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1.
Am J Trop Med Hyg ; 104(4): 1394-1403, 2021 01 11.
Article in English | MEDLINE | ID: mdl-33432900

ABSTRACT

Onchocerciasis, caused by infection with Onchocerca volvulus, has been targeted for elimination by 2030. Currently, onchocerciasis elimination programs rely primarily on mass distribution of ivermectin. However, ivermectin alone may not be sufficient to achieve elimination in some circumstances, and additional tools may be needed. Vector control has been used as a tool to control onchocerciasis, but vector control using insecticides is expensive and ecologically detrimental. Community-directed removal of the trailing vegetation black fly larval attachment sites (slash and clear) has been shown to dramatically reduce vector biting densities. Here, we report studies to optimize the slash and clear process. Conducting slash and clear interventions at Simulium damnosum sensu stricto breeding sites located within 2 km of afflicted communities resulted in a 95% reduction in vector biting. Extending slash and clear further than 2 km resulted in no further decrease. A single intervention conducted at the first half of the rainy season resulted in a 97% reduction in biting rate, whereas an intervention conducted at the end of the rainy season resulted in a 94% reduction. Vector numbers in any of the intervention villages did not fully recover by the start of the following rainy season. These results suggest that slash and clear may offer an inexpensive and effective way to augment ivermectin distribution in the effort to eliminate onchocerciasis in Africa.


Subject(s)
Community Participation/methods , Insect Control/methods , Insect Vectors/parasitology , Onchocerca volvulus/pathogenicity , Onchocerciasis/prevention & control , Onchocerciasis/transmission , Simuliidae/parasitology , Animals , Humans , Hydrobiology/methods , Insect Bites and Stings/prevention & control , Onchocerciasis/epidemiology , Plants , Rain , Seasons , Simuliidae/physiology , Uganda
2.
Am J Trop Med Hyg ; 103(3): 1135-1142, 2020 09.
Article in English | MEDLINE | ID: mdl-32588807

ABSTRACT

Wambabya-Rwamarongo onchocerciasis focus is one of the eight foci Uganda verified using the WHO verification guidelines. The approach for elimination was twice yearly treatment with ivermectin for every round, treating at least 90% of all the eligible population. This was in combination with vector elimination using Abate® (BASF SE, Limburgerhof, Germany) since elimination nationwide policy was launched. From 2008 to 2013, the program distributed ivermectin with a mean treatment coverage of the ultimate treatment goal (UTG) or eligible population of 91.2%, with a range of 85-96%. In 2009, vector elimination based on ground larviciding had a dramatic impact on the Simulium vectors, as the last fly was observed in October 2009. No more Simulium vectors were observed during a period of at least 7 years, including the 3-year posttreatment surveillance (PTS) until the focus was reclassified as eliminated in August 2017. During the PTS period, none of the 10,578 trapped crabs were found infested with the aquatic stages of the vector. The last infested crab was observed in March 2010, and for at least 7 years, no infested crabs were observed. Serological surveys showed that of 2,978 young children examined in 2013, only one was OV16 positive (0.0%; 95% CI: 0-0.21). In 2017, after the PTS period, all 3,079 young children examined were negative for OV16 (95% CI: 0-0.16). Therefore, entomological and serological results provided evidence that resulted in the reclassification of Wambabya-Rwamarongo focus from "transmission interrupted" to "transmission eliminated" with no possibility of recrudescence.


Subject(s)
Antiparasitic Agents/therapeutic use , Brachyura/parasitology , Ivermectin/therapeutic use , Onchocerciasis/epidemiology , Simuliidae/parasitology , Temefos/therapeutic use , Animals , Disease Eradication , Humans , Onchocerciasis/parasitology , Onchocerciasis/transmission , Uganda/epidemiology
3.
Am J Trop Med Hyg ; 102(6): 1411-1416, 2020 06.
Article in English | MEDLINE | ID: mdl-32228786

