Dynamics of a morbillivirus at the domestic–wildlife interface: Canine distemper virus in domestic dogs and lions

Abstract

Morbilliviruses cause many diseases of medical and veterinary importance, and although some (e.g., measles and rinderpest) have been controlled successfully, others, such as canine distemper virus (CDV), are a growing concern. A propensity for host-switching has resulted in CDV emergence in new species, including endangered wildlife, posing challenges for controlling disease in multispecies communities. CDV is typically associated with domestic dogs, but little is known about its maintenance and transmission in speciesrich areas or about the potential role of domestic dog vaccination as a means of reducing disease threats to wildlife. We address these questions by analyzing a long-term serological dataset of CDV in lions and domestic dogs from Tanzania's Serengeti ecosystem. Using a Bayesian state-space model, we show that dynamics of CDV have changed considerably over the past three decades. Initially, peaks of CDV infection in dogs preceded those in lions, suggesting that spill-over from dogs was the main driver of infection in wildlife. However, despite dog-to-lion transmission dominating cross-species transmission models, infection peaks in lions became more frequent and asynchronous from those in dogs, suggesting that other wildlife species may play a role in a potentially complex maintenance community. Widespread mass vaccination of domestic dogs reduced the probability of infection in dogs and the size of outbreaks but did not prevent transmission to or peaks of infection in lions. This study demonstrates the complexity of CDV dynamics in natural ecosystems and the value of long-term, large-scale datasets for investigating transmission patterns and evaluating disease control strategies.cross-species transmission | multihost pathogens | reservoirs | state-space models | serology T he genus Morbillivirus includes highly contagious, and often fatal, RNA viruses that cause diseases of great public health, economic, and conservation concern, such as measles, rinderpest, and canine distemper. Canine distemper virus (CDV) is distributed worldwide and affects an expanding range of host species, including domestic and wild canids (1, 2), marine mammals (3), felids (2, 4, 5), procyonids and ursids (6), and nonhuman primates (7-9). The propensity of CDV for host-switching has raised concerns about both potential risks for humans (10) and extinction threats to endangered wildlife (11-13).Although previously thought to be nonpathogenic in cats, outbreaks among large captive felids in the 1990s drew attention to CDV as a potential conservation threat to felids (2). The beststudied example of CDV infection in free-ranging felids comes from Tanzania's Serengeti ecosystem (Fig. 1A), where a CDV epidemic in 1994 killed ∼30% of lions (Panthera leo) and affected several Significance Morbilliviruses are a growing concern because of their ability to infect multiple species. The spill-over of canine distemper virus (CDV) from domestic dogs has been associated with severe declines in wild carnivores worldwide, and therefore mass...

Enhanced immunosurveillance for animal morbilliviruses using vesicular stomatitis virus (VSV) pseudotypes

“…The presence of PPRV in Serengeti buffalo is consistent with findings of PPRV antibody-positive wildlife species in the vicinity [43]. The detection of CDV-specific antibodies in 5 of the buffalo indicates that morbillivirus exposure in wildlife is not restricted to PPRV and is consistent with findings of CDV seropositivity in lions within the same ecosystem [44]. The co-circulation of PPRV and CDV in the same livestock and wildlife species may interfere with the accurate diagnosis of PPRV infection using existing serological techniques.…”

Advances in canine distemper virus pathogenesis research: a wildlife perspective

“…Thus, the question whether endangered wildlife should specifically be targeted for vaccination is raised. Several challenges associated with wildlife vaccination need to be considered including (1) knowledge on the safety and efficacy of the vaccine in the specific species targeted; (2) mode of vaccine delivery either during opportunistic animal handling (when fitting tracking collars, translocation or medical examination), or by hypodermic dart (could cause injury and stress), or orally through laced bait (reduced efficacy if not eaten by target species); (3) the logistics of administering the required booster shots; and finally (4) the cost involved in initiating and implementing a vaccination programme in wildlife [13,142,146,147].…”

“…Initially diagnosed as a life-threatening disease in domestic dogs (Canis familiaris), it has subsequently been recognized in a wide range of hosts including some non-human primates, posing a conservation risk to several free-ranging and captive non-domestic carnivores [10,11]. The ability of CDV to switch hosts has raised concerns about the extinction threat it poses to several endangered wildlife species [12][13][14].…”

Canine distemper and endangered wildlife: Is it time for mandatory vaccination of dogs?

“…However, although CDV transmission dynamics and maintenance in wildlife are more complex than previously stated [4], undoubtedly the primary reservoir of CDV for wildlife are the infected domestic dogs. Dog population size and density provide indeed optimal conditions for maintaining a large and dense susceptible population which act as a reservoir for CDV with potentially catastrophic impact for the conservation of isolated wild populations.…”

“…In some areas, mainly in spring and summer, when the number of wildlife juvenile individuals is higher, the scenario of overlap between the areas frequented by wildlife and by livestock guardian dogs (LGD) or stray dogs is not uncommon. In this scenario CDV transmission from dogs to wildlife has been well described in the African and European contexts [3,4]. Vaccine-based prophylaxis is the only effective way to keep clinical distemper disease under control in dogs.…”