title: Re-visiting Trichuris trichiura intensity thresholds based on anemia during pregnancy.
abstract: BACKGROUND
  The intensity categories, or thresholds, currently used for Trichuris trichiura (ie. epg intensities of 1-999 (light); 1,000-9,999 epg (moderate), and ≥ 10,000 epg (heavy)) were developed in the 1980s, when there were little epidemiological data available on dose-response relationships. This study was undertaken to determine a threshold for T. trichiura-associated anemia in pregnant women and to describe the implications of this threshold in terms of the need for primary prevention and chemotherapeutic interventions.
  
  
  RESULTS
  In Iquitos, Peru, 935 pregnant women were tested for T. trichiura infection in their second trimester of pregnancy; were given daily iron supplements throughout their pregnancy; and had their blood hemoglobin levels measured in their third trimester of pregnancy. Women in the highest two T. trichiura intensity quintiles (601-1632 epg and ≥ 1633 epg) had significantly lower mean hemoglobin concentrations than the lowest quintile (0-24 epg). They also had a statistically significantly higher risk of anemia, with adjusted odds ratios of 1.67 (95% CI: 1.02, 2.62) and 1.73 (95% CI: 1.09, 2.74), respectively.
  
  
  CONCLUSIONS
  This analysis provides support for categorizing a T. trichiura infection ≥ 1,000 epg as 'moderate', as currently defined by the World Health Organization. Because this 'moderate' level of T. trichiura infection was found to be a significant risk factor for anemia in pregnant women, the intensity of Trichuris infection deemed to cause or aggravate anemia should no longer be restricted to the 'heavy' intensity category. It should now include both 'heavy' and 'moderate' intensities of Trichuris infection. Evidence-based deworming strategies targeting pregnant women or populations where anemia is of concern should be updated accordingly.
authors.affiliation: Parasite Epidemiology Research Group, Division of Clinical Epidemiology, Research Institute of the McGill University Health Centre, Montreal, Canada. theresa.gyorkos@mcgill.ca
authors.forename: Theresa W
authors.initials: TW
authors.lastname: Gyorkos
authors.forename: Nicolas L
authors.initials: NL
authors.lastname: Gilbert
authors.forename: Renée
authors.initials: R
authors.lastname: Larocque
authors.forename: Martín
authors.initials: M
authors.lastname: Casapía
authors.forename: Antonio
authors.initials: A
authors.lastname: Montresor
mesh_terms: D000740:Anemia / Q000175:diagnosis*; D000818:Animals; D001774:Blood Chemical Analysis; D005260:Female; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D010568:Peru; D011247:Pregnancy; D015597:Pregnancy Complications, Parasitic / Q000473:pathology*; D012720:Severity of Illness Index; D014257:Trichuriasis / Q000473:pathology*; D014258:Trichuris / Q000472:pathogenicity*
chemical_list: D006454:Hemoglobins