Evidence of Natural Bluetongue Virus Infection Among African Carnivores Kathleen A

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11-1994 Evidence of Natural Bluetongue Virus Infection among African Carnivores Kathleen A. Alexander University of California - Davis

N. James MacLachlan University of California - Davis

Pieter W. Kat University of California - Davis

Carol House US Department of Agriculture

Stephen J. O'Brien National Cancer Institute at Frederick, [email protected]

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NSUWorks Citation Alexander, Kathleen A.; N. James MacLachlan; Pieter W. Kat; Carol House; Stephen J. O'Brien; Nicholas W. Lerche; Mary Sawyer; Laurence G. Frank; Kay Holekamp; Laura Smale; J. Weldon McNutt; M. Karen Laurenson; M. G. L. Mills; and Bennie I. Osburn. 1994. "Evidence of Natural Bluetongue Virus Infection among African Carnivores." American Journal of Tropical Medicine and Hygiene 51, (5): 568-576. http://nsuworks.nova.edu/cnso_bio_facarticles/801

This Article is brought to you for free and open access by the Department of Biological Sciences at NSUWorks. It has been accepted for inclusion in Biology Faculty Articles by an authorized administrator of NSUWorks. For more information, please contact [email protected]. Authors Kathleen A. Alexander, N. James MacLachlan, Pieter W. Kat, Carol House, Stephen J. O'Brien, Nicholas W. Lerche, Mary Sawyer, Laurence G. Frank, Kay Holekamp, Laura Smale, J. Weldon McNutt, M. Karen Laurenson, M. G. L. Mills, and Bennie I. Osburn

This article is available at NSUWorks: http://nsuworks.nova.edu/cnso_bio_facarticles/801 Am. J. Trop. Med. JIsg.. 5 1(5), l994, pp. 568â€”576 Copyright C 994 by The American Society of Tropical Medicine and Hygiene

EVIDENCE OF NATURAL BLUETONGUE VIRUS INFECTION AMONG AFRICAN CARNIVORES

KATHLEEN A. ALEXANDER, N. JAMES MacLACHLAN, PIETER W. KAT, CAROL HOUSE, STEPHEN J. O'BRIEN, NICHOLAS W. LERCHE, MARY SAWYER, LAURENCE G. FRANK, KAY HOLEKAMP, LAURA SMALE, J. WELDON McNUTf, M. KAREN LAURENSON, M. 0. L. MILLS, ANDBENNIE I. OSBURN Department of Veterinary Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, California; Foreign Animal Disease Diagnostic Laboratory, U.S. Department of Agriculture, Greenport, New York; Laboratory of Viral Carcinogenesis, National Cancer Institute, Frederick, Maryland; California Regional Primate Research Center, University of California, Davis, California; Department of Psychology, University of California, Berkeley, California; Department of Psychology, Michigan State University, East Lansing, Michigan; Division of Environmental Studies, University of California, Davis, California; Uplands Research Group, The Game Conservancy, Newtonmore, Invernessshire, United Kingdom; National Parks Board, Kruger National Park, Skukuza, Transvaal, Republic of South Africa

Abstract. Bluetongue is an International Office of Epizogtics List A disease described as the century's most economically devastating affliction of sheep. Bluetongue (BLU) viruses were thought to infect only ruminants, shrews, and some rodents, but recently, inadvertent administration of BLU virusâ€”contaminated vaccine resulted in mortality and abortion among domestic dogs. We present evidence of natural BLU virus infection among African carnivores that dramatically widens the spectrum of susceptible hosts. We hypoth esize that such infection occurred after ingestion of meat and organs from BLU virus infected prey species. The effect of BLU virus on endangered carnivores such as the cheetah and African wild dog requires urgent investigation. Also, the role of carnivores in the epizootiology of this disease needs elucidation.

