2010 NORTHEASTERN NATURALIST 17(4):523–530 Documentation of the Rabies Virus in Free-ranging Fisher (Martes pennanti) in Pennsylvania Jeffery L. Larkin1,*, Jennifer Christine Wester1, Walter O. Cottrell2, and Melia T. DeVivo1 Abstract - Mammalian carnivores are the primary hosts for the rabies virus in terrestrial disease cycles. While rabies prevalence in Vulpes spp. and Urocyon spp. (foxes), Mephitis mephitis (Striped Skunk), and Procyon lotor (Raccoon) is well documented in Pennsylvania, the reintroduction of Martes pennanti (Fisher) provides another potential vector of this disease. We used a direct, rapid immunohistochemical test to examine brain material from 46 free-ranging Fishers collected throughout Pennsylvania from 2002–2008. Five Fishers had brain material unsuitable for rabies testing, forty Fishers tested negative for the disease, and one individual tested positive. The individual that tested positive was an adult male that was found to be positive for the Eastern Raccoon strain of rabies. This individual was trapped and radio-collared in July 2006 as part of a research project examining Fisher resource selection. Researchers monitored this individual weekly starting July 2006 until October 2006, when it was found dead beneath a brush pile. As Fisher populations continue to expand throughout portions of the northeastern United States, their potential as a vector of rabies should not be overlooked. Introduction Rabies is a disease caused by a lyssavirus that has a tropism toward mammalian neural tissue and is one of the oldest recognized infectious diseases (Rupprecht et al. 2001, Wunner 2002). The rabies virus attacks the host’s nervous system and is almost always fatal (Williams-Whitmer and Brittingham 1996). Rabies was primarily associated with Canis domesticus L. (Domestic Dogs) when rabies surveillance began in the United States in 1938 (McLean 1970, Rupprecht et al. 2001). However, since 1960, wildlife rabies cases have surpassed rabies cases in domestic animals (McLean 1970, Wampler 2007). This transition was largely due to canine rabies control efforts during the 1940s that included mandatory vaccination of Domestic Dogs and removal of strays (Herman 2008, Rupprecht et al. 2001). Although the number of documented wildlife rabies cases fluctuates yearly, a general increase of rabies in wildlife has been observed in the United States (Blanton et al. 2009). While bats are by far the most common species involved in transmitting rabies to humans (Messenger et al. 2003), other wildlife species such as Procyon lotor (L.) (Raccoon), skunks, and foxes are potential risk factors for human exposure to this virus (Rupprecht et al. 2001). Such species are known reservoirs of rabies virus and have adapted rather well 1Department of Biology, Indiana University of Pennsylvania, Indiana PA 15705. 2Pennsylvania Game Commission, Animal Diagnostic Laboratory, Orchard Road, University Park, PA 16802. *Corresponding author - larkin@iup.edu. 524 Northeastern Naturalist Vol. 17, No. 4 to urban and agricultural landscapes (Adams et al. 2005). It is important to recognize, however, that all unvaccinated wild or domestic mammals can contract rabies and potentially infect other susceptible animals (Herman 2008). Martes pennanti (Erxleben) (Fisher) is one such species that historically has had a low documented incidence of rabies. The low number of documented rabies cases in Fisher most likely reflects limited investigation of Fisher as a species potentially affected by this disease. However, the generalist diet of this forest-dwelling carnivore includes species that are known reservoirs for the rabies virus, including Raccoon, Mephitis mephitis (Schreber) (Striped Skunk), Vulpes vulpes L. (Red Fox), and vespertilionids (bats) (Dzialak et al. 2005, Wester 2009). For example, Raccoon occurred in the diets of Maryland, West Virginia, and Pennsylvania Fishers (Dzialak et al. 2005, Wester 2009), and Red Fox, bats, and Striped Skunk were also observed in the diets of Pennsylvania Fishers (Wester 2009). Fishers likely both kill and scavenge carcasses of potentially rabid animals when available (Dzialak et al. 2005). In Pennsylvania, Raccoons are frequently struck by vehicles, and thus may be available to Fisher as carrion. During the time of our study (2002–2008), 1798 positive cases of Raccoon rabies in Pennsylvania were reported to the Centers for Disease Control (Blanton et al. 2006, 2007, 2008, 2009; Krebs et al. 2003a, 2004, 2005). Additionally, 9542 Raccoons tested