Disease Vectors

Animals that carry disease-causing organisms (pathogens) from one host to another are called vectors. The most important group of disease vectors are arthropods. Arthropod vectors transmit disease by two general methods. Mechanical transmission is the passive transport of the pathogen on the insect's feet or other body parts. If the insect makes contact with a host's food, microbes can be transferred to the food and later swallowed by the host. Houseflies, for instance, can transfer Salmonella or Shigella bacteria from the feces of infected people to food.

Biological transmission is an active process and is more complex. The arthropod bites an infected person or animal and ingests some of the infected blood. Pathogens then reproduce in the vector and the increase in the number of pathogens increases the possibility that they will be transmitted to another host. Some parasites reproduce in the gut of the arthropods; these can be passed with feces. Other parasites reproduce in the vector's gut and migrate to the salivary gland; these are directly injected into a bite.

Match the diseases listed below with their vectors.