Thiruvananthapuram zoo to test vaccine response in sambar deer after rabies deaths

THIRUVANANTHAPURAM: In a first-of-its-kind move, the Thiruvananthapuram zoo will send serum samples of sambar deer to the Institute of Animal Health and Veterinary Biologicals (IAH&VB) in Palode. The aim is to assess how effective the anti-rabies vaccine has been in wild deer following the recent rabies outbreak inside the zoo. The decision comes in the wake of two sambar deer dying of rabies within a span of one week. The anti-rabies vaccine being used on the deer was developed for domestic animals such as dogs and cattle. It has not been scientifically standardised for use in wild animals like the sambar deer. Zoo officials say that the testing, which was not carried out during earlier outbreaks, is now being taken up due to the recurring nature of the infection. A total of 64 sambar deer are currently undergoing a full five-dose vaccination course. As per the standard protocol, the vaccine is administered on days 0, 3, 7, 14, and 28. So far, the first two doses have been given. The vaccination is done using a syringe gun as the animals cannot be handled directly. Once the full course is completed, blood serum samples will be collected from random deer to check the level of antibodies developed against the virus. The deer that died had shown sudden changes in behaviour before death. According to zoo veterinarian Nikesh Kiran, the animals exhibited restlessness and an unusually aggressive attitude which are traits uncommon for the typically calm sambar deer. There were no visible bite marks. But the next day, the animal was found dead. Rabies was later confirmed, said Nikesh. Zoo officials suspect a stray mongoose could be the source of the infection, although this has not yet been confirmed. The zoo covers a vast area, and spotting or tracking a mongoose is not easy. Another possible source could be bats, but rabies has not been historically reported in bats in this region, he added. This year, three sambar deer deaths were reported from the zoo. The first case was reported in March, followed by two more in August, both of which were rabies-related. The remaining deer are under close observation, and so far, none of them are showing symptoms of infection. As a precautionary measure, all zookeepers and staff working closely with the deer have also been vaccinated. They received both pre-exposure and post-exposure shots, with annual boosters also being part of the protocol. Zoo officials confirmed that other animals were vaccinated earlier and do not require fresh doses at the moment. While the situation is under control, the zoo has ramped up its surveillance and is taking more steps to prevent another outbreak. The upcoming serum testing is expected to provide insights into how well the current vaccination strategy is working in a wild animal population, said Nikesh.