Pages 387–402 in Damiani, C.C. and D.K. Garcelon (eds.). 2009. Proceedings of 387 the 7th California Islands Symposium. Institute for Wildlife Studies, Arcata, CA. BIOMETRIC AND DISEASE SURVEILLANCE OF AN INSULAR POPULATION OF FERAL PIGS ON SANTA CRUZ ISLAND, CALIFORNIA

KAREN M. BLUMENSHINE,1 HAILU KINDE,2 AND SHARON PATTON3

1Wildlife Services Associates, 15 St. Ann Drive, Santa Barbara, CA 93109; [email protected] 2California Animal Health and Food Safety Laboratory, San Bernardino Branch, 105 Central Avenue, San Bernardino, CA 92408; School of Veterinary Medicine, University of California, Davis, CA 95616 3University of Tennessee College of Veterinary Medicine, Department of Comparative Medicine, 2407 River Drive, Knoxville, TN 37996-4543

Abstract—Feral pigs (Sus scrofa) can harbor parasites and other infectious agents that may potentiate sylvatic transmission to native wildlife such as the federally protected Urocyon littoralis santacruzae (Santa Cruz island fox) and Spilogale gracilis amphiala (island spotted skunk). When the wild boar population on Santa Cruz Island (SCI) was scheduled for eradication, an effort was made to gather reference data on a potential reservoir of parasites and pathogens for future epidemiology and management, should health issues arise among native biota. Blood samples (256) were collected and necropsies (77) were performed to document the health, age, disease exposure, and biometric characteristics of the feral pig population. Samples were conveniently collected during five field visits between July 3 and November 22, 2005 from representative sections of the island. Serum samples were tested for antibodies to Brucella spp., pseudorabies virus, Trichinella spiralis, Toxoplasma gondii, and six serovars of Leptospira spp. Tests were negative (with 95% confidence of less than 2.2% prevalence), except for 32 (14%) individuals that had very low antibody titers (1:100–200) to one or more serovars of Leptospira. The existence of low antibody titers for Leptospira suggests exposure to this agent and perhaps some interaction between feral pigs and other land or sea mammals of the island. Necropsy examination of 77 carcasses was unremarkable. Histologically, mild non-specific background lesions were noted in various organs, interstitial pneumonia being the most commonly seen (38%). No parasites were detected at necropsy from stomach and small or large intestines. Fecal samples from 68 animals examined for parasites/parasite parts detected Eimeria sp. oocysts (coccidia, 2.9%), Demodex sp. (mite, 2%), and Metastrongylus sp. (lungworm, 9%). External parasites that were detected included Pulex irritans (human flea), Ixodes pacificus (western black-legged tick), and Haematopinus suis (hog louse). Data suggests exposure of SCI pigs to several Leptospire serovars that are atypical in pigs. There is no evidence that wild pigs or the eradication efforts on SCI posed a conservation threat to the SCI fox or other SCI species.

INTRODUCTION eradicated non-native species such as the pig could have served as a reservoir for the pathogens. The The presence of parasites and infectious information presented here on the presence of diseases in Santa Cruz Island (SCI) feral pigs (Sus pathogens on the island and the behavior of these scrofa), which have potential sylvatic transmission pathogens would be useful in the case of possible to insular wildlife populations of conservation future emerging diseases in protected wildlife on interest such as SCI fox (Urocyon littoralis SCI. Additionally, human exposure to zoonotic santacruzae) or the island spotted skunk (Spilogale diseases of feral pigs, as well as sylvatic exposure, is gracilis amphiala), has yet to be described. During potentiated by hunting activities through exposure the decline of the endangered island fox on Santa to carrion (Neiland 1970; Zygmont et al. 1982; Catalina Island (SCaI), questions were raised as to Currier 1989; Weigel et al. 1996; Hutton et al. 2006; whether a particular disease may have been present Lloyd-Smith et al. 2007). The presence of one of on the island prior, and particularly if a previously- these diseases may influence management decisions 388 BLUMENSHINE ET AL. during eradication efforts. This project was and coma with meningioencephalitis (Quiroga et al. undertaken to document the health status of a subset 1995). of the feral pig population during the process of their Without the presence of cats (felidae) on the eradication. Some background history and potential island to shed infective oocysts, a sylvatic effects of sylvatic and zoonotic transmission of transmission cycle of T. gondii would depend diseases from of feral pigs are introduced herein. directly upon carnivorism of encysted meat or nerve tissue (Frenkel et al. 1970). The SCI fox has History apparently been living with exposure to T. gondii The initial introduction of the feral pig to SCI in without significant impact on the population. A 1852 was for commercial purposes. Within the year, serologic survey (Garcelon et al. 1992) showed a the enterprise was abandoned and the pigs went low antibody prevalence of T. gondii in SCI fox, and feral (More 1857). Hog cholera (Classical Swine recent work has shown persistence of the low Fever Virus) was purposely introduced on the island prevalence in SCI fox of T. gondii (Clifford et al. three times, once prior to 1944 and at two different 2006). Although not an apparent conservation threat times in the 1950s, in an attempt to control or to the SCI fox, T. gondii can infect all warm- eradicate the pigs with no success (Wheeler 1944; blooded animals, including pigs and foxes Corn 1987a). In 1987, serologic testing for hog (Jungersen et al. 2002), and infection in the fox can cholera was performed on 31 animals from the SCI be asymptomatic or can cause central nervous pig population and did not detect exposure (APHIS system or other pathology. Toxoplasma was found 1987). concurrently with distemper virus in the single fox Pigs have had multiple biological effects on the carcass recovered during the 1999 decline of the island ecosystem, such as competition with native SCaI fox (Timm et al. 2009). Recently T. gondii and species for food resources (Schuyler 1988), Sarcocystis neurona were recognized to cause reducing the regeneration of coast live oak (Quercus encephalitis in marine mammals (Dubey et al. agrifolia) and other woody-species (Peart et al. 2003). Without adjacent felidae to perpetuate T. 1994), and rooting impacts on two rare endemic gondii in the SCI ecosystem, carcasses of marine plants (Arabis hoffmannii and Thysanocarpus mammals that beach on SCI should be considered as conchuliferus) (Klinger 2003) and seven of the nine a potential source of exposure. Marine mammals listed plant species on SCI (EIS 2002). documented to have T. gondii infection include California sea lions (Zalophus californianus) Conservation Considerations (Dubey et al. 2003), harbor seals (Phoca vitulina) This serosurvey was generalized for diseases (Lambourn et al. 2001), and southern sea otters with sylvatic and zoonotic potential. The inferences (Enhydra lutris nereis) (Kreuder et al. 2003). It has for conservation are dependant upon the potential also been recovered from a dolphin fetus (Tursiops virulence of such diseases in naïve island natives aduncus) (Jardine and Dubey 2002) and has been and whether they are passed in carrion. Diseases isolated from carnivorous birds such as raptors passed in carrion vary in importance and include (Lindsay et al. 1993). pseudorabies virus (PRV) (Weigel et al. 1996), T. Although not a conservation threat, T. spiralis gondii (Frenkel et al. 1970), T. spiralis, B. abortus, can cause myositis, infect both sylvatic and and B. suis (Neiland 1970; Zygmont et al. 1982). domesticated animals, and be maintained by SCI fox have been observed feeding on feral pig carnivores such as foxes, skunks, and swine carrion; therefore, PRV could be a potentially (Murrell et al. 1987). Improper hunting practices serious threat to foxes, skunks, and carnivorous contribute to transmission and spread of this birds during eradication activities if the virus was infection among wildlife (Pozio 2000). Anaerobic present in the pig carcasses. PRV produces acute metabolism of the larvae in nurse cells allows their disease and high mortality in most non-porcine survival in extremely decomposed carcasses. secondary hosts (E. Hahn, personal communication Spread of Trichinella spiralis via ingestion of 2007). PRV has been shown experimentally to be infected musculature is low in swine and high in lethal in blue foxes (Alopex lagopus), producing an foxes (Smith 1985). acute illness progressing from anorexia, depression, BIOMETRIC AND DISEASE SURVEILLANCE OF SANTA CRUZ ISLAND FERAL PIGS 389

