The relationship between yellow fever and deforestation was initially established in the first half of the 20th century when ecological observations were made regarding the ability of Haemagogus mosquitoes to survive in forests with some degree of deforestation pressure ^[174][310]. In recent years, the number of cases of sylvatic yellow fever cases in Brazil have increased significantly in epizootic or transition areas and have been linked to large-scale deforestation and forest fragmentation within urbanized settings ^[175][176][311,312]. The main vectors of YFV in the Americas, Haemagogus spp. and Sabethes spp., share similar ecological and bionomic characteristics, including acrodendrophilous behavior and opportunistic feeding habits ^[177][313]. Studies on these vectors have shown that they are more abundant in sites with lower forest cover suggesting that forest fragmentation could be a critical factor in determining their presence ^[178][314]. For example, Sa. chloropterus was recently found in deforested areas adjacent to a primary forest in Costa Rica ^[179][315], indicating that deforestation could increase microhabitats for mosquito colonization, such as phytotelma and tree holes, typically used by some enzootic yellow fever vectors ^{[180][181][182]}[142,316,317]. Other studies suggest that deforestation could be pushing YFV vectors to adapt their feeding habits due to pressure from habitat disturbance. For instance, Hg. janthinomys Dyar, 1921 and other YFV vectors in Brazil were frequently observed descending to ground level in the presence of humans conducting wood extraction activities or when the non-human primate population number is small ^[183][318]. Moreover, others have found that their feeding behavior is more prolonged and aggressive at ground level than in the forest canopy ^[184][319]. Haemagogus spp. and Sabethes spp. are also eclectic feeders able to shift their host seeking among various wild or domestic animals and human hosts according to their local availability, frequently moving vertically from the top of trees to feed at ground level. However, it is not clear if this eclectic feeding behavior is innate or if it has been driven by an increase in deforestation in regions where this species occurs ^{[185][177][186][187]}[134,313,320,321]. Although there is no current evidence of active YFV transmission by Ae. aegypti or Ae. albopictus ^[188][322], experimental studies have determined that local domestic and peridomestic mosquito populations may be competent vectors for YFV strains circulating in South America ^[189][323].

The recent reemergence and dispersion of yellow fever in Brazil, potentially driven forest fragmentation near urbanized areas ^[176][312], raises the possibility of its resurgence elsewhere in the continent, including parts of Central America, where these sylvatic vectors are also present and similar ecological disturbances are taking place. The urbanization of yellow fever is one of the biggest infectious disease threats in Latin America ^[190][324]. The establishment of urban cycles, via Ae. aegypti and Ae. albopictus, could be catastrophic since these vectors are widely distributed throughout the region ^[183][318]. Most people living in urban areas of Latin America are not vaccinated, which could lead to high disease incidence that could further spread transmission ^[191][325]. It has been estimated that the proportion of infected people during an epizootic could be up to 29% under these conditions ^[192][326].

Deforestation can also affect non-human primate reservoirs of YFV and other arboviruses in the Americas. Recent studies have found a strong association between non-human primate diversity, their mobility patterns through forests, and the presence of human yellow fever cases ^[193][194][327,328]. The importance of howler monkeys (Alouatta spp.) as main reservoir host for several arboviruses, such as YFV, and their behavior must be further explored. In Costa Rica, Alouatta monkeys spend most of their day (77%) in an inactive state while a smaller proportion of their time is spent moving through the forest, feeding, or engaging in social behavior. In contrast, capuchin monkeys (Cebus spp.) spend most of the time (70–80%) day foraging or conducting other active behaviors ^[195][329]. The low activity budget of Alouatta monkeys could make them more susceptible to mosquito bites and YFV transmission, given that host movement has an important influence on the R0 in vector-borne disease systems ^[196][330]. Furthermore, Alouatta spp. can adjust their behavior to accommodate different feeding strategies as their forest habitat changes. These monkeys are found in both modified and undisturbed habitats throughout their distribution in Mexico and Central America. Their ability to adapt to changing environments is evidenced in their continued presence in regions where white-faced capuchins and spider monkeys no longer exist ^[197][331]. However, recent studies indicate that this behavior may not be spatially consistent. A recent study by Schreirer et al. (2021) in Costa Rica found that A. palliata do not appear to adjust their activity or spatial cohesion patterns in response to anthropogenic edge effects due to forest fragmentation, suggesting that these monkeys exhibit less behavioral flexibility than A. palliata at some other sites ^[198][332]. The high susceptibility of A. palliata to YFV infection and movement within disturbed or fragmented habitats could increase the risk of arbovirus transportation and exposure to humans in urbanized forest edges ^{[199][200][201][202]}[333,334,335,336].

