Parasitology
Parasitology: the study of parasites and their relationships to their hosts .
parasitology has traditionally been limited to parasitic protozoa , helminthes, and
arthropods, as well as those species of arthropods that serve as vectors for
parasites.
Medical (human) Parasitology consists of medical protozoology , medical
helminthology and medical arthropodology .
Human parasitology, an important part of parasitology, study the medical
parasites including their morphology, life cycle , the relationship with host and
environment. The objectives are to study the way or the measurement of parasitic
diseases control.
Parasites (from Greek parasitos, para—beside, by; sitos—wheat; meaning one
who eats at the table of another) so Its biolog ical definition is an animal or plant
which lives in or upon another organism(technically called its host) and draws its
nutriment directly from it. By this definition all infectious agents, viruses,
bacteria, fungi, protozoa, and helminths are parasites.
Parasitism
Parasitism is relationship between two organisms: a paras ite, usually the smaller
of the two, and a host, upon which the parasite is physiologically dependent. The
relationship may be permanent ,as in the case of tapeworms found in the
vertebrate intestine, or temporary, as with female mosquitoes, some leeches, and
ticks, which feed intermittently on host blood.
The parasites broadly are of two types: Endoparasite and Ectoparasite. The
parasite which lives within the host is called the endoparasite (e.g, Leishmania).
Invasion by the parasite is called infection. Usually, the endoparasites cause
most human diseases.
Ectoparasite, the parasite which lives on the outer surface or in the superficial
tissues of the host(e.g., Lice). The infection by these parasites is called
infestation
Transmission of Parasites
It depend upon: Source or reservoir of infection, and Mode of transmission.
Source of infection
1) Humans: Humans is the source or reservoir in a majority of parasitic
infections(e.g.,taeniasis, amoebiasis, etc). The condition in which the infection is
transmitted from one infected
man to another man is called anthroponoses .
2) Animal In many of the parasitic diseases, animals act as the source of
infection. The condition where infection is transmitted from animals to humans is
called zoonoses (e.g., hydatid disease).
Mode of transmission
Transmission of infection from one host to another, cause by a certain form of
the parasite is known as the infective stage. The infective stage of various
parasites many be transmitted from one host to another in the following ways.
1) Oral route Ingestion of food, water and vegetable: The infection is
transmitted orally by ingestion of food, water or vegetables contaminated by the
faeces that contain the infective stages of the parasite. This mode of transmission
is referred to as faecal-oral route(e.g., cysts of Entamoeba histolytica；ova of
Ascaris lumbricoides).
2) Penetration of the skin and mucous membrane The infection is transmitted by
Inoculation into the blood by Anopheles (vector for Plasmodium).
For example of protozoa parasite is Plasmodium vivax
The life cycle
of malaria
P. vivax invades erythrocytes. P. vivax Infect red blood cells then it usually
enlarged .
Clinical features
After an incubation period (usually 10 to 17 days), the patient experiences vague
flu-like symptoms, such as headache, muscle pains, photophobia, anorexia,
nausea and vomiting. As the infection progresses, increased numbers of rupturing
erythrocytes liberate merozoites as well as toxic cellular debris and hemoglobin
in to circulation. In combination, these substances produce the typical pattern
chills, fever and malarial rigors. These paroxysms usually reappear periodically
(generally every 48 hours) as the cycle of infection, replication, and cell lyses
progresses.
Treatment
Chloroquine is the drug of choice for the suppression and therapeutic treatment
of P. vivax, followed by premaquine for radical cure and elimination of
gamatocytes.