O riginal A rticles

The Biology, Clinical Significance and Control of the Common , natricis, in Captive Reptiles Edward J. Wozniak1, DVM, PhD, Dale F. DeNardo2, DVM, PhD

1. Resource Center, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77510, USA 2. Department of Biology, Arizona State University, Tempe, AZ 85287, USA Downloaded from http://meridian.allenpress.com/jhms/article-pdf/10/3/4/2206552/1529-9651-10_3_4.pdf by guest on 28 September 2021

A b s t r a c t : The common snake mite, (: ), is a blood feed­ ing, mesostigmatid mite that parasitizes reptiles. Anemia, dehydration, dermatitis, and several blood-borne infectious diseases have been linked to infestations (Camin, 1948, 1953, Chiodini, et al, 1983). Severe pruritic dermatitis has been reported in humans bitten by Ophionyssus natricis (Schultz, 1975, Beck, 1996). All levels of Ophionyssus natricis infestation should be considered a serious problem worthy of prompt treatment. This article describes the general morphology, biology, and behavior of each life stage and discusses the compo­ nents of an integrated control and prevention program for the maintenance of mite-free snake collections.

Key Words: Ophionyssus natricis, macronyssidae, , acariasis, ectoparasites, .

GENERAL LIFE CYCLE in clusters on the inner surface of the cage lid or hide box. The rate of embryonic development is temperature dependent

The life cycle of Ophionyssus natricis consists of egg, and doubles with each five-degree increase between 2 0 and

larva, protonymph, deutonymph and adult stages and is best 30°C ( 6 8 and 8 6 °F). At 25°C (77°F), the interval between characterized as that of a nest parasite (Figures 1 and 2). The oviposition and hatching is only 40 - 50.hr. adult and protonymph stages are parasitic and feed on blood. Larvae: Larvae are small, white, fragile, non-feeding, six­ The larva and deutonymph are non-feeding, free-living legged mites that measure approximately 400 pm by 250 pm. stages. The morphology and behavior of Ophionyssus natri­ The outer integument is finely papillated. The developing cis suggest that the mite either evolved from or shares a fourth legs can be identified as crescentric structures under common ancestor with mammalian parasites in the genus the lateral integument caudal to the third leg. Larvae fre­ (Camin, 1953). In the pockets under the scales quently remain at the hatch site until they molt into of the snake, the parasite presumably found a microenviron­ protonymphs. With an ambient temperature of 25 - 30°C (77 -

ment equivalent to the nest habitat (Camin, 1953). 8 6 °F), progression to the protonymph stage requires 18-24 Aside from on large boids, Ophionyssus natricis is rarely hr. Successful molting requires a relative humidity of at least found on free-ranging snakes. In captivity, however, the pri­ 75%. Desiccation and ineffective molting are major causes of mary enclosure (cage) serves as the perfect nest-like larval mortality. environment. The life cycle is short (7-16 d), resulting in the rapid establishment of dense populations. The mite has been shown to thrive on most snakes and some lizards including southern alligator lizards, Elgaira mulicarnata, (Wozniak, personal observation), blue-tongue skinks, Tiliqua scincoides, (Wozniak, personal observation) and side blotched lizards, Uta stansburiana, (Goldberg and Bursey, 1991). The follow­ ing detailed descriptions of stage-specific morphologies and i b $ L - feeding behaviors were summarized from Camin (1953) and male + female larvs^* supplemented with observational data except as noted. The life cycle and photomicrographs of all of the life stages are

illustrated in figures 1 and 2 respectively.

MORPHOLOGY

Eggs: The eggs of Ophionyssus natricis are off-white to deutonymph ^ ' ^^Tprotonymph tan and ovoid structures (300 - 400 pm in length and 200 - 300 pm in width) that darken at one pole as development Figure 1. Life cycle of the common snake mite, Ophionyssus ensues. Freshly laid eggs are sticky and are frequently found natricis.

