12/30/2023
As many of you may have heard, Dr. Sara and Dr. Derek recently diagnosed a horse with Potomac Horse Fever (PHF) in West Newbury. This disease is caused by a bacterial infection (Neorickettsia risticii) and can result in high fever, diarrhea, and laminitis. PHF is not very common in our area, but the extra rain this summer may temporarily increase the risk of infection. PHF is not contagious from horse to horse. The life cycle is complicated (see diagram), but the important part is that horses get infected by drinking water that contains larvae of aquatic insects such as the caddisfly, mayfly, and dragonfly.
What can you do to protect your horse?
1. Ensure access to fresh, clean water. Change water troughs daily and turn barn lights off at night, as this can attract insects.
2. Avoid pastures that are adjacent to bodies of water such as ponds, swamps, or streams. This is especially important in mid to late summer.
3. There is a vaccine available for PHF in horses. It is important to note that the efficacy of this vaccine is somewhat limited because there are large strain variations of the N. risticii bacteria and the vaccine does not protect against all strains. Nevertheless, we do recommend vaccinating horses at high risk of infection, such as horses in areas with recent cases or on farms near bodies of water.
Here is a good resource with further information for any that are interested:
https://www.merckvetmanual.com/digestive-system/infectious-diarrheal-diseases-in-horses/potomac-horse-fever
Please feel free to contact our office by phone or email if you have further questions or would like to schedule an appointment. Thank you, -Dr. Derek and Dr. Sara
Figure citation: Adv Parasitol. 2012;79:253-97
