Worms are parasitic organisms that thrive inside living hosts. They derive their nutrients from the host and often cause some health complications for the host through their activities. Some of the most common types of parasitic worms include roundworms, tapeworms and flukes. These worms are acquired through ingestion and contact with objects, animals or people that have been contaminated with the parasites.
Infestation by cysts containing the larvae of the tapeworm can lead to hydatid disease. Hydatid disease primarily affects livestock, such as sheep, or domestic animals, including dogs. When a dog eats uncooked meat containing tapeworm cysts, the immature larvae will develop into adults inside the dog's intestine. The adults will lay eggs and exist through the dog's faeces. When humans touch the faeces or anything that has been contaminated with the faeces, they might transmit the eggs to their food and ingest it. When the eggs enter the human digestive system they will hatch into larvae and migrate to the bones, lungs or liver. When they reach these areas, they will develop into cysts. A hydatid cyst in the lungs can lead to coughing and chest pain. A hydatid cyst in the bone can cause pain or even a fracture in the bone. When the hydatid cyst infects the liver, it may lead to jaundice, nausea and pain.
Infestation of various organs with roundworm larvae may lead to toxocariasis. These roundworms can infest domestic animals such as cats and dogs. The animals will pass the eggs of the roundworms from their faeces. Children are often more likely to be infested with roundworms because they tend to put their dirty fingers in their mouth after playing in the dirt. When the eggs of the roundworms are swallowed, they hatch into larvae in the intestine. These larvae will proceed to infest other parts of the body, including the liver and lungs. Mild roundworm infestation can cause a low fever while a heavy infestation in the lungs can cause coughing and wheezing. If the larvae migrate to the brain, the infestation may cause epilepsy. If the larvae infest the eye, it may lead to blindness.
Schistosomiasis can be caused by any of the five species of fluke. Flukes are parasitic flatworms that normally penetrate the skin of the hosts. People who bathe in lakes or freshwater pools are more likely to be affected by schistosomiasis. Freshwater snails release the larvae of flukes, which penetrate the skin and mature inside the body. Effects of flukes include blood in the urine, constant coughing, nausea, muscle spasms and a burning sensation while passing urine. Infestation with flukes may also lead to bladder tumours, colorectal cancer and liver damage.
Hookworms can infect hosts by piercing the skin. This is usually though contact with sewage, infected faeces or soil. Mild hookworm infestation may cause cough, mild fever and abdominal pain. Large numbers of hookworms in the host will lead to anaemia, which could cause chronic heart failure.