from 2000–2008 in the northeastern United States were positive for rabies (Blanton et al. 2006, 2007, 2008, 2009; Krebs et al. 2001, 2002, 2003a, 2004, 2005). The reintroduction of Fisher to Pennsylvania and other northeastern states combined with the species popularity among trappers further warrants concern regarding the species’ potential as a source of rabies virus transmission. The Pennsylvania Veterinary Laboratory tested two Fishers for rabies previously, and both were found to be negative (K. Herman, Pennsylvania Veterinary Laboratory, Harrisburg, PA, pers. comm.). Nationally, 10 Fishers have been documented with rabies since widespread testing began in 1960. All 10 cases were restricted to the northeastern states including New York (n = 3; 1965, 1994, and 2007), Maine (n = 2; 1973 and 1996), Massachusetts (n = 2; 1995 and 2002), New Hampshire (n = 2; 1994 and 1995), and Vermont (n = 1; 1996) (Blanton et al. 2008; Krebs et al. 1995, 1996, 1997, 2003a, 2003b). The most recent documented case of a Fisher with rabies occurred in the suburbs of Albany, NY (Grondahl 2007). This infected individual was shot by law enforcement after it attacked and bit a woman outside of her residence (Grondahl 2007). Although reports of rabies among Fisher are rare throughout the range of the species, Fisher may be of regional importance as a potential rabies virus transmitter. To determine whether rabies among Fisher is of concern in Pennsylvania, we tested Fisher carcasses collected from 2002–2008. Our objective was to document occurrences of rabies in Pennsylvania Fisher and to discuss its implications for Fisher management protocols. 2010 J.L. Larkin, J.C. Wester, W.O. Cottrell, and M.T. DeVivo 525 Methods From the Pennsylvania Game Commission (PGC), we obtained roadkilled and accidental trapper-killed Fisher carcasses that had been collected and stored from February 2002 to March 2008. One additional carcass was obtained from a radio-telemetry study that was conducted in southwestern Pennsylvania. Fisher carcasses were stored in freezers at PGC regional offices, transferred to Indiana University of Pennsylvania - Biology Department, and stored frozen (-20 °C) until necropsied. With few exceptions, each carcass had an accompanying kill report which included date and location of kill, cause of death, the name of the collector, and any other details regarding the carcass and cause of death. Rabies virus testing was performed by the United States Department of Agriculture Animal and Plant Health Inspection Service (USDA-APHIS) in New Castle, PA using direct, rapid immunohistochemical test (dRIT) as described by Lembo et al. (2006). Freezing specimens did not compromise the dRIT sensitivity to the rabies virus (Lembo et al. 2006). All previously detected genotype 1 variants of the rabies virus and representative lyssaviruses are recognized by this test (Lembo et al. 2006). The sensitivity and specificity of the dRIT were 100% (95% CI = 93.9%–100.0%) and 100% (95% CI = 96.3%–100.0%), respectively. These values are comparable to direct fluorescent-antibody assay (DFA), the traditional standard in rabies diagnosis (Lembo et al. 2006). The identification of the rabies virus variant (i.e., raccoon vs. skunk) associated with positive cases was determined via immunofluorescence using the Light DiagnosticsTM, Rabies Monoclonal Antibody Typing Set (Millpore Inc., Billerica, MA). Results Forty-six Fisher heads were collected from 21 Pennsylvania counties (Bedford, Blair, Bradford, Cambria, Centre, Clarion, Columbia, Elk, Fayette, Forest, Jefferson, Luzerne, Lycoming, Mercer, Mifflin, Somerset, Tioga, Union, Venango, Warren, and Westmorland; Fig. 1), and submitted to USDA-APHIS for rabies testing. Thirty-eight carcasses were vehicular mortalities, four were accidentally killed by trappers, and the cause of death for four individuals was unknown. Of the 46 Fisher heads submitted for rabies testing, 41 had brain material suitable for testing. Of the 41 Fishers tested, one (2.4%) tested positive for the Eastern Raccoon rabies virus variant. The individual that tested positive was a radio-collared adult male found dead under a brush pile in October 2006. The location of the mortality was such that vehicular strike may have actually been the cause of death. The animal had blood from multiple body orifices, but no other visible clues suggesting a reason for his death. A necropsy revealed extensive lung bruising and blood in the urine, but little else. The lung discoloration may have been an