A vector is an organism which spreads disease-causing parasites or pathogens from one host to another.
Invertebrates spread bacterial, viral and protozoan pathogens by two main mechanisms.
Sandfly species transmit the disease leishmaniasis, by acting as vectors for protozoan Leishmania species, and tsetse flies transmit protozoan trypansomes (Trypanosoma brucei gambiense and Trypansoma brucei rhodesiense) which cause African Trypanosomiasis (sleeping sickness).
For example, the human body louse transmits the bacterium Rickettsia prowazekii which causes epidemic typhus.
Dog Cat Fever, muscle ache, dizziness, neck pain, backache, headache, sore eyes and photophobia (sensitivity to light)Eastern Europe Worldwide Avoiding contact with body fluids