Disease Vectors and Pathogens

Malaria parasites infect and destroy red blood cells (erythrocytes) during their reproductive cycle. The spleen acts as a filter for damaged and abnormal blood cells, removing the massive numbers of dead erythrocytes resulting from malaria infection. This increased workload causes the spleen to enlarge (splenomegaly) as it accumulates the destroyed cells.

Female mosquitoes require blood proteins for egg development and have evolved specialized piercing mouthparts (proboscis) to penetrate skin. Male mosquitoes feed only on plant nectar and have mouthparts adapted for sucking liquids from surfaces, lacking the sharp, piercing structures necessary to break skin. This anatomical difference prevents them from feeding on blood.

On infection with virus, depositions of electron dense material between cell wall and plasma membrane may occur over substantial areas. These are called paramural bodies.

Aedes aegypti is a mosquito that can spread dengue fever, chikungunya and yellow fever viruses.

Contagious diseases are those diseases which are communicable by contact with a patient suffering from it, or with some secretion of, or object touched by, such a patient. Ringworm is a contagious fungal infection caused by mold-like parasites that live on the cells in the outer layer of your skin. Leprosy is a contagious disease caused by a bacteria Mycobacterium leprae, but is not easily transmitted.

Balantidiasis is a protozoan infection caused by infection with Balantidium coli. Malaria parasites belong to the genus Plasmodium (protozoan). Kala-azar (Leishmaniasis) is caused by Leishmania donovani (protozoan). Giardiasis is caused by microscopic protozoan parasites known as Giardia intestinalis.

All are helminthic diseases.Ascariasis is an infection caused by Ascaris lumbricoides, giant roundworm of humans belonging to the phylum Nematoda. Ancylostomiasis is the condition of infection by Ancylostoma hookworms. Enterobiasis (pinworm infection) is caused by a small and thin white roundworm called Enterobius vermicularis. Wuchereria bancrofti is a human parasitic roundworm that is the major cause of filariasis.

Elephantiasis or filariasis is a vector borne helminthinc disease (caused by Wuchereria bancrofti) transmitted by female Culex mosquito.

The infective stage of Plasmodium (malaria parasite) transmitted to humans through mosquito bite is the sporozoite. Sporozoites are injected from mosquito salivary glands, enter the liver, and develop into merozoites which infect red blood cells.

The signet ring stage occurs when Plasmodium merozoites invade red blood cells during the erythrocytic cycle. The nucleus and cytoplasm arrange in a characteristic ring pattern. Exo-erythrocytic schizogony happens in liver cells, sporogony in mosquitoes, and gamogony produces gametes.

Ascaris is a parasite that lives in the human intestine and absorbs nutrients from the host's digested food. Autotrophs produce their own food (plants). Facultative organisms can switch modes, but Ascaris is exclusively parasitic. Calling it a 'heterotroph' is less specific than 'parasite'.

Kala-azar (visceral leishmaniasis) is caused by the protozoan parasite Leishmania donovani. It is transmitted through the bite of infected sand flies and affects internal organs like spleen, liver, and bone marrow, often proving fatal if untreated.

The cercaria is the free-swimming infective stage of liver flukes (Fasciola hepatica) that actively penetrates the host's skin. Redia and miracidium are earlier developmental stages, while cysticercus is a tapeworm larval stage.

Sleeping sickness (African trypanosomiasis) is caused by protozoan parasites of the genus Trypanosome, specifically Trypanosoma brucei. It is transmitted through the bite of infected tsetse flies and affects the central nervous system if left untreated.