References:
- Global Infectious Diseases and Epidemiology Online Network: Infectious Diseases of the Philippines, 2013 eBook Edition, ISBN 978-1-61755-582-4, by Stephen Berger. Accessed here.
| Agent | PARASITE - Protozoa. Sporozoa, Coccidea, Eimeriida: Toxoplasma gondii |
| Reservoir | Rodent Pig Cattle Sheep Chicken Bird Cat Marsupial (kangaroo) |
| Vector | None |
| Vehicle | Transplacental Meat ingestion Soil ingestion Water or milk (rare) Fly |
| Incubation Period | 1 to 3 weeks (As early as 5 days) |
| Diagnostic Tests | Serology Cultivation or identification of organisms per specialized laboratories Nucleic acid amplification |
| Typical Adult Therapy | Pyrimethamine 25 mg/d + Sulfonamides 100 mg/kg (max 6g)/d X 4w - give with folinic acid. Alternatives: Clindamycin, Azithromycin, Dapsone. Spiramycin (in pregnancy) 4g/d X 4w |
| Typical Pediatric Therapy | Pyrimethamine 2 mg/kg/d X 3d, then 1 mg/kg/d + Sulfonamides 100 mg/kg/d X 4w - give with folinic acid. Alternatives: Clindamycin, Azithromycin, Dapsone. |
| Clinical Hints | Fever, lymphadenopathy and hepatic dysfunction; chorioretinitis; cerebral cysts (patients with AIDS); congenital hydrocephalus, mental retardation or blindness. |
| Synonyms | Toxoplasma, Toxoplasmose, Toxoplasmosi |
Acquired Toxoplasmosis
The clinical features of acquired toxoplasmosis can range from subclinical infection to lymphadenopathy (the most common presentation) to fatal, fulminant disease.
- In healthy adults, infection is usually subclinical, or mimics infectious mononucleosis; however, pharyngitis, posterior and posterior cervical lymphadenopathy are unusual in toxoplasmosis.
- Most patients with acute Toxoplasma lymphadenitis experience fatigue, headache, difficulty concentrating and muscle aches.
- In immunocompromised hosts, toxoplasmosis may mimic other opportunistic infections, such as tuberculosis or infection with P. jiroveci (formerly P. carinii), or extensive varicella.
- In patients with AIDS, CNS involvement is the most common manifestation, followed by pulmonary disease.
Congenital Toxoplasmosis
The rate and severity of congenital toxoplasmosis are largely related to gestational age at the time of infection.
- Overt clinical signs appear to be more common among American infants vs. European infants with congenital toxoplasmosis.
- The brain and eyes are often affected, presenting as chorioretinitis, hydrocephalus, intracranial calcifications, and seizures.
- 97% of children infected during the first trimester of pregnancy and having normal antenatal ultrasounds are asymptomatic or only slightly affected.
- Rare instances of nephrotic syndrome complicating congenital toxoplasmosis have been reported.
Ocular Toxoplasmosis
Ocular toxoplasmosis occurs from reactivation of cysts in the retina.
- Focal necrotizing retinitis is characteristic lesion, and approximately 35% of all cases of retinochoroiditis can be attributed to toxoplasmosis.
- Risk factors for early (first two years of life) retinochoroiditis include a delay of >8 weeks between maternal seroconversion and the beginning of treatment, female gender, and the presence of cerebral calcifications.
- The incidence and severity of ocular toxoplasmosis varies from country to country.
CNS Toxoplasmosis
The manifestations of CNS toxoplasmosis in the immunocompromised patient range from an insidious process evolving over several weeks to acute onset of a confusional state.
- Signs may be focal or symmetrical.
- T. gondii has a predilection to localize in the basal ganglia and brain stem, producing extrapyramidal symptoms resembling those of Parkinson’s disease.
- A normal CT scan does not rule out cerebral toxoplasmosis. MRI is the imaging modality of choice
- Nonfocal evidence of neurological dysfunction may include generalized weakness, headache, confusion, lethargy, alteration of mental status, personality changes, and coma.
- Infection in transplant recipients is often diffuse and disseminated.
- In patients with underlying malignancy (e.g. Hodgkin’s disease), the presentation is evenly distributed between focal and nonfocal forms of encephalitis.