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Effects of low litter birth weight on the pathogenesis of influenza A virus following experimental infection



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A fetus’ in utero environment has a profound effect on the individual’s development in postnatal life. Research has suggested that intrauterine growth restricted children have a less robust response to vaccination. Studies have confirmed similar results in animal models; however, the effect of low birth weight on clinical disease expression is unclear. This research aims to determine if pigs from low birth weight litters have increased severity of disease after experimental infection with influenza A virus (IAV) when compared to their counterparts from high birth weight litters, thus clarifying the effect of litter birth weight on disease expression. Pilot trials were conducted to determine the appropriate dose of virus to use and the optimal days post inoculation for necropsy to use for the main trial. The results indicated that the main trial should use an inoculation dose of 1 x 107 plaque forming units of IAV and the time of necropsy should be 48 hours post inoculation. In the main trial, male piglets (n=68) from parity one or two sows were identified at farrowing as coming from high or low birth weight litters. At four weeks of age, intratracheal IAV inoculation was performed (day 0) and pigs were euthanized at 48 hours post inoculation. Clinical signs were assessed prior to euthanasia. After euthanasia macroscopic and microscopic lesion severity were assessed, along with immunohistochemical staining intensity of IAV in lung tissue. SearchLight Chemiluminescent Array Technology was used to measure the concentration of the inflammatory cytokines interleukin 1 beta, interleukin 6, and interleukin 8 in bronchoalveolar lavage fluid. Interferon alpha was measured using fluorescent microsphere immunoassay. Fifty Percent Tissue Culture Infective Dose was used to measure influenza viral titers in lung tissue. The study found no differences in clinical scores or cytokine concentration between pigs from high and low birth weight litters. Gross, histopathological and immunohistochemical scores were significantly higher in piglets from high birth weight litters and viral titers trended higher in these piglets. These findings indicate that pathologic disease scores in piglets experimentally inoculated with IAV are more severe in piglets from high birth weight litters.



prenatal programming, swine, influenza A virus, birth weight



Master of Science (M.Sc.)


Large Animal Clinical Sciences


Large Animal Clinical Sciences


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