4 Journal of Herpetological Medicine and Surgery Volume 10, No. 3 and 4, 2000 Protonymphs: The unfed protonymph is an aggressive, licerae appear rudimentary and are presumably incapable of blood-feeding stage in the life cycle of Ophionyssus natricis. piercing skin. The deutonymph stage lasts only 24 - 26 hr at Protonymphs are similar to the larva in size but have four 25°C (77°F). Deutonymphs destined to become males are fre­ pairs of legs and well-developed chelicerae. The first pair of quently found riding on the dorsum of those destined to legs bear sensory receptors and are constantly waved in front become females. of the body in an antenna-like manner while the posterior A dults: A dult Ophionyssus natricis are active, three pairs of legs are used for locomotion. Unfed hematophagous, sexually dimorphic mites. In an unfed state, protonymphs often congregate on inanimate objects within the adults are small, inconspicuous and easily overlooked. the cage and swarm onto any source of disturbance including, Both sexes are tan and have a caudally tapered body. cleaning utensils, the caretaker’s hands, or the cage occupant. Microscopically, the dorsal and ventral surfaces are covered Upon contacting a suitable reptile host, protonymphs quickly with a series of scleritized plates and have a hairy appearance. crawl either under scales or around the eyes, attach and com­ Unfed adults are very active and will crawl around the cage mence feeding. Attachment to complete engorgement requires rapidly in search of a host. As with the protonymphs, the 3 - 7 d at 25°C (77°F). Newly engorged protonymphs drop mites attach and feed from the less heavily keratinized skin

from the host and congregate on rough surfaces within the between and under the scales and around the eyes. Downloaded from http://meridian.allenpress.com/jhms/article-pdf/10/3/4/2206552/1529-9651-10_3_4.pdf by guest on 28 September 2021

cage that are protected from light. Molting to the deutonymph Engorgement requires 4 to 8 d at 25°C (77°F). Fully engorged stage occurs 12 - 48 hr after engorgement. Protonymphs can males are ovoid, yellow to dark red or black and only slightly persist in the environment for up to 31 d without feeding. wider than unfed males. Fully engorged females are rounded Deutonymphs: The deutonymph is an active, but non­ caudally, dark red to black and often exceed 1300 pm in feeding life-stage. Deutonymphs are frequently found within length. Females can ingest up to 1500% of their body weight or on the cage, but seldom on the host. The dorsal and ventral in host blood at each feeding. Engorged females tend to crawl integument lacks the sclerotized plates and has a striated tex­ upward in search of a dark, moist, concealed area suitable for ture, giving it a “thumb-print” like appearance when ovipostion. Adult females will feed two to three times at one examined microscopically. The density of setae is markedly to two week intervals. Each blood meal results in the produc­

reduced in comparison to protonymphs and adults. The che­ tion of approximately 2 0 eggs.

4

Figure 2. Life stages of Ophionyssus natricis. 1. Egg. 2. Larva (adult male). 3. Protonymph. 4. Deutonymph. 5. Adult male, the black structure is the midgut and midgut diverticula which contain partially digested host blood. 6 . Adult Female. Scale bar = 100 pm.

Volume 10, No. 3 and 4, 20000 Journal of Herpetological Medicine and Surgery Pairing and mating behavior appears to take place only sumably seeking relief from the feeding-associated dermati- 1 before the first adult meal and is stimulated by the size of the tis. The skin at the feeding sites often becomes hyperemic and unfed female. Once a female weighs greater than 0.15 mg, edematous (Figure 3a). The dermal tissue around the embed- j males are no longer attracted to her. Since blood-fed females ded mouth-parts becomes infiltrated with heterophils, 1 will reattach and feed when their body weight decreases to lymphocytes and plasma cells (Figure 3b). Within crotalids, j 0.30 mg, it is likely that mating behavior is displayed only in mite-infestations have been associated with loreal pit inflam- j newly matured adults. Mated females have been shown to lay mation and impaction (Garrett and Harwell, 1991). 1 both fertilized and unfertilized eggs. Fertilized eggs develop Ophionyssus natricis protonymphs have been shown to ! into females, whereas males are produced parthenogenetical- swarm onto and bite humans who come into contact with ly. The two strategies of egg development result in cyclic infested cages. Although humans are accidental hosts and are , shifts in the sex ratio of adult mites. The periodic “outbreaks” only temporarily infested with Ophionyssus natricis, severe | of snake mites often reported by herpetoculturists probably bite-associated dermatitis has been reported (Schultz, 1975 represent the cyclic waves in which the predominant mite was Beck, 1996). the more conspicuous blood-engorged female. Under favor­ Mite Surveillance: Ophionyssus natricis is relatively easy j able environmental conditions, adult mites live up to 40 d to detect with a regular inspection program that includes a Downloaded from http://meridian.allenpress.com/jhms/article-pdf/10/3/4/2206552/1529-9651-10_3_4.pdf by guest on 28 September 2021 with or without feeding. search for both the free-living and parasitic stages. Inspection Feeding Behavior: The mouth-parts of and blood- of the snakes, cages, water bowls, hide boxes, and freshly j feeding mites consist of a pair of chelicerae flanking a central shed skins is recommended. In examining the water bowl, 1 peg-like hypostome (Harwood and James, 1979). The blade­ both the water surface and sediments should be carefully ; like chelicerae are pushed against the skin and rapidly moved inspected. Within the cage, special attention should be given j in a breast stroke-like fashion to create a penetrating wound. to the inner surface of the lid where resting mites, digested j The central hypostome is inserted into the skin and serves as blood (fecal material) and eggs are likely to be found. a hold fast (Harwood and James, 1979). Attached mites tend When examining snakes, close attention should be given to remain concealed under a scale and feed to repletion if to the periocular skin, chin shields, and the first two scale- undisturbed. Blood feeding in Macronyssidae is a biphasic rows on the lateral body. Any abnormally reddened areas or j process characterized by a prolonged period of slow ingestion widened gaps between scales should be closely inspected

