We’re here at the AAEP convention in San Antonio. We expected it to be sunny and warm, as it was 84 degrees only a few days before we arrived. But it’s pretty much just like it was in New England: Cloudy, dull, gray and cold. But never mind, the traditional Texas barbecue is yummy! Onto the issue at hand: Potomac Horse Fever.

To date it has been thought that snails & slugs (parasitized by trematodes) are the only vector for the transmission of Potomac Horse Fever (PHF). Therefore many forego vaccination for PHF because snails & slugs are not prevelant in their area (no water bodies, wetlands, etc.) In a recent study published at the AAEP, it was discovered that a large outbreak of PHF was due to the presence of mayflies. Infected, dessicated (dried up) mayflies blew into the stalls and the water and feed supply of the horses and caused infection.

The study found that in addition to snails & slugs, insects that accumulate around water bodies and wetlands–caddisflies, mayflies, dragonflies, etc.–can also transmit PHF. These insects are known to harbor the trematode parasite and when ingested by a horse can cause PHF infection. A worrisome thought is that the night lighting in our barns attracts these insects. The light attracts and may kill the insect, leaving a infected carcass that can be blown into the water and feed supply of the barn–and infect our horses.

This finding counsels additional caution surrounding the potential vectors of PHF transmission. An additional worriesome thought is that the infectious agent of PHF, trematodes, also live in the intestines of bats and barn swallows. Though not a proven vector of transmission, caution should also be taken with these animals in our barns. In general,these findings reinforce the recommendation of once to twice yearly vaccination for PHF.

This entry was posted on Sunday, December 3rd, 2006 at 8:59 pm. You can follow any responses to this entry through the RSS 2.0 feed. Responses are currently closed, but you can trackback from your own site.