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Titcomb G, Hulke J, Mantas JN, Gituku B, Young H. Cattle aggregations at shared resources create potential parasite exposure hotspots for wildlife. Proc Biol Sci 2023; 290:20232239. [PMID: 38052242 DOI: 10.1098/rspb.2023.2239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Accepted: 11/08/2023] [Indexed: 12/07/2023] Open
Abstract
Globally rising livestock populations and declining wildlife numbers are likely to dramatically change disease risk for wildlife and livestock, especially at resources where they congregate. However, limited understanding of interspecific transmission dynamics at these hotspots hinders disease prediction or mitigation. In this study, we combined gastrointestinal nematode density and host foraging activity measurements from our prior work in an East African tropical savannah system with three estimates of parasite sharing capacity to investigate how interspecific exposures alter the relative riskiness of an important resource - water - among cattle and five dominant herbivore species. We found that due to their high parasite output, water dependence and parasite sharing capacity, cattle greatly increased potential parasite exposures at water sources for wild ruminants. When untreated for parasites, cattle accounted for over two-thirds of total potential exposures around water for wild ruminants, driving 2-23-fold increases in relative exposure levels at water sources. Simulated changes in wildlife and cattle ratios showed that water sources become increasingly important hotspots of interspecific transmission for wild ruminants when relative abundance of cattle parasites increases. These results emphasize that livestock have significant potential to alter the level and distribution of parasite exposures across the landscape for wild ruminants.
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Affiliation(s)
- Georgia Titcomb
- Department of Fish, Wildlife, and Conservation Biology, Colorado State University, Fort Collins 80523-1019, CO, USA
- Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA, USA
| | - Jenna Hulke
- Department of Biology, Texas A&M University, College Station, TX 77843, USA
| | | | - Benard Gituku
- Ecological Monitoring Unit, Ol Pejeta Conservancy, Nanyuki, Kenya
| | - Hillary Young
- Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA, USA
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Evans MV, Ramiadantsoa T, Kauffman K, Moody J, Nunn CL, Rabezara JY, Raharimalala P, Randriamoria TM, Soarimalala V, Titcomb G, Garchitorena A, Roche B. Sociodemographic Variables Can Guide Prioritized Testing Strategies for Epidemic Control in Resource-Limited Contexts. J Infect Dis 2023; 228:1189-1197. [PMID: 36961853 PMCID: PMC11007394 DOI: 10.1093/infdis/jiad076] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Revised: 02/08/2023] [Accepted: 03/22/2023] [Indexed: 03/25/2023] Open
Abstract
BACKGROUND Targeted surveillance allows public health authorities to implement testing and isolation strategies when diagnostic resources are limited, and can be implemented via the consideration of social network topologies. However, it remains unclear how to implement such surveillance and control when network data are unavailable. METHODS We evaluated the ability of sociodemographic proxies of degree centrality to guide prioritized testing of infected individuals compared to known degree centrality. Proxies were estimated via readily available sociodemographic variables (age, gender, marital status, educational attainment, household size). We simulated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) epidemics via a susceptible-exposed-infected-recovered individual-based model on 2 contact networks from rural Madagascar to test applicability of these findings to low-resource contexts. RESULTS Targeted testing using sociodemographic proxies performed similarly to targeted testing using known degree centralities. At low testing capacity, using proxies reduced infection burden by 22%-33% while using 20% fewer tests, compared to random testing. By comparison, using known degree centrality reduced the infection burden by 31%-44% while using 26%-29% fewer tests. CONCLUSIONS We demonstrate that incorporating social network information into epidemic control strategies is an effective countermeasure to low testing capacity and can be implemented via sociodemographic proxies when social network data are unavailable.
