Elimination of Onchocerciasis from Mexico.

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.

Interruption of transmission of Onchocerca volvulus in the Southern Chiapas Focus, México.

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 interval = 0.08%). 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.

Interruption of Onchocerca volvulus transmission in Northern Venezuela.

BACKGROUND: Onchocerciasis is caused by Onchocerca volvulus and transmitted by Simulium species (black flies). In the Americas, the infection has been previously described in 13 discrete regional foci distributed among six countries (Brazil, Colombia, Ecuador, Guatemala, Mexico and Venezuela) where more than 370,000 people are currently considered at risk. Since 2001, disease control in Venezuela has relied on the mass drug administration to the at-risk communities. This report provides empirical evidence of interruption of Onchocerca volvulus transmission by Simulium metallicum in 510 endemic communities from two Northern foci of Venezuela, after 10-12 years of 6-monthly Mectizan (ivermectin) treatment to all the eligible residents. METHODS: In-depth entomologic and epidemiologic surveys were serially conducted from 2001-2012 in selected (sentinel and extra-sentinel) communities from the North-central (NC) and North-east (NE) onchocerciasis foci of Venezuela in order to monitor the impact of ivermectin treatment. RESULTS: From 2007-2009, entomological indicators in both foci confirmed that 0 out of 112,637 S. metallicum females examined by PCR contained L3 infection in insect heads. The upper bound of the 95% confidence intervals of the infective rate of the vector reached values below 1% by 2009 (NC) and 2012 (NE). Additionally, after 14 (NC) and 22 (NE) rounds of treatment, the seasonal transmission potential (±UL CIs) of S. metallicum was under the critical threshold of 20 L3 per person per season. Serological analysis in school children < 15 years-old demonstrated that 0 out of 6,590 individuals were harboring antibodies to Ov-16. Finally, epidemiological surveys made during 2010 (NC) and 2012 (NE) showed no evidence of microfilariae in the skin and eyes of the population. CONCLUSIONS: These results meet the WHO criteria for absence of parasite transmission and disease morbidity in these endemic areas which represent 91% of the population previously at-risk in the country. Consequently, the two Northern foci are currently under post-treatment onchocerciasis surveillance status in Venezuela.

Interruption of transmission of Onchocerca volvulus in the Oaxaca focus, Mexico.

All endemic communities of the Oaxaca focus of onchocerciasis in southern Mexico have been treated annually or semi-annually with ivermectin since 1994. In-depth epidemiologic assessments were performed in communities during 2007 and 2008. None of the 52,632 Simulium ochraceum s.l. collected in four sentinel communities was found to contain parasite DNA when tested by polymerase chain reaction-enzyme-linked immunosorbent assay (PCR-ELISA), resulting in an upper bound of the infection rate in the vectors of 0.07/2,000. The prevalence of microfilariae (mf) in the cornea and/or anterior chamber of the eye was also zero (0 of 1,039 residents examined; 95%-UL = 0.35%). Similarly, all 1,164 individuals examined by skin biopsy were mf negative (95%-UL = 0.31%), and sera collected from 3,569 children from 25 communities did not harbor Ov16 IgG4-antibodies (95%-UL = 0.09%). These meet the criteria for absence of morbidity and parasite transmission in the Oaxaca focus. As a result mass treatments with ivermectin were halted in 2009.

Lack of active Onchocerca volvulus transmission in the northern Chiapas focus of Mexico.

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.

Rapid suppression of Onchocerca volvulus transmission in two communities of the Southern Chiapas focus, Mexico, achieved by quarterly treatments with Mectizan.

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.

Polymerase chain reaction monitoring of transmission of Onchocerca volvulus in two endemic states in Mexico.

To investigate the impact of mass ivermectin treatments in Mexico on Onchocerca volvulus transmission, entomologic surveys were carried out in the two endemic states of Oaxaca and Chiapas. The data suggest that substantial progress towards the goal of elimination has been made. A comparison pre- and post-ivermectin data from a community in Southern Chiapas showed a 97% decrease in seasonal transmission potential, but some level of polymerase chain reaction positivity was still detectable. In other communities from northern Chiapas and Oaxaca where there are no baseline data, there was an absence or near absence of infective flies. Residual transmission was not evenly distributed because differences were seen in the infection and infective rates from different catch points. These findings suggest that while substantial progress towards elimination has been made in Mexico, it may be necessary to modify ivermectin distribution strategies to eliminate transmission in areas where transmission persists.

Antibody detection tests for Onchocerca volvulus: comparison of the sensitivity of a cocktail of recombinant antigens used in the indirect enzyme-linked immunosorbent assay with a rapid-format antibody card test.

