Potomac Horse Fever Alert– Cases for 2015 thus far diagnosed at UKVDL in 2015

Jul 10, 2015


Potomac Horse Fever (PHF) has an acute onset, sometimes fatal enterotyphlocolitis of horses caused by Neorickettsia risticii, sometimes resulting in abortion. The N. risticii is found in flukes that parasitize freshwater snails. PHF has been diagnosed all around North America and is usually seen in horses older than one year. Common signs are depression, anorexia, high fever, ileus and severe watery diarrhea. In warm water, N. risticii are released from the snails, develop to metacerciariae in the secondary host, aquatic insects. Although not totally clear, these insects are likely the source of infection via ingestion of the insect by infested grass or water. A secondary portal of entry could be N. risticii by skin penetration via infected cercariae in the water. Risk factors include association with rivers, streams and other aquatic habitats and grazing pastures next to waterways.

As of 7/9/2015, UKVDL has received the following specimens that tested positive for Potomac Horse Fever (Neorickettsia risticii) by PCR. To confirm suspect cases, send 10 ml anti-coagulated blood (purple top, 10 ml minimum) AND feces or a fecal swab. The fee is $35 in-state/$52.50 out-of-state total for both samples. Turn-around is 1-2 working days—the test is run Mon through Fri.

We will continue to monitor the trends and alert you accordingly.

Please don’t submit feces in an OB sleeve—thanks for your cooperation!




DEBORAH WILLIAMS, DVM, Diagnostic Services

JACQUELINE SMITH, PhD, Epidemiologist

859-257-8283 (Office)