Interruption of Transmission of Onchocerca volvulus in the Oaxaca Focus, Mexico

Rodríguez‐Pérez, Mario A.; Unnasch, Thomas R.; Domínguez-Vázquez, Alfredo; Morales-Castro, Alba L.; Peña-Flores, Graciela P.; Orozco-Algarra, María E.; Arredondo‐Jiménez, Juan I.; Richards, Frank O.; Vásquez-Rodríguez, Miguel A.; Rendón, Vidal García

doi:10.4269/ajtmh.2010.09-0544

Cited by 28 publications

(29 citation statements)

References 23 publications

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“…Currently, WHO guidelines for assessment of transmission interruption are based on the monitoring of antigenemia (for Wb at least) in children; however, antibody responses – particularly to antigens expressed in L3s (the infective larvae) are likely to provide much earlier measures of ongoing transmission [5], [6] than the presence of microfilariae or circulating filarial antigen. Such an approach has been used quite successfully in onchocerciasis-endemic regions of Central America where the absence of antibody responses to an O. volvulus (Ov) L3-expressed antigen, Ov16 [7], has been used as one of the criteria to certify areas free of Ov transmission [8]–[11].…”

Section: Introductionmentioning

confidence: 99%

Identification of Wb123 as an Early and Specific Marker of Wuchereria bancrofti Infection

Kubofcik¹,

Fink²,

Nutman

2012

PLoS Negl Trop Dis

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BackgroundThe current antibody tests used for monitoring in lymphatic filariasis (LF) elimination programs suffer from poor specificity because of the considerable geographical overlap with other filarial infections such as Loa loa (Ll), Onchocerca volvulus (Ov), and Mansonella perstans (Mp).MethodsUsing bioinformatics to assemble into contigs 2048 expressed sequence tags (ESTs) from the L3 infective larvae of W. bancrofti (Wb), these were next assessed for homology to known proteins and nucleotides and to similar assemblies of L3 larval ESTs of B. malayi (Bm – n = 5068), Ov (n = 4166), and Ll (n = 3315). Nineteen potential L3- and Wb- and/or Bm-specific antigens were identified. Sixteen of the 19 antigens could be expressed as fusion proteins with Renilla luciferase (Ruc); these were used in a rapid Luciferase Immunopreciptation System (LIPS) assay.ResultsOne of the 16 expressed antigens (Wb123) was both highly immunogenic and specific for Wb. Using Wb123-based IgG and IgG4 LIPS assays on well-defined sera from normal North Americans and those infected exclusively with intestinal helminths, we could detect all of the Wb-infected individuals (from diverse geographic regions) with 100% sensitivity and 100% specificity. Using sera from exclusively Ll-infected, Ov-infected Mp-infected or Bm-infected subjects as the negative comparator, the sensitivities were between 98–100% and the specificities ranged between 84–100% (for IgG anti-Wb123) and between 98–100% (for IgG4 anti-Wb123). Blinded assessments using panels of sera from various Wb-, Bm- or non-Wb helminth-infected subjects demonstrated equally high degrees of sensitivity and specificity.SignificanceWe have identified a Wb-encoded antigen that can be used both as a rapid, high throughput tool to diagnose individual Wb infections and as a sensitive method for early detection of recrudescent infections in areas of control and for mapping new areas of Wb transmission.

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Section: Introductionmentioning

confidence: 99%

Identification of Wb123 as an Early and Specific Marker of Wuchereria bancrofti Infection

Kubofcik¹,

Fink²,

Nutman

2012

PLoS Negl Trop Dis

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“…The key aspect in the control of onchocerciasis disease in Latin America is the treatment with the drug ivermectin available to all the people at risk [4], [8], [21]–[24]. The onchocerciasis program in Mexico began treatment with ivermectin in 1989, initially treating only symptomatic individuals in hyperendemic communities [4].…”

