Mechanisms of infection
A parasitic infection may occur by various routes, depending on
the nature of both parasite and host
- Infection by passive entry.
- By feeding and drinking . Cysts and eggs can be
tranported by water or by insects such as the housefly.
- Giardia, an intestinal parasite of beavers may
contaminate fresh water lakes and rivers in the US. The
drinking of this water may lead to intestinal infections in
- Entamoeba, an intestinal parasite of humans is
transmitted in the form of cysts by the house fly.
- Naegleria, present in surface water may enter via
the nose when swimming and lead to a fatal amoebal
- Acanthamoeba, a facultative
parasite may contaminate soft contact lenses and cause
By direct contact such as sexual intercourse
- Trichomonas, is transmitted via sexual
intercourse and is the causative agent of the most common
sexually transmitted disease amongts humans
- Giardia is widespread amongst the San
Francisco gay community.
- Trypanosoma equinum is a parasite of
equines (horses) and is transmitted via sexual
- Active entry
- By biting (haematophagous)
insects that serve as the active vectors in the transmission of
- mosquitoes transmit malaria and filariasis
- black flies transmit onchocerciasis or river
- tsetse flies transmit sleeping sickness in
- sandfies transmit leishmaniasis
- By highly specialized developmental forms in the
life cycle of the parasite
- Schistosoma cercaria actively penetrate human
Last updated: 6 October 1997.
created by :Fred