Recrudescence of onchocerciasis in the Comoé valley in Southwest Burkina Faso

doi:10.1016/j.actatropica.2016.11.003

Acta Tropica

Volume 166, February 2017, Pages 96-105

https://doi.org/10.1016/j.actatropica.2016.11.003 Get rights and content

Highlights

•
Vector control along the Comoé river ceased in 1989 after 20 years, and prevalence of onchocerciasis dropped below 5%.
•
In 2001 the prevalence was found to have increased to 39% in one community, and by 2007 was over 5% in two other villages.
•
Surveys in 2011 and 2012 have shown that prevalence had risen above 5% in 13 out of 30 villages in the Comoé valley.
•
Onchocerciaasis prevalence had risen in spite of mass administration of ivermectin against lymphatic filariasis since 2004.
•
Prevalences have remained low in six communities surveyed in the adjacent Léraba river valley.

Abstract

Onchocerciasis control by vector control was instigated in southwest Burkina Faso in January 1969 by ORSTOM/OCCGE, and continued until operations were taken over by the WHO Onchocerciasis Control Programme (OCP) in February 1975, which itself ceased operations in the area in 1989 when onchocerciasis was judged to have been reduced to insignificant levels. Initially (1969–1975) vector immigration maintained unacceptably high levels of transmission, but OCP was much larger than the preceding campaign and in 1975 the Annual Transmission Potential (ATP) dropped below 100 at all sites in the Comoé river valley except Folonzo, which continued to be subject to reinvasion, along with the whole of the Léraba river valley. However, after the southern extension of the OCP in 1979, ATPs dropped below 100 everywhere in the Comoé basin (including the Léraba valley), and further dropped to insignificant levels after the western extension of the OCP in 1985. Thus transmission dropped more quickly in the Comoé river valley than the Léraba river valley (which had been subject to vector reinvasion), and this was also reflected in prevalence of microfilaraemia in the human population. After 1986 prevalence was less than 5% in all villages in the Comoé river valley (except for two, which subsequently dropped to 0% and 3.7% by 1999). However, in 2001 (12 years after the cessation of vector control) the prevalence in one village in the Comoé river valley had increased to 39.6%, and two more had increased above 5% by 2007. New epidemiological surveys in 2011 and 2012 showed that in 13 out of 30 villages in the Comoé river valley prevalence of microfilaraemia was above 5%, although this was not observed in the Léraba river valley where prevalence remained low. This is the first documented case of recrudescence of onchocerciasis in the old OCP area, and the reasons are not clear. It is possible that there has been immigration of parasites with humans or vectors from areas where there has been a shorter period of control, or that control has been less effective. It is possible that in spite of very low levels of transmission the local parasite population was never reduced to a level below the transmission breakpoint, or that there has been a local recrudescence due to stochastic population effects. In any case it is clear that the distribution of ivermectin against lymphatic filariasis in the area since 2004 has failed to prevent the recrudescence of onchocerciasis, and the Burkina Faso Programme National de Lutte contre l’Onchocercose (PNLO − Ministere de la Santé) has instigated a programme of Community Directed Treatment with Ivermectin specifically aimed at onchocerciasis in accordance with the strategy developed by APOC and recommended to governments by OCP when it was dissolved in 2002.

Graphical abstract

Onchocerciasis was considered eliminated by more than 20 years of vector control in the Comoé river basin, but it has been found to have recrudesced.

Section snippets

Historical introduction

In 1974 the World Health Organisation Onchocerciasis Control Programme (OCP) began operations with the objective “to eliminate onchocerciasis as a disease of public health importance and socio-economic importance” in the Volta river basin of West Africa (Boatin et al., 1997). The OCP was located in this area because there was already a significant body of knowledge concerning the clinical aspects of the disease, its entomology, parasitology, epidemiology and socio-economics (PNUD, 1972,

Description the study area

The Comoé basin in SW Burkina Faso includes both the Comoé and Léraba river valleys, and is situated in the southern sudan savannah vegetation zone (=sudano-guinea savannah) with annual rainfall mostly between 900 and 1100 mm (but reaching 1300 mm near the border with Côte d’Ivoire). There are two seasons, a wet season from April to October in which the SW monsoon wind predominates and a dry season in which the NE dry harmattan wind predominates. The temperature usually lies between 39 °C and 17

