Journal of Zoo and Wildlife Medicine 49(2): 475–479, 2018 Copyright 2018 by American Association of Zoo Veterinarians

ERADICATION OF A TROPICAL ( BACOTI ) INFESTATION FROM A CAPTIVE COLONY OF ENDANGERED AMARGOSA VOLES (MICROTUS CALIFORNICUS SCIRPENSIS)

Sarah Mantovani, D.V.M., Nora Allan, M.S., Risa Pesapane, M.S., Laurie Brignolo, D.V.M., and Janet Foley, D.V.M., Ph.D.

Abstract: Staff at a university laboratory responsible for management of a captive insurance colony of endangered Amargosa voles (Microtus californicus scirpensis) discovered an outbreak of tropical rat (Ornithonyssus bacoti) infesting 106 voles. This bloodsucking mesostigmatid mite typically occurs in laboratory settings and can cause weight loss, wounds, or other negative impacts on health. The source of the infestation was likely feral , and the route was suspected to be straw bedding. Twenty-nine of the 106 (27.4%) infested voles developed ulcerated dorsal skin lesions that resolved when treated with topical selamectin. A triad approach was implemented to eradicate the mites, consisting of environmental management, individual treatment, and training. Voles were moved individually into a clean room containing only autoclaved materials (including straw), cages were treated with -impregnated cotton, treatment order was instituted to avoid transferring mites, and voles coming from outside were quarantined. All in an infested room were treated with topical selamectin, and personnel were trained on risks and new procedures. No adverse effects from the use of selamectin were identified, and this efficient protocol does not require the long-term use of acaricides. This report documents infestation of an endangered with an exotic parasite, safe use of permethrin and selamectin in this species, and comprehensive management to manage a large infestation. Key words: Amargosa vole, captive wildlife, Microtus californicus scirpensis, Ornithonyssus bacoti, selamectin, tropical rat mite.

BRIEF COMMUNICATION endangered24 and found in nature only in marshes in the Mojave Desert.12 The captive breeding Captive wild animals are at risk for infectious program is an insurance colony (against the disease not seen in their natural habitat.2,22 An possibility that the species could go extinct in important parasite of rodents in laboratory set- the wild) and a source for reintroduction into the tings is the tropical rat mite (Ornithonyssus baco- wild. Sources of mites into the colony were 16 ti). This bloodsucking mesostigmatid mite will investigated, and the mites eradicated by using a parasitize many species, including humans, and triad approach, incorporating environmental de- carries numerous pathogens in nature or follow- contamination, acaricides, and personnel training. ing experimental infection.1,4,5,7–9,11,13,17,18,20–22,26,27 The approximately 100 vole captive breeding Control is complicated because of its rapid colony was established with 20 wild-caught voles development, high fecundity, prolonged off-host in 2014 and supplemented with 12 voles in spring survival, and ability to travel a 100 m to find a 2016. There were 74 voles in captivity at the time host.14,25 the outbreak was detected. Indoor housing in a This report describes rat mite infestation in a restricted access building consisted of three captive colony of endangered Amargosa voles rooms designated rooms 2, 3, and 8. Staff entered (Microtus californicus scirpensis) in northern Cal- into a common entryway, where they put on shoe ifornia. This rodent is state and federally listed as covers, proceeded through a common hallway, and then accessed animal rooms, placing a second pair of shoe covers over the shoes upon entry. From the Department of Medicine and Epidemiology, Each room had a door to the outside reserved for School of Veterinary Medicine, University of California, materials to be autoclaved or trash. A microbio- Davis, 1 Shields Ave, Davis, California 95616, USA logic barrier cage in each room contained four (Mantovani, Allan, Pesapane, and Foley); and Office of the Campus Veterinarian, University of California, Davis, mice as sentinels for disease or parasites circulat- 1 Shields Ave., Davis, California 95616, USA (Brignolo). ing in the room. Outdoor housing consisted of Correspondence should be directed to Dr. Foley (jefoley@ mesocosms in pens in a nearby field. The pens ucdavis.edu). were lined with fine mesh wire cloth to prevent

