José F. Gil

Epidemiology of and impact of insecticide spraying on Chagas disease in communities in the Bolivian Chaco.

Background Chagas disease control campaigns relying upon residual insecticide spraying have been successful in many Southern American countries. However, in some areas, rapid reinfestation and recrudescence of transmission have occurred. Methodology/Principal Findings We conducted a cross-sectional survey in the Bolivian Chaco to evaluate prevalence of and risk factors for T. cruzi infection 11 years after two rounds of blanket insecticide application. We used a cubic B-spline model to estimate change in force of infection over time based on age-specific seroprevalence data. Overall T. cruzi seroprevalence was 51.7%. The prevalence was 19.8% among children 2–15, 72.7% among those 15–30 and 97.1% among participants older than 30 years. Based on the model, the estimated annual force of infection was 4.3% over the two years before the first blanket spray in 2000 and fell to 0.4% for 2001–2002. The estimated annual force of infection for 2004–2005, the 2 year period following the second blanket spray, was 4.6%. However, the 95% bootstrap confidence intervals overlap for all of these estimates. In a multivariable model, only sleeping in a structure with cracks in the walls (aOR = 2.35; 95% CI = 1.15–4.78), age and village of residence were associated with infection. Conclusions/Significance As in other areas in the Chaco, we found an extremely high prevalence of Chagas disease. Despite evidence that blanket insecticide application in 2000 may have decreased the force of infection, active transmission is ongoing. Continued spraying vigilance, infestation surveillance, and systematic household improvements are necessary to disrupt and sustain interruption of infection transmission.

Urban Transmission of American Cutaneous Leishmaniasis in Argentina: Spatial Analysis Study

We used kernel density and scan statistics to examine the spatial distribution of cases of pediatric and adult American cutaneous leishmaniasis in an urban disease-endemic area in Salta Province, Argentina. Spatial analysis was used for the whole population and stratified by women > 14 years of age (n = 159), men > 14 years of age (n = 667), and children < 15 years of age (n = 213). Although kernel density for adults encompassed nearly the entire city, distribution in children was most prevalent in the peripheral areas of the city. Scan statistic analysis for adult males, adult females, and children found 11, 2, and 8 clusters, respectively. Clusters for children had the highest odds ratios (P < 0.05) and were located in proximity of plantations and secondary vegetation. The data from this study provide further evidence of the potential urban transmission of American cutaneous leishmaniasis in northern Argentina.

Performance of different Trypanosoma cruzi antigens in the diagnosis of Chagas disease in patients with American cutaneous leishmaniasis from a co-endemic region in Argentina.

To determine the ability of recombinant antigens to detect cases of infection with Trypanosoma cruzi among cases of infection with Leishmania spp. by serological methods.

Immuno-enzymatic evaluation of the recombinant TSSA-II protein of Trypanosoma cruzi in dogs and human sera: a tool for epidemiological studies

The rTSSA-II (recombinant Trypomastigote Small Surface II) antigen was evaluated by ELISA to detect anti-Trypanosoma cruzi antibodies in sera from naturally infected dogs and humans. For this evaluation ELISA-rTSSA-II was standardized and groups were classified according to the results obtained through xenodiagnosis, ELISA and PCR. Sensitivity (Se), Specificity (Sp), Kappa index (KI) and area under curve (AUC) were determined. The Se was determined by using 14 sera from dogs infected with T. cruzi VI (TcVI) whereas Sp was determined by using 95 non-chagasic sera by xenodiagnosis, ELISA-Homogenate and PCR. The performance of ELISA-rTSSA-II in dog sera was high (AUC=0·93 and KI=0·91). The Se was 92·85% (1 false negative) and Sp was 100%. Two sera from dogs infected with TcI and 1 with TcIII were negative. For patients infected with T. cruzi, reactivity was 87·8% (36/41), there was only 1 indeterminate, and Sp was 100%. Fifty-four sera from non-chagasic and 68 sera from patients with cutaneous leishmaniasis did not react with rTSS-II. ELISA-rTSSA-II showed a high performance when studying sera from naturally infected dogs and it also presented 100% Sp. This assay could be an important tool to carry out sero-epidemiological surveys on the prevalence of T. cruzi circulating lineages in the region.

Benznidazole treatment in chronic children infected with Trypanosoma cruzi: serological and molecular follow-up of patients and identification of Discrete Typing Units.

A total of 221 children from two rural settlements in Northeast Argentina were examined for T. cruzi infection. Blood samples were taken for serology tests and PCR assays. In addition, T. cruzi Discrete Typing Units (DTUs) were determined by hybridization with specific DNA probes of the minicircle hypervariable regions (mHVR). Serological results indicated that 26% (57/215) were reactive against T. cruzi antigens. PCR analyses were performed on seropositive samples showing presence of parasite DNA in 31 out of 53 samples (58.5%). All seropositive children underwent specific chemotherapy with Benznidazole (5mg/kg/day) for a period of two months and were monitored two and five years after treatment. Overall the treatment was well tolerated and low side effects were observed. Serological conversion was observed at two years post -treatment in one child form Pampa Ávila and at five years in two children from Tres Estacas. However, at the end of the follow-up period, T. cruzi DNA could not be detected by PCR in samples from treated children, except in two cases. In addition, the results of hybridizations with specific DNA probes showed that DTU TcV was detected in 68% (21/31), TcVI in 7% (2/31) and TcV/VI in 3% (1/31) of the samples. Altogether, results of the follow-up of treated children showed a low rate of seroconversion; however trend toward seroconversion was evident at five years post-treatment. On the other hand, detection of T. cruzi DNA by PCR significantly decreased after Benznidazole treatment. The existence of data regarding serological and molecular follow-ups from controlled studies in the Chaco Region will be important for future treatment efforts against T. cruzi infection in this region. The results obtained in the present study represent a contribution in this regard.

