Visual loss in an onchocerciasis endemic community in Sierra Leone

How does onchocerciasis-related skin and eye disease in Africa depend on cumulative exposure to infection and mass treatment?

BACKGROUND

Onchocerciasis (river-blindness) in Africa is targeted for elimination through mass drug administration (MDA) with ivermectin. Onchocerciasis may cause various types of skin and eye disease. Predicting the impact of MDA on onchocercal morbidity is useful for future policy development. Here, we introduce a new disease module within the established ONCHOSIM model to predict trends over time in prevalence of onchocercal morbidity.

METHODS

We developed novel generic model concepts for development of symptoms due to cumulative exposure to dead microfilariae, accommodating both reversible (acute) and irreversible (chronic) symptoms. The model was calibrated to reproduce pre-control age patterns and associations between prevalences of infection, eye disease, and various types of skin disease as observed in a large set of population-based studies. We then used the new disease module to predict the impact of MDA on morbidity prevalence over a 30-year time frame for various scenarios.

RESULTS

ONCHOSIM reproduced observed age-patterns in disease and community-level associations between infection and disease reasonably well. For highly endemic settings with 30 years of annual MDA at 60% coverage, the model predicted a 70% to 89% reduction in prevalence of chronic morbidity. This relative decline was similar with higher MDA coverage and only somewhat higher for settings with lower pre-control endemicity. The decline in prevalence was lowest for mild depigmentation and visual impairment. The prevalence of acute clinical manifestations (severe itch, reactive skin disease) declined by 95% to 100% after 30 years of annual MDA, regardless of pre-control endemicity.

CONCLUSION

We present generic model concepts for predicting trends in acute and chronic symptoms due to history of exposure to parasitic worm infections, and apply this to onchocerciasis. Our predictions suggest that onchocercal morbidity, in particular chronic manifestations, will remain a public health concern in many epidemiological settings in Africa, even after 30 years of MDA.

Study of onchocerciasis-related visual impairment in North Kivu province of the Democratic Republic of Congo in Africa

Purpose:

The Objective of this study is to determine baseline data regarding onchocercal eye lesions and associated visual loss in the Nord Kivu province, an onchocerciasis hyperendemic tropical rain forest area in the Democratic Republic of Congo (DRC).

Methods:

A cross-sectional study was conducted in the Nord Kivu province of the DRC during which 2150 subjects were examined ophthalmologically. The eye examination included visual acuity (VA), slit-lamp examination, ophthalmoscopy, intraocular pressure, and visual field assessment by the confrontation test. Patients with suspicion of glaucoma were further evaluated by Humphreys automated perimeter.

Results:

39 (1.81%) out of 2150 subjects had onchocerciasis-related eye lesions and 4 (0.19%) were blind (VA <3/60). Chorioretinitis (0.88%) was the most frequent onchocerciasis lesion followed by keratitis (0.46%), microfilaria in the anterior chamber (0.28%), iridocyclitis (0.28%), secondary glaucoma (0.19%), complicated cataract (0.19%), and optic atrophy (0.19%). Visual impairment was discovered in 114 (5.3%) out of 2150 subjects, of whom 39 (0.19%) had blindness and 75 (3.4%) had low vision. Visual impairment was mostly caused by nononchocerciasis-related diseases like cataract (27.2%), retinal diseases (19.3%), glaucoma (15.8%), and iridocyclitis (15.8%) rather than because of onchocerciasis (9.6%) among all causes of visual impairment.

Conclusion:

Features of ocular onchocerciasis usually described in forest and savanna areas were relatively less common than expected in and around Goma, the capital of the Nord Kivu province of the DRC.

Economic evaluations of onchocerciasis interventions: a systematic review and research needs

OBJECTIVE

To provide a systematic review of economic evaluations that has been conducted for onchocerciasis interventions, to summarise current key knowledge and to identify research gaps.

METHOD

A systematic review of the literature was conducted on the 8th of August 2018 using the PubMed (MEDLINE) and ISI Web of Science electronic databases. No date or language stipulations were applied to the searches.

