Ascariasis a condition resulting from infestation by Ascaris lumbricoides, a nematode parasite of the family Ascaridae. The parasite, commonly known as roundworm, has undoubtedly been one of man's companions from time immemorial, probably since the beginning of domesticating pigs. A. lumbricoides is a large nematode that lives in the small intestine of man and pig. An adult worm may be up to 30 cm in length. Its mouth is guarded by three lips, one dorsal, and two latero-ventral, each with minute papillae. Infection ordinarily results from swallowing embryonated eggs, which are more frequently conveyed to the mouth by fingers than by other means. In some places in Bangladesh heavy infection is directly correlated with polluted water supplies. In slums and in rural areas the mud floors of houses are heavily seeded with Ascaris eggs, and since people sit, lie, eat, and play on the floor, opportunities for infection are numerous. The playing of children on polluted ground near their homes, tracking of pollution into the houses, and eating with dirty hands are some of the most important factors in the epidemiology.

Ascariasis results in submucosal haemorrhage and ulcer in the intestine. As a result, the liver may show varying degrees of fibrosis, which may be localized in the form of milk spots. Larvae cause haemorrhages in the lungs, alveoli and bronchioles. The parasite may cause abdominal discomfort and acute colic pains, vomiting, etc. Bile duct or intestinal obstruction may result if the number of parasites in high. In Bangladesh, rural children up to age of 12 to 14 are more commonly infected. Ascariasis requires medical attention. Home remedies or preparations from quacks are useless and may even be harmful.

Toxocara vitulorum causes ascariasis in young cattle and buffaloes. This parasite is characterized by the presence of three lips, broad at the base and narrow anteriorly. The parasite contributes significantly to buffalo calfhood mortality. About 85% of buffalo calves are reported to suffer from this deadly disease in certain parts of Bangladesh. The dominant cilinical signs are diarrhoea and steatorrhoea. They may be accompanied by colic, signs resembling intestinal obstruction and the presence of mud-coloured, nasty smelling faeces. The occlusion of bile duct and perforation of liver and small intestine is often noticed in dead calves. The piperazine compounds are usually used against ascarids in animals and birds. Good hygienic management and proper disposal and treatment of manure need to be followed for prevention and control of ascarid infection. [AWM Shamsul Islam]

See also worm.