As we study about the parasites (parasitology) the following parts will be discussed under every parasite

Geographical distribution

Morphology of various stages

Life cycle

Transmission and epidemiology

Pathology

Diagnosis

Treatment/management

Control/prevention

Parasitology is the scientific study of parasites, their hosts, and the relationship between them.

as a biological discipline, the scope of parasitology is not only determined by the organism and environment in question, but also by their ways of life.

Parasite is an organism that lives on or in another organism of different species known as host, from which it obtains food, shelter and protection.

Pathogen is any organism that can cause a disease.

Parasitism is the association between two organisms of different species in which one organism (parasite) benefits while the other (host) is harmed.

example: ticks on the bodies of dogs, cattle etc.

Symbiosis is the association between two organisms living together either temporary or permanently.

It means living together in a close relationship

Example

Mutualism –both organisms in the association benefit e.g. gut bacteria, bees and flowers

Commensalism –one organism benefit while the other do not, but not affected too e.g. the bird nests on tree and entamoeba coli in gut

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Parasitism –the association in which one organism (parasite ) benefit from the association or relationship while the host is affected, the parasite deprives the nutrients and shelter.

Plasmodium spp

Entamoeba histolytica

Ascaris lumbricoides

Necator americanus

Ancylostoma duodenale

Balantidium coli

Schistosoma mansoni

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Phoresis is the association between two organisms of different species in which one organisms usually a smaller organism (phoront) is mechanically carried by another larger organism (the host), no dependency or physiological interaction in procurement of food by either partner.

Example: sedentary protozoans, attached on bodies of aquatic turtles.

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example

ascaris lumbricoides

Plasmodium spp

Hookworms

Trichuris trichiura

A condition is called infection

Ectoparasite is the one that lives outside the host.

example

pediculus humanus corporis

Tick infestation

Pediculus humanus capitis

Pthirus pubis

A condition is known as infestation

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example plasmodium falciparum

Facultative parasite is the parasite which can survive in the absence of the host.

it is free living organism but is capable of becoming parasite in conducive situation.

example

Naegleria fowleri

Entamoeba coli

Candida albicans

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Accidental or Incidental Parasites: these are not normal parasites of man but enter or attach to the body and cause parasitism in man.

For example, Toxocara Canis that causes visceral larva migrans in man.

Opportunistic Parasite: these are usually commensals or non-pathogenic organisms that invade the body and cause disease when the host’s immune status is compromised.

Examples toxoplasma gondii.

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Larval Parasites: larval parasites are pathogenic parasites which infect man and cause pathology during their larval stage of development.

their adults may be parasites of other animals; man, or they may be free-living. e.g. echinococcus granulosa.

Zoonosis is any infection/disease that is naturally transmissible from vertebrate animals to humans and vice-versa.

Zoonotic disease is a disease that can be transmitted between vertebrate animals and humans.

For example, trichinella spiralis.

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These hosts, in comparison to their parasites are (usually) relatively larger in size than the parasites.

Primary host or Definitive host is the host that harbours parasite in adult/mature or sexual stage.

For example, man is definitive host for S. haematobium

Secondary host or Intermediate host is the host that harbours the immature or asexual stage of the parasite.

for example, Bulinus spp is intermediate host for S. haematobium

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example: mosquito is a natural host for plasmodium

Reservoir host: is one which make parasites available for transmission to other hosts. Example dogs are reservoir for leishmania donovani

an animal that harbors a parasite which is also infective to humans.

Accident host: is one which under normal circumstances is not infected with parasites.

Transport host: an animal that harbors a parasite that does not reproduce; it carries the parasite from one location to another to infect a new host

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Vector: is an organism that transmit pathogens (parasites) from one host to another or from a source of infection to the susceptible host.

Mechanical Vectors

are vectors which assist in the transfer of parasite forms between hosts but are not essential in the life cycle of the parasite, i.e. no parasite development occurs in such vectors.

Examples of mechanical vectors are musca domestica which can transfer cysts of entamoeba histolytica from faces to food that is eaten by man.

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Biological Vectors are vectors in which there is biological development of the parasite before it can be transmitted. for example, anopheles’ mosquitoes are biological vectors of plasmodium spp.

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Helminthes

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These belongs to two phyla

Platyhelminthes

Nemathelminthes

PLATYHELMINTHES

There are two medically important classes which include

1.Cestoda (tapeworms).

These are band-like and segmented

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Taenia solium (Pork tape worm)

Taenia saginata (Beef tape worm)

Hymenolepis nana (Dwarf tape worm)

Diphyllobothrium latum (Fish tape worm)

Echinococcus granulosus (Dog tape worm)

Dipylidium caninum (dog tape worm)

Trematoda (flukes)

Flukes are typically leaf-shaped

Examples of trematodes of medical importance include

Blood fluke – Schistosoma spp,

Lung flukes -Paragonimus spp

Liver flukes – Clonorchis sinensis,fasciola hepatica, Opisthorchis spp

Intestinal flukes -Fasciolopsis, heterophyes,metagonimus, echinostoma spp

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These have separate-sexes and unsegmented roundworms

They have body cavities

They have complete digestive, reproductive and nervous systems

They include many parasitic species that infect humans.

intestinal nematodes

Ascaris lumblicoides

Trichuris trichiura (Whip worm)

Enterobius vermicularis (Thread, pin or seat worm)

Strongyloides stercoralis

Hookworm

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Loa loa spp

Wuncheleria spp

Onchcerca volvulus

Brugia spp

Trichnella spp

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Protozoa

Blood protozoan genera

plasmodium, trypanasoma, leishmania, borrelia

Intestinal parotozoan genera

entamoeba, giardia, cryptosporidium, balantidium,

Urirogenital protozoan genera

trichomonas vaginalis

Tissue protozoan genera

toxoplasma, acanthamoeba, naegleria

ENTOMOLOGY

Mosquito

Tsetse fly

Black fly

Housefly

Flea

Ticks

Cockroach

Lice

Mites

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You can not change the past but

you can have the future