Tuesday, June 24, 2014

EID Journal: Equine H3N8 In Mongolian Bactrian Camel



Bactrian Camel – Credit Wikipedia


# 8777


Mongolia is home to recurring epizootic outbreaks of Equine H3N8 – an avian influenza that jumped to horses about a half century ago, and to dogs a decade ago -  among their horse populations (see Isolation and characterization of H3N8 equine influenza A virus associated with the 2011 epizootic in Mongolia)


These outbreaks, which occur roughly once a decade, not only impact the lives and economy of nomadic Mongolians, it has the potential of exposing other mammals to the virus.


While not as plentiful as horses, the Bactrian (two humped) camel is an important domesticated beast of burden for Mongolians, and as such is frequently exposed to both humans and horses.  It is also on the critically endangered list, and may even be extinct in the wild.


In the fall of 1979 a severe epizootic influenza broke out among Mongolian camels, which turned out to be a reassortant of the recently re-emerged (1977) H1N1 (aka `Russian flu) virus, showing that this species of camels was susceptible to at least some strains of influenza.


Virology. 1993 Dec;197(2):558-63.

A reassortant H1N1 influenza A virus caused fatal epizootics among camels in Mongolia.

Yamnikova SS1, Mandler J, Bekh-Ochir ZH, Dachtzeren P, Ludwig S, Lvov DK, Scholtissek C. 


In the autumn of 1979 a severe influenza epizootic started among camels in Mongolia (Lvov et al., 1982; Viprosi Virusol. 27, 401-405.) Between 1980 and 1983 13 independent isolates of H1N1 viruses were obtained from diseased camels, which were virtually indistinguishable from the human A/USSR/90/77 strain by serological means. Two hundred and seventy-one samples of camel sera collected between 1978 and 1983 contained antibodies against the human A/USSR/90/77 isolate. After experimental infection of camels with some of these isolates, the animals developed similar symptoms as those found during natural infection: coughing, bronchitis, fever, discharge from nose and eyes. A genetic sequence analysis revealed that among the eight segments (genes) the PB1, HA, and NA genes were almost identical with allelic genes of the USSR/77 strain, and the PB2, PA, NP, M, and NS genes were almost identical with those of the A/PR/8/34 strain.


Today the EID Journal carries a report on the detection of the Equine H3N8 influenza virus in a Mongolian Bactrian camel, likely acquired through exposure to infected horses.  First the link and some excerpts from the study, after which I’ll have a bit more:


Volume 20, Number 12—December 2014

Equine Influenza A(H3N8) Virus Isolated from Bactrian Camel, Mongolia

Myagmarsukh Yondon, Batsukh Zayat, Martha I. Nelson, Gary L. Heil, Benjamin D. Anderson, Xudong Lin, Rebecca A. Halpin, Pamela P. McKenzie, Sarah K. White, David E. Wentworth, and Gregory C. GrayComments to Author

Because little is known about the ecology of influenza viruses in camels, 460 nasal swab specimens were collected from healthy (no overt illness) Bactrian camels in Mongolia during 2012. One specimen was positive for influenza A virus (A/camel/Mongolia/335/2012[H3N8]), which is phylogenetically related to equine influenza A(H3N8) viruses and probably represents natural horse-to-camel transmission.


The phylogeny indicates that A/camel/Mongolia/335/2012 probably represents a relatively recent horse-to-camel transmission event. Without additional isolates from camels or corresponding epidemiologic data, and given the close genetic relationship between A/camel/Mongolia/335/2012 and related equine viruses, it is impossible to determine at this time whether the virus has been successfully transmitted from camel to camel.

In recent years, enhanced surveillance has detected influenza A viruses across a wider range of mammalian hosts, including horses, swine, dogs (14), seals (15), cats, and now camels, providing a more complete picture of the ecology of influenza A viruses beyond their presence in birds. How influenza A viruses successfully jump from 1 host species to another, and what the constraints on interspecies transmission are, remain key questions about influenza virus ecology and assessments of pandemic threats. Our findings highlight the need to further elucidate the ecology of influenza viruses and other pathogens in free-ranging camel populations.


As noted before, anytime an influenza virus jumps to a new host, we tend to take notice.  Influenza viruses as a rule are promiscuous, but until 2003 when it jumped to dogs, the H3N8 virus had only impacted birds and horses.


Last week, in Study: Dogs As Potential `Mixing Vessels’ For Influenza, we looked at a study that examined the susceptibility of canine tracheal cells to infection by canine, equine, and human influenza strains – including equine H3N8.


Any species that is susceptible to multiple, and diverse, flu strains has at least the potential to serve as a `mixing’ vessel for viral reassortment. Dogs, given their massive numbers and close contact with humans, are a far greater concern in this regard than Mongolian camels.


While the discovery of a single equine H3N8 virus among Bactrian camels may seem like an obscure, perhaps even insignificant bit of research, it reveals another piece of the influenza puzzle.


Learning how influenza viruses jump and adapt to new species – even among relatively small population of animals in a remote areas of the world – may very well lead to a better understanding of how the next pandemic (or epizootic) virus will emerge.