Human loa loa (Cobbold, 1864) (Filaroidea: Onchocercidae) morbidity distribution in northern Enugu State, Nigeria: implications for onchocerciasis control

Abstract

A cross-sectional epidemological investigation was conducted in Nsukka senatorial zone of Nigeriato evaluate the use of specific clinical signs/symptoms in the assessment of the endemicity, prevalence and morbidity of Loa loa infection in areas meso-endemic for onchocerciasis, and to evaluate the results in respect of the probability of occurrence of adverse reactons, post-treatmentwith ivermectin in areas presumed to be hypo-, meso-, and hyper endemic for Loa loa infection and morbidity. Standard questionnaire based on the key clinical manifesations of loiass were administered and the micofilaraemic levels of respondents determined at both community and individual levels. The results showed that the clinica symptoms/signs were known in all the studycommunities. Altogether 22.0% o respondents (n=1600) positively indicated having experienced either Loa loa infection and/ or Calabar swelling. Based on the questonnaire indices, an intercommunity prevalence of 21.9% (range 17.50 - 27.50%) was establshed An overall communiy medan microfaraemia (mf) prevalence of 19.4% (range 15.0 - 26.3%) was also recorded. A microfilaraemia prevalence >20% was however established in >35% of the study communities indicating the possibility of adverse reaction after ivermectin administration. More males (n=203, 12.7%) than females (n=109, 6.8%) were microfaraemic. Linear logistic regression indicated that Loa loa infection was significantly associated with age (adjusted odds rato: 1.12, 95% confidence interval: 1.00-1.14, p<0.001). The intercommuniy mean intensiy o microfilarial load varied (range 112 ± 25 – 205 ± 30).The best diagnostic performance was obtaned for reported history of L. loa wth a sensitiviy of 100% and a specificiy of 94.6%.

Keywords: Epidemiology, Loiasis, Onchocerciasis, Adverse reaction, Microfilaraemia, Implications for Control