Common Human Diseases Caused By Helminths- Online Class 12 Biology

Common Human Diseases Caused By Helminths- Online Class 12 Biology

ASCARIASIS: This disease is caused by roundworm Ascarislumbricoides. Infections have no symptoms in more than 85% of cases, especially if the number of worms is small. Symptoms increase with the number of worms present and may include shortness of breath and fever at the beginning of the disease. These may be followed by symptoms of abdominal swelling, abdominal pain, and diarrhoea. Children who are 3 to 8 years old are most likely to be infected because of their contact with soil while playing in the soil; hence they suffer from poor weight gain, malnutrition, and learning problems.

The source of infection is from objects which have been contaminated with faecal matter containing eggs. Ingestion of infective eggs from soil contaminated with human faeces or contaminated vegetables and water is the primary route of infection. Infectious eggs may occur on other objects such as hands, money, and furniture.

The eggs hatch in the intestines, burrow through the gut wall and migrate to the lungs via the blood. There they break into the alveoli and pass up the trachea, where they are coughed up and may be swallowed. The larvae then pass through the stomach for a second time into the intestine, where they become adult worms.

It lies free in the intestine, having no organs for attachment. It feeds on the semi-digested food of the host, the blood, and the fluid of the alimentary canal of the host. There is no secondary host in its life cycle.

The first appearance of eggs in stools is 60–70 days. In larval ascariasis, symptoms occur 4–16 days after infection. The final symptoms are gastrointestinal discomfort, colic and vomiting, fever, and observation of live worms in stools. Some patients may have pulmonary symptoms or neurological disorders during migration of the larvae.  Generally, there are few or no symptoms. A bolus of worms may obstruct the intestine; migrating larvae may cause pneumonitis and eosinophilia. Adult worms have a lifespan of 1–2 years which means that individuals may be infected all their lives as worms die and new worms 

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