The Biology, Clinical Significance and Control of the Common Snake Mite, Ophionyssus Natricis, in Captive Reptiles Edward J
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O riginal A rticles The Biology, Clinical Significance and Control of the Common Snake Mite, Ophionyssus natricis, in Captive Reptiles Edward J. Wozniak1, DVM, PhD, Dale F. DeNardo2, DVM, PhD 1. Animal 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, Ophionyssus natricis (Parasitiformes: Macronyssidae), 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, mites, acariasis, ectoparasites, snakes. 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 Steatonyssus (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 ticks 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.