In Latin America, the relationship between DENV and deforestation has not been clearly established or evidence is scarce. For instance, studies conducted in the Brazilian Amazon have found no association ^[203][204][337,338]. Studies conducted in other endemic DENV regions suggest that land use changes following deforestation (e.g., agriculture, settlements, or road construction) have been identified as significant dengue fever risk factors ^[164][205][300,339]. An increase in human population densities benefits DENV and its vectors through the establishment of artificial breeding habitats (i.e., water storage) and more frequent contact with susceptible populations, thus increasing the risk for virus transmission in rural and urban settings ^[206][340]. Other factors, such as proximity to paved roads and house clustering, could also promote breeding habitats ^[207][341]. The expansion of urban centers and bordering rural areas closer to the forest edge increases the chance of Ae. aegypti dispersal and colonization. For example, a study in the Peruvian Amazon by Guagliardo et al. (2014) found that the geographic spread of Ae. aegypti is driven by human transportation networks along rivers and highways in proximity to the city ^[208][342]. In this region, urban development and the availability of oviposition sites appear to contribute to the colonization of Ae. aegypti along roads. Moreover, unintentional transport of mosquitoes on boats disperses their populations over long distances into rural, riverine communities ^[208][342].

Forest fragmentation driven by land use changes could also facilitate movement of adult mosquito vectors between communities. For instance, a mark-release-recapture study by Russell et al. (2005) reported that released Ae. aegypti exhibit nonrandom patterns of dispersal with larger proportion of mosquitoes being recaptured along a corridor with heavy shading from trees and vegetation ^[209][343]. In Central America, several studies have been conducted using several vegetation indexes to evaluate correlations between vegetation coverage and dengue incidence. For example, a study by Fuller at al. (2009) was able to explain up to 83% of the variability in weekly cases of dengue fever and dengue hemorrhagic fever in Costa Rica between 2003 and 2007 based on vegetation indexes ^[210][344]. In another study, high dengue fever incidence correlated spatially with high temperature, low altitude, and a high vegetation index ^[211][345]. Moreover, ovitrap egg counts are also associated with vegetation indexes, which are dependent on temperature and rainfall, well known factors affecting vector abundance ^{[212][213][214]}[346,347,348]. Interestingly, other studies conducted in Central America revealed that dengue cases may be directly associated with tree cover and non-forested areas and inversely associated with built areas, probably because more larval habitats are available in larger, tree-covered outdoor areas with vegetation during rainfall episodes ^{[215][216][217]}[349,350,351].

In Central America, there are increasing concerns regarding the expansion of Ae. albopictus throughout the region. This important arbovirus vector species was initially detected in El Salvador, Honduras, and Guatemala in 1995; later in Panama and Nicaragua in 2002–2003; and Costa Rica and Belize between 2007 and 2009 ^{[218][219][220][221][222]}[352,353,354,355,356]. During the last decade, its distribution in Central America has expanded which is evidenced by surveillance and field study reports ^{[223][224][225][226]}[357,358,359,360], as well as by population genetic studies in Panama and Costa Rica ^[227][361]. Recent studies in Costa Rica demonstrate the adaptive capacity of this species to changes in land use and expansion of urbanized areas. For example, a study by Calderon-Arguedas et al. (2019) detected all four DENV serotypes in both Ae. albopictus female and male adults, and larvae associated with commercial pineapple farming, suggesting local horizontal and vertical transmission of DENV in the region ^[228][362]. Moreover, during these studies, most adult Ae. albopictus were collected within forest galleries bordering pineapple fields, which may indicate that forest edge habitats could serve as ecological refuges for this species in DENV endemic areas ^[229][228][186,362].

