CategoryPublic Health - Influenza
Date Full Report Received
Date Abstract Report Received
Influenza A is classified as a disease of major economic risk to US pork production due to the frequency of the outbreaks and high morbidity rate. After the 2009 pandemic of the H1N1 strain of influenza A virus (IAV), it is estimated that the pork industry lost over 1 billion dollars in revenue (6). Additionally, IAV is a zoonotic disease leading to public health concerns in swine handlers in intensive swine confinement operations. Hydrogen sulfide (H2S), a common stressor in such intense swine operations, is a known respiratory tract irritant that affects airways. Studies in rats have shown that H2S exposure increases bacterial retention in the respiratory tract, thus aggravating respiratory disease. However, hitherto, no studies have been conducted to investigate whether this gaseous stressor increases the severity of IAV infection in pigs.
The objective of this study was to identify the potential effects of low-level H2S exposure on IAV shedding and secondary respiratory infections in pigs. We hypothesized that low-level H2S exposure increases the severity of IAV infection. Thirty-five, 3-week-old crossbred pigs of mixed sex were randomly split into the following groups: Group 1 breathing air (BA)/non-challenged (NC); Group 2 exposed to BA/challenged with IAV (C); Group 3 exposed to 0.5 ppm H2S/C; Group 4 exposed to 5 ppm H2S/C, Group 5 exposed to 50 ppm/ NC; and Group 6 exposed to 50 ppm/C. Pigs were exposed for 6 hours each day, for 12 days total. After seven days, pigs were inoculated with approximately 3×105 TCID50 H3N2 IAV. Results demonstrated significantly increased body temperatures in Groups 3 and 6 compared to the BA/C group. H2S at 50 ppm with and without virus challenge had least weight gain compared to BA groups and groups receiving lower concentrations of H2S. Lung lesions were most severe in the 0.5 ppm/C and 50 ppm/C groups compared to the BA/C group. Pigs in the BA/non-challenge group did not manifest any fever or lung lesions. H2S exposure caused pigs challenged with IAV to shed the virus earlier, thus widening the window of viral shedding. The implication of this latter finding is that H2S may increase transmission of IAV in a swine herd. Overall, H2S exposure at any level increased the severity of disease in pigs challenged with IAV. These results indicate that even at the lowest level of H2S tested in this study, this environmental stressor aggravated IAV infection in pigs.