Browsing by Author "Estes, Anna"

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A multi-scale approach for integrating species distribution models with landscape connectivity to identify critical linkage zones for African savanna elephants (Loxodonta africana)
(Elsevier, 2025-05-27) Song, Lei; Frazier, Amy; Estes, Anna; Estes, Lyndon
The populations of African savanna elephants have declined by an estimated 60 % since the 1970s, which can be attributed to a mixture of poaching and habitat loss. Human activities and environmental changes have caused unprecedented loss and fragmentation of elephant natural habitats, resulting in the isolation of elephant pop- ulations. Preserving habitat connectivity is thus increasingly important to conserve remaining elephants’ pop- ulations and maintain ecological functions. A major challenge in large-scale connectivity modeling is data availability constraints. To tackle this issue, we developed an integrated modeling approach that leverages multiple, publicly available occurrence datasets, which vary in format and quality, with a multi-scale SDM to estimate spatial suitability of African savanna elephants. Two SDMs, based on polygon-based observations and presence-only occurrences, were separately calibrated using the Isolation Forest algorithm and then ensembled using Bayes fusion. Particularly, we included multiple landscape metrics derived from a high-resolution (~5 m) land cover map as environmental predictors in the SDMs to characterize the landscape structure influencing elephant movement. The resulting environmental suitability was then used to map landscape connectivity through circuit theory, implemented in Circuitscape. Using species distribution modeling (SDM) and graph-based landscape connectivity modeling, we aimed to understand population connectivity and target vital corridors across Tanzania, one of the most important elephant range states. Shapley value-based variable analysis in SDM revealed that human modifications strongly influence elephant distribution at broad scales, while habitat frag- mentation and connectivity impact their activities. Connectivity results further highlighted that both long- and short-distance connectivity are currently facing significant threats from intensive human activities (e.g., agri- culture) in Tanzania and identified critical linkage zones that should be targeted for connectivity conservation efforts.
Assessing Risk Factors for Trypanosome Infections in Cattle in Wildlife Interface Areas in Northern Tanzania
(Journal of Infectious Diseases and Epidemiology, 2019-05-04) Ngongolo, Kelvin; Estes, Anna; Hudson, Peter; Gwakisa, Paul
Trypanosomosis is a vector-borne, tropical disease that causes mortality and morbidity in livestock and humans. In this study we investigated the risk factors for trypanosome infection in cattle in the Maasai Steppe of northern Tanzania. We assessed the influence of age, sex, herd size and history of treatment against trypanosomosis as risk factors of trypanosome infection. Cattle blood samples were collected from 150 cattle in three villages in the vicinity of Tarangire National Park, which acts as a reservoir of tsetse flies, the trypanosome vector. Parasite species were identified using a nested Polymerase Chain Reaction (n-PCR). Smaller herd sizes, young age (1-2 years), and male sex significantly increased the risk of trypanosome infections. Efforts to control trypanosome infection should be strategically based on location and season while considering age, treatment and herd size as risk factors.
Identification of Bacillus anthracis, Brucella spp., and Coxiella burnetii DNA signatures from bushmeat
(Springer Nature Limited, 2021-07-21) Katani, Robab; Schilling, Megan; Lyimo, Beatus; Eblate, Ernest; Martin, Andimile; Tonui, Triza; Cattadori, Isabella; Francesconi, Stephen; Estes, Anna; Rentsch, Dennis; Srinivasan, Sreenidhi; Lyimo, Samson; Munuo, Lidia; Tiambo, Christian; Stomeo, Francesca; Gwakisa, Paul; Mosha, Fausta; Hudson, Peter; Buza, Joram; Kapur, Vivek
Meat from wildlife species (bushmeat) represents a major source of dietary protein in low- and middle-income countries where humans and wildlife live in close proximity. Despite the occurrence of zoonotic pathogens in wildlife, their prevalence in bushmeat remains unknown. To assess the risk of exposure to major pathogens in bushmeat, a total of 3784 samples, both fresh and processed, were collected from three major regions in Tanzania during both rainy and dry seasons, and were screened by real-time PCR for the presence of DNA signatures of Bacillus anthracis (B. anthracis), Brucella spp. (Brucella) and Coxiella burnetii (Coxiella). The analysis identified DNA signatures of B. anthracis (0.48%), Brucella (0.9%), and Coxiella (0.66%) in a total of 77 samples. Highest prevalence rates of B. anthracis, Brucella, and Coxiella were observed in wildebeest (56%), dik-dik (50%), and impala (24%), respectively. Fresh samples, those collected during the rainy season, and samples from Selous or Serengeti had a greater relative risk of being positive. Microbiome characterization identified Firmicutes and Proteobacteria as the most abundant phyla. The results highlight and define potential risks of exposure to endemic wildlife diseases from bushmeat and the need for future investigations to address the public health and emerging infectious disease risks associated with bushmeat harvesting, trade, and consumption.
