Vector–host interactions play a key role in pathogen transmission. More than half of the world’s population lives in areas at risk of one or more major vector-borne diseases, with mosquito-borne diseases being a major contributor (1). Mosquitoes are known to be vectors of diseases that are devastating to humans, domestic animals, and wildlife (2).

Hematophagy is an obligatory behavior for most female mosquitoes in order to reproduce and to obtain energy (3). This process is facilitated through catheterization of the skin (solenophagy), as a result of which pathogens are ingested and transmitted. Orientation toward a host is paramount for feeding success, and in the case of temporary ectoparasites, such as mosquitoes, host choice is underpinned by single or multiple factors, such as host availability (4–8), abundance (8–11), season shifting (4, 12), natural host defense (particularly in Aves) (13–17), host size (18–21), odor (22–24), and ecology (8, 25) leading to catholic tastes in a single gonotrophic cycle, which may favor parasite transmission.

The ability to precisely identify the source of blood meal in mosquitoes and to distinguish anthropophilic and zoophilic species is of prime importance for deciphering host choice and how parasites manipulate the host to promote infection and transmission, and for understanding disease epidemiology for improved entomological surveillance (2, 26–29).

Mosquito-borne pathogens, including yellow fever virus (30), Wuchereria bancrofti (31), Zika virus (32, 33), dengue virus (34), Plasmodium spp (35). Dirofilaria immitis (36), and Dirofilaria repens (37), which are of public health importance, have been reported in Cape Verde. To date, 11 species of mosquito have been described in Cape Verde, of which Anopheles arabiensis, Aedes aegypti, Culex pipiens sensu stricto (s.s.), and Culex quinquefasciatus are the most important (38–40).

Nevertheless, mosquito bites and diseases may be preventable by decreasing contact with humans through zooprophylaxis, by the use of repellant air-sprays and house improvements, and, at an individual level, by covering the skin and using insecticide-treated bed nets (1, 6, 23, 41–47). Thus, integrated vector management (IVM) with multiple strategies, included as part of the One Health Initiative, has greater potential to improve vector-borne disease control and facilitate elimination than isolated or routine approaches (48, 49). Understanding the temporal and spatial dynamics of the vector–host relationships is a key element in planning IVM.

Entomological studies in Cape Verde have focused more on mosquito density, distribution, and genetic and phenotypic composition than on feeding behaviors, although these are crucial for disease transmission. In our study, we investigated the blood feeding patterns of mosquitoes in three municipalities in Santiago Island: Praia, Santa Cruz, and Santa Catarina.

A total of 1,008 mosquito specimens freshly blood fed and with intermediary blood digestion were analyzed from the three municipalities of Santiago Island: Praia (n = 834; 83%), Santa Cruz (n = 127; 13%), and Santa Catarina (n = 47; 5%). The majority of these, 860 specimens, were Cx. pipiens s.l. (85%), followed by Ae. aegypti (n = 103; 10%) and An. arabiensis (n = 45; 4%) ( Table 1 ). No engorged An. arabiensis or Ae. aegypti were caught in Santa Catarina.

Single-host blood meals were more common [Ae.aegypti (84.3%), An. arabiensis (64.7%), and Cx. pipiens s.l. (81.6%)] than multiple-host blood meals [Ae. aegypti (15.7%), An. arabiensis (35.3%), and Cx. pipiens s.l. (18.4%)]. Single-host blood meals were mainly represented by human blood (56 for Ae. Aegypti, nine for An. arabiensis, and 581 for Cx. pipiens s.l.). Regarding multiple-host blood meals, the mosquitoes fed on human and other animal hosts (18 for Ae. Aegypti, 15 for An. Arabiensis, and 159 for Cx. pipiens s.l.). Following humans, dogs were the most frequent host among Cx. pipiens s.l. (represented 116 times) ( Table 1 ).

As regards the HBI, the lowest HBI (0.40) was recorded in An. arabiensis, whereas Ae. aegypti from the municipality of Santa Cruz had the highest HBI (1.00). The overall average HBIs in the Santiago Island were 0.98, 0.55, and 0.92 for Ae. aegypti, An. arabiensis, and Cx. pipiens s.l., respectively ( Table 1 ).

