PADMASHREE SCHOOL OF PUBLIC HEALTH

INTRODUCTION TO

PARASITOLOGY

- Dr. Rahul Shrivastava- (BDS, MPH 2nd Sem)

- PARASITOLOGY - The branch of biology or

medicine concerned with the study of parasitic organism.

- PARASITE - An organism which lives in or on another organism (its host) and benefits by deriving nutrients at the other's expense.

SOME TERMINOLOGIES

- PARASITOLOGIST - A scientist who

studies parasites and their biology and pathology, such as the parasitic diseases caused by them (parasitology). Since parasites can be observed in practically all animal and plant phyla, there are specializations for parasitologists (human, veterinary, plant, etc.).

- PARASITISM - A non-mutual symbiotic relationship between species, where one species, the parasite, benefits at the expense of the other, the host.

- PREDATOR – An organism that attack another

living animal, not necessarily killing them (attackers).

- PREY – They are the victims.

- HOST - An animal or plant on or in which a parasite or commensal organism lives.

- Definitive host: Host in which sexual

reproduction takes place . It is mostly a vertebrate.

- Intermediate host: The host in which some development of the parasite occurs but it does not reach sexual maturity, is referred as intermediate host and is usually a invertebrate.

- Paratenic or transport (carrier)host: Sometimes

the parasite enters a host in which it does not undergo any development but remains alive till it gains entry in the definitive host or intermediate host. These hosts are important for the completion of the life cycle of certain parasites as they are believed to bridge the ecological gap between the intermediate and the definitive host.

- Reservoir host:  An organism in which a parasite (that is pathogenic for some other species) lives and multiplies usually without damaging the host. For example, dogs and cats are reservoirs of Leishmania.

- VECTORS – Hosts that transmit parasites to

man.

- BIOLOGIC VECTORS – Those that are essential in the life cycle.

- PHORETIC/MECHNICAL VECTORS – Those that are not essential in the life cycle.

- ZOONOSIS – Disease of animals that are

transmissible to man.

1. Euzoonosis - common to man & reservoir host.2. Parazoonosis – man is infrequent host & incidental.3. Anthropozoonosis – infection acquired by man

from other vertebrates.4. Zooanthroponosis – human infections that may be

acquired by other vertebrates.

HISTORY

- The father of parasitology - Platter

- The Italian Francesco Redi, considered to be the father of modern parasitology, he was the first to recognize and correctly describe details of many important parasites.

- "Humans are hosts to nearly 300 species of

parasitic worms and over 70 species of protozoa, some derived from our primate ancestors and some acquired from the animals we have domesticated or come in contact with during our relatively short history on Earth.”

We are beginning to learn a lot about the past history of parasitic infections from studies of archaeological artifacts, such as the presence of helminth eggs or protozoan cysts and naturally or artificially preserved bodies; from such studies has emerged a new science, palaeoparasitology.

Examples of some of these discoveries will be discussed later.

So vast is the field of human parasitology, and so many and far-reaching the discoveries made, that it is not possible to do justice to the whole subject.Therefore; only the most significant aspects and the most important parasites are considered under two major headings, the helminth worms and the protozoa.

- Medical Parasitology- Agriculture, aquaculture & veterinary

Parasitology- Wildlife & Fisheries Parasitology- Ecological Parasitology- Biochemistry & Molecular Biology of

Parasitology- Immuno Parasitology- Quantitative Parasitology- Structural parasitology- Taxonomy & Phylogenetics

PARASITES

A parasite is an organism that lives on or in a host organism and gets its food from or at the expense of its host. There are three main classes of parasites that can cause disease in humans: 1. Protozoa2. Helminths3. Ectoparasites.

- Protozoa are microscopic, one-celled organisms that

can be free-living or parasitic in nature. - They are able to multiply in humans, which

contributes to their survival and also permits serious infections to develop from just a single organism.

- Transmission of protozoa that live in a human's intestine to another human typically occurs through a feco-oral route (for example, contaminated food or water or person-to-person contact).

- Protozoa that live in the blood or tissue of humans are transmitted to other humans by an arthropod vector (for example, through the bite of a mosquito or sand fly).

PROTOZOA

Entamoeba histolytica A microscope is necessary to view this parasite

- The protozoa that are infectious to humans can be

classified into four groups based on their mode of movement:

1. Sarcodina – the ameba, e.g., Entamoeba2. Mastigophora – the flagellates,

e.g., Giardia, Leishmania3. Ciliophora – the ciliates, e.g., Balantidium4. Sporozoa – organisms whose adult stage is not

motile e.g.,Plasmodium, Cryptosporidium

Classification of Protozoa

- Helminths are large, multicellular organisms

that are generally visible to the naked eye in their adult stages.

- Like protozoa, helminths can be either free-living or parasitic in nature.

- In their adult form, helminths cannot multiply in humans.

HELMINTHS(Warms)

1. Flatworms (platyhelminths) – these include the trematodes

(flukes) and cestodes (tapeworms).2. Thorny-headed worms (acanthocephalins) – the adult forms

of these worms reside in the gastrointestinal tract. The acanthocephala are thought to be intermediate between the cestodes and nematodes.

3. Roundworms (nematodes) – the adult forms of these worms can reside in the gastrointestinal tract, blood, lymphatic system or subcutaneous tissues. Alternatively, the immature (larval) states can cause disease through their infection of various body tissues.

4. Some consider the helminths to also include the segmented worms (annelids)—the only ones important medically are the leeches. Of note, these organisms are not typically considered parasites.

Classification of Helminths

- Although the term ectoparasites can broadly include blood-

sucking arthropods such as mosquitoes (because they are dependent on a blood meal from a human host for their survival), this term is generally used more narrowly to refer to organisms such as ticks, fleas, lice, and mites that attach or burrow into the skin and remain there for relatively long periods of time (e.g., weeks to months).

- Arthropods are important in causing diseases in their own right, but are even more important as vectors, or transmitters, of many different pathogens that in turn cause tremendous morbidity and mortality from the diseases they cause.

ECTOPARASITES

An adult louseAcutal size is about as big as a sesame seed

- Ingestion

- Arthropods bites

- Penetration of intact skin or mucous membranes

MODE OF ENTRY

- Some parasites must migrate to certain

locations within the host in order to complete their life cycle.

- Non-human parasites, in humans, often fail to migrate properly and become “dead-end infections”.

SPREAD OF PARASITES

- http://dictionary.reference.com/browse/parasite- http://www.cdc.gov/parasites/- http://

www.medicinenet.com/script/main/art.asp?articlekey=4769- http://journals.cambridge.org/action/displayJournal?jid=PAR- http://amsocparasit.org/careers/parasitology- http://link.springer.com/journal/436- http://www.journals.elsevier.com/international-journal-for-par

asitology/

- http://parasitology.conferenceseries.com/- http://www.cell.com/trends/parasitology/home- http://www.sciencedirect.com/science/journal/13835769- http://

knowledgeinbiology.blogspot.in/2010/03/father-of-various-branches-of-biology.html

REFERENCES