RESULTS

We identified 14 primary studies reporting the results of economic evaluations of onchocerciasis interventions, seven of which were cost-effectiveness analyses. The studies identified used a variety of different approaches to estimate the costs of the investigated interventions/programmes. Originally, the studies only quantified the benefits associated with preventing blindness. Gradually, methods improved and also captured onchocerciasis-associated skin disease. Studies found that eliminating onchocerciasis would generate billions in economic benefits. The majority of the cost-effectiveness analyses evaluated annual mass drug administration (MDA). The estimated cost per disability-adjusted life year (DALY) averted of annual MDA varies between US$3 and US$30 (cost year variable).

CONCLUSIONS

The cost benefit and cost effectiveness of onchocerciasis interventions have consistently been found to be very favourable. This finding provides strong evidential support for the ongoing efforts to eliminate onchocerciasis from endemic areas. Although these results are very promising, there are several important research gaps that need to be addressed as we move towards the 2020 milestones and beyond.

Doxycycline plus ivermectin versus ivermectin alone for treatment of patients with onchocerciasis

BACKGROUND

Onchocerciasis, also known as "river blindness," is a parasitic disease that is caused by infection from the filarial nematode (roundworm), Onchocerca volvulus. Nematodes are transmitted from person to person by blackflies of the Simulium genus, which usually breed in fast flowing streams and rivers. The disease is the second leading infectious cause of blindness in endemic areas.Ivermectin (a microfilaricide) is widely distributed to endemic populations for prevention and treatment of onchocerciasis. Doxycycline, an antibiotic, targets Wolbachia organisms that are crucial to the survival of adult onchocerca (macrofilaricide). Combined treatment with both drugs is believed to cause direct microfilarial death by ivermectin and indirect macrofilarial death by doxycycline. Long-term reduction in the numbers of microfilaria in the skin and eyes and in the numbers of adult worms in the body has the potential to reduce the transmission and occurrence of onchocercal eye disease.

OBJECTIVES

The primary aim of this review was to assess the effectiveness of doxycycline plus ivermectin versus ivermectin alone for prevention and treatment of onchocerciasis. The secondary aim was to assess the effectiveness of doxycycline plus ivermectin versus ivermectin alone for prevention and treatment of onchocercal ocular lesions in communities co-endemic for onchocerciasis and Loa loa (loiasis) infection.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision Trials Register) (Issue 7, 2015), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to July 2015), EMBASE (January 1980 to July 2015), PubMed (1948 to July 2015), Latin American and Caribbean Health Sciences Literature Database (LILACS) (1982 to July 2015), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com) (last searched 1 July 2014), ClinicalTrials.gov (www.clinicaltrials.gov) and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic search for trials. We last searched the electronic databases on 15 July 2015.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) that had compared doxycycline plus ivermectin versus ivermectin alone. Participants with or without one or more characteristic signs of ocular onchocerciasis resided in communities where onchocerciasis was endemic.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial eligibility and extracted data. We used standard methodological procedures as expected by Cochrane.

