Zoonotic Pathogen Seroprevalence in Cattle in a Wildlife–Livestock Interface, Kenya Abstract A cross-sectional study was conducted to determine the seroprevalence of Brucella spp. and Leptospira spp. and risk factors of exposure in cattle in three zones with varying land use types and wildlife–livestock interactions. Five villages were selected purposively; two in areas with intensive livestock–wildlife interactions (zone 1), another two in areas with moderate livestock–wildlife interactions (zone 2) and one in areas where wildlife–livestock interactions are rarer (zone 3). Sera samples were collected from 1170 cattle belonging to 390 herds in all the zones and tested for antibodies against Brucella abortus and Leptospira interrogans serovar hardjo using ELISA kits. Data on putative risk factors for seropositivity of these pathogens in cattle were collected using a questionnaire. The overall apparent animal-level seroprevalence of brucellosis and leptospirosis was, respectively, 36.9% (95% CI 34.1–39.8) and 23.5% (95% CI 21.1–26.0). Brucella spp. seroprevalence was higher in zone 1 than in zones 2 and 3 (χ2 = 25.1, df = 2, P < 0.001). Zones 1 and 2 had significantly higher Leptospira spp. seroprevalence than zone 3 (χ2 = 7.0, df = 2, P = 0.029). Results of multivariable analyses identified animal sex (female) and zones (high interface area) as significant predictors (P < 0.05) of animal-level seropositivity of Brucella spp. For Leptospira spp., important predictors of animal-level seropositivity were animal sex (female), zones (moderate interface area) and herds utilizing a communal grazing reserve. The seroprevalences of Brucella spp. and Leptospira spp. in cattle were higher in areas with moderate to high wildlife–livestock interactions than those with rare interactions.

Occupational Animal Contact in Southern and Central Vietnam Abstract Despite the global zoonotic disease burden, the underlying exposures that drive zoonotic disease emergence are not understood. Here, we aimed to assess exposures to potential sources of zoonotic disease and investigate the demographics, attitudes, and behavior of individuals with sustained occupational animal contact in Vietnam. We recruited 581 animal workers (animal-raising farmers, slaughterers, animal health workers, and rat traders) and their families in southern and central Vietnam into a cohort. Cohort members were followed for 3 years and interviewed annually regarding (1) demography and attitudes regarding zoonotic disease, (2) medical history, (3) specific exposures to potential zoonotic infection sources, and (4) socioeconomic status. Interview information over the 3 years was combined and analyzed as cross-sectional data. Of the 297 cohort members interviewed, the majority (79.8%; 237/297) reported raising livestock; almost all (99.6%; 236/237) reported being routinely exposed to domestic animals, and more than a quarter (28.7%; 68/237) were exposed to exotic animals. Overall, 70% (208/297) reported slaughtering exotic animals; almost all (99.5%; 207/208) reported consuming such animals. The consumption of raw blood and meat was common (24.6%; 73/297 and 37%; 110/297, respectively). Over half (58.6%; 174/297) reported recent occupational animal-induced injuries that caused bleeding; the use of personal protective equipment (PPE) was limited. Our work demonstrates that individuals working with animals in Vietnam are exposed to a wide range of species, and there are limited procedures for reducing potential zoonotic disease exposures. We advocate better education, improved animal security, and enforced legislation of PPE for those with occupational animal exposure in Vietnam.

