Medically Important Parasites

Medically Important Parasites

• Parasites are eukaryotes that can be single-celled (protozoa) or multicellular (helminths or worms).
• Protozoa are divided into four groups for medical purposes: Sarcodina (amoebas), Sporozoa (sporozoans), Mastigophora (flagellates), and Ciliata (ciliates).
• Metazoa are subdivided into two phyla: Platyhelminthes (flatworms) with classes Cestoda (tapeworms) and Trematoda (flukes), and Nemathelminthes (roundworms).

Protozoa: Intestinal & Urogenital

• Entamoeba histolytica: Causes amebic dysentery and liver abscess.
• Life cycle has two stages: motile trophozoite and nonmotile cyst.
• Transmission is primarily through the fecal-oral route.
• Giardia lamblia: Characterized by a pear shape, two nuclei, and four pairs of flagella.
• Has a suction disk for attachment to intestinal walls.
• Transmission is also through the fecal-oral route.
• Watery, foul-smelling, nonbloody diarrhea, accompanied by nausea, anorexia, flatulence, and abdominal cramps for weeks/months.
• Trichomonas vaginalis: Causes trichomoniasis.
• Pear-shaped organism with a central nucleus and four anterior flagella.
• Has an undulating membrane.
• Only exists as a trophozoite, no cyst form.
• In women, causes a watery, foul-smelling, greenish vaginal discharge, with itching and burning.
• In men, usually asymptomatic but can cause urethritis in 10% of infected individuals.

Blood & Tissue Protozoa: Malaria

• Malaria is caused by four Plasmodium species: P. vivax, P. ovale, P. malariae, and P. falciparum.
• P. vivax and P. falciparum are most common types.
• Worldwide, it's a common, serious infectious disease, even lethal disease.
• Transmission via female Anopheles mosquito (only the female feeds on blood).
• Life cycle involves sexual and asexual phases.

Blood & Tissue Protozoa: Toxoplasmosis

• Caused by the Coccidian protozoan Toxoplasma gondii.
• Zoonotic disease, infecting a wide variety of animals and birds; does not cause disease in them.
• Humans can acquire the infection transplacentally, leading to spontaneous abortion, stillbirth, or severe mental/physical handicap in the child.

Blood & Tissue Protozoa: Chagas' Disease

• Caused by Trypanosoma cruzi.
• The vector is the reduviid bug (Triatoma, cone-nose or kissing bug).
• The life cycle involves this bug stage as the vector. It ingests blood from the host.

Blood & Tissue Protozoa: Sleeping Sickness

• Caused by Trypanosoma gambiense and Trypanosoma rhodesiense.
• It is also known as African trypanosomiasis.
• Transmitted by the tsetse fly.

Helminths-Trematodes

• Trematoda (flukes) and Cestoda (tapeworms) belong to the phylum Platyhelminthes (flatworms).
• Schistosoma species are important trematodes, causing significant morbidity and mortality.
• Transmission tends to involve water sources, intermediate hosts (e.g., snails) and direct contact with the contaminated water.

Helminths-Cestodes: Tapeworms

• Tapeworms (Cestoda) are flatworms with a head (scolex) and multiple segments (proglottids).
• Ingestion of undercooked meat containing larvae is a common means of transmission, which leads to the infestation of a variety of animals depending on the worms' specific life cycle.

Nematodes

• Nematodes (roundworms) have a complete digestive tract, mouth, and anus.
• The entire body is covered with a cuticle.
• Males are usually bigger than females.
• Medically important nematodes are classified into intestinal and tissue nematodes.
• Intestinal nematodes: Enterobius (pinworm), Trichuris (whipworm), Ascaris (giant roundworm), hookworms (Necator and Ancylostoma), Strongyloides, and Trichinella.
• Tissue nematodes: Wuchereria, Onchocerca, and Loa.

Leishmaniasis

• Caused by Leishmania spp, unicellular, flagellate protozoa, intracellular parasite.
• Transmission involves infected female sandflies (Phlebotomus spp).
• Three main types: cutaneous, visceral, and mucocutaneous.

Other Information

• Important notes regarding the methods of transmission and diagnostic methods regarding the diseases were included within the slides.
• Also, some pictures/images were in the presentations.