Toxoplasmosis – Part 1 – Diagnosis and Treatment

• Toxoplasmosis is caused by the protozoan parasite called Toxoplasma gondii.

Sample

1. Blood to prepare the serum.
2. Store the blood at 2 °C to 6 °C if the test is delayed for more than 7 days.
3. Serum should not be heat-inactivated, because this may give false-positive results.

Spread

1. This is present worldwide in humans and domestic animals. This is also seen in wild animals.
2. In human spread is by the half-cooked meats that contain the cyst,
3. If there are infective oocyst from the contaminated cat feces.
4. Spread through blood transfusion is also possible.

Presentation

1. If there is an infection in utero in the early stage then there are possibilities of the death of the fetus, brain damage, hydrocephaly.
   1. The infected fetus will have fever, splenomegaly, jaundice,  and convulsion at birth.
2. Infection in late pregnancy can lead to mild disease.
3. Immune-deficient patients may have Chorioretinitis, pneumonia, lymphadenopathy, myocarditis, and possible death. 

Laboratory Diagnosis

1. Cultures can be done and it needs long incubation. 
2. In body fluids, tissue, and blood the presence of Tachyzoites are confirmatory.
3. Immunoperoxidase or Fluorescent techniques can be done.
4. Antibody dependants tests are diagnostic for toxoplasmosis. IgM antibody appears roughly after 5 days of the infection. This is suggestive of intrauterine infection.
   1. IgM titer lasts up to one year.
   2. IgM antibody can be found in the cord blood.
   3. Polymerase chain reaction (PCR) is highly specific and sensitive.  

Source 2

1. 1. Serology of Toxoplasmosis
      1. IgG antibody titer represents present or past infection.
      2. IgM antibody is needed to confirm the present infection.
         1. Antibody IgM titer <1:16  =  shows no exposure to virus.
         2. Antibody IgM titer >1:4 to 1:256  = acquired infection in last 18 months.
         3. Antibody IgM >1: 1024  = Acquired infection in last 4 months

Toxoplasma antibody interpretation:

IgG antibody	IgM antibody	Interpretation
Negative	local evidence of toxoplasmosis infection
Negative	Positive	Positive for early  infection or false positive so repeat the test
Positive	Negative	Past infection 6 months or more
Positive	Positive	Positive recent infection within the last 12 months

             

Treatment

• Sulfadiazine, Pyrimethamine, and folic acid are given.

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