Q90. In case of parasites that require multiple hosts to complete their life cycle, what does definitive host mean?
- It is the host that harbors the sexual stages of the parasite.
- It is the host in which the parasite reproduces asexually.
- It is the host in which the parasite feeds.
- It is the host in which the parasite remains in a dormant stage.
In parasites with complex life cycles requiring multiple hosts, the definitive host serves as the site for sexual reproduction and maturation of the adult parasite form. This contrasts with intermediate hosts where asexual multiplication occurs. Understanding host roles is crucial for disease transmission and control.
Correct Answer
The definitive host harbors the sexual stages of the parasite.
Here, the parasite reaches maturity, undergoes gamete formation, and produces eggs or offspring to continue the cycle.
Examples include humans for Taenia solium (pork tapeworm) or cats for Toxoplasma gondii.Option Analysis
Sexual Stages (Correct)
Sexual reproduction completes the parasite’s life cycle in this primary host.
Adult worms or protozoa produce fertilized eggs shed via feces or other routes.
Distinguishes from intermediate hosts’ larval/asexual phases.Asexual Reproduction
This occurs in intermediate hosts during larval multiplication (e.g., schizogony in malaria).
Definitive hosts lack these proliferative stages.
Incorrect for the final reproductive host.Parasite Feeding
All hosts provide nutrients; feeding is not host-specific.
Definitive role ties to reproduction, not just nutrition.
Too vague for classification.Dormant Stage
Dormancy (encystment) happens in intermediate or transport hosts.
Definitive hosts support active adult sexual phases.
Not characteristic of this host type.Option Definitive Host Role? Parasite Stage Examples Sexual stages Yes Adult gametes/eggs Humans (tapeworms) Asexual reproduction No Larval multiplication Mosquito (malaria) Parasite feeds No Any host General nutrition Dormant stage No Encysted forms Intermediate cysts This distinction underlies epidemiology of diseases like malaria or schistosomiasis.
