The Constant Threat of Zoonotic and Vector-Borne Emerging Tropical Diseases: Living on the Edge

Abstract

Emerging diseases have significantly impacted the last few decades (1–10). The emergence and re-emergence of vector-borne and zoonotic diseases in Africa, Asia, and Latin America have reshaped the epidemiological landscape of these continents. The impact of these diseases and the establishment of local transmission in traditionally non-endemic areas, due to migration and travel, have been revealed over the last years. Diseases such as Chikungunya (11–16), Zika (17–24), Yellow Fever (25–28), Dengue (29–33), Oropouche, Madre de Dios virus, Iquitos virus (34, 35), Mayaro Fever (36, 37), Ebola (38–42), Nipah virus, arenaviruses such as Lassa (43), Machupo (44, 45), Chapare (45, 46), Junin (47), zoonotic Malaria (48), Severe Fever with Thrombocytopenia Syndrome (49), Plague (50), Crimean-Congo Hemorrhagic Fever, Acute Orally Transmitted Chagas Disease (51–54), Visceral and Diffuse Cutaneous Leishmaniasis (55, 56), Toxoplasmosis (57–59), Tick-Borne Diseases (60, 61), Rift Valley Fever, Tuberculosis (62), Leprosy (63–67), Avian Influenza (68–70), Orthohantavirus (71–75), and Toxocariasis (76, 77) have posed a significant impact to human health. Furthermore, zoonotic epidemics and pandemic coronaviruses, such as the Severe Acute Respiratory Syndrome (SARS), the Middle East Respiratory Syndrome (MERS) (78–82), and the ongoing SARS-CoV-2/COVID-19 (83, 84) pandemic, have caused a profound economical and social disruption threatening to overwhelm public health systems globally (85) (Table 1). Most of these pathogens can even cocirculate and coinfect a significant proportion of inhabitants within the same territories (11, 87–94). For example, in arboviral diseases, the occurrence of coinfections has been widely reported –such as Dengue with Chikungunya and/or with Zika virus– and affects diverse populations, including pregnant women and immunocompromised patients (94–97). This may obscure clinical suspicion, as signs and symptoms for many of these pathogens may overlap. In endemic areas, this becomes a particularly pressing issue that must be taken into account in order to ensure accurate diagnosis and provide appropriate management. The ChikDenMaZika syndrome has been previously adopted as a mnemonic device to include Chikungunya, Dengue, Mayaro, and Zika in the broad differential of acute febrile illnesses due to arboviral agents (95). More recently, emerging coinfections, including bacterial and parasitic diseases, such as tuberculosis and Chagas disease, have also been reported (98). Table 1 Lessons learned from the COVID-19 pandemic in Latin America. Current times call for more comprehensive ecoepidemiological and bioecosocial approaches (20, 99). Scarce funding and the lack of research (39, 43, 61, 81) in tropical medicine are entirely unacceptable. Human immunodeficiency virus (HIV)/acquired immune deficiency syndrome (AIDS), tuberculosis (TB), and malaria combined receive approximately 70% of neglected diseases funding. As mentioned here, emerging tropical diseases, such as those mentioned here, are worldwide in scope, and many have significant regional implications. Therefore, a different funding paradigm that improves their situation is needed (100). The world is no longer a place with distant countries and shielded territories. Instead, ever increasing interconnectivity has turned it into a “small” global village, where the health status of underprivileged areas may undermine not only their lives and development but extend to the wealthiest. The Ebola crisis in 2014 highlighted how high-consequence emerging diseases could spill over to Europe and North America (38, 40). The ongoing 2020-2021 pandemic of COVID-19, which has reached as far as Antarctica, affecting almost all countries worldwide, is another clear example (8, 29, 84, 101–112). As was expected, coinfections between tropical pathogens and COVID-19 are also now increasingly being reported, especially with dengue (30). Dengue affects over 100 countries worldwide and puts about 2.5-3.9 billion people at risk of infection (113, 114). Within the next century, nearly a billion people are at risk of exposure to virus transmission by both main Aedes spp., Ae. aegypti, and Ae. albopictus (also Chikungunya and Zika) in the worst-case scenario (115). The recent first detection of Ae. vittatus in the Dominican Republic and the Americas generated concern in the region, requiring enhanced surveillance to understand the range and public health risks of this potential invasive mosquito species, deserving more studies (116). Most of these emerging tropical diseases are vector-borne, zoonotically transmitted, or environmentally spread through direct contact, food or water ingestion, as well as a consequence of environmental alterations (including the effects of climate change) (117–125), becoming significant sources of mortality and morbidity worldwide (2). The impact of these diseases extends well beyond the acute constellation of symptoms, leading in a considerable proportion of patients to chronic sequelae and complications, which can be long lasting and severely incapacitating, as is the case with Chikungunya (15, 126–132), Zika (17, 133–135), Ebola, Chagas disease (52), and even for COVID-19 (136–139). Many tools have been deployed to counteract emerging infectious diseases. Amongst these are active surveillance (some supported by artificial intelligence) (140–142), leading to the rapid identification of novel pathogens by genome sequencing and phylogenetic tracing studies (36, 105, 107, 143–146) based on computing methods to predict possible interspecies barriers spillover between humans and animals (147). Coupling biotechnological approaches with social sciences—the holistic understanding of humans and their...