Background: Mosquito-borne viruses, such as Zika, dengue, yellow fever, and chikungunya, are important causes of human diseases nearly worldwide. The greatest health risk for arboviral disease outbreaks is the presence of the most competent and highly invasive domestic mosquito, Aedes aegypti. In Cabo Verde, two recent arbovirus outbreaks were reported, a dengue outbreak in 2009, followed by a Zika outbreak in 2015. This study is the first entomological survey for Ae. aegypti that includes all islands of Cabo Verde archipelago, in which we aim to evaluate the actual risk of vector-borne arboviruses as a continuous update of the geographical distribution of this species. Methods: In order to assess its current distribution and abundance, we undertook a mosquito larval survey in the nine inhabited islands of Cabo Verde from November 2018 to May 2019. Entomological larval survey indices were calculated, and the abundance analyzed. We collected and identified 4045 Ae. aegypti mosquitoes from 264 positive breeding sites in 22 municipalities and confirmed the presence of Ae. aegypti in every inhabited island. Results: Water drums were found to be the most prevalent containers (n = 3843; 62.9%), but puddles (n = 27; 0.4%) were the most productive habitats found. The overall average of the House, Container, and Breteau larval indices were 8.4%, 4.4%, and 10.9, respectively. However, 15 out of the 22 municipalities showed that the Breteau Index was above the epidemic risk threshold. Conclusion: These results suggest that if no vector control measures are considered to be in place, the risk of new arboviral outbreaks in Cabo Verde is high. The vector control strategy adopted must include measures of public health directed to domestic water storage and management.

Background Cape Verde is an archipelago located off the West African coast and is in a pre-elimination phase of malaria control. Since 2010, fewer than 20 Plasmodium falciparum malaria cases have been reported annually, except in 2017, when an outbreak in Praia before the rainy season led to 423 autochthonous cases. It is important to understand the genetic diversity of circulating P. falciparum to inform on drug resistance, potential transmission networks and sources of infection, including parasite importation. Methods Enrolled subjects involved malaria patients admitted to Dr Agostinho Neto Hospital at Praia city, Santiago island, Cape Verde, between July and October 2017. Neighbours and family members of enrolled cases were assessed for the presence of anti-P. falciparum antibodies. Sanger sequencing and real-time PCR was used to identify SNPs in genes associated with drug resistance (e.g., pfdhfr, pfdhps, pfmdr1, pfk13, pfcrt), and whole genome sequencing data were generated to investigate the population structure of P. falciparum parasites. Results The study analysed 190 parasite samples, 187 indigenous and 3 from imported infections. Malaria cases were distributed throughout Praia city. There were no cases of severe malaria and all patients had an adequate clinical and parasitological response after treatment. Anti-P. falciparum antibodies were not detected in the 137 neighbours and family members tested. No mutations were detected in pfdhps. The triple mutation S108N/N51I/C59R in pfdhfr and the chloroquine-resistant CVIET haplotype in the pfcrt gene were detected in almost all samples. Variations in pfk13 were identified in only one sample (R645T, E668K). The haplotype NFD for pfmdr1 was detected in the majority of samples (89.7%). Conclusions Polymorphisms in pfk13 associated with artemisinin-based combination therapy (ACT) tolerance in Southeast Asia were not detected, but the majority of the tested samples carried the pfmdr1 haplotype NFD and anti-malarial-associated mutations in the the pfcrt and pfdhfr genes. The first whole genome sequencing (WGS) was performed for Cape Verdean parasites that showed that the samples cluster together, have a very high level of similarity and are close to other parasites populations from West Africa.

IntroductionThe transmission of pathogens by blood-sucking insects to humans and other animals depends on vector-host interactions. As yet unexplored in Cape Verde, mosquito feeding behavior plays a crucial role in pathogen transmission. Herein, we aim to explore, through blood meal analysis, the relationship between mosquito species and common hosts in Santiago Island, Cape Verde.MethodsEngorged female mosquitoes were collected through mechanical aspiration from May 2016 to December 2017 in three municipalities of Santiago Island (Praia, Santa Cruz, and Santa Catarina). Blood-feeding behavior in each municipality was assessed through blood meal analysis using an enzyme-linked immunosorbent assay (ELISA).ResultsWe were able to determine that single-host blood meals were common in Aedes aegypti, Anopheles arabiensis, and Culex pipiens sensu lato (s.l.). In general, the mosquitoes preferred to feed on humans, dogs, and chickens, and on multiple hosts, mainly two hosts. The human blood index (HBI) was highest (i.e., 1.00) in Ae. aegypti, with the lowest value (0.40) observed in An. arabiensis. It was observed that, among single-host blood meals, the likelihood of Cx. pipiens s.l. feeding on humans was significantly high, whereas the likelihood of An. arabiensis feeding on humans was significantly low (log-odds ratio (LOR) = 0.85 and –2.44, respectively). In addition, a high likelihood of Ae. aegypti feeding on humans was observed, but this was not statistically significant (LOR = 0.85).DiscussionOverall, our findings demonstrate a lack of feeding preference in Culex pipiens s.l. compared with Ae. aegypti and An. arabiensis. These results provide insights into possible parasite transmission and pathogen spillover/spillback, which threaten human/animal health and the economy in Cape Verde.

