I did a little research recently to try and figure out why Potomac Horse Fever (PHF) was so prevalent in horses this year in Central Virginia. I went with my family on a float trip down the James River. We got our swimsuits and a cooler and hopped on the old school bus now relegated to taking sun-screened lathered tubers up from the James River Reeling and Rafting headquarters in Scottsville, VA to the Hatton’s Ferry up river. The river was big and broad and lazy, but it was also extremely clear. You could easily see the bottom. Now if you have been down the James River, you know that it can be very deep or very shallow, and very muddy or very clear. It depends on the rainfall. This summer has been a summer of sporadic rain. Isolated storms can bring heavy rain in one area and no rain in the next county. The first thing you notice as you float along and look at the bottom of the river is that it is covered, I mean COVERED with snails! About every three inches there is a small snail hanging onto the rocks, the leaves, the mud, the logs and sticks.
What does this have to do with Potomac Horse Fever? Well, snails carry the bacteria that cause PHF. So it would make sense that the more snails you have, the more bacteria in the water or anywhere there are snails. Fresh water snails and water insects harbor PHF. These snails are not only in a river or stream. They go wherever it stays wet. They are on grass in fields near fresh water sources and even under stall mats in your barn. They can be in a large water trough. The bacteria are ingested by your horse while grazing or drinking. The more bacteria ingested, the worse the sickness. If there are more bacteria around from the snails, there is going to be a much higher incidence of PHF. This year has been a very good year for snails and thus, for PHF.
PHF is a deadly diarrhea that can dehydrate a horse beyond help very quickly. It first causes a mild fever and loose stool. Depending on how much is ingested, it can be very minor and unnoticed or it can be a very rapid and fatal disease. It can cause founder and kidney failure. If PHF is caught very early and treated with Oxytetracycline intravenously, it will resolve. Vaccinated horses can still contract PHF, but they are much less likely to founder or die.
Maybe for my next research project I will go sky diving to check on the mosquitoes in the bird population in Central Virginia!