Mercury in Populations of River Dolphins of the Amazon and Orinoco Basins Abstract In the Amazon and Orinoco basins, mercury has been released from artisanal and industrial gold mining since the Colonial time, as well as a result of deforestation and burning of primary forest, that release natural deposits of methyl mercury, affecting the local aquatic vertebrate fauna. This study reports the presence of mercury in river dolphins’ genera Inia and Sotalia. Mercury concentrations were analysed in muscle tissue samples collected from 46 individuals at the Arauca and Orinoco Rivers (Colombia), the Amazon River (Colombia), a tributary of the Itenez River (Bolivia) and from the Tapajos River (Brazil). Ranges of total mercury (Hg) concentration in muscle tissue of the four different taxa sampled were: I. geoffrensis humboldtiana 0.003–3.99 mg kg−1 ww (n = 21, Me = 0.4), I. g. geoffrensis 0.1–2.6 mg kg−1 ww (n = 15, Me = 0.55), I. boliviensis 0.03–0.4 mg kg−1 ww (n = 8, Me = 0.1) and S. fluviatilis 0.1–0.87 mg kg−1 ww (n = 2, Me = 0.5). The highest Hg concentration in our study was obtained at the Orinoco basin, recorded from a juvenile male of I. g. humboldtiana (3.99 mg kg−1 ww). At the Amazon basin, higher concentrations of mercury were recorded in the Tapajos River (Brazil) from an adult male of I. g. geoffrensis (2.6 mg kg−1 ww) and the Amazon River from an adult female of S. fluviatilis (0.87 mg kg−1 ww). Our data support the presence of total Hg in river dolphins distributed across the evaluated basins, evidencing the role of these cetaceans as sentinel species and bioindicators of the presence of this heavy metal in natural aquatic environments.

Incorporating Health Outcomes into Land-Use Planning Abstract The global trend toward increased agricultural production puts pressure on undeveloped areas, raising the question of how to optimally allocate land. Land-use change has recently been linked to a number of human health outcomes, but these are not routinely considered in land-use decision making. We review examples of planners’ currently used strategies to evaluate land use and present a conceptual model of optimal land use that incorporates health outcomes. We then present a framework for evaluating the health outcomes of land-use scenarios that can be used by decision makers in an integrated approach to land-use planning.

Detection of Leptospira spp. in Captive Broad-Snouted Caiman ( Caiman latirostris) Abstract Leptospira sp. is an important waterborne zoonotic bacterium, known to cause infection in animals and humans worldwide. The role of reptiles in the transmission of this microorganism is poorly understood and historically neglected. This study aimed to investigate the presence of anti-Leptospira spp. antibodies and leptospiral DNA in captive Caiman latirostris (broad-snouted caiman). Of the 23 reptiles studied by microscopic agglutination test (MAT), 22/23 (95.65%) were considered reactive (titers ≥ 100) and 1/23 (4.35%) non-reactive (titer < 100). The serogroup with highest occurrence was Grippotyphosa (68.18%, n = 15/22) followed by serogroup Djasiman (18.18%, n = 4/22). Specific amplification of Leptospira spp. gene lipL32 was observed in six (26.09%, n = 6/23) blood samples. Five of six samples, previously detected as pathogenic leptospira by PCR, were amplified and sequenced. All the samples corresponded to the pathogenic species Leptospira interrogans (presented 100% of identity) using the PCR targeting to secY gene. We demonstrated high detection of DNA of L. interrogans in crocodilians, and the authors suggest that further research is needed to elucidate the impact of Leptospira spp. infection in health broad-snouted caimans as well as the pathophysiology of leptospirosis in crocodilians.

Insights into the Host Specificity of Mosquito-Borne Flaviviruses Infecting Wild Mammals Abstract Mosquito-borne flaviviruses (MBFVs) are of public and animal health concern because they cause millions of human deaths annually and impact domestic animals and wildlife globally. MBFVs are phylogenetically divided into two clades, one is transmitted by Aedes mosquitoes (Ae-MBFVs) associated with mammals and the other by Culex mosquitoes (Cx-MBFVs) associated with birds. However, this assumption has not been evaluated. Here, we synthesized 79 published reports of MBFVs from wild mammals, estimating their host. Then, we tested whether the host specificity was biased to sampling and investigation efforts or to phylogenetic relationships using a viral phylogenetic tree drawn from analyzing whole flavivirus genomes obtained in GenBank. We found in total 18 flaviviruses, nine related to Aedes spp. and nine to Culex spp. infecting 129 mammal species. Thus, this supports that vectors are transmitting MBFV across available host clades and that ornithophilic mosquitoes are readily infecting mammals. Although most of the mosquito species are generalists in their host-feeding preferences, we also found a certain degree of MBFV’s specificity, as most of them infect closely related mammal species. The present study integrates knowledge regarding MBFVs, and it may help to understand their transmission dynamics between viruses, vectors, and mammal hosts.

