RESUMO
Onchocerciasis is a blinding disease caused by the filarial parasite Onchocerca volvulus, with a worldwide distribution. Onchocerciasis has been targeted for regional elimination based on annual and semiannual mass drug administration (MDA) with ivermectin in endemic communities over several years. This strategy in Ecuador led to the interruption of transmission and suspension of ivermectin MDA in 2009 with certification of elimination in 2014. In the present study, we analyzed sera collected in 2018 from 123 children aged 5-9 years from formerly hyperendemic communities in the Esmeraldas focus, Ecuador, for the presence of antibodies to Ov16 antigen. All samples were negative, indicating no evidence of transmission since MDA was stopped. Ov16-based serology offers an economic and practical alternative for measuring vector infectivity for post-certification surveillance in formerly endemic countries where expertise and capacity to reliably measure fly infectivity rates are costly to maintain.
Assuntos
Onchocerca volvulus/imunologia , Oncocercose/epidemiologia , Animais , Criança , Pré-Escolar , Erradicação de Doenças , Equador/epidemiologia , Doenças Endêmicas , Monitoramento Epidemiológico , Feminino , Humanos , Masculino , Onchocerca volvulus/isolamento & purificação , Oncocercose/parasitologia , Oncocercose/prevenção & controleRESUMO
We report the elimination of Onchocerca volvulus transmission from the Central Endemic Zone (CEZ) of onchocerciasis in Guatemala, the largest focus of this disease in the Americas and the first to be discovered in this hemisphere by Rodolfo Robles Valverde in 1915. Mass drug administration (MDA) with ivermectin was launched in 1988, with semiannual MDA coverage reaching at least 85% of the eligible population in > 95% of treatment rounds during the 12-year period, 2000-2011. Serial parasitological testing to monitor MDA impact in sentinel villages showed a decrease in microfilaria skin prevalence from 70% to 0%, and polymerase chain reaction (PCR)-based entomological assessments of the principal vector Simulium ochraceum s.l. showed transmission interruption by 2007. These assessments, together with a 2010 serological survey in children 9-69 months of age that showed Ov16 IgG4 antibody prevalence to be < 0.1%, meeting World Health Organization (WHO) guidelines for stopping MDA, and treatment was halted after 2011. After 3 years an entomological assessment showed no evidence of vector infection or recrudescence of transmission. In 2015, 100 years after the discovery of its presence, the Ministry of Health of Guatemala declared onchocerciasis transmission as having been eliminated from the CEZ.
Assuntos
Erradicação de Doenças , Onchocerca volvulus , Oncocercose/prevenção & controle , Animais , Pré-Escolar , Olho/parasitologia , Feminino , Filaricidas/uso terapêutico , Guatemala/epidemiologia , Humanos , Controle de Insetos , Insetos Vetores/parasitologia , Ivermectina/uso terapêutico , Masculino , Oncocercose/tratamento farmacológico , Oncocercose/epidemiologia , Oncocercose/transmissão , Simuliidae/parasitologia , Pele/parasitologiaRESUMO
BACKGROUND: Mexico is one of the six countries formerly endemic for onchocerciasis in Latin America. Transmission has been interrupted in the three endemic foci of that country and mass drug distribution has ceased. Three years after mass drug distribution ended, post-treatment surveillance (PTS) surveys were undertaken which employed entomological indicators to check for transmission recrudescence. METHODOLOGY/PRINCIPAL FINDINGS: In-depth entomologic assessments were performed in 18 communities in the three endemic foci of Mexico. None of the 108,212 Simulium ochraceum s.l. collected from the three foci were found to contain parasite DNA when tested by polymerase chain reaction-enzyme-linked immunosorbent assay (PCR-ELISA), resulting in a maximum upper bound of the 95% confidence interval (95%-ULCI) of the infective rate in the vectors of 0.035/2,000 flies examined. This is an order of magnitude below the threshold of a 95%-ULCI of less than one infective fly per 2,000 flies tested, the current entomological criterion for interruption of transmission developed by the international community. The point estimate of seasonal transmission potential (STP) was zero, and the upper bound of the 95% confidence interval for the STP ranged from 1.2 to 1.7 L3/person/season in the different foci. This value is below all previous estimates for the minimum transmission potential required to maintain the parasite population. CONCLUSIONS/SIGNIFICANCE: The results from the in-depth entomological post treatment surveillance surveys strongly suggest that transmission has not resumed in the three foci of Mexico during the three years since the last distribution of ivermectin occurred; it was concluded that transmission remains undetectable without intervention, and Onchocerca volvulus has been eliminated from Mexico.