Section: Discussionmentioning

confidence: 99%

Time Series Analysis of Onchocerciasis Data from Mexico: A Trend towards Elimination

et al. 2013

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BackgroundIn Latin America, there are 13 geographically isolated endemic foci distributed among Mexico, Guatemala, Colombia, Venezuela, Brazil and Ecuador. The communities of the three endemic foci found within Mexico have been receiving ivermectin treatment since 1989. In this study, we predicted the trend of occurrence of cases in Mexico by applying time series analysis to monthly onchocerciasis data reported by the Mexican Secretariat of Health between 1988 and 2011 using the software R.ResultsA total of 15,584 cases were reported in Mexico from 1988 to 2011. The data of onchocerciasis cases are mainly from the main endemic foci of Chiapas and Oaxaca. The last case in Oaxaca was reported in 1998, but new cases were reported in the Chiapas foci up to 2011. Time series analysis performed for the foci in Mexico showed a decreasing trend of the disease over time. The best-fitted models with the smallest Akaike Information Criterion (AIC) were Auto-Regressive Integrated Moving Average (ARIMA) models, which were used to predict the tendency of onchocerciasis cases for two years ahead. According to the ARIMA models predictions, the cases in very low number (below 1) are expected for the disease between 2012 and 2013 in Chiapas, the last endemic region in Mexico.ConclusionThe endemic regions of Mexico evolved from high onchocerciasis-endemic states to the interruption of transmission due to the strategies followed by the MSH, based on treatment with ivermectin. The extremely low level of expected cases as predicted by ARIMA models for the next two years suggest that the onchocerciasis is being eliminated in Mexico. To our knowledge, it is the first study utilizing time series for predicting case dynamics of onchocerciasis, which could be used as a benchmark during monitoring and post-treatment surveillance.

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“…Thus, northern Chiapas joins the five other foci in Latin America where transmission seems to have been interrupted: Oaxaca in Mexico, Santa Rosa, Huehuetenango, and Escuintla-Guatemala in Guatemala, and López de Micay in Colombia. 10,18,[20][21][22][23] The entomological criteria for asserting interruption of transmission includes the absence or near absence of infective-stage larvae of O. volvulus in the vector population, which has been operationally defined as < 1 infective fly per 2,000 examined. 9,10 During the first entomologic study carried out in Altagracia of the northern Chiapas focus, which was conducted in 2001 after 4 years of mass semiannual treatment with Mectizan, parasite DNA was detected in a single pool of 50 vector heads out of a total of 125 pools examined (6,250 flies total).…”

Section: Discussionmentioning

confidence: 99%

“…For this reason, additional communities were not included to increase the sample size as reported elsewhere. 10,18 Blood was collected by finger prick from each individual enrolled in the study, dried in the field, transported to the laboratory at 4°C, and kept refrigerated in sealed bags containing silica gel at −20°C until use. Blood collections and IgG 4-Ov16 ELISA assays to monitor exposure in the under 10 cohort were carried out as previously described.…”

Section: 11mentioning

confidence: 99%

Lack of Active Onchocerca volvulus Transmission in the Northern Chiapas Focus of Mexico

Rodríguez‐Pérez¹,

Unnasch²,

Domínguez-Vázquez³

et al. 2010

The American Society of Tropical Medicine and Hygiene

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The northern Chiapas onchocerciasis focus has undergone 11 years of ivermectin mass treatment. No evidence of microfilariae in the cornea and/or anterior chamber of the eye or in skin snips was seen in residents examined in 2006 in two sentinel communities (upper limit of the 95% confidence interval [UL 95% CI] = 0.5% and 0.3%, respectively). In children 10 and under, 0 of 305 were found to harbor antibodies to Ov16, a marker of parasite exposure; 0 of 4,400 Simulium ochraceum s.l. collected in 2005 contained parasite DNA, giving an UL 95% CI for the infective rate of 0.9/2,000, and an UL 95% CI of the seasonal transmission potential of 1.2 L3/person. These data, assumed to be representative of the focus as a whole, suggest that there is no ongoing transmission of Onchocerca volvulus in the northern Chiapas focus. Community-wide treatments with ivermectin were halted in 2008, and a post-treatment surveillance phase was initiated.

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Interruption of Transmission of Onchocerca volvulus in the Oaxaca Focus, Mexico

Cited by 28 publications

References 23 publications

Identification of Wb123 as an Early and Specific Marker of Wuchereria bancrofti Infection

Identification of Wb123 as an Early and Specific Marker of Wuchereria bancrofti Infection

Time Series Analysis of Onchocerciasis Data from Mexico: A Trend towards Elimination

Lack of Active Onchocerca volvulus Transmission in the Northern Chiapas Focus of Mexico

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