(a) Amoebiasis is caused by a single-celled organism called Entamoeba histolytica. The disease is spread through the ingestion of food or water contaminated with fecal matter containing the parasite. It can also be transmitted through oral-anal contact during sexual activity or through poor hygiene practices, such as not washing hands after using the bathroom.
(b) Malaria is caused by a parasite called Plasmodium, which is spread through the bites of infected female Anopheles mosquitoes. The parasite enters the bloodstream and travels to the liver, where it multiplies and then re-enters the bloodstream, causing symptoms such as fever, chills, and headache.
(c) Ascariasis is caused by a roundworm called Ascaris lumbricoides. The disease is spread through the ingestion of food or water contaminated with the eggs of the worm. The eggs hatch in the small intestine and the larvae migrate to the lungs, where they are coughed up and then swallowed, returning to the small intestine to mature into adult worms.
(d) Pneumonia is an infection of the lungs, which can be caused by a variety of pathogens, including bacteria, viruses, and fungi. It can be spread through the inhalation of respiratory droplets from an infected person who coughs or sneezes, or through contact with surfaces contaminated with these droplets. Certain types of pneumonia can also be spread through contact with contaminated soil or water.
It is important to note that the transmission of each of these diseases can be prevented through a combination of measures, including good hygiene practices, proper sanitation, vaccination, and vector control for diseases such as malaria.