Sarcocystis Toxoplasma Tissue Cysts Forming Coccidia Sarcocystis and

Sarcocystis & Toxoplasma Tissue Cysts Forming Coccidia

Ø Sarcocystis and Toxoplasma exhibit a heteroxenous life cycle (more than one obligatory host). Ø The sexual reproduction (gametogony & sporogony) takes place in the intestinal epithelium of the definitive host (carnivores) and asexual reproduction (merogony or schizogony) takes place in tissues of the intermediate host (herbivores).

ØThe life cycle within the carnivore is similar to the life cycles of intestinal coccidia such as Isospora & Cryptosporidium involving sexual cycle (gametogony) within the intestinal epithelial cells. Ø Omnivores, such as humans serve as both intermediate and definitive host in Sarcocystis infection.

Sarcocystis • Rare human infection • Heteroxenous parasite (2 hosts) • humans support both stages • Taxonomic confusion • generally named after host species • Sarcocystis bovihominis or huminis (cattle - intestinal ) • Sarcocystis suihominis (pig - intestinal ) • Sarcocystis lindmanni (muscular cysts= sarcocysts)

Sarcocystis huminis (coccidiosis huminis) S. suihominis (coccidiosis suihominis)

Intestinal Disease • Caused by S. huminis & S. suihominis • ingest undercooked meat of beef or pork (meat transmitted parasite) • Sexual stages (sporogony & gametogony) occur in definitive host (human). • Asexual stage (schizogony or merogony) occur in intermediate host (beef or pork) • transient mild to severe diarrhea • Human excrete sporulated sporocysts

Pathology of S. huminis & S. suihominis intestinal symptoms (abdominal discomfort, nausea, and diarrhea Diagnosis: finding the characteristic sporocysts and occasionally oocysts in feces.

Epidemiology Human acquire intestinal sarcocystosis from eating Sarcocystis-infected meat (meat transmitted infection) S. hominis and S. suihominis are complete their life cycles in specific intermediate hosts. For example, sporocysts in human feces of S. hominis infect cattle but not pigs whereas

Control Cooking or freezing meat to kill bradyzoites (merozoites) in the sarcocysts. Prevent animal from ingesting the sporocyst stage from human feces in contaminated water, feed, and bedding

Sarcocystis lindemanni (Sarcocystoisis or Tissue Cysts Forming Coccidia) §Proposed for all intramuscular sarcocysts in humans §Human is the intermediate host (asexual stages of life cycle-merogony or schizogony occur within human) §Predator of nonhuman primates is the final host (sexual stages of life cycle- gametogony and sporogony )

Sarcocystis lindemanni (Sarcocystosis or Tissue Cysts Forming Coccidia) §Ingestion of the sporocysts by humans will result in the formation of sarcocysts (soil transmitted parasite) §These sarcocysts are generally several 100 µm in size and cause little tissue damage.

S. hominis and S. suihominis

Sarcocystis lindemanni Non human primates

Muscle Disease • Sarcocystis infections in human have been documented, but are rare. • Most hosts do not show any clinical sign or symptoms. • Most sarcocysts in humans have been found in skeletal muscle and cardiac muscle.

• These sarcocysts (Meisher's tubes) are several 100 µm, compartments and sometimes with thick striated wall. • The most common pathological alterations observed are myositis, hemorrhages of heart and serosa, edema, necrosis and hemorrhages of lymph nodes. • Clinical symptoms can include episodic painful inflammatory swellings.

Diagnosis : bradyzoites in muscle biopsy specimens can be identified by microscopic examination Treatment: There is no known specific treatment for the muscle stages. Control: personal hygiene

Toxoplasma gondii • cosmopolitan distribution • seropositive prevalence rates Definitive Host vary • adult forms • generally 20 -75% • generally causes very benign • sexual reproduction disease in immunocompetent Intermediate Host adults • tissue cyst forming coccidia • immature forms • asexual • predator-prey life cycle reproduction • felines are definitive host • infects wide range of birds and mammals including man (intermediate hosts)

Life Cycle in Felines

Life Cycle in Felines • fertilization within infected host cells • immature oocysts in feces • sporulation in soil environment (1 -4 d)

Tachyzoite Stage • ingestion of oocysts • sporozoites penetrate intestinal epithelium • rapid intracellular replication (any cell) • dissemination via macrophages

Tachyzoite Stage • merogony 'merozoites' • typical apicomplexan • motile invasive stages • intracellular replication • 'binary fission' = endodyogony

Tachyzoite Stage • repeated rounds of merogony • acute stage infection • primarily in reticuloendothelial cells

Bradyzoite Stage • dormant, slowly replicating • due to host immune response • chronic or latent infection • tissue cysts primarily in brain and muscle

Life cycle of T gondii

Toxoplasmosis in immunocompetent: ÜToxoplasmosis in adults and children past the neonatal stage is usually benign and asymptomatic. ÜAcquisition of the infection via either oocysts or tissue cysts results in an acute infection in which tachyzoites are disseminated throughout the body via the lymphatic and hematogenously. ÜThis acute stage will persist for several weeks as immunity develops.

ÜBoth humoral and cellular immunity are important, but the cellular response appears critical for the conversion from acute (i. e, tachyzoites) to chronic (i. e, bradyzoites) infection. ÜWhen symptoms do occur they are generally mild and typically described as mononucleosis-like with chills, fever, headache, myalgia, fatigue and swollen lymph nodes.

Congenital Toxoplasmosis • 1 o infection must occur during or shortly before pregnancy • can only occur once • 1/3 will pass infection to fetus • incidence ~1 per 1000 births • severity varies with age of fetus • more severe in early in pregnancy • more frequent later in pregnancy • infection can result in: spontaneous abortion, still birth, premature birth, or full-term ± overt disease

• typical disease manifestations include: retinochoroiditis, psychomotor disturbances, intracerebral calcification, hydrocephaly, microcephaly

Toxoplasmic Encephalitis ØNoted as an opportunistic infection in regards to reactivation of latent infections due to immunosuppression associated with organ transplants and certain cancer treatments and AIDS patients. ØEarly symptoms of toxoplasmic encephalitis can include headache, fever, lethargy, and altered mental status.

Ocular Toxoplasmosis • Originally the ocular manifestations were more often associated with congenital infections (develop weeks to years after birth) or a late manifestation due to the reactivation of a congenital infection.

Diagnosis • various serological tests • active (acute) vs chronic infection • compare samples at 2 week intervals • Ig. M > Ig. G; Ab titers • direct parasite demonstration • Sabin-Feldman dye test • biopsy • inoculation into mice or cell culture (only acute stage) • Imaging techniques: • MRI • computed tomography (CT) scanning

Treatment • Recommended: anti-folates (pyrimethamine + sulfadiazine). • Spiramycin for infection during pregnancy.

Epidemiology: • Serologic prevalence data indicate that toxoplasmosis is one of the most common of human’s infections throughout the world. • Oocysts can survive in the environment for several months and are remarkably resistant to disinfectants, freezing, and drying, but are killed by heating to 70°C for 10 minutes.

Transmission of T. gondii

CONTROL Cook meat thoroughly (66 C) wear gloves when handling meat washing vegetables and fruits very well control strays cats