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Affiliation(s)
- Michelle V Evans
- Maladies Infectieuses et Vecteurs : Écologie, Génétique, Évolution et Contrôle, Université Montpellier, CNRS, IRD, Montpellier, France
| | - Tanjona Ramiadantsoa
- Maladies Infectieuses et Vecteurs : Écologie, Génétique, Évolution et Contrôle, Université Montpellier, CNRS, IRD, Montpellier, France
| | - Kayla Kauffman
- Department of Evolutionary Anthropology, Duke University, Durham, North Carolina, USA
- Duke Global Health Institute, Durham, North Carolina, USA
- Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, California, USA
| | - James Moody
- Department of Sociology, Duke University, Durham, North Carolina, USA
| | - Charles L Nunn
- Department of Evolutionary Anthropology, Duke University, Durham, North Carolina, USA
- Duke Global Health Institute, Durham, North Carolina, USA
| | - Jean Yves Rabezara
- Department of Science and Technology, University of Antsiranana, Antsiranana, Madagascar
| | | | - Toky M Randriamoria
- Association Vahatra, Antananarivo, Madagascar
- Zoologie et Biodiversité Animale, Domaine Sciences et Technologies, Université d’Antananarivo, Antananarivo, Madagascar
| | - Voahangy Soarimalala
- Association Vahatra, Antananarivo, Madagascar
- Institut des Sciences et Techniques de l’Environnement, Université de Fianarantsoa, Fianarantsoa, Madagascar
| | - Georgia Titcomb
- Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, California, USA
- Marine Science Institute, University of California, Santa Barbara, California, USA
- Department of Fish, Wildlife, and Conservation Biology, Colorado State University, Fort Collins, Colorado, USA
| | - Andres Garchitorena
- Maladies Infectieuses et Vecteurs : Écologie, Génétique, Évolution et Contrôle, Université Montpellier, CNRS, IRD, Montpellier, France
- Pivot, Ifanadiana, Madagascar
| | - Benjamin Roche
- Maladies Infectieuses et Vecteurs : Écologie, Génétique, Évolution et Contrôle, Université Montpellier, CNRS, IRD, Montpellier, France
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Kauffman K, Werner CS, Titcomb G, Pender M, Rabezara JY, Herrera JP, Shapiro JT, Solis A, Soarimalala V, Tortosa P, Kramer R, Moody J, Mucha PJ, Nunn C. Comparing transmission potential networks based on social network surveys, close contacts and environmental overlap in rural Madagascar. J R Soc Interface 2022; 19:20210690. [PMID: 35016555 PMCID: PMC8753172 DOI: 10.1098/rsif.2021.0690] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Accepted: 12/16/2021] [Indexed: 11/12/2022] Open
Abstract
Social and spatial network analysis is an important approach for investigating infectious disease transmission, especially for pathogens transmitted directly between individuals or via environmental reservoirs. Given the diversity of ways to construct networks, however, it remains unclear how well networks constructed from different data types effectively capture transmission potential. We used empirical networks from a population in rural Madagascar to compare social network survey and spatial data-based networks of the same individuals. Close contact and environmental pathogen transmission pathways were modelled with the spatial data. We found that naming social partners during the surveys predicted higher close-contact rates and the proportion of environmental overlap on the spatial data-based networks. The spatial networks captured many strong and weak connections that were missed using social network surveys alone. Across networks, we found weak correlations among centrality measures (a proxy for superspreading potential). We conclude that social network surveys provide important scaffolding for understanding disease transmission pathways but miss contact-specific heterogeneities revealed by spatial data. Our analyses also highlight that the superspreading potential of individuals may vary across transmission modes. We provide detailed methods to construct networks for close-contact transmission pathogens when not all individuals simultaneously wear GPS trackers.
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Affiliation(s)
- Kayla Kauffman
- Department of Evolutionary Anthropology, Duke University, Durham, NC 27708, USA
- Marine Science Institute, University of California, Santa Barbara, CA 93106, USA
| | - Courtney S. Werner
- Department of Evolutionary Anthropology, Duke University, Durham, NC 27708, USA
| | - Georgia Titcomb
- Marine Science Institute, University of California, Santa Barbara, CA 93106, USA
| | | | - Jean Yves Rabezara
- Science de la Nature et Valorisation des Ressources Naturelles, Centre Universitaire Régional de la SAVA, Antalaha, Madagascar
| | | | - Julie Teresa Shapiro
- Department of Life Sciences, Ben-Gurion University of the Negev, Be'er Sheva, Israel
| | - Alma Solis
- Department of Evolutionary Anthropology, Duke University, Durham, NC 27708, USA
- Duke Global Health Institute, Durham, NC 27156, USA
| | | | - Pablo Tortosa
- UMR Processus Infectieux en Milieu Insulaire Tropical (PIMIT), Université de La Réunion, Ile de La Réunion, France
| | - Randall Kramer
- Nicholas School of the Environment, Duke University, Durham, NC 27708, USA
| | - James Moody
- Department of Sociology, Duke University, Durham, NC 27708, USA
| | - Peter J. Mucha
- Department of Mathematics, Dartmouth College, Hanover, NH 03755, USA
| | - Charles Nunn
- Department of Evolutionary Anthropology, Duke University, Durham, NC 27708, USA
- Duke Global Health Institute, Durham, NC 27156, USA
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Titcomb G, Pringle RM, Palmer TM, Young HS. What explains tick proliferation following large-herbivore exclusion? Proc Biol Sci 2018; 285:rspb.2018.0612. [PMID: 29769364 DOI: 10.1098/rspb.2018.0612] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2018] [Accepted: 04/13/2018] [Indexed: 11/12/2022] Open
Affiliation(s)
- Georgia Titcomb
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Goleta, CA, USA .,Mpala Research Centre, PO Box 555, Nanyuki, Kenya
| | - Robert M Pringle
