Toxoplasma gondii FOR MEDICAL PARASITOLOGY

THIS TOPIC FOR MEDICAL PARASITOLOGY STUDENTS

1. Toxoplasma gondii

2. Introduction: Toxoplasma gondii  is an intestinal coccidium ( Coccidia are  protozoal organisms of the phylum Apicomplexa , members of which are obligatory intracellular parasites. Coccidia spp. have a complex life-cycle in which sexual and asexual reproduction occurs in gastrointestinal enterocytes .) that parasitizes members of the cat family as definitive hosts and has a wide range of intermediate hosts. Infection is common in many warm-blooded animals, including humans. In most cases infection is asymptomatic, but devastating disease can occur.

3. Prevalence: The prevalence of Toxoplasma gondii (T. gondii ) varies by region and population group:  Global : The estimated global seroprevalence rate for T. gondii is 25.7%, but the range can be as low as 0.5% or as high as 87.7%.  United States and United Kingdom : The prevalence rate is estimated to be around 8–22%.  Europe, South America, and Central America : The prevalence rate is estimated to be between 30–90%.  Nepal : A study found that the prevalence of T. gondii in sheep in Nepal was 36.17%, with the highest prevalence in Chitwan at 57.65%.

4. Geographical distribution: Toxoplasma gondii is a parasite that is found worldwide, from tropical to arctic ecosystems. However, the distribution of the parasite's strains varies by geographical location: Archetypal strains These strains are mainly found in the Northern Hemisphere. In Europe, the clonal lineages Type II and Type III are most common. In North America, a fourth clonal lineage ( haplogroup 12) and other atypical genotypes are more prevalent. Atypical strains These strains are mainly found in South America, where there is a high diversity of genotypes

5. Mode of infection: Toxoplasma gondii is a protozoan parasite that can infect humans and other warm-blooded animals in several ways:  Eating contaminated food Eating raw or undercooked meat or shellfish that contains tissue cysts, or consuming food or water contaminated with cat feces or other environmental samples  Drinking contaminated milk Consuming unpasteurized milk, especially goat's milk 

6. Contact with contaminated soil Children may become infected by ingesting oocysts in dirt or sandpit sand contaminated by cat feces  Blood transfusion or organ transplant Toxoplasmosis can be transmitted through blood transfusions and organ transplants  Transplacental transmission A mother can pass toxoplasmosis to her fetus if she becomes infected during pregnancy 

7. Habitat: Toxoplasma gondii is a protozoan parasite that can be found in almost every habitat on Earth, from the Arctic to deserts, and in cities and isolated islands. It can be found in water, soil, vegetables, and seafood. Toxoplasma gondii is a parasite that can be found in a variety of habitats, including: Cat feces : Cat feces can contaminate water, soil, and outdoor areas where cat feces can be found.  Raw or undercooked meat : Tissue cysts of Toxoplasma gondii can be found in raw or undercooked meat, especially pork and lamb.  Unwashed fruits and vegetables :  Toxoplasma gondii can be found in unwashed fruits and vegetables. 

8. Dust :  Toxoplasma gondii can be found in dust.  Toxoplasma gondii is a protozoan parasite that can infect most warm-blooded animals, including humans. The only known definitive hosts for Toxoplasma gondii are members of the cat family, such as domestic cats.  Humans can become infected with Toxoplasma gondii in several ways, including: Eating undercooked meat from animals harboring tissue cysts Consuming food or water contaminated with cat feces Blood transfusion or organ transplantation Transplacentally from mother to fetus 

9. Life cycle: T. gondii has a complex life cycle that involves two hosts: a definitive host, usually a cat, and an intermediate host, which can be any warm-blooded animal. The parasite spreads through a combination of environmental contamination Eggs are passed in cat stool. Many eggs are passed but usually for only 1 to 2 weeks. After 1 to 5 days in the environment, eggs become able to cause infection. Cats can become reinfected by consuming food or other materials contaminated with the eggs. Other animals (such as wild birds, rodents, deer, pigs, and sheep) may consume the eggs in contaminated soil, water, plant material, or cat litter.