ABSTRACT

Uganda has verified elimination of seven onchocerciasis foci since 2007 when the nationwide onchocerciasis elimination policy was launched. However, the Victoria Nile focus (which was eliminated in the early 1970s) had not been verified. The objective of this study was to verify this focus to the WHO verification guidelines and bring it in line with recently eliminated foci. Vector control with dichlorodiphenyltrichloroethane was the main intervention used at the Victoria Nile from the 1950s to the 1970s. Historical fly collection sites along River Nile were identified for recent fly collection. Relevant health workers near the sites were trained to supervise fly collection activity. With support from communities, fly collectors were identified, trained, and equipped to collect Simulium flies for at least a year. A total of 854 Simulium flies were collected and analyzed by polymerase chain reaction to detect Onchocerca volvulus DNA. The communities and their leaders provided consent for the collection of dry blood spots (DBS) from children younger than 10 years for investigation of recent exposure to the disease. A total of 2,953 DBS were collected and analyzed by OV16 ELISA to detect the presence of IgG4 antibodies recognizing the OV16 antigen. The results showed that none of the flies carried O. volvulus DNA. Similarly, all the children were OV16 negative, showing no exposure to onchocerciasis. All the flies collected were identified as Simulium adersi, which is not a known vector for O. volvulus. The results confirmed that onchocerciasis and its vector Simulium damnosum had been eliminated in the Victoria Nile focus.


Subject(s)
Disease Eradication , Onchocerciasis/epidemiology , Animals , Child , Humans , Insect Control , Insect Vectors , Onchocerciasis/prevention & control , Simuliidae , Uganda/epidemiology , World Health Organization
4.
Sci Rep ; 10(1): 4235, 2020 03 06.
Article in English | MEDLINE | ID: mdl-32144362

ABSTRACT

Concern is emerging regarding the challenges posed by spatial complexity for modelling and managing the area-wide elimination of parasitic infections. While this has led to calls for applying heterogeneity-based approaches for addressing this complexity, questions related to spatial scale, the discovery of locally-relevant models, and its interaction with options for interrupting parasite transmission remain to be resolved. We used a data-driven modelling framework applied to infection data gathered from different monitoring sites to investigate these questions in the context of understanding the transmission dynamics and efforts to eliminate Simulium neavei- transmitted onchocerciasis, a macroparasitic disease that causes river blindness in Western Uganda and other regions of Africa. We demonstrate that our Bayesian-based data-model assimilation technique is able to discover onchocerciasis models that reflect local transmission conditions reliably. Key management variables such as infection breakpoints and required durations of drug interventions for achieving elimination varied spatially due to site-specific parameter constraining; however, this spatial effect was found to operate at the larger focus level, although intriguingly including vector control overcame this variability. These results show that data-driven modelling based on spatial datasets and model-data fusing methodologies will be critical to identifying both the scale-dependent models and heterogeneity-based options required for supporting the successful elimination of S. neavei-borne onchocerciasis.


Subject(s)
Models, Theoretical , Onchocerciasis, Ocular/epidemiology , Onchocerciasis, Ocular/transmission , Simuliidae/parasitology , Algorithms , Animals , Humans , Insect Vectors/parasitology , Onchocerca , Onchocerciasis, Ocular/parasitology , Onchocerciasis, Ocular/prevention & control , Prevalence , Spatial Analysis
5.
Sci Rep ; 9(1): 15274, 2019 10 24.
Article in English | MEDLINE | ID: mdl-31649285

ABSTRACT

Attention is increasingly focusing on how best to accelerate progress toward meeting the WHO's 2030 goals for neglected tropical diseases (NTDs). For river blindness, a major NTD targeted for elimination, there is a long history of using vector control to suppress transmission, but traditional larvicide-based approaches are limited in their utility. One innovative and sustainable approach, "slash and clear", involves clearing vegetation from breeding areas, and recent field trials indicate that this technique very effectively reduces the biting density of Simulium damnosum s.s. In this study, we use a Bayesian data-driven mathematical modeling approach to investigate the potential impact of this intervention on human onchocerciasis infection. We developed a novel "slash and clear" model describing the effect of the intervention on seasonal black fly biting rates and coupled this with our population dynamics model of Onchocerca volvulus transmission. Our results indicate that supplementing annual drug treatments with "slash and clear" can significantly accelerate the achievement of onchocerciasis elimination. The efficacy of the intervention is not very sensitive to the timing of implementation, and the impact is meaningful even if vegetation is cleared only once per year. As such, this community-driven technique will represent an important option for achieving and sustaining O. volvulus elimination.


