Why some influenza virus strains are capable of transmitting virus between species is being investigated using new molecular technology, according to Y.M. Saif, DVM, professor and head of the Food Animal Health Research Program, Ohio Agricultural Research and Development Center (OARDC) at Ohio State University at Wooster.

Current research at the OARDC suggests that the ability of influenza viruses to transmit between species is strain specific.

Some strains of swine influenza virus (SIV) belonging to the same type (H3N2) have the ability to transmit from swine to turkeys and vice versa. Others will simply transmit in one direction, and some are not transmissible between the two species.

In 1978, Saif reported on the first evidence of natural and experimental transmission of the H1N1 influenza A viruses from swine to turkeys. At that time, it was thought that influenza viruses are host-specific and not able to cross the species barrier.

In 2004, Saif recorded natural outbreaks of H3N2 influenza A viruses in turkey breeder flocks. Laboratory studies indicated these viruses are the so-called triple reassortants, since they include genetic elements of viruses from swine, human and avian species.

Later, extensive studies confirmed the interspecies transmission of H3N2 viruses.

The molecular basis for interspecies transmission is not known.

To solve that puzzle, Saif is currently attempting to delineate the molecular basis for interspecies transmission using a molecular technology known as reverse genetics. Early results indicate that the hemagglutinin gene is probably the main determinant of whether a given strain of the virus will cross the species line. Saif’s laboratory at OARDC is seeking to uncover the specific molecules on that gene that will control this characteristic.

Meanwhile, an H1N1 virus that was isolated from a county fair in Ohio in 2007, and a similar virus isolated from people who came into contact with the swine at the fair, are being used for intraspecies transmission studies.

Learning the attributes of influenza viruses that contribute to the interspecies transmission will be useful for planning control strategies.

Researcher: Y. M. Saif, Food Animal Health Research Program/OARDC at The Ohio State University at Wooster, OH. Contact Saif by phone (330) 263-3743, fax (330) 263-3677 or e-mail saif.1@osu.edu.