Most worm infections in humans are due to roundworms, of which there are several types. Among Filipinos, the more common of these roundworms are the ascaris, whipworm, hookworm and pinworm.
The ascaris (scientific name: Ascaris lumbricoides) is the most common parasite that victimize humans. It is so common that among people who harbor more than one type of roundworms, it is almost a certainty that one of them is an ascaris. Experts estimate that 25 percent of the world’s population plays host to the worm.
In some underdeveloped countries, the prevalence rate of ascaris infection is a high 90 percent. In the Philippines, as per UP National Institute of Health and Department of Health figures, 70 percent of the population has ascaris.
The adult ascaris looks like an earthworm, but it is slightly smaller and is white, not brown, in color. It resides in the small intestines where it feeds on digested food.
The female lays as many as 200,000 eggs a day that are discharged with the feces. The eggs are very small and not visible with the naked eye. They have to undergo development in the soil for at least two weeks before they can be infective, thus, ascaris cannot be transmitted directly from human to human.
Instead, a human gets infected when he/she ingests soil, food or water that is contaminated with human feces.
Salads and other foods that are eaten raw are very common vehicles for ingestion of ascaris eggs. Poor personal hygiene, like failure to wash the hands before eating especially after handling contaminated soil, is another major cause of ascaris infection.
After ascaris eggs are ingested, they hatch into larvae in the small intestine. The larvae then enter the bloodstream and are brought to the liver, then the lungs. From the lungs, they travel upwards to the throat where they are swallowed and then transported back to the small intestine where they mature and mate.
A small number of ascaris in the intestines usually produce no symptoms. But in heavy infestations, a variety of signs and symptoms occur including colic, abdominal pain, and coughing out, vomiting or passing out of worms through the nose.
Nutritional deficiencies likewise occur. Sometimes, the worms migrate from the intestines into the bile duct, liver, appendix and other organs and cause serious, sometimes life-threatening, conditions. Rarely, they wrap around each other and form a ball that then obstructs the intestine.
Whipworms (scientific name: Trichuris trichiuria) are small (3.5 to 5 cm. long), flesh-colored roundworms that attach themselves in the walls of the large intestine. Among Filipinos, they are almost as common as ascaris.
The female whipworm lays 5,000 to 7,000 eggs a day that pass out with the stool. These eggs, like those of the ascaris, need to incubate in the soil before becoming infective.
Humans acquire the parasite by ingesting food, water or soil that is contaminated with the eggs. The eggs hatch into larvae when they reach the small intestine, which then migrate into the large intestine where they reside permanently.
In whipworm infection, symptoms occur only if infestation is heavy. Symptoms include abdominal pain, chronic diarrhea, anemia, bleeding, weight lost and rectal prolapse.
Hookworms are small parasites that attach themselves by their mouths to the wall of the small intestine where they feed on blood.
Two species of hookworm infest humans: Ancylostoma duodenale and Necator americanus.
The latter is more common in the Philippines. The female hookworm lays thousands of eggs per day that pass out with the stool.
In the soil, the eggs hatch into larvae. When the larvae get in contact with human skin as when a person walks barefooted or sits in contaminated soil, they penetrate the skin and find their way into the blood stream.
They reach the lungs via the bloodstream and from there travel upwards till they get to the throat where they are swallowed and in the process reach the small intestine.
Hookworm infection can result in anemia, which, in children could lead to stunting of growth and even heart failure.
Pinworms (scientific name: Enterobius vermicularis) are very thin and tiny (two to 13mm) white worms that reside in the large intestine where they feed on digested food.
The female worm deposits its eggs at night in the area around the anus from where the eggs can contaminate beddings, clothes, etc. The eggs can survive outside the body for as long as three weeks.
People get infected with pinworms when they ingest the egg. Pinworm eggs are infective as soon as they are laid; hence, infected people can re-infect themselves by manually transferring the eggs from the area of the anus to the mouth. After ingestion, the eggs hatch and the worms migrate into the large intestine.
Pinworm infection often produces no symptoms. Sometimes, it causes itching in and around the anal area and disturbed sleep. In girls, it can cause vaginal itching and irritation.
The drugs currently available for roundworms are very effective and relatively safe. Most are to be taken as a single dose. However, no one gets immune to roundworms and re-infection occurs very often.
The best way to prevent roundworm infection and re-infection is by proper disposal of human waste (e.g., use of water-sealed or similar toilets). This, of course, has to be a community effort.
Short of this, very effective preventive measures include: washing of hands with soap and water after defecating (especially among food-handlers and children) and before eating; thorough washing in running water of vegetables and other foods that are eaten raw; and, avoidance of walking barefooted.
