Roundworm Infection

Roundworms are wormlike parasites. The most famous representative is the roundworm known as ascaris lumbricoides causing human infection. In addition, there are roundworms affecting the animals such as toxocara canis (dogs) and toxocara catis (cats).


The infection is transmitted by roundworm eggs that leave the body of an infected human (or animal) by feces. If the eggs contaminate food or water, they can infect another person. Naturally, we conclude that the major risk factor is the lack of hygiene. Animal roundworms can easily infect children playing in unprotected sandboxes that may be used by cats and dogs as their “toilets”.


The manifestation of the disease is related to the lifecycle of worms in the human body. In human roundworms (ascariosis), after swallowing the eggs, they reach the digestive tract and the large intestine. There they hatch into larvae. The roundworm larvae penetrate through the intestinal wall, get into the bloodstream, they enter the pulmonary arteries and then the lungs. The pulmonary affection irritates the person and causes episodes of dry cough. The roundworms may get into the nasopharynx and be swallowed again.  In such case, the larvae return back into the intestine, where they mature. Adult roundworms may reach several tens of centimeters. They lay egg hat leave the intestine with the stool and so they may infect another individual.


Animal roundworms (toxocarosis) also get into human intestines in the egg form and the hatched larvae get into the bloodstream. However, here their development ends and the larvae do not return into the intestine to finish their lifecycle.


The manifestations of the roundworm infection include digestive symptoms (diarrhea, loss of appetite, abdominal pain, weight loss) and lung symptoms (dry cough). Exceptionally, multiple roundworms may clog the intestine and cause dangerous intestinal obstruction. Very rarely, some of the worms enter the bile duct and block it disrupting the bile flow and causing jaundice.


Animal roundworms (toxocarosis) can attack many organs including the eye causing vision disturbances.


The suspicion of a parasitic infection can occur from the blood count, where there is increased number of specific white blood cells known as the eosinophils. The final confirmation can be done by microbiological examination of the stool with finding of roundworm eggs or the larvae.


Basic hygiene habits are the best way of prevention. When abroad in less civilized countries, it is advisable to take food and fluid from unknown sources and wash any fruits or vegetables before eating them. House pets should be regularly dewormed (ask your vet).


The roundworms can be treated by special anti-parasitic drugs administered in form of tablets.


Jiri Stefanek, MD  Author of texts: Jiri Stefanek, MD
 Sources: basic text sources