ABSTRACT

A study on the assessment of Onchocercavolvulus infection in humans and blackflies and the onchocerciasis response to ivermectin therapy among some villagers around Gurara dam was conducted between June to November 2015. A total of 158 skin snips were collected and 4994 black flies were caught. The skin snips and female black flies were analysed by means of microscopy to detect Onchocerca volvulus. From the skin snips analysed, 4(2.6%) were positive for Onchocerca volvulus infection, The highest number of flies caught (1274) and highest number of parous flies (1089) were recorded in June. The highest number of infected flies, 14(38%) was obtained in the month of July. The amplified Polymerase Chain Reaction (PCR) detected O. volvulus DNA from skin snip of some individuals. The drug of choice, Ivermectin, administered in the study population was observed to be effective in humans, with 75% complete resolution of symptoms such as dermatitis and reduction in nodules. The highest incidence of Onchocerca volvulus was found among the age group of 50 years and above (75%). The prevalence was higher among the farmers (75%) with equal distribution among females (50%) and males (50%), followed by artisans (25%). The risk factor implicated was regular visit to the dam. The signs and symptoms of onchocerciasis observed in this study were; white patches, severe body itch, nodules and hanging groins. This study revealed that infective blackflies are still hovering around Gurara dam and vicinity, thus the persistence of onchocerciasis among the inhabitants, especially farmers, of the sampled villages. Hence the call for an effective vector control and a well supervised and prolonged ivermectin distribution is necessary.

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CHAPTER ONE

1.0       INTRODUCTION

1.1       Background

Onchocerciasis or “river blindness” is a parasitic disease caused by the filarial

nematodeOnchocerca volvulus and transmitted by repeated bites of infected blackflies of

the Simulium species(WHO, 2013).

The adult filarial worms are usually found in subcutaneous nodules and have an average

longevity of around 9-11 years Tthe adult female worm produces millions of

microfilariae who migrate to the skin of the host (Marroquin, 1981).

The microfilariae are the main cause of the clinical manifestations of the disease

(Shibuya, 2006). Onchocerciasis is characterized by chronic skin disease, severe itching,

and eye lesions that can progress to complete blindness (CDC, 2013). It is endemic in

Nigeria (Evans etal., 2011). Onchocerciasis is the second leading cause of blindness

(after trachoma) in the world (Dent and Kazura, 2011).

The disease was highly endemic in many parts of the world before the commencement

of control activities, affecting millions of people in Africa, South and Central America,

and Yemen (Babalola, 2011). Approximately 123 million persons are at risk of

contracting onchocerciasis in 38 endemic countries with at least 25.7 million infected,

and about 1 million reported blinded or exhibiting severe visual impairment. Nigeria

accounts for one-third of these estimates (CDC, 2013).

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Onchocerciasis is basically a rural disease affecting communities sited along fast-

flowing rivers with symptoms particularly irritating and disabling, often associated with

long-term exposure to infection and this affects the social and economic activities of the

inhabitants concerned (Okonkwo et al., 2010).

Both the savannah type that is associated with severe eye disorders and blindness and

the forest type which causes more skin damage are present and responsible for the

divergent clinic-epidemiologic picture. One of the major reasons northern Nigeria is

reported to have higher blindness rates than the southern part is owing to the widespread

distribution of savannah species of O. volvulus. In the south, the forest species that cause

mostly skin diseases abound (Okonkwo etal., 1991).

In Nigeria, most of the activities of the individuals in affected communities include

farming, fishing, handicraft and trading. Rural dwellers flee from this plague and

migrate to urban cities disrupting the socioeconomic development in their communities

(Alonso et al., 2009).

According to Ubachukwu (2006), one of the social consequences associated with

onchocerciaisis is the disruption of family life and relationships as disabled persons

desert rural villages to urban cities for better quality of life. However in the city, they are

unable to access and secure employment, and thus experience extreme poverty and

become beggars on the streets, they end up settling in shanty towns and resort to living

in slums.

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In addition, the burden of the disease impacts women and children, it affects the age of

marriage in young women, limiting their choice of partners such as older men and

divorcees. It also prevents infected mothers from practicing exclusive breastfeeding,

reducing bonding between new born and mother. The educational impact of the disease

is especially on children as they drop out from school to care for and lead blind family

members (Ubachukwu, 2006).

The vector (black fl