NEW DELHI: Leopards in India are infected by Canine Distemper Virus (CDV) disease that in its advanced stage makes the big cat less fearful of humans, say experts. It may cause the leopard to enter human settlements for food frequently. Its predation of domestic dogs (Canis lupus familiaris) has been the major potential route of getting the infectious virus.
In the recent past, the leopard-human conflict has become so common that most people hardly take note of it: A one-and-a-half-year-old boy was recently killed by a leopard in the Jamwaramgarh area of Jaipur district. On February 10, there were two reports – one from Maharashtra (Satara district) and Karnataka (Mysore district) – where leopards entered human habitations and were later captured.
On February 8, a wild leopard entered a Ghaziabad court in Delhi-NCR. A series of gory images and footage appeared as it attacked and injured eight people. Visuals of a disoriented leopard with blood around its mouth and growling were confined to a corner of the court.
A new study shows that CDV disease can also be the reason for the impatient behaviour of the leopard. The CDV is also known as canine morbillivirus, is a highly infectious single-stranded RNA virus in the Paramyxoviridae family, which causes neurological disorders such as ‘disorientation’ and ‘lack of fear’ in its advanced stage among carnivores.
The study ‘CDV in Tigers and Leopards in Nepal’ was published in an international, peer-reviewed journal Pathogens on January 28. It points out that between 2020 and 2022, six Indian leopards (P. pardus fusca) were presented to Nepali authorities with fatal neurological disease, consistent with CDV.
The study also points out that India’s carnivores like the tiger and leopard are also infected with the dangerous virus. “This is entirely possible as CDV-infected animals lose the fear of humans like in case of rabies,” says Dr Yadvendradev Jhala, Dean of the Wildlife Institute of India (WII).
The WII disease risk assessment report shows that CDV disease is present across the subcontinent. “I have detected CDV in lions, wolves, jackals, tigers, leopards and hyenas,” says Jhala. SP Yadav, Chairman of the National Tiger Conservation Authority, agrees with CDV-induced aberrant behaviour among carnivores. “CDV infection indeed results in aberrant behaviour of carnivores and a fear from human beings,” says Yadav.
How CDV acts?
The disease follows typical signs in all infected animals and is broadly classified into three stages. The initial phase occurs shortly after exposure and is characterized by intermittent fever and weaker immunity.
This followed an acute phase where the virus infects epithelial tissue, resulting in various clinical signs, including a crusting discharge from the eyes and nose, respiratory and gastrointestinal symptoms, and hyperkeratosis of the foot pads.
“Some animals succumb at this point, whilst others make a complete recovery,” the study says. In the third phase, animals develop neurological disease. The signs include disorientation and a lack of fear. Once an animal enters the neurological phase, mortality is almost inevitable, and this phase progresses to seizures and death.
The initial detection of CDV in free-ranging carnivores in Russia in 2003 and later confirmed in free-ranging tigers and leopards in Indonesia and India.
Feral dogs
Dogs are a major carrier of CDV. A study was done in 2014 on India’s leopard, which shows dogs have been found to account for up to 39% of the diet of leopards.
“A higher level of predation of dogs could account for greater levels of exposures of leopards,” says Prof. Nishikant Mukerji of Tiger Center Nagpur, a non-profit engaged in the conservation of Tigers.
Experts say dog vaccination is the only useful strategy to mitigate CDV disease risk.
The fatal virus