Modeling policy decisions to mitigate the risk of emerging arboviral diseases under ecological changes in Uganda: Proposing a one Health in all policies approach.

Background Aedes mosquito-borne arboviruses have (re-)emerged and caused considerable public health concerns in major sub-Saharan African cities subjected to rapid urbanisation. We assessed the effects of urbanisation on Aedes aegypti dynamics and biting pattern, and the risk of transmission of yellow fever (YF) and dengue (DEN) viruses along urban-rural gradient in Côte d'Ivoire. Methods We collected Aedes mosquitoes as eggs, larvae/pupae, and adults seasonally in urban, suburban and rural areas using ovitrap, larval survey and human-baited double net trap methods from January 2015 to December 2016. We sampled household data and characterised Aedes larval breeding sites. Ae. aegypti indices and biting rates were compared by area. Results Ae. aegypti was the most abundant species in all areas. It showed higher abundance in urban areas (n = 26,072; 99.4%). Larval indices were associated with human activities, including waste and water management. Tires and discarded containers were the most productive breeding sites in all areas. Household water receptacles displayed high Aedes-positive rate (23.6%) in urban areas. Positive ovitrap index was higher in urban (53.5%) compared to suburban (43.1%) and rural (29.7%). Stegomyia indices were highest in urban followed by suburban and rural areas, with respective house index of 67.2, 51.4 and 27.8, container index of 57.1, 43.5 and 19.7, and Breteau index of 95.2, 78.9 and 8.8. Biting rate was 4.3 and 2.7-fold higher in urban (83.5 bite/person/day) and suburban (52.1 bite/person/day) compared to rural (19.4 bite/person/day), respectively. Ae. aegypti indices were higher during rainy seasons. Conclusions In Côte d'Ivoire, urbanisation raised Ae. aegypti abundance and biting rate. As a result, YF and DEN risk indices were above WHO-established epidemic thresholds in urban area thus exposing local communities to high risk of getting diseases. Integrated community-based vector control programs should be applied to reduce arboviral risk. Key messages Urbanisation raises Aedes aegypti abundance and arboviral disease risk in Côte d’Ivoire. Integrated community clean-up actions are required to control Aedes vectors.

Seroprevalence of Trypanosoma cruzi infection and vector control activities in rural communities of the southern Gran Chaco (Argentina)

Background The city of Abidjan, Côte d’Ivoire has increasingly faced multiple outbreaks of Aedes mosquito-borne arboviral diseases (e.g., dengue (DEN) and yellow fever (YF)) during the recent years, 2017–2024. Thus, we assessed and compared Aedes aegypti larval and adult population dynamics and Stegomyia indices in four urbanized areas with differential arboviral incidences in Abidjan, Côte d’Ivoire. Methods From August 2019 to July 2020, we sampled Aedes mosquito immatures (larvae and pupae), adults and breeding habitats in Anono and Gbagba with high arboviral incidences and Ayakro and Entente with low arboviral incidences in the Abidjan city, using standardized methods. Sampling was conducted in the peridomestic and domestic (indoors and outdoors) premises during short dry season (SDS), short rainy season (SRS), long dry season (LDS) and long rainy season (LRS). The abdomens and ovaries of Ae. aegypti females were examined to determine their blood-meal and parity statuses. Stegomyia indices (container index: CI, house index: HI and Breteau index: BI), blood-meal status and parity rates were compared by study sites and seasons and with the World Health Organization (WHO)-established epidemic thresholds. Results Overall, Aedes and arboviral risk indices were high and similar between the four study areas. In total, 86,796 mosquitoes were identified and dominated by Ae. aegypti species (97.14%, 84,317/86,796). The most productive larval breeding habitats were tires, discarded containers and water storage containers. CI, HI, and BI in Anono (22.4%, 33.5% and 89.5), Ayakro (23.1%, 43.8% and 91.0), Entente (15.9%, 24.8% and 48.5) and Gbagba (23.3%, 43.0% and 102.0) were high in the respective study sites. Stegomyia indices were higher than the WHO-established epidemic thresholds during any seasons for DEN, and LRS and SRS for YF. The numbers of Ae. aegypti-positive breeding sites were higher in the domestic premises (68.0%, 900/1,324) than in the peridomestic premises (32.0%, 424/1,324). In the domestic premises, Ae. aegypti-positive breeding sites (94.6%, 851/4,360) and adult individuals (93.4%, 856/916) were mostly found outdoors of houses. Aedes aegypti adult females were mostly unfed (51.3%, 203/396), followed by blood-fed (22.2%, 88/396), gravid (13.9%, 55/396) and half-gravid (12.6%, 50/396), and had parity rate of 49.7% (197/396) that was comparable between the study sites. Conclusions The city of Abidjan, Côte d’Ivoire is highly infested with Ae. aegypti which showed comparable ecological patterns across study sites and seasons. Thus, the local communities are exposed to high and permanent risks of transmission of DEN and YF viruses that were above the WHO-established epidemic thresholds throughout. The results provide a baseline for future vector studies needed to further characterize the observed patterns of local Ae. aegypti abundances and behaviors, and risks of transmission of these arboviruses. Community-based larval source management of identified productive containers might reduce Ae. aegypti numbers and risks of transmission of Aedes-borne arboviruses in Abidjan, and other sub-Saharan African cities.

