The human body can harbour many types of intestinal worms. Some are relatively harmless, while others cause considerable discomfort and illness. Depending on the type of worm, the symptoms can range from no symptoms or mild itching, diarrhoea and vomiting to extreme abdominal pain, intestinal bleeding or serious effects on other body organs.The primary intestinal worms which cause detrimental effects in humans are: pin worms, hookworms, strongyloides, tapeworms, toxocara, trichinella and whip worms.
Pin worm eggs are spread from infected person through ingestion of the eggs from contaminated hands or objects. Children are the usual carrier for pin worms which cause perianal itching. The adult worm can be found in this area either through visual inspection or through the application of a strip of cellophane to the area, which picks up the eggs. This strip is then mounted on a microscope slide and examined for eggs.
Hookworms are spread either from ingestion of larva or from direct contact with soil harbouring the hookworm larva. Walking barefoot through contaminated soil is a common way to contract a hookworm infection. There are two types of human hookworms: Ancylostoma duodenale and Necator americanus. A person infected with hookworm may develop an itchy rash where the hookworm penetrated the skin. After the worms become established in the intestinal tract there will be symptoms of gas, abdominal pain, loss of appetite and diarrhoea. Severe or chronic infection leads to iron deficiency anaemia.
Like the hookworm, infection with strongyloides is through contact with contaminated soil. The adult worms of Strongyloides stercoralis live in the human small intestine. A person infected with strongyloides may not show any symptoms or she may experience loss of appetite, diarrhoea, vomiting, nausea and abdominal pain. A few cases will develop into a severe infection of many body organs and cause serious damage.
The infection of humans with tapeworms is called taeniasis. There are two main types of tapeworms which cause human infection: the beef tapeworm (Taenia saginata) and the pork tapeworm (Taenia solium). A person becomes infected with tapeworms through ingestion of raw or undercooked meat which is infected with the worm cyst. The worm then attaches to the small intestine and begins to produce segments, called proglottids, which hold the eggs. These segments detach from the main tapeworm and pass out in the faeces. Cattle and pigs then eat grass or feed contaminated with these eggs, perpetuating the tapeworm cycle.
Toxocara infections (toxocariasis) is a zoonotic disease or a disease which is spread from animals to humans. Cats and dogs can be infected with this worm and pass them on to humans. Humans acquire the infestation through ingestion of the eggs which are passed out of the animal's body in the stool. The eggs develop into larva which can then cause one of two diseases in people: ocular larva migrans (OLM) or visceral larva migrans (VLM). In OLM, the larva penetrates the eye and may cause problems with vision. Individuals with VLM will have damage in the body organs that the larva pass through.
Classic trichinosis results when the roundworm, Trichinella spiralis, is ingested in raw or undercooked pork products. Other species of Trichinella are found in other birds and mammals. These species can also infect humans. The disease develops when cysts containing larva is ingested in meat. The larva are then released from the cysts and burrow into the small intestine. They develop into adult worms which release larva. The larva migrate to muscles and cause symptoms such as muscle and joint pain or abdominal pain.
Whip worms are the third most common worm infection in people. Whip worms in humans are acquired from ingestion of the eggs of Trichuris trichiura. The eggs hatch into larva in the small intestine and develop into adults. The adults live in the large intestine. People with heavy infection can develop trichuris dysentery that can cause anaemia, bloody diarrhoea and growth retardation.