Transmission Of Vector-borne Pathogens Research Articles

Urbanization correlates with the prevalence and richness of blood parasites in Eurasian Blackbirds (Turdus merula)

Urbanization is increasing worldwide, producing severe environmental impacts. Biodiversity is affected by the expansion of cities, with many species being unable to cope with the different human-induced stressors present in these landscapes. However, this knowledge is mainly based on research from taxa such as plants or vertebrates, while other organisms like protozoa have been less studied in this context. The impact of urbanization on the transmission of vector-borne pathogens in wildlife is still unclear despite its relevance for animal and human health. Here, we investigated whether cities are associated with changes in the prevalence and richness of lineages of three vector-borne protozoans (Plasmodium, Haemoproteus and Leucocytozoon) in Eurasian blackbirds (Turdus merula) from multiple urban and forest areas in Europe. Our results show important species-specific differences between these two habitat types. We found a significant lower prevalence of Leucocytozoon in urban birds compared to forest birds, but no differences for Plasmodium and Haemoproteus. Furthermore, the richness of parasite lineages in European cities was higher for Plasmodium but lower for Leucocytozoon than in forests. We also found one Plasmodium lineage exclusively from cities while another of Leucocytozoon was only found in forests suggesting a certain level of habitat specialization for these protozoan vectors. Overall, our findings show that cities provide contrasting opportunities for the transmission of different vector-borne pathogens and generate new scenarios for the interactions between hosts, vectors and parasites.

Avian Plasmodium in invasive and native mosquitoes from southern Spain

BackgroundThe emergence of diseases of public health concern is enhanced by factors associated with global change, such as the introduction of invasive species. The Asian tiger mosquito (Aedes albopictus), considered a competent vector of different viruses and parasites, has been successfully introduced into Europe in recent decades. Molecular screening of parasites in mosquitoes (i.e. molecular xenomonitoring) is essential to understand the potential role of different native and invasive mosquito species in the local circulation of vector-borne parasites affecting both humans and wildlife.MethodsThe presence of avian Plasmodium parasites was molecularly tested in mosquitoes trapped in five localities with different environmental characteristics in southern Spain from May to November 2022. The species analyzed included the native Culex pipiens and Culiseta longiareolata and the invasive Ae. albopictus.ResultsAvian Plasmodium DNA was only found in Cx. pipiens with 31 positive out of 165 mosquito pools tested. None of the Ae. albopictus or Cs. longiareolata pools were positive for avian malaria parasites. Overall, eight Plasmodium lineages were identified, including a new lineage described here. No significant differences in parasite prevalence were found between localities or sampling sessions.ConclusionsUnlike the invasive Ae. albopictus, Cx. pipiens plays a key role in the transmission of avian Plasmodium in southern Spain. However, due to the recent establishment of Ae. albopictus in the area, further research on the role of this species in the local transmission of vector-borne pathogens with different reservoirs is required.Graphical

Thermal preference of Culicoides biting midges in laboratory and semi-field settings

Biting midges of the genus Culicoides (Diptera: Ceratopogonidae) are hematophagous insects, and some species can transmit a plethora of pathogens, e.g., bluetongue virus and African horse sickness virus, that mainly affect animals. The transmission of vector-borne pathogens is strongly temperature dependent, and recent studies pointed to the importance of including microclimatic data when modelling disease spread. However, little is known about the preferred temperature of biting midges. The present study addressed the thermal selection of field-caught Culicoides with two experiments. In a laboratory setup, sugar-fed or blood-fed midges were video tracked for 15 min while moving inside a 60 × 30 × 4 cm setup with a 15–25 °C temperature gradient. Culicoides spent over double the time in the coldest zone of the setup compared to the warmest one. This cold selection was significantly stronger for sugar-fed individuals. Calculated preferred temperatures were 18.3 °C and 18.9 °C for sugar-fed and blood-fed Culicoides, respectively. The effect of temperature on walking speed was significant but weak, indicating that their skewed distribution results from preference and not cold trapping. A second experiment consisted of a two-way-choice-setup, performed in a 90 × 45 × 45 cm net cage, placed outdoors in a sheltered environment. Two UV LED CDC traps were placed inside the setup, and a mean temperature difference of 2.2 °C was created between the two traps. Hundred-fifty Culicoides were released per experiment. Recapture rates were negatively correlated with ambient temperature and were on average three times higher in the cooled trap. The higher prevalence of biting midges in cooler environments influences fitness and ability to transmit pathogens and should be considered in models that predict Culicoides disease transmission.