Identifying the recrudescence

Historical and new results for the prevalence and CMFL in all villages surveyed epidemiologically in the Comoé basin from 1973 to 2011 are shown in Supplementary material Table 1, and as separate time-series for the villages along the Léraba and Comoé valleys in Fig. 2, Fig. 3, and the geographic distribution of prevalence of onchocerciasis in the villages surveyed in 2010/2011 is shown in Fig. 4. Current WHO elimination guidelines (WHO, 2016) make no recommendations on the issue of

Instigation of community directed treatment with ivermectin in the Comoé valley

Whatever the reason for the recrudescence of onchocerciasis in the Comoé valley it was clear that control measures would have to be put in place to prevent the levels of infection increasing and possibly spreading to other areas. PNLO (with assistance from its partners − APOC and SightSavers) therefore instigated a programme of Community Directed Treatment with Ivermectin (CDTI) in the two affected health districts (Banfora and Mangodara) in Région des Cascades in accordance with strategy

Acknowledgements

We are very grateful to the African Programme for Onchocerciasis Control (WHO-APOC) who funded the work and repatriated the historical data from the old Onchocerciasis Control Programme (WHO-OCP) before it was dissolved at the end of 2015.

References (42)

R.A. Cheke et al.
Indices of onchocerciasis transmission by different members of the Simulium damnosum complex conflict with the paradigm of forest and savanna parasite strains
Acta Trop.
(2013)
J.-M. Hougard et al.
Twenty-two years of blackfly control in the Onchocerciasis Control Programme in West Africa
Parasitol. Today
(1997)
M.Y. Osei-Atweneboana et al.
Prevalence and intensity of Onchocerca volvulus infection and efficacy of ivermectin in endemic communities in Ghana: a two-phase epidemiological study
Lancet
(2007)
APOC, 2010. Conceptual and Operational Framework of Onchocerciasis Elimination with Ivermectin Treatment. World Health...
H. Agoua et al.
études entomologiques de post-traitement dans le programme de lutte contre l'onchocercose en Afrique de lÉOuest
Parasite
(1995)
Amazigo U.V., Crump A., (1998) Traitement à l’ivermectine sous directives communautaires (TIDC) OMS/APOC, Genève, 1998,...
K. Awadzi et al.
An investigation of persistent microfilaridermias despite multiple treatments with ivermectin, in two onchocerciasis-endemic foci in Ghana
Ann. Trop. Med. Parasitol.
(2004)
R.H.A. Baker et al.
Progress in controlling the reinvasion of windborne vectors into the western area of the Onchocerciasis Control Programme in West Africa
Phil.Trans. R. Soc. Lond. B
(1990)
C. Bellec et al.
état physiologique, identitÉ spÉcifique et chronologie de l’apparition des adultes du complexe Simulium damnosum participant d’une rÉinvasion dans une zone de programme de lutte contre l’onchocercose dans le bassin de la Volta
Cah. O.R.S.T.O.M. Sér. Ent. Méd. Parasitol.
(1984)
D.A. Boakye et al.
Cytotaxonomy and study of population movements in the Simulium damnosum complex in the OCP area

D.A. Boakye et al.

Sibling species distribution of the Simulium damnosum complex in the West African Onchocerciasis Control Programme area during the decade 1984-93, following intensive larviciding since 1974

Med. Vet. Entomol.

(1998)

B. Boatin et al.

Patterns of epidemiology and control of onchocerciasis in West Africa

J. Helminthol.

(1997)

G.J.J.M. Borsboom et al.

Impact of ivermectin on onchocerciasis transmission: assessing the empirical evidence that repeated ivermectin mass treatments may lead to elimination/eradication in West-Africa

Filaria J.

(2003)

Davies J.B., Crosskey R.W., 1991. Simulium −Vectors of Onchocerciasis. World Health Organisation document...

J.B. Davies et al.