Although B. abortus and B. suis have been host (Bolin and Cassells 1992). Species and documented to cause infections in canines (Neiland epidemiological investigations involve 1970; Shin and Carmichael 1999), and B. canis is differentiating between maintenance-host known to cause abortion in canids, the effects of B. populations and accidental-host populations for the canis and B. suis on canids have not been reported to serovar in a particular ecosystem (Hathaway 1981). be a direct cause of death. (Neiland 1970). The Characteristics of infection with a particular serovar abortive effects of these strains on canids are in are often considerably different in different hosts; question (Woodroffe and Ginsberg 1997); consequently, leptospirosis is more likely to pose a therefore, these strains of Brucella are not conservation threat when it cross-infects to a new considered to be a major conservation threat to the species host, because it is often more virulent in the island fox. accidental host. For instance, domestic dogs are Leptospirosis is an acute febrile zoonosis considered maintenance hosts for L.i. serovar infecting a broad range of mammalian hosts and is Canicola, and incidental hosts for the other serovars re-emerging globally (Lloyd-Smith et al. 2007). It is (Moore et al. 2006). A common example of this generally accepted that the major mode of phenomenon of increased virulence in an incidental transmission of leptospirosis is by exposure to host is the (recent) resurgence of acute and chronic contaminated water or animal tissues. The various leptospirosis in domestic canines, most often caused serovars of L. interrogans differ widely in their host by L.i. serovars of Grippotyphosa or Pomona interactions (Lloyd-Smith et al. 2007). The (Brown et al. 2003). Some of the recent thinking on epizootic infections typical of Leptospira tend to be Leptospira epidemiology hypothesizes that an periodic (Gulland et al. 1996). These cycles may be accidental host may sometimes become a suggestive of either host susceptibility, climactic maintenance host through a process of an epidemic, change, and increase in population density of when the survivors of the infection sometimes co- reservoir hosts and/or “accidental” hosts (Gulland et adapt and “non-host-adapted” serovars may become al. 1996). A central tenant of the epidemiology of “host-adapted” (Gulland et al. 1996; Lloyd-Smith et leptospirosis is the distinction between maintenance al. 2007). Therefore, it may be important to know hosts and accidental hosts for a given serovar, or about the existence of reservoirs of leptospires, what equivalently, between host-adapted and non-host- the typical maintenance hosts and the actual adapted serovars (Lloyd-Smith et al. 2007). maintenance hosts may be, and how the organisms Classically, maintenance hosts develop a chronic, are behaving in an ecosystem where managers are largely asymptomatic infection in their kidneys, and seeking to protect and conserve threatened or may shed leptospires in their urine for months or endangered species. years, while accidental hosts experience acute In the relatively insular environment of SCI, the infections with symptoms ranging from malaise to possibilities of hosts are limited. There are only four multi-organ failure and death (Lloyd-Smith et al. indigenous land mammals on the island: deer mouse 2007). There is also a recognized co-adaptation on (Peromyscus maniculatus), western harvest mouse the part of Leptospira strains. Typically there are (Reithrodontomys megalotis), spotted skunk, and host-adapted and non-host-adapted strains of SCI fox (L. Laughrin, personal communication leptospires. Host-adapted strains cause mild 1991). Only very few cattle remain localized on the disease, abortion, a high percentage of seropositives island today, but in the past, cattle, sheep, and pigs in the host population, and are shed in the urine for were wide-ranging. The sheep (Schuyler 1988) and long periods (Heath and Johnson 1994; Gulland et nearly all the cattle were removed by the early al. 1996). Non-adapted strains cause sporadic 1990s. The pigs are now considered eradicated. severe disease in the host, low prevalence of Seals and sea lions, primarily Phoca vitulina (harbor seropositive hosts, and are usually only shed for seal) and Zalophus californianus (California sea short periods by host individuals (Gulland et al. lion), with occasional Mirounga angustirostris 1996). In addition, the behavior of Leptospira is (Northern elephant seal) and vagrants “haul out” on often geographically specific, so that within a SCI beaches. Carcasses of other marine mammals, geographic region, certain serovars are prevalent Enhydra lutris (California sea otter), Eschrichtius and become adapted to a particular maintenance robustus (California gray whale), and others may 390 BLUMENSHINE ET AL. occasionally wash up on SCI beaches. Eight species been known to infest deer mice, western harvest of bats (Brown 1980) should also be considered as a mice, wild turkey (Meleagris gallopavo; Lane et al. source of exposure of SCI natives to potential 2006), and the island fox) (Castro and Wright 2007) pathogens. and is an important vector of Borrelia burgdorferi, Because of the behavior of Leptospira the causative agent of Lyme disease. Lyme disease organisms, there are many literature citations of has been reported to cause multisystemic lesions in maintenance and incidental hosts that parallel SCI foxes in Hokkaido, Japan (Isogai et al. 1994). Since species. The pig has been considered a primary Lyme disease does not tend to be epizootic, it maintenance host for L.i. Pomona (Hathaway 1981). represents a low threat to conservation efforts. In North America striped skunks (Mephitis mephitis) are recognized as maintenance hosts for Zoonoses this serovar as well (McKeever et al. 1958; Feral swine carry several diseases that pose a Kingscote 1986). Leptospirosis due to L.i. Pomona, zoonotic threat to humans. Human exposure to has been reported in a small sample of red foxes in carcasses after a hunt can potentiate infections such Canada causing severe hemorrhagic disease. In this as brucellosis (from B. abortus and B. suis) (Currier study, the fox appeared to be functioning as an 1989) leptospirosis (Lloyd-Smith et al. 2007), amplifier (accidental) host but not as a maintenance toxoplasmosis, trichinosis, and sarcoptic mange host (Kingscote 1986). L.i. Pomona infection is (Hutton et al. 2006). Lyme disease may also be affecting the survival of California sea lions and is transmitted to humans via I. pacificus (Burgdorfer et thought to have important consequences on al. 1985). population dynamics of the species (Gulland et al. 1996). Although the pig is not considered a primary host for L.i. serovar Icterohaemorrhagiae, it was the MATERIALS AND METHODS most prevalent of eight serovars tested in wild swine in Texas (Corn et al. 1986). The rat is considered the To maximize sample yield, five field sample primary host for L.i. Icterohaemorrhagiae (Ward et periods were performed in conjunction with early al. 2004). Dogs are considered maintenance hosts trapping and aerial hunting operations between July for serovar Canicola (Moore et al. 2006). Skunks 3 and November 22, 2005. Seventy-seven field and rats are thought to serve as incidental hosts for necropsies were performed, and 256 blood samples L.i. Canicola (Roth et al. 1961; Ward et al. 2004) were conveniently collected during the eradication and it has been reported in bats (Matthias et al. 2005) process. As part of the eradication strategy, the and in other canids. Raccoons are considered to be a island was arbitrarily fenced into five zones based primary maintenance host to L.i. Grippotyphosa. primarily upon fencing convenience (Fig. 1). True Skunks have also been cited as showing evidence of random sampling was not possible due to logistical exposure to this serovar (Richardson and Gauthier constraints, but all pigs dispatched during the 2003). This was also the most common serovar seen sample periods were bled for serology. Since in foxes in Germany (Müller and Winkler 1994). porcine blood is prone to rapid hemolysis, rendering Although cattle are maintenance hosts for L. the samples unfit for some serologic analyses, we borgptersenii serovar Hardjo, pig, horse, and sheep made efforts to draw blood from carcasses in the are also known to carry the infection (Hathaway field within five minutes of dispatch. Global 1981). L.b. Hardjo has also been detected in bats in Positioning System (GPS) locations of the pigs were the Amazon (Matthias et al. 2005). The domestic recorded by the hunters and plotted in a random pig is considered the primary host for L.i. serovar subset, 241/256 (94%), of pigs sampled (Fig. 1). Bratislava (S. Hietala, personal communication This subset of sample locations represented a 2007). variety of habitats, including grassland (52%), Pulex irritans and Ixodes pacificus are thought coastal sage brush (17%), shrubland (13%), to be “host-sharing” with the SCI fox and spotted chaparral (6%), oak woodland (4%), fennel (4%), skunk (Crooks et al. 2001; Crooks et al. 2004). P. human land use (3%), and riparian (1%). Barren and irritans is a possible vector for wild canid disease forest habitats were not represented. Sage and such as plague (McGee et al. 2006). I. pacificus has chaparral habitats were particularly BIOMETRIC AND DISEASE SURVEILLANCE OF SANTA CRUZ ISLAND FERAL PIGS 391

