Read the passage and answer the following question:
Some of the human diseases are caused by protozoans too. You might have heard about malaria, a disease man has been fighting since many years. Plasmodium, a tiny protozoan is responsible for this disease. Different species of Plasmodium (P. vivax, P. malaria and P. falciparum) are responsible for different types of malaria. Plasmodium enters the human body as sporozoites (infectious form) through the bite of infected female Anopheles mosquito. The parasites initially multiply within the liver cells and then attack the red blood cells (RBCs) resulting in their rupture. When a female Anopheles mosquito bites an infected person, these parasites enter the mosquito’s body and undergo further development. The parasites multiply within them to form sporozoites that are stored in their salivary glands. When these mosquitoes bite a human, the sporozoites are introduced into his/her body, thereby initiating the events mentioned above. The malarial parasite requires two hosts – human and mosquitoes – to complete its life cycle; the female Anopheles mosquito is the vector (transmitting agent) too.
Choose the incorrect statements about the control of vector-borne diseases:
A. For diseases such as malaria and filariasis, the most important measure is to control or eliminate the vectors and their breeding places.
B. Fishes like Gambusia are introduced in ponds because they feed on adult mosquitoes.
C. Regular cleaning of household coolers helps in controlling the breeding places of mosquitoes.
D. Dengue and chikungunya are vector-borne diseases spread by Anopheles mosquitoes.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → B and D only
Malaria, filariasis, dengue and chikungunya are all carried by mosquitoes. The surest way to control them is to control the vectors and stop them from breeding. Here we must pick out the incorrect statements.
Statement A: For diseases such as malaria and filariasis, the most important measure is to control or eliminate the vectors and their breeding places. — True. These diseases are transmitted through insect vectors, so removing the vectors and their breeding places is the most important measure.
Statement B: Fishes like Gambusia are introduced in ponds because they feed on adult mosquitoes. — False. Gambusia feeds on mosquito larvae. Larvae live in the water of the pond, so a fish can eat them there; adult mosquitoes fly.
Statement C: Regular cleaning of household coolers helps in controlling the breeding places of mosquitoes. — True. Stagnant water in coolers is a breeding place for mosquitoes, so cleaning them regularly is one of the control measures.
Statement D: Dengue and chikungunya are vector-borne diseases spread by Anopheles mosquitoes. — False. Dengue and chikungunya are spread by Aedes mosquitoes. Anopheles is the vector of malaria.
NCERT Extract:
Common Diseases in Humans – “… For diseases such as malaria and filariasis that are transmitted through insect vectors, the most important measure is to control or eliminate the vectors and their breeding places. This can be achieved by avoiding stagnation of water in and around residential areas, regular cleaning of household coolers, use of mosquito nets, introducing fishes like Gambusia in ponds that feed on mosquito larvae, spraying of insecticides in ditches, drainage areas and swamps, etc. In addition, doors and windows should be provided with wire mesh to prevent the entry of mosquitoes. Such precautions have become more important especially in the light of recent widespread incidences of the vector-borne (Aedes mosquitoes) diseases like dengue and chikungunya in many parts of India.”