SBM 2022 Medical Parasitology & Entomology Lecturer: Sr. Norazsida Ramli

Course assessment Mid semester: 40 % Quiz/ assignment: 10% Final examination: 50%

What is Parasitology? Parasite: a live organism living in, or on, and having some metabolic dependence on another organism known as a host. A weaker organism that obtains food and shelter from the association. It may be a pathogen, causing disease in a host or it maybe nonpathogenic (causing no harm). Host: the harboring species.

THE NATURE OF HOST-PARASITE INTERACTIONS Symbiosis interaction– a permanent association of two organisms that cannot exist independently. Mutualism – both organisms are benefited. Comensalism – one partner is benefited, the other is unaffected. Parasitism: any reciprocal association in which a species depends upon an other for its existence.

Ectoparasite: parasite that lives on the outside of the host (infestation). -Example: tick, mite. Endoparasite: parasite that lives within the body of the host (infection). -Example: Plasmodium sp.

Facultative parasite: parasites that capable of leading both a free and a parasitic existence. For example, Halicephalobus (Micronema) deletrix, a saprophytic soil nematode that is found free-living in nature, has been reported to produce pathology in the CNS of horses. Obligate parasite: parasites that take up a permanent residence in and are completely dependent upon the host. Example: Plasmodium sp.

Incidental parasite: parasite that establishes itself in a host which it does not ordinarily live. For example, Parelaphostrongylus (Pneumostrongylus) tenuis normally is found in neurologic sites within the definitive host, white-tailed deer Temporary parasite: is free living during part of its existence and seeks its host intermittently to obtain nourishment.

Permanent parasite: remains on or in the body of the host from early life until maturity, sometimes for its entire life. Pathogenic parasite: parasite that cause injury to the host by its mechanical, traumatic, or toxic activities. Pseudoparasite: an artifact mistaken for a parasite. Coprozoic parasite: a foreign species that has passed through the alimentary tract without infecting the host. Zoonosis: a disease that caused by zoonotic infection. Can be transmitted from animal to human not from human to animal.

Geographic distribution Tropical countries are most favorable places for the survival, larval development, and transmission of parasites. WHY?????? Bcoz……. Optimal conditions of temperature and humidity are present.

Short summer season (temperate zones) prevents the development of many species that required high temperatures during their larval stages. Intense dry heat/direct sunlight may destroy the larval forms. Low temperatures arrest the development of eggs and larvae and may even destroy them. Freezing temperatures/snow force humanity to use privies and prevent general soil pollution.

Moisture is essential for the development of free-living larvae and propagation of intermediate hosts. Example: arthropods, snails and fishes.

Types of host Definitive host Intermediate host Paratenic host Incidental host Dead-end host Reservoir host

Definitive host The final host harbors the adult or sexual stage of the parasite. Example: human for the Scistosome sp.

Intermediate host (IH) Host that part or all of the larval or asexual stage may take place in another animal. Example: snail for the schistosome. It can be, 2 intermediate hosts for a parasite life cycle: primary and secondary intermediate host. Example: Diphyllobothrium latum, 1 0 IH is copepod, 2 0 is fish.

Paratenic host An animal that harbors the parasite in an arrested state of development; However the parasite is capable of continuing its cycle in a subsequent suitable host. Act as a transportation for parasite. Example: Shrew (tupai tanah)

Incidental host Host that refer to the situation in which the infected individual is not necessary for the parasite’s survival or development. -example: the human being in the case of trichinosis.

Dead-end host Human or incidental host is called as dead-end host if the cycle for transmission of the parasite is such as that it cannot be transmitted further.

Reservoir host Animal that harbor the same parasite. These hosts ensure continuity of the parasite’s life cycle and act as additional sources of human infection. Example: The rabbit as new reservoir host of enterohemorrhagic Escherichia coli.

Life cycle Directly –simple, only need a host. Indirectly –complicated, need more than a host.

Vector Biological vector -act as transportation and host as well -example: mosquito Mechanical vector -act as transportation only. -example: fly