Subject(s)
Antiparasitic Agents/pharmacology , Insect Control/methods , Insect Vectors/drug effects , Ivermectin/pharmacology , Onchocerca volvulus/drug effects , Onchocerciasis, Ocular/prevention & control , Onchocerciasis, Ocular/transmission , Animals , Humans , Models, Theoretical
6.
PLoS Negl Trop Dis ; 13(7): e0007558, 2019 07.
Article in English | MEDLINE | ID: mdl-31310607

ABSTRACT

BACKGROUND: Onchocerciasis, or river blindness, has historically been an important cause of blindness, skin disease and economic disruption in Africa and the Americas. It is caused by the filarial parasite Onchocerca volvulus, which is transmitted by black flies in the genus Simulium. Over the past decade, several international programs have been formed to control, or more recently eliminate onchocerciasis, using mass drug administration (MDA) of ivermectin. However, in many areas of Africa (particularly those which are endemic for the eyeworm, Loa loa, or where vector densities are very high) ivermectin MDA alone will not be sufficient to achieve elimination. In these situations, additional interventions may be necessary. METHODOLOGY/PRINCIPAL FINDINGS: The Esperanza Window trap (EWT), a simple trap originally developed to replace human landing collections for entomological surveillance of O. volvulus transmission was optimized, resulting in a 17-fold improvement in trap performance. The optimized trap was tested in trials in schools and in agricultural fields to determine if it could reduce vector biting locally. The traps resulted in a 90% reduction in biting in the school setting. In the field setting, results varied. In one location, the traps reduced biting by roughly 50%, while in a separate trial, the traps did not significantly reduce the biting rate. Examination of the two settings suggested that trap placement may be critical to their success. CONCLUSIONS/SIGNIFICANCE: These results suggest that the optimized EWT might be capable of reducing local vector black fly biting in areas commonly frequented by residents. Together with other recently developed methods of community directed vector control, the traps may augment ivermectin MDA, bringing the goal of onchocerciasis elimination within reach in much of Africa.


Subject(s)
Insect Bites and Stings/prevention & control , Insect Control/instrumentation , Insect Vectors/physiology , Onchocerciasis/prevention & control , Simuliidae/physiology , Animals , Female , Humans , Insect Control/methods , Insect Vectors/parasitology , Loa/physiology , Onchocerca volvulus/physiology , Onchocerciasis/transmission , Onchocerciasis, Ocular/prevention & control , Onchocerciasis, Ocular/transmission , Schools , Simuliidae/parasitology , Uganda
7.
Infect Dis Poverty ; 8(1): 52, 2019 Jul 15.
Article in English | MEDLINE | ID: mdl-31303175

ABSTRACT

A recent article "Is onchocerciasis elimination in Africa feasible by 2025: a perspective based on lessons learnt from the African control programmes" in Infectious Diseases of Poverty claimed that undue influence on African programs by concepts developed by the Onchocerciasis Elimination Program of the Americas (OEPA) is detrimental to stopping mass drug administration (MDA) in Africa. This claim is made despite a record year for MDA stoppage in four African countries of > 3.5 million treatments in 2018, far exceeding any past OEPA or African Program for Onchocerciasis Control (APOC) stop MDA success.


