Title page for ETD etd-01222009-134158

Type of Document Dissertation
Author Nieto, Prixia
Author's Email Address pnieto1@lsu.edu
URN etd-01222009-134158
Title Ecological Risk Models for Visceral Leishmaniasis in Bahia, Brazil and Diagnosis of Trypanosoma cruzi Infection in Dogs in South Central Louisiana
Degree Doctor of Philosophy (Ph.D.)
Department Pathobiological Sciences (Veterinary Medical Sciences)
Advisory Committee
Advisor Name Title
John B. Malone Committee Chair
Lane Foil Committee Member
Patricia Dorn Committee Member
James H. Diaz Committee Member
Don R. Labonte Dean's Representative
  • GIS
  • Visceral leishmaniasis
  • Trypanosoma cruzi
  • Diagnosis of Chagas Disease in Dogs
  • Niche models
Date of Defense 2008-12-19
Availability unrestricted
Three predictive models were developed within a geographic information system using earth observing satellite remote sensing (RS), the Genetic Algorithm for Rule-Set Prediction (GARP) and the growing degree day-water budget (GDD-WB) concept to predict the distribution and potential risk of visceral leishmaniasis (VL) in the State of Bahia, Brazil. The objective was to define the environmental suitability of the disease as well as to obtain a deeper understanding of the eco-epidemiology of VL by associating environmental and climatic variables with disease prevalence. The RS, the GARP model and the GDD-WB model, using different analysis approaches and with the same human prevalence database, predicted similar distribution and abundance patterns for the Lutzomyia longipalpis-Leishmania chagasi system in Bahia. When applied to the ecological zones of Bahia, all three approaches indicate that the highest VL risk is in the interior region of the state, characterized by a semi-arid and hot climate known as Caatinga, while the risk in the Bahia interior forest and the Cerrado ecological regions is lower. The Bahia coastal forest was predicted to be a low-risk area due to unsuitable conditions for the vector and VL transmission.

In a second study in Louisiana, dogs considered to be at high risk of infection with Trypanosoma cruzi, were tested serologically using the indirect fluorescent antibody test (IFAT). Serum samples obtained from a total of 122 dogs from three kennels, and from client dogs from local veterinary practices tested by IFAT revealed a prevalence rate of 22.1%. Fifty randomly selected samples from this group were also tested using two rapid experimental immunochromatographic assays designed as alternative or complementary diagnostic tests for T. cruzi infection. Of the fifty samples tested thirteen animals tested positive using rapid assay A and eleven animals tested positive using rapid assay B. In the same group, 11 animals tested positive by IFAT. The sensitivity of rapid assay A and B were 100%; the specificity of rapid assay A was 95%, and rapid assay B was 100% as compared to the IFAT, the test standard. Clinico-pathological reports revealed that cardiac signs are the main indicators of Chagas disease.

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