The impact of point source pollution on shallow groundwater used for human consumption in a threshold country

Many developing and threshold countries rely on shallow groundwater wells for their water supply whilst pit latrines are used for sanitation. We employed a unified strategy involving satellite images and environmental monitoring of 16 physico-chemical and microbiological water quality parameters to identify significant land uses that can lead to unacceptable deterioration of source water, in a region with a subtropical climate and seasonally restricted torrential rainfall in Northern Argentina. Agricultural and non-agricultural sources of nitrate were illustrated in satellite images and used to assess the organic load discharged. The estimated human organic load per year was 28.5 BOD(5) tons and the N load was 7.5 tons, while for poultry farms it was 9940-BOD(5) tons and 1037-N tons, respectively. Concentrations of nitrates and organics were significantly different between seasons in well water (p values of 0.026 and 0.039, respectively). The onset of the wet season had an extraordinarily negative impact on well water due in part to the high permeability of soils made up of fine gravels and coarse sand. Discriminant analysis showed that land uses had a pronounced seasonal influence on nitrates and introduced additional microbial contamination, causing nitrification and denitrification in shallow groundwater. P-well was highly impacted by a poultry farm while S-well was affected by anthropogenic pollution and background load, as revealed by Principal Component Analysis. The application of microbial source tracking techniques is recommended to corroborate local sources of human versus animal origin.

Ivermectin-related adverse clinical events in patients treated for Mansonella ozzardi infections

We report the occurrence of serious reactions after treatment with oral ivermectin in two patients with Mansonella ozzardi infections. Both had systemic and respiratory symptoms and recovered without sequelae. Follow-up revealed clearance of microfilaremia in both cases, with relapse in one of them. These reactions are well described in the treatment of other filarial infections, but have not yet been reported in the treatment of M. ozzardi. We are now reporting the first such known reactions with this helminthiasis.

Epidemiology of American Tegumentary Leishmaniasis and Trypanosoma cruzi Infection in the Northwestern Argentina

Background. Endemic areas of tegumentary leishmaniasis (TL) in Salta, Argentina, present some overlap zones with the geographical distribution of Chagas disease, with mixed infection cases being often detected. Objectives. The purpose of this study was to determine the magnitude of Leishmania sp. infection and potential associated risk factors, the serologic prevalence of T. cruzi, and the presence of T. cruzi-Leishmania sp. mixed infection in a region of the northwest of Argentina. Methods. Cross-sectional studies were conducted to detect TL prevalence and T. cruzi seroprevalence. A case-control study was conducted to examine leishmaniasis risk factors. Results. Prevalence of TL was 0.17%, seroprevalence of T. cruzi infection was 9.73%, and mixed infection proportion—within the leishmaniasic patients group—was 16.67%. The risk factors associated with TL transmission were sex, age, exposure to bites at work, staying outdoors more than 10 hours/day, bathing in the river, and living with people who had lesions or were infected during the study. Discussion. The endemic pattern of TL seems to involve exposure of patients to vectors in wild as well as peridomestic environment. Cases of T. cruzi infection are apparently due to migration. Therefore, a careful epidemiological surveillance is necessary due to the contraindication of antimonial administration to chagasic patients.

Spatial spread of dengue in a non-endemic tropical city in northern Argentina

After more than eighty years dengue reemerged in Argentina in 1997. Since then, the largest epidemic in terms of geographical extent, magnitude and mortality, was recorded in 2009. In this report we analyzed the DEN-1 epidemic spread in Orán, a mid-size city in a non-endemic tropical area in Northern Argentina, and its correlation with demographic and socioeconomic factors. Cases were diagnosed by ELISA between January and June 2009. We applied a space-time and spatial scan statistic under a Poisson model. Possible association between dengue incidence and socio-economic variables was studied with the Spearman correlation test. The epidemic started from an imported case from Bolivia and space-time analysis detected two clusters: one on February and other in April (in the south and the northeast of the city respectively) with risk ratios of 25.24 and 4.07 (p<0.01). Subsequent cases spread widely around the city without significant space-temporal clustering. Maximum values of the entomological indices were observed in January, at the beginning of the epidemic (B=21.96; LH=8.39). No statistically significant association between socioeconomic variables and dengue incidence was found but positive correlation between population size and the number of cases (p<0.05) was detected. Two mechanisms may explain the observed pattern of epidemic spread in this non-endemic tropical city: a) Short range dispersal of mosquitoes and people generates clusters of cases and b) long-distance (within the city) human movement contributes to a quasi-random distribution of cases.

Restricted outbreak of American tegumentary leishmaniasis with high microfocal transmission.

Cutaneous leishmaniasis is endemic in Salta, the northwestern province of Argentina. We describe an outbreak involving five recreational hunters whose exposure was limited to several hours in a residual patch of primary forest. All patients presented with typical cutaneous lesions after a mean incubation period of 59 days (range 15-78), and one developed simultaneous mucosal involvement. Polymerase chain reaction analysis of lesions confirmed Leishmania (V.) braziliensis as the etiologic agent in three cases. All patients were cured with anti-Leishmania treatment. Entomologic surveys in the transmission area revealed a predominance of Lutzomyia neivai. This outbreak report confirms a microfocal transmission pattern of tegumentary leishmaniasis in the Americas and based on a well-determined exposure, allows the determination of incubation times for leishmaniasis caused by Leishmania braziliensis.