Signs & Symptoms - Internal Parasites

Symptoms of worm parasitisms may be confused with symptoms of’ bacterial, viral, or other disease organisms so the use of fecal samples is valuable to aid the veterinarian in diagnosing the presence of worms. Especially in young animals the following symptoms may be observed when many worms are present:

1. Unthriftiness. The colt grows slowly or older horses fail to maintain normal weight.

2. Rough coat. Hair appears to lie in an abnormal position, is variable in oiliness and seems to “stand up” even with relatively short coats during the summer.

3. Anemia. Membranes of the eyes, lips, nostrils, and tongue are a lighter pink than in uninfected horses. Hematocrit (number of red blood cells per unit of blood) values may be below normal and there may be less hemoglobin in blood than normal. Anemia also may be caused by many bacterial or viral organisms as well as nutritional deficiencies.

4. Diarrhea. While this condition is highly variable it can be of diagnostic value in some horses at some stage of worm infection. However, it must be noted that some worms cause constipation for short periods in some horses.

5. Abnormal appetites. Horses may eat articles such as paper, matted hair, bark of trees and gnaw on wooden articles such as posts, trees, neck yokes and leather trappings. Sometimes this condition can be traced to mineral deficiencies, internal parasites or lack of total nutrients. Mineral and vitamin deficiencies could act with worm parasites to the disadvantage of the horse.

6. “Potbellied” condition. Ascarid worms, with or without the presence of stronglid worms, frequently cause abnormally large abdominal girth, some muscle weakness and poor growth, especially in the case of colts.

While symptoms are helpful in diagnosing worm problems in horses, perhaps the better way to determine kinds of worms is to have a reliable laboratory or a local veterinarian make fecal analyses.