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Is an infectious agent, or more commonly germ, is a biological agent that causes disease to its host. There is a classification into pathogens:
* Viral
* Bacterial
* Fungal* Eukaryotic, other fungal
* Prionic
Phthiraptera – Lice
Human lice (Pediculus humanus and P. capitus) spread Borellia recurrentis, a spirochaete pathogen that causesepidemic relapsing fever.   They also carry the rickettsial pathogens that cause epidemic typhus (Rickettsia prowazeki) and trench fever (R. quintana).


Mosquitoes in the genusAnopheles are the principle vectors of malaria, a disease caused by protozoa in the genus Trypanosoma.   Aedes aegypti is the main vector of the viruses that cause yellow fever and dengue.   Other viruses,the causal agents of various types of encephalitis, are also carried by Aedes spp. mosquitoes.   Wuchereria bancrofti and Brugia malayi, parasitic roundworms that cause filariasis, are usually spreadby mosquitoes in the genera Culex, Mansonia, and Anopheles.

Horse flies and deer flies may transmit the bacterial pathogens of tularemia (Pasteurella tularensis) and anthrax (Bacillusanthracis), as well as a parasitic roundworm (Loa loa) that causes loiasis in tropical Africa.

Muscidae Calliphoridae Sarcophagidae

House flies (family Muscidae), blow flies (familyCalliphoridae), and flesh flies (family Sarcophagidae) often live among filth and garbage.   They can carry the pathogens for dysentary (Shigella dysentariae), typhoid fever (Eberthella typhosa), and cholera(Vibrio comma) on their feet and mouthparts.   They have also been suspected as vectors of the viral agent that causes poliomyelitis.


Tsetse flies in the genus Glossina transmit theprotozoan pathogens that cause African sleeping sickness (Trypanosoma gambiense and T. rhodesiense).

Siphonaptera -- Fleas

Rat fleas, especially Xenopsylla cheopis (the Oriental rat...
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