10. Shortly after the eggs are consumed, they release forms of the parasite that can move (called tachyzoites ). Tachyzoites spread throughout the animal's body and form cysts in nerve and muscle tissue. Cats become infected after eating animals that contain these cysts. People can become infected by eating undercooked meat containing these cysts. People can also become infected if they eat food, water, or other materials (such as soil) contaminated with cat stool or when they touch a pet cat's litter and then touch their mouth. Rarely, people are infected when they have a blood transfusion or organ transplant that contains the parasite. Rarely, the infection is spread from mother to fetus. In people, parasites form cysts in tissues, usually in muscle and the heart, brain, and eyes

11. Pathogenesis: The pathogenesis of Toxoplasma gondii is a complex process that involves the parasite's ability to invade cells, evade the immune system, and persist in the body:  Invasion T. gondii invades host cells through a series of stages, including recognizing surface receptors, gliding, and forming a moving junction. The parasite then penetrates the host cell and forms a parasitophorous vacuole (PV) where it asexually replicates.  Evasion T. gondii can evade the immune system and spread to other parts of the body, including the liver, spleen, and central nervous system. 

12. Latency When the host's immune system develops, T. gondii multiplication stops and the parasite forms tissue cysts, called bradyzoites , that can remain dormant for years. These cysts can reactivate if the host's immunity is impaired, such as in people with AIDS.  Symptoms Most infections with T. gondii are subclinical, but some people can develop acute toxoplasmosis. Symptoms include fever, malaise, lymphadenopathy , and central nervous system pathology.  T. gondii is a parasite that's common in birds and mammals. People typically get infected by eating food or drinking water that's been contaminated with the parasite, which can come from cat feces. It causes Toxoplasmosis

13. Laboratory diagnosis: Laboratory tests for toxoplasmosis, or infection with Toxoplasma gondii , can include: Serologic tests These tests detect antibodies specific to Toxoplasma in the blood, such as IgG , IgM , IgA , or IgE . Some examples of serologic tests include:  Dye test (DT)  Indirect fluorescent antibody test (IFA)  Enzyme immunoassays (ELISA, immunoblots )  Agglutination test  Avidity test 

14. Molecular techniques These techniques detect the parasite's genetic material, such as with polymerase chain reaction (PCR).  Isolation of the parasite This can be done from blood or other body fluids by inoculation into mice or tissue culture.  Histologic demonstration This can be done by immunoperoxidase stain.  Other tests that may be used to diagnose toxoplasmosis include: Piezoelectric immunoagglutination assay (PIA) and Latex agglutination test (LAT).  A healthcare provider may also perform a physical exam, ask about symptoms, and order imaging, a lumbar puncture, or a biopsy. 

15. Prevention and control of: some ways to prevent and control toxoplasmosis: Cook meat thoroughly : Use a food thermometer to ensure meat is cooked to a safe internal temperature:  Whole meats and fish : Cook to at least 145° F (63° C) and let rest for at least three minutes  Ground meat : Cook to at least 160° F (71° C)  Whole and ground poultry : Cook to at least 165° F (74° C)  Wash hands and utensils : Wash hands with soap and water after handling raw meat, and wash utensils with hot, soapy water after preparing each food item  Wash fruits and vegetables : Wash all fruits and vegetables thoroughly before eating, especially salad vegetables 

16. Wear gloves : Wear gloves when gardening or touching soil or sand that may be contaminated with cat feces  Clean litter boxes : Clean cat litter boxes daily to remove feces before they become infectious  Cover sandboxes : Cover outdoor sandboxes to prevent cats from using them as litter boxes  Avoid unpasteurized goat's milk : Do not drink unpasteurized goat's milk or products made from the milk  Avoid raw shellfish : Do not eat raw oysters, mussels, or clams  Avoid untreated water : Do not drink untreated water, especially during pregnancy