Since the introduction into North America in 1999 of West Nile virus (WNV) and its subsequent dramatic spread across the United States and Canada, human cases of WNV infection declined from their 2003 peak of 9,862 to only 712 cases and 43 fatalities confirmed in 2011 (http://www.cdc .gov/ncidod/dvbid/westnile/index.htm). The reasons for this decline remain unclear because avian amplification host and human herd immunity remains low in most regions and WNV continues to circulate in most areas of the United States. However, last year an unexpected resurgence in West Nile fever and encephalitis cases occurred; a total of 5,674 human cases was detected in the United States, with 286 deaths, making 2012 the deadliest year yet. The epidemic was focused in the central part of the United States, with Texas reporting 1,739 human infections and 89 deaths, or about 33% of the national total and more than three times the number of any other state. Within Texas, Dallas County was the epicenter, with 398 human infections and 20 deaths. The reasons for this dramatic resurgence in WNV infections are not clear; however, several factors could be involved ranging from increased enzootic bird-mosquito-bird circulation, resulting in more human spillover infections, to increased human virulence. In this issue, Duggal and others report complete genomic sequences of 17 WNV isolates from several regions of Texas and phylogenetic studies to determine if viral genetic changes might have been responsible for the resurgence in human cases. Two distinct WNV genotypes were identified, and both circulated in the Dallas and Houston regions where disease incidence differed markedly (about four times higher in Dallas). Importantly, no signs of adaptive evolution that could have resulted in more efficient infection of mosquitoes or birds were identified in any of the recent WNV strains. These results, along with epidemiological analyses, suggest that the 2012 resurgence in the Dallas area resulted from an increase in transmission by mosquitoes from birds to humans (spillover infections), rather than an increase in WNV neuroinvasiveness. Unusually high summer temperatures in the Dallas area, perhaps combined with ecological changes affecting mosquito or avian populations, probably played important roles in driving the 2012 outbreak. These critical findings presented by Duggal and others 1 and the magnitude of the 2012 West Nile encephalitis epidemic underscore the importance of a better understanding of how WNV, other arboviruses, and vector-borne diseases in general will respond to climate and anthropogenic ecological changes that now appear inevitable. Rising temperatures exert a wide variety of complex effects on mosquito survival, reproduction, and behavior. Because temperature also influences vector infection, dissemination, and transmission of arboviruses, often in unpredictable ways, we remain unable to anticipate the effects of global warming on arboviral disease. Droughts, which are predicted to increase in some regions of the United States and elsewhere, can also have dramatic impacts on mosquito populations, especially on West Nile mosquito vectors because of their affinity for standing, highly polluted water and to irrigated agricultural lands. Drought conditions can also concentrate avian amplifying hosts in wetter locations amenable to mosquito transmission of WNV. Thus, rigorous experimental and modeling studies are needed to improve the ability of our public health systems to anticipate and respond to the effects of climate change and its influences on vector-borne pathogens such as WNV.