artifact from death or, even more likely, freezing. However, because the animal tested positive for rabies, no further examination or testing of the tissues 526 Northeastern Naturalist Vol. 17, No. 4 taken at necropsy was performed. Thus, the actual cause of death could not be determined. Discussion Pennsylvania has long been recognized as a state with high endemic indices of rabies (USDA-APHIS 2005). In addition to the one Fisher that tested positive for rabies during our study, 283 Raccoons, 62 Striped Skunks, 41 bats, 32 foxes, 6 Marmota monax L. (Groundhog), 4 Odeocoleus virginianus Zimmermann (White-tailed Deer), 2 Canis latrans Say (Coyote), and 1 Felis rufus Schreber (Bobcat) also tested positive for the disease in Pennsylvania during 2006 (Blanton et al. 2007). Among the counties from which Fisher carcasses in our study were obtained, the reported incidences of rabies from January 2002 to March 2008 included 512 Raccoons, 109 Striped Skunks, 69 bats, 49 Felis silvestris L. (Domestic Cat) , 47 foxes, 9 Bos taurus L. (Domestic Cow), 6 White-tailed Deer, 4 Bobcat, 4 Groundhog, 1 Domestic Dog, 1 Ovis aries L. (Domestic Sheep), 1 Capra hircus L. (Domestic Goat), 1 Ursus americanus Pallas (Black Bear), and 1 Fisher (Pennsylvania Animal Diagnostic Laboratory, unpubl. data, http://www.padls.org/notes/rabies.html) Figure 1. Distribution of confirmed cases of domestic and wild mammals infected with rabies in Pennsylvania from 2002–2008. Counties with stars had at least one Fisher carcass tested for rabies during this study. The circled star indicates the county from which a Fisher tested positive for rabies. (Data provided by A. Snow, Pennsylvania Department of Agriculture, Bureau of Animal Health and Diagnostic Services, Meadville, PA). 2010 J.L. Larkin, J.C. Wester, W.O. Cottrell, and M.T. DeVivo 527 (Fig. 1). The single Fisher that tested positive for the rabies virus in our study was only the eleventh (n = 11) Fisher to have ever tested positive for this virus (Blanton et al. 2007, 2008; Krebs et al. 2003a, b). All 11 cases were from the northeastern United States (Blanton et al. 2007, 2008; Krebs et al. 2003a, b). However, Fishers in western and central portions of the species range have not been thoroughly investigated for rabies infections. Results from a non-invasive hair-snare sampling effort in southwestern Pennsylvania from 2007–2008 indicated that the location where the rabiesinfected Fisher was found may support one of the highest density Fisher populations reported for the entire range of the species (Larkin et al. 2009). Southern Pennsylvania also consistently has the highest number of documented cases of Raccoons infected with the rabies virus annually (Pennsylvania Animal Diagnostic Laboratory, unpubl. data, http://www.padls.org/notes/ rabies.html). This observation is important because a high Fisher density in a region where Raccoon rabies is enzootic creates conditions where contact between Fishers and rabid animals may become increasingly probable. Rabies transmission primarily occurs between conspecific individuals (Blanton et al. 2009). Infection from rabies reservoirs associated with a specific virus variant to other species, known as spillover, occurs but rarely initiates subsequent infections (Blanton et al. 2009, Krebs et al. 2003b). However, rabies spillover and maintenance has occurred in foxes, skunks, bats, Coyote, and Raccoon within the United States (Guerra et al. 2003). Due to rabies spillover, rabies variants may adapt to secondary hosts and become enzootic within that new species (Guerra et al. 2003). The rabies-infected Fisher in our study was a result of spillover because it tested positive for the rabies virus variant associated with Raccoons. Fortunately, rabies spillover rarely leads to maintenance in carnivores that are not the primary hosts for a specific rabies virus variant (Krebs et al. 2003b). Additionally, the likelihood of rabies spillover and cross-species adaption in Fisher is unlikely due to limited intraspecific contact resulting from the species’ territorial behavior (Powell 1993). However, rabies-infected animals tend to behave abnormally due to the disease’s effect on the central nervous system (Williams-Whitmer and Brittingham 1996); therefore, intraspecific infection of rabies among Fisher is possible, particularly in areas with high Fisher population densities. Additionally, Fishers in Pennsylvania are known to consume Raccoon, Red Fox, Striped Skunk, and bats, which are all common reservoirs for rabies (Wester 