The movement of pathogens from sylvatic to amplified human transmission cycles in rural and urban settings (e.g., disease spillover) have been commonly reported in the literature; however, important questions on specific mechanisms still linger ^[230][363]. These events are typically associated with human and animal populations near forest edges, leading occasionally to urban cycles involving peridomestic vectors ^[168][231][304,364]. Arboviral disease spillover events in Central America are possible considering that these viruses share several ecological characteristics, including vectoring by anthropophilic mosquitoes in urban and rural transmission cycles, use of humans as main reservoirs, and their occurrence in habitats associated with expanding agriculture and urbanization near forest edges ^{[232][233][234]}[150,173,365]. Several studies in Central America suggest the potential for disease spillover of sylvatic arbovirus transmission cycles into rural and urbanized areas. For example, in Panama, evidence suggests that human cases of VEEV infections are associated with spillover infections from an enzootic cycle involving sylvatic rodents and Cx. (Melanoconion) spp. mosquitoes ^[41][82]. Recent clusters of human cases have occurred in Darien and Panama Provinces near rainforest and swamp habitats. In addition, entry of humans into forest galleries appears to be a risk factor for VEEV transmission ^[41][72][82,113]. Other studies suggest frequent occurrence of spillover events associated with other sylvatic arboviruses in Central America, such as MADV and MAYV ^{[41][77][161][162][235]}[82,118,129,203,211].

Conversely, spillback (e.g., reverse zoonosis) involves the movement of pathogens from urban/rural transmission cycles to sylvatic cycles between wild non-human primates and forest mosquitoes ^[236][366]. In the Americas, spillback events have been reported in several countries, including Argentina, Brazil, Colombia, and French Guyana, involving DENV, ZIKV, YFV, CHIKV, neotropical wild primates, and known mosquito vectors ^{[232][230][236][237]}[150,363,366,367]. A recent study carried out in Costa Rica found evidence of SLEV, WNV, and DENV seroprevalence in the primate species A. palliata, A. geoffroyi, and S. oerstedii (Reinhardt, 1872). Based on the collection of seropositive samples coinciding temporarily and spatially with peaks of infections in human populations, their study concluded that DENV exposure in these monkeys occurred through bidirectional human–wildlife contact or bridging vectors ^[44][85].

The ecological mechanisms by which forest disturbance triggers disease spillback events are still poorly understood, which makes it difficult to predict disease risk scenarios for future outbreaks in human-altered forest habitats and the potential establishment of sylvatic transmission cycles ^[230][236][363,366]. In Central America, where arbovirus-susceptible wild primates and known mosquito vectors are present (e.g., Haemagogus spp., Sabethes spp.), the occurrence of any one or a combination of epidemiological factors that could drive transmission is highly plausible, considering the high level of deforestation, extensive land use changes, and accelerating development of human settlements near forest edges. It is also possible that immunity of monkeys against active sylvatic arboviruses, such as YFV, could inhibit infections by DENV and ZIKV and, thus, evade the emergence of sylvatic cycles ^[236][366]. However, considering that YFV epizootics have not been reported in Central America in decades, cross-immunity to flaviviruses in non-human primates in the region may not be sufficient to suppress other arboviral infections.

