The course of swine influenza in pigs is reported to be similar to human influenza. Occasionally, abortions and other reproduction disorders have been associated with influenza A virus (IAV) infection in pigs, according to a paper published in BMC Veterinary Research.

Authors Krzysztof Kwit and colleagues at Poland's National Veterinary Research Institute explain that abortions may be a consequence of high fever, pro-inflammatory cytokines or transplacental transmission of the virus.

The role of IAV in the complications observed during pregnancy has been scanty and the true importance of this agent as a cause of reproductive problems in swine is not known.

The aim was of this work was to determine the possible involvement of swine H1N2 IAV strain on reproductive disorders in pregnant gilts under experimental conditions.

Gestation length was from 113 to 116 days, no abortion or any other reproduction disorders were noted.

A PCR assay confirms the presence of IAV in the nasal swabs taken from inoculated gilts between one and five days post infection. In the nasal swabs from control gilts and newborn piglets, no IAV genetic material was found. No viral RNA was detected in samples of blood taken from gilts and piglets, placentas, lungs and tracheas taken from piglets euthanized after delivery.

The significant decrease in the number and percentage of lymphocytes without leukopenia was observed at four days post infection in inoculated gilts. The percentage of granulocytes increased significantly at that time in inoculated pigs.

The concentration of IL-6, IL-10 and TNF-α were higher in inoculated gilts, while IL-4 and IFN-γ were not detected in the serum of any of animals.

Serum concentrations of C-reactive protein remained stable during study, while haptoglobin concentrations increased significantly after inoculation.

The results of the study indicate that infection of pregnant gilts with swine H1N2 IAV in the second month of pregnancy does not cause abortion and other reproduction disorders, concluded Kwit and colleagues. No evidence for transplacental transmission of swine H1N2 IAV was found.

However, they add, due to subclinical nature of influenza in this experiment, caution should be taken in extrapolating these results to the cases of acute influenza. The other limitation is IAV diversity; it cannot be excluded that other subtypes of IAV could be associated to reproduction failure in pigs.

Reference

Kwit K., M. Pomorska-Mól and I. Markowska-Daniel. 2104. The influence of experimental infection of gilts with swine H1N2 influenza A virus during the second month of gestation on the course of pregnancy, reproduction parameters and clinical status. BMC Veterinary Research. 10:123. doi:10.1186/1746-6148-10-123

June 2014