Influence of Land Cover and Host Species on Trypanosome Infection in Cattle and its Socio-Economic Impacts to Pastoralists of the Maasai Steppe, Tanzania
(Journal of Infectious Diseases and Epidemiology, 2020-01-27) Ngongolo, Kelvin; Shirima, Gabriel; Mpolya, Emmanuel; Estes, Anna; Hudson, Peter; Gwakisa, Paul
Introduction Trypanosome infections result into trypanosomosis in cattle and this is an infection detrimental to pastoralist income. The patterns of transmission are thought to be influenced by ecological factors including wildlife and land cover. We assessed the influence of the relative abundance of wildlife and land cover (cultivation and habitat type) on the presence of trypanosome infections in replicated cattle herds of the Maasai Steppe. Methodology We undertook a cohort field study in three villages of the Maasai Steppe: Sukuro, Kimotorok and Oltukai. The study took place in July 2017 and October 2017 and utilized 50 cattle from each village. Pastoralists were asked questions during each visit when blood sampled were taken to seek their viewpoint on the relative abundance of wildlife, habitat types and cultivation observed in the areas their cattle grazed. In addition, the percentage cover of cultivated land and habitat types in the grazing areas were determined during field visits and participatory mapping with pastoralists. A systematic review was used to understand the socio-economic importance of trypanosomosis. The species of trypanosomes in cattle were identified using nested Polymerase chain reaction (n-PCR). Results There was a significant and positive association between the presence of trypanosome infection and the abundance of wildlife within grazing areas, in particular the abundance of buffaloes (Odd Ratio > 1, P = 0.038, 95% CI 1.26 to 1.38) when cattle grazed in woodland habitats. Cultivation on grazing areas had a negative association with the presence of trypanosome infections (R < 1, P = 0.001, 95% CI 0.0614 to 0.0986) in cattle but this varied between villages. A systematic review showed that trypanosomosis had socio-economic impacts such as loss of income, reduced quality, and quantity of livestock products, management cost, and inadequate provisions of socio-services and potential zoonotic transmission to humans. Conclusion & recommendations The socio-economic impacts of trypanosomosis will continue to be a challenge to pastoralists when cattle are grazed close to wildlife areas which are infested with tsetse fly habitats. Control strategies for trypanosome infection in cattle on the Maasai Steppe should consider the interaction of cattle with ecological factors.
Microbial Diversity in Bushmeat Samples Recovered from the Serengeti Ecosystem in Tanzania
(Nature Publishing Group UK, 2019-12-02) Katani, Robab; Schilling, Megan; Lyimo, Beatus; Tonui, Triza; Cattadori, Isabella; Eblate, Ernest; Martin, Andimile; Estes, Anna; Buza, Teresia; Rentsch, Dennis; Davenpor, Karen; Hovde, Blake; Lyimo, Samson; Munuo, Lydia; Stomeo, Francesca; Tiambo, Christian; Radzio-Basu, Jessica; Mosha, Fausta; Hudson, Peter; Buza, Joram; Kapur, Vivek
Bushmeat, the meat and organs derived from wildlife species, is a common source of animal protein in the diets of those living in sub-Saharan Africa and is frequently associated with zoonotic spillover of dangerous pathogens. Given the frequent consumption of bushmeat in this region and the lack of knowledge about the microbial communities associated with this meat, the microbiome of 56 fresh and processed bushmeat samples ascertained from three districts in the Western Serengeti ecosystem in Tanzania was characterized using 16S rRNA metagenomic sequencing. The results show that the most abundant phyla present in bushmeat samples include Firmicutes (67.8%), Proteobacteria (18.4%), Cyanobacteria (8.9%), and Bacteroidetes (3.1%). Regardless of wildlife species, sample condition, season, or region, the microbiome is diverse across all samples, with no significant difference in alpha or beta diversity. The findings also suggest the presence of DNA signatures of potentially dangerous zoonotic pathogens, including those from the genus Bacillus, Brucella, Coxiella, and others, in bushmeat. Together, this investigation provides a better understanding of the microbiome associated with this major food source in samples collected from the Western Serengeti in Tanzania and highlights a need for future investigations on the potential health risks associated with the harvesting, trade, and consumption of bushmeat in Sub-Saharan Africa
