Affects: Cats
Toxoplasmosis is a parasitic disease caused by Toxoplasma gondii, an apicomplexan. Infections with toxoplasmosis are associated with a variety of neuropsychiatric and behavioral conditions. Occasionally, people may have a few weeks or months of mild, flu-like illness such as muscle aches and tender lymph nodes. In a small number of people, eye problems may develop. In those with a weakened immune system, severe symptoms such as seizures and poor coordination may occur. If a woman becomes infected during pregnancy, a condition known as congenital toxoplasmosis may affect the child.
Toxoplasmosis is usually spread by eating poorly cooked food that contains cysts, by exposure to infected cat feces, or from an infected woman to her baby during pregnancy. Rarely, the disease may be spread by blood transfusion or other organ transplant. It is thought to not otherwise spread between people, but broader transmissibility remains a matter of scientific debate. Studies have reported the presence of T. gondii in human semen and have proposed sexual transmission as a possible route, though this has not been established as a primary mode of spread. The parasite is only known to reproduce sexually in the cat family. It can infect most types of warm-blooded animals, including humans. Diagnosis is typically by testing blood for antibodies or by testing the amniotic fluid in a pregnant patient for the parasite's DNA.
Prevention is by properly preparing and cooking food. Pregnant women are also recommended not to clean cat litter boxes or, if they must, to wear gloves and wash their hands afterwards. Treatment of otherwise healthy people is usually not needed. During pregnancy, spiramycin or pyrimethamine/sulfadiazine and folinic acid may be used for treatment.
Signs And Symptoms: Infection has three stages:
Transmission: Toxoplasmosis is generally transmitted through the mouth when Toxoplasma gondii oocysts or tissue cysts are accidentally eaten. Congenital transmittance from mother to fetus can also occur. Transmission may also occur during the solid organ transplant process or hematogenous stem cell transplants.
Oral transmission may occur through:
Ingestion of raw or partly cooked meat, especially pork, lamb, or venison containing Toxoplasma cysts: Infection prevalence in countries where undercooked meat is traditionally eaten has been related to this transmission method. Tissue cysts may also be ingested during hand-to-mouth contact after handling undercooked meat, or from using knives, utensils, or cutting boards contaminated by raw meat.
Ingestion of unwashed fruit or vegetables that have been in contact with contaminated soil containing infected cat feces.
Diagnosis: Toxoplasmosis in humans is diagnosed through biological, serological, histological, or molecular methods, or by some combination of the above. Toxoplasmosis can be difficult to distinguish from several other conditions, especially ones that are common in HIV/AIDS and immunocompromised patients, and can cause central nervous system problems and brain lesions. Toxoplasmosis is most commonly mistaken for primary central nervous system lymphoma, both conditions cause lesions in the brain, but in about 50-80% of cases the lesions appearances can be very similar on imaging, and exist in an area of the brain that makes biopsying too risky, however the main difference is lymphoma typically causes a single lesion in the subependymal region, and toxoplasmosis causes multiple lesions scattered through the basal ganglia. Other conditions that can present as toxoplasmosis on a differential diagnosis are metastatic brain lesions, progressive multifocal leukoencephalopathy, CNS tuberculosis, bacterial or fungal brain abscess, cytomegalovirus (CMV), and herpes simplex encephalitis.
T. gondii may also be detected in blood, amniotic fluid, or cerebrospinal fluid by using polymerase chain reaction. T. gondii may exist in a host as an inactive cyst that would likely evade detection, with some studies finding evidence that latent toxoplasmosis (in non-HIV patients) might play a role in causing mental disorders like schizophrenia, Alzheimer's and Parkinson's.
Serological testing can detect T. gondii antibodies in blood serum, using methods including the Sabin–Feldman dye test (DT), the indirect hemagglutination assay, the indirect fluorescent antibody assay (IFA), the direct agglutination test, the latex agglutination test (LAT), the enzyme-linked immunosorbent assay (ELISA), and the immunosorbent agglutination assay test (IAAT).
Treatment: Treatment is recommended for people with serious health problems, such as people with HIV whose CD4 counts are under 200 cells/mm3. Trimethoprim/sulfamethoxazole is the drug of choice to prevent toxoplasmosis, but not for treating active disease. A 2012 study shows a promising new way to treat the active and latent form of this disease using two endochin-like quinolones.