Multiple filarial species microfilaraemia: a comparative study of areas with endemic and sporadic onchocerciasis.

BACKGROUND &
OBJECTIVES: The study was aimed at determining the pattern of co-occurrence of species of microfilaraemia between onchocerciasis endemic and sporadic populations.
METHODS: From every consenting person of one year and above, 50 μl of day and night blood samples were collected and processed respectively with Haemotoxylin and Giemsa as vital stains. Two skin snips (one each from the waist and the shoulder) were also taken from these individuals and processed.
RESULTS: Results showed single species microfilaraemia (86.4 and 82.3%), double species microfilaraemia (12.2 and 16.9%) and triple species microfilaraemia (1.4 and 0.7%) for endemic and sporadic populations respectively. All the species had single species microfilaraemia mostly, but Mansonella perstans and Loa loa showed greatest tendency towards double and triple species microfilaraemia. The prevalence of Wuchereria bancrofti microfilaraemia among those positive for Onchocerca volvulus was significantly lower than the overall prevalence of Wuchereria bancrofti. Wuchereria bancrofti microfilaraemia was most common among those who had L. loa microfilaraemia. Wuchereria bancrofti microfilarial intensity was higher among those with M. perstans microfilaraemia than among those positive for any of the other filarial species. Similarly, the intensity of M. perstans microfilaraemia among those positive for W. bancrofti exceeded the overall intensity of M. perstans.
CONCLUSION: It is concluded that there was no definite pattern in mf densities discernible from co- occurrence infections either in the onchocerciasis endemic or sporadic population. There could be varied outcomes of onchocerciasis infection attributable to positive or negative regulatory effects of other pathogens harbored by the victims.