Interruption of the transmission of Onchocerca volvulus in the Kashoya-Kitomi focus, western Uganda by long-term ivermectin treatment and elimination of the vector Simulium neavei by larviciding

Lakwo, Thomson; Garms, R.; Wamani, J.; Tukahebwa, Edridah M.; Byamukama, Edson; Onapa, Ambrose; Tukesiga, Ephraim; Katamanywa, James; Begumisa, Stephen; Habomugisha, Peace; Oguttu, David; Richards, Frank O.; Unnasch, Thomas R.; Katabarwa, Moses

doi:10.1016/j.actatropica.2016.12.029

Cited by 36 publications

(35 citation statements)

References 27 publications

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“…After MDA in the Wadelai focus, it was confirmed that onchocerciasis had been eliminated in 2010 but this was probably partly attributable to the earlier disappearance of the vectors for environmental reasons [36]. Elimination of S. neavei combined with MDA has stopped transmission in the Kashoya-Kitomi focus [37].…”

Section: Ugandamentioning

confidence: 99%

Factors affecting onchocerciasis transmission: lessons for infection control

Cheke

2017

Expert Review of Anti-infective Therapy

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Introduction: Onchocerca volvulus infects in excess of 15 million people. The vectors are Simulium blackflies, varieties of which differ in their ecologies, behaviour and vectorial abilities. Control of the vectors and mass administrations of ivermectin have succeeded in reducing prevalences with elimination achieved in some foci, particularly in Central and southern America. In Africa, progress towards elimination has been less successful.Areas covered: Even with community directed treatment with ivermectin (CDTI), control has been difficult in African areas with initial prevalences in excess of 55%, especially if only annual treatments are dispensed. This is partly attributable to insufficient coverage, but the appearance of incipiently resistant non-responding parasites and lack of attention to vector biology in modelling and planning outcomes of intervention programmes have also played their parts, with recrudescence now appearing in some treated areas. Expert commentary:The biology of onchocerciasis is complex involving different vectors with differing abilities to transmit parasites, diverse pathologies related to geographical and parasite variations and endosymbionts in both parasite and vector. Modelling to predict epidemiological and control outcomes is addressing this complexity but more attention needs to be given to the vectors' roles to further understanding of where and when control measures will succeed.

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Section: Ugandamentioning

confidence: 99%

Factors affecting onchocerciasis transmission: lessons for infection control

Cheke

2017

Expert Review of Anti-infective Therapy

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“…Alternatively, loop-mediated isothermal ampli cation (LAMP) is a simple molecular method which rapidly synthesizes large amounts of DNA within 60 minutes and which is less sensitive to impure DNA preparations and has higher ampli cation e ciency than PCR [21,22,[29][30][31][32]. In addition, LAMP does not require any expensive equipment and thus it is easier to use in low resource-settings [33][34][35][36]. LAMP assays targeting O-150 and the mitochondrial cox1 gene have been established for the diagnosis of onchocerciasis [21,22,34].…”

Section: Introductionmentioning

confidence: 99%

“…In addition, LAMP does not require any expensive equipment and thus it is easier to use in low resource-settings [33][34][35][36]. LAMP assays targeting O-150 and the mitochondrial cox1 gene have been established for the diagnosis of onchocerciasis [21,22,34].…”

Section: Introductionmentioning

confidence: 99%

Differential susceptibility of Onchocerca volvulus microfilaria to ivermectin in two areas of contrasting history of mass drug administration in Cameroon: Relevance of microscopy and molecular techniques for the monitoring of skin microfilarial repopulation within six months of direct observed treatment

