Toxoplasmosis

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | References

Definition

Toxoplasmosis is an infection caused by the protozoan parasite Toxoplasma gondii. It can affect most warm-blooded animals, including humans, and is particularly concerning in pregnant women and immunocompromised individuals.

Aetiology

Toxoplasmosis is caused by Toxoplasma gondii. The infection is typically acquired through:

• Ingestion of undercooked or contaminated meat
• Consumption of food or water contaminated with oocysts shed in the faeces of infected cats
• Transplacental transmission from an infected mother to her unborn child
• Organ transplantation or blood transfusion from an infected donor

Pathophysiology

The pathophysiology of toxoplasmosis involves:

• Ingestion of Toxoplasma gondii oocysts or tissue cysts
• Parasite invasion and multiplication within host cells
• Formation of tissue cysts in muscles, brain, and other organs
• Activation of the immune response, which can control but not eradicate the infection

Risk Factors

• Consumption of undercooked meat, especially pork, lamb, and venison
• Exposure to cat faeces, particularly through litter boxes or contaminated soil
• Drinking untreated water
• Living or working in environments with poor sanitation
• Immunocompromised individuals (e.g., HIV/AIDS, chemotherapy)
• Pregnancy

Signs and Symptoms

The signs and symptoms of toxoplasmosis vary depending on the individual's immune status and may include:

• Asymptomatic in most healthy individuals
• Flu-like symptoms: fever, fatigue, muscle aches, and swollen lymph nodes
• Ocular toxoplasmosis: blurred vision, eye pain, and redness
• Congenital toxoplasmosis: miscarriage, stillbirth, or birth defects such as hydrocephalus, microcephaly, and chorioretinitis
• Severe disease in immunocompromised individuals: encephalitis, seizures, confusion, and other neurological symptoms

Investigations

Specific investigations to diagnose toxoplasmosis include:

• Serology: Detection of IgM and IgG antibodies against Toxoplasma gondii.
• Polymerase Chain Reaction (PCR): To detect Toxoplasma DNA in blood, amniotic fluid, or other body fluids.
• Ophthalmological examination: To identify lesions typical of ocular toxoplasmosis.
• Imaging: CT or MRI scans of the brain in cases of suspected cerebral toxoplasmosis.
• Histopathology: Biopsy of affected tissues in severe or atypical cases.

Management

Primary Care Management

• Observation: Most healthy individuals do not require treatment and should be monitored for symptoms.
• Antibiotics: For symptomatic individuals or those with significant risk factors, a combination of pyrimethamine and sulfadiazine, along with folinic acid, is used.
• Preventive measures: Educating patients on proper food handling, cooking meat thoroughly, and avoiding exposure to cat faeces.

Specialist Management

• Hospitalisation: For severe cases, particularly those involving the central nervous system or in immunocompromised individuals.
• Treatment during pregnancy: Spiramycin is used to reduce the risk of transmission to the fetus; if fetal infection is confirmed, pyrimethamine and sulfadiazine are considered.
• Management of complications: Addressing complications such as seizures, vision loss, and other organ-specific issues.
• Regular follow-up: Monitoring for potential relapse, particularly in immunocompromised individuals.

References

1. NHS (2024) Toxoplasmosis. Available at: https://www.nhs.uk/conditions/toxoplasmosis/ (Accessed: 24 June 2024).
2. Centers for Disease Control and Prevention (2024) Toxoplasmosis. Available at: https://www.cdc.gov/parasites/toxoplasmosis/index.html (Accessed: 24 June 2024).
3. World Health Organization (2024) Toxoplasmosis. Available at: https://www.who.int/news-room/fact-sheets/detail/toxoplasmosis (Accessed: 24 June 2024).
4. British Medical Journal (2024) Toxoplasmosis: clinical features, diagnosis, and management. Available at: https://www.bmj.com/content/350/bmj.h2362 (Accessed: 24 June 2024).

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