Apicomplexa Apicomplexa Apical complex apicoplast Unicellular sporeforming Exclusively

Apicomplexa

Apicomplexa Apical complex= apicoplast Unicellular, spore-forming Exclusively parasites (i. e. , no free-living) Motile structures are absent except in certain gamete stages

Apicomplexa complex life-cycle sexual (sporogony & gametogony) asexual (schizogony or merogony)

Apicomplexan structure

GENERAL APICOMPLEXAN LIFE CYCLE

Apicomplexa Gregarines Piroplasms Babasia Microsporidia Neuplasms COCCIDIA Cryptosporidium Isospora Haemosporina Toxoplasma Plasmodium spp Sarcocystis

Coccidia ÜAre microscopic, spore-forming, single-celled parasites. ÜAre obligate, intracellular parasites (they must live and reproduce within host cells). ÜCoccidiosis is a parasitic disease of the intestinal tract of humans and animals, caused by coccidian protozoa belong to four genera: Cryptosporidium sp. , Isospora belli, Sarcocystis and Toxoplasma gondii).

ÜThe disease spreads from one host to another by contact with infected feces, or ingestion of infected tissue. ÜDiarrhea, which may become bloody in severe cases, is the primary symptom. ÜOnly two species of coccidia known to undergo schizogony and gametogony in man, viz. , Isospora belli & Cryptosporidium.

GENERAL APICOMPLEXAN LIFE CYCLE

ÜThe infective oocysts in species of Isospora belli and Sarcocystis produce two internal sporocysts, each with four sporozoites; in Cryptosporidium the sporocyst stage is omitted. Ücharacterized by thick-walled oocysts excreted in feces

Cryptosporidium cryptosporidiosis

Cryptosporidium • First human case reported in 1976 • Fecal-oral transmission (monoxenous) • Initially it was believed to be a rare and exotic infection. • Now recognized as a common human pathogen and a frequent cause of diarrhea in humans.

Cryptosporidium • Self-limiting diarrhea in immunocompetent persons • Profuse, watery diarrhea associated with AIDS (life threatening) Cryptosporidium parvum, C. muris and C. hominis

feces or respiratory secretions

Life cycle of Cryptosporidium

Cryptosporidium Life Cycle • Merogony • = schizogony • produce merozoites • Gametogony • = gamogony or • = gametocytogenesis • produce micro- and macrogametes • Sporogony • produce sporozoites • completed on host cell • thin (autoinfection) or thick walled oocysts

Extracytoplasmic Location • microvilli extend and fuse to enclose zoite • close association between parasite and host intestinal epithelial cell • called adhesive zone, feeder organelle, etc

PATHOGENESIS ►The most common clinical manifestation of cryptosporidiosis is a mild to profuse watery diarrhea. ►This diarrhea is generally self-limiting and persists from several days up to one month. ►Recrudescences are common.

PATHOGENESIS ►Abdominal cramps, anorexia, nausea, weight loss and vomiting are additional manifestations which may occur during the acute stage. ►The disease can be much more severe for persons with AIDS which manifests as a chronic diarrhea lasting for months or even years.

DIARRHEA • epithelia malfunction (osmotic) • impaired absorption • enhanced secretion • inflammatory diarrhea • mucosal invasion • leukocytes in stools • secretary diarrhea • toxin associated • watery Pathogenesis • Epithelial cells damaged or killed • villus atrophy (blunting) • Na+ absorption • intercellular permeability • crypt cell hyperplasia • Cl- secretion • inflammation in lamina propria • enhanced secretion of antibodies (Ig. A)?

Epidemiology • Fecal- oral disease. • 2 major genotypes identified: • genotype 1= C. hominis • only human sources • non-infective for mice or calves • anthroponotic transmission • genotype 2= C. parvum • human and bovine sources • infective for mice and calves • zoonotic transmission

Factors Favoring Waterborne Cryptosporidiosis • small size of oocysts (4 -5 mm) • reduced host specificity and monoxenous development • close associations between human and animal hosts • large number of oocysts excreted (up to 100 billion per calf per day) • low infective dose (<30) • robust oocysts; resistant to chlorine

Diagnosis demonstration of typically shaped oocysts in stool examination. Treatment §fluid and electrolyte replacement §In immunocompetent persons is selflimited diarrhea Control Improvement in sanitary and hygienic conditions is indicated.

Isospora belli

Isospora belli • wide geographical distribution (higher prevalence in warmer areas) • monoxenous, probably not zoonosis, occurs via the oral-fecal route. • invades intestinal epithelial cells of S. I. and produces self limiting diarrhea in normal individuals.

Isospora belli • symptoms range from mild gastro-intestinal distress to severe dysentery • often self-limiting, but can become chronic (wasting, anorexia) • symptoms more severe in AIDS patients

Life cycle of Isospora belli in soil: sporogony (sexual) end by formation of oocyst containing 8 sporozoites in human intestine: schizogony (asexual)– transformation of sporozoites into schizontes and merozoites gametogony(sexual): transformation of merozoites into male & female gametocytes

Isospora belli (30 x 12 mm oocyts) • 2 sporocysts 4 sporozoites each

Pathology In immunocompetent: acute, non bloody diarrhea crampy abdominal pain can last for weeks and result in malabsorption and weight loss. In immunodepressed patients, and in infants and children, the diarrhea can be severe

Diagnosis Microscopy (demonstration of typically shaped oocysts) Treatment Trimethoprim- is the drug of choice Control Improvement in sanitary and hygienic conditions is indicated.