Subject(s)
Disease Eradication/organization & administration , Filaricides/therapeutic use , Ivermectin/therapeutic use , Mass Drug Administration/standards , Onchocerciasis, Ocular/prevention & control , Africa , Americas , Animals , Humans , Onchocerca volvulus/physiology
8.
Am J Trop Med Hyg ; 100(5): 1208-1215, 2019 05.
Article in English | MEDLINE | ID: mdl-30915956

ABSTRACT

Mass drug administration (MDA) with ivermectin must reach a high treatment coverage (90% of the eligible population) if onchocerciasis is to be eliminated. Questions have been raised as to whether reported treatment figures reaching such high coverage are reliable. Sample surveys are proposed as the method of choice for "validating" reported coverage figures. The purpose of this study was to compare the district-level MDA coverage reported by programs with contemporaneous surveys of randomly selected respondents living in those same districts. Over an 8-year period, 19,219 households were selected using multistage random sampling; 38,433 adult male and female heads of those households were asked about their recent ivermectin MDA treatment experience. District coverage reports were considered "accurate" if they fell within the 95% CIs determined by the corresponding district's survey. Ninety-eight treatment rounds were evaluated over an 8-year period. Overall, the reported coverage of 96.5% (range: 68-100%) was significantly higher than the 92.5% surveyed coverage (range: 62.1-99.6%, 95% CI: 91.9-93.2%). However, only 20% of districts reported significantly higher coverage than surveys, 68% of district program reports were judged as accurate, and 12% of districts reported significantly lower coverage figures than their corresponding surveys. Eighty-eight percent of districts reported coverage ≥ 90% threshold for success, compared with 97% of surveys that included 90% in their 95% CIs. We conclude that when analyzed statistically at the district level, most surveys verified the reported coverage.


Subject(s)
Mass Drug Administration/statistics & numerical data , Onchocerciasis/prevention & control , Surveys and Questionnaires , Adult , Cameroon/epidemiology , Endemic Diseases/statistics & numerical data , Female , Filaricides/therapeutic use , Geography , Humans , Ivermectin/therapeutic use , Male , Onchocerciasis/drug therapy , Uganda/epidemiology
9.
Nat Commun ; 9(1): 4929, 2018 11 19.
Article in English | MEDLINE | ID: mdl-30451847

ABSTRACT

The original version of this Article contained an error in the spelling of Emily Griswold, which was incorrectly given as Emily Grisworld. This error has now been corrected in both the PDF and HTML versions of the Article.

10.
Nat Commun ; 9(1): 4324, 2018 10 18.
Article in English | MEDLINE | ID: mdl-30337529

ABSTRACT

Stopping interventions is a critical decision for parasite elimination programmes. Quantifying the probability that elimination has occurred due to interventions can be facilitated by combining infection status information from parasitological surveys with extinction thresholds predicted by parasite transmission models. Here we demonstrate how the integrated use of these two pieces of information derived from infection monitoring data can be used to develop an analytic framework for guiding the making of defensible decisions to stop interventions. We present a computational tool to perform these probability calculations and demonstrate its practical utility for supporting intervention cessation decisions by applying the framework to infection data from programmes aiming to eliminate onchocerciasis and lymphatic filariasis in Uganda and Nigeria, respectively. We highlight a possible method for validating the results in the field, and discuss further refinements and extensions required to deploy this predictive tool for guiding decision making by programme managers.


Subject(s)
Models, Biological , Parasitic Diseases/transmission , Surveys and Questionnaires , Elephantiasis, Filarial/diagnosis , Elephantiasis, Filarial/epidemiology , Elephantiasis, Filarial/parasitology , Elephantiasis, Filarial/transmission , Humans , Onchocerciasis/diagnosis , Onchocerciasis/epidemiology , Onchocerciasis/parasitology , Onchocerciasis/transmission , Parasitic Diseases/diagnosis , Parasitic Diseases/epidemiology , Parasitic Diseases/parasitology , Sample Size , Uganda/epidemiology
11.
PLoS Negl Trop Dis ; 12(8): e0006702, 2018 08.
Article in English | MEDLINE | ID: mdl-30148838

