Nematode Zoonoses - TRICHOSTRONGYLOSIS

(Trichostrongyliasis, Trichostrongylosis)

AGENT:

Several species of Trichostrongylus including Trichostrongylus axei, T. affinis, T. colubriformis, and many others.

RESERVOIRS AND INCIDENCE:

The reservoirs of most of the species of Trichostrongylus are domestic and wild herbivores. Trichostrongylids are very common parasites in domestic ruminants and their distribution is worldwide.

TRANSMISSION:

The sources of infection are soil and vegetation, in which the eggs deposited with the animal host's feces develop in a few days to the infective larval stage. Man and animals are infected orally. Man acquires the infection mainly by consuming raw vegetables contaminated with the infective larvae. Another important factor in transmission is the preparation and use of animal manure as fuel.

DISEASE IN ANIMALS:

In horses, these worms produce a chronic catarrhal gastritis and may result in weight loss. The lesions comprise nodular areas of thickened mucosa surrounded by a zone of congestion and covered with a variable amount of mucus. The lesions may be rather small and irregularly circumscribed, or may coalesce and involve most or all of the glandular portion of the stomach, and erosions and ulcerations may be seen. In ruminants, gastritis with superficial erosion of the mucosa, hyperemia, and diarrhea may result. Protein loss from the damaged mucosa and anorexia cause hypoproteinemia and weight loss.

DISEASE IN MAN:

Most cases asymptomatic. Severe infections - diarrhea, blood in stool, abdominal cramps, and emaciation.

DIAGNOSIS:

Flotation and fecal culture (identification of larvae used to distinguish between species).

TREATMENT:

Pyrantel pamoate, mebendazole, or levamisole.

PREVENTION/CONTROL:

Regular deworming of animals. Preventive measures for humans consist of improved food, environmental, and personal hygiene. In endemic areas, raw vegetables or other foods should not be eaten. Pasture management is important. Most of the larvae die in a field left ungrazed for a month.