|Year : 2017 | Volume
| Issue : 1 | Page : 14-19
Impact assessment study after 27 years of community-directed treatment with ivermectin in Galadimawa, Kaduna State, Nigeria
Olufemi E Babalola1, Amos Bassi2
1 Department of Surgery, College of Health Sciences, Bingham University, Jos; Rachel Eye Center, Garki, Abuja, Nigeria
2 Department of Community Medicine, College of Health Sciences, Bingham University, Jos, Nigeria
|Date of Web Publication||9-May-2017|
Olufemi E Babalola
Rachel Eye Center 23, Onitsha crescent Garki II Abuja, PO Box 4108, Garki Abuja
Source of Support: None, Conflict of Interest: None
Purpose: To assess the impact on blindness after 27 years of community-directed treatment with ivermectin (CDTI) in the Galadimawa community of Kauru Local Government in Kaduna state, Nigeria. The population of Galadimawa constituted about 12% of the total population examined during the ivermectin randomised control trial (RCT) in 1989. The RCT population of 8000 individuals was scattered over 36 villages in Kaduna state. Thus, longitudinal data are available on blindness. Materials and Methods: After 27 years of dosing with ivermectin, the people in the community of Galadimawa were re-examined for the prevalence and causes of blindness. This was achieved by an examination of the visually disabled. The findings were compared with the situation in 1989 before the dosing commenced. Results: The population of the village increased from 711 to 1419. The prevalence of blindness dropped from 4.9 to 0.96%. The most common causes of blindness were now cataract (55.2%) and optic atrophy (27.6%), whereas the most common causes in 1989 were onchocerciasis (28.3%), glaucoma (17.4%) and cataract (10.9%). People with optic atrophy were more likely to have taken fewer doses of ivermectin over the years. The blind people encountered in 2016 were on average 17 years older than those seen in 1989, which suggests that blindness, when it occurs, is delayed by almost two decades. Conclusion: CDTI has reduced the prevalence of blindness significantly in Galadimawa and may reflect the situation elsewhere in the Kaduna state, which is an oncho-endemic zone.
Keywords: Community-directed treatment with ivermectin, impact assessment, nigeria
|How to cite this article:|
Babalola OE, Bassi A. Impact assessment study after 27 years of community-directed treatment with ivermectin in Galadimawa, Kaduna State, Nigeria. Niger Postgrad Med J 2017;24:14-9
|How to cite this URL:|
Babalola OE, Bassi A. Impact assessment study after 27 years of community-directed treatment with ivermectin in Galadimawa, Kaduna State, Nigeria. Niger Postgrad Med J [serial online] 2017 [cited 2020 May 30];24:14-9. Available from: http://www.npmj.org/text.asp?2017/24/1/14/205978
| Introduction|| |
Community-directed treatment with ivermectin (CDTI) is the main onchocerciasis control platform adopted by the African Program for Onchocerciasis Control (APOC) and has been in existence in Galadimawa, a village within the Kauru Local Government (LG) of Kaduna state in the North Western zone of Nigeria, for the past 27 years. There are two main foci of meso-endemic onchocerciasis in Kaduna state, whose capital is Kaduna city. The first is the Kauru/Lere focus, which is to the east of Kaduna city, consisting of villages within Kauru and Lere LGs [Figure 1]. Galadimawa village is one of the villages within this focus. The second is the Birnin-Gwari focus, which is to the west of Kaduna state.
|Figure 1: A map showing the Galadimawa village within Kauru Local Government within the Kaduna state of Nigeria|
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The Galadimawa community [Figure 1] is one of the onchocerciasis endemic communities assessed between 1989 and 1990 before the commencement of CDTI in 1989 for ocular and parasitological variables as part of the randomised control trial for ivermectin. Longitudinal data are available on the prevalence and causes of blindness in that focus. The community of Galadimawa was the largest of the 36 communities assessed. Its population in 1989 was 716, constituting 12% of the total population examined in that study; however, currently, its population is estimated (on the basis of a population growth rate of 2.5% according to the National Population Commission) to have increased to about 1419.
Statement of the problem
Currently, there is parasitological evidence that CDTI has reduced, if not eliminated, onchocerciasis as a disease of public concern in the Kauru/Lere focus of Kaduna state. Tekle et al. demonstrated that the community microfilaria (mf) load in Galadimawa between 1987 and 2008 had dropped from 2.87 to 0 microfilaria per skin snip (mf/ss) and the prevalence of skin mf had dropped from 46.8 to 0%. The CDTI coverage in Kauru LG was around 76.2 (74.4–80.3)%. However, there is no evidence to date as to whether CDTI had any effect on the prevalence and causes of blindness in Kaduna.
