Introduction to parasitology Mrs. Dalia Kamal Eldien MSC in microbiology lecture(1)

Introduction to parasitology

Mrs. Dalia Kamal Eldien

MSC in microbiology lecture(1)

Objectives

Definition of parasitology &medical parasitologyIdentify parasitic infection, sings& symptoms Mode of transmission of parasitic infectionImportant definition related to parasitologylife cycle of parasite Host parasite relation shipClassification of parasite

parasitology

Parasitology  is the study of parasites, their hosts, and the relationship

between them. According to the very broad definition of parasitology, parasites should include the viruses, bacteria, fungi, protozoa and metazoa

Medical parasitology   is the study of parasites and parasitic diseases, including

methods the diseases caused by them, clinical picture the diagnosing, treating, and controlling parasitic diseases.

Parasite: organism living in or on, another organism known as a host, to obtain nutrition and shelter from the host as well as does harms to the host

Host : organism harboring a parasite, it supplies the parasite with nutrition and shelter, it is the injured partner.

parasitic infections

A parasitic disease is an infectious disease caused or transmitted by a parasite.

Many parasites do not cause diseases. Parasitic diseases can affect practically all

living organisms, including plants and mammals.  Although parasitic infections occur globally, the majority

occur in tropical regions, where there is poverty, poor sanitation and low personal hygiene

Sings& symptoms

Symptoms of parasitic disease may not always be obvious.

Some of the symptoms caused by several worm infestation can include itching affecting the anus or the vaginal area, abdominal pain, weight loss, increased appetite, bowel obstructions, diarrhea, and vomiting eventually leading to dehydration, sleeping problems, worms present in the vomit or stools, anemia, aching muscles or joints, general malaise, allergies, fatigue, nervousness.

Symptoms may also be confused with pneumonia or food poisoning.

Mode of transmission

Parasites usually enter the body through the mouth or skin.

Parasites that enter through the mouth are swallowed and can remain in the intestine or burrow through the intestinal wall and invade other organs.

Parasites that enter through the skin bore directly through the skin or are introduced through the bites of infected insects (called vectors because they convey or transmit organisms that cause disease).

Some parasites enter through the soles of the feet when a person walks barefoot or through the skin when a person swims or bathes in contaminated water.

Rarely, parasites are spread through blood transfusion, through injections with a needle previously used by an infected person, or from a pregnant woman to her fetus.

Key definitions

• Eukaryote: a cell with a well-defined chromosome in a membrane-bound nucleus; all parasitic organisms are eukaryotes

• Protozoa: unicellular organisms, e.g. Plasmodium (malaria)• Metazoa: multicellular organisms, e.g. helminths (worms)

and arthropods (ticks, lice)• Parasitisum- a relationship in which one of the participants,

the parasite, either harms its host or in some sense lives at the expense of the host

• Zoonosis animal’s diseases which can be transmitted to man, animal can be wild and/or domestic (these animals infected with parasites are called reservoir hosts)

• Obligate (permanent) parasites – organisms that for all or most of their life cycle are parasitic; they have at least one host during their life-history

• Temporary (intermittent) parasites – agents that are parasitic for limited periods for either feeding or reproduction

• Facultative parasites – organisms that are not normally parasitic but can survive for a limited period when they accidentally find themselves within another organism

• Adaptive parasites – those organisms that have capacity to live both as free-living or parasitic organisms

Parasite, can be:- Microparasites / Macroparasites Endoparasites / Ectoparasites Intracellular parasites (mostly microscopic) Extracellular

parasites (they range in size from micro- to macroscopic)

Life cycle

Life cycle is the process of a parasite’s growth, development and reproduction.

-Direct life cycle one host .

-Indirect life cycle more than one host Infective stage is a stage when a parasite can invade human

body and live in it Infective route is the specific entrance through which the

parasite invades the human body Infective mode means how the parasite invades human body,

such as:

1. the cercariae of the blood fluke actively penetrate the skin of a swimming man

2. the infective Ascaris eggs are swallowed by man

Host

Host - in parasitism, it supplies the parasite with nutrition and shelter, it is the injured partner

Carrier - a person who harbours parasite, has no clinical symptoms, is an important source of infection in epidemiology

Definitive host - in which the parasite reaches sexual maturity and the adult form

Intermediate host - in which the immature or larval form , or in which the parasite undergoes asexual reproduction

Transport host - one in which the parasite does not undergo any development but it remains alive and infective to another host

Reservoir host - any animal that harbors an infection and can transmitted to humans, even if the animal is a normal host of the parasite.

Host parasite relation ship

• Parasitisum is a type of symbiotic relationship between organisms of different species, the parasite benefits at the expense of the host, we have different type include:

1-Commensalism: the association of two different species or organism in which one is benefited and the other is neither benefited nor harmed. (e.g. non pathogenic intestinal protozoa)

2-Mutilisim :an association in which both partners are metabolically dependent upon each other and one cannot live without the help of the other; however, none of the partners suffers any harm from the association. the relation is benefit to both associates. (e. g. E.coli in small intestine)

3-Pathogensim : association where one of the partners is harmed and the other lives at the expense of the other. E.g. Worms like Ascaris lumbricoides

Classification of parasite

Classification of parasite

Parasites can be classified in several ways. They can be grouped according to the site in which

they normally are found; for example, intestinal parasites, blood parasites, or ectoparasites

Or they can be grouped according to morphological characteristics; for example, worms (tapeworms, roundworms, and flukes), protozoa, and arthropods (insects and arachnids).

linnaeus system classification

Classification

The animal kingdom has been divided into two subkingdoms;

Protoza

Metazoa