The impact of ivermectin on onchocerciasis in villages co-endemic for lymphatic filariasis in an area of onchocerciasis recrudescence in Burkina Faso

Abstract

In Burkina Faso, onchocerciasis was no longer a public health problem when the WHO Onchocerciasis Control Programme in West Africa closed at the end in 2002. However, epidemiological surveillance carried out from November 2010 to February of 2011, showed a recrudescence of infection in the Cascades Region. This finding was made at a time when ivermectin, a drug recommended for the treatment of both onchocerciasis and lymphatic filariasis, had been distributed in this area since 2004 for the elimination of lymphatic filariasis. It was surprising that ivermectin distributed for treating lymphatic filariasis had not prevented the recrudescence of onchocerciasis. Faced with this situation, the aim of our study was to evaluate the effectiveness of ivermectin on the onchocerciasis parasite. The percentage reduction in microfilarial load after treatment with ivermectin was used as a proxy measure for assessing possible resistance. A cohort study was carried out with 130 individuals who had tested positive for microfilariae of Onchocerca volvulus in 2010 using microscopic examination of skin-snip biopsies from five endemic villages. Subjects were followed from July 2011 to June 2012. The microfilarial load of each individual was enumerated by skin-snip biopsy in 2010, prior to the first ivermectin treatment against onchocerciasis under community guidelines. All individuals received two ivermectin treatments six months apart. In 2012, the microfilarial loads were determined again, six months after the second round of ivermectin and the reductions in parasite loads were calculated to measure the impact of the drug. The percentage reduction of the microfilarial loads ranged from 87% to 98% in the villages. In all villages, there was a statistically significant difference between the average microfilarial loads in 2010 and 2012. The level of reduction of microfilarial loads suggests that ivermectin is effective against the recrudescent population of O. volvulus in Cascades Region of Burkina Faso. Further investigations would be necessary to determine the causes of the recrudescence of onchocerciasis. (For French language abstract, see S1 Alternative Language Abstract—Translation of the Abstract into French by the authors.)

Progress towards elimination of onchocerciasis in the Region du Sud-Ouest of Burkina Faso which was previously subject to a recrudescence event after vector control

“…It seems that the situation had been stabilized after 1995 by the MDA, but there had been no obvious improvement and onchocerciasis was still a public health problem, and this was probably the result of poor geographic coverage [ 24 ]. In a multi-country study, it had been shown that CDTI produced better coverage than other methods of MDA (such as mobile teams and Community Based Treatment with Ivermectin) [ 40 ], and so the change of strategy from control to elimination was also accompanied by a change to biannual CDTI in 2013 after its successful introduction to control the recrudescence in Cascades region in 2011 [ 41 ].…”

“…The findings in the 2018 survey are very encouraging because they suggest that the region is progressing toward onchocerciasis elimination. A previous study assessing the effectiveness of the CDTI in the Cascades region, (where onchocerciasis had also been recrudescent), showed that the strategy could be applied effectively for control of onchocerciasis in Burkina Faso [ 41 ], and other studies in other parts of West Africa, East Africa and Ethiopia have also demonstrated successful interruption of onchocerciasis transmission by biannual CDTI [ 16 , 17 , 42 , 43 , 44 , 45 ]. Therefore, it seems probable that continuation of CDTI in the Sud-Ouest region of Burkina Faso, with rigorous supervision of the community distributors by health professionals, could quickly reach the goal of interruption of transmission.…”

Geospatial distribution and predictive modeling of onchocerciasis in Ogun State, Nigeria

“…Our regression model also indicated a double-fold increase in risk of infection among those who did not take ivermectin compared with those who did. Studies have reported the efficacy of ivermectin in reducing mf load and subsequently reduce transmission [ 39 , 40 ]. Therefore, there is a need to investigate the reasons for this shortfall and how to subsequently improve geographical coverage if we are to meet the elimination target.…”