Pets and wildlife sharing diseases
A versatile virus makes disease control difficult where humans and wildlife meet, according to a recent study published in the journal PNAS.
The team were investigating the dynamics of canine distemper virus (CDV) infections in Tanzania's Serengeti National Park using data from 1984-2012. This is a puzzle made trickier by the fact that CDV infects a wide range of mammal hosts, the virus is only called "canine" because it was first discovered in dogs.
In 1992 there was an outbreak of CDV in the pet dogs living on the edge of the Serengeti. Shortly afterwards, in 1994, another outbreak wiped out nearly a third of park's lions. The proximity in both space and time of the two outbreaks led experts to conclude that the infection had been passed from the dogs to the lions.
This prompted a mass CDV vaccination campaign of domestic dogs in the area, successfully cutting infection rates. However, there were still sporadic outbreaks in the lion population that did not match up to infection in the dogs. This suggested that there could be other species in the park acting as a reservoir of infection. Due to CDV's promiscuous nature, scientists are as yet unsure what species this might be.
One of the research team, Dr. Mafalda Viana of Glasgow University, was careful to point out that we don't know exactly how CDV originally arrived in the Serengeti ecosystem: "It seems that domestic dogs could have started the infection cycle in wildlife, but we don't know exactly how and when it started."
Although some infection persists in the Serengeti it is important to continue vaccination of domestic dogs in the area surrounding the park to reduce the likelihood of transmission to wildlife, in particular the highly-endangered and CDV-susceptible African wild dog.
This highlights the difficulty of controlling the spread of disease where humans and wildlife come into contact. One important way that we can be good neighbours is to keep our domestic animals healthy to prevent them becoming a source of infection, but vaccination alone will not prevent disease entirely.