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Frontiers
An Epidemic in the Serengeti:
Dog Virus Kills Lions
July/August 1996
Tourists were the first to notice that the lions were sick. In 1994, they were taking a balloon ride over East Africa's Serengeti park when they saw the felines convulsing. Their guide contacted Melody Roelke-Parker, the park's wildlife veterinarian, and the race was on.
In a matter of months, Roelke-Parker and other scientists identified the killer, but not before 1,000 lions--one-third of the Serengeti population--had already died.
The culprit: Canine Distemper Virus (CDV).
The 1994 epidemic is not likely to repeat itself for at least five years, according to pathologist Linda Munson of the University of Tennessee who analyzed tissue from the dead lions. The lions surviving the infection should have long-lived immunity.
In a recent article in the journal, Nature, Munson and her co-authors recount the epidemic and the detective work involved in tracking the killer that almost devastated the NSF-funded Serengeti Lion Project.
The lions mortality rate has returned to normal. But the danger for future generations is far from over. "There is something very different about this virus," says Munson. "It is now much more pathogenetic to big cats then we've ever seen before."
Nor will the next generations of lions be able to move away from carriers. As a growing human population pushes against the park, lions are more and more likely to meet infected animals. This reality increases the pressure on wildlife managers to find ways of understanding and preventing the disease called CDV.
CDV is named for its primary host--domesticated dogs. The epidemic probably
started with dogs outside the park. Researchers suspect infected dogs interacted
with wild hyenas and hyenas brought the disease to the park.
The disease attacks the victim's blood cells, lungs and brain, leaving a
distinctive pattern of destruction and microscopic materials in cells which
Munson refers to as "little viral footprints." Seeing this pattern
allowed her to rule out pesticides or other possible killers as she started
the detective work.
Suspecting CDV, she sent the tissue samples to a specialist for confirmation.
Max J.G. Appel at Cornell University identified the virus using monoclonal
antibodies--proteins that are virus specific. When Appel's proteins attached
to the sample, he knew it was the CD virus.
Unfortunately, knowing what the disease is does not provide the scientists
with an easy way of stopping it.
"Vaccinating wildlife is not feasible," says Munson. The vaccine
used for dogs--a modified live virus--has a high possibility of causing the
disease in wildlife.
But there are other options. East African government officials have started
"Project Lion," a vaccination program for domestic dogs that live
near the park.
In the meantime, wildlife managers are watching for further outbreaks. But
it's difficult, notes Munson. Communication within the Serengeti is poor,
and the area is full of susceptible carnivores. "Sick animals just
disappear."
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