Assuntos
Oncocercose/prevenção & controle , Simuliidae/parasitologia , Animais , Anti-Helmínticos/administração & dosagem , Feminino , Humanos , Insetos Vetores/parasitologia , Insetos Vetores/fisiologia , Ivermectina/administração & dosagem , Masculino , México/epidemiologia , Onchocerca volvulus/genética , Onchocerca volvulus/isolamento & purificação , Onchocerca volvulus/fisiologia , Oncocercose/tratamento farmacológico , Oncocercose/epidemiologia , Oncocercose/transmissão , Simuliidae/fisiologiaRESUMO
INTRODUCTION: A clinically significant endemic focus of onchocerciasis existing in Esmeraldas Province, coastal Ecuador has been under an ivermectin mass drug administration program since 1991. The main transmitting vector in this area is the voracious blackfly, Simulium exiguum. This paper describes the assessments made that support the decision to cease mass treatment. METHODOLOGY AND PRINCIPLE FINDINGS: Thirty-five rounds of ivermectin treatment occurred between 1991-2009 with 29 of these carrying >85% coverage. Following the guidelines set by WHO for ceasing ivermectin distribution the impact on parasite transmission was measured in the two vector species by an O-150 PCR technique standard for assessing for the presence of Onchocerca volvulus. Up to seven collection sites in three major river systems were tested on four occasions between 1995 and 2008. The infectivity rates of 65.0 (CI 39-101) and 72.7 (CI 42-116) in 1995 dropped to zero at all seven collection sites by 2008. Assessment for the presence of antibodies against O. volvulus was made in 2001, 2006, 2007 and 2008 using standard ELISA assays for detecting anti-Ov16 antibodies. None of total of 1810 children aged 1-15 years (between 82 and 98% of children present in the surveyed villages) tested in the above years were found to be carrying antibodies to this antigen. These findings were the basis for the cessation of mass drug treatment with ivermectin in 2009. SIGNIFICANCE: This fulfillment of the criteria for cessation of mass distribution of ivermectin in the only known endemic zone of onchocerciasis in Ecuador moves the country into the surveillance phase of official verification for national elimination of transmission of infection. These findings indicate that ivermectin given twice a year with greater than 85% of the community can move a program to the final stages of verification of transmission interruption.
Assuntos
Filaricidas/administração & dosagem , Insetos Vetores/parasitologia , Ivermectina/administração & dosagem , Oncocercose/transmissão , Simuliidae/parasitologia , Adolescente , Animais , Anticorpos Anti-Helmínticos/sangue , Criança , Pré-Escolar , Equador/epidemiologia , Humanos , Lactente , Recém-Nascido , Oncocercose/epidemiologia , Oncocercose/parasitologia , Oncocercose/terapia , Serviços Preventivos de Saúde/métodosRESUMO
BACKGROUND: The Southern Chiapas focus of onchocerciasis in Southern Mexico represents one of the major onchocerciasis foci in Latin America. All 559 endemic communities of this focus have undergone semi-annual mass treatment with ivermectin since 1998. In 50 communities of this focus, ivermectin frequency shifted from twice to four times a year in 2003; an additional 113 communities were added to the quarterly treatment regimen in 2009 to achieve a rapid suppression of transmission. METHODOLOGY/PRINCIPAL FINDINGS: In-depth epidemiologic and entomologic assessments were performed in six sentinel communities (which had undergone 2 rounds of ivermectin treatment per year) and three extra-sentinel communities (which had undergone 4 rounds of ivermectin treatment per year). None of the 67,924 Simulium ochraceum s.l. collected from this focus during the dry season of 2011 were found to contain parasite DNA when tested by polymerase chain reaction-enzyme-linked immunosorbent assay (PCR-ELISA), resulting in an upper bound of the 95% confidence interval (95%-ULCI) of the infective rate in the vectors of 0.06/2,000 flies examined. Serological assays testing for Onchocerca volvulus exposure conducted on 4,230 children 5 years of age and under (of a total population of 10,280 in this age group) revealed that 2/4,230 individuals were exposed to O. volvulus (0.05%; one sided 95% confidence intervalâ=â0.08%). CONCLUSIONS/SIGNIFICANCE: The in-depth epidemiological and entomological findings from the Southern Chiapas focus meet the criteria for interruption of transmission developed by the international community.
