Interruption of Onchocerca volvulus transmission in Northern Venezuela

Abstract

BackgroundOnchocerciasis 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.MethodsIn-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.ResultsFrom 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.ConclusionsThese 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.

One Hundred Years After Its Discovery in Guatemala by Rodolfo Robles, Onchocerca volvulus Transmission Has Been Eliminated from the Central Endemic Zone

“…4 Together these three foci account for 60% of the population at risk in the Americas. MDA has been halted in all three of these foci, 28,29 but only south Chiapas and the CEZ have completed PTS. Overall, MDA has been stopped in 11 of the 13 American foci; the only active MDA program for onchocerciasis in the Americas at this time is in a cross-border focus (shared by Brazil and Venezuela) in the Amazon jungle.…”

Neglected Tropical Diseases - Latin America and the Caribbean

“…1), which differ greatly in their ability to transmit the parasite, or their vectorial capacity. in this respect (Convit et al 2013). Vector competence is dramatically influenced by the presence or absence of an anatomical structure known as the cibarial armature (Duke 1970;Reid 1994;Basanez et al 2000).…”

Impact of Livestock Farming on Human Onchocerciasis in Adamawa and North Regions Cameroon

“…The female worms produce thousands of microfilariae that cross embryonic fibrous tissue and invade the epidermis [8]. O. volvulus embryonic forms migrate through the skin and causes severe itching, disfiguration, and ocular lesions [9]. Keratitis and blindness can be the result of heavy parasite loads in the human host over time.…”

“…Keratitis and blindness can be the result of heavy parasite loads in the human host over time. The parasite is encapsulated in fibrous tissue [9]. The female adult worm measures 30 cm to 80 cm long while the male measures 3 cm to 5 cm [8].…”