followed by a brief period ( 1 - 2 d) of rapid engorgement at with a hand lens. Swabbing the sides of the body with gauze the end of the feeding cycle (Kim, 1985). Physiologic and immediately examining the gauze surface for dislodged changes similar to those described in ixodid ticks including mites is a good way to detect even low-level infestations. integumental thickening, have been shown to occur during Any material recovered from the cage and/or animal that the slow phase of engorgement (Kim, 1985). Host blood and resembles mites should be fixed in 70% ethyl or isopropyl interstitial fluid are taken in through the feeding channels alcohol, cleared, mounted and examined microscopically for located between the chelicerae and hypostome and is stored accurate identification (Furman and Catts, 1982). Clinicians in the stomach-like midgut. The midgut is a sac-like structure and herpetoculturists who wish to submit alcohol-fixed para- i with numerous diverticula or outpouchings (Figure 2, adult sitic for identification should contact Dr. E. J. male). The digestion of blood appears to be an intracellular Wozniak at AGK Reptiles and Veterinary Services (agkrep- ; process, similar to that described in ticks (Coons, et al, 1986). tile @ earthlink.net). Since the hypostome lacks the tooth-like denticles of ticks, feeding mites are highly susceptible to mechanical detach­ MITE CONTROL IN REPTILE VIVARIA ment. The behavior of detached, partially fed mites and the influence of such interruptions on the kinetics of blood feed­ The complex life cycle and wandering behavior of ! ing and the epidemiology of pathogen transmission have not Ophionyssus natricis make the mite difficult to control in been determined. many vivariums. Persistent and/or recurrent infestation is a Clinical Significance: Ophionyssus natricis has been impli­ common complaint amongst herpetoculurists. In general, par- | cated in the transmission of several blood-borne viral, asitic organisms with complex life cycles are most effectively bacterial, and filariid pathogens of snakes (Camin, 1948, Hull controlled using a carefully planned integrated pest manage- ] and Camin, 1959, Chiodini, et al, 1983, Schumacher et al, ment (IPM) system composed of measures that target all life ; 1994). The biological relationship between the mite and the stages (Pfadt, 1985). A multifaceted integrated control pro- i infectious agent probably varies markedly with the different gram for Ophionyssus natricis consisting of isolation, i types of pathogens and needs to be better characterized in sanitation, topical and systemic acaricides and habitat-based I many cases. In an that feeds once as a protonymph, pesticide applications is described below. multiple times as an adult, and can be easily displaced and Isolation: The wandering behavior and ability of unfed reattached to different hosts, both mechanical and biological mites to survive for prolonged periods of time makes isola- j transmission are possible (Harwood and James, 1979). Vector tion of infested a very important component of the ' competency studies are presently needed to better character­ control program. Cages housing infested snakes should be ; ize the role of Ophionyssus natricis in the transmission of placed in separate room designated as a quarantine area and i infectious agents with which the mite has been temporally maintained for a period of time that extends two to four j associated. weeks beyond the date that mites were last detected. To maxi- I Snakes heavily infested with Ophionyssus natricis fre­ mize the odds of detection and monitor the therapeutic i

quently become dehydrated, lethargic and fail to thrive. response, all snakes and their cages should be checked daily. 1 Many snakes become restless and take refuge in water, pre­ Within the quarantine area, each cage should be physically j

Journal of Herpetological Medicine and Surgery Volume 10, No. 3 and 4, 2000 Downloaded from http://meridian.allenpress.com/jhms/article-pdf/10/3/4/2206552/1529-9651-10_3_4.pdf by guest on 28 September 2021