Several mosquito species distributed throughout Central America could serve as bridging vectors and initiate spillback events due to their bionomic plasticity. For example, Ae. albopictus is found predominantly in urban areas, but also spreads into rural, semi-rural, and forest areas, which could potentially drive arboviruses, such as ZIKV, DENV, and CHIKV, into sylvatic transmission cycles ^[230][236][363,366]. Moreover, sylvatic vectors like Haemagogus spp. could also serve as bridging vectors since they can be opportunistic feeders, frequently imbibing on humans and monkeys, in environmentally disturbed regions along forest edges ^{[238][177][187][239]}[140,313,321,368]. These mosquito vectors tend to be opportunistic feeders, targeting hosts that are immediately available ^[172][308]. This evidence demonstrates that disease spillover is not a random process but may be the result of forest degradation increasing the likelihood of contact between humans and mosquito vectors in forest-altered sites ^[170][171][306,307].

Both spillover and spillback events occur due to increasing human activities near adjacent forest areas and where humans closely interact with wild animals and their pathogens, facilitating the “jump” or “shift” of new pathogens between different host species ^[166][302]. Despite our current knowledge of these diseases, it is still difficult to predict the risk for future outbreaks since the ecological mechanisms that drive spillovers and spillbacks in human-modified forest habitats are not well defined. Considering the accelerated rate of deforestation, unplanned urbanization and agricultural expansion near forest edges, high endemicity of multiple arboviruses, and close human contact with wildlife and vectors taking place in Central America, there is a tangible possibility that spillback and spillover events may be more frequent than reported and may surge in the future. Therefore, it is critical that more intense epidemiological and ecological monitoring systems are established in the region to help predict future epizootics and epidemics.

3.2. Impact on Malaria

In recent decades, compelling evidence linking deforestation and land use changes with malaria transmission and anopheline vector ecology in Central America have been demonstrated ^{[99][240][241][242]}[229,369,370,371]. Deforestation and land use changes can have profound anthropogenic environmental effects on malaria transmission. In general, evidence shows that, in the Americas, deforestation leads to an increased potential for malaria transmission, particularly in communities where the vector An. darlingi is present ^{[243][244][245][246][247]}[372,373,374,375,376]. Working specifically in the Darien Province of Panama, Loaiza et al. (2017) correlated increased malaria incidence rates with extensive changes in landscape, including deforestation, and an associated expansion of An. darlingi habitat. These findings were recently supported when An. darlingi was implicated as an important vector of P. vivax in the Darien region ^[170][248][306,377]. Studies in other parts of Latin America have found that the human-biting activity of An. darlingi is more intense in areas associated with deforestation and road development ^[249][378], while a study by Loaiza et al. (2008) found that the Central American malaria vectors, An. vestitipennis and An. neivai Howard, Dyar and Knab, 1913 are closely associated with specific forms of vegetation and land-use practices in Panama ^[87][217].

Other studies have suggested that agricultural land use changes and environmental pollution can significantly alter natural malaria vector habitats and even affect mosquito diversity driving disease prevalence and more dominant vector populations. For instance, a study by Chapin and Wasserstrom (1981) showed that, as early as the 1970s, expanding the acreage used for cotton cultivation, and the associated increases in pesticide use in Guatemala, Nicaragua, and El Salvador, correlated with both the emergence of DDT resistance in local malaria vectors and rapid increases in annual malaria case incidence rates, in some cases three times greater than previously recorded ^[250][379]. Similar findings were noted in Belize, where malathion use in sugarcane cultivation was associated with malathion resistance in local An. albimanus populations ^[251][380]. Another compelling case study from Belize highlights how phosphorous runoff from sugarcane cultivation in proximity to marshlands increases the amount of dense cattail (Typha domingensis) marsh habitat favored by An. vestitipennis, the most efficient malaria vector in Northern Belize, and is associated with higher larval densities ^[252][253][381,382]. Interestingly, a strategy to reduce this cattail habitat through environmental management (e.g., mowing and burning) to control An. vestitipennis populations in the area was marginally successful, with one important caveat: while the habitat management strategies significantly reduced An. vestitipennis larval populations, the resulting altered marshland habitats proved suitable for another important local vector species, An. albimanus, whose populations increased ^[254][383]. Changes in landscape structure, in the form forest cover percentage and forest density, could also lead to dominant vector populations, such as An. darlingi, increasing the risk for malaria transmission ^[255][384].

