Evidence of suppression of onchocerciasis transmission in the Venezuelan Amazonian focus.

BACKGROUND: The World Health Organization (WHO) has set goals for onchocerciasis elimination in Latin America by 2015. Most of the six previously endemic countries are attaining this goal by implementing twice a year (and in some foci, quarterly) mass ivermectin (Mectizan®) distribution. Elimination of transmission has been verified in Colombia, Ecuador and Mexico. Challenges remain in the Amazonian focus straddling Venezuela and Brazil, where the disease affects the hard-to-reach Yanomami indigenous population. We provide evidence of suppression of Onchocerca volvulus transmission by Simulium guianense s.l. in 16 previously hyperendemic Yanomami communities in southern Venezuela after 15 years of 6-monthly and 5 years of 3-monthly mass ivermectin treatment. METHODS: Baseline and monitoring and evaluation parasitological, ophthalmological, entomological and serological surveys were conducted in selected sentinel and extra-sentinel communities of the focus throughout the implementation of the programme. RESULTS: From 2010 to 2012-2015, clinico-parasitological surveys indicate a substantial decrease in skin microfilarial prevalence and intensity of infection; accompanied by no evidence (or very low prevalence and intensity) of ocular microfilariae in the examined population. Of a total of 51,341 S. guianense flies tested by PCR none had L3 infection (heads only). Prevalence of infective flies and seasonal transmission potentials in 2012-2013 were, respectively, under 1% and 20 L3/person/transmission season. Serology in children aged 1-10 years demonstrated that although 26 out of 396 (7%) individuals still had Ov-16 antibodies, only 4/218 (2%) seropositives were aged 1-5 years. CONCLUSIONS: We report evidence of recent transmission and morbidity suppression in some communities of the focus representing 75% of the Yanomami population and 70% of all known communities. We conclude that onchocerciasis transmission could be feasibly interrupted in the Venezuelan Amazonian focus.

Aedes (Stegomyia) albopictus (Skuse) (Diptera: Culicidae) en los estados Monagasy Guárico, Venezuela / Aedes (Stegomyia) albopictus (Skuse) (Diptera: Culicidae) in the states of Monagas and Guarico, Venezuela

Aedes albopictus (Skuse, 1894), vector responsable de la transmisión del dengue y otros virus es por primera vez reportado en las localidades de Voladero del estado Monagas al oriente del país y en las localidades 5 de Julio y Banco Obrero en el estado Guárico. Se realizaron colectas de adultos posándose sobre humanos y fases inmaduras en un recipiente plástico y en plantas de la familia Araceae con abundante materia orgánica, en el solar de una vivienda. Este reporte nos alerta para extremar la vigilancia entomológica a nivel nacional, determinar la distribución del vector en el país y diseñar estrategias de control.

Aedes albopictus (Skuse, 1894), vector responsible for the transmission of dengue and other viruses, is first recorded in the locality of Voladero, Monagas state, east of the country and in the towns July 5 and Banco Obrero, in the state Guárico. Collections were performed for adult human landing and for immature stages in a plastic container and in plants of the family Araceae with abundant organic matter, on the back yard of a house. This report alerts us to exercise extreme national entomological surveillance to determine the vector distribution in the country and control strategies.

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.

Evaluación de la eficacia de drogas antihelmínticas para el control de Trichuris trichiura y otras helmintiasis en el estado Aragua, Venezuela / Evaluation of the efficacy of antihelmintic drugs for the control of Trichuris trichiura and other helminthic diseases in the state of Aragua, Venezuela