MAIN RESULTS

We identified three RCTs including a total of 466 participants with a diagnosis of onchocerciasis. All trials compared doxycycline plus ivermectin versus ivermectin alone. One study investigated improvement in visual impairment at six-month follow-up; the other two studies measured microfilarial loads in skin snips to assess sustained effects of treatment at follow-up of 21 months or longer. The studies were conducted at various centers across three countries (Cameroon, Ghana, and Liberia). We judged all studies to be at overall high risk of bias because of inadequate randomization and lack of masking (one study), missing data (two studies), and selective outcome reporting (three studies).Only one study measured visual outcomes. This study reported uncertainty about the difference in the proportion of participants with improvement in visual impairment at six-month follow-up for doxycycline plus ivermectin compared with ivermectin alone (risk ratio (RR) 1.06, 95% confidence interval (95% CI) 0.80 to 1.39; 240 participants; very low-quality evidence). No participant in either group showed improvement in optic atrophy, chorioretinitis, or sclerosing keratitis at six-month follow-up. More participants in the doxycycline plus ivermectin group than in the ivermectin alone group showed improvement in iridocyclitis (RR 1.24, 95% CI 0.69 to 2.22) and punctate keratitis (RR 1.43, 95% CI 1.02 to 2.00) at six-month follow-up; however, we graded these results as very low quality.Two studies reported that a six-week course of doxycycline may result in Wolbachia depletion and macrofilaricidal and sterilizing activities in female Onchocerca worms; however, no analysis was possible because data were missing and incomplete (graded evidence as very low quality). Adverse events were reported in 16 of 135 (12%) participants in one of these studies and included itching, headaches, body pains, and vertigo; no difference between treatment groups was reported for any adverse event. The second study reported that one (1.3%) participant in the doxycycline plus ivermectin group had bloody diarrhea after treatment was initiated.

AUTHORS' CONCLUSIONS

Available evidence on the effectiveness of doxycycline plus ivermectin compared with ivermectin alone in preventing and treating onchocerciasis is unclear. Limited evidence of very low quality from two studies indicates that a six-week course of doxycycline followed by ivermectin may result in more frequent macrofilaricidal and microfilaricidal activity and sterilization of female adult Onchocerca compared with ivermectin alone; however, effects on vision-related outcomes are uncertain. Future studies should consider the effectiveness of treatments in preventing visual acuity and visual field loss and their effects on anterior and posterior segment lesions, particularly chorioretinitis. These studies should report outcomes in a uniform and consistent manner at follow-up of three years or longer to allow detection of meaningful changes in vision-related outcomes.

Neglected tropical disease control in post-war Sierra Leone using the Onchocerciasis Control Programme as a platform

Strategic investments in the control of neglected tropical diseases (NTD) spearheaded by the US Government, the British Government and other bilateral donors such as foundations and key pharmaceutical partners have enabled the treatment of millions of people for the five targeted debilitating diseases (lymphatic filariasis, onchocerciasis, schistosomiasis, soil-transmitted helminthiasis and trachoma), paving the way for the potential elimination as public health problems of some of these diseases. Like many other countries, Sierra Leone has a high burden of these major NTDs. Despite the fragile infrastructure of a health system emerging from a devastating 10-year civil war, the country has successfully implemented the National NTD Control Programme, reaching national coverage in 2010. The NTD Control Programme uses the existing Onchocerciasis Control Programme as a platform and involves primary health workers. The programme has provided extensive training opportunities to health workers at national, district and community levels. The country currently has 31 161 trained community volunteers treating a population of five million people. It is shown that the investments in NTD control are not only to control NTDs but also to strengthen health systems, particularly at the primary level, through extensive capacity building of frontline health workers and community-directed distributors.

Impact of three rounds of mass drug administration on lymphatic filariasis in areas previously treated for onchocerciasis in Sierra Leone

Background

1974–2005 studies across Sierra Leone showed onchocerciasis endemicity in 12 of 14 health districts (HDs) and baseline studies 2005–2008 showed lymphatic filariasis (LF) endemicity in all 14 HDs. Three integrated annual mass drug administration (MDA) were conducted in the 12 co-endemic districts 2008–2010 with good geographic, programme and drug coverage. Midterm assessment was conducted 2011 to determine impact of these MDAs on LF in these districts.