There is a need for a specific, sensitive, and practical diagnostic test to monitor onchocerciasis elimination campaigns. In April 2001, an enzyme-linked immunosorbent assay (ELISA) using 3 recombinant antigens and a rapid-format antibody card test (immunochromatographic test; ICT) using an individual antigen were compared in a Mexican population with onchocerciasis. The sensitivity of the ELISA and ICT was 97% and 86%, respectively.

Estudio de reservorios silvestres del Trypanosoma cruzi en la reserva ecológica de El Zapotal, Chiapas, México / Study of Trypanosoma cruzi in wild reservoirs in the ecological reserve of El Zapotal, Chiapas, Mexico

Reservoirs of T. cruzi were studied in the ecological reserve "El Zapotal", in the Tuxtla Gutiérrez municipality located in the state of Cchiapas. the parasite transmissión cycle exists in that area. A totral of 73 specimens of B different mammal species were trapped alive. Xenodiagnosis tests showed that 11% of them were positive for T. cruzi. Blood concentration exam, blood culture, serology (CIEP) and histological exam were carried out in 65 specimens fromthe total captured T. cruzi positive results in these tests were 1.5, 3.6 and 6.2% respectively. None of the 73 specimens were positive in the histological ewxams. Amastigote nests were found in cardiac tissue of mice, which were inoculated with triatomine bugs dejections collected from those specimens used from xenodiagnosis testing or by the inoculation of parasites grown in axenic blood cultures. These results indicated that there is a sylvan cycle which is maintained by mammal species, which are plundering this geographic area

Estado nutricional en niños menores de seis años y su asociación con malaria y parasitismo intestinal / Nutricional status of children under six years of age and its association with malaria and intestinal prasitism

Para determinar la prevalencia del estado nutricional en niños menores de seis años y estudiar su relación con malaria y parasitismo intestinal, se llevó a cabo un estudio epidemiológico de corte transversal en la localidad de Córdoba, municipio de Buenaventura, en la costa del Pacífico Colombiano. La población estudiada fue de 128 niños, a quienes se les aplicó un cuestionario, examen de gota gruesa y serológico por medio de la prueba de inmunofluorescencia indirecta. Tambíen se practicaon examenes coproparasitoscópicos, además de examen médico y clínico antropométrico, el cual consistió en la toma del peso y la talla. Los resultados de esta investigación mostraron una prevalencia del estado nutricional, de acuerdo con la clasificación de Waterlow, de 0.81 por ciento, 17 por ciento y 2 por ciento para el primer, segundo y tercer grado de desnutrición, respectivamente. En cambio con la clasificación de Gómez fue de 49 por ciento, 14 por ciento y 2 por ciento para leve, moderado y severo grados de desnutrición, respectivamente. Cuando se compararon las medias geométricas de los títulos de anticuerpos para P. falciparum y para P. vivax, usando la metodología de la clasificación de Waterlow se encontraron asociaciones estadísticas, detectándose que las medias geométricas para P. falciparum, fueron más altas en aquellos niños que no tuvieron desnutrición. Sin embargo para P. vivax las medias geométricas fueron más altas para aquellos niños con algún grado de desnutrición. Sin embargo, cuando se compararon la intensidad de la infección de los helmintos intestinales, la calidad de la vivienda y la duración de la lactancia no se detectaron diferencias significantes. Por lo tanto creemos conveniente continuar con este tipo de investigación, sobre todo con estudios de tipo longitudinal, a fin de detectar asociación causal en la relación nutrición/malaria

In order to determinate the prevalence of the nutritional situation in children under six year of age and to study the relation with malaria and intestinal parasitism and epidemiological study of a cross sectional was carried ou in Cordoba locality, Buenaventura Municipality in the Colombian Pacific Coast. One hundred and twenty eight children were studied to whom a questionnaire, a thick smear examination, and a serological test through the indirected inmunoflorescence reaction was practiced. Coproparasitoscopic examination were also done in addition to medical and clinical anthropometric examinations, the latter consisting of the measurements of weigth and heigth. The results of this investigation showed a prevalence of the nutritional state, according to Waterlow classification, of 0.81 percent, 17 percent and 2 percent for the first, second and thirt degree of malnutrition respectively. Instead, according to the Gómez classification it was 49 percent, 14 percent and 2 percent for the sligth, moderate and severe degrees of malnutrition. When the geometric mean of the antibody titles for P. falciparum and for P.vivax were compared, using the metodology of the Waterlow classification, statistical associations were discovered and it was found that the geometric mean for P. falciparum were heigher in those children that didn't have any malnutrition. Nevertheless, the geometric mean for P. vivax was higher for those children with a certain degree of malnutrition. Nevertheless, when the intensity of infection of the intestinal helminths, the quality of the dwelling and the breast fed time duration were compared, no significant differences were detected. therefore we belive it convenient to keep on with this type of investigation, specially with those longitudinal type studies so as to detect causal association in the relation nutrition/malaria.