Assuntos
Anti-Helmínticos/administração & dosagem , Ivermectina/administração & dosagem , Onchocerca volvulus/isolamento & purificação , Oncocercose/epidemiologia , Oncocercose/prevenção & controle , Animais , Criança , Pré-Escolar , DNA de Helmintos/isolamento & purificação , Ensaio de Imunoadsorção Enzimática , Feminino , Humanos , Lactente , Masculino , México/epidemiologia , Onchocerca volvulus/genética , Oncocercose/tratamento farmacológico , Oncocercose/parasitologia , Reação em Cadeia da Polimerase , Simuliidae/parasitologiaRESUMO
The distribution of Aedes (Stegomyia) aegypti (L.), the main vector of dengue viruses (DENV) worldwide, overlaps with Aedes (Gymnometopa) mediovittatus (Coquillett), the Caribbean treehole mosquito, in urban, suburban, and rural areas. Ae. mediovittatus is a competent vector of DENV with high rates of vertical DENV transmission in the laboratory. This study determined whether Ae. mediovittatus feeds on humans and compared its feeding patterns with co-occurring Ae. aegypti in two rural communities of Puerto Rico. Adult mosquitoes were captured for three consecutive days every week from July 2009 to May 2010 using BG-Sentinel traps with skin lures that were placed in the front yard of houses in both communities. Three methods were used to identify the 756 bloodmeals obtained in this study: a multiplex polymerase chain reaction (PCR) for humans and dogs targeting cytochrome b; a PCR targeting the 16S rRNA; and a nested PCR targeting cytochrome b. Ae. mediovittatus fed mostly on humans (45-52%) and dogs (28-32%) but also on cats, cows, horses, rats, pigs, goats, sheep, and chickens. Ae. aegypti fed mostly on humans (76-79%) and dogs (18-21%) but also on cats, horses, and chickens. Our results indicate that Ae. mediovittatus may have a relatively high rate of vector-human contact, which might facilitate virus transmission or harborage in rural areas of Puerto Rico.
Assuntos
Aedes/fisiologia , Interações Hospedeiro-Parasita , Insetos Vetores/fisiologia , Animais , Cães , Comportamento Alimentar , Feminino , Humanos , Porto RicoRESUMO
Prior to 2006, West Nile virus (WNV) had not been definitively detected in Chiapas, the southernmost state of Mexico, although it circulates elsewhere in Mexico and Central America. We collected over 30,000 mosquitoes and blood-sampled 351 domestic animals in Chiapas in search for evidence of current or recent transmission of WNV. Two mosquito pools tested positive for WNV RNA and 17 domestic animals tested positive for specific WNV-neutralizing antibodies, including young animals (<1 year old) in four of five sampled locations. The two WNV-positive mosquito pools were collected on the Pacific coastal plain of Chiapas in June, 2006, and included a pool of Culex nigripalpus, a suspected vector of WNV, and a pool of Cx. interrogator. The sequence of a 537-nucleotide portion of a cDNA amplicon derived from the WNV NS5 gene from the Cx. interrogator pool contained a single silent nucleotide substitution when compared to WNV strain NY99.