Figure 1. Santa Cruz Island showing numbered hunting zones, and locations of where pig carcasses for sampling were collected. underrepresented in the study, and grasslands and mandibular lymph node, lung, spleen, liver, and scrublands were highly overrepresented, likely due brain were collected in separate sterile bags and to ease of targeting and trap setting in those areas. stored frozen. Additional tissues from animals Sampling was convenience-based, since field visits exhibiting gross lesions were collected when were coordinated with times of early trappings in indicated. The small intestine, spiral colon, and each region and most traps were set at sites with road caecum were examined for parasites and 5 g of access and where a higher density of pigs was contents from each were pooled and preserved in expected. Pigs from non-trap locations (10% of 10% formalin. A random subset of 54 of these pigs total) were also sampled during each field period. was examined for the presence of ectoparasites with The disparity between the age and sex of individuals an emphasis on a variety of organisms rather than sampled for serology, compared with a larger quantitative numbers. Parasites were collected, island-wide population subset, was 49% juveniles preserved in 10% formalin, and shipped to the (84/172), and 51% adults (88/172), versus 68% University of Tennessee for evaluation (SP). juveniles (519/761) and 32% adults (242/761) Formalin fixed tissues were shipped to 2 (χ 1=22.15, p<0.001); 40% sows (84/211) and California Animal Health and Food Safety 60% boars (127/211), versus 36% sows (1288/ Laboratory (CAHFS), San Bernardino Branch, for 2 3531) and 64% boars (2243/3531) (χ 1=0.81, histologic evaluation. Samples were processed by p=0.37). standard techniques, and tissues were sectioned at Age was estimated by visual examination of 4µm thick and stained with hematoxylin and eosin tooth eruption patterns and individuals were and examined microscopically (HK). In an assigned to one of five age classes according to the individual with diseased tissues, lesions were classification protocol of Matschke (1967): I (<1 described and then catalogued by organ affected, week to 6 weeks), II (7–19 weeks), III (20–51 i.e., hepatitis would count as one “lesion,” nephritis weeks), IV (12–21 months), and V (>21 months). as a separate lesion, and pneumonia as a third. Field necropsy examination was performed by Causative agents such as parasites were only cited if either a pathologist or a practicing veterinarian (HK, visualized, or if inferred by the pattern of pathologic KB) on 77 swine. Tissues of palatine tonsil, findings. Due to the incidence of pneumonia mandibular lymph node, lung, spleen, liver, brain, detected, a random subset of five individuals with heart, thymus, diaphragm, small intestine, spiral interstitial pneumonia was screened for porcine colon, caecum, and kidney were collected in 10% circovirus using immunoperoxidase (IPX) buffered formalin (pH 7.2) for histopathologic histochemistry technique (HK). evaluation. Paired tissues of palatine tonsil, 392 BLUMENSHINE ET AL.

Blood was drawn from the heart or chest cavity “federally reportable” disease because we could not with focus on obtaining samples within five minutes gain permission from U.S. Department of of dispatch. We evaluated 240 samples for Brucella Agriculture Animal and Plant Health Inspection and PRV and 223 for Leptospira antibodies at Service to test for these diseases. CAHFS. Antibody specific to PRV was evaluated Preserved external parasites and fecal samples using a commercially available latex agglutination were shipped to the UTCVM for evaluation. assay developed for domestic swine1 (Schoenbaum External parasites were examined microscopically et al. 1990). Buffered acidified plate agglutination for identification. A random subset of 69 fecal (BAPA) was used to screen for antibody to Brucella samples was collected from the 77 necropsies. Five spp. using B. abortus antigen supplied by the United grams of fecal material was taken from each of the States Department of Agriculture (USDA) National small intestine, large intestine, and caecum and then Veterinary Service Laboratory (NVSL) according combined into single specimens. Fecal samples to the procedure described in Uniform Methods and were concentrated using centrifugal sugar flotation Requirements (UM&R). The screening assay, (Sheather’s sugar solution specific gravity 1.275) though designed to detect B. abortus exposure, is and formalin-ethyl acetate sedimentation, and then known to be antigenically cross-reactive with examined microscopically (SP). Brucella suis (Nielsen et al. 1999); therefore Comparisons between sexes and juveniles and negative tests for B. abortus likely rules out B. suis adults were evaluated using Chi-Square for a 2X2 as well (S. Hietala, personal communication 2007). contingency table with a Yates correction for A standard microagglutination test (microAT) was continuity. We also report 95% confidence intervals used to screen for six Leptospira serovars, including (95% CI) for the true prevalence of all pathologies L. interrogans serovar Pomona, L.i. serovar within the population based on sample prevalence. Bratislava, L.b. serovar Hardjo, L.i. serovar Grippotyphosa, L.i. serovar Icterohemorragiae, and L.i. serovar Canicola. The microagglutination assay RESULTS was performed using serial twofold dilutions of serum starting at a 1:100 dilution (Cole et al. 1973). The sampling fraction of the total wild swine Reference antigen and serovar-specific control population of SCI tested for PRV and Brucella was antisera were supplied by the USDA NVSL. 5% (240/5048); for Toxoplasma and Trichinella it Positive serologic reactions were interpreted as was 5% (256/5048); and for the six serovars of evidence of exposure to disease rather than Leptospira it was 4% (223/5048). Eighty-five confirmation of active infection in the wild pig percent of all sera and 90% of the carcasses were sampled. from Zone III; whereas 15% of the sera and 10% of We analyzed 256 serum samples for the carcasses were from Zone V (Fig. 1). The sex Toxoplasma gondii antibodies by the modified ratio of the 211 sampled swine was 127/84 (boars/ agglutination test (MAT) using formalin fixed sows). Of these, the age class V adults had the tachyzoites as antigen (bioMerieux Laboratories, largest sex disparity (48/19). This sex ratio is Lyon, France) at the University of Tennessee, slightly more skewed than the larger island-wide College of Veterinary Medicine (UTCVM). Titers sample of age class V pigs (105/53) (S. Morrison, of 1:32 or greater were considered positive. Serum personal communication 2007). samples were analyzed for Trichinella spiralis No antibody titers were detected for Brucella, antibodies (SafePath Laboratories ELISA), using PRV, Toxoplasma or Trichinella. While it is not microwells coated with T. spiralis excretory- possible to calculate 95% confidence intervals for secretory antigen. Samples with absorbance of 0.3 these null results, the upper limit of the 95% optical density units or higher were considered confidence interval (assuming a single positive positive (SP). Serum was not analyzed for exposure result) suggests that these diseases have a true to the introduced CSF (hog cholera) or any other prevalence of <2.2% in this population. The overall apparent seroprevalence for 1. Viral Antigens, Meridian Life Sciences, Memphis, Leptospira (all serovars) was 14.3% (32/223) (95% TN (http://www.meridianlifescience.com). CI: 10.6%–18.8%), with 31% (10/32) showing titers BIOMETRIC AND DISEASE SURVEILLANCE OF SANTA CRUZ ISLAND FERAL PIGS 393

Table 1. Apparent seroprevalence of Leptospira spp. in feral pigs (Sus scrofa) sampled in 2005 from Santa Cruz Island, California. Leptospira serovar N >1:100 Seroprevalence (%) 95% CI Std. error