Mosquito-borne diseases such as malaria, dengue, or chikungunya have been re-emerging all over the world, including in Europe. Managing resistance to public health pesticides in mosquitoes is essential and requires global, integrated, and coordinated actions and strong engagement of decision-makers, scientists, and public health operators. In this context, the present work aims at proposing an integrated plan of resistance surveillance in France and in the French Overseas territories in order to provide graduated and appropriate responses according to the situation. Briefly, the plan relies on periodic monitoring of insecticide resistance at the population level in predefined sites using adequate biological, molecular, and/or biochemical approaches and a stratification of the level of resistance risk at the scale of territory to adjust surveillance and vector control actions. The plan relies on the latest methods and indicators used for resistance monitoring as recommended by the World Health Organization in order to prevent or slow down its extension in space and time. The plan has been developed for France but can be easily adapted to other countries in order to provide a coordinated response to the growing problem of mosquito resistance in Europe.

Infections caused by viruses transmitted via blood-feeding arthropods (arthropod-borne or arboviruses) have gained considerable attention and importance during the last decades due to their resurgence, impact on public health, and changing epidemiologic features. The complex transmission cycles affected by environmental, technological, and ecological changes place arboviral infections in the realm of emerging and reemerging infections that intermittantly reappear in epidemic form or display tendency to extend beyond endemic zones. A number of previously undetected arboviral diseases have emerged in Turkey during the last decade, although, in some cases, serologic evidence has been provided earlier. Since Crimean-Congo hemorrhagic fever first emerged in Turkey in 2002, there are now more than 4400 laboratory-confirmed cases of the disease. In addition, convincing evidence has accumulated to suggest that pathogenic flaviviruses, including West Nile virus, are in circulation. Recent studies have also revealed human exposure, central nervous system infections, and outbreaks of febrile diseases by sandfly fever viruses. In this study, reports published in local and international journals on surveillance and epidemiology of medically important arboviruses and associated diseases from Turkey have been reviewed, and current data on tick, mosquito, and sandfly vectors are incorporated.

The microbe, the insect, man and others… : the world of vector-borne diseases. The transmission of pathogens by vector arthropods is an original, complex and efficient mean of propagation ; so, the sanitary and economic impact of such diseases appears considerable. Malaria is always a major endemic disease and other parasitic infections like leishmanioses, trypanosomoses or filarioses remain very prevalent in tropical countries. The incidence of Lyme borreliosis seems increasing and arboviral diseases like dengue, Chikungunya infection, Rift Valley fever, blue tongue and others are important concerns for those who are in charge of human or animal public health. Furthermore, the constant evolution of epidemiologic situations following ecologic changes often resulting of human activities is complicating the work of epidemiologists. We poorly understand the complexity of vectorial systems where arthropods can play many roles as they can be involved as vectors, reservoirs or disseminators and because their organism is a privileged site for the evolution of microorganisms. Facing the threat of vector-borne diseases, an efficient ecosanitary prevention is essential and this necessitates to carry on researches in several directions. In particular, we must study thoroughly the relationships between microorganisms and vectors, the ecology of arthropods, epidemiologic surveillance and vector control. That implies to have at our disposal well trained entomologists.