Conceptual risk assessment of mosquito population modification gene-drive systems to control malaria transmission: preliminary hazards list workshops.

The field-testing and eventual adoption of genetically-engineered mosquitoes (GEMs) to control vector-borne pathogen transmission will require them meeting safety criteria specified by regulatory authorities in regions where the technology is being considered for use and other locales that might be impacted. Preliminary risk considerations by researchers and developers may be useful for planning the baseline data collection and field research used to address the anticipated safety concerns. Part of this process is to identify potential hazards (defined as the inherent ability of an entity to cause harm) and their harms, and then chart the pathways to harm and evaluate their probability as part of a risk assessment. The University of California Malaria Initiative (UCMI) participated in a series of workshops held to identify potential hazards specific to mosquito population modification strains carrying gene-drive systems coupled to anti-parasite effector genes and their use in a hypothetical island field trial. The hazards identified were placed within the broader context of previous efforts discussed in the scientific literature. Five risk areas were considered i) pathogens, infections and diseases, and the impacts of GEMs on human and animal health, ii) invasiveness and persistence of GEMs, and interactions of GEMs with target organisms, iii) interactions of GEMs with non-target organisms including horizontal gene transfer, iv) impacts of techniques used for the management of GEMs and v) evolutionary and stability considerations. A preliminary hazards list (PHL) was developed and is made available here. This PHL is useful for internal project risk evaluation and is available to regulators at prospective field sites. UCMI project scientists affirm that the subsequent processes associated with the comprehensive risk assessment for the application of this technology should be driven by the stakeholders at the proposed field site and areas that could be affected by this intervention strategy.

Species diversity and detection of pathogens in phlebotomine sand flies collected from forest management areas of Quintana Roo, Mexico.

Sand flies have expanded their areas of distribution, thereby increasing the risk of pathogen transmission in non-endemic areas. To establish efficient prevention and control strategies for the transmission of vector-borne pathogens, it is important to understand seasonal dynamics of their vectors. In Mexico, there are several areas where the contact between sand flies, hosts and reservoirs favours the transmission of the pathogen. We compared sand fly communities in a forest management area and a conserved area in Noh-Bec, Quintana Roo, Mexico. The analysis included species diversity, activity peaks and molecular detection of pathogens. Sand flies were collected from November to December 2021 and April to May 2022, during 84 night-traps. The conserved area showed higher numbers and greater species heterogeneity of sand flies as compared with the other sites. The β-diversity analysis revealed that sites disturbed by logging (S1, S2, S3) had greater similarity (90%) in their sand fly species composition than a conserved area (S4) (similarity = 36%). Although none of the specimens were infected with Leishmania, we detected Wolbachia (19.4%) in all four sites, as well as Bartonella (3.25%) only in the disturbed sites. Further studies on the dynamics of sand fly populations and their association with pathogens are necessary.

Survival of Salmonella Typhimurium in the hemolymph of the German cockroach vector is limited by both humoral immune factors and hemocytes but not by trehalose metabolism.