Figure. 3a. Skin of an opaque, mite positive Burmese python, Python should be carefully examined and if possible, wiped down molurus bivittatus, showing the characteristic swelling in the skin and with gauze and rinsed with water to remove as many mites as membrane around the eye (conjunctival sac) that is often seen with heavy possible. infestations. Clusters of actively feeding mites were recovered from the conjunctival sac. Chemical Control Figure 3b. Biopsy of a mite feeding site demonstrating an influx of Acaricidal sprays: The careful use of a dilute insecticide inflammatory cells (arrows). Scale bar -1 0 pm. product labeled for use on live animals can rapidly reduce snake mite burdens. Dilute pyrethrins 0.03% (Mite & Lice

Figure 3c. Sweater box lid from a cage used to house a mite positive Bird Spray, 8 in 1 Products, Inc., Hauppauge, NY) and the snake. Two resting adult female mites and deposits of mite urates pyrethroid resmethrin (0.35% active ingredient, Durakyl, (arrows) can be seen on the inner surface. DVM Pharmaceuticals, Miami, FL) have both been reported to be highly effective against of Ophionyssus natricis (Mader, Figure 3d. Moat isolation of a mite-positive Southern copperhead snake, 1996). Pyrethrins and synthetic pyrethroids block neurotrans­ Agkistrodon contortrix contortrix. mission by disrupting sodium and potassium ion transport. Because of the potential for transcutaneous absorption and isolated using a moat system (Figure 3d). A few drops of dish accidental poisoning, it is recommended that all pyrethrin and detergent in the water decreases the water surface tension, pyrethroid products be quickly and thoroughly rinsed from causing any mites that contact the water to sink and drown. the animal immediately after application (Sidon, et al, 1988, Sanitation: Being a nest parasite, Ophionyssus natricis Mader, 1996). Formulations that contain oils, synergistic thrives in neglected cages and can quickly establish dense compounds or insect growth inhibitors should be avoided populations. It is recommended that cages housing infested because these compounds can either increase the rate of tran­ snakes be equipped as simply as possible and be totally emp­ scutaneous absorption or are themselves toxic (Mader, 1996). tied, washed, and refurbished at least twice weekly. Materials The organophosphate, trichlorphon (Chem-Tronics Inc., used in the cage (e.g., substrate and hide-box) should be dis­ Leavenworth, KS) when applied to both the animal and cage posable and constructed of non-porous materials. The entire as a 0.15% spray and left on for 24 hr, has also been shown to cage including the top should be washed in hot (> be highly effective against snake mites (Boyer and Boyer, 50°C:122°F) water (Camin, 1953). Waste materials from 1991). Organophosphates exert their neurotoxic activity by infested cages should be immediately bagged, removed from inhibiting the enzyme acetylcholinesterase and causing rigid the facility, and either incinerated, autoclaved or treated with paralysis. To avoid accidental poisoning by ingestion, it is an insecticide. At the time of each cage service, the snake recommended that the water bowl be removed for 24 hr

Volume 10, No. 3 and 4, 2000 Journal of Herpetological Medicine and Surgery 7 (Boyer and Boyer, 1991). Concurrent use of other and DeNardo, 1997 unpublished data). No clinical signs or cholinesterase-inhibiting insecticides (organophophates and clinicopathologic evidence of organophosphate poisoning carbamates) is not recommended. Animals treated with developed in any of the snakes on study and no significant trichlorphon and/or other organophosphates should be closely differences in plasma or red blood cell cholinesterase activi­ monitored for signs of toxicity. Signs of toxicosis include ties were demonstrated in high dose, normal dose or excessive salivation, development of an abnormal posture, untreated control animals (Wozniak and DeNardo, 1997, and muscle twitching (Mader, 1996). Any snakes exhibiting unpublished data). Species differences in susceptibility may these signs should be immediately taken off treatment, rinsed exist, however, and it is highly recommended that animals on thoroughly with soapy water and promptly treated with treatment be closely monitored for signs of organophosphate atropine (0.4 mg/kg IM) and fluids (20 ml/kg) (Mader, 1996). poisoning. Animals developing clinical signs indicative of Treatment of seizure activity with diazepam (0.5 mg/kg) may toxicosis should treated in accordance with the protocol be indicated in some cases (Mader, 1996). described above. To minimize the risk of accidental poison­ In cases of widespread Ophionyssus natricis infestation, ing of the host, it is recommended that dichlorvos not be used the cage racks and the room should be washed and treated in conjunction with other acetylcholinesterase-inhibiting insecticides. with an insecticide after the animals and cages have been Downloaded from http://meridian.allenpress.com/jhms/article-pdf/10/3/4/2206552/1529-9651-10_3_4.pdf by guest on 28 September 2021 removed. For this purpose, a low-odor insectide formulation The use of potentially harmful pesticides in the treatment approved for indoor use such as carbaryl or one of the pyrethrin of arthropod infestations is a procedure that poses risks to or pyrethoid containing products should be used as directed by non-target organisms including humans. People exposed to the label. All treated shelving and other surfaces should be organic insecticides have reported a spectrum of manifesta­ allowed to dry and aerate prior to animal replacement. tions including gastrointestinal disturbances, acute severe No Pest Strips: Placement of dichlorvos-impregnated neurological manifestations, seizures, neuromuscular weak­ strips (e.g., No Pest Strips, United Industries Corp., St. Louis, ness, paralysis and cardiac arrhythmias (Peter and Cherian,

