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

Rodríguez‐Pérez, Mario A.; Unnasch, Thomas R.; Domínguez-Vázquez, Alfredo; Morales-Castro, Alba L.; Richards, Frank O.; Peña-Flores, Graciela P.; Orozco-Algarra, María E.; Prado-Velasco, Gibert

doi:10.4269/ajtmh.2010.09-0626

Cited by 18 publications

(21 citation statements)

References 16 publications

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“…Purified DNA was used as a template in the Onchocerca-specific O-150 polymerase chain reaction (PCR) followed by PCR-based enzyme-linked immunosorbent assay (ELISA) using probes specific for the parasite as previously reported. 18,[21][22][23] A sample was considered putatively positive if it had an ELISA score at or above the cutoff (i.e., the mean of 10 internal negative controls plus 3 SD). Only samples that were positive after a second independent PCR and ELISA were reported as confirmed positive.…”

Section: Methodsmentioning

confidence: 99%

“…The flies were divided into pools of 100 or less by site and date of collection and maintained in isopropanol until analysis. Heads of each black fly pool were first separated from bodies, and DNA was then extracted from pools of fly heads according to published procedures, 18,21,22 including the use of a 96-well purification module (Qiagen Inc., Valencia, CA) to streamline the DNA extraction process. A sham extraction was included with every 11 extractions to serve as contamination control.…”

Section: Methodsmentioning

confidence: 99%

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Interruption of Onchocerca volvulus Transmission in the Abu Hamed Focus, Sudan

Higazi

Zarroug

Mohamed

et al. 2013

The American Society of Tropical Medicine and Hygiene

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Abstract. Abu Hamed, Sudan, the northernmost location of onchocerciasis in the world, began community-directed treatment with ivermectin (CDTI) in 1998, with annual treatments enhanced to semiannual in 2007. We assessed the status of the parasite transmission in 2011 entomologically, parasitologically, and serologically. O-150 pool screening showed no parasite DNA in 17,537 black flies collected in 2011 (95% confidence interval upper limit [95% CI UL] = 0.023). Skin microfilariae, nodules, and signs of skin disease were absent in 536 individuals in seven local communities. Similarly, no evidence of Onchocerca volvulus Ov16 antibodies was found in 6,756 school children 10 years (95% CI UL = 0.03%). Because this assessment of the focus meets the 2001 World Health Organization (WHO) criteria for interrupted transmission, treatment was halted in 2012, and a post-treatment surveillance period was initiated in anticipation of declaration of disease elimination in this area. We provide the first evidence in East Africa that long-term CDTI alone can interrupt transmission of onchocerciasis.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Interruption of Onchocerca volvulus Transmission in the Abu Hamed Focus, Sudan

Higazi

Zarroug

Mohamed

et al. 2013

The American Society of Tropical Medicine and Hygiene

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“…Black flies were obtained and head pools of ≤ 100 heads were processed for O. volvulus -specific the O-150 polymerase chain reaction (PCR) and PCR-based enzyme-linked immunosorbent assay (ELISA) as reported. [15][16][17] A sample was considered putatively positive if it had an ELISA score at or above the cutoff (i.e., the mean of 10 internal negative controls plus 3 SD). Samples positive after a second independent PCR and ELISA were reported as confirmed positive.…”

mentioning

confidence: 99%

Polymerase Chain Reaction Pool Screening Used To Compare Prevalence of Infective Black Flies in Two Onchocerciasis Foci in Northern Sudan

Higazi¹,

Zarroug²,

Mohamed³

et al. 2011

The American Society of Tropical Medicine and Hygiene

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Onchocerciasis remains an important debilitating disease in many areas of Africa, including Sudan. The status of infection transmission in 2007 was assessed in the vectors of two disease foci in Sudan: Abu Hamed in northern Sudan, which has received at least 10 years of annual treatment and Galabat focus in eastern Sudan, where only minor, largely undocumented treatment activity has occurred. Assessment of more than 30,000 black flies for Onchocerca volvulus infectious stage L3 larvae by using an O-150 polymerase chain reaction protocol showed that black fly infectivity rates were 0.84 (95% confidence interval = 0.0497–1.88) per 10,000 flies for Abu Hamed and 6.9 (95% confidence interval = 1.1–16.4) infective flies per 10,000 for Galabat. These results provide entomologic evidence for suppressed Onchocerca volvulus transmission in the Abu Hamed focus and a moderate transmission rate of the parasite in the Galabat focus.

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“…In Mexico, the first cases of onchocerciasis were documented in 1923 in Chiapas, originated as a consequence of active seasonal migration of coffee workers from the endemic areas between Guatemala and Mexico. The regions in Chiapas and Oaxaca of Mexico are associated with the presence of abundant vector populations [4]. The focus of Oaxaca and Northern Chiapas represented the expansion of onchocerciasis from Southern Mexico or Guatemala [5].…”

Section: Introductionmentioning

confidence: 99%

“…The administration of diethylcarbamazine (DEC) began in 1947, followed by a sporadic application of DDT to eliminate the vector populations in 1952. In 1990, DEC was supplanted by ivermectin (Mectizan; Merck & Co., Inc., Whitehouse Station, NJ) [4]. In 1992, the Onchocerciasis Elimination Program for the Americas (OEPA) was launched [7], and has successfully coordinated the efforts of the affected countries in Latin America.…”

Section: Introductionmentioning

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

Cited by 18 publications

References 16 publications

Interruption of Onchocerca volvulus Transmission in the Abu Hamed Focus, Sudan

Interruption of Onchocerca volvulus Transmission in the Abu Hamed Focus, Sudan

Polymerase Chain Reaction Pool Screening Used To Compare Prevalence of Infective Black Flies in Two Onchocerciasis Foci in Northern Sudan

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

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