Rationale for the study
This study is important, because it is necessary to document the effect of CDTI on ocular diseases after 27 years of treatment. To our knowledge, it is only our group that has pre-CDTI data on ocular disease status in the APOC zone. We can, therefore, make longitudinal comparisons on the populations in question.
Aim of the study
The aim of the study is to assess the impact of CDTI in the Galadimawa community. The objectives are the following:
- To assess the prevalence and causes of blindness in Galadimawa and make longitudinal comparisons with the pre-CDTI situation in 1989.
- To assess the impact on the general health and socio-economic status of the community after 27 years of dosing with ivermectin.
This study will, however, focus on the prevalence and causes of blindness using the examination of the visually disabled (EVD) method.
| Materials and Methods|| |
The research was conducted between January and March 2016. The ethical clearance for the study was obtained from the Institutional Review Board of the Bingham University Teaching Hospitals Ethics Committee. Approval number BUTH/ERC/342/2016 was obtained on 30th December 2015. The study commenced on January 2016, and its completion date was March 2015. Informed consent was obtained from the Kaduna State Government, Kauru LG, the chieftaincy council of the Galadimawa community and from individuals examined during the exercise. The study followed the tenets of the Declaration of Helsinki. An EVD was conducted at a central location in the village after word had been sent out for several weeks before our visit. In 1989, EVD had been conducted before the whole community assessment (WCA), so data on both methods were available. In addition, the two methods have been compared in the Discussion section. Measures were taken to ensure that all those who presented were continuous residents in the village. For practical logistic reasons, the visually disabled could not be examined at home; however, the village leaders did determine that these visually disabled were indeed residents. All those who perceived themselves as visually disabled and who presented themselves for the examination were assessed. However, their true visual status was determined only after the examination; consequently, those with visual acuity (VA) <3/60 were excluded from the final analysis. The team consisted of an ophthalmologist Olufemi Emmanuel Babalola (OEB), a community physician Amos Bassi (AB), an ophthalmic nurse and two medical technicians.
History was obtained from the attendees with special emphasis on the duration of blindness, the perceived cause of blindness and exposure to dosing with ivermectin. Visual acuity was assessed by the ophthalmic nurse using a Snellen tumbling E chart in available outdoor light at 6 m. The participants were then examined with a pen torch, direct ophthalmoscope and a binocular indirect ophthalmoscope where indicated. The primary, secondary and tertiary causes of blindness or visual disability were determined.
Means were compared using Student’s t-test. Chi-squared test was performed to compare the proportions. Bivariate analysis and computation of confidence interval (CI) at 95% were performed where appropriate. A P value of <0.05 was accepted as significant.
The findings were recorded in a pre-tested pro forma and subsequently entered into an Excel worksheet. Analysis was performed using the Stata statistical analysis version 10 software.
| Results|| |
The findings obtained in 1989 and 2016 were compared [Table 1]. In 2016, 19 individuals presented for EVD. Of these, 14 were blind in both the eyes, and one was blind in only one eye (VA less than 3/60 in the better eye with the best correction). The total number of blind eyes was 29. In 1989, on the contrary, 32 people were found to be blind using the EVD method in the same community (both EVD and WCA methods were used in 1989). Meanwhile, the population of the village had increased from 711 to 1419 (on the basis of a growth rate of 2.5% per annum). The estimated prevalence of blindness based on EVD, therefore, dropped from 4.9 to 0.96%. The mean age of the blind also increased from 54.2 years (CI 49.7–58.7) in 1989 to 71.4 years (CI 64.0–78.8) in 2016 (P = 0.00038 by Student’s t-test). Thus, blindness occurred on average 17.2 years later than previously reported in the past.
|Table 1: Examination of the visually disabled (EVD non-case tracing) in Galadimawa in 1988 and 2016 following 25 years of community-directed treatment with ivermectin (CDTI)|
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Causes of blindness
[Table 2] compares the 29 blind eyes encountered in Galadimawa in 2016 with the 46 blind eyes encountered in 1989. This information was further compared with the 637 blind eyes in the combined Kaduna oncho focus (Kauru/Lere and Birnin Gwari, as well as 36 villages in six LGs). These latter two sets of figures were obtained by the WCA [Table 2].
|Table 2: Causes of blindness (eyes) in Galadimawa in 2016, 1988 and in the entire Kaduna oncho-endemic zone in 1988|
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In 2016, in Galadimawa, 16 eyes were blind from cataracts (55.2%), eight from optic atrophy (27%) and two from couching. Only two eyes were blind from posterior onchocerciasis (6.9%), and none were noted to be blind from anterior onchocerciasis.