MO) in the cage at the recommended 6 mm of strip per 10 2000). Exposure to organophosphates in particular can result cubic feet of cage area for 3 hr, three times per week for two in a variety of medically significant conditions ranging from weeks is a very effective mite control measure (Frye, 1991, mucous membrane irritation to acute poisoning and/or suba­ Klingenberg, 1993). Dichlorvos, being an organophosphate cute, delayed or chronic neurological, neurobehavioral and insecticide, works by the same mechanism of action as psychiatric syndromes (Jamal, 1997). Because of potential trichlorphon. Dichlorvos is highly volatile and is released health risks, all products containing pesticides should be han­ from the strip as a vapor. Within the cage environment, the dled with appropriate safety and personal protection vapor is believed to condense into a thin film that covers all equipment (i.e., rubber gloves, respirators, etc) and used as surfaces throughout the cage (Tillman, 1996), perhaps even directed by the label. the snake. Being a hazardous chemical, this product should Ivermectin: To control the actively feeding mites, the be handled only with gloved hands and used in strict accor­ snake should be treated three times at two week intervals dance with the package label. Transcutaneous absorption of with ivermectin as either an injection (200 pg/kg SQ) or topi­ dichlorvos with associated with dermal mutogenesis has been cal spray (Rosskopf, 1992, Mader, 1996). To prepare the demonstrated in laboratory animals topically treated with spray, 0.5 mis of injectable ivermectin for cattle (10 mg/ml) concentrated liquid formulations (Tungul, et al, 1991). is added to one quart of water, mixed and sprayed onto the Studies done on humans exposed to high levels of dichlorvos snake and its cage (Abrahams, 1992). Since ivermectin is not have shown rapid and protracted decreases in plasma and red water soluble, it is advisable to shake the spray vigorously blood cell cholinesterase activities (Mason, 2000). While before each use. To minimize light degradation, this and all there have been reports of toxic reactions in snakes treated other ivermectin formulations should be maintained in with dichlorvos (Mader, 1996), others have reported good opaque containers. Ivermectin is a gamma amino butyric results with no notable adverse effects at the recommended agonist that causes paralysis in nematodes and arthropods by dosage (Murphy and Armstrong, 1978, Klingenberg, 1993). binding to the alpha-subunit of glutamate-gated chloride To prevent the snake from having direct contact, the cut strip channels, resulting in an influx of chloride ions and neuronal should be placed in a ventilated container and suspended hyperpolarization (Plumb, 1995, Blackwell, et al, 1998). from the cage lid. To minimize the risk for ingestion, the While the recommended dose of 200 pg of ivermectin per kg water bowl should be removed during treatment of body weight is probably high enough to kill some mites, (Klingenberg, 1993). The authors have successfully used experimental work with closely related fowl mite, dichlorvos-impregnated strips at the recommended rate to Dermanyssus gallinae, demonstrated the dose of ivermectin treat a variety of snake species including cottonmouth; water required to kill the adult stages to be 400 to 500 pg/kg (Ash moccasin, Agkistrodon piscivorus, rhinoceros viper; river and Oliver, 1989). Further work on the susceptibility of jack, Bitis nasicornis, eastern diamondback rattlesnake, Ophionyssus natricis to ivermectin and the pharmicokinetics Crotalus adamanteus, Mojave rattlesnake, Crotalus scutella- of the drug including its margin of safety in snakes, needs to tus, Crotalus willardi, water snakes, Nerodia spp., Boa be done before dosages of this level are routinely recom­ constrictor, Boa constrictor, Brazilian rainbow boa, Epicrates mended. Studies have shown that mites and ticks can recover cenchria, ball python, Python regius, red ratsnake; corn from ivermectin-induced paralysis with time (Ash and Oliver, snake, Elaphe guttata, black ratsnake, Elaphe obsoleta, and 1989). Because of this, good sanitation and the concurrent fox snake, Elaphe vulpina. In a recent pilot experimental use of acaricidal sprays, and other integrated measures are study, a group of five Brazilian rainbow boas were exposed highly recommended adjuncts to ivermectin therapy. to strips cut at ten times the recommended width (Wozniak

