In June 2014, Health Talk first shared that a virus carried by domestic dogs is threatening the health of wild cats like the Serengeti lion. Now, in an update to that research, new findings led by the University of Glasgow and co-authored by the University of Minnesota suggest vaccinating domestic dogs against this virus, known as canine distemper, is not enough to keep Serengeti lions and their cohabitants, the endangered African wild dog, safe from infection.
Canine distemper virus has the potential to infect the 28 to 30 wild carnivore species in Tanzania’s Serengeti National Park, including wild cats. The disease can cause neurologic disease and reduce the likelihood of successful survival. That’s a big problem for endangered species that also face threats from habitat loss, poaching, and a changing climate. A 1994 outbreak, for one, resulted in the death of one third of the charismatic Serengeti lions.
To protect endangered big cats and African wild dogs from infection, University of Minnesota infectious disease ecologists Meggan Craft, Ph.D., and Craig Packer, Ph.D., worked with a team of international collaborators to investigate whether vaccinating domestic dogs near big cat conservation areas was enough to fully protect wild cats.
“In 2003, we thought we might be able to control the virus in lions by implementing a large-scale mass vaccination program of dogs living around the park,” said assistant professor in the College of Veterinary Medicine, Craft. “Domestic dogs were thought to be behind much of the disease transmission to wild cats. But it’s now looking like, while this has reduced infections a little, it stops short of doing enough to eliminate the threat of canine distemper for wild Serengeti carnivores.”
Vaccinating domestic dogs in a 10 km strip bordering the Serengeti’s most people-dense area has undeniably helped improve aspects of human health. Along with canine distemper protection, a single vaccination also protects against canine parvovirus and rabies. The result is healthier dogs and fewer cases of rabies in humans. However, despite key improvement to dog and human health, 50,000 vaccines administered to dogs in the 
area each year still aren’t enough to provide substantial protections to wild carnivores.
Researchers analyzed 6,866 domestic dog and 535 lion blood samples collected between 1984 and 2012 to learn that Serengeti lions still were exposed to canine distemper despite the introduction of domestic dog carnivore distemper vaccinations. Lions cannot easily be vaccinated against carnivore distemper themselves because of logistical challenges to the approximately 3,000 vaccines needed. Results from the new study raise the question of where, and in which carnivore species, is the virus maintained, if not in domestic dogs.
Ongoing research works to answer this question, and ultimately find a significant protection from canine distemper in the Serengeti.
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