The German cockroach (Blattella germanica) has been linked to transmission of Salmonella enterica serovar Typhimurium (S. Typhimurium), but infection dynamics within this vector are poorly characterized. Our recent work has focused on S. Typhimurium infection in the cockroach gut. However, microbial dissemination to the hemolymph is an essential aspect of many vector-borne pathogen transmission cycles and could potentially contribute to S. Typhimurium colonization of cockroaches. Therefore, the goal of this study was to examine the ability of S. Typhimurium to disseminate, survive, and proliferate in the hemolymph of cockroaches after oral infection. We detected only low numbers of bacteria in the hemolymph of a minority of insects (~26%) after oral infection. Further, S. Typhimurium was unable to survive overnight in cell-free hemolymph. Several hypotheses to explain the inability of S. Typhimurium to colonize hemolymph were tested. First, we investigated the ability of S. Typhimurium to metabolize trehalose, the primary sugar in hemolymph. S. Typhimurium grew efficiently in vitro using trehalose as a sole carbon source and mutant strains lacking trehalose metabolism genes exhibited no growth deficiencies in media mimicking the composition of hemolymph, suggesting that trehalose metabolism ability is not a factor involved in restricting survival in hemolymph. On the other hand, heat-inactivated cell-free hemolymph was permissive of S. Typhimurium growth, demonstrating that survival in hemolymph is limited specifically by heat-labile humoral factors. The involvement of cellular immune responses was also investigated and cockroach hemocytes in culture were observed to internalize S. Typhimurium within 1 h of exposure. Most hemocytes harbored few to no bacteria after 24 h, indicating that hemocyte responses are additionally involved in clearing infection from the hemolymph. However, dense intracellular clusters of S. Typhimurium were observed sporadically, suggesting a small subset of hemocytes may serve as reservoirs for bacterial replication. Together, our results reveal that a minute proportion of ingested S. Typhimurium is able to escape the cockroach gut and enter the hemolymph, but this systemic population is limited by both humoral effectors and hemocytes. Thus, we conclude that invasion of the hemolymph appears minimally important for colonization of the cockroach vector and that colonization of the gut is the main driver of vector-borne transmission. Our insight into the antimicrobial mechanisms of cockroach hemolymph also highlights the strong ability of these prevalent pests/vectors to cope with frequent infectious challenges in septic habitats.

Integrating Community Ecology into Models of Vector-Borne Virus Transmission.

Vector-borne plant viruses are a diverse and dynamic threat to agriculture with hundreds of economically damaging viruses and insect vector species. Mathematical models have greatly increased our understanding of how alterations of vector life history and host-vector-pathogen interactions can affect virus transmission. However, insect vectors also interact with species such as predators and competitors in food webs, and these interactions affect vector population size and behaviors in ways that mediate virus transmission. Studies assessing how species' interactions affect vector-borne pathogen transmission are limited in both number and scale, hampering the development of models that appropriately capture community-level effects on virus prevalence. Here, we review vector traits and community factors that affect virus transmission, explore the existing models of vector-borne virus transmission and areas where the principles of community ecology could improve the models and management, and finally evaluate virus transmission in agricultural systems. We conclude that models have expanded our understanding of disease dynamics through simulations of transmission but are limited in their ability to reflect the complexity of ecological interactions in real systems. We also document a need for experiments in agroecosystems, where the high availability of historical and remote-sensing data could serve to validate and improve vector-borne virus transmission models.

Humidity - The overlooked variable in the thermal biology of mosquito-borne disease.

Vector-borne diseases cause significant financial and human loss, with billions of dollars spent on control. Arthropod vectors experience a complex suite of environmental factors that affect fitness, population growth and species interactions across multiple spatial and temporal scales. Temperature and water availability are two of the most important abiotic variables influencing their distributions and abundances. While extensive research on temperature exists, the influence of humidity on vector and pathogen parameters affecting disease dynamics are less understood. Humidity is often underemphasized, and when considered, is often treated as independent of temperature even though desiccation likely contributes to declines in trait performance at warmer temperatures. This Perspectives explores how humidity shapes the thermal performance of mosquito-borne pathogen transmission. We summarize what is known about its effects and propose a conceptual model for how temperature and humidity interact to shape the range of temperatures across which mosquitoes persist and achieve high transmission potential. We discuss how failing to account for these interactions hinders efforts to forecast transmission dynamics and respond to epidemics of mosquito-borne infections. We outline future research areas that will ground the effects of humidity on the thermal biology of pathogen transmission in a theoretical and empirical framework to improve spatial and temporal prediction of vector-borne pathogen transmission.

Association of endoplasmic reticulum associated degradation (ERAD) with the transmission of Liberibacter solanacearum by its psyllid vector.