Un ensayo clínico de cuatro brazos fue llevado a cabo en 14 comunidades del estado Aragua para evaluar cuatro esquemas de tratamientos antihelmínticos para geohelmintos: Mebendazol y albendazol como monoterapias y cada una de estas drogas en combinación con ivermectina como terapias combinadas. Los tratamientos fueron administrados posteriormente a un examen coproparsitoscópico inicial, con reevaluaciones a los 7 y 21 días. Quedó en evidencia que las tasas de curación observadas a los 7 días posteriores al tratamiento, a favor de los esquemas combinados, particularmente la combinación albendazol + ivermectina (χ2 = 10,85; P < 0,0009), pero no se reflejaron a los 21 días después de la administración de los tratamientos y ningún esquema demostró una eficacia superior. Trichuris trichiura aún responde satisfactoriamente a los tratamientos convencionales. A pesar de la similitud en la eficacia de las monoterapias y terapias combinadas, el porcentaje de pacientes curados con T. trichiura solo o con infecciones mixtas fue elevada (> 93%). Las uncinarias fueron curadas en 100% (cero huevos en heces), seguido de A. lumbricoides (98,2%) y las infecciones mixtas de T. trichiura + A. lumbricoides + uncinarias (100%). La reducción porcentual de huevos por gramo de heces fue de 100% para las uncinarias, 89,3% para A. lumbricoides y 81,7% para T. trichiura. Las tasas de fracasos fueron bajas para los cuatro esquemas terapéuticos: mebendazol (5,14%), albendazol (6,20%), albendazol + ivermectina (2,02%) y mebendazol + ivermectina (2,22%). El grupo de edad de 0 a 9 años registró el mayor número de fracasos terapéuticos (n = 13). Quizás convendría emplear esquemas combinados en casos de fracasos terapéuticos. Pero, surge la duda si se está evidenciando la posibilidad de resistencia a estos medicamentos, dado que la mayoría de los fracasos terapéuticos se observaron en pacientes con bajas cargas parasitarias que bien podrían revertirse en el tiempo.

A four-arm clinical trial was carried out in 14 communities in the State of Aragua to evaluate four antihelminthics treatments, as monotherapy and combined treatments for soil-transmitted helminthiasis: Mebendazole, albendazole and each of these drugs in combination with ivermectin. Treatments were given after an initial stool specimens were obtained for examination, with two sequential stool reevaluations on days 7 and 21. Cure rates (zero eggs in stools) at day 7 after treatments were favourable for combined treatments, specially albendazole + ivermectin (χ2 = 10.85; P < 0.0009), which was not reflected by day 21 since no treatment showed any superior efficacy. Trichuris trichiura still responds satisfactorily to conventional treatments offered by the national Programme for the Fight against Anclyostomiasis and other Intestinal Parasites. Notwithstanding the similarities of monotherapy and combined treatments efficacy, the percentage of patients cured with T. trichiura solely or with mixed infections was high (> 93%). Hookworm infections were cured a 100% (zero eggs found in feces), followed by A. lumbricoides (98.2%) and mixed infections by T. trichiura + A. lumbricoides + hookworms (100%). However, the mean egg reduction percent was also a 100% for hookworms, 89.3% for A. lumbricoides and 81.7% for T. trichiura. The rates of treatment failure were limited, albendazole 6.20%, mebendazole 5.14%, for the combination of albendazole + ivermectin 2.02% and for mebendazole + ivermectine 2.22%. The majority of treatment failures were seen in the 0-9 age group. It is perhaps convenient to use combined schemes in cases of treatment failure. But, there is doubt as to whether there is the possibility of resistance to these drugs given that the majority of treatment failures observed in patients with low intensity infections which might be subdued in time.

Vector competence of Simulium oyapockense s.l. and S. incrustatum for Onchocerca volvulus: Implications for ivermectin-based control in the Amazonian focus of human onchocerciasis, a multi-vector-host system.

Although it is now well established that in the Amazonian onchocerciasis focus, straddling between Venezuela and Brazil, the main vectors in the highland (hyperendemic) and lowland (hypoendemic) areas, are respectively Simulium guianense sensu lato Wise and S. oyapockense s.l. Floch and Abonnenc, investigation of the vectorial role of a third anthropophagic species, Simulium incrustatum Lutz has remained inconclusive. Here we compare the vector competence of S. incrustatum with that of S. oyapockense s.l. by conducting, in the Venezuelan part of the focus, a series of feeding experiments designed to analyze their relative: (a) microfilarial intakes when fed upon the same skin load; (b) proportions of microfilariae (mf) surviving damage inflicted by the cibarial armature (present in both species); and (c) infective (L3) larval outputs. Although the ability of S. oyapockense s.l. to ingest mf, for a given microfilaridermia, was markedly higher than that of S. incrustatum, the (density-dependent) proportions of those ingested mf that were damaged by the armature were also consistently higher, with the resulting output of L3 larvae being significantly lower in S. oyapockense s.l. than in S. incrustatum. These results indicate that S. incrustatum plays a more important role in onchocerciasis transmission in the Amazonian focus than previously realized. We discuss the implications of our findings for the control and elimination of onchocerciasis with mass administration of ivermectin in this focus, where the three main anthropophagic species often co-occur.