Studies on biting Simulium damnosum s. l. at a breeding site in the Onchocerciasis Control Programme area during and after an interruption of insecticidal treatments

Tropenmed. Parasit.

(1981)

J.B. Davies et al.

The effects of helicopter applied adulticides for riverine tsetse control on Simulium populations in a West African savanna habitat. I. Introduction, methods and the effect on biting adults and aquatic stages of Simulium damnosum s. l

Trop. Pest Manage.

(1982)

L. Diawara et al.

Feasability of onchocerciasis elimination with ivermectin treatment in endemic foci in Africa: first evidence from studies in Mali and Sénegal

Plos Negl. Trop. Dis.

(2009)

P. Elsen et al.

Vitesse de repeuplement déun g’te de Cîte déIvoire par Simulium damnosum s. l. (Diptera, Simuliidae) aprôs léarrèt expêrimental des traitements larvicides: consêquence sur la stratêgie de la lutte contre ce vecteur de léonchocercose

Cah. O. R. S. T. O. M., Sêr. Ent. Mêd Parasitol.

(1981)

R. Garms et al.

Studies on the reinvasion of the Onchocerciasis Control Programme in the Volta river basin by Simulium damnosum s. l. with emphasis on the south-western areas

Tropenmed. Parasitol.

(1979)

Garms R., Cheke R.A., Sachs R., 1990. Discussion in Baker et al. (1990),...

J.-M. Hougard et al.

Criteria for the selection of larvicides by the Onchocerciasis Control Programme in West Africa

Ann. Trop. Med. Parasitol.

(1993)

Cited by (22)