- Mpala Research Centre, PO Box 555, Nanyuki, Kenya.,Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA
| | - Todd M Palmer
- Mpala Research Centre, PO Box 555, Nanyuki, Kenya.,Department of Biology, University of Florida, Gainesville, FL 32611, USA
| | - Hillary S Young
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Goleta, CA, USA.,Mpala Research Centre, PO Box 555, Nanyuki, Kenya
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Titcomb G, Allan BF, Ainsworth T, Henson L, Hedlund T, Pringle RM, Palmer TM, Njoroge L, Campana MG, Fleischer RC, Mantas JN, Young HS. Interacting effects of wildlife loss and climate on ticks and tick-borne disease. Proc Biol Sci 2018; 284:rspb.2017.0475. [PMID: 28878055 DOI: 10.1098/rspb.2017.0475] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Accepted: 07/24/2017] [Indexed: 01/18/2023] Open
Abstract
Both large-wildlife loss and climatic changes can independently influence the prevalence and distribution of zoonotic disease. Given growing evidence that wildlife loss often has stronger community-level effects in low-productivity areas, we hypothesized that these perturbations would have interactive effects on disease risk. We experimentally tested this hypothesis by measuring tick abundance and the prevalence of tick-borne pathogens (Coxiella burnetii and Rickettsia spp.) within long-term, size-selective, large-herbivore exclosures replicated across a precipitation gradient in East Africa. Total wildlife exclusion increased total tick abundance by 130% (mesic sites) to 225% (dry, low-productivity sites), demonstrating a significant interaction of defaunation and aridity on tick abundance. When differing degrees of exclusion were tested for a subset of months, total tick abundance increased from 170% (only mega-herbivores excluded) to 360% (all large wildlife excluded). Wildlife exclusion differentially affected the abundance of the three dominant tick species, and this effect varied strongly over time, likely due to differences among species in their host associations, seasonality, and other ecological characteristics. Pathogen prevalence did not differ across wildlife exclusion treatments, rainfall levels, or tick species, suggesting that exposure risk will respond to defaunation and climate change in proportion to total tick abundance. These findings demonstrate interacting effects of defaunation and aridity that increase disease risk, and they highlight the need to incorporate ecological context when predicting effects of wildlife loss on zoonotic disease dynamics.
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Affiliation(s)
- Georgia Titcomb
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA, USA .,Mpala Research Centre, Box 555, Nanyuki, Kenya
| | - Brian F Allan
- Mpala Research Centre, Box 555, Nanyuki, Kenya.,Department of Entomology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Tyler Ainsworth
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA, USA
| | - Lauren Henson
- Center for Conservation Genomics, Smithsonian Conservation Biology Institute, National Zoological Park, Washington, DC 20008, USA
| | - Tyler Hedlund
- Department of Entomology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Robert M Pringle
- Mpala Research Centre, Box 555, Nanyuki, Kenya.,Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA
| | - Todd M Palmer
- Mpala Research Centre, Box 555, Nanyuki, Kenya.,Department of Biology, University of Florida, Gainesville, FL 32611, USA
| | - Laban Njoroge
- Invertebrate Zoology Section, National Museums of Kenya, Nairobi, Kenya
| | - Michael G Campana
- Center for Conservation Genomics, Smithsonian Conservation Biology Institute, National Zoological Park, Washington, DC 20008, USA
| | - Robert C Fleischer
- Center for Conservation Genomics, Smithsonian Conservation Biology Institute, National Zoological Park, Washington, DC 20008, USA
| | | | - Hillary S Young
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA, USA.,Mpala Research Centre, Box 555, Nanyuki, Kenya
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Kilpatrick AM, Salkeld DJ, Titcomb G, Hahn MB. Conservation of biodiversity as a strategy for improving human health and well-being. Philos Trans R Soc Lond B Biol Sci 2018; 372:rstb.2016.0131. [PMID: 28438920 PMCID: PMC5413879 DOI: 10.1098/rstb.2016.0131] [Citation(s) in RCA: 80] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/18/2017] [Indexed: 12/24/2022] Open
Abstract
The Earth's ecosystems have been altered by anthropogenic processes, including land use, harvesting populations, species introductions and climate change. These anthropogenic processes greatly alter plant and animal communities, thereby changing transmission of the zoonotic pathogens they carry. Biodiversity conservation may be a potential win-win strategy for maintaining ecosystem health and protecting public health, yet the causal evidence to support this strategy is limited. Evaluating conservation as a viable public health intervention requires answering four questions: (i) Is there a general and causal relationship between biodiversity and pathogen transmission, and if so, which direction is it in? (ii) Does increased pathogen diversity with increased host biodiversity result in an increase in total disease burden? (iii) Do the net benefits of biodiversity conservation to human well-being outweigh the benefits that biodiversity-degrading activities, such as agriculture and resource utilization, provide? (iv) Are biodiversity conservation interventions cost-effective when compared to other options employed in standard public health approaches? Here, we summarize current knowledge on biodiversity-zoonotic disease relationships and outline a research plan to address the gaps in our understanding for each of these four questions. Developing practical and self-sustaining biodiversity conservation interventions will require significant investment in disease ecology research to determine when and where they will be effective.This article is part of the themed issue 'Conservation, biodiversity and infectious disease: scientific evidence and policy implications'.