ABSTRACT

BACKGROUND: Onchocerciasis a neglected tropical disease that historically has been a major cause of morbidity and an obstacle to economic development in the developing world. It is caused by infection with Onchocerca volvulus, which is transmitted by black flies of the genus Simulium. The discovery of the potent effect of Mectizan (ivermectin) on O. volvulus microfilariae and the decision by its manufacturer to donate the drug for onchocerciasis spurred the implementation of international programs to control and, more recently, eliminate this scourge. These programs rely primarily on mass distribution of ivermectin (MDA) to the afflicted populations. However, MDA alone will not be sufficient to eliminate onchocerciasis where transmission is intense and where ivermectin MDA is precluded by co-endemicity with Loa loa. Vector control will likely be required as a supplemental intervention in these situations. METHODOLOGY/PRINCIPAL FINDINGS: Because biting by the black fly vectors is often a major nuisance in onchocerciasis afflicted communities, we hypothesized that community members might be mobilized to clear the breeding sites of the vegetation that represents the primary black fly larvae attachment point. We evaluated the effect of such a community based "slash and clear" intervention in multiple communities in Northern Uganda. Slash and Clear resulted in 89-99% declines in vector biting rates. The effect lasted up to 120 days post intervention. CONCLUSIONS/SIGNIFICANCE: Slash and clear might represent an effective, inexpensive, community- based tool to supplement ivermectin distribution as a contributory method to eliminate onchocerciasis and prevent recrudescence.


Subject(s)
Insect Control/methods , Insect Vectors/parasitology , Ivermectin/administration & dosage , Onchocerca volvulus/physiology , Onchocerciasis/prevention & control , Simuliidae/parasitology , Animals , Community Participation , Humans , Ivermectin/pharmacology , Mass Drug Administration , Neglected Diseases , Onchocerciasis/drug therapy , Onchocerciasis/epidemiology , Time Factors , Uganda/epidemiology
12.
Am J Trop Med Hyg ; 99(3): 749-752, 2018 09.
Article in English | MEDLINE | ID: mdl-30014821

ABSTRACT

Onchocerciasis is a neglected tropical disease targeted for elimination. The World Health Organization (WHO) has developed guidelines for the verification of onchocerciasis elimination that include entomological and epidemiological criteria. The latter require demonstrating with statistical confidence that the infection prevalence in children is less than 0.1%, necessitating an assay with a high degree of specificity. We present an analysis of the performance of the Onchocerciasis Elimination Program for the Americas (OEPA) version of the Ov16 enzyme-linked immunosorbant assay (ELISA) when used under operational conditions. In Africa and Latin America, the assay demonstrated 99.98% specificity in 69,888 children in 20 foci where transmission was believed to be interrupted. The assay produced a prevalence estimate equal to that of skin snip microscopy when applied in putatively hypo-endemic zones of Ethiopia. The OEPA Ov16 ELISA demonstrated the specificity required to be effectively deployed to verify transmission elimination under the WHO guidelines, while exhibiting a sensitivity equivalent to skin snip microscopy to identify hypo-endemic areas.


Subject(s)
Ivermectin/administration & dosage , Ivermectin/therapeutic use , Mass Drug Administration , Onchocerca volvulus , Onchocerciasis/drug therapy , Animals , Antibodies, Helminth , Child , Disease Eradication , Enzyme-Linked Immunosorbent Assay , Global Health , Humans , Seroepidemiologic Studies , Time Factors
13.
Int Health ; 10(suppl_1): i79-i88, 2018 03 01.
Article in English | MEDLINE | ID: mdl-29471335

ABSTRACT

Onchocerciasis causes severe itching, serious skin disease and ocular damage leading to visual impairment or permanent blindness. It is associated with hanging groin, epilepsy, Nakalanga dwarfism and, most recently, nodding disease. This disease affected communities in 17 transmission foci in 37 districts of Uganda, where about 6.7 million people are once at risk. The efforts against onchocerciasis in Uganda commenced in the late 1940s, when vector control was launched using dichlorodiphenyltrichloroethane; by 1973, Simulium damnosum had been eliminated in the Victoria focus. Success outside of the Victoria focus was short-lived due to changes in government priorities and the political upheavals of the 1970s and 1980s. With the return of political stability, annual treatment with ivermectin through mass drug administration was launched in the early 1990s. Control of the disease has been successful, but there has been failure in interrupting transmission after more than 15 years. In 2007 Uganda launched a nationwide transmission elimination policy based on twice-per-year treatment and vector control/elimination, with a goal of eliminating river blindness nationwide by 2020. By 2017, 1 157 303 people from six foci had been freed from river blindness. This is the largest population ever declared free under World Health Organization elimination guidelines, providing evidence that elimination of river blindness in Africa is possible.


