Horses are exposed to PHF by inadvertently ingesting aquatic insects infected with flukes carrying the bacteria and by drinking flukes directly from rivers or streams. | Photo: Photos.com

The Massachusetts Department of Agricultural Resources (MDAR) has confirmed two cases of Potomac horse fever (PHF)—one in Essex County and one in Norfolk County.

The Norfolk County horse, whose age, gender, breed, and vaccination status were not reported, presented on July 16 with clinical signs including being “off feed” and uncomfortable—signs generally associated with mild colic—followed by fever and diarrhea. Veterinarians diagnosed the horse with PHF the following day. The horse is reported to be recovering. Massachusetts’ single 2018 confirmed case and a suspect case ­occurred at the same stable.

The second horse, located at an Essex County boarding stable, presented to a referral hospital with signs of colitis (inflammation of the large or small colon). The horse subsequently developed fever and diarrhea but is responding to