Elimination of transmission of onchocerciasis (river blindness) with long-term ivermectin mass drug administration with or without vector control in sub-Saharan Africa: a systematic review and meta-analysis
2024, The Lancet Global Health
WHO has proposed elimination of transmission of onchocerciasis (river blindness) by 2030. More than 99% of cases of onchocerciasis are in sub-Saharan Africa. Vector control and mass drug administration of ivermectin have been the main interventions for many years, with varying success. We aimed to identify factors associated with elimination of onchocerciasis transmission in sub-Saharan Africa.
For this systematic review and meta-analysis we searched for published articles reporting epidemiological or entomological assessments of onchocerciasis transmission status in sub-Saharan Africa, with or without vector control. We searched MEDLINE, PubMed, Web of Science, Embase, Cochrane Central Register of Controlled Trials, African Index Medicus, and Google Scholar databases for all articles published from database inception to Aug 19, 2023, without language restrictions. The search terms used were “onchocerciasis” AND “ivermectin” AND “mass drug administration”. The three inclusion criteria were (1) focus or foci located in Africa, (2) reporting of elimination of transmission or at least 10 years of ivermectin mass drug administration in the focus or foci, and (3) inclusion of at least one of the following assessments: microfilarial prevalence, nodule prevalence, Ov16 antibody seroprevalence, and blackfly infectivity prevalence. Epidemiological modelling studies and reviews were excluded. Four reviewers (NM, AJ, AM, and TNK) extracted data in duplicate from the full-text articles using a data extraction tool developed in Excel with columns recording the data of interest to be extracted, and a column where important comments for each study could be highlighted. We did not request any individual-level data from authors. Foci were classified as achieving elimination of transmission, being close to elimination of transmission, or with ongoing transmission. We used mixed-effects meta-regression models to identify factors associated with transmission status. This study is registered in PROSPERO, CRD42022338986.
Of 1525 articles screened after the removal of duplicates, 75 provided 282 records from 238 distinct foci in 19 (70%) of the 27 onchocerciasis-endemic countries in sub-Saharan Africa. Elimination of transmission was reported in 24 (9%) records, being close to elimination of transmission in 86 (30%) records, and ongoing transmission in 172 (61%) records. I² was 83·3% (95% CI 79·7 to 86·3). Records reporting 10 or more years of continuous mass drug administration with 80% or more therapeutic coverage of the eligible population yielded significantly higher odds of achieving elimination of transmission (log-odds 8·5 [95% CI 3·5 to 13·5]) or elimination and being close to elimination of transmission (42·4 [18·7 to 66·1]) than those with no years achieving 80% coverage or more. Reporting 15–19 years of ivermectin mass drug administration (22·7 [17·2 to 28·2]) and biannual treatment (43·3 [27·2 to 59·3]) were positively associated with elimination and being close to elimination of transmission compared with less than 15 years and no biannual mass drug administration, respectively. Having had vector control without vector elimination (−42·8 [−59·1 to −26·5]) and baseline holoendemicity (−41·97 [−60·6 to −23·2]) were associated with increased risk of ongoing transmission compared with no vector control and hypoendemicity, respectively. Blackfly disappearance due to vector control or environmental change contributed to elimination of transmission.
Mass drug administration duration, frequency, and coverage; baseline endemicity; and vector elimination or disappearance are important determinants of elimination of onchocerciasis transmission in sub-Saharan Africa. Our findings underscore the importance of improving and sustaining high therapeutic coverage and increasing treatment frequency if countries are to achieve elimination of onchocerciasis transmission.
The Bill & Melinda Gates Foundation and Neglected Tropical Diseases Modelling Consortium, UK Medical Research Council, and Global Health EDCTP3 Joint Undertaking.
For the Swahili, French, Spanish and Portuguese translations of the abstract see Supplementary Materials section.
Situation of onchocerciasis transmission in 2020 in the Cascades region of Burkina Faso
2024, Parasitology International
Faced with the focal resurgence of onchocerciasis reported since 2004 in the South-West of Burkina Faso, the Neglected Tropical Diseases Control Program adopted a resumption of biannual community-directed treatment with ivermectin, since 2011 in the Cascades region and since 2013 in the South West region. The objective of this study was to assess the situation of onchocerciasis transmission in the Cascades region, nine years after the resumption of mass drug administration. This cross-sectional and descriptive survey concerned people over 5. The traditional method of skin snip on both iliac crests was performed for the parasitological diagnosis of onchocerciasis. The Ov-16 serological test was carried out in children aged 5 to 9 years.
In 22 surveyed villages, the overall prevalence of microfilariae was 0.11% and below the tolerable threshold of 5%. It was less than 5% in all the villages (n = 22), less than 1% in 21 villages (99%) and zero in 19 villages (86.36%). The community microfilarial loads varied from 0.01 to 0.05 mf/b. Out of 946 children tested for OV-16, only one 9-year-old was positive and whose skin snip examination was negative. All the positive cases came from endemical areas in Côte d'Ivoire. Population migration is a risk factor for introducing the parasite into Burkina Faso; it also is risk factor for the effective elimination of onchocerciasis which requires the joint development of a control strategy between neighboring countries.
Taking the strain out of onchocerciasis? A reanalysis of blindness and transmission data does not support the existence of a savannah blinding strain of onchocerciasis in West Africa
2021, Advances in Parasitology
Citation Excerpt :