Abong

Amambo

Ndongmo

et al. 2020

Preprint

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Background. Ivermectin is an excellent microfilaricide against Onchocerca volvulus. However, in some regions, long term use of ivermectin has resulted in sub-optimal responses to the treatment. More data to properly document the phenomenon in various contexts of ivermectin mass drug administration (IVM-MDA) is needed. Also, there is a need to accurately monitor a possible repopulation of skin by microfilariae following treatment. Skin snip microscopy is known to have a low sensitivity in individuals with light infections, which can be the case following treatment. This study was designed with two complementary objectives: (i) to assess the susceptibility of O. volvulus microfilariae to ivermectin in two areas undergoing IVM-MDA for different lengths of time, and (ii) to document the repopulation of skin by the O. volvulus microfilariae following treatment, using 3 independent diagnostic techniques.Method. Identified microfilaridermic individuals were treated with ivermectin and re-examined after 1, 3, and 6 months using microscopy, real-time PCR and LAMP assays. Susceptibility to ivermectin and trends in detecting reappearance of skin microfilariae were determined using three techniques. Microscopy was used as an imperfect gold standard to determine the performance of real-time PCR and LAMP.Results. In Bafia with over 20 years of IVM-MDA, 11/51 (21.6%) treated microfilaridemic participants where still positive for skin microfilariae after 1 month. In Melong, with 10 years of IVM-MDA, 2/29 (6.9%) treated participants were still positive. The microfilarial density reduction per skin biopsy within one month following treatment was significantly lower in participants from Bafia.In both study sites, the molecular techniques detected higher proportions of infected individuals than microscopy at all monitoring time points. LAMP demonstrated the highest levels of sensitivity and real-time PCR was found to have the highest specificity.Conclusion. Patterns in skin mirofilarial clearance and repopulation were established. O. volvulus worms from Bafia with higher number of annual MDA were less susceptible to ivermectin. Molecular assays displayed higher sensitivity in monitoring O. volvulus microfilaridemia within six months following treatment.

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“…13 Similar success stories have been recently recorded in Africa, including Mali and Senegal, 14 Sudan, 15 and several foci in Uganda. [16][17][18][19][20] These successes resulted in the need to develop standardized metrics that can be used by the international community to verify that onchocerciasis has been eliminated. The World Health Organization (WHO) responded to this need, recently issuing a revised set of guidelines outlining the type of data that must be collected for a country to be verified as having eliminated onchocerciasis.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Community-Directed Operation of Black Fly Traps for Entomological Surveillance of Onchocerca volvulus Transmission in the Madi-Mid North Focus of Onchocerciasis in Northern Uganda

Loum

Katholi

Lakwo

et al. 2017

The American Journal of Tropical Medicine and Hygiene

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Entomological measures of transmission are important metrics specified by the World Health Organization to document the suppression and interruption of transmission of , the causative agent of onchocerciasis. These metrics require testing of large numbers of vector black flies. Black fly collection has relied on human landing collections, which are inefficient and potentially hazardous. As the focus of the international community has shifted from onchocerciasis control to elimination, replacement of human landing collections has become a priority. The Esperanza window trap (EWT) has shown promise as an alternative method for collection of s.l., the primary vector of in Africa. Here, we report the results of a community-based trial of the EWT in northern Uganda. Traps operated by residents were compared with human landing collections in two communities over 5 months. Three traps, when operated by a single village resident, collected over four times as many as did the two-men collection team. No significant differences were noted among the bait formulations. The results suggest that EWTs may be effectively operated by community residents and that the trap represents a viable alternative to human landing collections for entomological surveillance of transmission.

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Interruption of the transmission of Onchocerca volvulus in the Kashoya-Kitomi focus, western Uganda by long-term ivermectin treatment and elimination of the vector Simulium neavei by larviciding

Cited by 36 publications

References 27 publications

Factors affecting onchocerciasis transmission: lessons for infection control

Factors affecting onchocerciasis transmission: lessons for infection control

Evaluation of Community-Directed Operation of Black Fly Traps for Entomological Surveillance of Onchocerca volvulus Transmission in the Madi-Mid North Focus of Onchocerciasis in Northern Uganda

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