IN­FLUENZA VIRUS IS ZOONOTIC

EQUUS - - Eq Medicalfro­nt -

sus­tain­ing the trans­mis­sion of these viruses in horses by serv­ing as si­lent vec­tors,” says Gray. “That means they are har­bor­ing the virus them­selves and pass­ing it along to other horses. This isn’t a case of the virus be­ing on their hands and passed through con­tact, but hu­mans that are in­fected and shed­ding it in their own nasal se­cre­tions to in­fect horses. We haven’t found such ev­i­dence, but it’s bi­o­log­i­cally be­liev­able based on the his­tor­i­cal ev­i­dence we’ve looked at.”

Gray notes that the biose­cu­rity mea­sures and hy­giene prac­tices com­mon in the Western world min­i­mize the threat of the EIV pass­ing be­tween peo­ple and horses. Else­where, how­ever, the risk is greater. “In a place like Mon­go­lia or China, where one care­taker may be look­ing af­ter a large herd of work­ing horses, a sick horse or hu­man may go un­no­ticed. That’s where you have some po­ten­tial of a prob­lem.” He adds that if the equine in­fluenza virus were to change or if a dif­fer­ent strain were to emerge, the sce­nario could change dras­ti­cally.

“Mod­ern H3N8 strains of in­fluenza in horses are mild and fairly sta­ble, but there are some strains ---such as H7N7---that cir­cu­lated 30 or 40 years ago and have dis­ap­peared,” says Gray. “If they were to come back, the hu­man pop­u­la­tion wouldn’t haven’t the par­tial re­sis­tance we do have to the H3N8 strain and there would likely be a greater prob­a­bil­ity that it would in­fect hu­mans. That’s when you can de­velop an out­break sit­u­a­tion like we’ve seen with a num­ber of hu­mans be­com­ing sick with var­i­ous type of avian in­fluenza viruses.”

For­tu­nately, says Gray, “there are ve­teri­nar­i­ans ded­i­cated to this study in var­i­ous parts of the world, closely mon­i­tor­ing for out­breaks in horses and the emer­gence of new strains. If that hap­pens we don’t know how big of a prob­lem it will be, but we will likely soon be­come aware of it and start tak­ing steps to con­tain it.”

As for what in­di­vid­ual horse own­ers can do to pro­tect them­selves and their horses against in­fluenza, Gray rec­om­mends fol­low­ing the vac­ci­na­tion ad­vice of ve­teri­nar­i­ans and doc­tors: “If your doc­tor sug­gests an in­fluenza vac­cine, get it. In most years, the hu­man ver­sion will give you some pro­tec­tion from equine vari­ants be­cause they both con­tain some sim­i­lar com­po­nents. And by the same to­ken, if your vet­eri­nar­ian rec­om­mends in­fluenza vac­cines for your horses, take that ad­vice.”

Biose­cu­rity mea­sures and hy­giene prac­tices com­mon in the Western world min­i­mize the threat of EIV pass­ing be­tween peo­ple and horses. Else­where, how­ever, the risk is greater.

Ref­er­ence: “A re­view of ev­i­dence that equine in­fluenza viruses are zoonotic,” Pathogens, July 2016

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