2009). While transmission of rabies through consumption of infected animals is rare (West 1972), Pennsylvania Fisher may be more susceptible due to their frequent contact with many prey species that are known reservoirs of the rabies virus. The single rabies-infected Fisher documented in our study warrants concern. As Fisher populations in the northeastern United States expand, human encounters with rabies-infected animals may become more frequent. Presence of rabies among Fisher is perceived as uncommon; however, Fishers are reclusive animals and a rabid Fisher may go 528 Northeastern Naturalist Vol. 17, No. 4 unnoticed. In fact, if the individual that tested positive for rabies in our study had not been radio-collared, we would not have detected the infection. Although documented rabies cases among Fisher are rare, they can be a source of rabies exposure for humans and domestic animals (Krebs et al. 2003b). Moreover, rabies in wildlife is of great concern because it can lead to “silent epizootics,” where wildlife acts as reservoirs for the virus to grow and propagate, often reviving the virus in areas that were once considered rabies-free (West 1972). Occurrence of rabies among Fisher may become of regional importance, especially if managers intend to trap and transfer Fisher from areas of high population density to areas with low or variable Fisher population density (Lovallo 2008). Translocation of potentially infected animals could have detrimental effects not only on Fisher populations, but also on other wildlife, domestic animals, and people (Chipman et al. 2008). The Ontario Ministry of Natural Resources imposed a ban on the translocation of rabies vector species within areas of the province endemic for Raccoon rabies (Rosatte et al. 2009). An intrastate translocation protocol that prohibits moving Fisher from areas of Pennsylvania with high incidences of rabies to areas with low incidences should be developed and employed. Additionally, trapper education regarding the safe handling of carcasses should be considered in response to the recent decision to initiate a Fisher-harvest season in 2010. As Fisher populations continue to expand throughout portions of the northeastern United States, their potential as a vector of rabies should not be overlooked. Acknowledgments We are grateful to Molly Giles, Christopher Kirkhoff, Jim Kauffman, Andrea Evans, and Eric Ludwig for their contributions in the field. We are also thankful to Dr. Jan Humphreys and Mourad Gabriel who reviewed earlier drafts of this manuscript. This work was conducted under the approval of Indiana University of Pennsylvania- IACUC protocol # 02-0506 and Pennsylvania Game Commission general use permit # 75-2006. Literature Cited Adams, C.E., K.J. Lindsey, and S.J. Ash. 2005. Urban Wildlife Management. CRC Press, Boca Raton, fl. 328 pp. Blanton, J.D., J.W. Krebs, C.A. Hanlon, and C.E. Rupprecht. 2006. Rabies surveillance in the United States during 2005. Journal of American Veterinary Medical Association 229:1897–1911. Blanton, J.D., C.A. Hanlon, and C.E. Rupprecht. 2007. Rabies surveillance in the United States during 2006. Journal of the American Veterinary Medical Association 231:540–556. Blanton, J.D., C.A. Hanlon, and C.E. Rupprecht. 2008. Rabies surveillance in the United States during 2007. Journal of the American Veterinary Medical Association 233:884–997. Blanton, J.D., K. Robertson, D. Palmer, and C.E. Rupprecht. 2009. Rabies surveillance in the United States during 2008. Journal of the American Veterinary Medical Association 235:676–689. 2010 J.L. Larkin, J.C. Wester, W.O. Cottrell, and M.T. DeVivo 529 Chipman, R., D. Slate, C.E. Rupprecht, and M. Mendoza. 2008. Downside risk of wildlife translocation. Pp. 223–232, In B. Dodet, A.R. Fooks, T. Muller, N. Tordo, and the Scientific and Technical Department of the World Organization for Animal Health (OIE) (Eds.). Towards the Elimination of Rabies in Eurasia. Developments in Biologicals Vol. 131. Karger Publishing. Basel, Switzerland. 594 pp. Dzialak, M.R., T.L. Serfass, C.L. Brown, and J.J. Krupa. 2005. Fall and winter diet of a reintroduced Fisher (Martes pennanti) population in West Virginia and Maryland. Proceedings of the West Virginia Academy of Science 77:7–13. Grondahl, P. 2007. New neighbor was furry, fierce, and rabid. Times Union Newspaper, Albany, NY. Guerra, M.A., A.T. Curns, C.E. Rupprecht, C.A. Hanlon, J.W. Krebs, and J.E. Childs. 