Quimioterapia de la oncocercosis: evaluación del mebendazol solo y asociado con dietilcarbamazina / Drug therapy of onchocercosis: evaluation of mebenzole alone and in combination with diethylcarbamazine

El objetivo de este trabajo fue evaluar la eficacia del mebendazol(MEB) solo, o en combinación con dietilcarbamazina(DEC), en un estudio abierto, controlado, en pacientes infectados con Onchocerca volvulus. Se administró MEB a dosis de 50 mg/kg/día, durante 14 días a 7 pacientes con altas cuentas de microfilarias en piel. Otros 7 pacientes recebieron 2 g de MEB diarios por 14 días (promedio 44 mg/kg/día). Adicionalmente, a estos últimos pacientes, se les agregaron 3 mg/kg/día de DEC durante los últimos cuatro días de tratamiento. Los criterios para la selección de pacientes fueron: a) cuentas de microfilarias entre 15 y 100 por biopsia de piel; b) presencia de nódulos subcutáneos y c) ausencia de severo daño ocular y enfermedades sistémicas. Los resultados mostraron que la combinación de MEB más DEC fue ineficaz para prevenir las reacciones adversas causadas por la administraçäo de DEC. Esto fue debido a la ineficacia del MEB para disminuir la carga original de microfilarias en piel antes de la administración de DEC. El MEB, administrado a 50 mg/kg/día, durante 14 días, fue incapaz de inducir un descenso significativo y substancial de las cuentas de microfilarias en piel. Sin embargo, se observó una leve reducción en las cuentas de microfilarias en piel 15 días después de iniciada la administración de la droga. Los cambios más importantes a nivel ocular fueron detectados en el grupo de pacientes que recibieron MEB. Extradiordinariamente importante, fue la movilización de microfilarias observada en la cámara anterior de los ojos de los individuos que recibieron MEB sólo. Las reacciones sistémicas adversas fueron más aparentes tanto en frecuencia como en intensidad en los pacientes que recibieron MEB más DEC, que en los pacientes que recibieron MEB solo. En conclusión, MEB dado a la dosis de 50 mg/kg/día durante 14 días, fue ineficaz para disminuir las cuentas de microfilarias en pacientes infectados con Onchocerca volvulus

Quimioterapia de la onconcercosis: utilidad del mebendazol a nivel comunitario / Drug therapy of onchocercosis: use of mebendazole at communitary level

Resumen El mebendazol, compuesto que en un estudio controlado a nivel hospitalario demostró tener efecto sobre los adultos hembras y las microfilarias de Onchocerco volvulus. fue ahora evaluado en un estudio abierto comunitario para el tratamiento de la oncocercosis. Un total de 26 individuos de diferentes edades y sexos de una comunidad del foco endémico sur del estado de Chiapas, con diferentes densidades de microfilarias en la piel, fueron distribuidos en tres grupos de tratamiento: Grupo 1 formado por 11 hombres mayores de 14años que recibieron I g de mebendazol dos veces al día oralmente durante 4 semanas; Grupo 2 integrado por 6 mujeres mayores de 14 años que recibieron 100mg de dietilcarbamazina dos veces al día durante 4 semanas; y Grupo 3, de 9 menores de 14 aftas de ambos sexos, que recibieron 30 mg de mebendazol por Kg de peso al día. repartidos en dos tomas durante 4 semanas. En los grupos que recibieron mebendazol se observó una baja importante y sostenida en las densidades de microfiliarias, lo cual contrasta notablemente con lo observado en el grupo que recibió dietilcarbamazina. en quienes la baja de las densidades de microfilarias fue inmediata a la administración del medicamento (una semana) y a partir de los 6 meses se observ6 recuperación gradual en el número de microfilarias en la piel, persistiendo una alza lenta a los 14 meses posteriores al inicio del tratamiento. Los efectos secundarios se presentaron con más frecuencia y severidad en el grupo que recibió dietilcarbamazina que en los que se trataron con mebendazol. En ninguno de ellos se presentaron alteraciones oculares atribuibles al tratamiento. Estos resultados sugieren que el mebendazol es seguro y efectivo en el tratamiento de la oncocercosis en la comunidad y que puede ser preferible a la dietilcarbamazina