MICROPARA - MODULE 5

Parasitology

Study of parasites, their hosts, and the relationship between them

Parasite

Organism that lives on or within another organism (host), deriving nutrients at host’s expense

Host

Organism that harbors the parasite

Definitive Host

Host in which a parasite reaches sexual maturity and reproduces

Intermediate Host

Host that harbors the immature or asexual stages of a parasite

Reservoir Host

Animal host that maintains the parasite and serves as a source of human infection

Vector

Arthropod or other organism that transmits a parasite from one host to another

Mechanical Vector

Vector that transmits parasite without parasite development (e.g., housefly)

Biological Vector

Vector in which parasite undergoes development or multiplication before transmission (e.g., mosquito)

Obligate Parasite

Parasite that cannot live without a host

Facultative Parasite

Parasite that can exist as free-living or parasitic organism

Ectoparasite

Parasite that lives on the surface of the host (e.g., lice, ticks)

Endoparasite

Parasite that lives inside the host (e.g., protozoa, helminths)

Protozoa

Unicellular eukaryotic parasites; classified by locomotion (flagella, cilia, pseudopodia)

Trophozoite

Active, feeding, motile stage of protozoa

Cyst

Dormant, resistant stage of protozoa; helps survival outside host

Amoeba

Protozoa that move by pseudopodia (e.g., Entamoeba histolytica)

Entamoeba histolytica

Amoeba that causes amoebic dysentery

Flagellates

Protozoa that move by flagella (e.g., Giardia lamblia, Trichomonas vaginalis)

Giardia lamblia

Flagellate causing giardiasis (diarrheal illness)

Trichomonas vaginalis

Flagellate causing trichomoniasis; transmitted sexually

Trypanosoma

Flagellated protozoan transmitted by tsetse fly; causes African sleeping sickness

Leishmania

Flagellated protozoan transmitted by sandfly; causes leishmaniasis

Ciliates

Protozoa that move by cilia (e.g., Balantidium coli)

Balantidium coli

Only ciliate known to cause disease in humans; causes balantidiasis

Apicomplexa

Non-motile protozoa; obligate intracellular parasites with apical complex for host invasion

Plasmodium

Apicomplexan protozoan causing malaria; transmitted by Anopheles mosquito

Plasmodium falciparum

Most severe species of malaria-causing parasite

Toxoplasma gondii

Apicomplexan parasite causing toxoplasmosis; cats are definitive host

Cryptosporidium

Apicomplexan parasite causing diarrhea via contaminated water

Helminths

Multicellular parasitic worms (flatworms and roundworms)

Flatworms

Platyhelminthes; include trematodes (flukes) and cestodes (tapeworms)

Trematodes

Flukes; leaf-shaped flatworms with complex life cycles (e.g., Schistosoma)

Schistosoma

Blood fluke causing schistosomiasis

Cestodes

Tapeworms; intestinal parasites with scolex and proglottids

Taenia solium

Pork tapeworm; causes taeniasis and cysticercosis

Taenia saginata

Beef tapeworm; causes taeniasis

Echinococcus granulosus

Tapeworm causing hydatid disease

Roundworms

Nematodes; cylindrical worms with complete digestive system

Ascaris lumbricoides

Large intestinal roundworm; causes ascariasis

Enterobius vermicularis

Pinworm causing enterobiasis; common in children

Trichuris trichiura

Whipworm causing trichuriasis

Ancylostoma duodenale

Hookworm causing anemia by feeding on intestinal blood

Necator americanus

Hookworm common in the Americas; causes anemia

Trichinella spiralis

Roundworm causing trichinellosis; transmitted via undercooked pork

Wuchereria bancrofti

Filarial worm transmitted by mosquitoes; causes lymphatic filariasis (elephantiasis)

Onchocerca volvulus

Filarial worm transmitted by blackfly; causes river blindness (onchocerciasis)

Dracunculus medinensis

Guinea worm; transmitted by drinking contaminated water

Arthropods

Invertebrates with exoskeleton; many serve as vectors for parasitic diseases

Pediculus humanus capitis

Head louse; ectoparasite causing pediculosis

Pediculus humanus corporis

Body louse; vector of epidemic typhus

Phthirus pubis

Pubic louse; ectoparasite causing pediculosis pubis

Sarcoptes scabiei

Mite causing scabies by burrowing into skin

Vector Control

Public health measures to reduce or eliminate transmission of parasitic diseases

Antihelminthic Drugs

Medications used to treat helminth infections (e.g., mebendazole, albendazole)

Antiprotozoal Drugs

Medications used to treat protozoal infections (e.g., metronidazole, chloroquine)