2003. Skunk and raccoon rabies in the eastern United States: Temporal and spatial analysis. Emerging Infectious Diseases 9:1143–1150. Herman, K. 2008. An update on the incidence of rabies in Pennsylvania in 2008. Available online at http://www.agriculture.state.pa.us. Accessed 12 December 2009. Krebs, J.W., T.W. Strine, J.S. Smith, C.E. Rupprecht, and J.E. Childs. 1995. Rabies surveillance in the United States during 1994. Journal of American Veterinary Medical Association 207:1562–1575. Krebs, J.W., T.W. Strine, J.S. Smith, D.L. Noah, C.E. Rupprecht, and J.E. Childs. 1996. Rabies surveillance in the United States during 1995. Journal of American Veterinary Medical Association 209:2031–2044. Krebs J.W., J.S. Smith, C.E. Rupprecht, and J.E.Childs. 1997. Rabies surveillance in the United States during 1996. Journal of American Veterinary Medical Association 211:1525–1539. Krebs, J.W., A.M. Mondul, C.E. Rupprecht, and J.E. Childs. 2001. Rabies surveillance in the United States during 2000. Journal of the American Veterinary Medical Association 219:1687–1699. Krebs, J.W., H.R. Noll, C.E. Rupprecht, and J.E. Childs. 2002. Rabies surveillance in the United States during 2001. Journal of the American Veterinary Medical Association 221:1690–1701. Krebs, J.W., J.T. Wheeling, and J.E. Childs. 2003a. Rabies surveillance in the United States during 2002. Journal of American Veterinary Medicine Medical Association 223:1736–1748. Krebs, J.W., J.S. Smith, C.E. Rupprecht, and J.E. Childs. 2003b. Rabies among infrequently reported mammalian carnivores in the United States, 1960–2000. Journal of Wildlife Diseases 39:253–261. Krebs, J.W., E.J. Mandel, D.L. Swerdlow, and C.E. Rupprecht. 2004. Rabies surveillance in the United States during 2003. Journal of the American Veterinary Medical Association 225:1837–1849. Krebs, J.W., E.J. Mandel, D.L. Swerdlow, and C.E. Rupprecht. 2005. Rabies surveillance in the United States during 2004. Journal of the American Veterinary Medical Association 227:1912–1925. Larkin, J.L., E.H. Ellington, J.C. Wester, M. Lovallo, and M. Dzialak. 2009. Estimating Fisher population size and distribution in Pennsylvania. Final Project Report submitted to Bureau of Wildlife Management, Pennsylvania Game Commission, Harrisburg, PA. Lembo, T., M. Neizgoda, A. Velasco-Villa, S. Cleaveland, E. Ernest, and C.E. Rupprecht. 2006. Evaluation of a direct, rapid immune-histochemical test for rabies diagnosis. Emerging Infectious Diseases 12:310–313. 530 Northeastern Naturalist Vol. 17, No. 4 Lovallo, M.J. 2008. Status and management of Fisher (Martes pennanti) in Pennsylvania (2008–2017). Bureau of Wildlife Management, Pennsylvania Game Commission, Harrisburg, PA. McLean, R.G. 1970. Wildlife rabies in the United States: Recent history and current concepts. Journal of Wildlife Diseases 6:229–235. Messenger, S.L., C.E. Rupprecht, and J.S. Smith. 2003. Bats, emerging virus infection, and the rabies paradigm. Pp. 622–679, In T.H. Kunz and M.B. Fenton (Eds.). Bat Ecology. University of Chicago Press, Chicago, IL. 810 pp. Powell, R.A. 1993. The Fisher: Life History, Ecology, and Behavior. University of Minnesota Press, Minneapolis, MN. 217 pp. Rosatte, R. C., D. Donovan, M. Allan, L. Bruce, T. Buchanan, K. Sobey, B. Stevenson, M. Gibson, T. MacDonald, M. Whalen, J.C. Davies, F. Muldoon, and A. Wandeler. 2009. The Control of Raccoon rabies in Ontario, Canada: Proactive and reactive tactics, 1994–2007. Journal of Wildlife Diseases 45:772–784. Rupprecht, C.E., K. Stöhr, and C. Meredith. 2001. Rabies. Pp. 3–36, In E.S. Williams and I.K. Barker (Eds.). Infectious Diseases of Wild Mammals. Iowa State University Press, Ames, IA. 558 pp. United States Department of Agriculture Animal and Plant Health Inspection Service Wildlife Services (USDA-APHIS). 2005. Cooperative rabies management program national report 2005. Washington, DC. 136 pp. Wampler, T. 2007. An update on the incidence of rabies in Pennsylvania in 2006. Available online at http://www.padls.org/notes/wampler2006.pdf. Accessed 12 December 2009. West, G.P. 1972. Rabies in Animals and Man. Arco Publishing Company, Inc. New York, NY. 168 pp. Wester, J.C. 2009. Assessing diet and disease in a reintroduced Fisher population in Pennsylvania. M.Sc. Thesis. Indiana University of Pennsylvania, Indiana, PA. 81 pp. Williams-Whitmer, L.M., and M.C. Brittingham.1996. Rabies wildlife damage control 1. Available online at http://www.cas.psu.edu/FreePubs/pdfs/uh083.pdf. Accessed 12 December 2009. Wunner, W.H. 2002. Rabies virus. Pp. 23–78, In A.C. Jackson and W.H. Wunner (Eds.). Rabies. Academic Press, San Diego, CA. 680 pp.