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. 2011 Feb 22;5(2):e970.
doi: 10.1371/journal.pntd.0000970.

A history of chagas disease transmission, control, and re-emergence in peri-rural La Joya, Peru

Affiliations

A history of chagas disease transmission, control, and re-emergence in peri-rural La Joya, Peru

Stephen Delgado et al. PLoS Negl Trop Dis. .

Abstract

Background: The history of Chagas disease control in Peru and many other nations is marked by scattered and poorly documented vector control campaigns. The complexities of human migration and sporadic control campaigns complicate evaluation of the burden of Chagas disease and dynamics of Trypanosoma cruzi transmission.

Methodology/principal findings: We conducted a cross-sectional serological and entomological study to evaluate temporal and spatial patterns of T. cruzi transmission in a peri-rural region of La Joya, Peru. We use a multivariate catalytic model and Bayesian methods to estimate incidence of infection over time and thereby elucidate the complex history of transmission in the area. Of 1,333 study participants, 101 (7.6%; 95% CI: 6.2-9.0%) were confirmed T. cruzi seropositive. Spatial clustering of parasitic infection was found in vector insects, but not in human cases. Expanded catalytic models suggest that transmission was interrupted in the study area in 1996 (95% credible interval: 1991-2000), with a resultant decline in the average annual incidence of infection from 0.9% (95% credible interval: 0.6-1.3%) to 0.1% (95% credible interval: 0.005-0.3%). Through a search of archival newspaper reports, we uncovered documentation of a 1995 vector control campaign, and thereby independently validated the model estimates.

Conclusions/significance: High levels of T. cruzi transmission had been ongoing in peri-rural La Joya prior to interruption of parasite transmission through a little-documented vector control campaign in 1995. Despite the efficacy of the 1995 control campaign, T. cruzi was rapidly reemerging in vector populations in La Joya, emphasizing the need for continuing surveillance and control at the rural-urban interface.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. The La Joya, Peru, study area.
The high-resolution satellite image (50-cm resolution panchromatic image acquired by WorldView-1 on 04 September 2008, eMap International) shows the peri-rural landscape of the La Joya study area. The inset map illustrates the proximate locations of the La Joya study site and the city of Arequipa.
Figure 2
Figure 2. Spatial patterns of T. cruzi infection in T. infestans and humans.
Comparisons of spatial distributions of households with T. infestans versus households with T. cruzi-infected insects (top panel); and households with T. cruzi-seropositive humans versus households with T. cruzi-infected insects (bottom panel). To preserve study participant confidentiality while maintaining actual and relative distance and orientation relationships, locations of all households were masked by displacing each point from its original location by a constant increment.
Figure 3
Figure 3. Spatial clustering analysis of T. infestans, T. cruzi-infected T. infestans, and T. cruzi-seropositive humans.
K-function difference analyses, where observed values above 99% tolerance limits indicate statistically significant spatial clustering at a given spatial scale. Clustering of households with T. infestans was statistically significant at all spatial scales from 10 to 500 m (top panel), while clustering of households with T. cruzi-infected vectors was statistically significant only at spatial scales from 10 to 130 m and 390 to 410 m (middle panel). Clustering of households with T. cruzi-seropositive humans was not statistically significant at any spatial scale from 10 to 500 m (bottom panel).
Figure 4
Figure 4. A comparison of catalytic model predictions and actual age-specific T. cruzi seroprevalence.
Curves show the predicted prevalence of T. cruzi infection versus time at risk for each of the three regression models evaluated. A histogram of seroprevalence by five-year age category is provided for comparison of model and empirical results. The value inside each bar represents the number of T. cruzi-seropositive individuals in each 5-year age category.
Figure 5
Figure 5. A comparison of catalytic model prediction and historical data.
An expanded catalytic model and a Bayesian MCMC algorithm were used to estimate the year of an insecticide intervention in La Joya. The frequency histogram shows the distribution of the 1,000 estimates generated by the model. Model prediction of the year of the intervention was confirmed by historical documentation of a campaign authorized by then-President Fujimori as part of his reelection campaign.

References

    1. World Health Organization. Geneva: World Health Organization; 2007. Reporte sobre la enfermedad de Chagas.
    1. World Health Organization. Geneva: World Health Organization; 2002. Control of Chagas disease: Second report of the WHO expert committee.
    1. Heymann DL, editor. Washington, DC: American Public Health Association; 2004. Control of communicable diseases manual (18th edition).
    1. World Health Organization. Geneva: World Health Organization; 2004. Revised global burden of disease (GBD) 2002 estimates.
    1. Dias JCP, Silveira AC, Schofield CJ. The impact of Chagas disease control in Latin America - A review. Mem Inst Oswaldo Cruz. 2002;97:603–12. - PubMed

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