The bluetongue (BLU) serogroup of orbivi mortality has been described in a free-ranging ruses are insect-transmitted and infect wild and population of topi (Damaliscus korrigum)6 and domestic ruminants, principally sheep. The dis a captive eland (Tragelaphus strepsiceros).7 ease is common in tropical, subtropical, and Buffalo (Syncerus caffer) calves died after ex some temperate regions of the world. Twenty perimental infection,8 whereas blesbok (Damal five different BLU virus serotypes are currently iscus albifrons) developed subclinical infections identified) Bluetongue was first recognized but had a sufficient viremia to cause clinical dis when susceptible European sheep breeds were ease among sheep injected with blesbok blood.9 introduced into South Africa in the 17th century. While a number of serologic surveys for BLU It consequently was proposed that BLU virus virus antibodies have been conducted among Af originated in Africa and was spread to other rican ungulates'Â°' II and small mammals,'2 no parts of the world,2 although recent genetic anal such serosurveys have been reported for carni yses indicate that several BLU virus serotypes vores. A related group of viruses, African horse could have had a long evolutionary history in sickness (AHS), have long been known to infect North America.3 carnivores.'3 Domestic dogs are susceptible and The consequences of BLU virus infection dif have been reported to be capable of infecting the fer among ruminant hosts. Sheep infected with tick vectors of AHS.'3 Domestic dog mortality the viruses may show signs of bluetongue dis and abortion were recently documented follow ease, whereas infection of cattle is typically ing inadvertent administration of a BLU virus asymptomatic.4 Very little is known about the contaminated vaccine.'4 We report here that nat effect of BLU virus infection on wild ungulates ural occurrence of antibodies to BLU virus is in Africa; serologic studies indicate that a large widespread among African carnivores. proportion of wild ruminant populations have MATERIALS AND METHODS been infected by the viruses,5 but little infor mation is available on the adverse consequences Samples used in this study were largely col of such infection. Bluetongue virusâ€”associated lected in conjunction with our carnivore disease

568 BLUETONGUE VIRUSES IN CARNIVORES 569 and genetic surveys and were stored at â€”20Â°C 100 and 400 50% tissue culture infective dose and â€”80Â°Cin various serum banks until tested. (TCID@0) units. Titers were expressed as the in Serum samples were collected from African car verse of the final dilution of serum that provided nivores including domestic dogs (Canis fami at least 50% protection of Vero cell monolayers. hans, Moremi, Botswana; Masai Mara, Kenya), Serum titers > 30 were considered positive, and jackals (C'anis spp., various locations in Kenya), samples were not tested beyond a dilution of 1: African wild dogs (Lycaon pictus, Moremi, Bot 120. swana; Masai Mara, Kenya; Kruger National For the immunoprecipitation assay,'7 a conflu Park, Republic of South Africa; Serengeti Na ent monolayer of BHK-21 cells was infected with tional Park, Tanzania; Chipangali Breeding Cen BLU-lO at a multiplicity of infection of 0.5. tre, Zimbabwe), Simien wolves (Canis simien Twelve hours after infection, 35S-methionine ( I00 sis, Bale Mountains National Park, Ethiopia), p.Ci/ml) was added in methionine-deficient mm spotted hyenas (Crocuta crocuta, Masai Mara, imal essential medium. Cells were labeled for I Kenya), domestic cats (Felis catus, Masai Mara, hr. then washed three times with phosphate-buf Kenya), cheetahs (Acinonyxjubatus, Kruger Na fered saline before extracting with NET-NP4O tional Park, Republic of South Africa; Serengeti (0.1 SM NaC1, 50 mM Tris, pH 8.0, 40 mM National Park, Tanzania), lions (Panthera leo, EDTA, 0.01% NaN3, I mM phenylmethylsulfon Ngorongoro Crater and Serengeti National Park, yl fluoride, and 0.05% NP-40) for S mm. Nuclei Tanzania; Kruger National Park, Republic of were removed by centrifugation at 400 X g for 5 South Africa), large-spotted genets (Genetta ma mm. The 35S-methionineâ€”Iabeled lysate was culata, Masai Mara, Kenya), white-tailed mon preadsorbed with a I % volume of washed Pan gooses (Ichneumia albicauda, Masai Mara, Ke sorbin (Staphylococcus aureus; CalBiochem, La nya), and marsh mongooses (Atilax paludinosus, Jolla, CA) for 1 hr. The lysate was then centri Masai Mara, Kenya). Serum samples tested from fuged at 72,000 X g for 1 hr. The preadsorbed, American carnivores included coyotes (Canis virion-free preparation of 35S-methionineâ€”labeled latrans, California) and domestic dogs (Yolo and BLU viral proteins was incubated with 25 1iJ of Lancaster County Pounds, California). Samples antisera for 1 hr before adding 50 pi of 25% Pro from captive African wild dogs in America were tein A agarose beads. Ten micrograms of rabbit made available by the Brookfield, Cheyenne anti-canine IgG was added to all dog and hyena Mountain, and San Diego Zoos. sera to facilitate binding to Protein A beads. After Serum antibodies specific for a viral core pro an additional 30-mm incubation, the reaction was tein (VP-7) of BLU virus were identified with a washed three times with NET-NP4O. Sodium do commercial competitive enzyme-linked immu decyl sulfateâ€”polyacrylamide gel electrophoresis nosorbent assay (cELISA, Blueplate Special; Di sample buffer was added and the samples were agxotics Inc., Wilton, CT) and samples were subjected to electrophoresis and autoradiography. considered positive if they showed inhibition Identical immunoprecipitations were performed that was 30% of the negative control.'5 This with mock-infected BHK-21 cells as a negative test is highly sensitive and specific for the blue control. tongue serogroup of orbiviruses (98% and Seroprevalence levels among species and lo 99.4%, respectively) and has been tested for cality were compared by chi-square analyses; in cross-reactivity with a variety of related and comparisons where cells contained values of 5 nonrelated viruses including AHS serotypes 1-9, or less, Fisher's exact test was used.'8 epizootic hemorrhagic disease virus, bovine her pesvirus 1-3, bovine parvovirus, respiratory syn RESULTS cytium virus, bovine leukosis virus, bovine viral diarrhea, parainfluenza-3 virus, and anaplasma, Seroprevalence of BLU viral antibodies. Brucella abortus, and Mycobacterium paratu Seroprevalence of antibodies to BLU virus by berculosis (Reddington ii, unpublished data). species and location is presented in Table I. Pos Sera were tested for neutralizing antibody itive individuals were identified among most of against BLU viral serotypes 1-20 using a micro the free-ranging African carnivores sampled titer virus neutralization assay.'6 Cell culture (cheetahs, lions, domestic cats, African wild adapted BLU viral serotypes were titrated and dogs, jackals, domestic dogs, hyenas, large-spot diluted to obtain a virus concentration between ted genets). Variable levels of seroprevalence 570 ALEXANDER AND OTHERS

