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To date, Triatoma dimidiata sensu lato [Reduviidae: Triatominae (Latreille 1811)] remains the sole vector species associated with Chagas disease transmission reported from Belize. Human infection data are limited for Belize and the disease transmission dynamics have not been thoroughly investigated, yet the likelihood of autochthonous transmission is supported by the widespread collection of infected vectors from within local households. Here, we report updated infection rates of the vector population and infestation rates for villages in north and central Belize. Overall, 275 households were enrolled in an ongoing vector surveillance program. Of the 41 insects collected, 25 were PCR positive for T. cruzi, indicating an infection rate as high as 60%. To further characterize the epidemiological risk of human-vector contact, determinants of household invasion were modeled. Local households were surveyed and characterized with respect to over 25 key factors that may be associated with household infestation by T. dimidiata s.l. While final models were not strongly predictive with respect to the risk factors that were surveyed, likely due to the low number of collection observations, the presence of domestic/peri-domestic dogs, nearby light sources, and household structure materials could be the focus of continued risk assessments. In northern Belize, this vector survey lends support to T. dimidiata s.l. inhabiting sylvatic settings as opposed to the classical paradigm of domiciliated vector populations. This designation has strong implications for the local level of human exposure risk which can help guide vector surveillance and control resources.

Assuntos

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AbstractThe Department of Santa Rosa, Guatemala, is targeted for malaria elimination. However, compared with 2011, a 13-fold increase in cases was reported in 2012. To describe the epidemiology of malaria in Santa Rosa in the setting of the apparent outbreak, demographic and microscopic data from 2008 to 2013 were analyzed. In April 2012, a new surveillance strategy, funded by the Global Fund to Fight AIDS, Tuberculosis and Malaria, was introduced involving more active case detection, centralized microscopy, increased community engagement, and expanded vector control. Interviews with vector control personnel and site visits were conducted in June 2013. From 2008 to 2013, 337 cases of malaria were reported. The increase in cases occurred largely after the new surveillance strategy was implemented. Most (137/165; 83%) 2012 cases came from one town near a lake. Plasmodium vivax was the malaria species detected in all cases. Cases were detected where malaria was not previously reported. Monthly rainfall or/and temperature did not correlate with cases. Interviews with public health personnel suggested that the new funding, staffing, and strategy were responsible for improved quality of malaria detection and control and thus the increase in reported cases. Improvements in surveillance, case detection, and funding appear responsible for the temporary increase in cases, which thus may paradoxically indicate progress toward elimination.

Assuntos

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Anthropogenic land use changes often alter natural patterns of disease transmission. The goal of this study was to determine whether phosphorus input from sugarcane, Saccharum officinarum L., cultivation in northern Belize could pose a significant environmental impact on malaria transmission by changing vegetation structure and composition of wetlands and associated larval habitats. Our primary focus was on the increased dominance of cattail, Typha domingensis Pers., a favored habitat for Anopheles vestitipennis Dyar & Knab. A land cover classification based on satellite imagery was used to select 20 marshes impacted by agricultural runoff and 20 marshes surrounded by forest (nonimpacted). A 100-m transect was established into each of the 40 marshes. Water, vegetation, and larval sampling were conducted at the 0-, 10-, 25-, 50-, and 100-m locations along the transect. Analyses of larval density data indicated that Anopheles albimanus Wiedemann was negatively correlated with percentage of cover of Typha (R2 = 0.39, P < 0.001) but positively correlated with sparse Eleocharis cellulosa Torr. (rush) cover (R2 = 0.19, P < 0.05) and presence of cyanobacterial mats (CBM) (R2 = 0.33, P < 0.0001). An. vestitipennis was found to be positively correlated with percentage of cover of Typha (R2 = 0.19, P < 0.001). Canonical correspondence analysis identified CBM and light as the variables associated with the presence of An. albimanuts larvae, Typha cover with An. vestitipennis larvae, and Eleocharis and absence of light with Anopheles crucians (Wiedemann). A positive correlation also existed between marshes adjacent to agricultural activities and presence of An. vestitipennis (R2 = 0.37, P < 0.05). These results indicate that marshes in proximity to agricultural fields are conducive for Typha growth, thereby providing habitat for the more efficient malaria vector

Assuntos

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Previous studies have identified several anopheline species integral to the transmission of malaria in Belize. The highly efficient vector, Anopheles darlingi Root, is currently considered the most important. The preferred larval habitat of An. darlingi has been described as floating detritus patches, which are commonly associated with overhanging spiny bamboo, Guadua longifolia (E. Fourn.), along river margins. The objectives of this study were to use remote sensing and geographic information system (GIS) tools to 1) define the landscape features (i.e., river curvature, land cover, and house locations) associated with An. darlingi-positive breeding habitats and 2) determine the association between cleared land cover and the growth of spiny bamboo. A systematic survey was conducted in which all detritus patches of at least 1 m2 were sampled, mapped using GPS, and characterized by cause of habitat lodging. Bamboo stretches growing along the river margins also were mapped. Spatial analyses of satellite imagery found no associations between river characteristics or land cover with positive An. darlingi habitats. In addition, there was no significant difference in cleared versus forested land cover in relation to the presence or absence of bamboo. Results indicate that the average distance from homes to negative habitats was significantly greater than from positive detritus mats. Based on the land cover and river characteristics used, our results do not support the use of remote sensing as a predictive tool to locate specific areas within rivers positive for An. darlingi habitats.

Assuntos

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BACKGROUND: The purposes of this study were to map overall malaria incidence rates from 1989 through 1999 for villages in Belize; to assess the seasonal distribution of malaria incidence by region; and to correlate malaria incidence rates with vegetation cover and rivers in villages, using geographic information system technology.Malaria information on 156 villages was obtained from an electronic database maintained by the Belize National Malaria Control Program. Average annual malaria incidence rates per 1000 population over 10 years were calculated for villages using the 1991 population census as a denominator. Malaria incidence rates were integrated with vegetation cover from a 1995 vegetation map, and with river data from a digital data set. RESULTS: Mapping malaria incidence over the 10-year period in the study villages indicated the existence of a spatial pattern: the southern and western areas of Belize had consistently higher rates of malaria than northern areas. Examination of the seasonal distribution of malaria incidence by month over 10 years indicated that a statistically significant difference existed among districts and among months (p < 0.05). Spatial analysis of malaria incidence rates and of vegetation in Belize showed villages with high malaria rates having more broadleaf hill forests, agricultural land, and wetland vegetation types (i.e. SWF-seasonally waterlogged fire-induced shrubland of the plains). Statistical and spatial analyses of malaria incidence and of river distributions in Belize determined the high 10 percentile malaria incidence villages in western and southern Belize to have more rivers within two kilometers of the center of a village and a statistically significant correlation between proximity to rivers and villages (Spearman's gamma = -0.23; p < 0.05), especially in Stann Creek District (Spearman's gamma = -0.82; p < 0.05). CONCLUSIONS: Examination of the distribution of malaria during 10 years indicated transmission varied among geographic areas and among seasons. Additional studies are needed to examine, in more detail, the association between environmental and meteorological factors and malaria transmission. Furthermore, the role of An. darlingi in malaria transmission in Stann Creek needs further study since, of the three main vectors in Belize, An. darlingi has been found strongly associated with rivers.