February, 2023

It is almost spring in the United States, and for wildlife biologists at the National Wildlife Disease Program (NWDP), this means migratory bird season. This season is unlike any other as a new, highly pathogenic strain of avian influenza has been sweeping through migratory birds, backyard chicken coops and poultry farms.

What We Have Seen

The first U.S. case of the virus was identified in birds in December, 2021. Over the winter, as bird populations migrated south, the NWDP worked with counterparts across Central and South America to monitor the spread of what is called a Highly Pathogenic Avian Influenza (HPAI). The spread of HPAI follows the Pacific Migratory Flyway. Colombia was the first South American country to report HPAI cases, followed by Peru in November. Bolivia, Chile, Argentina, and Uruguay followed. In many cases, birds in backyard flocks and poultry farms have become sick and died, likely after being infected by migratory wild birds interacting with farms.

Wildlife agencies across South America are also seeing new and concerning trends. In January, authorities from Peru reported the deaths of sea lions that tested positive for HPAI. As of this writing, authorities have reported over 713 sea lion deaths in Peru, and one death in Chile. While cases in mammals have been found in the United States and Canada, the mass die-off of sea lions suggests that the virus may be spreading from mammal to mammal. If true, this would be the first time HPAI has spread from mammal to mammal in the wild.

Why Don’t Some Countries Have Cases?

Territories

One factor that has affected reporting across the Americas is the number of territories in the Caribbean. The World Animal Health Information System (WAHIS) is the global aggregator of animal disease data. WAHIS publishes data reported directly by a country’s wildlife or agricultural agency. In the Caribbean, the Cayman Islands are the only self-governing territory that independently reports cases WAHIS. In the case of most territories, including American Virgin Islands, British Virgin Islands, St. Kitts and Nevis, and the Grenadines, the governing nation (U.S.A., United Kingdom, France, respectively) is responsible for reporting disease data to WAHIS. The infrastructure and capacity for wildlife disease surveillance in Caribbean territories varies depending on the governing nation, and many of these territories do not have robust resources to support sampling birds, testing samples, and reporting data. For this reason, reports of HPAI in the Caribbean remain low.

Commercial Poultry Industries

On mainland Central and South America, Belize, Brazil, El Salvador, French Guiana, Guyana, Nicaragua, Paraguay, and Suriname all still report zero cases of HPAI. Brazil is the world’s largest exporter of chicken meat, with an industry that is expected to grow 6% in 2023. The Brazilian government actively conducts surveillance for HPAI in bird species. There is also a robust program for farmers and ranchers to report livestock and poultry diseases. China is the leading importer of Brazilian poultry, and the Chinese government has imposed import restrictions on U.S. states with reported cases of HPAI. Industry fear may be driving a resistance to report disease. Alternatively, large poultry operators may be implementing effective biosecurity measures to reduce the likelihood of migratory birds spreading the disease into their flocks. Similar concerns exist in El Salvador, which has the largest poultry industry in Central America, and sits along bird migration pathways.

Lack of Testing and Reporting Infrastructure

Another common characteristic of countries without reported HPAI cases is a lack of infrastructure for surveillance of disease in wild and domestic birds. French Guiana, Guyana, Nicaragua, Paraguay and Suriname all lack centralized systems where livestock and poultry owners can report diseases. This means that small-scale poultry farmers may have undetected cases of HPAI in their flocks. Trained professionals are also an important factor. These countries have few state biologists and veterinarians who can do the everyday science to detect animal diseases. These countries also have poorly developed laboratory infrastructure, lower levels of investment in disease surveillance, and undeveloped wildlife tourism sectors compared to their counterpart countries that have reported cases. So, the numbers may not tell the whole story. These countries may have HPAI cases circulating, without the resources to test for and report them.

What Can We Expect to See?

Countries across Central and South America are already collaborating on surveillance and control measures. With increased cooperation amongst neighboring governments, the world may see more countries reporting cases in the coming months. NWDP biologists are already predicting a rise in cases in the United Sas migratory birds make their way back North. To prepare for a spring case spike, the NWDP is working with partners at state wildlife agencies, providing proper equipment to test birds and maintaining a case database. The office will continue to provide accurate and up-to-date information on this epidemic.