TABLE 1 Seroprevalence of bluetongue virusâ€”specific antibodies among nonruminant species *

Nondomestic carnivores in Africa ZimbabweWildSpecies Botswana EthiopiaKenyaNamibiaSouth AfricaTanzania dog 23/24 (96) NP (33) (83) (44) 0/7 (0)t iackal 1/3 (33) NS 3/56(5) NS NS NS 0/9(0)t Simien wolves NP 0/25 (0) NP NP NP NP NP Cheetah NS NS NS NS 0/2 (0) Ng 0/2 (0) NS Se 4/33(12) Lion NS NS NS 19/36 (53) 29/36 (81) Ng 28/32 (88) NS Se 15/33 (46) Spotted hyena NS NS 33/60 (55)1: NS NS NS NS 33/76 (43)@ W.t. mongoose NS NS 0/15 (0) NP NP NS NS M. mongoose NS NS 0/5 (0) NS NS NS NS NSDomesticSpotted genet NS NS6/18 2/10(20)NS NS10/12 NS8/18 NS

carnivores in Africa BotswanaEthiopiaKenyaDogSpecies 2/92: 13/41 (32) 0/7 (0)7/89: 9/51 (18) 11/92: 20/52 (39)1990: 7/90: 20/87 (23) 8/91: 4/53(8) (22)Cat 10/92: 13/63

(21)Domestic NSNS10/92: 7/34

and nondomestic carnivores in the United States SpeciesUnited States Domestic dog 0/174(0) Coyote 0/10 (0) African wild dog 0/13 (0)t