Journal of Heroetological Medicine and Surgery Volume 10, No. 3 and 4, 2000 MAINTAINING MITE-FREE SNAKES selection may become dehydrated or deposit their eggs in unsuitable locations. The overall effect of these combined Eliminating contact between mite-free snakes and reptiles measures is a rapid reduction in the mite population density of undetermined status is a key factor in the maintenance of and disruption of the life cycle. Construction and implemen­ mite-free animals. All newly acquired snakes should be quar­ tation of a customized integrated control program including antined for a minimum of three to four weeks before moving continuous surveillance and adoption of barrier practices to them into the mite-free collection. Any snakes suspected of eliminate the introduction of mites are advisable for anyone having mites should be moat-isolated, further inspected, and who maintains captive snakes. appropriately treated. Cage cleaning tools, people’s hands, and other objects that have come into contact with snakes or the cages of snakes of undefined health status should all be treated with suspicion and properly sanitized before having REFERENCES direct contact with mite-free snakes. Access to mite-free facil­ ities should not be extended to anyone who has recently Abrahams R. 1992. Ivermectin as a spray for the treatment handled reptiles of undefined health status until the person for snake mites. Bull ARAV, 2(1):8. Ash LS, Oliver JH Jr. 1989. Susceptibility of Omithodoros Downloaded from http://meridian.allenpress.com/jhms/article-pdf/10/3/4/2206552/1529-9651-10_3_4.pdf by guest on 28 September 2021 has showered and changed clothes. Reptile shows that allow parkeri (Cooley) (: ) and Dermanyssus gallinae the indiscriminate handling of animals can be sources of DeGeer) (Acari: Dermanyssidae) to ivermectin. J Med Entomol, mites. 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Volume 10, No. 3 and 4, 2000 Journal of Herpetological Medicine and Surgery 9 Mason HJ. 2000. The recovery of plasma cholinesterase and Schultz H. 1975. Human infestation by Ophionyssus natricis erythrocyte acetylcholinesterase activity in workers after over­ snake mite. British J Dermatol, 93(6):695-697. exposure to dichlorvos. Occup Med, 50(5):343-347. Sidon EW, Moody R P, Franklin CA. 1988. Percutaneous Murphy JB, Armstrong BL. 1978. Maintenance of rat­ absorption of cis- and trans-permethrin in rhesus monkeys and tlesnakes in captivity. Univ of Kansas Mus Nat Hist Spec Pub, rats: anatomic site and interspecies variation. J Toxicol Environ 3:40. Health, 23:207-216. Peter JV, Cherian AM. 2000. Organic insecticides. Anaesth Schumacher J, Jacobsen ER, Homer BL, Gaskin JM. 1994. Intensive Care, 28(1): 11-21. Inclusion body disease in boid snakes. J Zoo Wild Med, Pfadt RE. 1985. Fundamentals of Applied Entomology. 25(4):511-524. Macmillan Pub., New York, NY:742. Tillman PC. 1996. Personal communication, School of Plumb DC. 1995. Veterinary Drug Handbook. Iowa Univ Veterinary Medicine, Univ of CA, Davis, CA. Press. Ames, IA:790. Tungul A, Bonin AM, He S, Baker RS. 1991. Micronuclei Rosskopf WJ. 1992. Ivermectin as a treatment for snake induction by dichlorvos in the mouse skin. Mutagenesis, mites. Bull ARAV, 2(1). 6(5):405-408. Downloaded from http://meridian.allenpress.com/jhms/article-pdf/10/3/4/2206552/1529-9651-10_3_4.pdf by guest on 28 September 2021

description, range of habitat and natural history. SC, 104pg., 175 photos $20.95 including shipping

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