Ascariasis is caused by Ascaris lumbricoides, it is the most widespread parasitic worm infections worldwide. It also causes the most trouble in the human host when compared to other roundworm infections. Ascariasis can be transmitted through many means, all of which are generally contaminated with feces. Soil, water, and food that have come into contact with the infected feces all become a means of transmission for the virulent eggs.(1) Soil touched by hand and then to mouth or fresh food grow in infected soil that has not been properly washed can both be means of transmission. Water is a means of transmission generally in areas with poor sanitation techniques.(2) Ascariasis has numerous reservoirs, which include; animals, humans, and soil.
Ascariasis eggs are very resilient and can survive in soil for years.(3) A key test used for the identification of an Ascariasis infection is the wet mount. The wet mount is prepared from a stool sample; “fixing it in 10% formalin, concentrate using the formalin-ethyl acetate sedimentation technique”, and then examining the wet mount of the specimen.(2) If the concentration techniques are not available a simple wet mount is sufficient for detecting moderate to heavy infections. Larvae can be identified during the pulmonary phase in the sputum, and adult worms can be identified in the stool or protruding from the mouth or nose, in serious cases. Abdominal X-rays and malnutrition can lead to the identification of an infection.(4)
It is estimated that one billion people are infected with Ascariasis worldwide.(4) The highest occurrence has been seen in tropical and subtropical regions and areas with poor sanitation.(2)
A description of the growth of this round worm, once it infects the body, is helpful in describing the signs and symptoms of the infection. Once the eggs have been ingested and reach the digestive tract they release larvae that penetrate the intestinal wall and move into the respiratory tract, specifically the lungs, by means of the liver and bloodstream. Once in the lungs a ten day incubation period passes and the larvae migrate into the upper lung and airway passages where they are swallowed again. When they return to the intestine, they mature into adults and begin to reproduce releasing 200,000 eggs a day, which are expelled through either the mouth or anus.(1) The adult worms can grow to be 12-14 inches long and their initial incubation period is 60-75 days. Signs and symptoms of the disease include, sporadic respiratory symptoms of pneumonitis with coughing, wheezing, pulmonary infiltrates, and a fever will occur after the eggs hatch in the small intestine and move to the respiratory system. The gastrointestinal symptoms include nausea and vomiting which in some causes contains worms. The adult worms are easily seen in the stool and the worms may easily emerge from the stomach through the nose or mouth as a result of coughing or vomiting.(5)
Ascariasis is treated with an antihelminthic medication. These medications destroy roundworms by either paralyzing them or by blocking them from feeding. Research has found that there is not yet a treatment for the pulmonary phase. The intestinal phase is treated with albendazole 400mg in a single dose for light infections or a daily dose for three days for heavier infections. Pryantel pamoate 10mg/kg in a single dose or mebendazole 100mg for three days or mebendazole 500mg in one dose is also effective for both children or adults.(6) A benefit of using albendazole or mebendazole is that these are also effective treatments of hookworm and whipworm infections.(6) Infections complicated by intestinal obstruction may be treated with piperazine 50-75 mg/kg for two days and for severe infections piperazine treatment may be repeated after one week. The intestinal obstructions rarely require surgery.(2) After treatment, stools should be checked regularly every two weeks and if necessary the patient can be re-treated until there are no more ascarids. There is some disagreement about treatment during pregnancy or for nursing mothers.
The best strategy for the prevention of an ascariasis infection is using proper sanitation techniques and avoiding uncooked foods. Other recommendations for reducing the rate of infections are; “avoiding soil that could be contaminated with feces, washing hands with soap and water before handling food, wash, peel, or cook all raw vegetables and fruits, protect foods from soil and wash or reheat any food that falls on the floor”.(1) Currently there is no vaccine for Ascariasis.
Works Cited:
1) Anonymous. Water Related Diseases; Ascariasis http://www.who.int/water_sanitation_health/diseases/ascariasis/en/ 04/26/2004
2) Anonymous. Ascariasis. 12/13/2002. http://www.dpd.cdc.gov/dpdx/HTML/Ascariasis.htm 04/26/2004.
3) Anonymous. Ascaris lumbricoides. 04/09/1999. http://medinfo.ufl.edu/year2/mmid/bms5300/bugs/asclum.html 04/27/2004
4) Christopher Parsons M.D. Ascariasis. 7/30/2002. http://www.nlm.nih.gov/medlineplus/ency/article/000628.htm 4/27/2004
5) Anonymous. Ascaris lumbricoides and Ascaris suum (intestinal roundworms of humans and pigs). http://www.biosci.ohio-state.edu/~parasite/ascaris.html 04/26/2004
6) Anonymous. Nematodes-Ascariasis. http://mednet3.who.int/eml/disease_factsheet.asp?diseaseId=405 4/26/2004