Analyses of nuclear DNA, mitochondrial DNA and genes coding for antigenic proteins have suggested that populations of O. volvulus can have a mix of habitat-related markers and that they can and do interbreed (Choi et al., 2016; Keddie et al., 1999). This genetic mixing may be readily maintained by the migrations of both vectors (Baker et al., 1990; Cheke and Garms, 1983; Garms et al., 1979) and humans, including traditional transhumance and pastoralism from the Sahel to forests and back (Food and Agriculture Organization of the United Nations–Centre for International Cooperation in Agricultural Research for Development (FAO–CIRAD), 2012) and recent economic migration (Zachariah and Condé, 1981), with implications for recrudescence of onchocerciasis (Koala et al., 2017). Nevertheless, recent analyses based on mitochondrial DNA revealed that geographically distinct populations have genetic structure consistent with vector migration patterns (Crawford et al., 2019; Hedtke et al., 2020), knowledge of which could be useful for defining transmission zones (geographical areas where transmission of O. volvulus occurs by locally-breeding vectors and which can be regarded as a natural ecological and epidemiological unit for interventions).
Onchocerciasis (also known as ‘river blindness’), is a neglected tropical disease (NTD) caused by the (Simulium-transmitted) filarial nematode Onchocerca volvulus. The occurrence of ‘blinding’ (savannah) and non-blinding (forest) parasite strains and the existence of corresponding, locally adapted Onchocerca–Simulium complexes were postulated to explain greater blindness prevalence in savannah than in forest foci. As a result, the World Health Organization (WHO) Onchocerciasis Control Programme in West Africa (OCP) focused anti-vectorial and anti-parasitic interventions in savannah endemic areas. In this paper, village-level data on blindness prevalence, microfilarial prevalence, and transmission intensity (measured by the annual transmission potential, the number of infective, L3, larvae per person per year) were extracted from 16 West–Central Africa-based publications, and analysed according to habitat (forest, forest–savannah mosaic, savannah) to test the dichotomous strain hypothesis in relation to blindness. When adjusting for sample size, there were no statistically significant differences in blindness prevalence between the habitats (one-way ANOVA, P = 0.68, mean prevalence for forest = 1.76 ± 0.37 (SE); mosaic = 1.49 ± 0.38; savannah =1.89 ± 0.26). The well-known relationship between blindness prevalence and annual transmission potential for savannah habitats was confirmed and shown to hold for (but not to be statistically different from) forest foci (excluding data from southern Côte d’Ivoire, in which blindness prevalence was significantly lower than in other West African forest communities, but which had been the focus of studies leading to the strain–blindness hypothesis that was accepted by OCP planners). We conclude that the evidence for a savannah blinding onchocerciasis strain in simple contrast with a non-blinding forest strain is equivocal. A re-appraisal of the strain hypothesis to explain patterns of ocular disease is needed to improve understanding of onchocerciasis epidemiology and disease burden estimates in the light of the WHO 2030 goals for onchocerciasis.
Onchocerciasis prevalence, human migration and risks for onchocerciasis elimination in the Upper Mouhoun, Nakambé and Nazinon river basins in Burkina Faso
2018, Acta Tropica
Citation Excerpt :
CMFL values were in all communities much lower than the acceptability threshold of 0.5 mfs/s (Dadzie et al., 1991; APOC, 2010) and ranged from 0 to 0.06 mf/s. APOC (2010) also recommended that these levels should be maintained for several years after intervention is discontinued to ensure that infections did not recrudescence. There was a recrudescence event in the Comoé valley in Burkina Faso after cessation of vector control (Koala et al., 2017), but the levels of infection recorded in the three river basins in this study have remained very low (probably below the transmission threshold) and the only real question is whether this is a continuing low-level of autochthonous transmission or whether it is the result of immigration of parasites mediated by human migration from elsewhere. In theory, the recrudescence of infection in an area may be caused either by local increase in transmission of residual infections or by reintroduction of the parasite associated with migrations of infected persons or the immigration of vectors carrying the parasite.
Historically, the whole of Burkina Faso was considered to be endemic for onchocerciasis (except a small area in the far north of the country) with prevalence rates 60–80%, but all endemic areas were included in the World Health Organisation Onchocerciasis Control Programme, which operated a system of vector control by larviciding beginning in 1974. In Burkina Faso larviciding had been phased out by 1989 when it was considered that onchocerciasis had been reduced to levels below the transmission breakpoint (and any residual infections would disappear without further intervention). There was never any mass drug administration against onchocerciasis in Burkina Faso, except in the Bougouriba and Comoé river basins (from 1996 and 2011 to present respectively) because in each of these two areas there was a resurgence of infection, and in parts of the Nakambé River basin and Sissili River basin from 1992 to 1998. However, mass drug administration with ivermectin was also phased in across the whole country starting in 2000 using ivermectin against lymphatic filariasis and is currently being phased out (depending upon the epidemiological parameters). In this publication we report a new epidemiological survey for onchocerciasis which was carried out in 2014 in the Upper Mouhoun, Nakambé and Nazinon river basins in Burkina Faso to evaluate the prevalence and intensity of infection of onchocerciasis. A total of 11,195 people from 61 villages were examined across these three river basins, and onchocerciasis prevalence by skin-snip was below 5% in all villages, below 1% in 57 villages (93% of 61 villages) and zero in 