Modelling the ecological niche of hookworm in Brazil based on climate

Ntombi B. Mudenda, John B. Malone, Michael T. Kearney, Paula D. Mischler, Prixia del Mar Nieto, Jennifer C. McCarroll, Penelope Vounatsou
  • Ntombi B. Mudenda
    Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA, United States | nmuden1@tigers.lsu.edu
  • John B. Malone
    Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA, United States
  • Michael T. Kearney
    Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA, United States
  • Paula D. Mischler
    Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA, United States
  • Prixia del Mar Nieto
    Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA, United States
  • Jennifer C. McCarroll
    Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA, United States
  • Penelope Vounatsou
    Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel; University of Basel, Basel, Switzerland

Abstract

The distribution of hookworm in schistosomiasis-endemic areas in Brazil was mapped based on climate suitability. Known biological requirements of hookworm were fitted to data in a monthly long-term normal climate grid (18 x 18 km) using geographical information systems. Hookworm risk models were produced using the growing degree day (GDD) water budget (WB) concept. A moisture-adjusted model (MA-GDD) was developed based on accumulation of monthly temperatures above a base temperature of 15 °C (below which there is no lifecycle progression of Necator americanus) conditional on concurrent monthly values (rain/potential, evapotranspiration) of over 0.4. A second model, designated the gradient index, was calculated based on the monthly accumulation of the product of GDD and monthly WB values (GDD x WB). Both parameters had a significant positive correlation to hookworm prevalence. In the northeastern part of Brazil (the Caatinga), low hookworm prevalence was due to low soil moisture content, while the low prevalence in southern Brazil was related to low mean monthly temperatures. Both environmental temperature and soil moisture content were found to be important parameters for predicting the prevalence of N. americanus.

Keywords

hookworm, Necator americanus, risk models, growing degree days, water budget, geographical information systems, Brazil.

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Submitted: 2014-12-17 11:16:32
Published: 2012-09-01 00:00:00
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Copyright (c) 2012 Ntombi B. Mudenda, John B. Malone, Michael T. Kearney, Paula D. Mischler, Prixia del Mar Nieto, Jennifer C. McCarroll, Penelope Vounatsou

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