* values are the no. positive/no, tested (%). Carnivore sampling localities were Botswanaâ€”Moremi; Kenyaâ€”Masai Mare, jackals were sampled in several localities; Tanzaniaâ€”SerengetiNational Park (Se) and Ngorongoro Crater (Ng); Ethiopiaâ€”Bale Mountains National Park; Zimbabweâ€”Bulawayo; South Africaâ€”Kruger National Park; United Statesâ€”coyotesfrom California, domestic dogs from Yolo and Lancaster County (CA) pounds, captive wild dogs from zoos. NP = species not present in this locality; NS = species not sampled. t Captive population. @ Hyena population sampled in 1980. Â§Hyenapopulationsampledin 1990.

were noted among species: jackals and cheetahs ronegative samples did not precipitate any viral characteristically had low numbers of seroposi protein. live individuals, while most lions and hyenas Serum neutralization. Neutralizing antibod tested positive for BLU viral antibodies. Positive ies to 12 of 20 BLU viral serotypes were iden individuals often had high percent inhibition val tified in carnivore sera, and antibodies to BLU ues (Figure 1). viral serotypes 3, 8, 13, and 17 were especially No seropositive individuals were detected prevalent (Table 2). Neutralizing antibodies to among free-ranging Ethiopian wolves, marsh BLU viral serotypes 6 and 19 were exclusively mongooses, or white-tailed mongooses. All cap identified among domestic cats from the Masai tive African wild dogs from both Zimbabwe and Mara, Kenya. Serotype 14 neutralizing antibod the United States were seronegative. Coyotes ies were detected solely among domestic dogs and domestic dogs from California were tested and hyenas from this same area. Only African to determine the route of infection (i.e., oral ver wild dogs from Kruger National Park in the Re sus vector). public of South Africa demonstrated neutralizing Immunoprecipitation. An immunoprecipita antibodies to BLU viral serotypes 2 and 18. lion assay was used to confirm specific reaction More than 50% of the samples positive for neu of individual sera to the core protein (VP-7) of tralizing antibody had titers greater than or equal BLU virus (Figure 2). Seropositive samples to 120. Of the 163 cELISA-positive samples, strongly precipitated soluble VP-7, whereas se however, 77 did not demonstrate the presence of BLUETONGUE VIRUSES IN CARNIVORES 571

100%. Africa,25 with the exception of serotype 17, 90%. which has been identified only in the United 2 80% U States and parts of India. While many individ 50%. uals reacted with only a single serotype, some 50%. animals had neutralizing antibodies to several Z 4Q%. different BLU viral serotypes. Whereas sero w 30%, types are commonly used to define BLU virus variants, it might not be valid to classify BLU

lililIJi virus into such distinct groups;@ cross-reactions between serotypes and reassortment of viral EASTERN AFRICAN @LDDOGS genes among cocirculating viruses have been 627 In addition, BLU virus nucleotide se quence analyses have indicated a greater amount of divergence between the same serotype from ,(100% different geographic locations (serotype I from 90% @ 80% Australia and Africa) than between different se @ 70% rotypes from the same location (serotypes I and 60% T 50% 20 from Australia).28 We are therefore hesitant Z 40%, to draw specific conclusions from these data but 30% would suggest that the data indicate exposure to o 20% 10% an array of BLU viruses. 0% Of the 163 samples tested for neutralizing an SOUTHERNAFRICANWILDDOGS tibodies, 47% did not react with BLU viral se rotypes 1-20. The cause of this finding was not FIGURE 1. Comparison of competitive enzyme determined, but several potential explanations linked immunosorbent assay (cELISA) percent inhi might be proposed. Virus TCID50 and sample di bition among wild dogs sampled in eastern Africa (Ke nya and Tanzania) and southern Africa (Botswana and lution were selected to increase specificity be the Republic of South Africa). Significant differences cause cross-reactions among serotypes are an ac in bluetongue virus seroprevalence were found be knowledged problem in BLU viral diagnostics.@ tween these groups; also, southern African wild dogs However, this also reduces the sensitivity of the had considerably higher levels of inhibition compared with eastern African wild dogs. test. Furthermore, BLU virus 25, which was re cently identified in Kenya,1 could not be ob tained for the neutralization assays. This sero neutralizing antibodies against BLU viral sero type does not cross-react with any other BLU types 1-20 with the test criteria used. viral serotypes) There also may be other un identified serotypes of BLU virus that would be DISCUSSION detected by group reactive tests such as the cELISA but not by neutralization tests with ex Antibodies to BLU viruses are prevalent isting viruses. among a variety of free-ranging African herbi Since this was a retrospective serosurvey, we vore species (Table 3). Tests with varying spec did not have appropriate samples to isolate virus, ificities and sensitivities (agar gel immunodif but both the high cELISA and virus neutraliza fusion,10' 9-22 cELISA,@ and fluorescent tion titers imply that BLU virus had replicated antibody23' 24)were used to screen the herbivores, in the seropositive carnivores. The route of BLU but nevertheless, the surveys indicate that wild virus infection for these carnivore species is un and domestic ruminants in eastern and north known but could include either vector transmis eastern Africa (Kenya, Tanzania, Egypt, Sudan) sion or ingestion. Vector transmission of BLU usually have lower BLU viral antibody sero virus between ruminants is almost exclusively prevalence levels than those in southern Africa by Culicoides midges,29 but oral infection of do (Botswana, Zambia). mestic dogs has previously been described for a Antibodies to 12 BLU viral serotypes were closely related group of viruses that cause noted among the African carnivores tested. AHS.3Â° Experimental oral infection of sheep These serotypes have largely been described in with BLU virus resulted in clinical disease,31 and @ VP7 â€” â€”