L.i. Canicola 223 3 1.3 0.4–3.4 8.1 L.i. Grippo 223 16 7.2 4.6–10.7 6.4

L.i. Hargjo 223 0 0 ND* - L.i. Ictero 223 15 6.7 4.2–10.2 6.5 L.i. Pomona 223 2 0.9 0.2–2.8 9.4 L.i. Bratislava 223 12 5.4 3.1–8.6 6.6 Total # tested** 223 32 14.4 10.6–18.8 6.8 >1:100 dilution titer denotes exposure to one or more Leptospira serovars. *ND – No antibody detected at 1:100. ** Some individuals were positive to one or more serovars

(microAT) 1:100 to one or more serovars of organs. Among the 63 aged individuals, there was 2 Leptospira (Table 1). These low-level titers were no significant difference (χ 1=2.19, p = 0.14) in considered to be indicative of past exposure rather numbers of juveniles (I–III) (83%, 15/18) (95% CI: than evidence of active infections. The 62.3%–95.3%) with pathology as compared to seroprevalence of exposure to Leptospira spp. adults (IV–V) (60%, 27/45) (95% CI: 46.7%– relative to sex was 14% (18/127) (95% CI: 9.3%– 72.3%). There was, however, a marginally 20.3%) boars and 16% (13/84) (95% CI: 9.4%– significant number of pigs with lesions in age class 23.5%) sows, with one positive sample from an V (19/34=56%) (95% CI: 9.9%–23.7%) compared animal of undetermined sex. With respect to age class, the seroprevalence of exposure to Leptospira Table 2. Histopathological findings for Santa Cruz Island feral was 17% (14/84) (95% CI: 10.4%–24.8%) juveniles pigs (Sus scrofa) in 2005 from Santa Cruz Island, California. (age class I–III) and 16% (14/88) (95% CI: 9.9%– Histopathology Number of 23.7%) adults (age class IV and V). Samples were findings (N=77) findings Incidence positive from four pigs of undetermined age. There was no significant difference in prevalence of Interstitial pneumonia 29 38% Leptospira between boars and sows, or between Pulmonary hemorrhage 2 3% juveniles and adults (χ2 <0.01, p>0.99 for both 1 Interstitial nephritis 1 1% comparisons). Gross examination was performed on 77 Hepatitis 1 1% carcasses consisting of 65% (50/77) boars, 32% (25/ Myositis 4 5% 77) sows, and 3% (2/77) undetermined sex. No gross lesions indicative of population-level disease Sarcocyst 7 9% were noted in any of the animals examined. Sixty- Eosinophilic enteritis* 4 5% two percent (48/77) (95% CI: 52.4%–71.6%) of the Tonsilitis 18 23% pigs had mild, non-specific microscopic lesions in one or more organs (Table 2). Interstitial pneumonia Cervical lymphadenopathy 5 7% characterized by mild multifocal lymphocytic Chronic abscess 3 1% infiltrates was seen in 38% (29/77) of the necropsied Total # pigs with lesion 48† 62% animals. The distribution of combined lesions among the different groups was 76% (19/25) in * Possibly due to parasitic migration. sows and 58% (29/50) in boars. The 77 pigs showed † Individuals may have > 1 pathological findings. various non-specific incidental lesions in different 394 BLUMENSHINE ET AL.