Microbial Diversity in Bushmeat Samples Recovered from the Serengeti Ecosystem in Tanzania
(Scientific Reports, 2019-12-02) Katani, Robab; Schilling, Megan; Lyimo, Beatus; Tonui, Triza; Cattadori, Isabella; Eblate, Ernest; Martin, Andimile; Estes, Anna; Buza, Teresia; Rentsch, Dennis; Davenport, Karen; Hovde, Blake; Lyimo, Samson; Munuo, Lydia; Stomeo, Francesca; Tiambo, Christian; Radzio-Basu, Jessica; Mosha, Fausta; Hudson, Peter; Buza, Joram; Kapur, Vivek
Bushmeat, the meat and organs derived from wildlife species, is a common source of animal protein in the diets of those living in sub-Saharan Africa and is frequently associated with zoonotic spillover of dangerous pathogens. Given the frequent consumption of bushmeat in this region and the lack of knowledge about the microbial communities associated with this meat, the microbiome of 56 fresh and processed bushmeat samples ascertained from three districts in the Western Serengeti ecosystem in Tanzania was characterized using 16S rRNA metagenomic sequencing. The results show that the most abundant phyla present in bushmeat samples include Firmicutes (67.8%), Proteobacteria (18.4%), Cyanobacteria (8.9%), and Bacteroidetes (3.1%). Regardless of wildlife species, sample condition, season, or region, the microbiome is diverse across all samples, with no significant difference in alpha or beta diversity. The findings also suggest the presence of DNA signatures of potentially dangerous zoonotic pathogens, including those from the genus Bacillus, Brucella, Coxiella, and others, in bushmeat. Together, this investigation provides a better understanding of the microbiome associated with this major food source in samples collected from the Western Serengeti in Tanzania and highlights a need for future investigations on the potential health risks associated with the harvesting, trade, and consumption of bushmeat in Sub-Saharan Africa
Molecular species identification of bushmeat recovered from the Serengeti ecosystem in Tanzania.
(PLOS ONE, 2020-09-14) Schilling, Megan; Estes, Anna; Eblate, Ernest; Martin, Andimile; Rentsch, Dennis; Katani, Robab; Joseph, Asteria; Kindoro, Fatuma; Lyimo, Beatus; Radzio-Basu, Jessica; Cattadori, Isabella; Hudson, Peter; Kapur, Vivek; Gwakisa, Paul; Buza, Joram
Bushmeat harvesting and consumption represents a potential risk for the spillover of endemic zoonotic pathogens, yet remains a common practice in many parts of the world. Given that the harvesting and selling of bushmeat is illegal in Tanzania and other parts of Africa, the supply chain is informal and may include hunters, whole-sellers, retailers, and individual resellers who typically sell bushmeat in small pieces. These pieces are often further processed, obscuring species-identifying morphological characteristics, contributing to incomplete or mistaken knowledge of species of origin and potentially confounding assessments of pathogen spillover risk and bushmeat offtake. The current investigation sought to identify the species of origin and assess the concordance between seller-reported and laboratory-confirmed species of origin of bushmeat harvested from in and around the Serengeti National Park in Tanzania. After obtaining necessary permits, the species of origin of a total of 151 bushmeat samples purchased from known intermediaries from 2016 to 2018 were characterized by PCR and sequence analysis of the cytochrome B (CytB) gene. Based on these sequence analyses, 30%, 95% Confidence Interval (CI: 24.4-38.6) of bushmeat samples were misidentified by sellers. Misreporting amongst the top five source species (wildebeest, buffalo, impala, zebra, and giraffe) ranged from 20% (CI: 11.4-33.2) for samples reported as wildebeest to 47% (CI: 22.2-72.7) for samples reported as zebra although there was no systematic bias in reporting. Our findings suggest that while misreporting errors are unlikely to confound wildlife offtake estimates for bushmeat consumption within the Serengeti ecosystem, the role of misreporting bias on the risk of spillover events of endemic zoonotic infections from bushmeat requires further investigation.