Disease Vectors and Pathogens

The Widal test detects Salmonella typhi antibodies in serum, diagnosing typhoid fever. It tests for agglutinating antibodies against O and H antigens, not for malaria, cholera, or dengue.

The sporozoite is the infectious form of the malaria parasite (Plasmodium) that enters the human body when an infected female Anopheles mosquito takes a blood meal. From the bloodstream, sporozoites travel to the liver to begin the next stage of their life cycle.

Rodents serve as an intermediate host for Echinococcus multilocularis.

Diphyllobothrium latum, also called fish tapeworm, causes severe vitamin B12 deficiency due to the parasite absorbing 80% of it. This leads to megaloblastic anaemia.

Snails act as an intermediate host for trematodes.

Onchocerca volvulus infection leads to blindness. It is the main cause of river blindness in Africa and is transmitted by the black fly. It forms nodules in the head.

Infections by Baylisascaris procyonis (Racoon worm) are very rare, but very dangerous. This is because the worm migrates to the brain and causes a lot of damage.

This is wrong. Only the encapsulated groups of Trichinella infect the mammalian host.

The farmer was infected by Schistosoma mansoni because sub-terminal eggs are only produced by Schistosoma mansoni. 

Elephantiasis tropica is caused by Wuchereria bancrofti. 

Clonorchis sinensis is Chinese liver fluke which causes serum sickness disease. Fasciola hepatica is sheep liver fluke which causes asymptomatic fever. Fasciolopsis buski is giant intestinal fluke which may cause abdominal pain and diarrhoea. Paragonimus westerman is lung fluke which may cause tuberculosis-like symptoms.

Skin is most affected in Ancylostoma caninum infection because larvae cannot penetrate further.

Ringworm is the odd one out because it is a fungal infection (dermatophytosis), not a worm. Guineaworm, Hookworm, and Tapeworm are all actual parasitic worms (helminths) that infect humans. The name 'ringworm' is misleading - it's caused by fungi, not parasitic worms.

Mouth part of mosquito is sucking and piercing type.  

Visceral leishmaniasis (VL), also known as kala-azar, black fever, and Dumdum fever, is the most severe form of leishmaniasis. Leishmaniasis is a disease caused by protozoan parasites of the Leishmania genus.