2 to juveniles (χ 1=2.80, p=0.094). Thirty-eight open areas along roads and in the long central valley percent (29/77) (95% CI: 28.4%–47.6%) of the that courses longitudinally through the island. Trap- animals had no remarkable lesions in any of the wary pigs would be less likely to be represented. It tissues examined. Although pathologic changes may be assumed that the subset of pigs along roads were seen in the liver of one pig and interstitial would be more likely to interact, due to more nephritis of the kidney of another, none of the pigs convenient travel access, as opposed to some with positive titers for Leptospira showed smaller subpopulations that may have been more pathology in the commonly affected organs. isolated by geographic barriers. This would likely Overall, there were no remarkable lesions noted in bias the data to reflect a higher incidence of disease the swine population to suggest an active than the total population prevalence. population-disease process. Contrary to the age ratio observed in the island- Fecal sample concentration yielded: eggs of wide survey, significantly fewer juveniles than Metastrongylus spp. (lungworm) in 9% (6/69) (95% adults were represented in this study (p 0.001). The CI: 3.9%–16.4%); Demodex sp. (“mange” mite) in reason for this discrepancy was undetermined. one fecal sample (95% CI 0.1%–7.7%); Eimeria sp. Nevertheless, adults, having lived longer than oocysts 3% (2/69) (95% CI: 1.2%–10.9%) and grain juveniles, could have greater opportunities for mites or their eggs in 17% (12/69) (95% CI: 10.4%– exposure to diseases endemic to the island. The 26.6%) of the samples. A few of the samples selection of older individuals, with the expected contained unidentified coccidian oocysts that were increased probability of disease exposure over time, not compatible with Eimeria or Isospora species and those with external lesions or in poor condition, typical of swine. Twenty percent (14/69) (95% CI: could potentially bias the necropsy results toward a 12.7%–29.9%) contained grain mites or parasite higher incidence of pathology. However, the data eggs that were considered to be non-specific to show a marginally greater number of pigs with swine. External parasites identified on pigs lesions in juveniles than in adults (age class V). This examined included Haematopinus suis (hog louse) may be due to some acquired-immunity effect in 80% (43/54) (95% CI: 68.5%–88.1%); Pulex adults, which may protect surviving individuals irritans 13% (7/54) (95% CI: 6.2%–23.0%); and (Lankester 2001, 239; Fallon et al. 2003). Although Ixodes pacificus 6% (3/54) (95% CI: 1.5%–13.7%). a 30% rate of interstitial pneumonia in the H. suis was detected commonly during all visits, P. population may appear high, it was comparable to irritans was seen once in July and the remainder in pig farms where a moderate prevalence is October and November, and I. pacificus was found considered to be in the range of 30%–70% (Pointon in October and November only. et al. 1984; Radostits et al. 2000). In our opinion, the gross and histologic pathology findings in this pig population represented mild, incidental, non- DISCUSSION specific background lesions without evidence of an active population-disease process. In spite of the background pathology present Because of the hemolytic nature of porcine and evidence of exposure to several serovars of blood there was hemoglobin contamination in some Leptospira, data suggest that the subset of SCI wild serum samples. Some of the laboratory analyses, pigs examined was from a generally healthy particularly the Leptospira titers, were more population with no detectable ongoing population- sensitive to hemoglobin contamination. The disease processes. However, since several serovars respective laboratories discarded contaminated of Leptospira were unexpectedly found in an samples as invalid for each method; hence, the atypical host, it raises questions as to the potential of discrepancy in sample size between the different cross-infection to an island native as a naïve serologic tests. The serologic assays used in this accidental host. study were developed for use in domestic species and are not data to reference diagnostic sensitivity Methodology and Data Biases and specificity for feral pigs. With most serological The serum sampling had a convenience-based testing performed on wildlife species there is a bias, as the majority of traps were set primarily in general assumption that individual assays will BIOMETRIC AND DISEASE SURVEILLANCE OF SANTA CRUZ ISLAND FERAL PIGS 395 detect antibodies with similar performance as was the fact that the subset was a purposely biased documented for domestic species (Hietala and selection of an older, and therefore more likely Gardner 1999). These are considered screening exposed, population sample. assays with high detection sensitivity, but include the possibility of false positive results due to Implications antigenic cross-reactivity with other organisms Our objective was to document whether there sharing similar surface antigens. The BAPA test for were diseases in SCI pigs that would have zoonotic Brucella is the standard used for herd screening in implications or be of conservation interest to native domestic swine since it has up to 100% sensitivity fauna on or around SCI, including marine mammals (Barton 1996; Olsen et al. 1996), although a wide and the SCI fox. range of specificity values are reported. Since all Sarcocystis found in heart and skeletal muscles pigs tested negative for Brucella, the specificity of of pigs are incidental findings and are of no clinical this test is inconsequential. The pseudorabies assay relevance. The grain mites and the unidentified specificity is approximately 95%, also as measured coccidian oocysts, that were non-specific to swine for domestic swine. In the microAT test for and were detected in fecal samples, were Leptospira, as in other agglutination assays, presumably ingested from an exogenous source. serologic cross-reaction is known to occur, and Since grain mites and their eggs were fairly extremely elevated titers are more likely to show abundant, it is likely they were consumed with the cross-reaction to related surface antigens. The tested corn that was used for baiting the pig traps. The serotypes do have some shared surface antigens, so unidentified coccidian oocysts were likely passed cross-reactivity is expected between L.i. Bratislava from ingested prey. The Pulex irritans and I. and L.i. Pomona, as well as a lower level cross- pacificus found on the pigs may also have been reactivity between L.i. Icterohemmorhagiae and L.i. “host-sharing” with the SCI fox and spotted skunk Pomona. For example, a high antibody titer of L.i. (Crooks et al. 2001; Crooks et al. 2004). The lone Bratislava of >1:3200 can cause a low reaction Demodex sp. mite recovered in a fecal sample is the (such as 1:100) in L.i. Pomona, or a >1:3200. L.i. first documented on SCI. This finding should be Pomona can pull up an L.i. Bratislava to 1:100. The considered in the differential diagnosis of chronic highest serologic response generally indicates the skin lesions in the captive island foxes, should they serovar to which it is exposed, and the higher the reoccur. titer in one serovar the more likely it is to cross-react There was no significant difference between and artificially raise the titer in the other serovar. juveniles and adults in the prevalence of detectable The titers for Leptospira measured in this study did antibody titers for any of the diseases. For PRV, this not exceed 1:200. This decreases the chances of is in contrast to prevalence findings in studies of cross-reaction (S. Hietala, personal communication pigs on SCaI (Timm et al. 2005), in Georgia (Pirtle 2007). There are no published evaluations of et al. 1989), and in Florida (Van der Leek et al. Leptospira serology performance for swine. In 1993), where the probability of exposure appeared assessments of MAT for other species, however, the to increase with age. It had been hypothesized this sensitivity was low (30%) in early acute-phase cases disparity was due to maternal-sibling grouping of and increased to 76% in convalescence, while young pigs, thereby reducing exposure. However, specificity was less than or equal to 97% recent work by Romero et al. (2001) has shown that (Cumberland et al. 1999). Therefore, while the transmission of the PRV strain indigenous to feral prevalence of Leptospira may be underestimated by pigs is preferentially by venereal route, suggesting this technique, the probability of false positives is that exposure is primarily in adults. low. Transmission of Leptospira is primarily from In those necropsies done by a practicing urine and contaminated water sources (Gummow et veterinarian, rather than the pathologist, subtle al. 1999). After weaning, exposure would be similar lesions may have been overlooked, thereby in all sex and age groups using a water source, underestimating prevalence of pathologic changes. regardless of the size of their home range. There was The lack of population disease seen on gross and no significant difference in titers between sexes for microscopic examination is noteworthy in light of 396 BLUMENSHINE ET AL. any of the diseases tested, which agrees with the Unlike SCaI, where Trichinella were found in findings of the above authors for PRV. muscle of pigs (Timm et al. 2005), no evidence of The most important finding of this study Trichinella was found in the SCI pig population relative to SCI fox conservation was the lack of either by serology, gross examination of muscle evidence of exposure of SCI pigs to PRV during the tissue, or by microscopic examination of diaphragm feral pig eradication. This is in contrast with the tissue for nurse cells. It is doubtful the SCI pig PRV seroprevalence of 25% in the SCaI pig population was a reservoir for infection on the population (Timm et al. 2005). PRV infection is island. There have been suggestions, however, of acute and has a high mortality in experimentally potential low level cannibalism in foxes in Italy infected foxes (Quiroga et al. 1995) and in most (Rémonti et al. 2005) which could perpetuate non-porcine secondary hosts in the wild (Thawley transmission of Trichinella infection within a fox and Wright 1982; Weigel et al. 1996; E. Hahn, population without an intermediate host. Regardless personal communication 2007). Although there is of this potential, Trichinella infection within a fox no evidence implicating PRV in the fox population population would not represent a conservation decline on SCaI, finding PRV antibodies in the SCaI threat. pig population and having a concurrent decline in The spectrum of titers for different serovars of fox or other wildlife populations during the pig Leptospira is interesting in light of the variety and eradication (Timm et al. 2000), where infected pig history of mammalian inhabitants on SCI over the carcasses are available for scavenging, raises last 20 years. The current four indigenous land interesting questions regarding potential exposure mammals, the past four ranching mammals of wildlife. Further data, such as testing of fox (including dogs), and marine mammals which tissues for evidence of exposure to PRV, would be “haul-out” or wash up as carcasses on the beaches, needed to address these questions. Since these as well as the eight recorded bat species (Brown coincident circumstances did not exist on SCI, 1980) need to be considered in the epidemiology of decline of the SCI fox population due to PRV Leptospira. The expected prevalence of Leptospira exposure is very unlikely. in a wild swine population is estimated at 5% (E. The lack of evidence of Brucella infection Bush, personal communication 2008). This data supports the results of previous testing of 61 suggests that SCI wild swine were exposed to a individuals in the SCI swine population (Corn number of serovars of Leptospira. 1987b) that were also negative (Corn 1987c). This is L. i. Grippotyphosa represents the highest titers significant to the hunters participating in the of any serovar tested (7%), although there have been eradication efforts to have low risk of zoonotic no reports of raccoons on SCI. This serovar has been transmission of brucellosis. shown experimentally to pass to wild carnivores Although there are no cats on SCI, the finding when fed infected rodents (Reilly 1970), however, by Garcelon et al.(1992) of low-level recent work has revealed no evidence of antibodies seroprevalence for Toxoplasma gondii in SCI foxes to this serovar in the SCI fox (Clifford et al. 2006). may not necessarily be false positive laboratory Although they are the primary host of L.i. results, as hypothesized, since the findings were Icterohaemorrhagiae, there have been no confirmed repeated in the recent study (Clifford et al. 2006). sightings of rats on SCI. Incidental hosts include However, data suggest that it is unlikely that mice, skunk, fox, and bat (Clark et al. 1961; Ward et transmission to foxes by eating wild pig carrion was al. 2004; Matthias et al. 2005). Our 6% prevalence a contributing factor. T. gondii infection could be rate is not unexpected in light of the fact that sustained in the population by SCI foxes scavenging Garcelon et al. (1992) reported a prevalence of 14% carcasses of marine mammals or eating fresh meat in the SCI foxes. SCI was the only one of six of birds. It is interesting to note that the single fox Channel Islands with foxes to have any evidence of carcass recovered during the rapid decline of SCaI Leptospira exposure for the two serovars tested in foxes had evidence of infection of T. gondii and the that study. No antibody titer to L.i. importance of the co-infection is unknown (L. Icterohaemorrhagiae was detected in the SCI fox Munson, personal communication 2007). survey in 2001–2003 (Clifford et al. 2006) or SCI spotted skunks in 2000–2001 (Bakker et al. 2006). It BIOMETRIC AND DISEASE SURVEILLANCE OF SANTA CRUZ ISLAND FERAL PIGS 397 is interesting that by the 2001–2003 survey of the were not a primary source of L.i. Pomona to sea SCI fox, there was no evidence of this serovar in the lions. sample tested. Although data indicate exposure of the SCI pigs Leptospira i. Bratislava displayed a 5% to several serovars of Leptospira, there has been no antibody response in the study population and is report of pathology attributed to Leptospirosis from reportedly indigenous in feral pigs (Corn et al. the necropsies done on the SCI fox population to 1986). Serologic studies in the United States and date (L. Munson, personal communication 2008). Canada indicate that Bratislava has become the The overall conservation threat to the SCI fox from serovar that most frequently affects swine (Bolin Leptospirosis appears to be low at this time. and Cassells 1992). It is noteworthy that 7% (2/28) Because of the behavior of Leptospira organisms, of the wild SCI fox population showed evidence of the ecology of Leptospira in island natives bears exposure to this serovar (Clifford et al. 2006), but monitoring of a variety of serovars, particularly in a the captive-born SCI fox showed no evidence of threatened or endangered population. exposure. This finding suggests that there was exposure of fox in the wild from the pigs or other mammals. The SCI spotted skunk has not been CONCLUSIONS AND tested for this serovar. This serovar has been RECOMMENDATIONS reported in rodents and dogs and it is considered they could serve as carriers; however, Moore et al. Although there were parasites and background (2006) cite dogs as an incidental host for this pathology present and there was evidence of serovar. exposure to several serovars of Leptospira in this Leptospira i. Canicola only produced a positive sample of SCI wild pigs, this was generally a antibody response in 1% of the study population. healthy sub-population with no detectable ongoing The presence of L.i. Canicola exposure is interesting population-disease processes. There is no evidence since the dog is considered to be the primary that the wild pigs or the eradication efforts on SCI reservoir host (Ward et al. 2004; S. Hietala, personal posed a zoonotic threat to hunters nor a conservation communication 2007). Over the past 20 years, with threat to the SCI fox or other island species. These the exception of pig-hunting dogs, dogs have been studies underscore the importance of pathogen typically limited to the main ranch area and/or screening on a species prior to eradication to incidental illegal entry to the shore for short periods preserve data and to aid preventative management from oceancraft. No antibodies to L.i. Canicola were of sylvatic and zoonotic transmission during the reported in the 29 SCI foxes tested by Garcelon et al. efforts. (1992), nor by Clifford in 2001–2003, nor in 28 SCI These studies and findings supplement other spotted skunks tested in 2000–2001 (Bakker et al. works showing the complexity of interactions 2006). between different serovar of Leptospira with Leptospira i. Pomona titer levels were also primary and alternative hosts. It is not likely that relatively low (1%) in the study population. L.i. Leptospirosis will become a major conservation Pomona has been shown to have a markedly threat on SCI; however any serovar now pathogenic effect on California sea lions (Zalophus documented on the island could potentially become californianus) and appears to be responsible for virulent if the un-adapted serovar infected a new periodic die-offs along the mainland. There has host species. With an endangered insular native been suggestion that a source of contamination may mammal population on SCI, more effort devoted to be small mammals or pigs living on the Channel land and sea mammal serologic surveillance may be Islands (Gulland et al. 1996). No evidence of desired to address potential reservoirs, particularly exposure to this serovar was found during testing of for Leptospira and T. gondii, in order to anticipate 28 SCI spotted skunks in 2000–2001 (Bakker et al. potential sylvatic interactions in the island 2006) and 28 SCI foxes in 2001–2003 (Clifford et ecosystem. al. 2006). These data from SCI pigs suggest that pigs 398 BLUMENSHINE ET AL.