475 476 JOURNAL OF ZOO AND WILDLIFE MEDICINE wild rodent incursion, although house mice were dozens of mobile mites present along lesion occasionally detected inside pens. Mesocosms edges; nevertheless, all lesions resolved within were plastic planters (140 3102 3 63.5 cm) filled 1–2 wk of topical application of approximately 0.1 with commercial potting soil and planted with ml of 60 mg/ml selamectin (Zoetis, Parsipanny, three-square bulrush (Schoenoplectus americanus), New Jersey 07005, USA). One staff person noted the only food item used by voles in the wild. occasional small 1–2 mm, raised, reddened, and Voles from the wild were quarantined for 2 wk pruritic bites on herself but did not and then subject to monthly health checks. As report them at the time (and only associated the weak pathogens were tolerated to allow animals bites with the voles after the mite was identified). to retain alleles to combat pathogens when Under compound light microscopy, mites were released in the wild, protocols did not include characteristic of O. bacoti, with eight legs on an routine antiparasite treatment. After quarantine, unsegmented, weakly sclerotized body, three setal voles were maintained singly, in sibling groups, or pairs on the sternal shield, an anal shield with a in mated pairs in polycarbonate isolator cages cranially positioned anus, anteroventral keel on with a wire top or in outside mesocosms. Water trochanter of pedipalp, gnathosoma with four was provided in a bowl, and rodent chow was pairs of setae, and a tritosternum. DNA from placed loose inside the enclosure. Wheat or rice four mites was extracted by using a Qiagen blood straw from a local feed store was stored in a bin and tissue kit (Valencia, California 91354, USA) and used to fill cages 10 cm deep. Cages were spot following manufacturer’s instructions for 18S cleaned daily, soiled straw was replaced, and voles PCR15 and a 16S fragment by using primers were fed and watered. Cages were washed month- 16Sþ1 and 16S2.6 DNA sequences were searched ly in an industrial washer, rinsed at 828C and with the Basic Local Alignment Search Tool by autoclaved at 1218C for 30 min. using the National Center for Biotechnology In January 2015, the care team first detected Information GenBank database (https://www. skin lesions in room 2 on voles’ cervical and ncbi.nlm.nih.gov/genbank/). All 18S samples scapular regions, followed by lesions in room 3 in from voles were 100% the same and had 96%

March, and in outside housing in September query coverage, with 99% homology with Orni- 2016. A total of 106 voles were documented thonyssus bursa (there were no 18S O. bacoti infested with rat mites, with 187 separate mite accessions in GenBank). The 16S fragments were detections (with some animals being diagnosed also identical among vole mites and were 95% more than once, Fig. 1). The last case was the homologous over the full amplicon with O. bacoti. single-known infested outdoor vole and detected Representative sequences were deposited in Gen- months after eradication had occurred indoors. Bank as MF872606 for 16S and MF741975 for This vole was placed outside in February 2016, 18S. showed no disease during monthly health checks, Prior to May 2016, cases were managed with and was found dead with heavy tropical rat mite topical selamectin on affected animals and cage infestation. Necropsy revealed mild pneumonia, mates, bedding was replaced, and caging and cardiomyopathy, and a possible portosystemic other fomites washed and autoclaved. Large-scale shunt. eradication was performed after a year because of Indoors, mites were seen frequently in cages. ongoing cases, bites on humans, and reports of the No mites were seen in quarantine or on sentinel same species of mite in a mouse colony on the mice, except after straw from contaminated vole other side of the campus (approximately 5 km cages was placed into the sentinel cage; infested away). mice did not develop skin lesions. Twenty-nine of Possible sources of mites included the original the 106 (27.4%) infested voles had gross skin field source, movement among facilities on per- lesions that typically were round, 0.5 to 1 cm in sonnel, introduction on fomites (most plausibly diameter, with raised, reddened edges and central the straw from the feed store), infestation of ulceration. A tissue biopsy was obtained from a outdoor mesocosms by wild rodents, and feral characteristic lesion and revealed focal erosive mice within the animal building. Despite a per- and mild, diffuse ulcerative pleocellular dermati- ceived population increase in local feral house tis with lymphocytes, plasma cells and neutro- mice, mesocosms were considered unlikely be- phils, and mites extending into hair follicles. The cause lesions were detected inside 2 mo prior to lesion extended minimally into the dermis. It was any voles being brought in from mesocosms. On- not known if the mites or self-trauma caused the personnel transport was unlikely: staff denied lesions. Voles with ulcerated lesions typically had having pet rodents or any exposure to rodents that MANTOVANI ET AL—RAT MITE ERADICATION FROM AMARGOSA VOLES 477

