Low Prevalence of Enzootic Equine Influenza Virus among Horses in Mongolia.

Alexandra Sack,Battsetseg Gonchigoo,Gregory Gray,Nyamdorj Tsogbadrakh,Ulziimaa Daramragchaa,Maitsetseg Chuluunbaatar,Boldbaatar Bazartseren

doi:10.3390/pathogens6040061

Abstract

Horses are critically important for Mongolian herders’ livelihoods, providing transportation and food products, and playing important cultural roles. Equine influenza virus (EIV) epizootics have been frequent among Mongolia’s horses, with five occurring since 1970. We sought to estimate the prevalence for EIV infection among horses and Bactrian camels with influenza-like illness between national epizootics. In 2016–2017, active surveillance for EIV was periodically performed in four aimags (provinces). Nasal swabs were collected from 680 horses and 131 camels. Seven of the horse swabs were “positive” for qRT-PCR evidence of influenza A (Ct value ≤ 38). Two more were “suspect positive” (Ct value > 38 and ≤ 40). These nine specimens were collected from four aimags. None of the camel specimens had molecular evidence of infection. Despite serial blind passage in Madin-Darby Canine Kidney cells (MDCK) cells, none of the nine horse specimens yielded an influenza A virus. None of the 131 herder households surveyed had recently vaccinated their horses against EIV. It seems likely that sporadic EIV is enzootic in multiple Mongolian aimags. This finding, the infrequent use of EIV vaccination, periodic prevalence of highly pathogenic avian influenza, and the mixing of domestic and wild equid herds suggest that Mongolia may be a hot spot for novel EIV emergence.

Highlights

Mongolia’s relationship with domestic horses (Equus ferus caballus) is unique, as horses play important roles in transportation, cultural events, and as a food source for many of Mongolia’s rural people
Seventy horses with signs of influenza-like illness (ILI) were tested during the Naadam festival from July 10–12, 2016 during six races
Equine influenza virus (EIV) surveillance is important in designing a strategy for reducing morbidity and mortality, as well as ameliorating any potential novel EIV emergence and zoonotic transmission

Summary

Introduction

Mongolia’s relationship with domestic horses (Equus ferus caballus) is unique, as horses play important roles in transportation, cultural events, and as a food source for many of Mongolia’s rural people. Mongolia is home to Mongolian wild asses (Equus hemionus hemionus), and the majority of the remaining wild Takhi or Przewalski’s horses (Equus ferus przewalskii) [5,6]. This large population and critical economic role of horses as well as the daily interactions during most of the year between humans and horses in Mongolia results in increased risk of infectious disease transmission. One disease with the potential to cause severe epidemics in equids as well as Pathogens 2017, 6, 61; doi:10.3390/pathogens6040061 www.mdpi.com/journal/pathogens

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