Canine Distemper in Endangered Ethiopian Wolves - Volume 21, Number 5—May 2015 - Emerging Infectious Disease journal - CDC
Volume 21, Number 5—May 2015
Research
Canine Distemper in Endangered Ethiopian Wolves
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Christopher H. Gordon, Ashley C. Banyard , Alo Hussein, M. Karen Laurenson, James R. Malcolm, Jorgelina Marino, Fekede Regassa, Anne-Marie E. Stewart, Anthony R. Fooks, and Claudio Sillero-Zubiri
Abstract
The Ethiopian wolf (Canis simensis) is the world’s rarest canid; ≈500 wolves remain. The largest population is found within the Bale Mountains National Park (BMNP) in southeastern Ethiopia, where conservation efforts have demonstrated the negative effect of rabies virus on wolf populations. We describe previously unreported infections with canine distemper virus (CDV) among these wolves during 2005–2006 and 2010. Death rates ranged from 43% to 68% in affected subpopulations and were higher for subadult than adult wolves (83%–87% vs. 34%–39%). The 2010 CDV outbreak started 20 months after a rabies outbreak, before the population had fully recovered, and led to the eradication of several focal packs in BMNP’s Web Valley. The combined effect of rabies and CDV increases the chance of pack extinction, exacerbating the typically slow recovery of wolf populations, and represents a key extinction threat to populations of this highly endangered carnivore.
Infectious diseases are a major cause of population declines in wildlife (1). Canine distemper virus (CDV; familyParamyxoviridae, genus Morbillivirus) constitutes one such threat and has caused outbreaks in a diverse range of wild mammals: black-backed jackals (Canis mesomelas) (2); lions (Panthera leo) (3); spotted hyenas (Crocuta crocuta) (4); fennecs (Vulpes zerda); rhesus monkeys (Macaca mulatta) (5); and aquatic species, including Lake Baikal seals (Phoca sibirica) and Caspian seals (Phoca caspia) (6). CDV has also affected several threatened carnivores, including the world’s most endangered felid, the Iberian lynx (Lynx pardinus) (7); the Santa Catalina Island fox (Urocyon littoralis catalinae) (8); and the Amur tiger (Panthera tigris altaica) (9). Rapidly expanding human populations increase domestic dog contact with wild canids (10,11), exacerbating the risk for disease transmission (12,13). CDV infections in different species are serologically indistinguishable due to the existence of a single stereotype of the virus.
The Ethiopian wolf (Canis simensis) is recognized as the rarest canid species in the world and as the most threatened carnivore in Africa. Fewer than 500 adult and subadult wolves remain in half a dozen suitable Afroalpine habitat ranges (14). The largest population is in the Bale Mountains National Park (BMNP) in southeastern Ethiopia, where wolf populations reach densities of up to 1.4 adults and subadults/km2 (15). On average, family packs contain 6 adult and subadults (range 2–20) and protect a home range of ≈6 km2 (16). Such high wolf densities, large packs, and intense social behaviors increase the risks for disease transmission (17). As a result of rabies outbreaks during 1991–1992 (18), 2003 (19), and 2008–2009 (20), wolf subpopulations in BNMP were dramatically reduced by 45%–75% .
Serologic evidence for CDV within wolf populations has been reported (21); of 30 samples tested during 1989–1992, a total of 9 (30%) were seropositive for CDV. This finding among wild mammal populations shows that survival rates among animals with canine distemper (CD) infection can be high, as most clearly evidenced in populations of rare or threatened species that are likely to be closely monitored by field conservation efforts. Furthermore, it is well established that the virulence of CDV can vary greatly depending on the infecting virus strain, the immunologic competence of the infected host, and the presence of preexisting infections that can be exacerbated by the immunosuppressive effect of infection with a morbillivirus (22).
Population viability analyses have been used to predict the effect of epizootics on wolf populations, and the findings suggest that periodic CD epizootics would play a relatively minor role in population persistence, even when modeled together with rabies (23,24). However, estimated CD-associated death rates in these models were low (15%–20%), and a caveat of the study findings was that the effect on wolf populations should be reassessed if death rates were >40% (23). These models predicted that populations could recover from outbreaks of rabies or CDV, but if the interval between disease outbreaks was <30 months, the likelihood of local extinction would be high in the absence of low-coverage parenteral vaccination campaigns (25).
To confirm whether CDV poses an extinction threat to Ethiopian wolves, we examined the effect of CDV infection on pack and population dynamics during 2 CD epizootics in BMNP and quantified their effect on the wolf populations. We investigated the source of CD epizootics in village dogs close to the geographic onset of the outbreaks and compared CD-associated deaths between domestic dogs and wild canids.
Animal care and use protocols for the ethical handling of domestic dogs in this study were approved by the Oxford University Zoology Ethical Review Committee (case no. ZERC040905). Animal care and use protocols adhere to the Animals (Scientific Procedures) Act regulations (1986) in the United Kingdom. Furthermore, all animal handling protocols were approved by the Ethiopian Wildlife Conservation Authority.
Dr. Gordon is the Kenya Country Manager for the Zoological Society of London. His current areas of focus are antipoaching efforts, protected area support, and biodiversity monitoring.
Acknowledgments
We are grateful to the Ethiopian Wildlife Conservation Authority and Bale Mountains National Park for permission to work in Bale. This manuscript was greatly improved by comments from Richard Kock and Tim Coulson.
The Ethiopian Wolf Conservation Programme is chiefly funded by the Born Free Foundation and the Wildlife Conservation Network.
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Suggested citation for this article: Gordon CH, Banyard AC, Hussein A, Laurenson MK, Malcolm JR, Marino J, et al. Canine distemper in endangered Ethiopian wolves. Emerg Infect Dis. 2015 May [date cited]. http://dx.doi.org/10.3201/eid2105.141920
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