Bilharzia is a waterborne disease. Image credit

ZIMSEC O Level Geography Notes:Common Killer diseases in the Tropics: Bilharzia

  • Is also known as schistosomiasis.
  • It is another serious infection and wide spread in Africa and other tropical and sub-tropical regions.
  • The disease is caused by a flat worm that lives in various parts of the blood stream.
  • Adult worms live up to 25 years, laying thousands of eggs into the blood stream of an infected person.
  • These find their way either into the urinary bladder or intestine of the infected person before being passed out.
  • With the poor sanitation levels in developing countries, the eggs find their way into unprotected water bodies like rivers, dams and wells.
  • The eggs hatch in fresh water and the larva enters into water snails.
  • In the snails the larvae undergoes changes and multiplication.
  • This reproduction phase produces cercaria larvae which eventually leaves the snail and swims in the water ready to infect the next person who baths, swims, walks in the water or drinks the water.
  • These burrow through the skin to reach blood vessels.
  • The larvae will remain in the blood stream for about ninety days before resting in the bladder or intestine as adult worms.
  • The worm or blood flukes cause inflammation of the bladder, pain and bleeding which weakens the body making the victim ill and less productive.
  • Symptoms include passing of blood stained urine, body weakness and pain.
  • Bilharzia can be controlled by the use drugs that kill the worm in the human body or by killing the snails in their breeding places such as rivers, dams and irrigation canals.
  • It can also be controlled by improving sanitation and thus preventing human waste and urine from reaching fresh water bodies.
  • Safe facilities for washing clothes and bathing should be provided to avoid human contact with contaminated water.

To access more topics go to the O Level Geography Notes page