The calculated probabilities of mosquito species taking a single-host blood meal from humans indicated that, for Cx. pipiens s.l., the probability was lowest in Santa Catarina (HBI = 0.88; 95% CI 0.71 to 0.96) and highest in Santa Cruz (HBI= 0.93; 95% CI 0.84 to 0.97). Whereas for An. arabiensis the chance was lower (HBI = 0.40; 95% CI 0.07 to 0.83) but higher (HBI = 1.00; 95% CI 0.63 to 1.00) for Ae. aegypti in the Santa Cruz municipality ( Table 2 ).

Only An. arabiensis took single-host blood meals from all five hosts (pigs, humans, goats, dogs, and chickens) especially in urban areas like Praia during the rainy season ( Figure 2 ). Cx. pipiens s.l. had a higher preference for human blood, followed by chicken, and this preference did not differ across seasons, municipalities, or land uses ( Figure 3 ). Ae. aegypti also preferred to feed on humans but this preference did not differ across seasons and was not different in Praia and Santa Cruz, the two municipalities where it was possible to capture this mosquito species ( Figure 4 ).

The LOR calculated only for single-host blood meals clustered together Cx. pipiens s.l. and Ae. aegypti with similar feeding patterns. These estimations revealed positive LORs for all the mosquito–host relationships; however, the Cx. pipiens s.l.–dogs and Cx. pipiens s.l.–goats relationships show negative LORs, i.e., negative associations. This is similar to An. arabiensis–human host ( Figure 5 ).

Significant positive or negative associations were found for two out of the five hosts (humans and goats). There was a significant clustering positive LOR (LOR = 0.85, p = 0.01) for Cx. pipiens s.l. for human hosts and a strong negative association for goats (LOR = –4.38, p < 0.0001), meaning a higher and a lower likelihood of this mosquito species taking blood from humans and goats, respectively. Similarly, positive associations between Ae. aegypti and humans (LOR = 0.85, p = 0.10) and between Ae. aegypti and pigs (LOR = 2.44, p = 0.16) were observed, but these were not statistically significant. For An. arabiensis–humans a significant strong negative correlation (LOR = –2.44, p < 0.0001) was observed, which points to a lower likelihood of this mosquito species biting humans. A strong positive association was observed between An. arabiensis and goats (LOR = 5.30, p = 7.80) and between An. arabiensis and pigs (LOR = 3.51, p = 0.06), but these associations were not statistically significant. An LOR value closer to 0 was found only for Ae. Aegypti–dogs, which suggests no relationship (LOR = 0.02, p = 0.64) ( Figure 5 ).

The transmission potential of a vector-borne pathogen by a competent vector is influenced to a large extent by blood feeding behavior, vector population density, and longevity (56). In our study, data gathered from multiple sites indicate that the major pathogen vectors (i.e., An. arabiensis, Ae. aegypti, and Cx. pipiens s.l.) share up to three hosts, although this may be influenced by host availability rather than by species-specific host choices. A limitation at this point is the fact that our data could be more accurate if PCR-based molecular approaches were used. Despite Praia being more urbanized, multiple-host blood meals (from four or five hosts) were also observed ( Table 1 ). This observation is not new in mosquitoes, as shown in studies in Brazil, Honduras, and Peru (57–60).

A pertinent result that we found was the generic feeding behavior among An. arabiensis and Cx. pipiens s.l., in contrast to Ae. aegypti, which showed a specific feeding behavior with a strong predilection for human hosts (HBI_{single-host + multiple-host blood meals} = 0.98; HBI_{single-host blood meals} = 0.95). Work carried out in Grenada, the USA, Thailand, Puerto Rico, and Australia also found similar feeding behaviors in Ae. aegypti (61–67), as humans provide reproductive and metabolic advantages (68). This feeding behavior could be one of various factors that would explain the large number of cases of dengue fever in 2009 (34) and of Zika in 2015 (32) in Cape Verde, and this is also a point of consideration, as Ae. aegypti from Cape Verde is also able to transmit the Chikungunya virus (69).

Few (n = 45) blood-fed An. arabiensis were caught, which limits conclusions on any blood meal analyses. These low numbers could be due to the collection technique employed (70), as we collected only mosquitoes that were within range of the suction effect of the aspirator. It is likely that the use of a collecting tool with wider coverage, such as pyrethrum spray catches, would have increased the numbers collected. In any case, in our study, An. arabiensis showed low anthropophily [HBI_{single-host + multiple-host blood meals =} 0.55; HBI_{single-host blood meals} = 0.41(LOR = –2.44, p < 0.0001)], similar to the findings of studies in Burkina Faso, Kenya, and Ethiopia (71–73). We verified that An. Arabiensis fed from multiple hosts in the same gonotrophic cycle (from two to four hosts), which agrees with the gonotrophic discordance phenomenon previously described in other species of this genus in Ethiopia, Brazil, Kenya, Mexico, and Sri Lanka (73–78). The low anthropophily observed in this species could also explain the relatively low prevalence of malaria in Cape Verde, in contrast to other countries in Africa, where the main malaria vector, An. gambiae s.s., is, essentially, anthropophilic (79).

