Studies on onchocerciasis in forest-savannah mosaic areas of Nigeria. I. Investigations in Gbaragu, Oji River

Onchocerciasis transmission status in some endemic communities of Cross River State, Nigeria after two decades of mass drug administration with ivermectin

Onchocerciasis is a parasitic disease transmitted by black flies. Human onchocerciasis is a public health and socioeconomic problem in Nigeria. Its prevalence and morbidity have reduced over the years because of control efforts especially, Mass Drug Administration with ivermectin. The current goal is to eliminate the disease transmission by 2030. Understanding the changes in transmission patterns in Cross River State is critical to elimination of onchocerciasis in Nigeria. This study was designed to determine the transmission dynamics of onchocerciasis in Cross River State after over two decades of mass ivermectin distribution in endemic communities. Agbokim, Aningeje, Ekong Anaku and Orimekpang are four endemic communities from three Local Government Areas of the State selected for this study. Transmission indices such as infectivity rates, biting rates and transmission potentials, parity rates and diurnal biting activities were determined. A total of 15,520 adult female flies were caught on human baits, Agbokim (2831), Aningeje (6209), Ekong Anaku (4364) and Orimekpang (2116). A total of 9488 and 5695 flies were collected during the rainy and dry seasons respectively in the four communities studied. The differences in relative abundance among the communities were statistically significant (P < 0.001). Monthly and seasonal fly numbers varied significantly (P < 0.008). There were differences in diurnal biting activities of flies in this study at different hours of the day and different months. The peak monthly biting rates were 5993 (Agbokim, October), 13,134 (Aningeje, October), 8680 (Ekong Anaku, October) and 6120 (Orimekpang, September) bites/person/month while the lowest monthly biting rates were 400 (Agbokim, November), 2862 (Aningeje, August), 1405 (Ekong Anaku, January) and 0.0 (Orimekpang, November and December) bites/person/month. Differences in biting rates among the study communities were significant (P < 0.001). The peak monthly transmission potential in Aningeje was 160 infective bites/person/month in the month of February while the lowest (except for months with no transmission) was 42 infective bites/person/month in the month of April. All other study sites had no ongoing transmission in this study. Transmission studies showed that there is progress toward transmission interruption especially in 3 out of the four studied areas. Molecular O-150 poolscreen studies is required to confirm the true transmission situation in the areas.

Impact of Eighteen-Year Varied Compliance to Onchocerciasis Treatment with Ivermectin in Sentinel Savannah Agrarian Communities in Kaduna State of Nigeria

Baseline and impact assessment data were generated in 1994 (n = 532) and 2011 (n = 593) from 6 sentinel villages with generalized onchocerciasis. Only volunteers and a cohort (n = 445, 75%) were screened at both visits. Each village had received 11 (64.7%) annual treatments and 92.6%, range 88.7-100%, treatment compliance. Overall mean number of treatment was 2.9 ± 1.6 with a range 2.0 ± 1.2-3.3 ± 0.6. Significant decreases in skin microfilaria prevalence from 201 (38%) to 0 (0%), palpable nodule from 77 (15%) to 4 (0.7%), dermal changes from 51 (9.6%) to 2 (0.04%), optic nerve disease from 24 (4.5%) to 4 (2.0%), and onchocercal inducible ocular lesions from 31 (5.8%) to 12 (2.0%) were recorded, P < 0.05, (t-test of unpaired data). Cases of glaucoma, 8 (1.4%), and blindness, 6 (1.05%), remained unchanged. Visual acuity ≥6/24 in one or both eyes, 198 (33.45%); cataract, 169 (28.5%); pterygium 157 (26.5%); and acute senilis, 165 (27.9%), were significantly increased and positively correlated with increase in age (R (2) = 0.898 - 0.949). Dissected parous Simulium damnosum caught (n = 222) were without infective third stage larva. Active onchocerciasis transmission seems halted despite varied compliance to long-term ivermectin treatment. We recommend continued surveillance and targeted treatment of controlled and hypoendemic areas.