This paper develops an integrated strategy to model the urban development and ecological dynamics in the Central Puget Sound Region. This effort is part of the Puget Sound Regional Integrated Synthesis model (PRISM) – an interdisciplinary initiative at the University of Washington aiming to develop a dynamic and integrated understanding of the environmental and human systems in the Puget Sound. We describe a model that predicts the environmental stresses associated with urban development and related changes in land use and human activities under alternative demographic, economic, environmental, and policy scenarios. We build on UrbanSim, an existing urban simulation model developed by Waddell [42]. The principal urban actors, represented in the model as objects corresponding to businesses, households, developers, and governments, make choices about location of activities and land development. We extend the object properties and methods now implemented in the UrbanSim model to predict three types of human-induced environmental stressors: land conversion, resource use, and emissions. The core location model in UrbanSim will be revised from its current aggregate structure to one based on microsimulation, and from a zone description of space to one based on a high-resolution grid structure. We will use a spatially explicit process-based landscape modeling approach to replicate ecosystem processes and represent land use–cover interactions at the regional scale. The output of the urban ecological model will serve as the input to several biophysical models for hydrology, hillslope stability, water quality, atmosphere, and ecosystems. Ecological changes will feed back on the choices of both households and business locations, and availability of land and resources.

Farm-scale ecological and economic impacts of agricultural change in the uplands

Mosquito-borne viruses cause diseases of great public health concern. Arboviral disease case distributions have complex relationships with socioeconomic and environmental factors. We combined information about socio-economic (population, and poverty rate) and environmental (precipitation, and land use) characteristics with reported human cases of arboviral disease in the counties of Alabama, USA, from 2007–2017. We used county level data on West Nile virus (WNV), dengue virus (DENV), chikungunya virus (CHIKV), Zika virus (ZIKV), California serogroup virus, Eastern equine encephalitis virus, and Saint Louis encephalitis virus to provide a detailed description of their spatio-temporal pattern. We found a significant spatial convergence between incidence of WNV and poverty rate clustered in the southern part of Alabama. DENV, CHIKV and ZIKV cases showed a different spatial pattern, being mostly located in the northern part, in areas of high socioeconomic status. The results of our study establish that poverty-driven inequities in arboviral risk exist in the southern USA, and should be taken into account when planning prevention and intervention strategies.

During the last decades the disease vector Aedes albopictus (Asian tiger mosquito) has rapidly spread around the globe. Global shipment of goods contributes to its permanent introduction. Invaded regions are facing novel and serious public health concerns, especially regarding the transmission of formerly non-endemic arboviruses such as dengue and chikungunya. The further development and potential spread to other regions depends largely on their climatic suitability. Here, we have developed a tool for identifying and prioritizing European areas at risk for the establishment of Aedes albopictus by taking into account, for the first time, the freight imports from this mosquito’s endemic countries and the climate suitability at harbors and their surrounding regions. In a second step we consider the further transport of containers by train and inland waterways because these types of transport can be well controlled. We identify European regions at risk, where a huge amount of transported goods meet climatically suitable conditions for the disease vector. The current and future suitability of the climate for Aedes albopictus was modeled by a correlative niche model approach and the Regional Climate Model COSMO-CLM. This risk assessment combines impacts of globalization and global warming to improve effective and proactive interventions in disease vector surveillance and control actions.

We assessed the prevalence of infection with Trypanosoma cruzi, parasite genotypes (discrete typing units, DTUs), and the host-feeding sources of domestic and peridomestic Triatoma infestans Klug and Triatoma eratyrusiformis Del Ponte in eight rural communities of the subandean Calchaqui valleys in northwestern Argentina. We sought to analyze their epidemiological role in the context of routine vector surveillance and control actions. Infection with T. cruzi was determined by optic microscopy or polymerase chain reaction (PCR) amplification of the hypervariable region of kinetoplast DNA minicircles. Parasite genotypes were identified through a multi PCR-based strategy. Bloodmeal contents were tested with a direct ELISA assay against nine antisera. Human sleeping quarters (domiciles) and peridomestic dry-shrub fences concentrated most of the T. infestans and T. eratyrusiformis infected with T. cruzi, respectively. The most frequent host-feeding sources of T. infestans were chickens (73.1%) in peridomiciles and humans (73.3%) in domiciles, whereas T. eratyrusiformis fed more often on cavid rodents (92.6%), which thrived in the dry-shrub fences. The main T. cruzi DTU identified in both vectors was T. cruzi I (TcI). Triatoma eratyrusiformis was implicated in the local circulation of TcI among cavies and perhaps mice, but infection with other typically domestic DTUs (TcVI and TcII/TcV/TcVI) indicated overlap between (peri)domestic transmission cycles in both vector species. Because dry-shrub fences were not targeted for routine insecticide spraying, they may act as sources of (peri)domestic reinfestation. Triatoma eratyrusiformis is an emergent secondary vector of T. cruzi and plays a significant role in the local transmission of T. cruzi.