On the contrary, if we examined the figures in 1989 in Galadimawa village and in the same year for the Kaduna oncho-endemic zone, onchocerciasis was the most common cause of blindness (Galadimawa 23.5 and Kaduna oncho zone 27%). Posterior onchocerciasis was more common than anterior onchocerciasis in the Kaduna oncho zone (the prevalence of posterior onchocerciasis was 23.5, whereas the prevalence of anterior onchocerciasis was 3.5%). Furthermore, in 1989, the prevalence of cataracts in Galadimawa was 10.9% and a smaller 6.5% in the Kaduna oncho zone compared with 55.2% in the recent survey in Galadimawa. On the other hand, in 1989, optic atrophy caused 4.3% of the blindness in Galadimawa village in particular and 9.4% in the entire Kaduna Oncho zone.
The prevalence of cataract and optic atrophy in 2016 in Galadimawa was, therefore, significantly higher, whereas the prevalence of onchocerciasis was significantly lower. It must be noted, however, that in a previous study we estimated that about 50% of the optic atrophy in the area under discussion was attributable to onchocerciasis (see Discussion). One concomitant case of glaucoma was identified in 2016, but it was decided that cataract was the primary cause of blindness.
Dosing with ivermectin
All the participants who presented for EVD had received ivermectin in the past, but the number of yearly doses received varied widely. The number of annual doses received ranged from 1 to 25. The median number of annual doses was 10 (95% CI 6.7–20), whereas the modal number was 20 (frequency 4) [Table 3].
|Table 3: History of annual dosing with ivermectin among the 19 patients who presented for EVD|
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The patients with optic atrophy took on average only half as many doses of ivermectin as those blind from other causes (number of doses taken = 6.27; CI 1.4–11 doses for the optic atrophy group vs. 12.3; CI 8.7–16 for the non-optic atrophy group). The likelihood that the patients with optic atrophy would take <10 annual doses of the possible 27 was 11 times higher than the other non-optic atrophy blind patients (CI 0.93–130.33, P = 0.057).
| Discussion|| |
Abiose predicted in 1998 that the sustained distribution of ivermectin ‘should lead to a reduction in the prevalence of blindness’ in the onchocerciasis endemic areas of West Africa and the APOC region in general. The findings suggested that the overall prevalence of blindness has dropped significantly between 1989 and 2016 following 27 years of CDTI.
This is the first evidence of an impact on blindness in the West African oncho-endemic zone in general and in the Kaduna focus in particular, a region where onchocerciasis is known to be a major cause of blindness.,
There is already entomological evidence that CDTI has virtually eliminated skin-borne mf in the Kauru/Lere focus. However, literature on the impact of CDTI on blindness is surprisingly scarce. CDTI impact studies conducted in Ethiopia did not appear to directly address the problem of blindness, although the authors stated that blindness was not a major issue in Ethiopian onchocerciasis. There was some evidence presented in a study, which reported that blindness was no longer a major cause of concern in the Mexican onchocercal focus, with the prevalence of onchocercal blindness having dropped to 0.01% from a pre-CDTI level of 0.1%.
The findings in this study align with the findings of zero mf load in the Kauru LG Area, which is the setting for this study. The prevalence of skin mf had come down from 46.8 to 0% and mf load from 2.87 mf/ss in 1987 to zero in 2008.
It is worthy of note that a similar reduction in the prevalence of blindness was observed after the Onchocerciasis Control Program (OCP) in West Africa, a programme which predated the APOC initiative and which was based only on larviciding of the breeding sites of the blackfly Simulium damnosum between the years 1975 and 2002. It should be recalled that Liberia and Nigeria were not included in the OCP. The OCP intervention caused a significant reduction in the incidence of blindness from about 5% in the hyper-endemic areas of the Upper Volta to 1% for all causes of blindness, while incident blindness from onchocerciasis appeared to no longer be a problem.,
Our findings also suggest that the mean age of the blind in Galadimawa in 2016 (71.4 years) was significantly higher than the mean age in 1989 (51.2 years) (P = 0.00038). This suggests that people were becoming blind almost two decades later than before CDTI commenced, and thus the overall number of ‘blind years’ has been reduced significantly. This is a sign that CDTI has an overall salutary effect on blindness burden in this environment.