47. In the 14 villages with positive skin snips, prevalence figures ranged from 0.31% to 3.50%. During the survey 31 infected individuals were found. All of them were Burkinabé, of whom 30 had a recent history of residence in Côte d’Ivoire (with a range of 0.5 to 73 microfilariae per skin-snip from two snips per person) and only one had no history of migration and presumably had an autochthonous infection (mean of 0.5 microfilariae per skin snip from two snips). According to parasitological indicators listed by the World Health Organization African Programme for Onchocerciasis Control in 2010, the situation for onchocerciasis was considered to be satisfactory in all three river basins and probably below the transmission threshold, in which case the disease should disappear naturally without the need for further intervention in the absence of continuing immigration. However, the results clearly indicate that infected persons coming from endemic zones of Côte d’Ivoire are settling in small communities which are otherwise nearly free from onchocerciasis in Burkina Faso. They are thus a source of continuing re-introduction of the parasite into the basins and could be a risk for the achievement of onchocerciasis elimination in all three basins. This would justify the continuation of periodic epidemiological surveys to monitor the possible recrudescence of the disease, and entomological (vector) surveys should be undertaken to assess and monitor the residual transmission.
The Current Status of Molecular Xenomonitoring for Lymphatic Filariasis and Onchocerciasis
2017, Trends in Parasitology
Citation Excerpt :
Ideally, transmission-interruption would signify the end of the need for surveillance, as new cases of infection should not develop under settings of interrupted parasite transmission. However, as has been recently reported by onchocerciasis elimination efforts in Burkina Faso, factors such as an incomplete understanding of transmission breakpoints (leading to premature termination of MDA), ecological change, human migration, and vector migration might all have the capacity to allow for recrudescence of infection in areas where the interruption of transmission was previously thought to have been achieved [71]. Imagining such concerns becomes particularly easy when regions demonstrating programmatic success share borders with countries still lacking well developed elimination programs.
The capacity of vector insect surveillance to provide estimates of pathogen prevalence and transmission potential has long been recognized within the global communities tasked with eliminating lymphatic filariasis (LF), the underlying cause of elephantiasis and hydrocele, and onchocerciasis (river blindness). Initially restricted to the practice of dissection, the potential of vector monitoring has grown due to the advent of molecular methods capable of increasing the sensitivity and throughput of testing. However, despite such advancement, operational research gaps remain. If insufficiently addressed, these gaps will reduce the utility of molecular xenomonitoring (MX) for onchocerciasis as elimination efforts expand into Africa. Similarly, such shortcomings will limit the programmatic usefulness of MX for LF, resulting in this technique’s significant underutilization.
Modelling the elimination of river blindness using long-term epidemiological and programmatic data from Mali and Senegal
2017, Epidemics
Citation Excerpt :
Hence, by this criterion, elimination cannot be verified in the River Gambia focus and it is probable that low-level transmission continues. Resurgence – based on parasitological (mf) and entomological data – has also been reported in Burkina Faso in a focus previously thought to have eliminated the infection (Koala et al., 2017). Notwithstanding the superior sensitivity of serological techniques, how seroprevalence profiles in children manifest in near-elimination settings and, more specifically, how the seroprevalence threshold (WHO, 2016) relates to transmission breakpoints and the likelihood of elimination, is a subject of ongoing research.
The onchocerciasis transmission models EPIONCHO and ONCHOSIM have been independently developed and used to explore the feasibility of eliminating onchocerciasis from Africa with mass (annual or biannual) distribution of ivermectin within the timeframes proposed by the World Health Organization (WHO) and endorsed by the 2012 London Declaration on Neglected Tropical Diseases (i.e. by 2020/2025). Based on the findings of our previous model comparison, we implemented technical refinements and tested the projections of EPIONCHO and ONCHOSIM against long-term epidemiological data from two West African transmission foci in Mali and Senegal where the observed prevalence of infection was brought to zero circa 2007–2009 after 15–17 years of mass ivermectin treatment. We simulated these interventions using programmatic information on the frequency and coverage of mass treatments and trained the model projections using longitudinal parasitological data from 27 communities, evaluating the projected outcome of elimination (local parasite extinction) or resurgence. We found that EPIONCHO and ONCHOSIM captured adequately the epidemiological trends during mass treatment but that resurgence, while never predicted by ONCHOSIM, was predicted by EPIONCHO in some communities with the highest (inferred) vector biting rates and associated pre-intervention endemicities. Resurgence can be extremely protracted such that low (microfilarial) prevalence between 1% and 5% can be maintained for 3–5 years before manifesting more prominently. We highlight that post-treatment and post-elimination surveillance protocols must be implemented for long enough and with high enough sensitivity to detect possible residual latent infections potentially indicative of resurgence. We also discuss uncertainty and differences between EPIONCHO and ONCHOSIM projections, the potential importance of vector control in high-transmission settings as a complementary intervention strategy, and the short remaining timeline for African countries to be ready to stop treatment safely and begin surveillance in order to meet the impending 2020/2025 elimination targets.

