Threadworms (Strongyloides) in dogs

Threadworms are round worms just 2 mm long that live in the small intestines and infect both dogs and humans. The parasite is found in humid, subtropical regions such as the southeastern United States and Gulf Coast areas.

The life cycle of the threadworm is complex. Eggs and larvae are passed in the feces. Larvae become infective and are either ingested or gain entrance by directly penetrating the skin.

Threadworms are mainly a problem in puppies. Infected pups suffer from a profuse watery or bloody diarrhea that can be fatal. Pneumonia may occur as the larvae migrate through the lungs.

Treatment: The diagnosis is made by finding eggs or larvae on microscopic examination of stool, both fresh and after incubation. A five-day course of Panacur is the treatment of choice. Retreatment in 30 days is recommended. Ivermectin has also been used effectively, although it is not labeled for this purpose.

Public health considerations: Dogs can readily infect humans, and vice versa. Threadworm infection in humans is a debilitating disease accompanied by chronic diarrhea. Accordingly, infected pups must be isolated until treated and cured. Extreme care must be taken to avoid human contact with the feces of dogs infected with threadworms.