Subject(s)
Disease Eradication/organization & administration , Onchocerciasis/prevention & control , Adult , Animals , Antiparasitic Agents/supply & distribution , Antiparasitic Agents/therapeutic use , Humans , Insect Control/organization & administration , Insect Vectors , Ivermectin/supply & distribution , Ivermectin/therapeutic use , Onchocerciasis/drug therapy , Uganda/epidemiology
14.
Int Health ; 10(suppl_1): i60-i70, 2018 03 01.
Article in English | MEDLINE | ID: mdl-29471337

ABSTRACT

National onchocerciasis elimination committees (NOECs) serve to help ministries of health complete the pathway to successful verification of elimination of onchocerciasis (river blindness), as outlined in the 2016 World Health Organization guidelines. These guidelines, however, only take effect when the country believes it has reached a point that elimination can be demonstrated, and do not address the preceding milestones. Therefore, NOECs can be of great help with guiding and tailoring earlier planning, programming and assessments to empower national programs to aggressively move toward their countries' elimination goals. In this article, we provide suggestions for organizing NOECs and examples of four such committees that have successfully operated in Africa and the Americas.


Subject(s)
Disease Eradication/organization & administration , Internationality , Onchocerciasis/prevention & control , Africa , Americas , Developing Countries , Disease Eradication/standards , Guidelines as Topic , Humans , Onchocerciasis, Ocular/prevention & control , World Health Organization
15.
PLoS One ; 12(12): e0189306, 2017.
Article in English | MEDLINE | ID: mdl-29253862

ABSTRACT

INTERVENTION: Few studies have documented the interruption of onchocerciasis and Lymphatic Filariasis (LF) by integrated chemotherapy in Uganda. The study describes the interruption of transmission of the two diseases co-endemic in Obongi focus, north western Uganda. Base line data for Onchocerciasis and LF were collected in 1994 and 2006, respectively. Annual mass drug administration for onchocerciasis (Ivermectin) and Lymphatic Filariasis (Ivermectin + albendazole) was conducted for 20 and 6 years, respectively. Thereafter, assessments by skin snip, larval searches in rivers and human landing catches were performed. Children <10 years were screened for IgG4 antibodies using Ov16 ELISA technique in 2013. LF Pre-TAS and TAS1 were conducted in sentinel sites. ITN coverage and utilization for the implementation unit was also reported. INTERVENTION COVERAGE: Onchocerciasis treatment coverage was <80% but improved with the introduction of CDTI in 1999. While for LF, effective coverage of >65% was achieved in the six treatment rounds. Household ownership of ITN's and utilization was 96% and 72.4%., respectively. IMPACT: Parasitological examinations conducted for onchocerciasis among 807 adults and children, revealed a reduction in mf prevalence from 58% in 1994 to 0% in 2012. Entomological monitoring conducted at the two sites had no single Simulium damnosum fly caught. Serological analysis using Ov16 ELISA for onchocerciasis revealed that out of the 3,308 children <10 years old screened in 2013, only 3/3308 (0.091%) positive cases were detected. All Ov16 positive children were negative when tested for patent infection by skin snip PCR. A reduction in LF microfilaria prevalence from 2.5% (n = 13/522) in 2006 to 0.0% (n = 602) in 2014 was observed. LF TAS1 conducted in 2015 among 1,532 children 6-7 years, all were negative for antigens of W. bancrofti. CONCLUSION: The results concluded that interruption of onchocerciasis and LF has been achieved.