Candidatus Liberibacter solanacearum (CLso) is a complex of gram negative plant pathogenic and fastidious bacterial haplotypes restricted to the phloem and transmitted by several psyllid species. In Israel, the carrot psyllid Bactericera trigonica transmits CLso haplotype D in a persistent and propagative manner and causes the carrot yellows disease, inflicting significant economic losses in many countries. Understanding the transmission of CLso is fundamental to devising sustainable management strategies. Persistent transmission of vector-borne pathogens involves the critical steps of adhesion, cell invasion and replication inside the insect gut cells before passage to the hemolymph. Using microscopy and expression analyses, we have previously confirmed a role for the endoplasmic reticulum (ER) in inducing immune responses and subsequent molecular pathways resulting in programmed cell death (apoptosis) upon CLso-infection in the midgut. In the current study, we confirm that the ER-associated degradation (ERAD) machinery and its associated marker genes were upregulated in CLso infected insects, including Derlin-1, Selenoprotein-1 and Ubiquitin Ligase RNF-185. Silencing Derlin-1, which acts on the ER membrane by regulating the degradation of unfolded proteins upon ER stress, revealed its role in CLso persistence and transmission. Molecular pathways initiated in the ER membrane upon bacterial infection are well documented in human, animal and insect systems, and this study confirms the role of the ER in CLso-psyllid interactions.

Ecological predictors of mosquito population and arbovirus transmission synchrony estimates.

Quantifying synchrony in species population fluctuations and determining its driving factors can inform multiple aspects of ecological and epidemiological research and policy decisions. We examined seasonal mosquito and arbovirus surveillance data collected in Connecticut, United States from 2001 to 2020 to quantify spatial relationships in 19 mosquito species and 7 arboviruses timeseries accounting for environmental factors such as climate and land cover characteristics. We determined that mosquito collections, on average, were significantly correlated up to 10 km though highly variable among the examined species. Few arboviruses displayed any synchrony and significant maximum correlated distances never exceeded 5 km. After accounting for distance, mixed effects models showed that mosquito or arbovirus identity explained more variance in synchrony estimates than climate or land cover factors. Correlated mosquito collections up to 10-20 km suggest that mosquito control operations for nuisance and disease vectors alike must expand treatment zones to regional scales for operations to have population-level impacts. Species identity matters as well, and some mosquito species will require much larger treatment zones than others. The much shorter correlated detection distances for arboviruses reinforce the notion that focal-level processes drive vector-borne pathogen transmission dynamics and risk of spillover into human populations.

Candidatus Neoehrlichia mikurensis and Hepatozoon sp. in voles (Microtus spp.): occurrence and evidence for vertical transmission

Candidatus Neoehrlichia mikurensis (CNM) and Hepatozoon spp. are important vector-borne parasites of humans and animals. CNM is a relatively recently discovered pathogen of humans. Hepatozoon are parasites of reptiles, amphibians and mammals, commonly found in rodents and carnivores worldwide. The present study aimed to determine the prevalence of CNM and Hepatozoon spp. in three species of Microtus and to assess the occurrence of vertical transmission in naturally-infected voles. Molecular techniques were used to detect pathogen DNA in blood and tissue samples of captured voles and their offspring. The prevalence of CNM in the vole community ranged 24–47% depending on Microtus species. The DNA of CNM was detected in 21% of pups from three litters of six infected Microtus dams (two Microtus arvalis and one M. oeconomus) and in 3/45 embryos (6.6%) from two litters of eight CNM-infected pregnant females. We detected Hepatozoon infection in 14% of M. arvalis and 9% of M. oeconomus voles. Hepatozoon sp. DNA was detected in 48.7% of pups from seven litters (6 M. arvalis and 1 M. oeconomus) and in two embryos (14.3%) obtained from one M. arvalis litter. The high prevalence of CNM infections in the Microtus spp. community may be a result of a relatively high rate of vertical transmission among naturally infected voles. Vertical transmission was also demonstrated for Hepatozoon sp. in M. arvalis and M. oeconomus. Our study underlines the significance of alternative routes of transmission of important vector-borne pathogens.

Field Evaluation of Novel Spatial Repellent Controlled Release Devices (CRDs) against Mosquitoes in an Outdoor Setting in the Northern Peruvian Amazon.