BackgroundDetermining the reproductive rate and how it varies over time and space (RT) provides important insight to understand transmission of a given disease and inform optimal strategies for controlling or eliminating it. Estimating RT for malaria is difficult partly due to the widespread use of interventions and immunity to disease masking incident infections. A malaria outbreak in Praia, Cabo Verde in 2017 provided a unique opportunity to estimate RT directly, providing a proxy for the intensity of vector-human contact and measure the impact of vector control measures.MethodsOut of 442 confirmed malaria cases reported in 2017 in Praia, 321 (73%) were geolocated and informed this analysis. RT was calculated using the joint likelihood of transmission between two cases, based on the time (serial interval) and physical distance (spatial interval) between them. Log-linear regression was used to estimate factors associated with changes in RT, including the impact of vector control interventions. A geostatistical model was developed to highlight areas receptive to transmission where vector control activities could be focused in future to prevent or interrupt transmission.ResultsThe RT from individual cases ranged between 0 and 11 with a median serial- and spatial-interval of 34 days [interquartile range (IQR): 17–52] and 1,347 m (IQR: 832–1,985 m), respectively. The number of households receiving indoor residual spraying (IRS) 4 weeks prior was associated with a reduction in RT by 0.84 [95% confidence interval (CI) 0.80–0.89; p-value <0.001] in the peak-and post-epidemic compared to the pre-epidemic period.ConclusionsIdentifying the effect of reduced human-vector contact through IRS is essential to determining optimal intervention strategies that modify the likelihood of malaria transmission and can inform optimal intervention strategies to accelerate time to elimination. The distance within which two cases are plausibly linked is important for the potential scale of any reactive interventions as well as classifying infections as imported or introduced and confirming malaria elimination.

BackgroundCape Verde is an archipelago located off the West African coast, and is in a pre-elimination phase of malaria control. Since 2010, less than 20 Plasmodium falciparum malaria cases have been reported annually, except in 2017, when an outbreak in Praia before the rainy season led to 423 autochthonous cases. It is important to understand the genetic diversity of circulating P. falciparum to inform on drug resistance, potential transmission networks, and sources of infection, including parasite importation.MethodsEnrolled subjects involved malaria patients admitted to Dr. Agostinho Neto Hospital at Praia city, Santiago island, Cape Verde, between July and October 2017. Neighbours and family members of enrolled cases were assessed for the presence of anti-P. falciparum antibodies. Sanger sequencing and real time PCR was used to identify SNPs in genes associated with drug resistance (e.g. pfdhfr, pfdhps, pfmdr1, pfk13, pfcrt), and whole genome sequencing data was generated to investigate the population structure of P. falciparum parasites.ResultsWe analysed 190 parasite samples, 187 indigenous and three from imported infections. Malaria cases were distributed throughout Praia city. There were no cases of severe malaria, and all patients had an adequate clinical and parasitological response after treatment. Anti-P. falciparum antibodies were not detected in the 137 neighbours and family members tested. No mutations were detected in pfdhps. The triple mutation S108N/N51I/C59R in pfdhfr and the chloroquine resistant CVIET haplotype in the pfcrt gene were detected in almost all samples. Variations in pfk13 were identified in only one sample (R645T, E668K). The haplotype NFD for pfmdr1 was detected in the majority of samples (89.7%).ConclusionsPolymorphisms in pfk13 associated with ACTs tolerance in Southeast Asia were not detected, but the majority of the tested samples carried the pfmdr1 haplotype NFD and antimalarial associated mutations in the the pfcrt and pfdhfr genes. We performed the first WGS for Cape Verdean parasites that showed that the samples cluster together, have a very high level of similarity and are close to other parasites populations from West Africa.