Prevalence of onchocerciasis, attitudes and practices and the treatment coverage after 15 years of mass drug administration with ivermectin in the Tombel Health District, Cameroon

Introduction Onchocerciasis is an infection caused by Onchocerca volvulus. It affects 37 million people of which 99% are in Africa. This study assessed the prevalence of onchocerciasis after 15 years of mass drug administration with ivermectin. Methods This was a population based cross sectional study. Questionnaires covering participants' identity and attitudes and practices of community respondents towards ivermectin were administered. The treatment coverage was obtained by review of records of mass drug administration from 1999 to 2015. The epidemiological evaluation of infection status was done by parasitological examination of skin snips and nodule palpation in individuals in five health areas of the district. Results A total of 400 participants were randomly selected. Of these, 56.0% were males, 62.0% single, 59.5% farmers and 98.0% Christians. Participants with good attitudes towards community directed treatment with ivermectin made up 80.5% while 47.8% of the participants had good practice. The highest treatment coverage achieved was 88.0% in 2010 while lowest was 57.0% in 2002. Less than 2% had microfilaria and 6.0% had nodules. There was no statistically significant difference in the prevalence of microfilaria with respect to age. There was a statistically significant difference in the distribution of nodules (χ2=73.6, p=0.001) among the different age groups. The greatest rate of infection (2.1%) was among farmers. Conclusion This study showed that the prevalence reduced compared to other prevalence studies in Cameroon. The study area was hypo-endemic for onchocerciasis.


Introduction
Onchocerciasis is an infection caused by the nematode Onchocerca volvulus. Humans acquire onchocerciasis through the bite of an infected female black fly in the genus Simulium. Since the fly larvae develop in fast-flowing water, onchocerciasis is mostly common along rivers and is also referred to as river blindness. The disease affects rural communities and is a major cause of blindness and skin disease in endemic areas with serious socioeconomic consequences [1]. It affects about half a million people in sub-Saharan Africa.
Onchocerciasis also causes skin disease with acute and chronic dermatitis, lichenification, atrophy, depigmentation and severe itching. It is estimated to affect over 37 million people worldwide.
Onchocerciasis has not caused a single death but the global burden is 987,000 disability adjusted life years (DALYs). The disease has been found to significantly reduce the lifespan of infected people [2]. In 1995, the WHO launched the African Programme for Onchocerciasis Control (APOC) that was intended to eliminate onchocerciasis from the African continent through Community Directed Treatment with Ivermectin (CDTI) in the next 12years [3]. However, following the 2006 and 2007 progress report, the APOC was extended to 2015.
The CDTI strategy has been very successful in ensuring sustained high treatment coverage and by the year 2010 some 75 million people at risk were treated annually with ivermectin in the APOC countries [4].
Rapid Epidemiological Mapping for Onchocerciasis (REMO), has shown that the disease is endemic in Cameroon [5]. The issue of serious adverse events or side effects (SAEs) due to ivermectin in areas coendemic for loiasis has been known for some time. The only current control measure is CDTI. In this perspective, the purpose of this study was to assess the prevalence of onchocerciasis in Tombel Health District (THD) where CDTI has been carried out for 15 consecutive years, in order to evaluate the impact of ivermectin treatment. To assess the impact of mass drug administration with ivermectin over 15 years, the prevalence in this study was compared to the prevalence in other areas of Cameroon such as the Fundong health district [6] and the West region of Cameroon [7].

Methods
Study design: the study was a population based cross sectional study designed to assess the prevalence of onchocerciasis after fifteen years of mass drug administration (MDA) with ivermectin and to determine the attitudes and practices towards ivermectin and the treatment coverage with ivermectin. This involved collection of both qualitative and quantitative data from five randomly selected health areas namely: Ebonji, Nyasoso, Baseng, Ndibenjock and Tombel.
Qualitative data collection involved administration of pre-tested Study participants: a total number of 400 participants were randomly selected from the five health areas.
Sample size determination: sample size was determined based on the Taro Yamane's approach [9].
where, n=the expected sample size, N=finite population out of which the sample size is drawn, e=level of precision. The target population for this study was 52575 [10]. n=35683/1+52575(0.05)2; n=396 participants.