ACKNOWLEDGMENTS Bolin, C.A., and J.A. Cassells. 1992. Isolation of Leptospira interrogans serovars Bratislava and For assistance in this study, many thanks to: Hardjo from swine at slaughter. Journal of Lotus Vermeer, Scott Morrison, and The Nature Veterinary Diagnostic Investigation 4:89–93. Conservancy for their support and sponsorship, Brown, C., W. Roberts, S. Sanchez, D. Drum, and making this study possible; Sue Benech for C. Greene. 2003. Clinical syndromes technical assistance, field assistance, and draft associated with Leptospirosis in dogs. 28th review; Sharon Hietala for sharing her expertise; World Congress of the World Small Animal Eric Bush and the National Center for Disease Veterinary Association Proceedings, Bangkok, Surveillance, USDA, APHIS, and Brian Hudgens of Thailand. Available at http://www.vin.com/ the Institute for Wildlife Studies, for their proceedings/ contribution in epidemiology and statistics; Lyndall Proceedings.plx?CID=WSAVA2003&O=Gen Laughrin and the University of California SCI Field eric. Station for technical and field assistance; Brian Brown, P.E. 1980. Distribution of bats of the Green, Cyril Harnisch, Kathy Foerner, Nora Morse, California Channel Islands. Pages 751–756. In: and Ron Gutier for field assistance; and Sabrina Power, D.M. (ed.), The California Islands: Martyn, Dacy Lim, Laura Fairbanks, and Kim Proceedings of a Multidisciplinary Peden for data entry and report generation. Special Symposium. Santa Barbara Museum of thanks to Prohunt for the “make it work” efforts in Natural History, Santa Barbara, CA. all field situations. Burgdorfer, W., R.S. Lane, A.G. Barbour, R.A. Gresbrink, and J.R. Anderson. 1985. The western black-legged tick, Ixodes pacificus: a REFERENCES vector of Borrelia Burgdorferi. American Journal of Tropical Medicine and Hygiene Acevedo-Whitehouse, K., H. de la Cueva, F.M. 34:925–930. Gulland, D. Aurioles-Gamboa, F. Arellano- Castro, M.B., and S.A. Wright. 2007. Vertebrate Carbajal, and F. Suarez-Guemes. 2003. hosts of Ixodes pacificus (Acari: Ixodidae) in Evidence of Leptospira interrogans infection California. Journal of Vector Ecology 32:140– in California sea lion pups from the Gulf of 1 4 9 . California. Journal of Wildlife Diseases Clark, LG, J.I. Kresse, R.R. Marshak, and C.J. 39:145–151. Hollister. 1961. Natural Occurrence of Animal and Plant Health Inspection Service Leptospira icterohaemorrhagiae in the Eastern (APHIS). 1988. APHIS/SCWDS Hog Cholera grey fox and the Eastern raccoon. Nature Surveillance on the Islands of Santa Cruz and 192:1312–1313. Santa Rosa, California (February 1–February Clifford, D.L, J.K. Mazet, E. Dubovi, D. Garcelon, 13, 1987). USDA, APHIS, Washington, DC. T. Coonan, P. Conrad, and L. Munson. 2006. Unpublished report on file, Channel Islands Pathogen exposure in endangered island fox National Park. (Urocyon littoralis) populations: implications Bakker, V.J, D.H. Van Vuren, K. Crooks, C. Scott, for conservation management. Biological J. Wilcox, and D. Garcelon. 2006. Serologic Conservation 131:230–243. survey of the island spotted skunk on Santa Cole, J.R., C.R. Sulzer, and A.R. Pursell. 1973. Cruz Island. Western North American Improved micro-technique for the leptospira Naturalist 66:456–461. microscopic agglutination test. Applied Barton, C. 1996. The Rapid Automated Microbiology 25:976–980. Presumptive (RAP) Test. Livestock Corn, J.L. 1987a. Feb. 27. Letter to Dr. Carey Conservation Institute Annual Meeting. Stanton. Southeastern Cooperative Wildlife Colorado Springs, CO. 3–4. Disease Study. University of Georgia, College Bolin, C.A. 1994. Diagnosis of Leptospirosis in of Veterinary Medicine. Dept. of Parasitology. swine. Swine Health and Production 2: 23–24. Athens, GA. BIOMETRIC AND DISEASE SURVEILLANCE OF SANTA CRUZ ISLAND FERAL PIGS 399

