INTROD TO PARASITOLOGY 1.pptx

INTROD TO PARASITOLOGY/ CLASSIFICATION Medical Parasitology is the study of invertebrate animals capable of causing disease in humans and other animals. PARASITES OCCUR IN 2 DISTINCT FORMS • Single – celled Protozoa • Multicellular Metazoa called Helminths or Worms SUB-DIVISIONS OF PROTOZOA • •...

INTROD TO PARASITOLOGY/ CLASSIFICATION Medical Parasitology is the study of invertebrate animals capable of causing disease in humans and other animals. PARASITES OCCUR IN 2 DISTINCT FORMS • Single – celled Protozoa • Multicellular Metazoa called Helminths or Worms SUB-DIVISIONS OF PROTOZOA • • • • Sarcodina (Amebas) Sporozoa (Sporozoans) Mastigophora (flagellates) Ciliata (Ciliates) SUB-DIVISIONS OF METAZOA • Phylum Platyhelminthes (flatworms) • Phylum Nemahelminthes (Roundworms or Nematodes). • Phylum Platyhelminthes contains 2 medically important classes: • Cestoda (tapeworms) • Trematoda (flukes). MED IMPT INTESTINAL PROTOZOA • Entamoeba histolytica (ameba) • Giardia lamblia (flagellate) • Cryptosporidium (sporozoan) ENTAMOEBA: Epidemiology & Pathogenesis/Mode of Transmission • DISEASE: Amebic dysentry & Liver abscess • E. histolytica infection is found worldwide • Occurs most frequently in tropical countries especially in areas with poor sanitation. • Disease is widely prevalent among male homosexuals • Organism is acquired by ingestion of cysts • Transmission is primarily by the fecal-oral route (contaminated food and water) CONT. • Anal-oral transmission occurs among male homosexuals. • Ingested cysts differentiate into trophozoites in the ileum but tend to colonize the cecum & colon • Trophozoites invade the colonic epithelium & secrete enzymes that cause localized necrosis • The most frequent site of systemic disease is the liver, where abscesses form LIFE CYCLE/IMPORTANT PROPERTIES • Has 2 stages, motile ameba (trophozoite) and nonmotile cyst • After ingestion, the cyst pass through the stomach. • Upon excystation in the intestinal tract, ameba with 4 nuclei emerges & divides to form 8 trophozoites • Trophozoites produce extensive local necrosis in the large intestine • Trophozoite is found within the intestinal/ extraintestinal lesions and in diarrheal stools • Cysts predominates in nondiarrheal stools/ killed by boiling, not chlorination/removed by filtration of water • Encystatation occurs in the rectum CLINICAL FINDINGS • • • • • • • • • • • INTESTINAL AMEBIASIS Abdominal pain Cramping Colitis with diarrhea Numerous bloody stools per day in severe disease EXTRAINTESTINAL AMEBIASIS Fever, leukocytosis, rigors Liver involvement Lungs, brain and heart involvement Secondary bacterial infection etcs LABORATORY DIAGNOSIS • Identification of trophozoites and cysts in stools • Identification of trophozoites in tissues • Specific serologic test (Indirect hemagglutination test) • Microscopic examination of abcess material • Polymerase chain reaction/DNA-probe assay for the detection of pathogenic strains of E. histolytica. TREATMENT, PREVENTION & CONTROL • Treatment: Metronidazole (flagyl), iodoquinol, paromomycin. • Avoiding fecal contamination of food and water • Adequate sanitation measures and education • Chlorination & filtration of water supplies • High-risk sexual behavior should be avoided GIARDIA LAMBLIA (DUODENALIS) • • • • • • • • • • • • • • • DISEASE: Giardiasis EPIDEMIOLOGY: Worldwide distribution Acquired by: Consumption of inadequately treated contaminated water Ingestion of contaminated uncooked vegetables/ fruits Person to person spread by the fecal-oral route Person to person spread by oral-anal route Children in day-care centers Patients in mental hospitals RISK FACTORS Poor sanitary conditions Consumption of inadequately treated water Travel to endemic areas Oral-anal sexual practices PATHOGENESIS/ CLINICAL FINDINGS • Infection is initiated by ingestion of cysts • Minimum infective dose for humans (10-25 cysts). • Gastric acid stimulates excystation with the release of trophozoites in the duodenum & jejunum • Organisms multiply by binary fission • Trophozoite attach to intestinal villi by ventral sucking disk • Metastatic spread of disease beyond the GIT is rare • CLINICAL FINDINGS: • Nonbloody, foul-smelling diarrhea with nausea, anorexia, flatulence and abdominal cramps. LIFE CYCLE/ LAB DIAGNOSIS • Life cycle is in 2 stages: trophozoite & cyst • Trophozoite is pear-shaped with 2 nuclei, 4 pairs of flagella and a suction disk. • The oval cysts is thick-walled with 4 nuclei and several internal fibers • Each cyst gives rise to 2 trophozoites during excystation • Diagnosis : Presence of trophozoites or cysts or both in diarrheal stools • Presence of cysts in formed stools of asympomatic carriers • Entero-Test or string test • Immunological tests TREATMENT, PREVENTION & CONTROL • DRUG OF CHOICE: Metronidazole with furazolidone, tinidazole or quinacrine. • Avoiding fecal contamination of food and water • Adequate sanitation measures and education • Chlorination & filtration of water supplies • High-risk sexual behavior should be avoided • Maintenance of properly functioning filtration systems in municipal water supplies TRICHOMONAS (UROGENITAL PROTOZOA) • DISEASE: Trichomonas vaginalis causes trichomoniasis • IMPORTANT PROPERTIES: • T. vaginalis exists only as a trophozoite • Its pear-shaped with a central nucleus & 4 anterior flegella • Has an undulating membrane that extends about two-thirds of its length • Its found in the urethras & vaginas of women and in the urethras & prostate of men EPIDEMIOLOGY/ PATHOGENESIS • Parasite has worldwide distribution • Sexual intercourse is the primary mode of transmission • Infants may be infected by passage through the mother’s infected birth canal • Symptomatic disease is highest among sexually active women and lowest in postmenopausal women CLINICAL FINDINGS/ LAB DIAGNOSIS • Most women are asymptomatic or have a scant, watery vaginal discharge accompanied by itching, burning and painful urination • Men are primarily asymptomatic carriers who serve as reservoirs for infections in women • Men occasionally experience urethritis, prostatitis etc • LAB DIAGNOSIS: Microscopic examination of vaginal or urethral discharge for trophozoites Stained Giemsa or unstained smears can be examined Serological test in epidemiologic surveillance Monoclonal fluorescent antibody staining/ Nucleic acid probe assay. TREATMENT, PREVENTION & CONTROL • Drug of choice is metronidazole. • Male & female sex partners should be treated to avoid reinfection • Personal hygiene • Avoidance of shared toilet articles & clothing • Safe sexual practices