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Affiliation(s)
- A Marm Kilpatrick
- Department of Ecology and Evolutionary Biology, University of California, Santa Cruz 95064, USA
| | - Daniel J Salkeld
- Department of Biology, Colorado State University, Fort Collins, CO 80523, USA
| | - Georgia Titcomb
- Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA 93106, USA
| | - Micah B Hahn
- Centers for Disease Control and Prevention, Fort Collins, CO 80521, USA
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Weinstein S, Titcomb G, Agwanda B, Riginos C, Young H. Parasite responses to large mammal loss in an African savanna. Ecology 2017; 98:1839-1848. [PMID: 28403506 DOI: 10.1002/ecy.1858] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Revised: 03/01/2017] [Accepted: 04/05/2017] [Indexed: 11/11/2022]
Abstract
Biodiversity loss can alter disease transmission; however, the magnitude and direction of these effects vary widely across ecosystems, scales, and pathogens. Here we experimentally examine the effects of one of the most globally pervasive patterns of biodiversity decline, the selective loss of large wildlife, on infection probability, intensity and population size of a group of common rodent-borne parasites - macroparasitic helminths. Consistent with previous work on vector-borne pathogens, we found that large wildlife removal causes strong and systematic increases of rodent-borne parasites, largely due to increases in rodent density, as rodents are released from competition with larger herbivores. Although we predicted that increased host density would also increase per capita infection among all directly transmitted parasites, this additional amplification occurred for only two of three examined parasites. Furthermore, the actual effects of large mammal loss on per capita infection were mediated by the complex suite of abiotic and biotic factors that regulate parasite transmission. Thus, while these results strongly suggest that large wildlife loss will cause systematic increases in rodent parasite populations, they also underscore the difficulty of making more specific predictions for a given parasite based on simple attributes such as transmission mode or life history strategy. Instead, detailed information on the ecology of each parasite species would be necessary to make more accurate predictions of how biodiversity loss will affect infection.
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Affiliation(s)
- Sara Weinstein
- Department of Ecology, Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, California, USA
| | - Georgia Titcomb
- Department of Ecology, Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, California, USA.,Mpala Research Centre, Nanyuki, Kenya
| | - Bernard Agwanda
- Zoology Department, Mammalogy Section, National Museums Kenya, Nairobi, Kenya
| | - Corinna Riginos
- Mpala Research Centre, Nanyuki, Kenya.,Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming, USA
| | - Hillary Young
- Department of Ecology, Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, California, USA.,Mpala Research Centre, Nanyuki, Kenya
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Forbes E, ter Kuile AM, Orr D, Titcomb G. Navigating the cascades of circumstance
Serendipity An Ecologist's Quest to Understand Nature
James A. Estes
University of California Press, 2016. 291 pp. Science 2016. [DOI: 10.1126/science.aaf7138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
An ecologist reflects on the unexpected twists and turns that shaped his scientific career
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Affiliation(s)
- Elizabeth Forbes
- The reviewers are graduate students in the Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Ana Miller ter Kuile
- The reviewers are graduate students in the Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Devyn Orr
- The reviewers are graduate students in the Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Georgia Titcomb
- The reviewers are graduate students in the Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
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