L2 Protazoa Flashcards
Transmission of Protozoa?
- Faecal-oral
- Vector-borne
- Direct
Diagnosis of Protozoal Infections?
Intestinal
CANNOT GRAM STAIN
Stool microscopy (3 samples on 3 consecutive days)
Antigen detection in stool
PCR
Extraintestinal/Tissue
Serology
Histopathology
PCR
List the protozoal infections that are of special importance in the immunocompromised host?
Toxoplasma Gondii
Cryptosporidium Parvum
Giardia Lamblia
Protozoal infections that are of special importance in the immunocompromised host?
Risk Groups?
Toxoplasma Gondii (HIV/Transplant )
Cryptosporidium Parvum (HIV)
Giardia Lamblia
Isospora belli (HIV, HTLV-1,
ALL, Lymphoma)
Cyclospora cayetanensis (HIV)
Microsporidia (HIV/Transplant )
Life Cycle/Human Acquisition of Toxoplasma Gondi?
Life Cycle
Cat is reservoir host, passes oocysts in feces
Other animals may act as intermediate hosts
Acquisition of Human Infection
Ingestion of undercooked meats from intermediate host
Ingestion of oocysts from cat faeces
Less Commonly
Transplacental
Blood transfusion, organ transplantation (uncommon)
Presentation/Reactivation risks of Toxoplasmosis in HIV?
30% risk of reactivation (if not on prophylaxis)
* HIV+
* CD4 < 100
* Toxoplasma IgG positive
CNS most common site of reactivation
Extra-cerebral infection
* Chorioretinitis
* Hepatitis
* Pulmonary infection
Clinical Presentation of Toxoplasma CNS infection?
Subacute onset
Meningitis caused by bacteria/virus (Acute)
Manifests as:
Headache
Confusion
Fever
Focal neurological deficits
Seizures
Altered mental status
Diagnosis of CNS disease in HIV?
- Compatible clinical syndrome
- ≥ 1 mass lesion on brain imaging
MRI > CT
Ring enhancing lesions, usually multiple - Detection of organism in brain biopsy
OR
- CD4 < 100
- Toxoplasma IgG positive
- Not on effective prophylaxis
- Typical appearance on brain imaging
CSF in Toxoplasmosis?
Elevated WCC (lymphocytes)
Elevated protein
Risk/Manifestation of Toxoplasmosis in Transplant?
Highest risk in heart transplant
Manifests as:
Myocarditis, encephalitis, pneumonitis
May have disseminated disease
Prevention/Treatment of Toxoplasmosis?
Prevention
Primary infection
* Avoid contact with cat faeces – hand hygiene
* Consume well-cooked meat
* Wash fruit and vegetables
* Pre-transplant – check serostatus
* Matching of seronegative recipient, if possible
Prophylaxis with Cotrimoxazole
* HIV – when CD4 < 100
* Transplant – if high risk (D+, R-)
Treatment
Pyrimethamine and sulfadiazine (add folinic acid to prevent hematological toxicity)
Duration – 6 weeks
Followed by chronic suppressive therapy while immunocompromised
Life Cycle of Cryptosporidium Parvum
1) Thick walled oocyst exits host (sporulated) through GIT
2) Contamination of water/food with oocytes
3) Ingested by hos
4) Wall breakdown within host => watery diarrhea
Clinical Features of Cryptosporidium Parvum vs. Giardia Lamblia
Cryptosporidium Parvum
Watery diarrhea (Weight loss with chronic diarrhea)
Anorexia, nausea, malaise
Low grade fever
Crampy abdominal pain
Biliary tract infection, pancreatitis in HIV
Giardia Lamblia
Asymptomatic
Acute diarrhoea
Chronic diarrhoea – malabsorption/ weight loss
Diagnosis of Cryptosporidium Parvum
Visualization of parasite
* Modified acid-fast stain
* Immunofluorescent antibody
Not detected by routine Ova and Parasites exam
Multiple samples (Intermittent shedding)
Prevention/Management of Cryptosporidium Parvum
Prevention
Good hygiene
Avoid exposure to water from lakes, streams, swimming pools
Resistant to chlorination!!
(Filter/Boiling removes cysts from water, not chlorination)
Management
Nitazoxanide, Paromomycin
Supportive
Reduction of immunosuppression
Notify Public Health
