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Monitoring influenza A virus in a breeding herd

Which sample type should we test?

October 23, 2023

2 Min Read
National Pork Board

By Daniel Moraes, Phillip Gauger, Cesar Moura, Isadora Machado, Guilherme Cezar, Onyekachuco Osemeke, Rodrigo Paiva, Mafalda Mil-Homens, Gustavo Silva and Daniel Linhares, Iowa State University and Alex Ramirez, The University of Arizona.

Defining the sampling plan to detect influenza A virus depends on the diagnostic sensitivity of the sample type and the convenience of sample collection. This study compared different sample types on the probability of IAV RNA detection in swine breeding herds.

Three breeding herds were screened with pigs in the farrowing room at weaning age (17-21 days) using udder wipes to ensure evidence of IAV circulation before sample collection of FOF within 48 hours of screening. Eligible herds had at least 15% (6/35) of udder wipes testing positive.

Samples were collected from three rooms (A, B, C) at the selected breeding herd (n=3,500 sows) using 57 matched sets of family oral fluids, udder wipes, nasal wipes from sows, individual nasal wipes of suckling piglets (as a reference sample type), and sow drinker wipes.

Major findings and implications

  1. Using piglet nasal wipes as the reference, FOF and udder wipes showed higher IAV detection, and they can be used according to the veterinarian and producer’s decision based on the expected within litter prevalence scenarios.

  2. FOF were an effective population specimen for IAV detection in the weaning-age litter, as compared to piglet nasal wipes. It had higher PCR positivity and lower Ct values than udder wipes and sow nasal wipes.

  3. The proportion of positive piglets within litter differed significantly by room, ranging from 8 to 100% within farrowing stalls and 9 to 91% within rooms.

  4. Sample collection for IAV monitoring should be conducted in different rooms (rooms A, B, C), as there may be significant differences in prevalence.

  5. Sample type should be considered in the breeding herd depending on the prevalence of IAV. FOF presented the highest probability of IAV detection, especially in scenarios of within litter prevalence lower than 25%.

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