Normally only found in foals, the bacteria Lawsonia causes severe diarrhea, fever, and intestinal damage that causes a loss of protein into the intestinal tract. It has recently been noted in adult horses. The organism also causes infection in pigs and it was originally believed that a horse's exposure to pigs was the source of the infection. And although this is certainly possible, especially if there are large number of wild hogs in the area, recent isolates of Lawsonia have found the strain of the bacteria to be one that is common in rabbits and other animals rather than the strain commonly found in pigs. Regardless of the source, this can be a very serious disease in foals and can require intensive care treatment for survival. Blood testing and fecal testing can be helpful in making the diagnosis as well as ruling out other causes of diarrhea and infectious disease.

The disease usually responds to antibiotics but the major concern is the loss of protein and electrolytes due to diarrhea and the severe intestinal damage. For this reason, all cases of severe diarrhea should be examined by a veterinarian because most of these cases will require continuous intravenous fluids and sometimes even require that the horse be given fresh frozen plasma. Although plasma is expensive, it may be necessary to treat this disease as well as intensive care in a hospital to monitor fluid treatment. Getting the treatment started early will save you money in the long run, so if you have a foal or an adult horse with severe diarrhea, do not wait but contact your vet immediately.