Pathogenic Blastocystis at a Glance

NAME:  Pathogenic Blastocystis

PHYLOGENETIC DESIGNATION:

Domain/Superkingdom                    Protista
Kingdom                                            Stramenopile
Phylum                                                Sarcomastigophora
Order                                                  Amoebida (or Blastocystea)
Family                                                 Blastocystidae
Genus                                                 Blastocystis
Species                                              TBD

METHOD OF TRANSMISSION: Fecal-Oral

SYMPTOMS: Symptomatic diagnosis can be difficult due to the range of symptoms reported.   

GASTROINTESTINAL:
           Diarrhea^{16 19 20 22}, Constipation^{20 22}, Abdominal Pain^{16 20 22}, Weight Loss²¹

NEUROLOGICAL: Fatigue^{20 21 22}, Depression⁴², Headaches⁴²

INFLAMMATORY: Skin Rash^{25 26 43 44}, Joint Pain^{23 24 45}        

EPIDEMIOLOGY:

* Italy^{25 30 31 32 33 34 35} and the Middle East^{16 20 21 22 36}  contribute many case reports.

* Risk factors for contracting the disease in Oregon (US) are use of well water, canoeing, hiking in undeveloped areas.³⁷

VECTORS: The epidemiology is consistent with transmission from an animal.  Human to human transmission is possible as well.

ECONOMIC AND SOCIAL IMPACT: Most patients interviewed described reductions in quality of life, most often from fatigue and pain.  Some patients described substantial loss of earning ability, partial to complete disability, and mental health issues that commenced with the onset of the infection.

INVASIVENESS: Blastocystis has been reported in synovial fluid and in joints.^{24 45} The skin rash reported by patients may be analogous to the rash caused by invasive Entamoeba histolytica.  

DETECTION: Research labs can use sensitive and selective tests for identifying symptomatic Blastocystis infection.  Existing clinical methods are neither sensitive nor selective.  PCR primers already reported could serve as a basis for the development of a PCR assay.

DETECTION (RESEARCH LAB METHODS): 

1.      Serum Antibody Testing has been found to be both sensitive and selective.^{3 4}  Reagents are not commercially available and must be custom made.

2.      Stool Culture has been found to be sensitive and selective when performed properly.²

3.      PCR Identification:  The following primers have been reported in a study on Malaysian, Australian, and Pakistani isolates.¹  The primers have not been corroborated. 
           D1       1.3 kbp           5′-ACCGCGAAGG-3′
           A10     850 bp            5′-GTGATCGCAG-3′
           B5       920 bp            5′-TGCGCCCTTC-3′ (B5 is shared by commensal B.
                                                 hominis)

4.      Fluorescence: The possible use of the fluorescent properties of Blastocystis is explored in a supporting presentation available from the Foundation.

TREATMENT: Use of Metronidazole and TMP/SMX has been reported.¹⁶  A high failure rate (80%) is associated with heavily infected patients.  The amoebic form is non-motile, which may provide it with an unusual method of antibiotic resistance.  Some success has been reported with triple antibiotic treatment.³⁸  In choosing to treat patients with single antibiotic treatments, doctors and patients should weigh the possibility that this may render a combined antibiotic treatment ineffective at a later date.

MISCELLANEOUS TESTING RESULTS:

 * Blood test have shown a lowered white blood cell count.³⁹

 * Serum tests have shown lowered magnesium levels.⁴⁰

 * Findings from Endoscopy /Colonoscopy are unremarkable.⁴¹

^REFERENCES

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This web site is for information only and is not meant to be used for self-diagnosis or as a substitute for consultation with a health care proider regarding Blastocystis hominis.  If you have any questions about the disease described above or think that you may have a parasitic infection, consult a health care provider.