Onchocerciasis in Imo state, Nigeria (2): the prevalence, intensity and distribution in the upper Imo river basin

Abstract

Human infection with Onchocerca volvulus was investigated in 13 rural communities in the Upper Imo River basin, Imo State, Nigeria between March 1997 and December 2000 using the skin snip method. Of the 3,311 persons examined, 889 (26.8%) had microfilariae. There were significant differences between communities in microfilariae prevalence and intensity of infection (P<0.05). Sex infection was similar in males (26.8%) and females (26.9%); whereas farmers (46.6%) and fishermen (28.4%) were more affected than people in other occupations. The proportion of infected persons increased with age coinciding with the period when most clinical signs manifest. A significant proportion of the 889 persons with positive microfilariae skin biopsy had musculoskeletal pain (57.1%). Thirty-four (47.2%) of the 72 epileptics identified had positive skin biopsy in addition to other manifestations. The present findings show that onchocerciasis is a public health problem in the area. The use of ivermectin has reduced the incidence of the disease when compared with data from the pre-ivermectin era. This shows that Community Directed Treatment with Ivermectin (CDTI) campaign is successful and should be sustained until onchocerciasis is eliminated as a public health problem in the area.

Prevalence of Onchocerciasis and Efficacy of Ivermectin: a brief study from Idogun, Nigeria.

“…This suggests that individuals that are engaged in activities such as farming and hunting especially around the river are likely to be exposed to the blackfly bites and consequently have higher infection rate and worm loads (intensity) as observed in Idogun community. This was in agreement with the finding of Ikechukwu et al [15] , who reported prevalence of 46.6% among the farmers in Imo State. The total prevalence of infection in Idogun (28.1%) community suggests that the community is hypo-endemic (16-39%).…”

“…This finding was in accordance with the findings of other groups [10,[12][13][14]. But contrary to the report of Ikechukwu et al [15] who reported that the sex prevalence in upper river basin in Imo State was not different between the gender. Similarly, farming, fishing and hunting were identified as major socio-economic activities that highly predisposed the respondents to the infection.…”

Onchocerca volvulus and epilepsy: A comprehensive review using the Bradford Hill criteria for causation

“…In the Central African Republic, a study conducted in 1996 reported a positive and significant correlation (r = 0.73; P < 0.001) between onchocerciasis endemicity levels determined by community microfilarial levels (hypoendemic, mesoendemic, and hyperendemic) and epilepsy prevalence (respectively, 0.5%, 0.8%, and 2.5%), and a negative and significant correlation (r = -0.34; P < 0.03) between epilepsy prevalence and mean distance from the nearest river of the villages in each endemicity level (respectively, 9.5, 5.9, and 2.4 Km) [57]. A positive correlation between epilepsy and onchocerciasis, albeit being weaker, was also observed in the Imo river basin in Nigeria: (r = 0.38; P < 0.043) [39,58].…”

Onchocerciasis Fingerprints in the Geriatric Population: Does Host Immunity Play a Role?

“…volvulus infection has been reported in all age groups, from children younger than 10 years to adults over 50 years of age. Although not always consistent, reports have generally revealed an increase in the prevalence of onchocerciasis with increasing age (see Table 1) [12][13][14][15][95][96][97][98][99][100], and the duration of stay in an onchocerciasis-endemic community is thought to be one of the main predictors of onchocercal infection [13]. This may be ascribed to the fact that the rate of larval stage 3 infecting the human host is greater than the rate of death of the adult worms [13,15,95,96,98,101].…”

“…Several studies have unequivocally revealed an increase in the prevalence of onchocerciasis infection among older people, aged 50 years and above, living in endemic regions [12][13][14][15]. Most lymphatic complications, skin and eye lesions due to onchocerciasis are more frequent among the elderly population.…”