Diseases continue to cross species barrier as global bird flu cases double

Climate change, animal trade and falling vaccination rates leading to rise

A trader with camels at a market in the village of A Thamama near Riyadh. Scientists believe the Mers coronavirus originates in camels. Reuters

Outbreaks of bird flu in mammals doubled in 2024 with other zoonotic diseases spreading and putting more humans at risk, says a new report on animal health.

The first assessment published by the World Organisation for Animal Health (WOAH) revealed animal diseases were migrating into unaffected areas. Half (47 per cent) of these have zoonotic – animal-to-human – potential.

In 2023, there were 459 outbreaks of bird flu recorded in mammals, but that number climbed to 1,022 across 55 countries a year later.

Climate change, the expanding animal trade and a five per cent reduction in livestock vaccinations between 2020 and 2022 contributed to the rise, the report said.

“The spread, prevalence and impact of infectious animal diseases is changing, bringing new challenges for agriculture and food security, human health and development, and natural ecosystems,” said Emmanuelle Soubeyran, director general of WOAH.

“By launching a new, annual assessment of the state of the world’s animal health, WOAH shines a light on our interconnected health issues and the solutions that can improve animal health and, by extension, global health.

“To limit the spread of highly damaging diseases, the global community must strengthen international co-operation and ensure equitable access to safe, effective vaccines, alongside other control measures.”

The findings come after the World Health Organisation (WHO) reported nine new cases of Middle East Respiratory Syndrome (Mers) in Saudi Arabia. The disease causes flu-type respiratory symptoms and has spread from camels to humans. Of new infections reported between March 1 and April 25, two were fatal.

Cases of bird flu in mammals have doubled, according to the most recent data. Reuters

But eight of the patients had no known history of contact with camels or camel products. Since the first report of Mers-CoV in Saudi Arabia in 2012, there have been a total 2627 laboratory-confirmed cases and 946 associated deaths.

The majority of cases (84 per cent), have been reported from Saudi Arabia, including the most recent infections, eight of which were in Riyadh and one in Hail. No human cases of Mers have been reported outside the region to date.

More than 630 million birds have been culled across two decades during bird flu outbreaks, also called high pathogenicity avian influenza. While the risk to humans remains low, more mammalian species that become infected - such as cattle, cats and dogs - the greater the risk of transmission to humans.

Bird flu was one of several animal diseases to affect new areas in 2024. One of those is peste des petits ruminants (PPR), a disease traditionally affecting sheep and goats in developing countries, that has re-emerged in Europe.

Symptoms in livestock include fever, gastroenteritis, pneumonia and sometimes death. African swine fever has also reached pig farms in Sri Lanka, travelling more than 1.8km from the nearest outbreaks, the report found.

Of all diseases notified to WOAH between 2005 and 2023, almost half were considered a threat to human health or with potential to make the jump from animals. The organisation currently operates two global vaccine banks, to protect animals against rabies and PPR, delivering vaccines to 30 million dogs in Africa and Asia.

In 2024, there were a further 3,517 cases of Bluetongue, an insect borne virus that spreads among livestock, in 23 countries, while Germany experienced its first outbreak of foot-and-mouth disease since 1988.

In Mexico, vets reported the first case of New World screwworm, a parasitic fly whose lava eat the flesh of warm blooded animals. The disease has also re-emerged in Nicaragua. As in humans, antimicrobial resistance (AMR) remains a significant threat to livestock and is predicted to jeopardise food security in two billion people by 2050.

AMR has increased as overuse of antibiotics has led to germs evolving to develop an ability to beat the drugs designed to kill them off. Europe saw the greatest decline in antibiotic use in animals from 2020 to 2022, Javier Yugueros-Marcos, head of the WOAH antimicrobial resistance and veterinary products department, said antibiotic misuse continued to cause wider issues in animal care.

“The declining use of antibiotics in almost all regions is encouraging but further reductions can be achieved,” he said.

“This can be done by prioritising preventive measures against animal diseases, with vaccination an essential component. The indiscriminate use of antimicrobials contributes to antimicrobial resistance, which is a major threat to both animal and human health.”