This article originally was published in the May 2017 issue of EQUUS magazine, a media partner of US Equestrian. 

Low doses of a common anticoagulant drug may help prevent a life-threatening neurological complication of equine herpesvirus type 1 (EHV-1) infection.

Typically, EHV-1 causes only mild clinical signs, but in outbreak situations, an estimated 33 percent of in­fected horses may develop equine herpesvirus myeloen­cephalopathy (EHM), which is characterized by damage of the blood vessels in the brain and spinal cord and ensuing neurological deficits.

Vaccines against EHV-1 infections are available, but they do not fully protect against the neurological form of the disease. “Some data are available on antivi­ral drugs, but mostly limited to the bioavailability of the compounds or on their effec­tiveness in cell culture,” says Jasmin Walter, DVM, DECAR, of the University of Zurich in Switzerland. “Proper ran­domized clinical studies are almost impossible to perform under natural outbreak con­ditions, which makes it hard to obtain scientific evidence for EHM prevention options.” Treatment of EHM is limited to anti-inflammatory medica­tion and supportive care.

Faced with these chal­lenges during an outbreak of EHV-1 at a large breeding facility in southern Germany in the spring of 2009, re­searchers and clinicians there decided to see whether the drug heparin would pre­vent EHM.

“The idea of using hepa­rin was brought up early during the outbreak by Kerstin Fey, DVM, DECEIM, an equine internal medi­cine specialist, and Klaus Osterrieder, DVM, PhD, who specializes on the virology side,” says Walter, who was the veterinarian in charge at the stud at the time.

Heparin is an anticoagu­lant used to treat diseases associated with abnormal or excessive blood-clotting, such as thrombosis, lami­nitis, or endotoxic shock. “EHM has a thromboisch­emic pathomechanism--meaning it causes blood to clot--which may be inhibited by anticoagulant drugs like heparin,” explains Walter. Furthermore, in cell culture experiments, heparin and re­lated substances are able to prevent virus entry into cells.

A total of 79 horses were kept in seven different barns at the German farm where the EHV-1 outbreak occurred, and 61 developed at least one clinical sign of infection--most often fever. In the early phase of the outbreak, 30 of the affected horses did not receive heparin, and these horses served as the con­trol group. Thirty-one horses were given heparin as soon as signs of illness appeared.

“I decided to use a very tentative treatment regime with low doses for a short, defined period to avoid possi­ble side effects,” says Walter. “Regular bloodwork in all the horses was not possible to check for critical conditions like anemia or thrombocyto­penia, which can arise under heparin medication.” Treated horses received subcutane­ous injections of 25,000 IU of heparin twice daily for three days. Horses with only a fever were given no other treatment; those exhibiting neurological signs received anti-inflammatory drugs, as well as antibiotics when nec­essary to prevent bladder in­fection due to paralysis.

When the outbreak ended nearly a month later, the re­searchers reviewed the re­cords of all the horses and found a distinct trend: only one of the horses treated with heparin developed EHM, while seven of the horses in the control group came down with neurological disease. The research­ers describe these results as “promising” and hope other clinicians try this approach when faced with an EHV-1 outbreak to collect more data.

“To my knowledge, no one else has tried this, but I hope our paper will encour­age equine clinicians and researchers to work on this topic,” says Walter.

Reference: “Prevention of equine herpesvirus myeloencephalopathy—Is heparin a novel option? A case report,” Tierärztliche Praxis Großtiere, October 2016

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This copyrighted article is not to be repurposed or used on any other website without permission from EQUUS magazine.

in the May 2017 issue of EQUUS magazine, a media partner of US Equestrian. 

Low doses of a common anticoagulant drug may help prevent a life-threatening neurological complication of equine herpesvirus type 1 (EHV-1) infection.

Typically, EHV-1 causes only mild clinical signs, but in outbreak situations, an estimated 33 percent of in­fected horses may develop equine herpesvirus myeloen­cephalopathy (EHM), which is characterized by damage of the blood vessels in the brain and spinal cord and ensuing neurological deficits.

Vaccines against EHV-1 infections are available, but they do not fully protect against the neurological form of the disease. “Some data are available on antivi­ral drugs, but mostly limited to the bioavailability of the compounds or on their effec­tiveness in cell culture,” says Jasmin Walter, DVM, DECAR, of the University of Zurich in Switzerland. “Proper ran­domized clinical studies are almost impossible to perform under natural outbreak con­ditions, which makes it hard to obtain scientific evidence for EHM prevention options.” Treatment of EHM is limited to anti-inflammatory medica­tion and supportive care.

Faced with these chal­lenges during an outbreak of EHV-1 at a large breeding facility in southern Germany in the spring of 2009, re­searchers and clinicians there decided to see whether the drug heparin would pre­vent EHM.

“The idea of using hepa­rin was brought up early during the outbreak by Kerstin Fey, DVM, DECEIM, an equine internal medi­cine specialist, and Klaus Osterrieder, DVM, PhD, who specializes on the virology side,” says Walter, who was the veterinarian in charge at the stud at the time.

Heparin is an anticoagu­lant used to treat diseases associated with abnormal or excessive blood-clotting, such as thrombosis, lami­nitis, or endotoxic shock. “EHM has a thromboisch­emic pathomechanism--meaning it causes blood to clot--which may be inhibited by anticoagulant drugs like heparin,” explains Walter. Furthermore, in cell culture experiments, heparin and re­lated substances are able to prevent virus entry into cells.

A total of 79 horses were kept in seven different barns at the German farm where the EHV-1 outbreak occurred, and 61 developed at least one clinical sign of infection--most often fever. In the early phase of the outbreak, 30 of the affected horses did not receive heparin, and these horses served as the con­trol group. Thirty-one horses were given heparin as soon as signs of illness appeared.

“I decided to use a very tentative treatment regime with low doses for a short, defined period to avoid possi­ble side effects,” says Walter. “Regular bloodwork in all the horses was not possible to check for critical conditions like anemia or thrombocyto­penia, which can arise under heparin medication.” Treated horses received subcutane­ous injections of 25,000 IU of heparin twice daily for three days. Horses with only a fever were given no other treatment; those exhibiting neurological signs received anti-inflammatory drugs, as well as antibiotics when nec­essary to prevent bladder in­fection due to paralysis.

When the outbreak ended nearly a month later, the re­searchers reviewed the re­cords of all the horses and found a distinct trend: only one of the horses treated with heparin developed EHM, while seven of the horses in the control group came down with neurological disease. The research­ers describe these results as “promising” and hope other clinicians try this approach when faced with an EHV-1 outbreak to collect more data.

“To my knowledge, no one else has tried this, but I hope our paper will encour­age equine clinicians and researchers to work on this topic,” says Walter.

Reference: “Prevention of equine herpesvirus myeloencephalopathy—Is heparin a novel option? A case report,” Tierärztliche Praxis Großtiere, October 2016

Want articles like this delivered to your inbox every week? Sign up to receive the Equestrian Weekly newsletter here.

This copyrighted article is not to be repurposed or used on any other website without permission from EQUUS magazine.