Another aspect of environmental change, like urbanization, is the global expansion of invasive malaria vectors, like An. stephensi Liston, 1901, and its potential implications for malaria control and elimination throughout Central America. Often described as a highly competent malaria vector able to breed in human-made containers, An. stephensi is known to establish and sustain outbreaks of urban malaria in previously malaria-free regions ^{[256][257][258]}[385,386,387]. While the arrival and establishment of An. stephensi in Central America is probably less likely than in Africa or other parts of Asia ^[256][385], it is nonetheless realistic to consider the possibility. Regional receptivity to the vector and its potential to impact local malaria control and elimination initiatives is poorly understood but potentially worrisome given the rapid urbanization of population centers, the high abundance of peridomestic habitats, its invasive potential, and intense human migration from malaria-endemic regions through Central America ^[259][260][388,389].

Although the risk for malaria transmission in Central America has been steadily declining in recent years, the intensification of human migration and illegal drug trafficking throughout the region, which are driving deforestation and land use changes, have the potential to reignite the resurgence of malaria in the region ^[241][370]. Currently, the La Mosquitia tropical forest region, located between Honduras and Nicaragua, is one of the most malaria endemic locations in Central America ^[99][229]. Although this region is part of the protected MBC, it continues to be threatened by illegal drug smuggling, cattle ranching, logging, and land grabbing ^{[22][261][262]}[22,38,50]. The recent increase in malaria cases in Panama, Costa Rica, and Nicaragua, especially of the more severe form, P. falciparum, raises concerns about the possibility of eradicating malaria in those countries in the next few years. This recent resurgence has been linked to imported cases from foreign migrants passing through the region ^[263][390]. While numerous findings highlight the effects of land use and micro and macro habitat changes have on of malaria vectors and disease risk across Central America, it is also evident that more research into these complex relationships and interactions is desperately needed. An improved understanding of anopheline vector ecologies will help inform on how malaria transmission dynamics might change over time and guide future malaria control and elimination activities in the region.

3.3. Impact on Tick-Borne Diseases

Studies in different areas of the world have demonstrated that deforestation practices and forest fragmentation could both decrease and modify biodiversity, which may lead to a greater abundance of fewer vertebrate species and an increased prevalence of their associated ticks that can thrive in modified habitats ^{[264][265][266][267][268][269][270]}[391,392,393,394,395,396,397]. In addition, some domestic animals, such as dogs and horses, may act as bridges for ticks and zoonotic pathogens from wildlife to humans, resulting in disease spillover events into urban environments ^{[271][272][273][274]}[398,399,400,401]. It is also important to consider environmental factors, such as temperature, precipitation and humidity, critical to host and tick survival, which could also change in modified environments. Each host, vector, and pathogen has its own requirements, which must be met to ensure their establishment and survival ^{[267][275][276][277][278][279]}[394,402,403,404,405,406].

Zoonotic pathogens may resurge depending on the conditions present, such as availability of humans and other domestic animals, tick vectors, and environmental conditions. When conditions are optimal and disease vectors and suitable vertebrate reservoir hosts become abundant, pathogen transmission risk may increase. Decreased contact between ticks and vertebrate hosts not relevant in pathogen transmission can also increase disease risk, which could cause a dilution effect. However, the mechanisms of this effect depend on scale and overall context, including local land use changes, climate/microclimate conditions, host communities, and their interactions ^[268][270][395,397]. Therefore, if humans encounter tick vectors in these deforested or disturbed areas, there may be a greater risk of zoonotic disease transmission.