572 ALEXANDERAND OTHERS

A B

1 2 3 4 5 6 7 8 9 1 2 3 4 567

VP2â€”@ VP2 @ VP7

FIGURE 2. Immunoprecipitation of 35S-methionineâ€”labeled bluetongue virus-lO (BLU-lO) proteins. A, lane I, monoclonal antibody (MAb) 034 a BLU viral core protein-2 (VP-2); lane 2, MAb 290 a BLU VP-7; lane 3, normal rabbit sera (NRS); lane 4, polyclonal rabbit a BLU-lO (#1097, 12/15/89); lane 5, hyena (positive by competitive enzyme-linked immunosorbent assay [cELISA]: +); lane 6, lion (+); lane 7, domestic dog (+); lane 8, domestic cat (+); lane 9, cheetah (+). B, lane 1, MAb 290; lane 2, NRS; lane 3, rabbit a BLU 10; lane 4, hyena (negative on cELISA: â€”);lane 5, lion (â€”);lane 6, domestic dog (â€”);lane 7, captive wild dog from the United States (â€”). Viral proteins are identified at the left of each autoradiograph. Note the precipitation of VP7 by seropositive carnivore sera.

we suspect that infection among carnivores oc- a high percentage of seropositive individuals, in curred by this route. We base this statement on cluding buffalo, wildebeest, and cattle. Carni observed seroprevalence levels among and geo- vores such as African wild dogs prey mainly on graphic trends within carnivore species. For ex- smaller herbivores such as impalas and Thom ample, the highest seroprevalence levels were son's gazelles.32 These gazelles had significantly noted among large carnivores such as lions and lower BLU viral seroprevalence levels (P < hyenas that prey on large ruminant species with 0.01, x2 = 64.47) than other bovid species.24

TABLE 2 Distribution of bluetongue virus serotvpes 1â€”20among African carnivores*

SpeciesSerotypes234689101314171819Eastern AfricaDomestic (K)XXXXDomesticdog (K)XXJackalcat (K)XWild (K)XXHyena(K)XXXXXXXLion(T)XXXCheetahdog

(T)XXXWild (T)XXXSoutherndog AfricaDomestic (B)XXXXWilddog(B)XXXXXLion(SA)XXXXWilddog

dog(SA)XXXXXXXX

* K = Kenya; X = serotype present among individuals tested; X serotype unique to species or region; T = Tanzania; B = Botswana; SA = South Africa. BLUETONGUE VIRUSES IN CARNIVORES 573

TABLE 3 Seroprevalence of bluetongue virusâ€”specific antibodies among African ruminants (herbivores) compiled from published surveys *