Peri-urban infestations with triatomine bugs, their sources and their dynamics have rarely been investigated. Here, we corroborated the reported occurrence of Triatoma infestans in a peri-urban area and in neighbouring rural houses in Pampa del Indio, in the Argentine Chaco, and identified its putative sources using spatial analysis and demographic questionnaires. Peri-urban householders reported that 10% of their premises had triatomines, whereas T. infestans was collected by timed manual searches or community-based surveillance in only nine (3%) houses. Trypanosoma cruzi-infected T. infestans and Triatoma sordida were collected indoors only in peri-urban houses and were infected with TcV and TcI, respectively. The triatomines fed on chickens, cats and humans. Peri-urban infestations were most frequent in a squatter settlement and particularly within the recently built mud houses of rural immigrants, with large-sized households, more dogs and cats and more crowding. Several of the observed infestations were most likely associated with passive bug transport from other sources and with active bug dispersal from neighbouring foci. Thus, the households in the squatter settlement were at a greater risk of bug invasion and colonisation. In sum, the incipient process of domestic colonisation and transmission, along with persistent rural-to-urban migratory flows and unplanned urbanisation, indicate the need for active vector surveillance and control actions at the peri-urban interface of the Gran Chaco.

The present study investigated the correlation between tourist demand and the incidence of dengue in Maceió, Alagoas, during the period 2007 to 2017, under the hypothesis that the flow of visitors aggravates the disease's dispersion in an endemic tropical context. Using Wavelet Coherence Analysis to identify patterns of local synchronization in time and frequency, the study aimed to isolate the effect of tourism, controlled by meteorological and climatic variables. The results obtained demonstrated low and inconsistent direct temporal coherence between tourist demand and the disease's incidence (both classic and hemorrhagic). It was concluded that the dynamics of dengue in Maceió are primarily driven by seasonal factors, and not by tourist demand, which implies concentrating vector surveillance and control actions based on climatic factors.

BackgroundsAedes albopictus (Diptera; Culicidae) is a highly invasive mosquito species and a competent vector of several arboviral diseases that have spread rapidly throughout the world. Prevalence and patterns of dispersal of the mosquito are of central importance for an effective control of the species. We used site-occupancy models accounting for false negative detections to estimate the prevalence, the turnover, the movement pattern and the growth rate in the number of sites occupied by the mosquito in 17 localities throughout Mallorca Island.ResultsSite-occupancy probability increased from 0.35 in the 2012, year of first reported observation of the species, to 0.89 in 2015. Despite a steady increase in mosquito presence, the extinction probability was generally high indicating a high turnover in the occupied sites. We considered two site-dependent covariates, namely the distance from the point of first observation and the estimated yearly occupancy rate in the neighborhood, as predicted by diffusion models. Results suggested that mosquito distribution during the first year was consistent with what predicted by simple diffusion models, but was not consistent with the diffusion model in subsequent years when it was similar to those expected from leapfrog dispersal events.ConclusionsAssuming a single initial colonization event, the spread of Ae. albopictus in Mallorca followed two distinct phases, an early one consistent with diffusion movements and a second consistent with long distance, ‘leapfrog’, movements. The colonization of the island was fast, with ~90% of the sites estimated to be occupied 3 years after the colonization. The fast spread was likely to have occurred through vectors related to human mobility such as cars or other vehicles. Surveillance and management actions near the introduction point would only be effective during the early steps of the colonization.