Protecting animals from the diseases that affect their species and related ones is a herculean task in itself. Imagine having to worry about sicknesses that originate in canines ravaging felines? According to scientists, that is exactly the scenario that Siberian tigers, also known as Amur tigers (Panthera tigris altaica), are being challenged within Far Eastern Russia, and that vaccination is the only viable approach to protect them.
A new study has stated that the Siberian tiger is facing a major threat from Canine distemper virus (CDV) that leads to serious illness in domestic dogs (Canis familiaris), and can also infect other carnivores. While domestic dogs believed to be the primary source of the potent virus, the research found that other endemic wildlife has been serving as the principal source of CDV that is threatening an already endangered species of big cats with extinction.
"Understanding how tigers are catching distemper is absolutely crucial to helping us design effective measures to minimize the conservation impact of the virus," said Dr. Martin Gilbert, lead author of a study, in a statement.
A Ruthless Virus that Crossed Over
Canine distemper, the disease caused by CDV, is highly contagious and causes a wide range of complications in the infected animal. According to the American Veterinary Medical Association (AVMA), the disease critically affects the gastrointestinal, respiratory, and nervous systems of domestic dogs.
However, other related species such as coyotes, wolves, foxes, and jackals, along with animals such as minks, raccoons, and ferrets, can also be infected by the virus. The disease has also been found in big cats such as leopards, lions, tigers and other wild cats.
Though it was initially believed that the disease could not cross over to felines, a CDV outbreak among captive big cats in California in the 1980s confirmed that it was a cause for concern. The fears were further amplified in 1994 when lions in the Serengeti Reserve in Tanzania were devastated by a massive outbreak, and nearly 1,000 of them succumbed to it.
The long-held belief that the interaction of big cats in some form or the other with domesticated dogs was the primary source of the infection. Also, vaccinating dogs against the disease has been considered the most effective method of controlling it. However, the Siberian tigers in the Russian Far East do not interact with domestic dogs much. Therefore, it led the team to believe that dogs were not the cause of CDV among these tigers, and while vaccination was the only practical option to curb the spread of pathogens, it was not dogs who required it.
Tracing the Real Source
In order to identify the culprits affecting the Siberian tiger population, which numbers below 550 in Far Eastern Russia and neighboring China, the authors collected samples from domestic dogs, tigers, and other wild carnivores. They compared the viral genetic sequence data obtained from these samples and utilized antibodies to examine the pattern of exposure in each of the populations. The results confirmed the doubts of the researchers.
"The taiga forest where the tigers live supports a rich diversity of 17 wild carnivore species. Our findings suggest that more abundant small-bodied species like martens, badgers and raccoon dogs are the most important contributors to the CDV reservoir," explained Dr. Nadezhda Sulikhan, co-author of the study.
Vaccination—The Only Viable Strategy
The authors agreed that vaccination was the only feasible measure to tackle the problem. However, they stressed that it was the tigers themselves that had to be inoculated using injectable vaccines and not the local dogs. To ascertain whether existing CDV vaccines could offer wild tigers protection, the team tested serum procured from captive tigers that had been vaccinated with CDV vaccines. Surprisingly, the strain of CDV that had been identified in Russia was effectively neutralized.
Nevertheless, the researchers were faced with a practical hurdle—How can an abundant big cat population be vaccinated? The absence of an oral CDV vaccine makes the distribution of vaccines to such a large population via baited food impossible. To mitigate this, the scientists developed a computer model that demonstrated that even a low rate of vaccination (two tigers per year) had the potential to decrease the threat of extinction among these tigers remarkably (almost seventy-five percent).
If strategized smartly, the entire exercise could cost only $30,000 per year or lesser if the tigers are vaccinated when they are captured for regular radio-collaring studies. "This work shows that CDV in the Amur tiger is a solvable problem — a rare piece of good news for the tiger conservation community," concluded Dr. Sarah Cleaveland, co-author of the study.
