Parasitic Infections: An Overview of Protozoan and Helminthic Diseases
Parasitic Infections: An Overview
Protozoan Infections
Giardia lamblia
Giardia lamblia causes giardiasis, characterized by mucous diarrhea, bloating, abdominal pain, and anorexia. Infection occurs through ingestion of cysts, which rupture in stomach acid, releasing trophozoites in the duodenum and jejunum. Transmission is via fecal-oral route, often through contaminated water and vegetables.
Trichomonas
Trichomonas vaginalis causes trichomoniasis, a urogenital infection. T. tenax resides in the mouth, while T. hominis exists only as a trophozoite.
Trypanosoma
Trypanosoma brucei and T. brucei rhodesiense cause African trypanosomiasis. T. cruzi, found in the feces of the Triatoma bug (kissing bug), enters through bite wounds. Tripomastigotes migrate to the heart, liver, and brain, transforming into intracellular amastigotes. Acute infection presents with fever, chills, myalgia, and asthenia, potentially leading to death. Chronic infection can cause hepatosplenomegaly, myocarditis, and esophageal and colonic hypertrophy.
Toxoplasma gondii
Toxoplasma gondii completes its life cycle in the intestinal cells of cats. Transmission to humans occurs through consuming raw meat from infected animals, ingesting oocysts from cat feces, or via transplacental transfer. The parasite can affect the lungs, heart, lymphoid tissue, and central nervous system. Diagnosis is typically through ELISA.
Plasmodium
Four Plasmodium species cause malaria: P. vivax (benign tertiary malaria), P. ovale (benign tertian malaria), P. malariae (benign quartan malaria), and P. falciparum (malignant tertian malaria). P. falciparum is the most dangerous, capable of invading any red blood cell and causing severe complications like blackwater fever, coma, and death.
Helminthic Infections
Ascaris lumbricoides
Ascaris lumbricoides is a nematode transmitted through ingestion of contaminated food or water. Larvae migrate from the intestines to the liver, heart, and lungs, maturing in the alveoli. Symptoms include coughing, peritonitis, and pneumonitis. Ascariasis is one of the most common human infections.
Enterobius vermicularis (Pinworm)
Enterobius vermicularis is transmitted through ingestion of eggs. Symptoms include itching, fatigue, and local inflammation. Diagnosis is typically through the Graham sticky tape test.
Trichinella spiralis
Trichinella spiralis causes trichinosis, transmitted through ingestion of raw or undercooked meat. Larvae encyst in muscles, causing fever, myalgia, and ocular alterations. Severe cases can involve the heart or CNS.
Taenia solium (Pork Tapeworm)
Taenia solium is a tapeworm acquired by consuming undercooked pork. It can cause taeniasis (intestinal infection) and cysticercosis (tissue infection).
Taenia saginata (Beef Tapeworm)
Taenia saginata is a tapeworm acquired by consuming undercooked beef. It causes intestinal infection.
Echinococcus granulosus
Echinococcus granulosus is a small tapeworm whose eggs are shed in dog feces. Humans are intermediate hosts, developing hydatid cysts in organs like the liver and lungs. Diagnosis includes imaging and serological tests.