Selection criteria
Inclusion criteria: those from 20 years and above who signed the consent form and those below 20 years whose guardian signed the consent form and assent obtained from these children were included in the study. A qualified subject must have lived in the area for at least five years prior to the study.

Socio-demographic characteristics of the study participants:
a total of 400 participants aged 5-92 years were recruited for the study. The majority were in the age range 21 to 40 with mean age of 37.65±19.056 years ( Table 1). Most of the participants were males and majority were single. Farmers represented a higher percentage.
A greater proportion of participants were Christians.

Attitude and practice of community respondents about CDTI
in the THD: among the respondents, 329 (82.3%) perceived CDTI as very useful programme (  (Table 3). To facilitate the late memory to the reaction of the drug, the respondents were asked when they did receive the last treatment and 340 (85%) of the respondents responded last year (Table 3).
Attitude and practice on the CDTI programme: participants with good attitude and good practice recorded 80.5% and 47.8% ( Figure 1) respectively while participants with poor attitude and poor practice recorded 19.5% and 52.2% respectively (Figure 1).

Coverage of mass drug administration with ivermectin in
Tombel health district: the highest treatment coverage was

Proportion of participants with microfilaridermia and
nodules: the overall prevalence of microfilaredermia and nodules was 1.5% and 6.0% respectively.  [5] and the West region of Cameroon [6]. Elimination is considered attained when the microfilaria prevalence in skin snips is less than 5% in sampled communities.

Discussion
This study showed that the study area was hypo-endemic for onchocerciasis, following fifteen years of continuous treatment with ivermectin. The prevalence of onchocerciasis was higher among males than female subjects. The differences in infection rate with regards to sex could be due to endemicity [12], occupational exposure and susceptibility of individual [13]. Males work longer in the farm, and with bare body, than the females thereby making them more prone to the bite of the black flies. The findings in this study differ from another report [14]  This observation is consistent with studies conducted in a hyper-endemic community in Imo State [19] and Edo State [20] in Nigeria and in Ethiopia [21]. However, a few individuals interrupted the treatment due to fear of drug related adverse reactions which is similar to the findings of studies conducted in Sequa area, Southwest Ethiopia [21] and the hyper-endemic community of Edo State, Nigeria [20]. Generally, majority of the study participants had good attitudes about the CDTI programme (80.5%). This finding differs from the findings of the study conducted in the Quara district Northwest Ethiopia [22]. Greater percentage of the participants had poor practices compared to good practices. This finding is consistent with the findings of the study conducted in the Quara district, Northwest Ethiopia. The poor practices were probably due to the lack of health education at the community level and the CDDs might not have been properly trained on the CDTI programme due to negligence of health extension workers to supervise the CDDs in delivering health education.

Conclusion
This study showed that, the prevalence of nodules and microfilaridermia reduced from >40% and >5% to 6.0% and 1.5% respectively following 15 years of continuous treatment with ivermectin. The treatment coverage in the health areas was at an average of 74.1% with combined range of 73.2%-78.3%.

What is known about this topic
• Impact of the CDTI programme towards eradication of the onchocerciasis; • The efficacy of the drug as well as the attitude and practice of community participants towards the drug; • Prevalence studies on onchocerciasis in areas like the West and Southwest regions of Cameroon.

What this study adds
• Shows a high treatment coverage (74.1%) with ivermectin in the Tombel Health District.
• Shows high rate of poor practice (52.2%) towards ivermectin despite the endemicity of onchorcerciasis; • Demonstrates a need for training of CDDs on the CDTI programme and health education at the community level.
Special thanks go to the people of Tombel for their cooperation and assistance during data collection and chief of bureau health, chiefs of centre and laboratory technicians in the Tombel Health District (THD) for their dedication, commitment and support.