Although there have been reports of D. immitis and D. repens among dogs in Cape Verde (80–87), and the West Nile virus and W. bancrofti in other African countries (31, 88, 89), Cx. Pipiens s.l. has not been implicated in any human disease in Cape Verde. Two species of the Cx. pipiens complex, Cx. pipiens s.s. (ornithophilic) and Cx. quinquefasciatus (anthropophilic), and their hybrids, have been observed in Cape Verde (90). Both species are more eclectic than An. Arabiensis and Ae. Aegypti. In our study Cx. pipiens s.l. showed a preference for human blood meals (HBI_{single-host + multiple-host blood meals} = 0.92; HBI_{single-host blood meals} = 0.91 [LOR = 0.85, p = 0.01]) followed by blood meals in chickens and dogs. Similar trends have been found in Grenada, the USA, Ecuador, India, Brazil, Germany, Australia, and Kenya (61, 62, 91–98).

The mosquito feeding behavior observed in our study demonstrates that it is important to consider the closeness of dogs to humans and their role in parasite transmission. Although humans are dead-end hosts for D. immitis and D. repens (both found in dogs in Cape Verde), earlier stages can cause dirofilariasis and inflammatory response when parasites die in human tissues (99). Ocular and pulmonary dirofilariasis with benign pulmonary and subcutaneous nodules that may be confused with cancer can also be found in humans (99–102). In addition to Cx. pipiens s.l., Ae. aegypti has also been implicated in the transmission of both parasites, although we observed a low probability of this species biting dogs ( Table 1 , Figure 5 ) (87, 103, 104).

It is possible that our results could be a reflection more of host availability than of mosquito host preference: the high numbers of Cx. pipiens s.l. and Ae. aegypti individuals collected and their feeding behaviors (on both humans and domestic animals), as reported in this study, call for further investigations into parasites circulating in these mosquitoes and also in dogs and humans in Cape Verde. For situations where humans would behave as amplifying hosts of other dog parasites not mentioned here, from our results of simultaneous blood meals in dogs and humans, we may have an even greater amplification event due to interaction augmentation between these two hosts, which increases as their abundance also increases (105). However, as pointed out elsewhere (18, 106, 107), it is necessary to consider the specific attributes to such interactions.

Future directions from this study should therefore consider on combining data from mosquito and animal densities and richness to explore transmission risk according to season and land use. In addition, considering a larger panel of hosts, including non-domestic animals, and increasing sampling efforts with proper sampling techniques, will ensure enough representation of samples for biological relevance of data generated. Another limitation is that we did not record the total number of collected mosquitoes. Therefore, we cannot provide the percentage of blood-fed mosquitoes for our field study.

In conclusion, our study provides the first characterization of blood sources utilized by medically important mosquitoes in Santiago Island, Cape Verde. Importantly, this work has shown that feeding behavior among Cx. pipiens s.l. is more random than that demonstrated by Ae. aegypti and An. arabiensis. Our findings also provide interesting information on disease transmission between hosts and pathogens spillover or spillback phenomena. These phenomena, despite the fact that they have not yet been thoroughly investigated in the country, could threaten livestock, poultry farming, wildlife health, and the economy, and this may be even more important in view of climate change. Thus, inclusion of the One Health Initiative (involving animals) in disease surveillance could help track diseases of humans with animal ancestry and zoonosis for planning interventions. Interventions such as zooprophylaxis, in which animals are treated with mosquito-killing drugs, and mosquito bites are redirected can greatly reduce mosquito survival and lower their potential to transmit pathogens.

The original contributions presented in the study are included in the article/Supplementary Material. Further enquiries can be directed to the corresponding author.

AG and SL conceived and directed the study. AG, DM, IV, and AD performed species identification. AG, DM, IV, and AD undertook sample processing, DNA extraction, and molecular assays. AG and AD performed data analyses. AG and AD interpreted results. AG wrote the first draft of the manuscript with inputs from SL and AD. All authors commented on and edited the draft manuscript and approved the final manuscript. AG and SL compiled the final manuscript. All authors contributed to the article and approved the submitted version.