By Ana Mano and Tom Polansek
SAO PAULO (Reuters) -Brazil’s vast and diverse geography, with the Amazon to the north, mountain ranges along the Atlantic coast and the Andes to its west, may have helped it avoid the U.S. fate of widespread bird flu among commercial poultry flocks by keeping migratory birds away from farms in the country’s interior.
Wednesday marks more than a month without a new bird flu case on a commercial poultry farm in Brazil, ending an observation period after its first such outbreak. The success brings hope to farmers that there will be no repeat of the persistent infections in the U.S., where the virus devastated the domestic egg industry and triggered lasting trade bans.
There are doubts, however, whether the landscape can offer long-term protection.
Bird flu has spread around the world, even reaching Antarctica for the first time in 2024, in a threat to poultry flocks, wild birds and mammals, including U.S. dairy cows.
In Brazil, the Andes may delay the entrance of virulent new strains for two or three years, said Alex Jahn, researcher at Oregon State University’s department of integrative biology.
But Brazil will remain at risk for outbreaks as wild bird populations now infected with the virus circulate more widely. South American birds can migrate in all directions depending on rainfall, Jahn said, unlike the north-south seasonal migration over the United States.
Those migratory flyways over the U.S. appear to be major vectors for contagion between wild birds and commercial poultry, said John Clifford, the U.S. Department of Agriculture’s former chief veterinary officer.
“If you look at the wild waterfowl patterns, that’s probably the key,” said Clifford. “We have four flyways coming in through the U.S.”
By contrast, the Amazon basin acts as a natural filter keeping wild birds away from Brazilian poultry, said Guillermo Zavala, a U.S.-based avian health consultant who has worked in the poultry industry for more than 30 years.
The wild birds spreading the virus tend to spend time in nesting areas north of the equator, he said.
Masaio Ishizuka, a senior epidemiologist at the Sao Paulo University, said evidence suggests migratory birds have now infected local Brazilian species, making the bird flu virus endemic in the world’s largest chicken exporter, which accounts for 39% of global trade.
Last month, Brazil’s first outbreak on a commercial farm led to the culling of about 17,000 breeding chickens, producing birds raised for meat. Since then, meatpackers BRF and JBS culled at least 141,000 healthy chickens preemptively.
Brazil has detected 174 cases of highly pathogenic avian influenza, or bird flu, since 2023, mostly in waterfowl along the coast, according to government data.
The United States has confirmed the virus in about 10 times as many commercial and backyard flocks since 2022, the USDA said. About 175 million U.S. chickens, turkeys and other birds have been culled.
China has blocked poultry products from Brazil and most U.S. states due to outbreaks, and other nations also restricted shipments.
Russia, Saudi Arabia and Mexico enforce statewide restrictions that only apply to poultry from Rio Grande do Sul, where the one commercial outbreak occurred. Japan and United Arab Emirates are among nations with even narrower import bans, restricting only poultry products from the town of Montenegro.
SECURITY MEASURES
Brazil’s first commercial outbreak hit a chicken breeding farm, where biosecurity rules are supposed to be stricter than on facilities where chickens are raised for meat, said Felipe Sousa, assistant professor at Sao Paulo University’s school of agriculture.
Security measures at breeding facilities require workers to shower before going in and use clean uniforms and shoes provided by employers.
Brazilian farmers are also required to put up fences 5 meters (16.4 feet) away from chicken houses and one-inch mesh screening, commonly known as chicken wire, both around the walls and the property to keep stray or wild animals away from flocks, Sousa said.
Many U.S. farms have similar precautions, except for the fencing and screening rules, said Ashley Peterson, a senior vice president at the U.S. National Chicken Council.
U.S. chicken flocks are tested for bird flu before being slaughtered as part of a monitoring program, she added.
Brazilian meat lobby ABPA and the government did not comment on pre-slaughter protocols.
Clifford, who works with a U.S. poultry export association, said he expects more commercial outbreaks in Brazil with the virus present in wild waterfowl.
“If they only have one, I would have a lot of curiosity about their surveillance program,” he said. “They would be darn lucky.”
Officials recently confirmed backyard and wild species outbreaks in the center of Brazil, showing the virus is traveling inland.
In response, Marcelo Mota, Brazil’s chief veterinary officer, said the country will enforce new biosecurity guidance for zoos, parks and conservation sites.
“We will be busy,” he said.
(Reporting by Ana Mano in Sao Paulo and Tom Polansek in Chicago; Additional reporting by Sybille de la Hamaide in Paris; Editing by Brad Haynes and Bill Berkrot)
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