Bird flu source remains unclear in Kuttanad despite repeated outbreaks

Despite the Kuttanad region reporting seven bird flu outbreaks over the past 11 years, the source of the infections is yet to be identified.

While migratory and wild birds have long been suspected to be the carriers of the virus, testing of samples collected from such birds from across Kerala has failed to detect avian influenza.

A study by Kerala Agricultural University (KAU), in collaboration with NGOs and the State Wetland Authority Kerala (SWAK), found no direct evidence linking migratory birds to the bird flu outbreak reported in Alappuzha, Kottayam and Pathanamthitta districts in 2024. The findings were based on waterbird monitoring conducted between January and April 2024.

The study, led by P.O. Nameer, Dean, College of Climate Change and Environmental Science, KAU, analysed the presence of two common migratory duck species — Garganey and Northern Pintail —and compared their distribution with 10 bird flu epicentres reported in April/May 2024.

“Garganey and Northern Pintail numbers peaked in the districts between February and March. Crucially, both species were largely absent in April in the three districts when bird flu cases were reported and their sightings were far from the epicentres,” said Dr. Nameer, adding that migratory birds could not be confirmed as the source of avian influenza without virological testing.

The report further raised concerns about biosecurity lapses, particularly the practice of bringing ducks from Tamil Nadu and rearing them in wetlands.

Earlier, an expert panel constituted by the Animal Husbandry Department (AHD) following the 2024 avian flu outbreak suggested that migratory birds could be the source of the virus.

Boby Rajan, chief disease investigation officer, State Institute for Animal Diseases, Palode, said the assumption that migratory birds could be the source of the infection was based on “circumstantial evidence”.

Most avian flu outbreaks coincided with migratory seasons and initially occurred in wetland regions of Alappuzha and Kottayam, which attract large numbers of migratory birds. Dr. Rajan pointed out that the virus strain detected in domesticated birds in Kerala was the same as that found globally.

He said there was no mechanism for screening migratory birds. “Migratory birds act as reservoir hosts without showing symptoms and that collecting samples is difficult as they roost in marshy or inaccessible areas. Though samples collected earlier by the Avian Disease Diagnostic Laboratory (ADDL), Thiruvalla, tested negative, the possibility of infection from migratory birds cannot not be ruled out solely on that basis,” Dr. Rajan added.

Besides the ADDL, Kerala Veterinary and Animal Sciences University (KVASU) and the AHD, among others, collected samples from migratory and wild birds over the years, but none tested positive for avian influenza.

T.P. Sethumadhavan, former director, KVASU, and professor, University of Trans-Disciplinary Health Sciences and Technology, Bengaluru, said repeated outbreaks in Kuttanad called for detailed research and strong diagnostic studies.

“Though the government in 2015 assured that a National Centre for Bird Flu would be established in Alappuzha, nothing has materialised so far. Instead of assumptions, stakeholder-driven research, including comprehensive epidemiological studies, is required, along with a clear assessment of economic losses. Universities such as KVASU and the AHD should take the lead with greater emphasis on multidisciplinary studies,” Dr. Sethumadhavan noted.

Dr. Nameer, meanwhile, suggested continuous monitoring of wild birds, stricter biosecurity checks on poultry transport from neighbouring States, regular farm inspections and coordinated field investigations involving ornithologists, veterinarians and public health experts for early detection of avian influenza.