Subject(s)
Antiparasitic Agents/therapeutic use , Elephantiasis, Filarial/drug therapy , Onchocerca volvulus , Onchocerciasis/drug therapy , Wuchereria bancrofti , Adolescent , Albendazole/administration & dosage , Animals , Child , Child, Preschool , Elephantiasis, Filarial/epidemiology , Enzyme-Linked Immunosorbent Assay , Female , Humans , Immunoglobulin G/blood , Ivermectin/administration & dosage , Male , Onchocerciasis/epidemiology , Prevalence , Uganda
16.
Am J Trop Med Hyg ; 97(6): 1843-1845, 2017 Dec.
Article in English | MEDLINE | ID: mdl-29187277

ABSTRACT

Previous studies have demonstrated that the presence of larvae of other filarial species in Simulium damnosum sensu lato can distort estimates of transmission potential for Onchocerca volvulus in West Africa. However, studies conducted in foci of onchocerciasis in West Central Uganda indicated that larvae other than O. volvulus were not common in vectors collected there. Recent data collected in Northern Uganda revealed a striking discordance between estimates of the prevalence of flies carrying O. volvulus infective larvae obtained from molecular pool screening and dissection methods. To resolve this discrepancy, sequences from three mitochondrially encoded genes were analyzed from the larvae collected by dissection. All larvae analyzed were Onchocerca ochengi v. Siisa, a parasite of cattle, or Onchocerca ramachandrini, a parasite of warthogs. These results suggest that nonhuman parasite larvae are common in vectors in Northern Uganda, underscoring the necessity for molecular identification methods to accurately estimate O. volvulus transmission.


Subject(s)
Onchocerca/isolation & purification , Simuliidae/parasitology , Animals , Cattle/parasitology , Cattle Diseases/parasitology , Insect Vectors/parasitology , Larva , Onchocerca/classification , Onchocerciasis/diagnosis , Onchocerciasis/veterinary , Swine/parasitology , Swine Diseases/parasitology , Uganda
17.
Am J Trop Med Hyg ; 97(4): 1235-1242, 2017 Oct.
Article in English | MEDLINE | ID: mdl-29031285

ABSTRACT

Entomological measures of transmission are important metrics specified by the World Health Organization to document the suppression and interruption of transmission of Onchocerca volvulus, 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 Simulium damnosum s.l., the primary vector of O. volvulus 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 S. damnosum 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 O. volvulus transmission.


Subject(s)
Onchocerca volvulus/physiology , Simuliidae/physiology , Simuliidae/parasitology , Animal Distribution/drug effects , Animals , Humans , Pheromones/pharmacology , Uganda/epidemiology
18.
Am J Trop Med Hyg ; 95(2): 417-425, 2016 08 03.
Article in English | MEDLINE | ID: mdl-27215297

ABSTRACT

It was not until early 1990s that, when the Imaramagambo focus of southwest Uganda was mapped, mass treatment with a single annual dose of ivermectin for onchocerciaisis control commenced. However, comprehensive investigations on its transmission were launched after a nationwide policy for onchocerciasis elimination in 2007. Entomological surveys throughout the focus from 2007 to 2015 have yielded few or no freshwater crabs (Potamonautes aloysiisabaudiae), which serve as the obligate phoretic host of the larvae and pupae of the vector Simulium neavei No S. neavei flies have been observed or collected since 2007. Skin snips (microscopy) from 294 individuals in 2008 were negative for skin microfilariae, and of the 462 persons analyzed by polymerase chain reaction skin snip poolscreen in 2009, only five (1.08%) persons were indicated as infected with onchocerciasis. All five of the positive persons were at least 40 years old. Serosurvey results showed negative exposure among 3,332 children in 2012 and 3,108 children in 2015. Both were within the upper bound of the 95% confidence interval of the prevalence estimate of 0.06%, which confirmed the elimination of onchocerciasis. Treatment coverage in Imaramagambo was generally poor, and transmission interruption of onchocerciasis could not be attributed solely to annual mass treatment with ivermectin. There was sufficient evidence to believe that the possible disappearance of the S. neavei flies, presumed to have been the main vector, may have hastened the demise of onchocerciasis in this focus.


