Vector-borne disease transmission mechanisms

There are two ways that vector-borne diseases are transmitted:

  1. Mechanical transmission takes place when a vector simply carries pathogenic microorganisms on their body and transfers them to food, which we then consume. Flies and cockroaches are in this category. Flies like to rest on faecal matter and then may move on to fresh food. They can carry infectious agents through their mouth and on their legs and other body parts. They deposit these agents on ready-to-eat foods and the recipient gets infected if they consume the contaminated food.
  2. Biological transmission involves the multiplication and growth of a disease-causing agent inside the vector's body.

Malaria is a good example of biological transmission. The female mosquitoes take the malaria infectious agent (Plasmodium) from an infected person with a blood meal. After sexual reproduction in the gut of the mosquito, the infectious agent migrates into the salivary gland of the insect, where it grows in size, matures and becomes ready to infect humans. When the mosquito next bites a human the saliva is injected into the skin and transfers the infection in doing so. An infectious agent may be passed from generation to generation of vector — this happens mostly in ticks and mites.

Important vectors and disease transmission mechanisms.

VectorDiseasesMechanism
Housefly Diarrhoeal diseases, TB, polio, worms, food poisoning, infective hepatitis Mechanical
Mosquito Malaria, yellow fever, filariasis, dengue fever Biological
Louse Typhus fever, relapsing fever, dermatitis Biological
Mite Scabies, chigger Biological
Flea Plague, murine typhus/endemic typhus Biological
Sandfly Leishmaniasis Biological
Blackfly Onchocerciasis Biological
Bedbug Dermatitis, Chagas disease Biological
Cyclops Guinea worm, fish tapeworm Biological
Tsetse fly Sleeping sickness (trypanosomiasis) Biological
Freshwater snail Schistosomiasis Biological
Dog Rabies Biological
Last modified: Wednesday, 2 July 2014, 12:21 PM