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Chikungunya virus (CHIKV) is a re-emerging arbovirus known to cause chronic myalgia and arthralgia with high morbidity. CHIKV is now considered endemic in many countries across Asia and Africa. In this study, the susceptibility of various human, mammalian and mosquito cell lines to CHIKV infection was evaluated. CHIKV infection was found to be cell-type dependent and virus strain-specific. Furthermore, SJCRH30 (human rhabdomyosarcoma cell line) was showed to be highly permissive to CHIKV infection, with maximum production of infectious virions observed at 12 h.p.i. Pre-infection treatment of SJCRH30 with various inhibitors of endocytosis, including monodansylcadaverine (receptor-mediated endocytic inhibitor), dynasore (clathrin-mediated endocytic inhibitor), as well as filipin (caveolin-mediated endocytosis inhibitor), resulted in minimal inhibition of CHIKV infection. In contrast, dose-dependent inhibition of CHIKV infection was observed with the treatment of macropinocytosis inhibitor, 5-(N-ethyl-N-isopropyl)amiloride (EIPA). Furthermore, siRNA-mediated knockdown of sortin nexin 9 (SNX9) a protein involved in macropinosome formation, also resulted in a significant dose-dependent reduction in viral titre. By performing a virus entry assay, CHIKV particles were also observed to colocalize with FITC-dextran, a macropinosome marker. This study shows for the first time, that the infectious entry of CHIKV into human muscle cells is mediated by macropinocytosis. Together, the data from this study may pave the way for the development of specific inhibitors that target the entry process of CHIKV into cells. [ABSTRACT FROM AUTHOR]

Contact patterns strongly influence the dynamics of disease transmission in both human and non-human animal populations. Domestic dogs Canis familiaris are a social species and are a reservoir for several zoonotic infections, yet few studies have empirically determined contact patterns within dog populations. Using high-resolution proximity logging technology, we characterised the contact networks of free-ranging domestic dogs from two settlements (n = 108 dogs, covering >80% of the population in each settlement) in rural Chad. We used these data to simulate the transmission of an infection comparable to rabies and investigated the effects of including observed contact heterogeneities on epidemic outcomes. We found that dog contact networks displayed considerable heterogeneity, particularly in the duration of contacts and that the network had communities that were highly correlated with household membership. Simulations using observed contact networks had smaller epidemic sizes than those that assumed random mixing, demonstrating the unsuitability of homogenous mixing models in predicting epidemic outcomes. When contact heterogeneities were included in simulations, the network position of the individual initially infected had an important effect on epidemic outcomes. The risk of an epidemic occurring was best predicted by the initially infected individual’s ranked degree, while epidemic size was best predicted by the individual’s ranked eigenvector centrality. For dogs in one settlement, we found that ranked eigenvector centrality was correlated with range size. Our results demonstrate that observed heterogeneities in contacts are important for the prediction of epidemiological outcomes in free-ranging domestic dogs. We show that individuals presenting a higher risk for disease transmission can be identified by their network position and provide evidence that observable traits hold potential for informing targeted disease management strategies. [ABSTRACT FROM AUTHOR]

Background: Recent outbreaks of dengue and other Aedes aegypti-borne arboviruses highlight the importance of a rapid response for effective vector control. Data on insecticide resistance and underlying mechanisms are essential for outbreak preparedness, but are sparse in much of Africa. We investigated the levels and heterogeneity of insecticide resistance and mechanisms of Ae. aegypti from contrasting settings within and around Ouagadougou, Burkina Faso. Methodology/Principal findings: Bioassays were performed on larvae and adults to diagnose prevalence of resistance, and to assess levels where resistance was detected. Investigation of resistance mechanisms was performed using synergist bioassays, knockdown resistance (kdr) target site mutation genotyping and quantitative PCR expression analysis of candidate P450 genes. Larval dose-response assays indicated susceptibility to the organophosphates tested. Adult females were also susceptible to organophosphates, but resistance to carbamates was suspected in urban and semi-urban localities. Females from all localities showed resistance to pyrethroids but resistance prevalence and level were higher in urban and especially in semi-urban areas, compared to the rural population. Environment was also associated with susceptibility: adults reared from larvae collected in tires from the semi-urban site were significantly less resistant to pyrethroids than those collected from large outdoor drinking water containers (‘drums’). Susceptibility to both pyrethroids tested was largely restored by pre-exposure to Piperonyl Butoxide (PBO), suggesting a strong metabolic basis to resistance. The 1534C kdr mutation was nearly fixed in semi-urban and urban areas but was far less common in the rural area, where the 1016I kdr mutation frequency was also significantly lower. P450 gene analysis detected limited over-expression of single candidates but significantly elevated average expression in the semi-urban site compared to both a susceptible laboratory colony, and females from the other collection sites. Conclusions/Significance: Our results reveal pyrethroid resistance and paired kdr mutations in both urban and semi-urban sites at levels that are unprecedented for mainland Africa. The combination of target site and metabolic mechanisms is common in Ae. aegypti populations from other continents but is a worrying finding for African populations. However, organophosphate insecticides are still active against both larvae and adults of Ae. aegypti, providing useful insecticidal options for control and resistance management. [ABSTRACT FROM AUTHOR]

Background: Cholera remains a substantial health burden in Asia and Africa particularly in resource poor settings. The standard procedures to identify the etiological organism V. cholerae are isolation from microbiological culture from stool as well as Polymerase Chain Reaction (PCR). Both the processes are highly lab oriented, labor extensive, time consuming, and expensive. In an effort to control for outbreaks and epidemics; an effective, convenient, quick and relatively less expensive detection method is imperative, without compromising the sensitivity and specificity that exists at present. The objective of this component of the study was to evaluate the effectiveness of a locally produced rapid diagnostic test (RDT) for cholera diagnosis. Methods: In Bangladesh, nationwide cholera surveillance is ongoing in 22 hospitals covering all 8 divisions of the country since June, 2016. In the surveillance, stool samples have been collected from patients presenting to hospitals with acute watery diarrhea. Crystal VCTM (Span diagnostics, India) and Cholkit (locally produced RDT) have been used to detect V. cholerae from stool samples. Samples have also been sent to the main laboratory at icddr,b where the culture based isolation is routinely performed. All the tests were carried out for both direct and enriched stool samples. RDT sensitivity and specificity were calculated using stool culture as the gold standard. Results: A total of 7720 samples were tested. Among these, 5865 samples were solely tested with Crystal VC and 1355 samples with Cholkit whereas 381 samples were tested with both the RDTs. In comparison with culture, direct testing with Crystal VC showed a sensitivity of 72% (95% CI: 50.6% to 87.9%) and specificity of 86.8% (95% CI: 82.8% to 90.1%). After enrichment the sensitivity and specificity was 68% (95% CI: 46.5% to 85.1%) and 97.5% (95% CI: 95.3% to 98.8%) respectively. The direct Cholkit test showed sensitivity of 76% (95% CI: 54.9% to 90.6%) and specificity of 90.2% (95% CI: 86.6% to 93.1%). Conclusion: This evaluation has demonstrated that the sensitivity and specificity of Cholkit is similar to the commercially available test, Crystal VC when used in field settings for detecting V. cholerae from stool specimens. The findings from this study suggest that the Cholkit could be a possible alternative for cholera endemic regions where V. cholerae O1 is the major causative organism causing cholera. [ABSTRACT FROM AUTHOR]