Methodology/Principal Findings

The mf prevalence and intensity in the 12 districts were determined using the thick blood film method and results compared with baseline data from 2007–2008. Overall mf prevalence fell from 2.6% (95% CI: 2.3%–3.0%) to 0.3% (95% CI: 0.19%–0.47%), a decrease of 88.5% (p = 0.000); prevalence was 0.0% (100.0% decrease) in four districts: Bo, Moyamba, Kenema and Kono (p = 0.001, 0.025, 0.085 and 0.000 respectively); and seven districts had reductions in mf prevalence of between 70.0% and 95.0% (p = 0.000, 0.060, 0.001, 0.014, 0.000, 0.000 and 0.002 for Bombali, Bonthe, Kailahun, Kambia, Koinadugu, Port Loko and Tonkolili districts respectively). Pujehun had baseline mf prevalence of 0.0%, which was maintained. Only Bombali still had an mf prevalence ≥1.0% (1.58%, 95% CI: 0.80%–3.09%)), and this is the district that had the highest baseline mf prevalence: 6.9% (95% CI: 5.3%–8.8%). Overall arithmetic mean mf density after three MDAs was 17.59 mf/ml (95% CI: 15.64 mf/ml–19.55 mf/ml) among mf positive individuals (65.4% decrease from baseline of 50.9 mf/ml (95% CI: 40.25 mf/ml–61.62 mf/ml; p = 0.001) and 0.05 mf/ml (95% CI: 0.03 mf/ml–0.08 mf/ml) for the entire population examined (96.2% decrease from baseline of 1.32 mf/ml (95% CI: 1.00 mf/ml–1.65 mf/ml; p = 0.000)).

Conclusions/Significance

The results show that mf prevalence decreased to <1.0% in all but one of the 12 districts after three MDAs. Overall mf density reduced by 65.0% among mf-positive individuals, and 95.8% for the entire population.

Onchocerciasis studies across Sierra Leone between 1974 and 2005 showed that 12 of the 14 health districts (HDs) are endemic for onchocerciasis. Baseline lymphatic filariasis (LF) studies 2005–2008 showed that all 14 HDs of Sierra Leone are LF endemic. Three annual rounds of integrated mass drug administration (MDA) with ivermectin and albendazole 2008–2010 were conducted in the 12 HDs that are co-endemic for onchocerciasis and LF with good geographic, epidemiological drug (or programme) and drug coverage. A midterm evaluation study of mf prevalence and density was conducted in the 12 HDs in 2011. The hypothesis proposed for this study is that areas previously exposed to ivermectin treatment for onchocerciasis control may require less rounds of annual MDA to eliminate LF (i.e. reduce microfilaremia (mf) prevalence to <1%). Results of the midterm evaluation study showed very significant and rapid reduction of mf prevalence and density with 11 out of the 12 districts having mf prevalence <1%. Relatively low LF baseline prevalence and effective integrated MDA for onchocerciasis and LF have led to rapid reduction in LF prevalence.

Blindness and visual impairment in an urban West African population: the Tema Eye Survey

OBJECTIVE

To determine the prevalence, causes, and risk factors of blindness and visual impairment among persons aged 40 years or older residing in an urban West African location.

DESIGN

Population-based, cross-sectional study.

PARTICIPANTS

A total of 5603 participants residing in Tema, Ghana.

METHODS

Proportionate random cluster sampling was used to select participants aged 40 years or older living in the city of Tema. Presenting distance visual acuity (VA) was measured at 4 and 1 m using a reduced logarithm of the minimum angle of resolution tumbling E chart and then with trial frame based on autorefraction. A screening examination was performed in the field on all participants. Complete clinical examination by an ophthalmologist was performed on participants with best-corrected visual acuity (BCVA) <20/40 or failure of any screening test.

MAIN OUTCOME MEASURES

Age- and gender-specific prevalence, causes, and risk factors for blindness (VA of <20/400 in the better eye, World Health Organization definition) and visual impairment (VA of <20/40 in the better eye).

RESULTS

A total of 6806 eligible participants were identified, of whom 5603 (82.3%) participated in the study. The mean age (± standard deviation) of participants was 52.7 ± 1 0.9 years. The prevalence of visual impairment and blindness was 17.1% and 1.2%, respectively. After refraction and spectacle correction, the prevalence of visual impairment and blindness decreased to 6.7% and 0.75%, respectively, suggesting that refractive error is the major correctable cause of visual impairment and blindness in this population. Of 65 subjects with a VA <20/400, 22 (34%) were correctable with refraction, 21 to the level of visual impairment and 1 to normal. The remaining 43 patients (66%) had underlying pathology (cataract in 19, glaucoma in 9, nonglaucomatous optic neuropathy in 3, corneal opacities in 3, retinal disease in 3, and undetermined in 5) that prevented refractive correction. Increased age was a significant risk factor for blindness and visual impairment.