In addition, cataract is now a proportionately more important cause of blindness, causing 55% of the blindness compared with 6.5% in 1989. This is likely due to the fact that onchocerciasis now causes proportionately less blindness than in the past. However, even if we removed onchocerciasis and optic atrophy from the equation in 1989, cataracts would have been accountable for only 11.6% of the blindness. The recent figure of 55% is closer to the national average. There are the following two possibilities for such an outcome: we underestimated the prevalence of cataracts then which is unlikely, or some factor such as increased longevity and/or the changes in the population structure accounted for an increase in the prevalence of cataracts, which would appear to be the more likely explanation, given the fact that people became blind at a much later age than before.
Onchocerciasis as a cause of blindness
In 2016, in Galadimawa, there was no case of anterior onchocerciasis seen among the blind and visually handicapped, and only one individual (two eyes) with posterior onchocercal chorioretinitis was encountered. This contrasts with the finding in 1989 in which onchocerciasis, especially the posterior variety, was responsible for about one-third of the cases of blindness. This finding is clear evidence that CDTI has drastically reduced the threat of blindness from onchocerciasis in this focus.
Examination of the visually disabled versus whole community assessment
We may be accused of comparing apples and oranges in our assessment of blindness because we have juxtaposed findings from EVD with WCA with regards to the prevalence and cause of blindness. We had addressed this issue in a previous publication, in which our analysis suggested that prevalence and cause data from EVD were not too dissimilar to the findings from WCA, at least in this population. Nonetheless, in Galadimawa village specifically, the EVD appeared to have overestimated the prevalence of blindness relative to WCA (4.5% vs. 3.1%) during the 1989 exercise. Both methods had been used concurrently in 1989. However, even if we took the figure 3.1%, the current blindness prevalence estimate of 0.96% is still significantly lower.
Currently, there appears to be a disproportionate number of optic atrophy cases in Galadimawa, with optic atrophy being responsible for 27.6% of all blind eyes compared with 9.4% in the generic Kaduna oncho zone in 1989, a significant difference at P < 0.05. Specifically, in Galadimawa in 1989, only 4.3% of the population were blind from optic atrophy, a significant difference at P < 0.005 between 2016 and 1989. Optic atrophy is a part of the spectrum of posterior onchocercal diseases. However, as in our previous publications, we have refrained from attributing all cases of optic atrophy without concomitant onchocercal chorioretinitis to onchocerciasis. Nevertheless, as in our analysis that was conducted and published earlier, 50% of optic atrophy in the Kaduna oncho-endemic zone was attributable to onchocerciasis.
If posterior onchocerciasis is removed from the equation in 1989, optic atrophy per se would account for 17% of blindness, which is still lower that the current figure of 28%. This brings up the rather discomfiting possibility that ivermectin has caused an increased incidence of optic neuritis and atrophy over these many years. In an earlier publication, we found that ivermectin protected against the development of optic neuritis and consecutive optic atrophy when the mf load was higher than a certain threshold (10 mf/mg ss). However, as already noted, participants with optic atrophy were much less compliant with annual ivermectin than other persons blind from other causes in the same community. This fact would reinforce the notion that ivermectin is protective against optic atrophy. Nonetheless, the possibility is also that some of the cases of optic atrophy were a legacy from previous cases prior to the onset of dosing with ivermectin, because the concerned patients were relatively older.
Health priorities in the village
From the focus group discussion held in the village, it was clear that the health priorities of the villagers have changed between 1989 and 2016 following the CDTI intervention. Currently, blindness and ocular and dermatological problems are only ‘somewhat significant’ and rated behind malaria, hypertension and diabetes.
However, this is a relatively small sample, Galadimawa being only about 12% of the whole Kaduna oncho zone. The results should be interpreted with caution, and there is a need for an expanded study.
| Conclusion|| |
CDTI appears to have resulted in a dramatic lowering of the prevalence of blindness in the eastern onchocerciasis focus of Kaduna state, Nigeria, as exemplified by our findings in Galadimawa village. Cataracts are now the most common cause of blindness, as is the case in the other non-onchocerciasis endemic areas of Nigeria. The health priorities of the village have shifted accordingly, and authorities must be prepared to shift their own focus to meet the new challenges. Other health interventions, such as polio eradication, have been modelled on the CDTI intervention.
Limitations of the Study
The CI tends to be wide on some parameters because of the limitations on the size of the sample. A WCA, including the examination of those sighted as well, will give a more holistic picture of the eye health situation. More settlements need to be assessed to give more power to the study. Efforts are underway to obtain grants for the expanded study.
Financial support and sponsorship
This study was sponsored by Rachel Eye Center.
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3]