U.S. military troops are exposed to mosquito-borne pathogens when deployed to endemic regions. Personal protective measures such as permethrin-treated uniforms and dermal repellents are the cornerstones of mosquito-borne disease prevention for the U.S. military. These measures have limitations and additional personal protection tools, such as spatial repellent devices to decrease the risk of vector-borne pathogen transmission, are required. Novel spatial repellent controlled-release devices formulated with metofluthrin were evaluated in an outdoor setting in the northern Amazon of Peru to evaluate performance under field conditions. The metofluthrin emitting devices lowered the number of mosquitoes captured in protected human landing collections (HLC) compared to blank devices, although there were effect differences between Anopheles spp. and species in other mosquito genera. A computational-experimental model was developed to correlate HLC and active ingredient (AI) concentrations as a function of time and space. Results show a strong correlation between the released AI and the decrease in HLC. This model represents the first effort to obtain a predictive analytical tool on device performance using HLC as the entomological endpoint.

Patterns and Ecological Mechanisms of Tick-Borne Disease Exposure Risk in Acadia National Park, Mount Desert Island, Maine, United States.

National parks are unique and significant vector-borne pathogen transmission settings, engaging over 300 million people in outdoor recreation per year. In this study, we integrated vector surveys and ecological habitat feature data in spatial models to characterize tick-borne disease exposure risk in Acadia National Park (ANP), Maine. To determine the broad-scale patterns of blacklegged tick Ixodes scapularis Say (Acari: Ixodidae) densities in ANP, we conducted host-seeking tick collections at 114 sites across the park over two years. Using these tick survey data and geospatial landscape feature data (i.e., land cover, elevation, forest patch size, and aspect) we developed a random forest model of nymphal tick density. We found that host-seeking tick density varies significantly across the park and is particularly high in areas characterized by deciduous forest cover and relatively low elevation. To explore potential fine-scale ecological drivers of tick density spatial patterns, we quantified microclimate conditions, host activity, and vegetation characteristics at a subset of 19 sites. We identified significant differences in microclimate conditions but not host activity or vegetation metrics across broad-scale landscape feature classes. Mean temperature and mean humidity were correlated to nymphal densities and therefore may provide a mechanistic link between landscape features and blacklegged tick densities. Finally, we detected multiple tick-borne pathogens in both ticks and small mammals sampled in ANP, including Borrelia burgdorferi, Babesia microti, and Anaplasma phagocytophilum. Our findings demonstrate the value of using ecological metrics to estimate vector-borne disease exposure risk and provide insight into habitat characteristics that may drive tick-borne disease exposure risk.

Environmental factors driving fine-scale ixodid tick abundance patterns

Tick abundance is an essential demographic parameter to infer tick-borne pathogen transmission risks. Spatiotemporal patterns of tick abundance are heterogeneous, so its determinants at small spatial scales need to be understood to reduce their negative effects on hosts. Current knowledge of these determinants is scarce, especially in Mediterranean environments, limiting the possibilities for designing efficient tick control strategies. With the goal of unravelling tick abundance determinants and informing new tick management strategies, we estimated tick burdens on 1965 wild ungulates in Doñana National Park, Spain, annually between 2010 and 2020. Under the hypothesis of a predominant host influence on tick abundance, we modelled the burdens of Rhipicephalus annulatus, Hyalomma lusitanicum, and Ixodes ricinus with relevant predictors grouped into four factors: i) environment; ii) host population; iii) host individual; and iv) land-use. Generalized linear mixed models with a zero-inflated negative binomial distribution were built. Additionally, we analysed the differential contribution to abundance of each factor by deviance partitioning. We finally estimated the similarity in the environmental space of tick species by analysing their niche overlap with the environmental principal component analysis method. Our work hypothesis was confirmed for R. annulatus and H. lusitanicum, but we found that tick abundance at a fine spatial scale is jointly driven by multiple drivers, including all four factors considered in this study. This result points out that understanding the demography of ticks is a complex multifactorial issue, even at small spatial scales. We found no niche differences between the three tick species at the study spatial scale, thus showing similar host and environmental dependencies. Overall results identify that host aggregation areas displaying environmentally favourable traits for ticks are relevant tick and vector-borne pathogen transmission hotspots. Our findings will facilitate the design of new strategies to reduce the negative effects of tick parasitism.

