Can The World's Tigers Survive This Virus?
A virus, mainly affecting dogs, is threatening the remaining, endangered wild populations of tigers worldwide. If left unattended, it poses a serious threat to this species, now risking extinction within 50 years. Any conservation efforts towards tigers must keep canine distemper virus in their sights if we are to help this majestic animal survive as long as possible.
Tigers are endangered, but how many are there still out there?
(Photo: Dileep Kaluaratchie)
The tiger is the largest cat in the world and a fascinating creature. It is the favorite animal of many people and the national animal of India and understandably so. It is deadly, majestic, agile and beautiful. However, this species is severely endangered: there are fewer than 4,000 individuals remaining in the wild, down from 100,000 in early 20th century. There are many reasons for their disappearance, including habitat destruction and fragmentation, and poaching.
Which subspecies of tiger is most endangered?
There are officially ten tiger subspecies, though one became extinct in prehistory. Of the remaining nine, three (the Bali, Caspian and Javan tigers) became extinct at some point during the 20th century, and the remaining six are currently endangered. The largest surviving subspecies today are Bengal tigers, with a rough population estimate of 2,500 – in comparison, there are only 65 South China tigers, all in captivity, and no reported wild sightings of this particular subspecies in over 25 years. As such, the South China tiger is already considered functionally extinct.
(Photo: Toshihiro Gamo)
Isn't that a dog disease?
Canine distemper virus (CDV), despite its name, can affect a wide range of animals, including dogs, ferrets, red pandas, hyenas and seals. It can also affect animals from the felidae family (though not domestic cats – feline distemper is the virus exclusive to those animals), including tigers. This disease is very dangerous, due to its high contamination via inhalation and its deadly effects: it is fatal 50 percent of the time. This virus is a close relative to measles, and causes symptoms such as fever, hardening of the footpads and nose, paralysis, and seizures which may eventually lead to death.
This virus is a danger to more than just tigers. Introduced in the wild probably via domestic dogs, it poses a serious threat to many species. The black-footed ferret's near extinction can be partially attributed to this virus, and it has also played a significant role in the disappearance of the thylacine (also known as Tasmanian wolf). It already has been reported as the cause of death in several tigers in the wild, in climates as different as those of Siberia and India.
So why is this so bad for tigers?
A recent study by Martin Gilbert and colleagues, published in PLoSOne, studied the potential long-term impact of CDV on a tiger population in a nature reserve in Russia. They used simulations of infection both through tiger-to-tiger interaction, and through tigers hunting affected dogs and/or other carnivores, and used published observation data on current infection status to simulate high- and low-risk scenarios.
(Photo: Michele W)
Their results show that CDV poses a serious extinction threat to tiger populations. Infected populations are 6.3 to 55.8 percent more likely to be extinct within 50 years than non-infected populations, depending on the scenario they simulated. More importantly, smaller populations with only 25 individuals were likely to be more affected than larger populations.
Due to habitat destruction and human movement, many wild tiger populations are reduced to small, isolated patches, often with roughly 25 breeding adult individuals. These small but often dense populations mean that CDV is a particularly important threat to the conservation of tigers worldwide.
What we humans can do to help tiger conservation
Just like for the measles virus affecting humans, there is no real treatment for canine distemper virus, but a symptomatic and supportive approach can help affected animals survive through the infection. There are currently studies investigating potential treatments, trying to improve their efficacy by reducing negative side-effects, but veterinarians and medical professionals agree that prevention is the best course of action. There exists a vaccine for domestic dogs and ferrets, but no such vaccine is approved for non-domestic felines yet.
(Photo: Harvey Barrison)
Tiger conservation efforts must keep canine distemper virus in mind when attempting to care for both wild and captive tigers. Careful observation, and potential isolation and treatment of infected animals until recovery, will be vital for tigers to survive more than 50 years.
By Marion Thibaudeau.
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