A guide to the Simulium damnosum complex (Diptera: Simuliidae) in Nigeria, with a cytotaxonomic key for the identification of the sibling species

Although approximately 40% of all the people blinded by Onchocerca volvulus are Nigerians, almost nothing was known about the various cytospecies of the blackfly vectors present in Nigeria until 1981. The activation of the Nigerian National Onchocerciasis Control Programme in 1986 (and that programme's initiation of mass distributions of ivermectin in 1991) provided a significant stimulus to understand the biology of the Nigerian vectors but the exploration of any possible differences between the cytospecies has been hampered by a lack of accessible taxonomic information. This review attempts to satisfy that need. There are nine different cytoforms reliably recorded from Nigeria (Simulium damnosum s.s. Nile form, S. damnosum s.s. Volta form, S. sirbanum Sirba form, S. sirbanum Sudanense form, S. soubrense Beffa form, S. squamosum A, S. squamosum B, S. squamosum C and S. yahense typical form), and three more are known from surrounding countries and might be reasonably expected to occur in Nigeria. All of these cytospecies are presumed to be vectors, although there have been almost no identifications of the vectors of O. volvulus in Nigeria. The biogeographical distribution of the cytoforms is broadly similar to that known in other parts of West Africa (although many of the cytoforms remain insufficiently studied). The physico-chemical hydrology of the Nigerian breeding sites of the cytospecies does not, however, correspond to that seen elsewhere in West Africa, and it is not clear whether this might be related to differences in the cytoforms. An illustrated cytotaxonomic key is presented to facilitate and encourage future studies.

Parasitological and clinico-epidemiological features of onchocerciasis in West Wellega, Ethiopia

Onchocerciasis is a disease of public health and socio-economic importance in Ethiopia. The aim of this study was to assess parasitological and clinico-epidemiological features of onchocerciasis in the Anfilo District, West Wellega, prior to implementation of Community Directed Treatment with Ivermectin (CDTI) to generate epidemiological and parasitological data for use in control program of the disease and subsequent evaluation of CDTI. A cross-sectional study was conducted in Anfilo District of West Wellega zone during a period of 1 month: from mid-August to mid-September 2006. Data on socio-demographic characteristics were collected using a standardized questionnaire prepared for this purpose. All persons were examined clinically for skin signs and symptoms of onchocerciasis. Two skin snips, one from each side of the gluteal fold were taken using blood lancet and sterilized razor blade and examined for microfilaria. All data were categorized, coded, entered in a data base and analyzed using SPSS version 15.0. for windows. A total of 1114 individuals ≥15 years were examined for microfilariae (mf) of Onchocerca volvulus and onchocercal skin disease (OSD). The prevalence of onchocercal (mf) carrier was 74.8% (833/1114). In both genders, the prevalence of onchocerciasis showed direct correlations with the age of individuals (R (2) = 0.79, P < 0.05). The infection rate varied with the occupation of the study subjects, with preponderance among farmers. Among the subjects with onchocerciasis, the mf density ranged from 1.0 to 711.0 per mg of skin snip with a mean density (SD) and median values of 32.1 (61.5) and 10.4 respectively. The overall community microfilariae load (CMFL), the most sensitive parasitological indicator of onchocerciasis was 19.6. The pervasiveness of OSD among the study subjects was 26.4%. OSD was more frequent in males (32.4%) than their female counterparts (20.8%, P < 0.05). The overall prevalence of onchocercal nodule carrier, the symptom opted for determining the community-wide prevalence of onchocerciasis was 12.1%. Leopard skin, the proxy of longstanding infection of onchocerciasis in the community, was also relatively high (19.1%). The abundance of mf in skin would definitely lead to high transmission potential in the Anfilo District. The situation in the Anfilo District should call for continued CDTI, owing to success of similar recommendations for such programmes in other parts of the country and elsewhere.

