Disease Vectors and Pathogens

Racial immunity is when different races within a species show differences in susceptibility to infections. In some parts of Africa, resistance to Plasmodium falciparum malaria is an example of racial immunity.

Dengue fever is transmitted specifically by Aedes mosquitoes, particularly Aedes aegypti. Anopheles mosquitoes transmit malaria, Culex mosquitoes transmit West Nile virus and filariasis, making Aedes the correct answer.

Yellow fever virus is transmitted through Aedes mosquitoes (Aedes aegypti).

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This is the correct option. Wuchereria bancrofti causes elephantiasis, in which enlargement of limbs, scrotum and mammae of humans takes place due to infection.

Tobacco mosaic virus (TMV) is a rigid rod-shaped ssRNA-containing virus that causes distortion and blistering of leaves in a wide range of plants.

This is the major structural protein and covers the RNA genome. It protects the genome from nucleases and holds it in a conformation that allows transcription.

During this stage the cellular proteolytic enzymes digest the capsid away from the nucleic acid. This always occurs in the cytoplasm of the host cell. The period of the replication cycle between the end of the uncoating stage and maturation of new viral particles is termed the eclipse. Thus, during the eclipse stage no complete viral particles can be viewed within the cell.

NSP1, the product of rotavirus gene 5, is a non-structural RNA-binding protein that contains a cysteine-rich region and is a component of early replication intermediates.

Kala-azar (visceral leishmaniasis) is spread by the bite of infected female sand flies belonging to the genus Phlebotomus (Old World) and Lutzomyia (New World). Sand flies transmit the protozoan parasite Leishmania donovani.

Yellow fever is primarily transmitted by the Aedes aegypti mosquito. Aedes mosquitoes are also responsible for transmitting other diseases including dengue, Zika, and chikungunya viruses. Anopheles transmits malaria, Culex transmits West Nile virus, and houseflies are mechanical vectors for bacterial diseases.

Malarial parasites (Plasmodium) rupture from red blood cells synchronously, causing the characteristic fever spikes. The parasites are most abundant in peripheral blood immediately after the temperature rise, which corresponds to the release of merozoites from infected RBCs. This timing offers the best chance for detection in blood smears.

The trophozoite stage of Plasmodium develops within human erythrocytes (red blood cells) after merozoite invasion. Here, the parasite multiplies asexually, consumes hemoglobin, and develops into schizonts. The liver cells contain the exo-erythrocytic stages (sporozoites and merozoites), while the salivary glands of mosquitoes contain sporozoites, not trophozoites.

A digenetic parasite requires two hosts to complete its life cycle. Plasmodium vivax needs both a human host (asexual reproduction) and a mosquito host (sexual reproduction). Monogenetic parasites need only one host, and trigenetic is not a standard parasitological term.

Leishmania donovani causes visceral leishmaniasis, commonly known as kala-azar or black fever. Sleeping sickness is caused by Trypanosoma, amoebiasis by Entamoeba histolytica, and dengue fever by a flavivirus.