At the 150th American Veterinary Medical Association (AVMA) convention in Chicago in July 2013, Ahmed Ali of the Food Animal Health Research Program at Ohio State University outlined his investigation - with colleagues - of the attachment of avian and mammalian influenza viruses to the respiratory and reproductive tracts of turkey breeder hens.

Mammalian influenza viruses especially swine influenza viruses (SIVs) are frequently transmitted to turkeys, according to Ali. However, SIVs show differences in their tissue tropism and pathogenesis especially in layer turkeys. Despite previous studies indicating the importance of virus receptors in the outcome of infection, a direct correlation between the influenza receptor distribution and pathobiology of SIVs in turkeys could not be established.

In the Ohio study, the attachment patterns of an avian H7N2, swine H1N1 and H3N2 as well as seasonal human and pandemic H1N1 influenza strains to turkey tracheal, lung and oviduct tissues were determined using virus histochemistry.

In the respiratory tract, all the tested influenza viruses showed attachment to the tracheal epithelium. However, no attachment was recognised in the lung tissues despite the presence of both avian and human type receptors.

In the oviduct tissues, the avian H7N2 and both H1N1, and H3N2 SIVs showed varying level of attachment to the epithelium of different oviduct compartments. The most abundant virus attachment was observed in the epithelium of isthmus and uterus. In contrast, neither seasonal human nor pandemic H1N1 viruses did attached to the reproductive tract tissues, with the exception of minor attachment of the pandemic H1N1 to the isthmus.

These results indicate that virus histochemistry is a useful tool to demonstrate the actual in vivo influenza virus distribution pattern in different hosts.

Moreover, commented Ali, the abundant attachment of the several tested viruses to the lower reproductive tract in turkeys further highlight the potential risks of venereal transmission and egg-associated influenza virus spread in turkeys.

August 2013