Procedures to eliminate H3N2 swine influenza virus from a pig herd

Abstract

A three-site pig herd infected with a H3N2 swine influenza virus (SIV) underwent a herd SIV elimination programme using herd closure and partial depopulation. The herd consisted of sow, nursery and finishing units, 1 to 2 km apart. Disease was noted in the sow unit and then the nursery unit. The herd temporarily stopped introduction of replacement animals, and replacement gilt introductions in the breeding herd was changed from monthly to quarterly. Gilts from a serologically negative source were also introduced and monitored. Virus elimination from growing pigs was attempted by totally depopulating the nursery and finishing sites once there was evidence that shedding in site 1 had stopped. Sentinel gilts remained serologically negative by haemagglutination inhibition (HI) test (0 of 69 animals negative) for at least 20 months after the initial disease. After restoring the pig flow in site 2, pigs did not experience flu-like clinical signs and HI serology results remained negative (0 of 30 animals tested) for the six months following repopulation of sites 2 and 3. In addition, nursery mortality was improved by 2.2 per cent, the growth rate was improved by 0.123 kg/day and feed efficiency was improved 0.26 points. Based on these results, SIV elimination was considered successful.

The first identified case of pandemic H1N1 influenza in pigs in Australia

“…21 Influenza H1N1/09 is now considered endemic in the Australian human population. Cross-sectional serology conducted 6 weeks earlier suggested that almost all pigs had circulating antibodies against H1N1/09 influenza virus.…”

“…20 Although there are published reports of influenza virus eradication from pig herds, these are rare. 21,22 An H3N2 strain of swine influenza was eradicated from a three-site pig herd using herd closure and nursery depopulation. 21 Elimination of the virus was deemed to have happened as part of the natural course of infection, with the virus eliminated when susceptible animals were no longer available for it to replicate.…”

“…21,22 An H3N2 strain of swine influenza was eradicated from a three-site pig herd using herd closure and nursery depopulation. 21 Elimination of the virus was deemed to have happened as part of the natural course of infection, with the virus eliminated when susceptible animals were no longer available for it to replicate. 2 The results of our longitudinal study suggest that maternally-derived antibodies partially prevented infection and seroconversion in suckling pigs until weaning at 3-4 weeks of age.…”

“…Herd closure is a recommended strategy to assist with influenza eradication in pig herds. 21 Influenza H1N1/09 is now considered endemic in the Australian human population. We report the first spill-over of this virus into pigs in Australia.…”

Diagnostics and Surveillance for Swine Influenza

“…Surveillance design parameters depend on the objectives of the surveillance program as outlined previously. For example, surveillance parameters would be different if the objective is to identify the most prevalent influenza virus subtypes in pigs in a particular region versus whether influenza virus has been eliminated from a specific swine herd (Torremorell et al 2009). Designing a surveillance program also requires a thorough understanding of the behavior of the virus in pigs, available diagnostic tests, and the production practices used for raising pigs that are to be monitored.…”