CONCLUSIONS

There is a high prevalence of blindness and visual impairment among those aged ≥ 40 years in Tema, Ghana, West Africa. Refractive error is a major cause of blindness and visual impairment in this population, followed by cataract, glaucoma, and corneal disease.

Prevalence of blindness in people over 40 years in the volta region of ghana

SummaryIn 2001, we conducted a population-based cluster survey of the prevalence of blindness and glaucoma in three districts of the Volta region of Ghana, West Africa. A secondary purpose was to assess the presenting visual acuities of individuals who had undergone extracapsular cataract extraction with an intraocular lens implant (ECCE/IOL) and intracapsular cataract extraction (ICCE). The target population consisted of 2400 adults, aged 40 years and older, of whom, 2298 (95.7%) were examined. The prevalence of moderate to severe bilateral blindness was found to be 4.4 %. The main causes of blindness were cataract and glaucoma (53.9% and 20.6%, respectively). Eighty-one percent of the blind had preventable or treatable causes. Nine percent of the population >/=40 years needed cataract surgery in one or both eyes for vision </=6/18. The corrected prevalence of glaucoma in one or both eyes was 7.5%. There were 51 individuals who had undergone cataract surgery, all of whom had been operated in Ghana. Those who had ECCE/IOL surgery had a presenting visual acuity of 20/60 or better in 65% of eyes while those who had ICCE surgery achieved this level in only 30% of eyes [p=0.02].

Incidence of visual loss in rural southwest Uganda

BACKGROUND

Surveys have been conducted to measure prevalence of eye disease in Africa, but not of incidence, which is needed to forecast trends. The incidence of visual loss is reported in southwest Uganda.

METHODS

A rural population residing in 15 neighbouring villages was followed between 1994-5 (R1) and 1997-8 (R2). Survey staff screened adult residents (13 years or older) for visual acuity using laminated Snellen's E optotype cards at each survey. Those who failed (VA >6/18) were evaluated by an ophthalmic clinical officer and an ophthalmologist. Incidence of visual loss (per 1000 person years (PY)) was calculated among those who had normal vision at R1.

RESULTS

2124 people were studied at both survey rounds (60.9% of those screened at R1); 48% were male. Participants in R1 were older (34.7 versus 31.5 years at R2, p<0.001). Visual loss in R2 occurred in 56 (2.8%) of 1997, yielding a crude incidence rate of 9.9, and an age standardised incidence rate of 13.2, per 1000 PY. Incidence of visual loss increased with age from 1.21 per 1000 PY among people aged 13-34 to 64.2 per 1000 PY in those aged 65 years or older (p for trend >0.001). The six commonest causes of visual loss were: cataract, refractive error, macular degeneration, chorioretinitis, glaucoma, and corneal opacity. If similar rates are assumed for the whole of Uganda, it is estimated that 30 348 people would develop bilateral blindness or bilateral visual impairment, per year.

CONCLUSIONS

Cataract and refractive error were the major causes of incident visual loss in south west Uganda. These data are valuable for forecasting and planning eye services.

Profile of eye lesions and vision loss: a cross-sectional study in Lusambo, a forest-savanna area hyperendemic for onchocerciasis in the Democratic Republic of Congo

OBJECTIVE

To determine baseline data regarding eye lesions and vision loss in five villages of Lusambo, an onchocerciasis-hyperendemic forest-savanna area in the Democratic Republic of Congo (DRC), in preparation of mass ivermectin distribution.

