According to the World Health Organisation, malaria kills a child every 30 seconds. Malaria is caused by a tiny parasitic protozoan called Plasmodium. Plasmodium enters the human body in its infectious form, known as sporozoites, through the bite of the female Anopheles mosquito. Sporozoites travel through the blood to reach the liver, where they initially multiply to form merozoites inside the liver cells. The liver cell bursts and the merozoites are released into the blood. Then, they attack the red blood cells by multiplying again leading to the rupture of RBCs which release haemozoin, which causes chills and high fever. As the released parasites go on to infect new RBCs, some merozoites develop into sexually differentiated forms such as male and female gametocytes. So when the female Anopheles mosquito bites an infected person, these gametocytes enter the mosquito’s body. They further fertilise and develop inside the mosquito’s intestine to form sporozoites. These sporozoites migrate from the intestine to the salivary glands of mosquitoes, where they are then stored. Later when these mosquitoes bite healthy individuals, the sporozoites are introduced into the human body, repeating the same chain of events.
Amoebic dysentery is another disease caused by a protozoan called Entamoeba Histolytica that lives in the large intestine of human beings. It is characterised by symptoms such as the discharge of blood and mucus in the faeces. Houseflies act as vectors by transmitting the parasite from the faeces of the infected person to food and water. It is caused by by consuming contaminated food.
Therefore, maintaining both personal and public hygiene is crucial for the prevention and control of several infectious diseases such as the common cold, typhoid, polio and diphtheria.
Keeping water and food clean is important because most infectious diseases like typhoid, amoebiasis and ascariasis are spread by vectors that are transmitted through contaminated food and water. Further, it is important to control or eliminate vectors along with their breeding places. Undertaking control measures prevents the transmission of diseases such as malaria and filariasis, dengue and chikungunya, which are transmitted by a mosquito vector called Aedes.
For air-borne diseases like pneumonia and the common cold, care must also be taken that contact with infected persons and their belongings are avoided.
With new, emerging developments in biotechnology, several antibiotics and drugs have been discovered that are effectively used in the treatment of infectious diseases.