HerbivoretBotswanaâ€•Egypt2'Kenyaâ€•Sudan2'Tanzaniaâ€•Zambiaâ€•Buffalo283/325 (92)NSGazelleNPNP22/151 (87)NS7/19 (37)NS329/359 (7)NPNSNPImpala19/23 (32)NSNSNSTopi/tsessebe10/13 (83)NS36/114 (14)NSHartebeest2/3 (77)NP11/38 (29)NS3/22 (83)NPWildebeest5/13 (67)NP79/104 (76)NP10/12 (46)NSCattle548/583 (38)NP8 1/134 (60)NP45/98 (87)Sheep137/381 (94)5/30 (17)289/634(46)70/874 (8)NS187/214 (28)NSNSGoat230/278 (36)425/2,933 (14)239/938 (25)C276/980 (11)NSNSCamel26/32 (83)13/110 (12)C11/98 (81)4/31 (13)NS5/102 (5)NSNS

* Values are Ihe no. positive/no.tesled(%).NS = species not sampled; NP = species not present at this locality; C = goats and sheep were combined in Kenya. t Buffalo (Sv,,cerus caffer); gazelle (Gazella thomsoni); impala (Aepyceros rne!anzpu.s); topi (Damaliscus lunatus); harlebeest (Alcelaphus husela phus); wildebeest (Connochaeies taurinus).

Thomson's gazelles are not found in southern area (> 3,000 m above sea levePâ€•)does not sup Africa, but impalas had a significantly lower ser port Culicoides midges,37 and therefore, viremic oprevalence of BLU viral antibodies in Kenya ruminants would not be expected in this region. than in Botswana (32% and 83%, respectively; African domestic dogs may have been infect P < 0.01, x2 = 20.74).2224 This trend among ed after ingestion of livestock or wildlife offal, impalas is reflected in BLU viral antibody prey which forms a consistent part of their diet. Like alence levels and percent inhibition among pop wild dogs, domestic dogs in Kenya had signifi ulations of their eastern and southern African cantly lower seroprevalence levels than dogs in wild dog predators (33% and 96%, respectively; Botswana (22% and 39%, respectively; P = P < 0.01, x2 = 21.38; Figure 2). 0.03, x2 = 4.42). In Kenya, domestic cats lived Carnivore species such as white-tailed mon together with domestic dogs in Maasai tribal gooses, large-spotted genets, and jackals that households and were sampled simultaneously. largely scavenge from herbivore carcasses were Among all the carnivores examined, however, either seronegative or had low seroprevalence domestic cats alone tested positive for BLU vi levels. This is compatible with their scavenging rus 6 and 19 neutralizing antibodies (Table 2). of meat and skin rather than ingestion of organs These serotypes have previously been recorded such as spleen and liver, which are rapidly con among sheep in Africa25 and the Middle East.38 sumed by the predators that killed the prey. Kenyan domestic dogs and cats from the same Spleen contains the highest concentration of vi household thus had been exposed to different rus-infected blood in BLU virusâ€”infected sheep BLU viruses, and we propose this is best ex and cattle.33 Marsh mongooses, which primarily plained by differences in diets. prey on aquatic invertebrates,@â€• were seronega In this study, domestic dogs sampled from tive despite living in close sympatry with in BLU virusâ€”endemic regions of the United States fected ungulates. such as California were negative for BLU viral Captive wild dogs and jackals in Zimbabwe antibodies. This observation is rather surprising were largely fed horse meat and therefore, oral given the results obtained from African domestic infection with BLU virus would be unlikely.35 dogs. However, domestic dogs in the United However, captive canids would likely have been States are generally fed commercial diets and exposed to the vector because they were kept by would be unlikely to have access to uncooked open paddocks containing wild ruminant spe meat from viremic ruminants. A survey recently cies. All captive wild dogs and jackals were se conducted among domestic dogs in other parts ronegative, which further suggests that natural of the United States identified a number of se BLU virus infection of carnivores occurs orally. ropositive animals; the BLU virus-contaminated Ethiopian wolves and domestic dogs sampled canine vaccine was implicated as the cause of from the Bale Mountains National Park in Ethi seroconversion in these dogs (Osborne BI, opia were all seronegative. This high altitude MacLachlan NJ, unpublished results). If vectors 574 ALEXANDER AND OThERS

