About parasites

Protozoans parasites

In five kingdom system of classification,the kingdom Protista is divided into three major groups

1. Photosynthetic protists
2. Slime moulds and
3. Protozoans Protista

Protozoans Protista is one of the groups of the kingdom Protista.

Protozoans are classified according to how they move and these are four types

• Mastigophoran: Which moves with a long whip-like extension called a flagellum.The flagellum beats or rotates in the water to move protozoans about.
• Cilliophorians: They have numerous cilia which beat in unison like oars to propel through the water.Often cilia are fused together in rows or tufts and are use for special functions such as food gathering.In addition to locomotion,the paramecium uses cilia to sweep food down into gullet.
• Scarcodinians: It includes Amoebas that have pseudopods to move.
• Sporozoans: They are very small spore-like organisms without locomotory structures.

In a two-kingdom system of classification protozoans, Protists is regarded as phylum protozoa.

Characteristics of Protozoan Parasite

1. They are unicellular and microscopic.
2. Most protozoans exist in two forms i.e trophozoite and cyst.Trophozoite is the motile and feeding form of parasite whereas the cyst is inactive form.
3. Organs of motility are different in different protozoans For eg some possesses cilia some possess pseudopodia some possess flagella for motility.
4. In many protozoan cytoplasms is divided into outer ectoplasm and inner endoplasm.
5. In some protozoans,there are two types of a nucleus.One is macronucleus and other is micronucleus.

Disease caused by protozoans

• Amoebiasis: It is also known as amoebic dysentery which is caused by Entamoeba histolytic .The infective stage of Entamoeba histolytic is the quadrinucleate cyst.Infection generally occurs through drinking contaminated water.The trophozoites of Entamoeba Histolytica penetrates the wall of the colon,secrets the histolytic enzymes and feeds upon its cells causing ulcers.These ulcers rupture and discharge mucus and blood into the intestine that passes along with stool and results in amoebic dysentery.If the infection is allowed to continue the para site may reach the liver,lungs, and brain where it causes abscesses which are fate to the human.Drinking water vegetable and fruits with faecal contamination are the primary cause of transmission of amoebiasis.Amoebiasis is endemic in tropic countries.It can be treated with metronidazole,tinidazole etc.
• Giardiasis:nIt is caused by Giardia lamblia.It is transmitted by ingestion of cyst from contamination food and water.It affects small intestine.Symptoms include mal-absorption of food.
• Balantidiasis: It is caused by Basidium Coli.It is transmitted by ingestion of cyst.It is transmitted by ingestion of cyst.It affects large intestine.Symptoms include diarrhea.dysentry etc.
• Tertian or Vivax malaria: It is caused by plasmodium Vivax.It is transmitted by biting of female anopheles mosquito which injects sporozoites into the blood.It affects the RCB and liver cell.Symptoms include fever,headache etc.
• Urethritis/Vaginitis: It is transmitted by transfer of trophozoites during sexual contacts.It affects vagina and urethra.Symptoms include inflammation of vagina and urethra.

Nematoda parasite

Nematodes are among the most numerous of any phylum.It is the heterogeneous assemblage of different animals.Their classification is difficult due to much diversity in form and structureChitwood divided the phylum Nematoda into two classes;Phasmidia and Aphasmida,on the basis of presence or absence of plasmids(caudal sensory organs).

Characteristics of Nematode parasite

1. They have elongated body with point ends.
2. Body is surrounded by noncellular cuticle which prevents them from digestive enzymes of host
3. They have the complete digestive system which is adapted for ingestion of host cell,host RCB,host nutrition etc.
4. The body contains longitudinal muscles on the wall that permits penetration of parasite into host tissue.
5. Eggs and all form of the larva of nematodes are well adapted to survive in the external environment and in various intermediate hosts.

Disease caused by Nematodes:

1. Ascariasis: It is caused by Ascaris lumbricoid. Man acquires the infection by ingestion of cyst from contamination food and water.
2. Filariasis: It is caused by Wuchereria Broncrofti. It is transmitted by biting of female anopheles mosquito which injects microfilaria into the blood.
3. Trichuriasis: It is caused by Trichuris Trichiura.
4. Conjunctivitis: It is caused by Loa loa in the conjunctiva of the eye.

Two diseases in plants caused by nematodes are:

• Meloidogyne Species causes root knot disease in vegetables.
• Heterodera Auenae causes Molya diseases in wheat and barley.

Characters of Trematode parasite

1. They are soft-bodied worm commonly called flukes.
2. They are typically flattened and leaf shape or elongated with a pair of suckers.
3. They have a bipartite gut with no anus i.e. incomplete alimentary tract.
4. Fluid possess both longitudinal and circular muscle characteristic of nematode but they lack the cuticle and their body is curved by cellular epithelium.

Diseases caused by trematodes

1. Fascioliasis: It is caused by Fasciola hepatica.
2. Echinostomiasis: It is caused by Echinostoma Ilocanum.

Characters of Cestoda parasite

1. They are also called tapeworm.
2. The body consists of the ribbon-like chain of segments called strobila.
3. Each segments bearing a complete male and female reproductive system.
4. There is no mouth or alimentary tract in instead nutrients are directly absorbed by the hair-like structure called microfiches.At the anterior end, there is scolex with suckers and hooks.It helps in attachment into the host tissue.

Diseases

• Taeniasis: It is caused byTaenia Solium
• Echinococcosis: it is caused by Echinococcus Multilocuris.

References

Arvind, Keshari K. and Kamal K Adhikari. A Textbook of Biology. Vidyarthi Pustak Bhander.

Michael J.Pleczar JR, Chan E.C.S. and Noel R. Krieg. Microbiology. Tata Mc GrawHill, 1993.

Powar. and Daginawala. General Microbiology.

Rangaswami and Bagyaraj D.J. Agricultural Microbiology.