View all citing articles on Scopus

View full text

Original research articleRecrudescence of onchocerciasis in the Comoé valley in Southwest Burkina Faso

Highlights

Abstract

Graphical abstract

Section snippets

Historical introduction

Description the study area

Identifying the recrudescence

Instigation of community directed treatment with ivermectin in the Comoé valley

Acknowledgements

Acta Trop.

Parasitol. Today

Lancet

études entomologiques de post-traitement dans le programme de lutte contre l'onchocercose en Afrique de lÉOuest

Parasite

An investigation of persistent microfilaridermias despite multiple treatments with ivermectin, in two onchocerciasis-endemic foci in Ghana

Ann. Trop. Med. Parasitol.

Progress in controlling the reinvasion of windborne vectors into the western area of the Onchocerciasis Control Programme in West Africa

Phil.Trans. R. Soc. Lond. B

état physiologique, identitÉ spÉcifique et chronologie de l’apparition des adultes du complexe Simulium damnosum participant d’une rÉinvasion dans une zone de programme de lutte contre l’onchocercose dans le bassin de la Volta

Cah. O.R.S.T.O.M. Sér. Ent. Méd. Parasitol.

Cytotaxonomy and study of population movements in the Simulium damnosum complex in the OCP area

Sibling species distribution of the Simulium damnosum complex in the West African Onchocerciasis Control Programme area during the decade 1984-93, following intensive larviciding since 1974

Med. Vet. Entomol.

Patterns of epidemiology and control of onchocerciasis in West Africa

J. Helminthol.

Impact of ivermectin on onchocerciasis transmission: assessing the empirical evidence that repeated ivermectin mass treatments may lead to elimination/eradication in West-Africa

Filaria J.

Studies on biting Simulium damnosum s. l. at a breeding site in the Onchocerciasis Control Programme area during and after an interruption of insecticidal treatments

Tropenmed. Parasit.

The effects of helicopter applied adulticides for riverine tsetse control on Simulium populations in a West African savanna habitat. I. Introduction, methods and the effect on biting adults and aquatic stages of Simulium damnosum s. l

Trop. Pest Manage.

Feasability of onchocerciasis elimination with ivermectin treatment in endemic foci in Africa: first evidence from studies in Mali and Sénegal

Plos Negl. Trop. Dis.

Vitesse de repeuplement déun g’te de Cîte déIvoire par Simulium damnosum s. l. (Diptera, Simuliidae) aprôs léarrèt expêrimental des traitements larvicides: consêquence sur la stratêgie de la lutte contre ce vecteur de léonchocercose

Cah. O. R. S. T. O. M., Sêr. Ent. Mêd Parasitol.

Studies on the reinvasion of the Onchocerciasis Control Programme in the Volta river basin by Simulium damnosum s. l. with emphasis on the south-western areas

Tropenmed. Parasitol.

Criteria for the selection of larvicides by the Onchocerciasis Control Programme in West Africa

Ann. Trop. Med. Parasitol.

Original research article
Recrudescence of onchocerciasis in the Comoé valley in Southwest Burkina Faso