Corn, J.L. 1987b. June 5. Letter to Dr. D.A. Jessup, Fallon, P.G., J. Gibbons, R.A. Vervenne, E.J. Southeastern Cooperative Wildlife Disease Richardson, A.J. Fulford, S. Kiarie, R.F. Study. University of Georgia, College of Sturrock, P.S. Coulson, A.M. Deelder, J.A. Veterinary Medicine. Dept. of Parasitology. Langermans, A.W. Thomas, and D.W. Dunne. Athens, GA. 2003. Juvenile rhesus monkeys have lower Corn, J.L. 1987c. July 9. Letter to Dr. Carey type 2 cytokine responses than adults Stanton. Southeastern Cooperative Wildlife following primary infection with Schistosoma Disease Study. University of Georgia, College mansoni. Abstract. Journal of Infectious of Veterinary Medicine. Dept. of Parasitology. Diseases 187:939–945. Athens, GA. Frenkel, J.K., J.P. Dubey, and N.L. Miller. 1970. Corn, J.L., P.K. Swiderek, B.O. Blackburn, G.A. Toxoplasma gondii in cats: Fecal stages Erickson, A.B. Thiermann, and V.F. Nettles. identified as coccidian oocysts. Science 1986. Survey of selected diseases in wild 167:893 –896. swine in Texas. Journal of the American Garcelon, D.K., R.K. Wayne, and B.J. Gonzales. Veterinary Medical Association 189:1029– 1992. A serologic survey of the island fox 1032. (Urocyon littoralis) on the Channel Islands, Crooks, K.R., D.K. Garcelon, C. Scott, J. Depue, J. California. Journal of Wildlife Diseases Wilcox, R. Kimsey, and D. Van Vuren. 2004. 28:223–229. Ectoparasites of a threatened insular endemic Gulland, F.M., M. Koski, L.J. Lowenstine, A. mammalian carnivore: The island spotted Colagross, L. Morgan and T. Spraker. 1996. skunk. The American Midland Naturalist Leptospirosis in California sea lions (Zalophus 151:35–41. californianus) stranded along the central Crooks, K.R., C.A. Scott, L. Angeloni, L. Bowen, California coast, 1981–1994. Journal of R.B. Kimsey, and D.H. Van Vuren. 2001. Wildlife Diseases 32:572–580. Ectoparasites of the island fox of Santa Cruz Gummow, B., J.H. Myburgh, P.N. Thompson, J.J. Island. Journal of Wildlife Diseases 37:189– Van der Lugt, and B.T. Spencer. 1999. Three 193. case studies involving Leptospira interrogans Cumberland, P, C.O. Everard, and P.N. Levett. serovar pomona infection in mixing farm units. 1999. Assessment of the efficacy of an IgM- Abstract. Journal of the South African elisa and microscopic agglutination test (MAT) Veterinary Association 70:29–34. in the diagnosis of acute Leptospirosis. Hathaway, S.C. 1981. Leptospirosis in New American Journal of Tropical Medicine and Zealand: an ecological view. Abstract. New Hygiene 61:731–734. Zealand Veterinary Journal 29:109–112. Currier, R.W. 1989. Brucellosis. Zoonosis Heath, S.E., and R. Johnson. 1994. Leptospirosis. Updates. Journal of the American Veterinary Journal of the American Veterinary Medical Medical Association 195:595–597. Association 205:1518–1523. Dubey, J.P., R. Zarnke, N.J. Thomas, S.K. Wong, Hietala, S.K., and I.A. Gardner. 1999. Validity of W. Van Bonn, M. Briggs, J.W. Davis, R. using diagnostic tests that are approved for use Ewing, M. Mense, O.C.H. Kwok, S. Romand, in domestic animals for non-domestic species. and P. Thulliez. 2003. Toxoplasma gondii, Pages 55–58. In: Fowler, M.E., and R.E. Miller Neospara caninum, Sarcosytis neurona, and (eds.), Zoo and Wild Animal Medicine. 4th Sarcosytis canis-like infections in marine edition. WB Saunders, Philadelphia, PA. mammals. Veterinary Parasitology 116: 275– Hutton, T, T. DeLiberto, S. Owen, and B. 296. Morrison. 2006. Disease Risks Associated with Environmental Impact Statement. 2002. Santa Increasing Feral Swine Numbers and Cruz Island Primary Restoration Plan, Final Distribution in the United States. Midwest Environmental Impact Statement Appendix. Association of Fish and Wildlife Agencies. National Park Service, US Department of the Wildlife and Fish Health Committee, July 11. Interior. June 205-213. Isogai, E, H. Isogai, H. Kawabata, T. Masuzawa, Y. Yanagihara, K. Kimura, T. Sakai, Y. 400 BLUMENSHINE ET AL.

Azuma, N. Fujii, and S. Ohno. 1994. Lyme Lloyd-Smith, J.O., D.J. Greig, S. Hietala, G. disease spirochetes in a wild fox (Vulpes Ghneim, L. Palmer, J. St Leger, B.T. Grenfell, vulpes schrencki) and in ticks. The Journal of and F.M.D. Gulland. 2007. Cyclical changes in Wildlife Diseases 30:439–444. seroprevalence of Leptospirosis in California Jardine, J.E., and J.P. Dubey. 2002. Congenital sea lions: endemic and epidemic disease in one toxoplasmosis in an Indo-Pacific Bottlenose host species? BMC Infectious Diseases 7:125. Dolphin (Tursiops aduncus). Journal of Avail from http://www.biomedcentral.com/ Parasitology 88:197–199. 1471-2334/7/125. Jungersen, G., L. Jensen, M.R. Rask, and P. Lind. Matschke, G.H. 1967. Aging European wild hogs 2002. Non-lethal infection parameters in mice by dentition. Journal of Wildlife Management separate sheep Type II Toxoplasma gondii 31:109 –113. isolates by virulence. Comparative Matthias, M.A., M. Díaz, K.J. Campos, M. Immunology, Microbiology and Infectious Calderon, M.R. Willig, V. Pacheco, E. Diseases 25:187–195. Gotuzzo, R.H. Gilman, and J.M. Vinetz. 2005. Kingscote, B.F. 1986. Leptospirosis in red foxes in Diversity of bat-associated Leptospira in the Ontario. Abstract. Journal of Wildlife Diseases Peruvian Amazon inferred by Bayesian 22:475–478. phylogenetic analysis of 16S ribosomal DNA Klinger, R.C. 2003. The Population Dynamics of sequences. American Journal of Tropical Feral Pigs and Their Effects on Vegetation Medicine and Hygiene 73:964–974. Communities and Rare Plants on Santa Cruz McGee, B., M.J. Butler, D.B. Pence, J.L. Island, California. 6th California Islands Alexander, J.B. Nissen, W.B. Ballard, and Symposium Abstracts, Dec. 1–3. K.L. Nicholson. 2006. Possible vector Kreuder, C., M. Miller, D. Jessup, L. Lowenstine, dissemination following a plague epizootic in M.D. Harris, J. Ames, T.E. Carpenter, P.A. black-tailed prairie dogs in northwestern Conrad, and J.K. Mazet. 2003. Patterns of Texas. Abstract. Journal of Wildlife Diseases mortality in the southern sea otter (Enhydra 42:415–420. lutris) from 1998–2001. Journal of Wildlife McKeever, S, G.W. Gorman, J.F. Chapman, M.M. Diseases 39:495–509. Galton, and D.K. Powers. 1958. Incidence of Lambourn, D.M., S.J. Jeffries, and J.P. Dubey. leptospirosis in wild mammals from 2001. Seroprevalence of Toxoplasma gondii in southwestern Georgia, with a report of new harbor seals (Phoca vitulina) in southern Puget hosts for six serotypes of leptospires. Abstract. Sound, Washington. Abstract. Journal of American Journal of Tropical Medicine and Parasitology. 87:1196. Hygiene 7(6):646–655. Lane, R.S., T.F. Kucera, R.H. Barrett, J. Mun, C. Moore, G.E., L.F. Guptill, N.W. Glickman, R.J. Wu, and V.S Smith. 2006. Wild turkey Caldanaro, D. Aucoin, and L.T. Glickman. (Meleagris Gallopava) as a host of Ixodid 2006. Canine Leptospirosis, United States, ticks, lice, and Lyme disease spirochetes 2002–2004. Emerging Infectious Diseases (Borrelia burgdorferi Sensu Lato) in Journal, Center for Disease Control March California State Parks. Journal of Wildlife 12(3). Available from http://www.cdc.gov/ Diseases 42:759–771. ncidod/EID/vol12no03/05-0809.htm. Lankester, M.W. 2001. Extrapulmonary More, T.W. 1857 Affidavit, County of Santa lungworms of cervids. Pages 228–278. In: Barbara, District Court 2nd Judicial District, Samuel, W.M., A.A Kocan, and M.J. Pybus Judicial Proceedings, Thomas Wallace More (eds.), Parasitic Diseases of Wild vs. M.J. Box. June 2. Mammals..Iowa State University Press, Ames, Müller, H, and P. Winkler. 1994. Results of IA. serological studies of Leptospira antibodies in Lindsay, D.S., P.C. Smith, F.J. Hoerr, and B.L. foxes. Abstract. Berliner und Münchener Blagburn. 1993. Prevalence of encysted tierärztliche Wochenschrift 107:90–93. Toxoplasma gondii in raptors from Alabama. Journal of Parasitology 79: 870–873. BIOMETRIC AND DISEASE SURVEILLANCE OF SANTA CRUZ ISLAND FERAL PIGS 401