In general, the scientific literature concerning tick-borne diseases in Central America focuses on the distribution or presence of tick species and their associations with vertebrate hosts and reports of human infections by specific pathogens (for examples see ^{[103][104][106][108][111][113][114][117][119][123][124][125][127][129][131][132][133][134][148][155][280][277][281][282][283][284][285][286][287]}[233,234,236,238,241,243,244,247,249,253,254,255,257,259,261,262,263,264,278,285,293,404,407,408,409,410,411,412,413]). However, very few studies in the region have focused on the influence of land use changes on pathogen and vector ecology. Except for recent studies in Panama ^{[278][288][289]}[405,414,415], no other published reports in the scientific literature have directly and specifically investigated the effects of forest modification, deforestation, or land use changes on tick species, or on pathogen transmission dynamics.

Among the few studies conducted in the region, one conducted in the Chiriquí province of Panama aimed to identify environmental predictors of tick burdens on dogs, as well as environmental predictors of pathogens in these ticks, including vegetation cover and land use change ^[278][405]. Although the most relevant predictor of tick prevalence and abundance was elevation, a decrease in vegetation cover linked to increased urbanization, was also associated with the highest tick prevalence and abundance. This is probably due to the close relationship of R. sanguineus s.l., the most common dog tick in the region, with human dwellings ^[278][405]. In areas with higher vegetation cover and less urbanization, other tick species became relevant, including A. ovale and I. c.f. boliviensis. Therefore, deforestation linked to increased urbanization appears to hinder survival and establishment of ticks, such as A. ovale and I. cf. boliviensis, while benefitting R. sanguineus s.l. ^[278][405]. In areas where R. sanguineus s.l. may act as a vector of zoonotic pathogens, decreases in forest cover and urbanization may increase transmission risk to humans.

Another study in Panama investigated tick diversity in a gradient of decreasing disturbance (low trees and shrubs, secondary forest, secondary forest crossed by a creek, and secondary–primary transition forests also crossed by a creek) and increasing forest cover along the 17 km Oleoducto trail in Soberania National Park ^[288][414]. Results showed that the most disturbed site had fewer tick–host interactions, compared with the other sites, and showed low tick diversity and few potential hosts ^[288][414]. Notably, this site included more A. mixtum ticks, which are common in diverse environments, including disturbed landscapes. Moreover, secondary and transition forests had a higher diversity of tick species and tick-host interactions, including a high abundance and diversity of birds and small mammals as well as several medium and large sized mammals that could serve as hosts for different tick species ^[288][414]. Therefore, this study suggests that a decrease in tick and host diversity may be a consequence of deforestation and forest disturbances in Central America. If these tick populations and their small mammal hosts are relevant in zoonotic transmission, deforestation in the region may also increase the risk for human infections due to diversity loss ^[268][270][395,397].

Additionally in Panama, a recent study investigated both vertebrate and tick communities in forest fragments, specifically in forested islands and peninsulas in the Barro Colorado Nature Monument, which were formed as a result of of damming the Chagres River about a century ago ^[289][415]. Its main findings indicate that tick species richness and abundance in this area increases according to the availability of vertebrate host species richness and wildlife biomass, which is higher in larger forest patches. In addition, tick species that have a broad range of vertebrate hosts as adults (e.g., generalists) increase in abundance when host diversity and specialist tick species is low ^[289][415]. Therefore, when human activities cause forest fragmentation, there is a decrease in wildlife biodiversity, while smaller sized tick hosts and generalist tick species may become more abundant. When these include possible reservoirs and vectors of pathogens, the risk of transmission between vertebrate species, including humans, can also increase ^[270][397].

