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The aim of this study was to evaluate influenza vaccination in pigs as a means to reduce aerosolization of virus and subsequent airborne spread.
Thirty-six, three-week old weaned pigs were obtained from an influenza seronegative herd. Pigs were vaccinated at 3 and 5 weeks of age using 4 different treatments: a) an autogenous vaccine (HOM), b) a commercially available monovalent vaccine (MON), c) a commercially available multivalent vaccine (MULTI) and d) saline solution (CRTL). The commercial vaccines were considered heterologous to the challenge virus based on HA sequencing (sequence homology <95%) and they included pandemic H1N1 virus (MON group) or H1N1, H1N2 and H3N2 strains (HET group). The autogenous vaccine was prepared using the challenge virus A/ Sw/IA/00239/04 H1N1 strain. Pigs were inoculated intratracheally and intranasally two weeks after the second vaccination was completed. Pigs were tested daily using nasal swabs and assayed by qRT-PCR. Oral fluids and air samples were also collected three times a day and tested by qRT-PCR and virus isolation.
Individual nasal PCR results indicated that all pigs in the control group and all pigs but one in the HET- MULTI group were influenza positive. In the HET-MON group 5 out of 9 pigs became positive and only one pig was positive in the HOM group. No positive air samples were detected in the vaccinated groups. However, in the CONTROL group, positive air samples were detected at DPI 2, 3 and 4 by qRT-PCR. However, virus was not isolated from these samples. Average temperature and relative humidity among rooms was 28°C (24°-33°) and 53% (36%-75%), respectively.
In this study, influenza virus detection in pigs and air samples was reduced through vaccination. However, overall virus detection in air samples in the non-vaccinated pigs was limited. This may be explained by the increased room temperature and humidity observed. Nevertheless, influenza virus was detected in aerosols generated in hot and humid conditions. More studies are needed to further assess vaccination as a means to decrease the risk of influenza airborne transmission under field conditions.
Victor Neira, Cesar Corzo, Matt Allerson, Marie Gramer, Montse Torremorell. Effect of influenza vaccination on influenza bioaerosol generation. Proceedings 2013 AASV Annual Meeting.