Mosquitoes play a central role in the transmission of pathogens causing important diseases to humans and other animals. The incidence of zoonotic diseases has increased in recent decades, many of them caused by pathogens transmitted by mosquitoes. Due to the relevance of these diseases in public and animal health, medical and veterinary entomologists have traditionally focused their studies on the impact of mosquitoes, among other vectors, in diseases such as malaria, West Nile fever or dengue. However, the relevance of mosquitoes in the transmission of pathogens affecting wildlife have been comparatively neglected. The current volume of Ecology and Control of Vector-Borne Diseases series highlights significant and novel aspects of the ecology of diseases transmitted by mosquitoes to wildlife, contributing to the better understanding of their epidemiology. We hope this volume will influence to improve our understanding of the dynamics of transmission of mosquito-borne diseases in the wild and provide updated information on the surveillance, control and epidemiology of mosquito-borne zoonotic diseases.

The invasive species (IS) introduced in islands cause important impacts due to the vulnerability of their ecosystems. The invasive potential of certain mosquito species and their role as vectors of pathogens is one of the main concerns for public and animal health. The introduction of IS such as Aedes albopictus (Skuse 1895), Aedes aegypti (Linnaeus 1762) and Culex quinquefasciatus Say 1823 are also related to outbreaks of vector-borne diseases (VBD), such as yellow fever, dengue and Zika. Here, we review the surveillance activities on mosquito IS conducted in several islands of different origin (i.e. volcanic vs continental origin) located in different countries of the world. Those countries included Cabo Verde, Greece, Italy, Portugal, Spain and the USA. In regards to continental islands, Ae. albopictus was detected in the Balearic Islands (Spain) in 2012 despite monitoring at points of entry lead by national authorities since 2008. Greece comprises over 6,000 islands and islets with first record of Ae. albopictus in Corfu in 2003. In Italy, Ae. albopictus was first detected in Sicily in 2004 where several cases of filariasis by Dirofilaria repens in dogs and humans have been reported. Volcanic origin islands are characterised by having all mosquito fauna introduced from the continent. In Cabo Verde, Anopheles arabiensis is the main vector of malaria and can also transmit lymphatic filariasis. Ae. aegypti is also present in Cabo Verde since 1930 causing several outbreaks of dengue and Zika in 2009 and 2015. In Spain, Ae. aegypti was detected in Fuerteventura (Canary Islands) in 2017, but the fast intervention of local authorities reached its eradication in 2019. In Portugal, Ae. aegypti was first recorded in Madeira in 2006 with a single outbreak of dengue in 2012. In the USA, the islands of Hawaii have currently six established IS of mosquitoes including the four top vector species Ae. albopictus, Ae. aegypti, Aedes japonicus and Cx. quinquefasciatus, which have been implicated in outbreaks of dengue and transmission of Dirofilaria immitis and Plasmodium relictum.

Mosquito surveillance consists in the routine monitoring of mosquito populations: to determine the presence/absence of certain mosquito species; to identify changes in the abundance and/or composition of mosquito populations; to detect the presence of invasive species; to screen for mosquito-borne pathogens; and, finally, to evaluate the effectiveness of control measures. This kind of surveillance is typically performed by means of traps, which are regularly collected and manually inspected by expert entomologists for the taxonomical identification of the samples. The main problems with traditional surveillance systems are the cost in terms of time and human resources and the lag that is created between the time the trap is placed and collected. This lag can be crucial for the accurate time monitoring of mosquito population dynamics in the field, which is determinant for the precise design and implementation of risk assessment programs. New perspectives in this field include the use of smart traps and remote monitoring systems, which generate data completely interoperable and thus available for the automatic running of prediction models; the performance of risk assessments; the issuing of warnings; and the undertaking of historical analyses of infested areas. In this way, entomological surveillance could be done automatically with unprecedented accuracy and responsiveness, overcoming the problem of manual inspection labour costs. As a result, disease vector species could be detected earlier and with greater precision, enabling an improved control of outbreaks and a greater protection from diseases, thereby saving lives and millions of Euros in health costs.