Assuntos
Doenças dos Animais/epidemiologia , Animais Domésticos/sangue , Culicidae/virologia , Febre do Nilo Ocidental/veterinária , Vírus do Nilo Ocidental/isolamento & purificação , Doenças dos Animais/sangue , Doenças dos Animais/virologia , Animais , Anticorpos Antivirais , Bovinos , Feminino , Cavalos , México/epidemiologia , Aves Domésticas , Suínos , Febre do Nilo Ocidental/sangue , Febre do Nilo Ocidental/epidemiologiaRESUMO
The impact of quarterly Mectizan (ivermectin) treatments on transmission, microfiladermia, and ocular lesions was evaluated in two formerly hyperendemic communities (Las Golondrinas and Las Nubes II) located in the main endemic focus for onchocerciasis in Southern Chiapas, Mexico. The data suggest that Onchocerca volvulus transmission has been suppressed after elimination of microfiladermia in these two communities. Increasing the frequency of Mectizan treatment to four times per year appears to have resulted in the rapid suppression of transmission in communities with residual transmission.
Assuntos
Filaricidas/uso terapêutico , Ivermectina/uso terapêutico , Onchocerca volvulus/efeitos dos fármacos , Oncocercose/prevenção & controle , Animais , Esquema de Medicação , Filaricidas/administração & dosagem , Humanos , Ivermectina/administração & dosagem , México/epidemiologia , Oncocercose/epidemiologia , Oncocercose/transmissão , Pele/parasitologiaRESUMO
Entomologic and serologic surveys were performed in four sentinel communities in the Oaxaca focus in southern Mexico to assess the level of transmission and exposure incidence to Onchocerca volvulus. All communities have been receiving ivermectin mass treatment twice per year since 1997. In one community, parasite DNA was detected by polymerase chain reaction-enzyme-linked immunosorbent assay in 2004 in one pool of 50 vector heads of 170 such pools (8,500 flies) examined, which indicated an estimated transmission potential of 6.7 third-stage larvae/person/year. No evidence for transmission was found in the three other communities in 13,650 flies examined. All persons in a cohort consisting of 117 children in the four communities remained serologically negative for antibodies recognizing a cocktail of recombinant antigens over a four-year period from 2001 to 2004, which indicated an exposure incidence of 0%. Taken together, these data suggest that transmission has been suppressed in the four communities.
Assuntos
Onchocerca volvulus/isolamento & purificação , Oncocercose/epidemiologia , Oncocercose/prevenção & controle , Animais , Antígenos de Helmintos/análise , DNA de Helmintos/análise , Ensaio de Imunoadsorção Enzimática , Filaricidas/uso terapêutico , Humanos , Incidência , Insetos Vetores/parasitologia , Ivermectina/uso terapêutico , México/epidemiologia , Onchocerca volvulus/genética , Onchocerca volvulus/imunologia , Oncocercose/etiologia , Oncocercose/transmissão , Reação em Cadeia da Polimerase , Simuliidae/parasitologiaRESUMO
To study the impact of mass Mectizan treatment on Onchocerca volvulus transmission in Mexico, entomological surveys were carried out in the endemic foci of Oaxaca, Southern Chiapas, and Northern Chiapas. Collected flies were screened by polymerase chain reaction (PCR) for O. volvulus parasites. The prevalence of infected and infective flies was estimated using the PoolScreen algorithm and with a novel probability-based method. O. volvulus infective larvae were not detected in flies from 6/13 communities. In 7/13 communities, infective flies were detected, with prevalences ranging from 1.6/10,000 to 29.0/10,000 and seasonal transmission potentials ranging from 0.4 to 3.3. Infected and infective flies were found in a community in Northern Chiapas, suggesting that, according to World Health Organization criteria, autochthonous transmission exists in this focus. These data suggest that O. volvulus transmission in Mexico has been suppressed or brought to a level that may be insufficient to sustain the parasite population.