Equine Herpesvirus Research
Can airborne viruses survive in water?
by Fran Jurga
April 21, 2017
We obsess over the how-and-why-and-when-and-where transmission of equine herpesvirus between horses. The highly contagious and sometimes deadly virus can endanger horses’ lives by contaminating a horse show stall, a trailer, a vet clinic exam station or even just a groom’s jacket. It can travel through a racing stable, as it did in France last week, and a horse can bring it home from a show to sicken horses that never even left the property.
An outbreak of even routine equine herpesvirus brings the horse world to a screeching halt, shuts down horse shows, closes racetracks and sometimes even stops the interstate movement of horses.
One hundred years ago, city government workers in the United States took sledge hammers to public water troughs for fear that they were transmission pools for equine diseases, especially glanders. Many veterinarians challenged the closures, saying that watering horses with buckets was inefficient and equally disease-friendly. But it was too late: the troughs’ pipes were smashed, and the lack of water for city work horses became another reason for businesses to convert to motor freight delivery.
Virus outbreaks in zoos have inspired new research to protect captive animals, and we can now look to a triad of domestic, wild and captive living laboratories where equine herpesvirus “research” can be done, and data collected.
A new study challenges the tenet that herpes viruses, like most enveloped viruses, are relatively unstable outside their host. Under a variety of conditions, equine herpesvirus remained stable and infectious over a three-week period. This suggests that untreated water could be a source of infection by some herpesviruses. The results are reported today under Open Access in the journal Scientific Reports.
Enveloped viruses such as herpesviruses can cause disease when spread from host to host by aerosol transmission. They are generally thought to be unstable in the environment, requiring rapid and direct transfer among hosts in order to ‘survive’ and remain infectious. Recently, a research team lead by scientists from Germany’s Leibniz Institute for Zoo and Wildlife Research, in collaboration with the Institut für Virologie of the Freie Universität Berlin, tested this assumption by spiking water with equine herpesviruses under different conditions over a three-week period.
They then examined whether viral DNA could be retrieved and to what extent the virus remained infectious after having been in the water.
The results demonstrate that the virus does remain stable and infectious for up to three weeks, with pH and temperature being the two most important factors to determine how long the virus survived. Surprisingly, the addition of soil to the water appeared to “pull” the virus out of the water and stabilize it in the soil, suggesting that in natural water bodies, viruses may persist for an extended time without infecting additional hosts.
Therefore, in the case of equine herpesviruses, horses or other mammals susceptible to these viruses could be infected by herpesviruses from water bodies long after the animals that shed the virus had left the area.
These results suggest that viruses such as equine herpesviruses may become a part of the environmental “virome” and remain infectious. Equine herpesviruses have spread among mammals such as polar bears and rhinos without direct contact with horses or their relatives in both the wild and in captivity, often resulting in fatal consequences. Shared water sources may be a source and potential vector for infection.
Note: The authors state that further research is necessary to establish whether their laboratory results reflect virus biology in environmental samples.
This work is part of the ongoing project AquaVir (“Water as an aquatic viral vector for emerging infectious diseases”) funded by the Leibniz Society Intramural Competitive Fund and the Leibniz Research Alliance INFECTIONS’21. The research is licensed under a Creative Commons Attribution 4.0 International License.
Click here to read and download the entire paper on the publisher’s website.
Citation:
Dayaram A, Franz M, Schattschneider A, Damiani AM, Bischofberger S, Osterrieder N, Greenwood AD (2017): Long term stability and infectivity of herpesviruses in water. Scientific Reports. Published online April 21, 2017.
www.nature.com/articles/srep46559
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