Predators affect a plant virus through density and trait-mediated indirect effects on vectors

Biological control programs frequently rely on insect predators to control pests that vector plant pathogens in agroecosystems. Predators affect vectors by eating them (consumptive effects) and by inducing antipredator behaviors (non-consumptive effects), and these interactions may affect transmission of vector-borne pathogens. However, it has proven difficult to experimentally tease apart the effects of predators on vector fitness and behavior as they are often correlated. We addressed this problem by assessing how both aphids and an aphid-borne pathogen were affected by variable predation risk. Specifically, we experimentally manipulated ladybeetle predators' mouthparts to isolate consumptive, and non-consumptive, effects of predators on aphid fitness, movement, and virus transmission. We show that although lethal predators decreased aphid vector abundance, they increased pathogen transmission by increasing aphid movement among hosts. Moreover, aphids responded to risk of predation by moving to younger plant tissue that was more susceptible to the pathogen. Aphids also responded to predator risk through compensatory reproduction, which offset direct consumptive effects. Our results support predictions of disease models showing alterations of vector movement due to predators can have greater effects on transmission of pathogens than vector consumption, which should be considered when examining natural enemies' role in pathogen dynamics. Broadly, our study shows isolating direct and indirect predation effects can reveal novel pathways by which predators affect vector-borne pathogens.

The new invasive mosquito species Aedes koreicus as vector-borne diseases in the European area, a focus on Italian region: What we know from the scientific literature.

The increased mobility of goods, people, and animals worldwide has caused the spread of several arthropod vectors, leading to an increased risk of animal and human infections. Aedes koreicus is a common species in South Korea, China, Japan, and Russia. Due to its cold-resistant dormant eggs, the adults last from the late summer until the autumn seasons. For these reasons, it seems to be better adapted to colder temperatures, favoring its colonization of hilly and pre-alpine areas. Its first appearance in Europe was in 2008 in Belgium, where it is currently established. The species was subsequently detected in Italy in 2011, European Russia, Germany, the Swiss–Italian border region, Hungary, Slovenia, Crimea, Austria, the Republic of Kazakhstan, and the Netherlands. The role of A. koreicus in the transmission of vector-borne pathogens remains unclear. The available scientific evidence is very old, often not available in English or not indexed in international databases, and therefore difficult to find. According to the literature reviewed, A. koreicus can be considered a new invasive mosquito species in Europe, establishing populations on the European continent. In addition, experimental evidence demonstrated its vector competence for both Dirofilaria immitis and Chikungunya and is relatively low for ZIKA but not for Western Nile Virus. On the other hand, even if the field evidence does not confirm the experimental findings, it is currently not possible to exclude with absolute certainty the potential involvement of this species in the spread, emergence, or re-emergence of these vector-borne disease agents.

Extracellular Vesicles and Immunomodulation in Mosquitoes and Ticks

Extracellular vesicles are small blebs that are secreted by cells, which are lipid-rich and contain proteomic and genomic material (including small RNAs, mRNA, and plasmid DNA). These materials are delivered into recipient cells leading to a phenotypic change. Recent studies have demonstrated the secretion of extracellular vesicles by mosquito and tick cells, as well as tick salivary glands. Further, these studies suggest vesicles play a role in the transmission of vector-borne pathogens, including viruses and bacteria, and are involved in the manipulation of wound healing and immune responses. Both of these processes are key in the host response to hematophagous arthropods’ feeding. The role of mosquito and tick EVs in the modulation of immune responses and pathogen transmission is discussed in this entry.

Mathematical modelling to assess the feasibility of Wolbachia in malaria vector biocontrol

Releasing mosquitoes transinfected with the endosymbiotic bacterium Wolbachia is a novel strategy for interrupting vector-borne pathogen transmission. Following its success in controlling arboviruses spread by Aedes aegypti, this technology is being adapted for anopheline malaria vectors. However, antagonistic interactions between Wolbachia and naturally resident Asaia bacteria in malaria vectors have been demonstrated experimentally, potentially jeopardising Wolbachia biocontrol. We developed the first mathematical model accounting for interspecific competition between endosymbionts to assess the feasibility of this novel strategy for controlling malaria. First, Asaia prevalences among natural mosquito populations were compared with simulations parametrized with rates of Asaia transmission reported from laboratory studies. Discrepancies between projections and natural Asaia prevalences indicated potential overestimation of Asaia transmissibility in artificial laboratory settings. With parametrization that matches natural Asaia prevalence, simulations identified redundancies in Asaia’s many infection routes (vertical, sexual and environmental). This resilience was only overcome when Wolbachia conferred very high resistance to environmental infection with Asaia, resulting in Wolbachia fixation and Asaia exclusion. Wolbachia’s simulated spread was prevented when its maternal transmission was impeded in coinfected mosquitoes and the pre-control Asaia prevalence was beyond a threshold of 60–75%. This theoretical assessment highlights critical next steps in laboratory experiments to inform this strategy’s feasibility.