Other studies in Panama have documented that most local species of ticks are host- specific as adults or at least they are associated with taxonomically related vertebrate species ^[290][416]. Therefore, a notable change in host diversity driven by deforestation and other land use changes could result in significant changes in local tick populations and disease transmission dynamics. For instance, the most common ticks on bovines in Central America are Rhipicephalus microplus (Canestrini, 1888) and Amblyomma mixtum (formerly cited as Boophilus microplus and A. cajennense, respectively), whereas horses are usually parasitized by Dermacentor nitens Neumann, 1897 (=Anocentor nitens) and A. mixtum ^{[101][104][129][275][277][282][291][292][293]}[231,234,259,402,404,408,417,418,419]. Depending on the specific area, other frequently found species include A. maculatum Koch, 1844, A. cf. oblongoguttatum Koch, 1844, and/or A. parvum Aragão, 1908, among others ^{[282][292][293]}[408,418,419]. Therefore, deforestation associated with cattle ranching may increase local populations of these ticks driven by changes in host abundance if other environmental conditions are suitable for ticks to complete their development. The case of A. mixtum is of particular interest since this species is considered a generalist biter frequently feeding on humans in areas of Central America ^{[146][294][277][281][284][285][295]}[276,297,404,407,410,411,420]. This tick species has been identified as a vector of R. rickettsii in Costa Rica and Panama ^{[107][277][285][296]}[237,404,411,421]. Moreover, there is molecular evidence of other pathogens detected in A. mixtum in Central America, including E. chaffeensis ^[107][237]. Amblyomma maculatum is the main vector of R. parkeri, which has been reported in Belize ^[287][297][413,422]. It is also relevant to note that there are additional reports of bovines and equines infected by A. phagocytophilum and detections of E. chaffeensis, E. ewingii, and/or A. phagocyophilum DNA in unidentified Amblyomma sp., D. nitens, and R. microplus collected from horses and cows in Guatemala and Panama ^[104][106][234,236]. Furthermore, R. microplus and D. nitens can also parasitize white tail deer (Odocoileus virginianus [Zimmermann, 1780]) in areas where they coexist with cattle and horses ^{[281][298][299]}[407,423,424]. In countries like Brazil, infection of R. rickettsii in humans has been associated with a shift from predominantly rural to a more urban transmission in Rio de Janeiro where ticks like D. nitens, R. microplus, and A. sculptum Berlese, 1888 are common on horses and cattle ^[271][398]. In this area, A. sculptum is also common on wild animals and it is considered a generalist biter and the most important vector of R. rickettsii. In Central America, an increase in the abundance of cattle, horses, and A. mixtum (and other generalist ticks) in areas where there is already local transmission of zoonotic pathogens may result in an increased risk of human exposure to these potential vectors and pathogen infection.

Rhipicephalus sanguineus s.l. is the most common tick on domestic dogs in Central America, although it is not indigenous to this region ^{[111][119][277][282][300][301][302]}[241,249,404,408,425,426,427]. Despite its marked preference toward dogs, this tick also bites humans and can do so frequently in rural and urban areas in Central America ^[294][295][297,420]. Considering that these ticks are usually found in urban environments or areas that have been disturbed, deforestation and other land use changes leading to human settlements and increased dog populations could result in the establishment of this species where it was not present before human activity, as it has been observed in Panama ^[278][405]. In addition to being the main vector of E. canis in the region, R. sanguineus s.l. may be implicated in the transmission of A. phagocytophilum, given reports of infection in dogs in Costa Rica and Nicaragua and the detection of its DNA in this tick species in Costa Rica and Panama ^{[109][119][125][127][277]}[239,249,255,257,404]. Moreover, R. sanguineus s.l. has been identified as responsible for urban outbreaks of severe human rickettsiosis by R. rickettsii in Mexico, and it may have been associated with a human case in Panama ^[147][303][277,428]. Considering the presence of these bacteria in Central America, an increase in dog populations in this region may facilitate contact with pathogen transmission cycles in wildlife and their ticks. In Rio de Janeiro, Brazil, recent investigations close to the Pedra Branca State Park have found R. rickettsii in R. sanguineus ticks as well as a higher exposure of dogs to Rickettsia spp. in recently urbanized areas, compared to rural and non-endemic areas ^[304][429]. This supports the hypothesis that interactions of dogs with wildlife and their ticks may eventually lead to the establishment of urban transmission cycles among dogs and R. sanguineus s.l. vectors and the possibility of a higher risk to humans mediated by contact with R. sanguineus s.l.