Mosquitoes (Culicidae) are at the centre of worldwide entomological research and control efforts primarily because of their medical importance as vectors of diseases, like malaria, dengue, Zika, Chikungunya, West Nile or Yellow fever. They are responsible for more than half a million deaths per year. Despite their role as vectors, culicids can also cause considerable nuisance like floodwater mosquitoes frequently create as they can reproduce in a short time in enormous numbers. The consequence is that outdoor activities in parks or recreation areas are not possible and this has a detrimentrous effect on touristic activities. The most successful approach for managing nuisance or vector mosquitoes is when an integrated vector mosquito management (IVM) is implemented in which all appropriate technologies and control techniques are used, to bring about a decline of target species populations in a cost effective and environmentally safe manner. The IVM strategy can include environmental management, physical, chemical, biological or genetical components. Environmental management means physical reduction of breeding resources, water management to create conditions unfavourable for mosquito breeding. Physical control includes the use of nets and surface layers to avoid vector contact or breathing by mosquito developing stages. Chemical control by using organochlorines, organophosphates, carbamates or pyrethroids is still the most frequently practised approach to combat mosquitoes but usually these chemicals are broad-spectrum products which can have also unwanted side effects on non-target organisms and on the biodiversity when they are used in ecological sensitive areas. Therefore, biological control aiming at the reduction of target populations by the use of predators, pathogens or toxins from microorganisms are nowadays more and more in focus of control operators. Especially the use of protein toxins such as from Bacillus thuringiensis israelensis or Lysinibacillus sphaericus provide efficient control of target organisms on the one hand and environmental safety on the other hand. The increased application of biological and microbiological methods or Insect growth regulators as well as genetic methods as the Sterile Insect technique (SIT) contribute to an environmentally friendly solution of the mosquito problems. New and improved techniques like the CRISPR (clustered regularly interspaced short palindromic repeats) as a mean of editing mosquito genomes to drive desirable gene constructs into mosquito population can help in future to avoid the transmission of human pathogens. The Geographic Information System (GIS) integrated with digital mobile collection systems supported by a Global Positioning System (GPS) and modern information-technology, can significantly contribute to improving the planning, realisation and documentation of mosquito control/management operations and allow a more effective effort to reducing mosquito-borne diseases. It is out of question that all strategies should involve the public to raise the awareness of people, e.g. for the control of invasive mosquitoes by community participation.

Traditionally, mosquitoes have been studied given their relevance as vectors of pathogens that affect humans. However, in recent decades, their relevance as vectors of pathogens that affect wildlife has become evident. For this reason, multidisciplinary research disciplines have been developed focusing on the ecology, epidemiology and evolution of the interactions between pathogens and their hosts, including the transmission dynamics of diseases. However, there is a gap in the knowledge of mosquito-borne pathogens that affect wildlife, being necessary to study the taxa diversity, using genomic tools and, of course, their life cycles and their vectors. However, the information on the vector competence of mosquitoes for the transmission of pathogens that affect wild animals is certainly scarce. Interspecific and intraspecific differences have been evidenced. This would determine the capacity of mosquitoes to transmit parasites that infect wild animals. Different factors such as physiological and biochemical processes, or the mosquito microbiota could determine these differential capacities of mosquitoes to transmit pathogens.

Mosquito-borne pathogens are an important challenge for public and animal health. In the last years, invasive mosquito species have spread globally, resulting on emerging diseases in many regions of the world. A combination of several factors, such climate change, globalisation and transport have been associated to this phenomenon and scientific predictions indicate that this pattern will continue during the next decades. It is not yet clear to which extent the introductions of these vectors will negatively affect wildlife ecosystems. Most information on mosquito-borne diseases is often limited to those of medical and/or veterinary relevance, while our understanding of pathogens affecting wildlife is limited. The detection of mosquito-borne diseases in wild mammals is essential in their conservation, but also because it helps detecting emerging mosquito-borne diseases in humans. Furthermore, preventing the spillover of wildlife pathogens to humans requires a deep understanding of the dynamics of the disease in the reservoir hosts and this information is still scarce. We present a comprehensive review of the mosquito-borne pathogens that affect wild mammal species, particularly viruses and parasites. In relation to the latter, many have been described morphologically prior to the introduction of molecular techniques and therefore such information must be critical assessed. Therefore, the number of pathogens included in this chapter is far from complete but includes those with most stable information.

