Ask the Vet: Infectious Disease

Question: I have a beautiful Palomino Quarter horse gelding that I want to show. When I got him last year, they told me not to vaccinate him because he foundered two days after his last routine vaccines. That was back in 2008. He was in the same barn so it was not a problem. Now I own him and the barn that I want to go to, won’t let me board him without a flu/rhino vaccine. His previous veterinarian said no…don’t vaccinate him as it’s not worth the risk. Do you have any suggestions for me? Is there a vaccine that pinpoints herpes? Is there a more mild, for lack of a better word, type of vaccine that I could give? I don’t want to risk my horse’s life, but just thinking there must be someway to protect horses that have adverse reactions.

Answer: This is a very difficult, if not impossible, question to answer. My best advice is to request the specific vaccine type (manufacturer, vaccine trade name) from your horse’s previous veterinarian. The previous owner may need to authorize your acquisition of this information. Then discuss with your current veterinarian the options available for vaccination with different products. Each manufacturer uses a different adjuvent (a substance that is added to the vaccine to increase the body’s immune response to the vaccine). There are multiple vaccines available targeting herpes virus, both in combination with flu and alone. Ultimately, you and your regular veterinarian are best suited to determine the best preventive care program and living environment for your horse. I apologize that I cannot answer your question more specifically. 

Question: It’s the end of summer and in the 90’s with unusual humidity for California. To my frustration, my gelding has presented a fever of 104+/- and a snotty nose. My veterinarian suspects a virus. This horse has been on “bed” rest for the last month due to lameness. How the heck did he contact a virus with no other horses on the property or within nose contact?

Answer: Fever and nasal discharge may indeed be caused by viral infection, or by bacterial infection. Equine herpes virus lies dormant in clinically healthy horses until periods of stress, when it becomes re-activated, causing clinical disease. Another possibility in this case is that transmission occurred between a contaminated item, or even person, and your horse. In the early stages of viral infection, there may be no outward signs and thus transmission can occur by fomite (person or item) quite readily. Additionally, it can be difficult to distinguish viral from bacterial infections in the first few days of clinical disease. Viral infections typically resolve within a few days, while bacterial infections are often more prolonged.

Question: Can a horse that has had Potomac Horse Fever (PHF) make a complete recovery? Can they return to their prior job as if nothing has happened or will their performance ability be diminished?

Answer: Yes, a horse can recover completely from Potomac Horse Fever (PHF) and return to normal performance. Not all horses do recover to this degree. The severity of clinical signs is quite wide with PHF, and the development and severity of laminitis is often the limiting factor in future athletic endeavors.