REVERSE MOLECULAR EPIDEMIOLOGY: INSIGHTS INTO THE INFECTION DYNAMICS OF BLOOD-BORNE HUMAN PARASITES IN A LOA LOA-, MANSONELLA PERSTANS- AND PLASMODIUM FALCIPARUM-ENDEMIC REGION OF CAMEROON

The study of the interactions among parasites within their hosts is crucial to the understanding of epidemiology of disease and for the design of effective control strategies. We have conducted an assessment of infections with Loa loa, Mansonella perstans, Wuchereria bancrofti, and Plasmodium falcipanim in eastern Cameroon using a highly sensitive and specific quantitative polymerase chain reaction assay using archived dried whole blood spots. The resident population (N = 1,085) was parasitized with M. perstans (76%), L. loa (39%), and P falciparum (33%), but not with W bancrofti. Compared with single infections (40.1%), coinfection was more common (48.8%): 21.0% had L. loa-M. perstans (Ll(+)/Mp(+)/Pf(-)), 2.7% had L. loa-P. falciparum (Ll(+)/Pf(+)/Mp(-)), 15.1% had M. perstans-P. falciparum (Mp(+)/Pr+/ Ll(-)), and 10.0% had L. loa-M. perstans-P falciparum (Ll(+)/Mp(+)/Pf(+)). Interestingly, those with all three infections (Ll(+)/Mp+/Pf) had significantly higher L. loa microfilaria (mf) counts than either single Ll+ (P = 0.004) or double Ll(+)/Mp+ (P = 0.024) infected individuals. Of those infected with L. loa, the mean estimated counts of L. loa mf varied based on location and were positively correlated with estimated intensities of M. perstans mf. Finally, at a community level, heavy L. loa infections were concentrated in a few individuals whereby they were likely the major reservoir for infection.