Molecular analysis provides insights into equine flu outbreaks in South America

The influenza virus viewed under an electron microscope. Image: Centers for Disease Control and Prevention
The influenza virus viewed under an electron microscope. Image: Centers for Disease Control and Prevention

Researchers have stressed the need for good biosecurity startegies to curb the global spread of equine influenza, saying major outbreaks that have taken place in South America since 1963 were caused by at least four different and independent introductions of the virus, primarily through international horse movements.

The study team said there was a need for good surveillance programs, appropriate quarantine measures and widespread vaccinations to minimize the risk of equine flu incursions.

Equine influenza virus is considered the most important respiratory pathogen in horses, as outbreaks of the disease cause substantial economic losses.

The H3N8 equine flu virus has caused respiratory disease in horses across the world, including South American countries.

Researchers Cecilia Olguin Perglione, Marcelo Golemba, Carolina Torres and Maria Barrandeguy conducted genetic research to paint a picture of equine flu infections in South America, which date back to 1963. Their aim was to assess the diversification of the virus, to infer their origin, and to estimate the dynamics of their geographical spread.

The molecular evidence suggested that outbreaks between 1963 and 2012 in South America were possibly due to the introduction of at least four different equine flu viruses, primarily through the international movement of horses.

However, analysis suggested South America was the starting point of the spread of the H3N8 virus in 1963. It is believed that virus of the H3N8 subtype crossed the species barrier from birds in the early 1960s and subsequently spread worldwide.

Indeed, it has been suggested that the H3N8 equine flu subtype originated in South America, since it was identified after the arrival of thoroughbred horses imported from Argentina to Miami in 1963.

However, in the case of later incursions, the molecular evidence showed migration links the other way, from the United States to South America.

The study team identified an increase in the relative genetic diversity of the virus in South America between 2006 and 2007, probably due to the co-circulation of different lineages, and a subsequent decline since 2009, probably as a result of the incorporation of the Florida clade 2 strain in vaccines.

The data highlighted the importance of taking appropriate measures to prevent outbreaks of the disease, Perglione and her colleagues wrote in the journal Pathogens.

“Taking into account that the spread of equine influenza virus worldwide is facilitated by the international movement of horses, adequate epidemiological surveillance programs, appropriate quarantine procedures and the maintenance of high levels of population immunity through vaccination with updated and efficacious vaccines, are critical aspects in the control of equine influenza,” the researchers said.

Molecular Epidemiology and Spatio-Temporal Dynamics of the H3N8 Equine Influenza Virus in South America
Cecilia Olguin Perglione, Marcelo D. Golemba, Carolina Torres, and Maria Barrandeguy.
Pathogens 2016, 5(4), 61; doi:10.3390/pathogens5040061

The study, published under a Creative Commons License, can he read here.

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