Infections of the Blood
This chapter is primarily concerned with the presence of bacteria in the blood. However, many other organisms enter the blood to cause disease. These include those transmitted by various arthropod vectors, such as mosquitoes of the genera Anopheles (malaria), Aedes (yellow fever virus, dengue fever virus), Culex (West Nile virus) and the tsetse fly, Glossina morsitans (African trypanosomiasis/sleeping sickness). Ticks of the genus Ixodes transmit Lyme disease (Borrelia burgdorferi), while rickettsial diseases are transmitted by Dermacentor (Rocky Mountain spotted fever) and Amblyomma (African tick-bite fever) ticks. Wucheria bancrofti, a tissue nematode, is distributed in parts of the tropics and subtropics. Adult worms reside in the lymphatics, and their microfilaria enter the blood to be taken up by blood-feeding female mosquitoes of the genera Aedes, Anophyles and Culex. Passing through the insect's midgut, they reach the thoracic muscles, and mature into larvae that infect the human when the mosquito next feeds.