PATHOGENS & PREVENTION ▶▶▶


More attention needed for swine influenza


Swine influenza is becoming more complex. The virus is also behaving more whimsically than ten years ago. That is why it is good to focus on the pathogen’s impact and to explore how to reduce the infection risk.


BY KEES VAN DOOREN, SENIOR REPORTER, BOERDERIJ A


Sampling ud- ders is also a way to deter- mine influenza infection as pig- lets can leave traces behind after drinking.


t an ever-growing number of pig farms, influenza is a problem that undermines animal health to a certain degree all year long. Not only is the virus behaving more whimsically, it is also more difficult


to control. There’s a plethora of reasons for that development.


Emergence of a pandemic type The emergence of a pandemic type A (H1N1) in 2009, origi- nating in Mexico, was pivotal. It joined the classical subtypes H1N1, H1N2 and H3N2. In short, that means that currently four subtypes of influenza are known in pigs, with the newest member of the family being a relatively pathogenic one. The latest addition has made influenza more difficult to con- trol. In every classical subtype of the virus there are eight gene segments, which can be exchanged completely for each other. At many farms, more than one subtype is present. When two subtypes infect the same pig cell simultaneously, they are capable of exchanging genetic material and, as a consequence, new subtypes are created. An example of such a newly formed subtype is H1pdmN2.


Swine farms are larger Another reason influenza has a larger impact than roughly ten years ago is that pig farms have grown larger in size. Because of continuous production, the virus can easily maintain its pres- ence on a farm. This applies mainly to the lactation and the grower phases, when maternal immunity slowly dwindles. Pig- let and grower areas therefore are often unintended virus res- ervoirs, comparable to a kindergarten for humans. The bottom line is that pig producers need to be alert for influ- enza, not only when winter is approaching, but year-round. Ac- cording to Van der Wolf, in the Netherlands for instance, influ- enza is present at 80% to 90% of pig farms. A growing number of pig farms is permanently infected with influenza, with more than one subtype involved, which is why various mixed varie- ties may show up. In addition, not everybody in the swine busi- ness is aware of the pandemic influenza variety from 2009, says Van der Wolf, which leads to underestimation.


Eight subtypes being found Ceva is conducting a lot of research at farms where there is a suspicion of influenza negatively impacting animal health. From January 2020 until mid-2021, at 116 pig farms in the Netherlands, eight new subtypes of influenza virus were demonstrated. In the recent quarter, an H3 type was also found in pigs; this originates from seasonal influenza with humans. When influenza occurs on its own, pig producers do not have to worry too much. Within a few days the pigs will have recovered from the virus. Things are different, however, if Actino bacillus pleuropneumoniae (App) is also present, or Por- cine Reproductive and Respiratory Syndrome virus (PRRSv) or when Mycoplasma hyopneumoniae (M. hyo) has just been around as well. M. hyo, for instance, causes damage to the cilia in the respira- tory tract, and these are key to blocking unwanted invaders like pathogens. After an M. hyo infection, the influenza virus is blocked less effectively, allowing the virus to protrude deeper


16 ▶ PIG PROGRESS | Volume 37, No. 10, 2021


With four subtypes of influenza in the pig industry, purely mathematically speaking it is possible to create many more varieties than with three. Peter van der Wolf, senior expert technical service swine at animal health company Ceva, ex- plains: “Since 2009, many more recombinations have become possible because the pandemic variety emerged.”


PHOTOS: RONALD HISSINK


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44