Integrated xenosurveillance of Loa loa, Wuchereria bancrofti, Mansonella perstans and Plasmodium falciparum using mosquito carcasses and faeces: A pilot study in Cameroon

Abstract

Background Community presence of loiasis must be determined before mass drug administration programmes for lymphatic filariasis and onchocerciasis can be implemented. However, taking human blood samples for loiasis surveillance is invasive and operationally challenging. A xenosurveillance approach based on the molecular screening of mosquitoes and their excreta/feces (E/F) for Loa loa DNA may provide a non-invasive method for detecting the community presence of loiasis. Methods We collected 770 wild mosquitoes during a pilot study in a known loiasis transmission area in Mbalmayo, Cameroon. Of these, 376 were preserved immediately while 394 were kept in pools to collect 36-hour E/F samples before processing. Carcasses and E/F were screened for L. loa DNA. To demonstrate this method’s potential for integrated disease surveillance, the samples were further tested for Wuchereria bancrofti, Mansonella perstans, and Plasmodium falciparum. Results Despite limited sample numbers, L. loa DNA was detected in eight immediately-stored mosquitoes (2.13%; 95% CI 1.08 to 4.14), one carcass stored after providing E/F (0.25%; 95% CI 0.04 to 1.42), and three E/F samples (estimated prevalence 0.77%; 95% CI 0.15 to 2.23%). M. perstans and P. falciparum DNA were also detected in carcasses and E/F samples, while W. bancrofti DNA was detected in E/F. None of the carcasses positive for filarial worm DNA came from pools that provided a positive E/F sample, supporting the theory that, in incompetent vectors, ingested parasites undergo a rapid, complete expulsion in E/F. Conclusions Mosquito xenosurveillance may provide a useful tool for the surveillance of loiasis alongside other parasitic diseases.

Nondestructive Methods of Pathogen Detection: Importance of Mosquito Integrity in Studies of Disease Transmission and Control

“…This promising method has shown great potential for the surveillance of other circulating pathogens. Recent findings of xenosurveillance demonstrated the presence of Loa loa filaria (the causative agent of loiasis) in three EF samples obtained from wild mosquitoes, in addition to W. bancrofti , M. perstans , and P. falciparum [ 126 ].…”

Towards a practical trap for deer flies (Diptera: Tabanidae): initial tests of a bi-level Nzi trap

“…Catches of Chrysops Meigen as a whole are often 1% or less of all tabanids in all but a few African trapping studies (Sinshaw et al 2006; Koné et al 2011; Acapovi-Yao et al 2017). Hence, sweep nets are used for critical sampling in the study of loiasis (Pryce et al 2022). In the absence of convenient sampling methods, the biology of deer flies is not well documented, with most studies recording only their presence and species composition.…”