Exotic Pinus radiata Plantations do not Increase Andes Hantavirus Prevalence in Rodents Abstract Andes south virus (ANDV) is the etiologic agent of hantavirus cardiopulmonary syndrome (HCPS) in Chile and southern Argentina. Farm and forestry workers have been identified as a group at high risk of acquiring HCPS caused by ANDV due to their close exposure to rodents or their secretions in rural areas. Therefore, investigation on the effect of landscape composition on ANDV in wild rodents becomes relevant for disease prevention and control. In this study, we analyzed the influence of Monterey pine (Pinus radiata) plantations, an important monoculture in the global forest industry, on small mammal assemblage and on ANDV seroprevalence and abundance of seropositive rodents from central Chile. Small mammals were sampled seasonally during 2 years in native forests, adult pine plantations and young pine plantations. A total of 1630 samples from seven rodent species were analyzed for antibody detection. ANDV seroprevalence and abundance of seropositive rodents were significantly higher in the native forest compared to pine plantations. Furthermore, Monterey pine plantations decrease the abundance and relative abundance of Oligoryzomys longicaudatus (the principal reservoir of ANDV) and do not change sex ratio and distribution of age classes of this rodent species, which are variables that are important for ANDV transmission. Our findings indicate that Monterey pine plantations would not pose a higher risk of human exposure to ANDV compared to the temperate native forest. Our results can be useful for hantavirus risks assessment in human-dominated areas where ANDV is endemic.

Population-Level Resistance to Chytridiomycosis is Life-Stage Dependent in an Imperiled Anuran Abstract Amphibian declines caused by chytridiomycosis have been severe, but some susceptible populations have persisted or even recovered. Resistance to the causal agent Batrachochytrium dendrobatidis (Bd) could result from alleles of the adaptive immune system. During metamorphosis, however, immune systems may not be fully functional, implying that an effective immune response to Bd may be life-stage dependent. We evaluated the susceptibility of the relict leopard frog (Rana onca) sourced from two areas where Bd was present or absent, and where the populations appeared to show differences in pathogen resistance. We evaluated whether population-level resistance manifested across life stages using challenge experiments with late-stage tadpoles (Gosner stage 31–38), metamorphs (stage 45–46), and juvenile frogs. We used three different Bd isolates including one from wild R. onca to challenge juvenile frogs and focused on the isolate from R. onca to challenge tadpoles and resulting metamorphs. We found that juveniles from the Bd exposed population were 5.5 times more likely to survive Bd infection and 10 times more likely to clear infections than those from the area without Bd. In contrast, and regardless of the source area, we observed 98% survivorship of tadpoles, but only 19% survivorship of resulting metamorphs following re-exposure. Given the low survivorship of exposed metamorphs in the laboratory, we speculate on how resistance characteristics, whether adaptive or innate, that do not manifest at each life stage could develop in the wild. We suggest that seasonal high temperatures during times when metamorphosis appears common may modulate the effects of the pathogen during this most susceptible life stage.

Global Emergence of Buruli Ulcer

Evidence that Passerine Birds Act as Amplifying Hosts for Usutu Virus Circulation Abstract Environment determines the distribution and prevalence of vector-borne pathogens due to its direct and indirect effects on the hosts, vectors, and pathogens. To investigate the relationship between Usutu virus occurrence and host biodiversity and to characterize the nidus of infection, we used field-based measures of host diversity and density (all birds and only passerines), vector abundance, landscape and Usutu virus prevalence (mosquito infection rate), an emergent disease with a similar cycle to West Nile virus. We collected 908,237 female mosquitoes in an area of 54,984 ha in the Doñana National Park, southern Spain. We identified the mosquitoes and screened them for viruses, censused birds, characterized landscape and climatic variables, and then modeled the presence and infection rate of the virus in relation to host, vector, climatic, and landscape variables. Monthly Usutu presence, detected in Culex perexiguus, was positively related to Passeriformes richness and secondarily to NDVI in the previous month. Our results suggest that Usutu prevalence may be higher when and where host (passerine) richness was high, and thus challenging the conventional idea that host biodiversity reduces flavivirus amplification.