Detection of Wuchereria bancrofti in human blood samples and mosquitoes in Matayos, Busia County-Kenya

Subclinical Inflammation in Asymptomatic Schoolchildren With Plasmodium falciparum Parasitemia Correlates With Impaired Cognition

BACKGROUND

Subclinical inflammation and cognitive deficits have been separately associated with asymptomatic Plasmodium falciparum infections in schoolchildren. However, whether parasite-induced inflammation is associated with worse cognition has not been addressed. We conducted a cross-sectional pilot study to better assess the effect of asymptomatic P. falciparum parasitemia and inflammation on cognition in Kenyan schoolchildren.

METHODS

We enrolled 240 children aged 7-14 years residing in high malaria transmission in Western Kenya. Children performed five fluid cognition tests from a culturally adapted NIH toolbox and provided blood samples for blood smears and laboratory testing. Parasite densities and plasma concentrations of 14 cytokines were determined by quantitative PCR and multiplex immunoassay, respectively. Linear regression models were used to determine the effects of parasitemia and plasma cytokine concentrations on each of the cognitive scores as well as a composite cognitive score while controlling for age, gender, maternal education, and an interaction between age and P. falciparum infection status.

RESULTS

Plasma concentrations of TNF, IL-6, IL-8, and IL-10 negatively correlated with the composite score and at least one of the individual cognitive tests. Parasite density in parasitemic children negatively correlated with the composite score and measures of cognitive flexibility and attention. In the adjusted model, parasite density and TNF, but not P. falciparum infection status, independently predicted lower cognitive composite scores. By mediation analysis, TNF significantly mediated ~29% of the negative effect of parasitemia on cognition.

CONCLUSIONS

Among schoolchildren with PCR-confirmed asymptomatic P. falciparum infections, the negative effect of parasitemia on cognition could be mediated, in part, by subclinical inflammation. Additional studies are needed to validate our findings in settings of lower malaria transmission and address potential confounders that could affect both inflammation and cognitive performance.

Detection of Wuchereria bancrofti DNA in wild caught vector and non-vector mosquitoes: implications for elimination of lymphatic filariasis

BACKGROUND

Transmission Assessment Survey (TAS) is the WHO recommended method used for decision-making to stop or continue the MDA in lymphatic filariasis (LF) elimination programme. The WHO has also recommended Molecular Xenomonitoring (MX) of LF infection in vectors as an adjunct tool in settings under post-MDA or validation period. Screening of non-vectors by MX in post-MDA / validation settings could be useful to prevent a resurgence of LF infection, as there might be low abundance of vectors, especially in some seasons. In this study, we investigated the presence of LF infection in non-vectors in an area endemic for LF and has undergone many rounds of annual MDA with two drugs (Diethylcarbamazine and Albendazole, DA) and two rounds of triple drug regimens (Ivermectin + DA).

METHODS AND RESULTS

Mosquitoes were collected from selected villages of Yadgir district in Karnataka state, India, during 2019. A total of 680 female mosquitoes were collected, identified morphologically by species and separated as pools. The female mosquitoes belonging to 3 species viz., Anopheles subpictus, Culex gelidus and Culex quinquefaciatus were separated, pooled, and the DNA extracted using less expensive method and followed by LDR based real-time PCR assay for detecting Wuchereria bancrofti infection in vector as well as non-vector mosquitoes. One pool out of 6 pools of An. subpictus, 2 pools out of 6 pools of Cx. gelidus, and 4 pools out of 8 pools of Cx. quinquefaciatus were found to be positive for W. bancrofti infection by RT-PCR. The infection rate in vectors and non-vectors was found to be 1.8% (95% CI: 0.5-4.2%) and 0.9% (95% CI: 0.2-2.3%), respectively.

CONCLUSIONS

Our study showed that non-vectors also harbour W. bancrofti, thus opening an opportunity of using these mosquitoes as surrogate vectors for assessing risk of transmission to humans in LF endemic and post MDA areas.