How investigating the piglet helps us advance influenza control

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Weaning-age piglets are responsible for the spread of many diseases, but in the case of influenza, they are also responsible for circulating the virus within the herd. 

While examining the role of the sow and the environment in the propagation of influenza virus in sow herds, Montse Torremorell, DVM, PhD, and her team incidentally found viable virus on the udder skin of lactating sows, making Torremorell the first researcher to describe a new route for transmission of influenza in suckling piglets. 

75% of the samples from sows’ underline showed viable influenza virus that could potentially infect piglets.

Even though all piglets are born influenza negative, they can become infected shortly after birth and start shedding virus in their nasal and oral secretions. While these piglets suckle, they deposit live virus particles on the sow’s underline skin that can in turn infect other piglets in the litter. Thus, a key factor in controlling influenza is to know when and how piglets become infected. 

Torremorell and her team designed a new sampling technique called “the udder wipe” to analyze viruses present on the udder skin of lactating sows. Seventy-five percent of these samples showed viable influenza virus that could potentially infect piglets. 

Piglets nursing on a sow

Additionally, Torremorell and her graduate student, Jorge Garrido, investigated the role of nurse sows as a possible source of virus. Nurse sows are animals with good mothering ability that have just reared their own litter and are used to adopt poorly performing piglets. They demonstrated that nurse sows did not shed a lot of influenza virus in their respiratory tract but had heavily contaminated udder skin. As a consequence, their newly adopted piglets rapidly became influenza positive. Field studies confirmed that adopted piglets are more likely to test influenza positive than those reared by their own dam. 

This is one more piece of the puzzle in trying to figure out how and when piglets become infected, taking us one step closer in the long path to influenza control.

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