Type of infection
Toxoplasmosis (toxo) is an illness caused by a protozoa.
Toxo is mainly transmitted by eating raw or under-cooked meat, or through exposure to cat faeces that is more than 1 day old.
Many adults have been exposed to toxo. But there is usually a risk of illness only when CD4 levels are below 200 cells/mm3.
If untreated, toxo can be fatal.
Toxo usually affects the brain (toxoplasma encephalitis). Symptoms include:
- Disorientation, confusion.
- Memory loss.
- Vision loss.
- Behaviour change.
Toxo can affect organs, including the eyes and lungs.
Diagnosis is difficult. Blood tests for antibodies, and even viral load tests in CSF (cerebrospinal fluid) are not always positive. Brain scans can highlight any damage to the brain, but rarely provide enough information to diagnose the cause of the damage.
Symptoms are often sufficient to start treatment. If symptoms improve within 2 weeks then toxoplasmosis will have been the cause. A brain scan will show reduced damage within 3 weeks.
- Treatment with the antibiotics pyrimethamine, sulphadiazine, folinic acid for six weeks, followed by maintenance therapy. This is usually effective and straight forward.
- If there is a bad reaction to sulphadiazine, then clindamycin is preferred.
- Co-trimoxazole alone (Trimethoprim-sulphamethoxazole, TMP-SMX) or atovaquone combined with sulphadiazine or pyrimethamine can be used but they are supported by less evidence,
- UK (BHIVA) guidelines include recommending a biopsy of there is no clinical improvement within two weeks.
After a successful response to treatment (usually three weeks) maintenance therapy is continued with low dose pyrimethamine plus either sulphadiazine or clindamycin. This is called secondary prophylaxis.
Treatment is life-long while CD4 count remains below 200.
Treatment can be safely stopped sometimes if ART increases the CD4 count over 200. This also depends on the severity of the previous illness.
Primary prophylaxis is when treatment is used to prevent an initial infection. It is recommended in all people living with HIV who have a CD4 count under 200.
- The first option is co-trimoxazole (Septrin, Bactrim, TMP-SMX) – Co-trimoxazole is made up of two drugs trimethoprim (TMP) and sulphamethoxazole (SMX).
- For people who can not tolerate co-trimoxazole, either atovaquone or dapsone are options. Sometimes these are used with pyrimethamine.
The drugs used to protect against toxo also protect against PCP.
Secondary prophylaxis, is when a treatment is used to prevent a second bout of infection (see treatment section above).
Research and links
Alternative antibiotics like azithromycin and doxycycline are being studied.
- BHIVA guidelines: Treatment of opportunistic infection in HIV-seropositive individuals (2011) – Chapter 2.5 Toxoplasmosis
Last updated: 1 January 2023.