Haitian Child

Haitian Child

Friday, November 29, 2013

Worms in Nicaragua

Worms in Nicaragua

Worm disease is common in Nicaragua. One study showed Ascaris infection in 13% of individuals.

Worms are present worldwide in the moist warm soil found in the tropical latitudes. There are three common worms, Ascaris lumbricoides, Trichuris trichiura (whipworm), and Anclostoma duodenale & Necator americanus (hookworm).
 Ascaris eggs on R & L. Adult female in center. Images courtesy CDC.

Ascaris live in the lumen of the small intestine. A female can produce approximately 200,000 eggs per day, which are passed with the feces. Fertile eggs are infective after 18 days to several weeks, depending on the environmental conditions. After infective eggs are swallowed, the larvae hatch, invade the intestinal mucosa, and are carried via the blood to the lungs. The larvae mature further in the lungs (10 to 14 days), penetrate the alveolar walls, ascend the bronchial tree to the throat, and are swallowed. Upon reaching the small intestine, they develop into adult worms. Between 2 and 3 months are required from ingestion of the infective eggs to oviposition by the adult female. Adult worms can live 1 to 2 years.
Hookworm larva. Images courtesy CDC.

Hookworm eggs are passed in the stool, and the 
larvae hatch in 1 to 2 days. The larvae are infective after 5 to 10 days, and can survive 3 to 4 weeks. On contact with the human host (bare feet), the larvae penetrate the skin and are carried through the blood vessels to the heart and then to the lungs. They penetrate into the pulmonary alveoli, ascend the bronchial tree to the pharynx, and are swallowed. The larvae reach the small intestine, where they mature into adults. Adult worms attach to the intestinal wall with resultant blood loss. Most adult worms are eliminated within 1 to 2 years.
Whipworm eggs on R & L. Adult female in center. Images courtesy CDC.

Whipworm eggs are passed in the stool, and the eggs are infective in 15 to 30 days. The eggs hatch in the small intestine and release larvae that mature and migrate to the colon. Female worms in the cecum shed between 3,000 and 20,000 eggs per day. The lifespan of an adult is about 1 year.

Once infected with a worm, a child can develop abdominal pain and distension, intestinal obstruction, iron-deficiency anemia, malnutrition and poor growth, and allergic reactions.

Mebendazole kills the worms. Mebendazole is on the World Health Organization (WHO) List of Essential Medicines for Children, and is intended for the use in children up to 12 years of age. There is limited data on the safety in children under the age of 2 years. In Nicaragua, a government program is in place to administer the medication. Each school-aged child receives a 500 mg dose of mebendazole. Reinfection is common, so the medication needs to be re-administered. 

Prevention is preferable to regular re-administration of the medication. 
The fundamentals of prevention for all worms include access to clean water, modern sanitation to dispose of infected feces, good personal hygiene with regular hand washing, and careful cleansing of soil-grown-vegetables and fruits.

To prevent hookworm infection, individuals should not walk barefoot in the soil and should otherwise avoid skin contact with soil.

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