had been important in transmission of BLU vi mitted from carnivores to ruminants or whether ruses to domestic dogs, more seropositive mdi carnivores are dead-end hosts that only acquire viduals would have been expected. infection after ingestion of BLU virusâ€”infected Despite these observations, variation in host tissues from herbivores. preference among vectors cannot be excluded as an alternative explanation for the differences Acknowledgments: We thank Paul Rossito for labo noted in seroprevalence levels. Culicoides spe ratory assistance, Itsuro Yamani for samples of do mestic dogs, and Claudio Sillero-Zubiri and Dada Go cies have been shown to exhibit preferences telli for serum samples from Ethiopian wolves. among ruminant and avian species,39 and viral Brookfield, Cheyenne Mountain, and San Diego Zoos serotype has been shown to influence the rate of and the Chipangali Breeding Center contributed sam infection of C. variipennis.â€•Â°Carnivores such as ples of carnivores in their collections. lions and hyenas, which exhibit a high seroprev Financial support: The Seebe Trust, Wildlife Concern alence of BLU viral antibody, might thus be pre International, and the Hanley Foundation granted par tial financial support, and Diagxotics, Inc. provided ferred hosts over species such as jackals and technical and material support. mongooses. Similarly, vectors that prefer do mestic cats might be more competent in trans Authors' addresses: Kathleen A. Alexander, N. James MacLachlan, Pieter W. Kat, Mary Sawyer, and Bennie mitting serotypes 6 and 19 than vectors that pre I. Osburn, Department of Veterinary Pathology, Mi fer domestic dogs. Studies that include host crobiology and Immunology, School of Veterinary identification from blood meals,39 virus isolation, Medicine, University of California, Davis, CA 95616. and taxonomic assessment of Culicoides could Carol House, Foreign Animal Disease Diagnostic Lab oratory, U.S. Department of Agriculture, Greenport, be used to determine the applicability of such NY 11944. Stephen J. O'Brien, Laboratory of Viral alternative explanations. Carcinogenesis, National Cancer Institute, Frederick, Carnivores had stable antibody prevalence MD 21702. Nicholas W. Lerche, California Regional levels over time. No significant differences were Primate Research Center, University of California, Da detected in seroprevalence of BLU viral anti vis, CA 95616. Laurence G. Frank, Department of Psy chology, University of California, Berkeley, CA bodies between sampling periods among Bot 94720. Kay Holekamp and Laura Smale, Department swanan and Kenyan domestic dogs. Similarly, of Psychology, Michigan State University, East Lan no significant differences were found among hy sing, MI 48823. J. Weldon McNutt, Division of En ena samples from the same clan collected 10 vironmental Studies, University of California, Davis, CA 95616. M. Karen Laurenson, Uplands Research years apart (Table 1). Group, The Game Conservancy, Newtonmore, Inver Two important questions emerge from this nessshirePH2O 1BE,UnitedKingdom.M. G.L.Mills, study. The first concerns the potential impact of National Parks Board, Kruger National Park, Private BLU virus infection on susceptible carnivore Bag X402, Skukuza 1350, Transvaal, Republic of South Africa. hosts and the importance of this infection in car nivore population structure and regulation. Blue Reprint requests: Kathleen A. Alexander, Department tongue viruses are pathogenic for pregnant do of Veterinary Pathology, Microbiology and Immunol ogy, School of Veterinary Medicine, University of Cal mestic dogs, and BLU virus infection may ifornia, Davis, CA 95616. therefore have serious consequences for endan gered wild relatives. In addition, infection could manifest itself in a more insidious fashion REFERENCES through decreased competitive fitness, reproduc I. Davies FG, Mungai iN, Pini A, 1992. A new tive success, survival, and dispersal capability. bluetongue virus serotype isolated in Kenya. The second question concerns the role of car Vet Microbiol 31: 25â€”32. nivores in the epizootiology of BLU virus infec 2. Howell PG. Verwoerd DW, 1971. Bluetongue vi tion. Outbreaks of BLU virus unexplained by rus. Virol Monog 9: 37â€”74. importation of domestic or wild ruminants have 3. Heidner HW, lezzi LG, Osburn B!, MacLachlan NJ, 1991. 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