Abstract
Avian (AIV) and equine influenza virus (EIV) have been repeatedly shown to circulate among Mongolia’s migrating birds or domestic horses. In 2009, 439 Mongolian adults, many with occupational exposure to animals, were enrolled in a prospective cohort study of zoonotic influenza transmission. Sera were drawn upon enrollment and again at 12 and 24 months. Participants were contacted monthly for 24 months and queried regarding episodes of acute influenza-like illnesses (ILI). Cohort members confirmed to have acute influenza A infections, permitted respiratory swab collections which were studied with rRT-PCR for influenza A. Serologic assays were performed against equine, avian, and human influenza viruses. Over the 2 yrs of follow-up, 100 ILI investigations in the cohort were conducted. Thirty-six ILI cases (36%) were identified as influenza A infections by rRT-PCR; none yielded evidence for AIV or EIV. Serological examination of 12 mo and 24 mo annual sera revealed 37 participants had detectable antibody titers (≥1∶10) against studied viruses during the course of study follow-up: 21 against A/Equine/Mongolia/01/2008(H3N8); 4 against an avian A/Teal/Hong Kong/w3129(H6N1), 11 against an avian-like A/Hong Kong/1073/1999(H9N2), and 1 against an avian A/Migrating duck/Hong Kong/MPD268/2007(H10N4) virus. However, all such titers were <1∶80 and none were statistically associated with avian or horse exposures. A number of subjects had evidence of seroconversion to zoonotic viruses, but the 4-fold titer changes were again not associated with avian or horse exposures. As elevated antibodies against seasonal influenza viruses were high during the study period, it seems likely that cross-reacting antibodies against seasonal human influenza viruses were a cause of the low-level seroreactivity against AIV or EIV. Despite the presence of AIV and EIV circulating among wild birds and horses in Mongolia, there was little evidence of AIV or EIV infection in this prospective study of Mongolians with animal exposures.
Highlights
Among the world’s last pastoral people groups, Mongolians often live in close proximity with flocks of migrating birds or freeranging herds of horses
Because serologic responses to zoonotic influenza infections can rapidly wane [15], as we have reported previously [7,16,17,18], we chose a low threshold of antibody titer ($1:10) as evidence of previous infection with an avian influenza viruses (AIV) or equine influenza A virus (EIV) strain
One participant had an elevated titer (1:10) against A/Migratory duck/Hong Kong/MPD268/2007(H10N4) at 24 months. This subject experienced an influenza-like illnesses (ILI) the month prior to her 24 month visit, the respiratory swabs were negative for influenza A virus
Summary
Among the world’s last pastoral people groups, Mongolians often live in close proximity with flocks of migrating birds or freeranging herds of horses. Mongolia’s large migrating bird populations have been shown to harbor both highly-pathogenic and low-pathogenic avian influenza viruses (AIV) [1,2,3,4]. Having some of the highest horse-to-man population ratios in the world, Mongolia has suffered some of the world’s largest equine influenza A virus (EIV) epizootics [5]. In recent years H3N8 EIV epizootics occurred in 2007–2008 (96,390 cases; 24,600 deaths) and again in 2011 (75,208 cases; 40 deaths) (Mongolia’s Department of Veterinary and Animal Breeding). Knowing humans can experience AIV infections and H3N8 EIV has been experimentally shown to infect volunteers who were intranasally inoculated [6], we sought to prospectively study Mongolians for evidence of AIV and EIV infections
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
