Avian metapneumovirus spreads in North America

Outbreaks of avian metapneumovirus have occurred in turkeys and broilers in Virginia, North Carolina, Pennsylvania, South Carolina and California. Photo: Hans Prinsen

Following the first detection of avian metapneumovirus (aMPV) subtype B in 2 Ontario turkey flocks in early May, the disease continues to spread in that province, a current hotspot of outbreaks within North America.

The Feather Board Command Centre (FBCC) of Ontario, an initiative that oversees poultry disease issues for the boards of the provincial poultry associations, issued an advisory for the aMPV upon its detection in the province as it is highly contagious.

Avian metapneumovirus is also known as Turkey Viral Rhinotracheitis in turkeys and Swollen Head Syndrome in chickens. It is a respiratory disease with symptoms similar to bronchitis and avian influenza. Mortality rates can be high. Transmission can occur through direct contact with infected poultry, via wild bird vectors, or through contaminated materials or equipment.

Numerous outbreaks

As of 27 June, the FBCC reported new aMPV cases in 12 counties in Ontario. There are also cases in the neighbouring province of Manitoba, the US and Mexico.

Within the US, recent cases of the disease were detected in late 2023 onward. Outbreaks have occurred in turkeys and broilers in Virginia, North Carolina, Pennsylvania, South Carolina and California. A few years ago, the disease (subtype C) was found in Minnesota.

Mitigation

Regarding Ontario, the FBCC states: “There are currently no active control programmes or disease-specific response plans for aMPV. The FBCC is working with government authorities to monitor the situation and coordinate any necessary response actions.”

No licensed aMPV vaccines are available in Canada or the USA, although emergency access to killed vaccines may be granted by the Canadian Food Inspection Agency on a case-by-case basis.”

New strain, new worries

In the US, scientists from the Georgia Poultry Laboratory Network and the Southeast Poultry Research Laboratory and Animal and Plant Health Inspection Service of the US Department of Agriculture have just published a paper examining the genetics of the new aMPV strain.

They state, “the recent detection of aMPV-A and -B subtypes in the United States marks a significant shift after a prolonged period free of aMPV following the eradication of the previously-circulating subtype C. Hence, the demand for molecular diagnostic tests for aMPV has arisen due to their limited availability in the US market.”

The team’s phylogenetic analysis of recently-isolated strains were clustered within the aMPV-A subtype and were found to be most closely related to recent Mexican strains. However, “a detailed amino acid analysis identified unique mutations in the G gene of the US isolates compared to Mexican strains.”

The team also compared the performance, cross-reactivity and limit of detection of their revised aMPV subtype-specific RT-qPCR test with 2 commercial kits, and found there were similar detection and subtyping capabilities.