Primary motives for demand of ivermectin drug in mass distribution programmes to control onchocerciasis

BACKGROUND

Onchocerciasis is a disease with a spectrum of manifestations suffered by different infected people. Based on individual perceptions and manifestations presented, demand for the drug Ivermectin was due to different motives and priorities during mass distribution programmes.

SUBJECTS AND METHOD

This study presents findings from a sample of 594 persons out of a total of 35,763 treated individuals who voluntarily demanded Ivermectin treatment during a community-based Ivermectin distribution exercise. The distribution, which took place in 2008, was mass distribution of the microfilaricide to control onchocerciasis in endemic communities of Ezinihitte in the Imo River Basin of Nigeria. The subjects who were selected by quota sampling procedure on the basis of community and gender, were asked to rank-order six plausible reasons for seeking treatment in terms of their order of importance in motivating them to demand Ivermectin.

RESULTS

"To gain treatment and prevention of Skin Problems" and "Desire to be De-wormed" ranked first and second respectively. "To gain promotion of general wellbeing" and "To improve state of vision and prevent blindness" ranked third and fourth respectively. In the fifth and sixth rank-order positions were "To prevent hanging groin" and "to prevent/relieve enlargement of the scrotum or clitoris" in that order. A test of hypothesis to determine if there was significant agreement among treated persons on the rank order of importance of their reasons for demanding Ivermectin gave a Kendall's Coefficient of Concordance of W = 0.62, p <.001.

CONCLUSION

The findings are interpreted within the framework of the major postulations of the health belief model with consideration to perceptions of severity of the conditions and belief that submitting to treatment will abate the perceived risk of the conditions. The role of endemicity of specific manifestations of onchocerciasis in lay assessment of risk of this disease is also discussed.

Community-directed treatment with ivermectin in two Nigerian communities: an analysis of first year start-up processes, costs and consequences

OBJECTIVES

To determine the start-up processes, costs and consequences of community-directed treatment with ivermectin (CDTI) in two onchocerciasis endemic rural towns of Southeast Nigeria; namely Achi and Nike. The other objectives were to discover the community-financing mechanisms, local ivermectin distribution strategies and communities' organisational capacity to handle the programme.

METHODS

Structured questionnaires, informal interviews, observations, discussions with community members at general village assemblies and community outreach lectures were used at different stages of the study.

RESULT

The towns had the organisational capacity to implement the programme. Coverage with ivermectin was between 31-73% in Achi (mean = 58.6%), and 36.6-72% in Nike (mean = 61.95%). The unit financial costs were $0.17 in Nike and $0.13 in Achi, but the unit aggregate cost was $0.37 in Nike and $0.39 in Achi. When research costs were removed, the unit aggregate cost was $0.22 in Achi and $0.20 in Nike. Provider's financial costs and communities' non-financial costs were the biggest contributors to the aggregate cost. The cost would decrease in subsequent years since the research cost and parts of the mobilisation and training costs would not be incurred after the first year.

CONCLUSION

Governments and sponsors of CDTI should find means of continuously strengthening the programme and providing technical support to the communities. As both CDTI and communities are dynamic entities, continuous health education campaigns are needed to keep reminding the people of the benefit of long-term ivermectin distribution, together with the need for community ownership of the programme.

Factors affecting adverse event reporting during mass ivermectin treatment for onchocerciasis

This study examines the effect of age, sex, dosing round, time of day, and distance from the nurse monitor on adverse event reporting during mass ivermectin administration at Achi, south-east Nigeria. There was a significant increase in adverse event reporting with age but no significant difference between the sexes. Both compliance and the incidence of reported adverse events were less during the second dosing round than during the first. Only three (2%) out of 144 subjects interviewed gave adverse events as a reason for non-compliance. Significantly fewer adverse events were reported as starting at night (22:00-06:00 h) than by day. The effect of distance on adverse event reporting was not statistically significant for distances up to 1 km.