A great variety of microorganisms need dipterans as part of their life cycle. The dominance of these insects as vectors is differential between vertebrates; thus, they have a leading role in transmitting viruses, protozoans, and other pathogens to mammals and birds; however, they have a more discrete representation as vectors of parasites among ectotherms. Most of the parasites that affect herpetofauna are transmitted mainly by mites, ticks, leeches. At the same time, in less proportion use generalist or herpetophilic dipterans, which have developed strategies to extend their feeding sources to warm-blooded vertebrates. On the other hand, hemoparasites belonging to Apicomplexa, Trypanosomatida, and Spirurida have generated mechanisms for dissemination other than the infection by bite. This chapter aims to provide a detailed review of the current knowledge of the hemoparasites of herpetofauna transmitted by dipterans, collecting classic literature until recent research. We also discuss the life cycle transmission of these parasites and their possible implications in public health scenarios.

Zoos and wildlife parks offer a variety of biotopes and habitats for all life stages of numerous mosquito species and are places of close encounters between mosquitoes, captive animals, wild native animals and human visitors. Since stock animals of modern zoos/wildlife parks are closely observed by their keepers and medically attended by veterinarians, disease agents transmitted to them by mosquitoes will come to attention as soon as they cause symptoms or the animals are routinely checked. In addition to giving medical care to the affected animal, zoo/wildlife park staff has then the possibility to induce epidemiological investigations. The latter should be done in cooperation with the higher veterinary authority or, in case of a zoonotic disease agent, with the responsible public health authority, or with both. Zoos/wildlife parks can thus be valuable sentinel stations for detecting local circulation and transmission of mosquito-borne disease agents and significantly contribute to public health surveillance. Sometimes, zoos/wildlife parks also offer the opportunity to study mosquito-borne infections or disease cases in susceptible non-natural hosts or in natural hosts kept under non-natural conditions or exhibiting non-natural behaviour. These situations allow important insights into disease etiology and pathology as well as into vector biology. With respect to the ‘One Health’ approach, zoos, wildlife parks and similar facilities, where exotic and non-adapted animals are exposed to locally occurring (native or imported) vectorborne pathogens, should gain much more attention regarding pathogen surveillance and public health issues.

Some disease agents are readily transmitted by mosquitoes from one host species to another host species, while others like Plasmodium falciparum are host specific. This is mainly determined by the susceptibility of the host and the vector competence of the mosquito for a certain disease agent. However, the mosquito has to bite the host to be able to transmit the disease agent, which is determined by host availability and host preference. Mosquito host preference drives the transmission of vector borne pathogens within and between species. Mosquitoes with an opportunistic feeding behaviour may be responsible for the transmission of pathogens between host species, while mosquitoes with specific preferences may facilitate the maintenance of pathogen cycles within a specific host species. The factors that drive host preference and therefore disease transmission from wildlife to humans are discussed. For Chikungunya, malaria, Zika and West Nile, and overview is given of the role of mosquito host preference on the transmission to and from wildlife. The tools to study the host preferences of mosquitoes in wildlife settings are limited and are often biased or difficult and expensive to organise. Therefore, the spillover of pathogens from wildlife to humans and vice versa by mosquito vectors is still poorly understood. Because deforestation and an increased human population will lead to closer contact between wildlife, humans and mosquitoes, monitoring at locations where spillover may occur will become more important.

The identification of the vertebrate blood meal sources of mosquitoes allows insight to better understand the dynamics of vector-borne pathogens. To do so, different approaches have been used, based on the use of the remains of blood present in the abdomen of recently engorged mosquito females. Among others, different authors have used serological techniques to the more recently developed approaches based on host DNA amplification or mass spectrometry. These methods have allowed researchers to identify the vertebrate hosts of mosquitoes accurately to the species level or, even, at the individual level, providing information on the relative importance of different mosquito species in the transmission of particular pathogens. These approaches have been especially relevant to reveal the contact rates between vectors, susceptible and competent hosts, and mosquito-borne pathogens, including zoonotic ones. Additionally, these methods have revealed important asymmetries in the attraction of mosquitoes towards different host species, allowing to identify key vertebrates for the amplification of some pathogens. This chapter reviews those tools most frequently used for the identification of the blood meals of mosquitoes in order to highlight the main advantages and limitations of these methodologies.