The rise of bird flu

Dr Anjani Ganase warns that we should pay attention to the most recent rise of the Avian Influenza (H5N1) which is wreaking havoc among domestic and wild populations of birds. Here is what you need to know.

A brief history of avian influenza (H5N1)

Avian influenza first arose in the 90s in farmed geese in Southern China, resulting in the die off of 40 per cent of the farmed population in the area before spreading across Asia, Africa and Europe.

The avian influenza has resulted in deaths of millions of farmed birds with some transmission to wild bird populations, as well as some crossover infections to humans as a zoonotic disease. In Southern China, Guangzhou province is sub-tropical with a long humid summer season supporting a wetlands and river systems used for farming and agriculture. It is also a major wintering ground for migratory birds.

Around the time of the first major avian outbreak in 1996, China had ramped up its poultry farming by 300 per cent compared to the previous decade. In the following year, the first human case of avian flu was recorded in Hong Kong, and 1.5 million chickens were slaughtered to curb the spread of the virus.

Fast forward to 2003/2004, the virus was now circulating among a wider group of hosts including waterfowl, cranes, crows, herons, quail, sparrows, and turkeys. The virus which previously was not able to infect ducks, now had high virulence with certain species and even infect through the dust that landed on their feathers and often led to death. Human cases were also on the rise and confirmed cases in other domestic animals were revealed through local surveillance.

Much of the research over the years identified major modes of transmission through geese which roam between terrestrial and wetland ecosystems and serve as intermediate hosts between the farm poultry and the waterfowl. Furthermore, the migratory waterfowl facilitated the spread across Asia and Europe.

In 2014, the first case of avian flu was detected in a goose farm in North America resulting in the culling of many farm birds. Little was known about the impact on wild bird populations. But during 2014, the avian flu decimated European bird populations.

Avian influenza in this decade

The latest version of the virus has resulted in outbreaks in the Americas since 2021 via transatlantic migration from Europe where the virus is now endemic. By 2022 the virus had spread southwards into Mexico and Central and South America. The virus is deemed to be highly pathogenic, infecting not just birds, but also mammals, including sea lions and dolphins in Peru.

Assessments of the disease reveal significant deaths in wild bird populations in North America, including the northern gannets, black-backed gulls and the black vultures in 2021. In 2022, the virus moved south with reports of 22,000 seabirds dying off the coast of Peru. By March 2023, wild bird mass mortality events (more than 100 birds) have been recorded, and over 58 million chickens had been infected and culled in poultry farms across the United States and over seven million chickens in Canada.

The growing body of research to understand the impacts to wild bird populations in the Americas reveals more asymptomatic cases among many wild species, especially migratory species. It is thought that the biggest spread might be among colonial nesting birds (62 per cent of Caspian terns that nest around Lake Michigan died in 2022) and seasonal outbreaks have been identified during the summer months. The iconic bald eagles of the US got sick after consuming infected waterfowl.

The impact on wild birds is extensive, and many species of birds migrate between the USA and Trinidad and Tobago including the American coot, the common tern, lesser scaup, osprey peregrine falcon, the royal tern and occasionally the Caspian tern. Infections of some of these species have been observed in the US, namely the Caspian tern, common tern, and osprey. With the disease spreading via the nesting colonies, our treasured scarlet ibis is at risk, but we must also pay attention to our herons, egrets, boobies and tropic birds that all the nest in colonies. Many of which are found on Little Tobago, and in north-east Tobago. There are about 16 species of ducks, 13 species of terns and 19 species of egrets observed in TT all of which are likely to be vulnerable to the disease.

What is to be done?

While the outbreaks in the US have direct impacts on the rising prices of eggs and poultry, the more urgent question is how will our relevant authorities manage a potential outbreak on TT? Whilst PAHO is observing the spread in the region, their specific concern is the potential infection of humans. However, more needs to be done in the development of plans to curb the introduction and spread to bird populations in our islands.

While the management of migratory birds is difficult, management of imported bird and bird products can be undertaken, and a plan should be implemented for swift isolation and eradication of the disease in an event of local infection. Guidelines do exist for bird owners on how to protect their beloved birds; and a strict warning not to interact with dead birds.

Furthermore, we should build our capacity in surveillance of the disease in multiple sectors including universities, veterinary clinics and poultry farms. Most importantly, strategies to limit the spread of the disease to our wild bird population require education among the local tour operators and hunting associations.

Restrictions should be enforced by wildlife managers who should devise systems to limit contact in an event of an outbreak. While vaccinations are in the making, it’s not feasible to vaccinate the numbers of poultry at the rate that is required, and even less feasible for wild birds.