Subject(s)
Disease Eradication , Larva/pathogenicity , Onchocerca volvulus/pathogenicity , Onchocerciasis/epidemiology , Onchocerciasis/transmission , Adult , Animals , Anthelmintics/therapeutic use , Brachyura/parasitology , Epidemiological Monitoring , Fresh Water/parasitology , Humans , Incidence , Insect Vectors/parasitology , Ivermectin/therapeutic use , Larva/physiology , Onchocerca volvulus/isolation & purification , Onchocerca volvulus/physiology , Onchocerciasis/diagnosis , Onchocerciasis/parasitology , Simuliidae/parasitology , Uganda/epidemiology
19.
Int Health ; 8(2): 116-23, 2016 Mar.
Article in English | MEDLINE | ID: mdl-26152231

ABSTRACT

BACKGROUND: The community-directed intervention (CDI) approach has improved treatment coverage in onchocerciasis-affected communities. However, there is still a lot to learn. This study assessed its performance and highlighted the lessons learnt so far. METHODS: Representative samples of households were selected from Cameroon and Uganda program areas through multi-stage random sampling. An adult male and female from every selected household were interviewed separately on their involvement in CDI activities every year between 2004 and 2010. Community health workers (CHWs) were interviewed and treatment records reviewed to determine whether 90% treatment coverage was attained within 2 weeks. Records related to training of CHWs and their supervisors were analyzed. RESULTS: Decision making decreased for community leaders and health workers, while it increased for community members. The proportion of CHWs attaining 90% treatment coverage within 2 weeks improved as their demand for monetary incentives, and number of persons they served, reduced. The number of CHWs supervised by a community supervisor remained low, but increased for the health workers. The cost of training a CHW and a community supervisor reduced to about US$1 and US$4.8, respectively. CONCLUSIONS: The CDI approach was effective, culturally appropriate and probably less costly in delivering health services in low-resource communities.


Subject(s)
Community Health Services/organization & administration , Community Health Workers/organization & administration , Community Participation/methods , Onchocerciasis/drug therapy , Cameroon/epidemiology , Community Health Services/economics , Community Health Workers/education , Decision Making , Family Characteristics , Filaricides , Humans , Ivermectin/therapeutic use , Uganda/epidemiology
20.
Am J Trop Med Hyg ; 90(6): 1159-66, 2014 Jun.
Article in English | MEDLINE | ID: mdl-24686740

ABSTRACT

The study determined that Simulium neavei-transmitted onchocerciasis in Mount Elgon onchocerciasis focus had been interrupted. Annual mass treatment with ivermectin changed to two times per year along with vector elimination in 2007. Then, baseline microfilaria (mf) prevalence data of 1994 in five sentinel communities were compared with follow-up data in 2005 and 2011. Blood spots from 3,051 children obtained in 2009 were analyzed for Onchocerca volvulus immunoglobulin G4 antibodies. Fresh water crab host captures and blackflies collected indicated their infestation with larval stages of S. neavei and presence or absence of the vector, respectively. Mf rates dropped from 62.2% to 0.5%, and 1 (0.03%) of 3,051 children was positive for O. volvulus antibodies. Crab infestation dropped from 41.9% in 2007 to 0%, and S. neavei biting reduced to zero. Both remained zero for the next 3 years, confirming interruption of onchocerciasis transmission, and interventions were halted.


Subject(s)
Antibodies, Helminth/blood , Brachyura/parasitology , Insect Vectors/parasitology , Onchocerca volvulus/physiology , Onchocerciasis/transmission , Simuliidae/parasitology , Adolescent , Animals , Antiparasitic Agents/therapeutic use , Child , Child, Preschool , Humans , Infant , Ivermectin/therapeutic use , Larva , Male , Microfilariae , Onchocerca volvulus/immunology , Onchocerciasis/drug therapy , Onchocerciasis/prevention & control , Prevalence , Uganda/epidemiology
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