METHODS

Five villages were selected by simple randomization. Through a cross-sectional design, 750 subjects were examined ophthalmologically. The eye examination included acuity visual measurement, slit-lamp examination, ophthalmoscopy, intraocular pressure measurement, and visual field assessment by the Wu-Jones test.

RESULTS

There was a high prevalence of onchocerciasis-related eye lesions compared with non-onchocercal lesions. Chorioretinitis (20%) was the most frequent disease, others were punctate keratitis and microfilariae in the anterior chamber in equal frequency (13.8%), white intraretinal deposits (10.4%) and iridocyclitis (8%). Vision loss was discovered in 8.5% of the subjects, of whom 0.5% had bilateral blindness, 2.2% had monocular blindness and 5.7% had visual impairment. Vision loss was mostly caused by onchocerciasis-related diseases, especially those affecting the anterior segment of the eye.

CONCLUSION

Features of ocular onchocerciasis usually described in forest and savanna areas were both found in this forest-savanna zone of the DRC.

The effect of 5 years of annual treatment with ivermectin (Mectizan) on the prevalence and morbidity of onchocerciasis in the village of Gami in the Central African Republic

To assess the impact of 5 years of annual community treatment with ivermectin (Mectizan) on the prevalence of onchocerciasis and onchocerciasis-associated morbidity, data collected, before and after such treatment, in the village of Gami, in a hyper-endemic area of the Central African Republic, were analysed. Skin snips from all the villagers treated in 1990 and/or 1995 were used to assess the prevalence and intensity of infection with Onchocerca volvulus. Ocular and dermatological morbidity was assessed by ophthalmological and clinical examinations of the same subjects. Following the five annual treatments, there was a reduction in the prevalence of infection and a dramatic decrease in the microfilarial load of the community. The prevalences of pruritus, onchocercal nodules and impaired vision were all significantly reduced. The results emphasise the long-term benefits of the mass-treatment programmes, particularly for children aged <10 years.

Intraocular pressure and gonioscopic findings in rural communities mesoendemic and nonendemic for onchoceriasis, Kaduna State, Nigeria

PURPOSE

To report on glaucoma-related ocular parameters, namely intraocular pressure and peripheral anterior synechiae, in the presence of onchocercal infection.

METHODS

Two computer-generated random samples of individuals were drawn from communities mesoendemic and nonendemic for onchocerciasis respectively. Applanation tonometry and gonioscopy were carried out on these individuals.

RESULTS

Four hundred and thirty-six and 319 individuals from the mesoendemic and nonendemic communities were examined respectively. The mean intraocular pressure was 1.58 mmHg lower in the individuals from the mesoendemic communities compared with those from the nonendemic communities (p < 0.001) despite the prevalence of peripheral anterior synechiae being higher in the mesoendemic communities. In these communities, there was strong evidence that the prevalence of peripheral anterior synechiae increased with increasing microfilarial load.

CONCLUSIONS

Onchocercal infection produces a low-grade inflammatory process, which may result in a lowering of intraocular pressure despite the formation of peripheral anterior synechiae. Glaucomatous optic nerve damage may therefore not be the primary cause of visual loss in ocular onchocerciasis as this occurs late and is probably preceded by other blinding onchocercal pathology.

Blindness from uveitis in a hospital population in Sierra Leone

A retrospective study was conducted to assess the causes of blindness and visual impairment in patients who visited an eye hospital in Sierra Leone, West Africa, in 1989 and 1992. These data were compared with figures from 1981. Throughout the years, senile cataract was the major cause of blindness, followed by uveitis (including onchocerciasis). Uveitis remained the second most important cause of blindness in this population, despite the significant decrease in blindness from onchocerciasis (from 30% in 1981 to 15% in 1992). An increasing number of patients with uveitis from non-onchocercal origin was observed: almost 10% of the blindness found in 1992 was due to uveitis of non-onchocercal origin. A reduction in visual handicap in patients with non-onchocercal uveitis could be achieved if local hospitals could obtain more accurate diagnoses in these patients.