The Missouri Department of Agriculture doesn't require cases of Potomac horse fever to be reported, and a spokesperson says it is not tracking information about the disease because it is only affecting a small area by the river.
However, the University of Missouri College of Veterinary Medicine in Columbia, Mo., has treated at least six cases of PHF already this summer and has been informed of at least a dozen more cases in the St. Louis area.
The disease is not common in the Midwest, as it's carried by snails, bats, flies and other vectors from wet areas. The disease, cause by Neorickettsia risticii, could be hitting Missouri as a result of recent flooding and a wet summer, says Dr. Philip Johnson, a veterinarian at the university.
PHF causes a bacterial infection in the large intestine of infected horses that can lead to colic, toxemia, laminitis and more. Untreated cases can be fatal. The disease can be treated with oxytetracycline, according to Johnson.
Potomac horse fever cannot be transmitted from horse to horse, to people or to other animals.