Figure 1. Number of detections of infestation with the tropical rat mite (Ornithonyssus bacoti) on Amargosa voles (Microtus californicus scirpensis) in a captive breeding colony between January 2015 and September 2016. could be sources of infection. The only staff teArrest, Ecohealth, Boston, Massachusetts individuals who had visited both infested colonies 01841, USA) and systematic decontamination of were campus veterinary staff, and they were cages and room surfaces. This method was at- scrupulous about protocols to avoid disease trans- tempted to avoid destroying commensal arthropod port. Mites from original field sites could not be fauna and because of safety concerns regarding ruled out, although tropical rat mites have never selamectin on neonatal voles. Treatment voles were been detected during extensive trapping of Amar- placed into autoclaved cages and given 2–3 per- gosa voles in the field. Feral mice occur in the methrin-impregnated cotton balls (that rodents animal building but have never been seen in vole should incorporate into nests), which were replaced rooms and mouse feces has not been detected. once weekly for 8 wk. Trained staff performed Mite eradication was initiated in May 2016 in animal care in cages containing permethrin before room 3 (29 voles). Surfaces of a new room were untreated, contaminated cages every day to prevent scrubbed weekly for 2 wk with germicidal deter- movement of mites. Treated cages were transferred gent (Sani-Plex 128, Quip Laboratories, Wilming- to a clean room after 2.5 wk of treatment and edges ton, Delaware 19801, USA). The room was of shelving dusted with 0.1% pyrethrin and 1% fogged for 10 min by using hydrogen peroxide piperonyl butoxide (Zodiac flea powder, Wellmark, (HaloSpray, Quip Laboratories). Materials were Schaumburg, Illinois 60007, USA). Success of the autoclaved at 1208C for 30 min and then not treatments was confirmed by thoroughly examining shared between rooms thereafter. Voles were beddingandcagesurfacesformitesandanimalsfor treated with approximately 2.5 mg of topical mites and lesions. selamectin once 4 days prior to moving. Two days Subsequent routine monitoring consisted of before the move, they were placed into fresh cages monthly examination of every individual for mites with autoclaved straw inside the original room. or lesions and indefinite quarterly submission of During the move into the clean room, staff were four voles for comprehensive necropsy (all with stationed in the building to handle cages to avoid concurrent medical conditions warranting eutha- contact with fomites. At no time did hallway or nasia). No rat mites have been found on animals original room personnel have direct contact with since eradication, leading to the conclusion that the clean room. Fipronil (Merial, Duluth, Georgia the procedures were effective. 30026, USA) was sprayed on gloves, the bottom Staff training was conducted to ensure that any of each cage, and countertops between cages. further infestations would be prevented, if possible, For the second room (30 voles), mite eradication and detected early, if they occurred. All personnel was performed beginning 19 July 2016 by using who had contact with voles were contacted indi- 7.4% permethrin-impregnated cotton balls (Mi- vidually to review proper vole care, including room 478 JOURNAL OF ZOO AND WILDLIFE MEDICINE cleaning order and procedures for introducing nomiques. [A morphological study of some Litomosoides supplies or voles into a room, to decrease the species from rodents ; taxonomic conclusions]. Ann opportunity for future outbreaks in the colony. Parasitol Hum Comp. [Parasite].1989;64(4):268–289. A triad approach successfully eradicated O. 2. Ballou JD. 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