Munson, L., and W. Vickers. 2008. Update on Fox Trichinella. Veterinary Parasitology 93:241– Health. Summary Report, Island Working 262. Group Annual Meeting. Quiroga, M.I., S. Vasquéz, M. Lopez-Peña, F. Murrell, K.D., F. Stringfellow, J.B. Dame, D.A. Guerrero, and J.M. Nieto. 1995. Experimental Leiby, C. Duffy, and G.A. Schad. 1987. Aujeszky’s disease in blue foxes (Alopex Trichinella spiralis in an agricultural lagopus). Zentralblatt für Veterinärmedizin. ecosystem. II. Evidence for natural Reihe A 42:649–657. transmission of Trichinella spiralis spiralis Radostits, O.M., J.H. Arundel, C.C. Gay, D.C. from domestic swine to wildlife. Abstract. Blood, and K.W. Hinchcliff. 2000. Diseases International Journal for Parasitology. 73:103– caused by Mycoplasma SPP. Pages 1009– 109. 1010. In: Veterinary Medicine: A Textbook of Neiland, K.A. 1970. Rangiferine brucellosis in the Diseases of Cattle, Horses, Sheep, Pigs and Alaskan canids. Journal of Wildlife Diseases. Goats. W.B. Saunders Company, Philadelphia, 6: 136–139. PA. Nielsen, K., D. Gall, P. Smith, A. Vigliocco, B. Reilly, J.R. 1970. The susceptibility of five species Perez, L. Samartino, P. Nicoletti, A. Dajer, P. of wild animals to experimental infection with Elzer, and F. Enright. 1999. Validation of the Leptospira grippotyphosa. Journal of Wildlife fluorescence polarization assay as a serological Diseases 6:289–294. test for the presumptive diagnosis of porcine Rémonti, L, A. Balestrieri, L. Domenis, C. Banchi, brucellosis. Veterinary Microbiology 68:245– T. Lo Valvo, S. Robetto, and R. Orusa. 2005. 253. Red fox (Vulpes vulpes) cannibalistic behavior Olsen, S.C., D. Evans, S.G. Hennager, N.F. and the prevalence of Trichinella brivoti in Cheville, and M.G. Stevens. 1996. Serologic NW Italian Alps. National Reference Centre responses of Brucella abortus strain 19 for Wild Animal Diseases. Parasitology calfhood-vaccinated cattle following adult Research 97:431–435. vaccination with strain RB51. Journal of Richardson, D.J., and J.L. Gauthier. 2003. A Veterinary Diagnostic Investigation 8:451– serosurvey of Leptospirosis in Connecticut 454. peridomestic wildlife. Abstract. Vector-Borne Peart, D., D.T. Patten, and S.L. Lohr. 1994. Feral and Zoonotic Diseases 3:187–193. pig disturbance and woody species seedling doi:10.1089/153036603322662174. regeneration and abundance beneath coast live Romero, C.H., P.N. Meade, J.E. Shultz, H.Y. oaks (Quercus agrifolia) on Santa Cruz Island, Chung, E.P. Gibbs, E.C. Hahn, and G. Lollis. California. Pages 313-322. In: Halvorson, 2001. Venereal transmission of pseudorabies W.L., and G.J. Maender (eds.), The Fourth viruses indigenous to feral swine. Journal of California Islands Symposium: Update on the Wildlife Diseases 37:289–296. Status of Resources. Santa Barbara Museum of Roth, E.E., W.V. Adams, and D. Linder 1961. Natural History, Santa Barbara, CA. Isolation of Leptospira canicola from skunks Pirtle, E.C., J.M. Sacks, V.F. Nettles, and E.A. in Louisiana. Public Health Reports 76:335– Rollor III. 1989. Prevalence and transmission 340. of pseudorabies virus in an isolated population Schoenbaum, M.A., G.W. Beran, and D.P. of feral swine. Journal of Wildlife Diseases Murphy. 1990. A study comparing the 25:605–607. immunologic responses of swine to Pointon, A.M., P. Heap, and P. McCloud. 1984. pseudorabies viral antigens based on the Enzootic pneumonia of pigs in South ELISA, serum virus neutralization, and latex Australia—Factors relating to incidence of agglutination tests. Journal of Veterinary disease. Abstract. Journal of the Australian Diagnostic Investigation 2:29–34. Veterinary Association Ltd. 62:98–101. Schuyler, P. 1988. Feral Pigs (Sus scrofa) on Santa Pozio, E. 2000. Factors affecting the flow among Cruz Island: The Need for a Removal Program. domestic, synanthropic, and sylvatic cycles of The Nature Conservancy, Santa Barbara, CA. 402 BLUMENSHINE ET AL.

Unpublished report on file, Channel Islands Van der Leek, M.L., H.N. Becker, E.C. Pirtle, P. National Park. Humphrey, C.L. Adams, B.P. All, G.A. Shin, S., and L.E. Carmichael. 1999. Canine Erickson, R.C. Belden, W.B. Frankenberger, Brucellosis Caused by Brucella canis. and E.P.J. Gibbs. 1993. Prevalence of International Veterinary Information Service. pseudorabies (Aujeszky’s disease) virus Avail at: www.ivis.org. Document antibodies in feral swine in Florida. Abstract. A0101.1199. Journal of Wildlife Diseases 29:403–409. Smith, H.J. 1985. Infectivity of Canadian isolates Ward, M.P., L.F. Guptill, and C.C. Wu. 2004. of Trichinella spiralis nativa for swine, rats, Environmental risk factors for Leptospirosis in and carnivores. Canadian Journal of dogs. Journal of the American Veterinary Comparative Medicine 49:88–90. Medical Association 225:72–77. Thawley, D.G., and J.C. Wright. 1982. Weigel, R.M., E.C. Hahn,, and G. Scherba. 1996. Pseudorabies virus infection in raccoons: A An experimental evaluation of raccoons as a review. Journal of Wildlife Diseases 18:113– reservoir for transmission of genetically 116. engineered pseudorabies virus vaccine and Timm, S.F., L. Munson, B.A. Summers, K.A. wildtype-vaccine recombinants. Chapter 3. Terio, E.J. Dubovi, C.E. Rupprecht, S. Kapil, Proceedings of the International Symposium and D.K. Garcelon. 2009. A suspected canine on Environmental Release of Biotechnology distemper epidemic as the cause of a Products, Ottawa, Canada. catastrophic decline in Santa Catalina island Wheeler, S.A. 1944. California’s little known foxes (Urocyon littoralis catalinae). Journal of Channel Islands. United States Naval Institute Wildlife Diseases 45:333–343. Proceedings 70:257–270. Timm, S.F., J.S. Romsos, and D.K. Garcelon. Woodroffe, R., and J.R. Ginsberg. 1997. Chapter 4: 2005. Serological Survey for Pseudorabies Past and Future Causes of Wild Dogs’ Virus, Brucellosis and San Miguel Sea Lion Population Decline. African Wild Dog Status Virus in an Isolated Population of Wild Swine Survey and Action Plan. The IUCN/SSC Canid (Sus scrofa). Unpublished report. Institute for Specialist Group. Wildlife Studies, Arcata, CA. Zygmont, S.M., V.F. Nettles, E.B. Shotts, Jr., W.A. Timm, S.F., J.M. Stokely, T.B. Gehr, R.L. Peebles, Carmen, and B.O. Blackburn. 1982. and D.K. Garcelon. 2000. Investigation into Brucellosis in wild swine: A serologic and the Decline of Island Foxes on Santa Catalina bacteriologic survey in the southeastern United Island. Unpublished report prepared by the States and Hawaii. Journal of the American Institute for Wildlife Studies, Arcata, CA for Veterinary Medical Association 181:1285– the Ecological Restoration Department, Santa 1287. Catalina Island Conservancy, Avalon, CA.