Submitted to: Research Conference on Orthomyxoviruses
Publication Type: Abstract Only
Publication Acceptance Date: 7/1/2007
Publication Date: 9/21/2007
Citation: Lipatov, A.S., Kwon, Y., Lager, K.M., Suarez, D.L., Swayne, D.E. 2007. Pathogenesis of avian influenza A (H5N1) viruses in pigs [abstract]. In: Proceedings of the Research Conference on Orthomyxoviruses, September 21-24, 2007, Woods Hole, Massachusetts. p. 26.
Technical Abstract: Background. Genetic reassortment of avian influenza H5N1 viruses with currently circulating human influenza A strains is one possibility that could lead to efficient human-to-human transmissibility. Domestic pigs which are susceptible to infection with both human and avian influenza A viruses are one of the natural hosts where such reassortment events could occur. To begin to study this possibility we characterized the pathogenesis of H5N1 influenza in a pig model. Methods. 3-week-old male domestic pigs (PIC 1050's, a cross between a Land Race x Large White Cross) were used in the experiments. Groups of 4 animals were intranasally inoculated with 10 6 EID50 of A/Vietnam/1203/04 (VN/04) or A/Muscovy duck/ Vietnam/209/06 (Dk/VN/06) viruses. Pigs were observed daily and 2 pigs from each group were euthanized on day 5 and day 14 after virus inoculation to collect organ samples. Body weight of infected pigs was measured daily; nasal and rectal swabs for virus detection were collected on days 1, 3, 5, 7, 9, and 11. Results. Inoculation of pigs with both H5N1 viruses did not result in disease with visible clinical signs or significant weight loss. VN/04 virus was detected in nasal swabs of inoculated pigs on days 1 (2 animals, titers 10 1.5 EID50 and 10 2.25 EID50/1.0 ml of collection fluid), 3 (1 pig, titer 10 2.25 EID50) and 5 (1 pig, titer 10 3.75 EID50). Dk/VN/06 virus was not detected in nasal or rectal swabs. VN/04 virus was not detected in any of organs samples collected on day 5. Dk/VN/06 virus was isolated from lungs of 1 pig (titer 10 5.75 EID50/g) and nasal turbinate of another animal (titer 10 2.5 EID50/g). Histological examination revealed lobular lymphocytic bronchopneumonia and focal alveolitis in the lungs of pigs infected with both H5N1 viruses. Conclusions. Pigs had limited susceptibility to infection with avian influenza H5N1 viruses. Inoculation of pigs with VN/04 and Dk/VN/06 viruses resulted in asymptomatic infection restricted only to the respiratory tract in contrast to mouse and ferrets animal models, where these viruses are highly pathogenic and replicate systemically.