Match List – I with List – II.

List – I (Water specific diseases)	List – II (Examples)
A. Water borne diseases	I. Malaria
B. Water washed diseases	II. Schistosomiasis
C. Water based diseases	III. Typhoid
D. Water related diseases	IV. Trachoma

Choose the correct answer from the options given below:

The correct option is A-III, B-IV, C-II, D-I.

To understand why this match is correct, let's break down the classification of water-associated diseases as categorized by the World Health Organization (WHO):

1. Water-borne diseases (A - III):
These diseases are transmitted by consuming water contaminated by human or animal feces or urine containing pathogenic bacteria, viruses, or parasites. Typhoid fever (caused by the bacterium Salmonella typhi) is a classic example of a water-borne disease, as it spreads primarily through the ingestion of contaminated food or water.

2. Water-washed (or water-scarce) diseases (B - IV):
These diseases occur due to a lack of adequate water for personal hygiene (such as washing hands, face, and body). Under-washing allows pathogens or vectors to thrive on the skin or eyes. Trachoma is a bacterial infection of the eye caused by Chlamydia trachomatis. It is heavily associated with poor sanitation and insufficient water for facial cleanliness, making it a water-washed disease.

3. Water-based diseases (C - II):
These are caused by pathogenic organisms (like parasitic worms) that spend part of their life cycle in aquatic hosts (such as freshwater snails) before infecting humans through skin contact or inhalation. Schistosomiasis (also known as bilharzia) is caused by parasitic flatworms. The parasites penetrate human skin during contact with infested freshwater, fitting perfectly into the water-based category.

4. Water-related (or insect-vector) diseases (D - I):
These diseases are transmitted by insect vectors, such as mosquitoes, that breed in or bite near water habitats. The pathogens themselves do not live in the water, but their vectors rely on water bodies to complete their life cycles. Malaria is transmitted to humans by the bite of infected female Anopheles mosquitoes, which breed in stagnant water, making it a water-related disease.

Matching these definitions to the items gives us:
A. Water borne diseases → III. Typhoid
B. Water washed diseases → IV. Trachoma
C. Water based diseases → II. Schistosomiasis
D. Water related diseases → I. Malaria