Impact of repeated ivermectin treatments against onchocerciasis on the transmission of loiasis: an entomologic evaluation in central Cameroon

Particle and Fibre Toxicology

Joseph Kamgno⁵  Sébastien DS Pion⁴  Michel Boussinesq⁴  Maurice Demanou²  Jules B Tchatchueng-Mbougua³  Marc K Kouam¹ 

[1] Department of Animal Production, University of Dschang, P.O. Box 222, Dschang, Cameroon;Centre Pasteur of Cameroon, P.O. Box 1274, Yaoundé, Cameroon;Filariases and other Tropical Diseases Research Center (CRFilMT), P.O. Box 5797, Yaoundé, Cameroon;Université de Montpellier 1, 5 Boulevard IV, Montpellier 34000, France;Faculty of Medicine and Biomedical Sciences University of Yaoundé I, P.O. Box 1364, Yaoundé, Cameroon

关键词: Cameroon;    Loiasis;    C. dimidiata;    C. silacea;    Entomologic indices;    CDTI;   

Others  :  824397
DOI  :  10.1186/1756-3305-6-283

 received in 2013-05-09, accepted in 2013-09-25,  发布年份 2013

【 摘 要 】

Background

Annual community-directed treatment with ivermectin (CDTI) have been carried out since 1999 in the Lekie division (central region of Cameroon where most cases of Loa-related post ivermectin severe adverse events were reported) as part of the joined activities of the African Programme for Onchocerciasis Control (APOC) and Mectizan® Donation Program (MDP). As large-scale administration of ivermetine was demonstrated to be an efficient means to control loiasis transmission, it was hypothesized that CDTI would have lowered or halted the transmission of Loa loa in the Lekie division after 13 years of annual drug administration, indicating a possible reduction in the occurrence of Loa-related post-ivermectin severe adverse events.

Methods

A 4-month entomologic study was carried out from March to June 2012 in the Lekie division to evaluate the impact of 13 years of CDTI on the transmission of L. loa whose baseline data were recorded in 1999–2000.

Results

There was a significant reduction in the infection rate for Chrysops silacea and C. dimidiata from 6.8 and 9% in 1999–2000 to 3 and 3.6% in 2012, respectively. The differences in the infective rate (IR) (percentage of flies harboring head L3 larvae), potential infective rate (PIR) (percentage of flies bearing L3 larvae), mean head L3 larvae load (MHL3) (average L3 per infective fly) and mean fly L3 larvae load (MFL3) (average L3 per potentially infective fly) for both C. silacea and C. dimidiata were not significantly different between the two investigation periods. The biting density (BD) was almost three-fold higher in 2012 for C. silacea but not for C. dimidiata. The transmission potential (TP) which is a function of the BD, was higher in the present study than in the baseline investigation for each species.

Conclusion

The infection rate remaining high, the high TP and the stability observed in the IR, PIR, MHL3 and MFL3 after 13 years of CDTI suggest that transmission of L. loa is still active. This is an indication that the risk of occurrence of severe adverse events such as fatal encephalopathies is still present, especially for heavily microfilaria-loaded people taken ivermectin for the first time.

【 授权许可】

   
2013 Kouam et al.; licensee BioMed Central Ltd.

【 图 表 】

Figure 1.

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