Current knowledge of vector-borne zoonotic pathogens in Zambia: A clarion call to scaling-up "One Health" research in the wake of emerging and re-emerging infectious diseases.

Although vector-borne zoonotic diseases are a major public health threat globally, they are usually neglected, especially among resource-constrained countries, including those in sub-Saharan Africa. This scoping review examined the current knowledge and identified research gaps of vector-borne zoonotic pathogens in Zambia. Major scientific databases (Web of Science, PubMed, Scopus, Google Scholar, CABI, Scientific Information Database (SID)) were searched for articles describing vector-borne (mosquitoes, ticks, fleas and tsetse flies) zoonotic pathogens in Zambia. Several mosquito-borne arboviruses have been reported including Yellow fever, Ntaya, Mayaro, Dengue, Zika, West Nile, Chikungunya, Sindbis, and Rift Valley fever viruses. Flea-borne zoonotic pathogens reported include Yersinia pestis and Rickettsia felis. Trypanosoma sp. was the only tsetse fly-borne pathogen identified. Further, tick-borne zoonotic pathogens reported included Crimean-Congo Haemorrhagic fever virus, Rickettsia sp., Anaplasma sp., Ehrlichia sp., Borrelia sp., and Coxiella burnetii. This study revealed the presence of many vector-borne zoonotic pathogens circulating in vectors and animals in Zambia. Though reports of human clinical cases were limited, several serological studies provided considerable evidence of zoonotic transmission of vector-borne pathogens in humans. However, the disease burden in humans attributable to vector-borne zoonotic infections could not be ascertained from the available reports and this precludes the formulation of national policies that could help in the control and mitigation of the impact of these diseases in Zambia. Therefore, there is an urgent need to scale-up "One Health" research in emerging and re-emerging infectious diseases to enable the country to prepare for future epidemics, including pandemics.

Patterns of deer ked (Diptera: Hippoboscidae) and tick (Ixodida: Ixodidae) infestation on white-tailed deer (Odocoileus virginianus) in the eastern United States

BackgroundWhite-tailed deer (Odocoileus virginianus) host numerous ectoparasitic species in the eastern USA, most notably various species of ticks and two species of deer keds. Several pathogens transmitted by ticks to humans and other animal hosts have also been found in deer keds. Little is known about the acquisition and potential for transmission of these pathogens by deer keds; however, tick-deer ked co-feeding transmission is one possible scenario. On-host localization of ticks and deer keds on white-tailed deer was evaluated across several geographical regions of the eastern US to define tick-deer ked spatial relationships on host deer, which may impact the vector-borne disease ecology of these ectoparasites.MethodsTicks and deer keds were collected from hunter-harvested white-tailed deer from six states in the eastern US. Each deer was divided into three body sections, and each section was checked for 4 person-minutes. Differences in ectoparasite counts across body sections and/or states were evaluated using a Bayesian generalized mixed model.ResultsA total of 168 white-tailed deer were inspected for ticks and deer keds across the study sites. Ticks (n = 1636) were collected from all surveyed states, with Ixodes scapularis (n = 1427) being the predominant species. Counts of I. scapularis from the head and front sections were greater than from the rear section. Neotropical deer keds (Lipoptena mazamae) from Alabama and Tennessee (n = 247) were more often found on the rear body section. European deer keds from Pennsylvania (all Lipoptena cervi, n = 314) were found on all body sections of deer.ConclusionsThe distributions of ticks and deer keds on white-tailed deer were significantly different from each other, providing the first evidence of possible on-host niche partitioning of ticks and two geographically distinct deer ked species (L. cervi in the northeast and L. mazamae in the southeast). These differences in spatial distributions may have implications for acquisition and/or transmission of vector-borne pathogens and therefore warrant further study over a wider geographic range and longer time frame.Graphical