Host Parasite Relationship – Basic microbiology, parasitology, and immunology; nature, reproduction, growth, and transmission of common microorganisms and parasites in Bangladesh; prevention including universal precaution and immunization, control, sterilization, and disinfection; and specimen collections and examination. Students will have an understanding of common organisms and parasites caused human diseases and acquire knowledge about the prevention and control of those organisms.
Host Parasite Relationship
Types of Biological Association/Host-Parasite Relationship:
An association, which is formed between animals of different species, may be divided into 3 categories –
Symbiosis: An association in which both are so dependent upon each other that one cannot live without the help of others. None of partners suffer harm from the association.
Example: Bacterial flora in human intestine.
Commensalism: An association in which the parasite only is deriving nutrition without causing harm to the host. A commensal is capable of leading independent life.
Example: E. coli in human intestine.
Parasitism: An association in which the parasite derives benefit and the host gets nothing in return but always suffers from injury.
Example: Man & hook worm.
Host:
Host may be defined as living organism or animal which provide shelter to the foreign living animal or parasite.
Or,
Hosts are organisms which gives shelter and nourishment to the parasite,
Classes/Types of Hosts:
1. Definitive host
2. Intermediated host
3. Accidental host
- Permissive host
- Non-permissive host
4. Paratenic host (A carrier or transport host)
5. Reservoir hosts.
Definitive Host
That either harbours the adult stage of the parasite or where the parasite utilizes the sexual method of reproduction.
Example: In the majority of human parasitic infections, man is the definitive host such as-
- Ancylostoma duodenale
- Ascaris lumbricoides
- Enterobius vermicularis
Intermediate host:
That harbours the larval stages of the parasite. In some cases larval developments are completed in two different intermediate hosts which are being referred to as first and second intermediate hosts respectively!
Example:
- Man for malarial parasite & Echinococcus granulosus.
- Culex mosquito for Wuchereria bancrofti.
- Man for Toxoplasma gondii.
Accidental Hosts:
Are those in which the parasite does not normally develop but when occasionally infections occur accidentally, the parasite is able to complete its life cycle. Example – Man is accidental host for Echinococcus granulosus
➤ Permissive Hosts: Are those hosts where the parasite can complete its lifecycle. They include true definitive and intermediate hosts as well as many accidental hosts, 210 элд то
➤ Non-Permissive Hosts: Are those accidental hosts where the parasite, can not complete its lifecycle and eventually die within the host. These are the dead end host. e.g. Man is the accidental non- permissive host for Echinococcus granulosus.
Paratenic host (A carrier or transport host):
A host where the parasite remains viable without further development.
Example: Man is the paratenic host in case of cutaneous larva migrans such as
- Ancylostoma braziliensis
- Ancylostoma caninum
Reservoir Hosts:
A reservoir host is a vertebrate animal species that harbors a particular pathogen and acts as a long-term source of infection for other vertebrates or vectors. Reservoir hosts are essential for the maintenance of the infection during times when active transmission is not occurring, e.g. Dog in case of Leishmania donovani
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