Amblyomma ovale is another tick species in Central America that can be found feeding on dogs in rural areas, urban periphery, and nearby human-disturbed forests areas or frequently accessed forest habitat (e.g., for hunting) ^{[111][124][277][281][282][285][300][301][305][306]}[241,254,404,407,408,411,425,426,430,431]. Although it is not frequently found in highly urbanized areas, this species readily bites humans in rural landscapes of Central America and it is the main vector of R. parkeri (strain Atlantic rainforest) in other parts of Latin America, including Colombia, Brazil, and Argentina ^{[294][277][295][297][306][307][308][309]}[297,404,420,422,431,432,433,434]. The presence of this strain of R. parkeri and R. africae in A. ovale has been recently reported in Belize and Nicaragua, respectively ^[124][286][254,412]. Moreover, several studies in the Americas, such as the U.S. and Brazil, have found that people who own or hunt with dogs that are in contact with wildlife and forest areas are more exposed to wildlife ticks, including vectors of zoonotic pathogens, that could also parasitize dogs ^[272][273][399,400]. Therefore, a consequence of increased human settlements in proximity to forest habitats and incursions into nearby forests, along with their domestic dogs for company, herding, hunting, and other activities, may increase human and dog exposure to A. ovale and other ticks and wildlife pathogens in disturbed and forest areas of Central America.

Land use changes leading to human settlements may also increase contact of humans with argasid ticks and the pathogens that they carry. Tick infestations in domestic environments and human bites by Ornithodoros spp. in Central America can occur due to bats, rodents, birds, or other small animals accessing the interior of buildings or seeking refuge close to buildings ^{[118][280][294][310][311][312]}[248,293,297,435,436,437]. In Panama, O. talaje and O. rudis were implicated as vectors of an unidentified Borrelia sp. that causes tick-borne relapsing fever in the area, but other common species (e.g., O. puertoricensis [Fox, 1947]) may also be competent vectors of Borrelia spp. ^[118][312][248,437]. In other regions of the world where cases of tick-borne relapsing fever occur, infection usually takes place within houses or buildings infested with argasid ticks ^[118][313][248,438]. In Central America, the expansion of human settlements, especially informal and unplanned housing, could offer adequate refuge for argasid ticks and small animals, such as rodents and bats, placing humans in close proximity to these ticks and increasing the risk for pathogen transmission.

There are other potential tick-borne pathogens in Central America that have been directly or indirectly documented in wild animals or ticks, but not in humans. For example, DNA of A. phagocytophilum and B. burgdorferi s.l. was recently detected in I. tapirus Kohls, 1956 and in I. cf. boliviensis, respectively, in Panama ^[133][263]. Although there is evidence of possible exposure to B. burgdorferi s.l. in dogs and humans in Central America, the bacterium involved has not been clearly identified ^{[127][135][140][314]}[257,265,270,439]. However, species such as I. c.f. boliviensis have the potential to transmit enzootic pathogens and may parasitize domestic animals, including dogs and even humans ^{[125][294][281][300][301][315]}[255,297,407,425,426,440]. This generalist feeding behavior may allow them to act as bridge vectors in peridomestic environments, especially near disturbed forests and rural settings near forests. The transmission cycles of A. phagocytophilum and B. burgdorferi s.s. typically involve wild animals, such as white tail deer and rodents, and tick populations that may increase in abundance due to forest disturbances, conservation measures, and reforestation practices ^{[264][266][269][316][317]}[391,393,396,441,442].