Definition

     Toxoplasmosis is an infection with the protozoan intracellular parasite Toxoplasma gondii. This organism is usually passed on to humans from cat feces. It can cause a variety of different symptoms depending on which part of the body is infected.

Cause

• Human infection results from ingestion of the parasites cysts in raw or undercooked meat, unwashed raw vegetables or other foods. The parasite also spreads through contaminated soil or cat waste.

Symptoms 

     In non-immunosuppressed people:

• mild illness with fever, resembling mononucleosis

• enlarged lymph nodes in the head and neck

• headache

• sore throat

• muscle pain

     In congenital infection:

• central nervous system disorders

• enlarged liver or spleen

• rash, fever, jaundice, anemia

• inflammation of the retina of the eye

• psychomotor and learning disorders (may not appear until later)

     In an immunosuppressed person:

• brain lesions are associated with fever, headache, confusion, seizures, and abnormal neurological findings

• retinal inflammation causing blurred vision

Screening and Diagnostics

     Tests to determine infection or presence of cysts:

• serologic titers for toxoplasmosis

• MRI of head

• cranial CT scan

• brain biopsy

• slit lamp examination reveals characteristic retinal lesions

Treatment

• The drug of choice is Pyrimethamine with either Trisulfapyrimidines or Sulfadiazine.

• Clindamycin is an alternative drug that has proven effective, especially for eye infections.

• Newer drugs are being studied to determine their effectiveness.

• In pregnant women, the drug of choice is Spiramycin.  This drug is not used for other types of infection.

• Anyone on Pyrimethamine should take Folic Acid supplements because of medicine-induced Folic Acid deficiency.

• Not everyone infected needs to be treated.

• Individuals over 5 years of age with normal immune systems do not need to be treated unless symptoms develop.

• Once symptoms of the infection present, treatment will be required until they decrease and blood tests indicate the development of immunity to the disease.  This usually takes about 3-4 weeks.

• Most eye infections heal by themselves.  The best way to treat this type of infection is unclear.  Seek the advice of a specialist.

• All with weakened immune systems who develop the infection need to be treated.  Treatment is usually continued for 4-6 weeks after all symptoms have subsided.  This may require treatment for several months.  Successful treatment will need to be followed up with continued medication to prevent re-infection (prophylaxis)-until the immune system is back to normal.  Those with AIDS, who will never have normal immune systems, will need to be on medicines for the rest of their lives to prevent repeat infections.

• Also, those with weakened immune systems who have evidence of past infection with Toxoplasmosis will need to be placed on medicines to prevent infection from ever occurring.

• Babies who were infected while they were in the uterus should also be treated after birth.

• Pregnant women who develop the infection need to be treated to reduce the chance of the fetus becoming infected.

• The long-term prognosis for infected individuals with normal immune systems is very good, and almost all make full recovery.  Those with weakened immune systems usually do well if treated early-if left untreated, they will likely die from it.

Complications 

• spread of the infection in immunocompromised hosts (can be fatal)

• permanent disability in infants (blindness, learning disorders, and so on)

• recurrence of the disease

Prevention

• Prevention is the most important safeguard.

• The organism can be destroyed by freezing meats to below -20º C for 2 days, or by heating meat to at least 60º C for at least 4 minutes before consuming.  All meats should be thoroughly cooked before eating.

• The organism can remain alive in cat feces for up to a year.  However, for the first 48 hours it is not as infectious.  Cat litter boxes should be cleaned every day.

• Also, every effort must be made to keep cats and dogs out of children's play areas and sandboxes.  Children tend not to be conscientious about washing their hands after playing outdoors or in sand.  They may even eat small amounts of sand or dirt, or put contaminated hands in their mouths.  Therefore, it is very important to take this preventive step in order to try to avoid any infection.  Parents and caretakers need to make every effort to have children wash their hands before eating or touching the mouth or face.

• Thoroughly wash your hands after cleaning the litter box.  Also, wash your hands if you think that any soil you've touched might be contaminated with cat (or dog) feces.  The basic rule is that it is always a good idea to frequently and thoroughly wash your hands.

• Indoor cats should be fed only dry, canned, or cooked meat.

• Pregnant women comprise a special risk group and must be extra careful to avoid spreading infection to the baby.  The easiest and best way to avoid any problems is to stay away from cats and cat litter when pregnant.

• If this is not possible, pregnant women will need to have their blood tested to determine if they have developed immunity to the organism.  The doctor can do the necessary blood tests.

• If a pregnant woman has developed some level of immunity, she will still need to be careful and follow the precautions listed here.

• If she has no immunity, then to be safe she must avoid all cats and cat litter.  She will also need to thoroughly cook all meats, wash her hands after handling uncooked meat, before touching her face, and before eating.

• If she has no immunity but still has contact with cats or cat litter, then other precautionary measures (see above) need to be followed.  In addition, she will need to have her blood checked periodically during pregnancy to make sure not to develop any infection.

• It is very important that pregnant women tell their doctors if they have any cats at home.