Nematode Zoonoses - ANCYLOSTOMIASIS

(Uncinariasis, Necatoriasis, Hookworm Disease)

AGENT:

The causative agents are mainly Necator americanus and Ancylostoma duodenale; occasionally A. ceylanicum and A. caninum.

RESERVOIR AND INCIDENCE:

A common worm infection of humans and domestic dogs and cats in various tropical and subtropical countries where disposal of human feces is inadequate. The reservoirs are humans, dogs, and cats.

TRANSMISSION:

Adult worms, living in the small intestines of humans, produce eggs which pass on to the ground in feces. The eggs hatch and go through three larval stages. Human infection results from the third-stage larvae which survive in soil for several weeks in moist and warm conditions. Animals and man become infected by contact with infected soil, the larvae penetrating through skin or mucosa of the digestive tract. The parasites then migrate through the blood capillaries to the lung, eventually to be coughed up and swallowed. They reach maturity and complete their cycle in the intestines.

DISEASE IN ANIMALS:

Factors such as the weight of infection and nutritional state of the animal are important. Loss of blood together with malnutrition produce anemia. Severe enteritis causes hemorrhagic diarrhea and weight loss from intestinal malabsorption. Prenatal infection of the dog causes death of the fetal pups. Mild infections generally cause no clinical signs.

DISEASE IN MAN:

The condition is often asymptomatic. Self-limiting vesicular/pustular skin eruptions may appear at the site of larval entry. A. caninum does not penetrate human skin beyond the epidermis. With other species chronic symptoms due to iron deficiency anemia may occur. Rarely there is tracheitis and coughing due to lung infiltration with parasites.

DIAGNOSIS:

Fecal flotation.

TREATMENT:

Pyrantel pamoate, mebendazole, albendazole, levamisole, or tetrachloroethylene.

PREVENTION/CONTROL:

Educate the public to the dangers of soil contamination by feces. Wear shoes! Screen feces from persons and animals from endemic areas. Keep kennel floors dry and avoid feeding animals on the ground.