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Blastocystis subtypes in symptomatic and asymptomatic family members and pets and response to therapy

R Nagel1, L Cuttell, C R Stensvold

  • 1School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia. robynnagel@tgclinic.com.au

Internal Medicine Journal
|October 29, 2011
PubMed
Abstract

Insights

Conventional therapy failed to clear Blastocystis infections in symptomatic patients. The parasite frequently transmits between humans and pets within households, indicating a need for new treatment strategies.

Area of Science:

  • Medical Parasitology
  • Infectious Diseases
  • Gastroenterology

Background:

  • Blastocystis is a common enteric parasite with uncertain pathogenicity.
  • Blastocystis subtypes (ST) 1 and 3 are suspected to cause irritable bowel-like symptoms.

Purpose of the Study:

  • To evaluate the efficacy of conventional therapy for symptomatic Blastocystis infections.
  • To determine Blastocystis clearance and carriage rates in patients and asymptomatic household members.
  • To analyze subtype (ST) prevalence and transmission within households.

Main Methods:

  • A longitudinal, prospective case study involving 11 symptomatic Blastocystis-positive patients.
  • Patients received either metronidazole or trimethoprim/sulfamethoxazole for 14 days.
  • Faecal specimens analyzed via smear, culture, and 16S small-subunit (SSU) ribosomal DNA (rDNA) polymerase chain reaction (PCR) in patients, household contacts, and pets.

Main Results:

  • No patients cleared Blastocystis following conventional therapy; subtypes 1, 3, 4, and 6 were prevalent.
  • Identical Blastocystis STs were observed in patients before and after treatment.
  • High Blastocystis prevalence and ST concordance were found in household contacts (94%) and pets (88%).

Conclusions:

  • Conventional therapy is ineffective against symptomatic Blastocystis infections.
  • High rates of Blastocystis infection within households suggest human-to-pet transmission.
  • 16S SSU rDNA subtyping alone may not predict Blastocystis pathogenicity.

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