Can community leaders' preferences be used to proxy those of the community as a whole?

BACKGROUND

Community-based distribution of ivermectin and other drugs requires people in the endemic communities who are capable of distributing the drug. It is essential also to collect information on local people's views concerning different financing mechanisms and approaches to distributing ivermectin. However, studies at household level are resource-intensive. Eliciting the preferences of the community by interviewing a smaller number of community leaders offers an alternative strategy.

METHODS

A comparison of information from community leaders and household heads on the financing and distribution of ivermectin through communities was conducted in three communities in Nigeria to determine whether rapidly collected information from key community leaders could represent broad community preferences.

RESULTS

The preferences of community leaders and household heads were comparable in relation to the method of collecting payments, managing payments and making payments, who should set the level of payments and the drug distribution mechanisms. However, there were differences between community leaders' views and those of heads of households concerning how the scheme should be supervised.

CONCLUSIONS

This study has shown that community leaders' views can only be used as a partial substitute for more laborious methods of data collection insofar as they have the attraction of being quicker and less costly to use. However, they should not be assumed to be identical with the views of the community as a whole.

Willingness to pay for community-based ivermectin distribution: a study of three onchocerciasis-endemic communities in Nigeria

OBJECTIVE

To determine the willingness to pay (WTP) for local ivermectin distribution in a community financing framework.

METHOD

Contingent valuation in three communities in Nigeria, using randomly selected household heads. WTP was elicited using a bidding game, and for collecting information on the households' socio-economic status, level of knowledge, priority ranking and perception of risk of contracting the disease, structured questionnaires were used. Ordinary least squares (OLS) multiple regression analysis was used to analyse factors associated with WTP.

RESULTS

Between 92.1% and 93.3 % of respondents were willing to pay amounts ranging from 5 Naira (US$ 0.06) to 100 Naira (US$ 1.25) (median: 20 Naira, US$ 0.25) in the three communities, more than three times the modelled unit direct cost of distributing ivermectin by the communities themselves. Occupation of the respondent, marital status, average monthly expenditure on health care, manifestations of onchocerciasis, the type of savings scheme embarked on by the respondent, age-group, level of education and type of property were statistically significant (P < 0.05) variables affecting WTP.

CONCLUSION

This study shows that there is WTP for local ivermectin distribution in the three study communities, and that it should be assessed before instituting community-directed treatment with ivermectin.

Ivermectin levels in human breastmilk

Ivermectin levels were measured in breastmilk and plasma of 4 healthy mothers after an oral 150 micrograms/kg dose. Mean +/- S.D. plasma and milk values were 37.9 +/- 0.54 and 14.13 +/- 0.43 (ng/ml) respectively. Steady-state ivermectin levels in milk were low. Our results suggest that exclusion of lactating mothers from mass chemotherapy with ivermectin may be unnecessary.

Human onchocerciasis in the lower Jos Plateau, central Nigeria: the prevalence, geographical distribution and epidemiology in Akwanga and Lafia local government areas

An investigation of human infection with Onchocerca volvulus and the resulting clinical disease was carried out for the Nigerian National Onchocerciasis Control Programme between July and August 1989 [corrected]. The survey covered 10.6% of the rural population in 41 savanna villages of central Nigeria. Of the 8451 self-selected individuals examined, 900 (10.6%) had skin microfilariae (Mf). There were differences between villages in both endemicity and intensity of infection, but in general the number of both Mf carriers and cases of clinical onchocerciasis increased with age. The disease in the Mf carriers showed as blindness (0.8%), onchocercal nodules (0.6%), leopard skin (1.6%) and pruritus (2.8%). Of 35 persons with lymphatic complications, 19 had hanging groin, 10 had elephantiasis and six had hydrocoele. Onchocerciasis was mesoendemic in the rocky northern escarpments, and became hypoendemic and sporadic in the southern uplands of sedimentary geological origin.