Coccidian Parasites: Toxoplasma Gondii

Coccidian Parasites include the parasites such as Toxoplasma Gondii, Cryptosporidium, Cyclospora, Isospora, and Sarcocystis.

Toxoplasma Gondii

The Definitive Host for Toxoplasma Gondii is Cats. The definitive host is where the Oocyst is formed or Sexual Reproduction occurs. The Intermediate Host is where the rest of the lifecycle occurs. The intermediate host of Toxoplasma Gondii is Humans. However, it could be any other animal, such as sheep, rodents, pigs, etc.

The Infective Forms of toxoplasma are 

• Sporulated Oocyst
• Tachyzoites
• Bradyzoites

The Mode of Transmission for the disease is by:

• Blood Transfusion: Tachyzoites are transmitted through blood 
• Ingestion: A sporulated oocyst can be inhaled through contaminated soil, food, or water. Bradyzoites occur through undercooked meat.

Tachyzoites multiply actively, and Bradyzoites multiply slowly.

Congenital toxoplasmosis

Congenital toxoplasmosis is more severe for pregnant females, especially in Trimester 1, as the organogenesis is taking place at that time. However, it is more common in Trimester III, during vaginal delivery. The Conditions experienced by the patients are:

• Chorioretinitis
• Cerebral Calcification
• Convulsions
• Microcephaly
• Hydrocephalus
• Mental Retardation

Adult Toxoplasmosis( immunocompetent)

Toxoplasmosis is mostly Asymptomatic in adults. The most common symptom is painless inflammation of cervical LN. For immunocompromised adults, like In the case of an HIV+ individual, Encephalitis is seen, and the most commonly affected organ is the Brain Stem.

In BMT patients, Pneumonia is seen. The chest X-ray shows Bilateral Ground Glass Opacities. The Giemsa stain shows Chyzoites in the CSF or BAL sample to confirm the disease.

Diagnosis of Toxoplasmosis Gondii

• IgM- acute infection (they fall down slowly)
• IgA/E- acute infection (they tend to fall down faster than IgM)
• IgG- chronic infection (life-long antibody)

The gold standard for Toxoplasmosis is the Sabin Feldman test, which is a type of complement fixation test (CFT).

Treatment of Toxoplasmosis Gondii

Pyrimethamine + sulfadiazine (Folinic acid)

Similarities and Differences between CMV (Cytomegalovirus) and Congenital Toxoplasmosis

The similarities between CMV (Cytomegalovirus) and Congenital Toxoplasmosis include:

• Chorioretinitis
• Microcephaly 
• Mental Retardation. 

The major difference between CMV and congenital Toxoplasmosis is that CMV possesses Periventricular Calcification, while Congenital Toxoplasmosis possesses Cerebral Calcification and Convulsions.

Cryptosporidium

Cryptosporidium has small infectivity dose. Cysts can survive chlorination of H2O. Cryptosporidium is associated with autoinfection.  

Lifecycle of Cryptosporidium

• Transmission of Cryptosporidium parvum occurs through exposure to infected animals or exposure to water contaminated by the feces of infected animals ..
•  Following ingestion, excystation occurs. The sporozoites are released and hide in the tunnel, known as Parasitophorous vacuoles, which hide along the brush border cells of  GIT.
• In these cells, the parasites develop that sporulated oocyst in the infected host.
•  Two different types of oocysts are produced: the thick-walled, which is commonly excreted from the host, and the thin-walled oocyst, which is primarily involved in autoinfection. 

Cyclospora and Isospora

They have unsporulated oocysts in feces, so it does not cause autoinfection. Cyclospora is associated with raspberry consumption.

Difference between Cryptosporidium, Cyclospora and Isospora

Also Read: Miscellaneous Pathogenic Bacteria

Frequently Asked Questions:

Question- What type of Toxoplasma gondii transfer via organ transplant?

Answer- Bradyzoite, since they are a tissue.

Question- HIV-positive person presented with diarrhea. A stool examination revealed a round acid-fast cyst with an 8-12 micron diameter. What is the Diagnosis?

1. E coli
2. E Histolytica
3. Cryptosporidium
4. Cyclospora

Answer- d. Cyclospora

Question- Parasitophorous vacuole is suggestive of?

1. Cryptosporidium
2. Isospora
3. Cyclospora
4. Giardia

Answer- a. Cryptosporidium

Question- The oocyst shown below is depictive of?

1. Cryptosporidium
2. Isospora
3. Cyclospora
4. Giardia

Answer- c. Cyclospora

Question- A person who has recently consumed a box of raspberries came down with severe watery diarhhoea. What is the most likely diagnosis?

1. Cyclospora
2. Cryptosporidium
3. Isospora
4. Vibrio

Answer- a. Cyclospora

Question- Sabin Feldman test is used for?

1. Leishmania
2. Malaria
3. Toxoplasma
4. Trypanosoma

Answer- c. Toxoplasma

Question- Which of the following is not a coccidean?

1. Cyclospora
2. Isospora
3. Cryptosporidium
4. Entamoeba coli

Answer- d. Entamoeba coli.

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