The changes that the malarial parasite undergoes in the mosquito represent which one of the following types of biological transmission?
Cyclopropagative
The correct answer is cyclopropagative. In this form of biological transmission the agent both multiplies and undergoes a cyclical change of form inside the vector. In the female Anopheles, ingested gametocytes of Plasmodium undergo sporogony: gametes fuse to a zygote, which becomes a motile ookinete, penetrates the gut wall as an oocyst, and within it thousands of sporozoites form and reach the salivary glands. Both change of form and multiplication occur, over an extrinsic incubation period of 10–14 days.
Why the others are wrong: Propagative means multiplication only, with no change of form — plague bacilli in the rat flea, or arboviruses in mosquitoes. Developmental and cyclodevelopmental mean developmental or cyclical change without multiplication — classically microfilariae in the mosquito, or guinea-worm larvae in Cyclops. Since Plasmodium clearly multiplies in the mosquito, none of these fits.
Key point: Malaria in mosquito = cyclopropagative; filaria in mosquito = cyclodevelopmental; plague in flea = propagative; housefly spread = mechanical.
Important Questions from Infectious Disease Control & Prevention
As per the Open Vial Policy, partially used multidose vials of which of the following vaccines can be used over more than one immunization session?
1. BCG vaccine
2. DPT vaccine
3. Hepatitis B vaccine
4. Measles vaccine
Select the correct answer using the code given below.
Consider the following statements regarding dengue virus :
1. It has four distinct serotypes.
2. Infection with any one serotype confers lifelong immunity for that virus serotype.
3. Secondary infection with dengue serotype 2 leads to severe form of dengue.
Which of the statements given above are correct?
Consider the following statements regarding dengue :
1. The mosquito becomes infective after an extrinsic incubation period of 8-10 days.
2. Once it becomes infective, the mosquito remains infective for life.
3. The genital tract of the mosquito does not get infected.
Which of the statements given above are correct?
Consider the following statements about Kyasanur Forest Disease (KFD) :
1. It is transmitted by ticks.
2. It was originally called 'pig disease' because of the association with dead pigs.
3. It was first recognized in Karnataka State.
How many of the statements given above are correct?
- In countries with low levels of measles transmission, what should be the appropriate age for starting immuni-zation with measles-containing vaccine (MCV)?
