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Ekselius L, Gerdin B, Vahlquist A. The Syphilis Pandemic Prior to Penicillin: Origin, Health Issues, Cultural Representation and Ethical Challenges. Acta Derm Venereol 2024; 104:adv34879. [PMID: 38436430 PMCID: PMC10926575 DOI: 10.2340/actadv.v104.34879] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Accepted: 01/16/2024] [Indexed: 03/05/2024] Open
Abstract
Syphilis is currently a treatable disease, with a low incidence in most developed countries, although the prevalence has increased recently, especially among men-who-have-sex-with-men. In many of the least developed countries, however, syphilis is still a major health problem, although the problem is not comparable to the desperate situation worldwide less than 80 years ago. At that time, and for many centuries previously, syphilis dramatically affected the lives and health of individuals and threatened the well-being of many societies. This review examines the aetiology, transmission, and many manifestations of syphilis from a historical perspective, emphasizing morbidity, treatment, psychosocial and cultural manifestations, as well as ethical issues uncovered in the clinical search for knowledge about the manifestations of the disease.
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Affiliation(s)
- Lisa Ekselius
- Department of Women's and Children's Health, Uppsala University, Uppsala, Sweden
| | - Bengt Gerdin
- Department of Surgical Sciences, Uppsala University, Uppsala, Sweden
| | - Anders Vahlquist
- Department of Medical Sciences, Uppsala University, Uppsala, Sweden.
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2
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Kenyon C, Herrmann B, Hughes G, de Vries HJ. Management of asymptomatic sexually transmitted infections in Europe: towards a differentiated, evidence-based approach. THE LANCET REGIONAL HEALTH. EUROPE 2023; 34:100743. [PMID: 37927435 PMCID: PMC10624996 DOI: 10.1016/j.lanepe.2023.100743] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Revised: 09/05/2023] [Accepted: 09/18/2023] [Indexed: 11/07/2023]
Abstract
Most sexually transmitted infections (STIs) can be accurately diagnosed and treated during asymptomatic carriage. Widespread screening for these STIs is therefore assumed to be an effective way to reduce their prevalence and associated disease. In this review, we provide evidence that this is the case for HIV and syphilis. However, for other STIs such as Neisseria gonorrhoeae and Chlamydia trachomatis, our review reveals that the evidence that screening reduces infection prevalence and associated disease is weak. There is also growing evidence of harms from screening that might outweigh any benefits. The harms include the increased consumption of antimicrobials that follows frequent screening and increased detection of asymptomatic STIs in key populations, such as men who have sex with men taking HIV pre-exposure prophylaxis, and associated risk of antimicrobial resistance in target and non-target organisms. There may also be psycho-social harm associated with an STI diagnosis. We conclude that in the absence of symptoms, in high STI prevalence populations frequent STI screening should be limited to HIV and syphilis.
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Affiliation(s)
- Chris Kenyon
- Department of Clinical Sciences, Institute of Tropical Medicine, Antwerp, Belgium
| | - Björn Herrmann
- Section of Clinical Microbiology, Department of Medical Sciences, Uppsala University, Uppsala, Sweden
| | - Gwenda Hughes
- Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, UK
| | - Henry J.C. de Vries
- Department of Dermatology, Amsterdam UMC Location University of Amsterdam, Meibergdreef 9, Amsterdam, the Netherlands
- Amsterdam Institute for Infection and Immunity, Infectious Diseases, Amsterdam, the Netherlands
- Center for Sexual Health, Department of Infectious Diseases, Public Health Service Amsterdam, the Netherlands
- Amsterdam Institute for Global Health and Development, Amsterdam, the Netherlands
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3
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Oumarou Hama H, Boualam MA, Levasseur A, Ardagna Y, Adalian P, Chaix AC, Drancourt M. Old World Medieval Treponema pallidum Complex Treponematosis: A Case Report. J Infect Dis 2023; 228:503-510. [PMID: 37440462 DOI: 10.1093/infdis/jiad248] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Revised: 05/02/2023] [Accepted: 06/30/2023] [Indexed: 07/15/2023] Open
Abstract
BACKGROUND Introduction of 1 Treponema pallidum complex pathogen in naive European populations following the return of Christopher Columbus' troops from Central America in 1493 is a central dogma in venereology. METHODS Among skeletal elements from the seventh or eighth century uncovered in Roquevaire, France, individual RS-1003 femur macroscopically suspected of having an infectious disease was investigated by means of paleoautoimmunohistochemistry, direct metagenomics, and paleoserology, along with 1 control femur from an apparently healthy individual (R-1003) and experimental negative controls. RESULTS RS-1003 femur showed infectious bone; paleoautoimmunohistochemistry of the lesions led to microscopic detection of a T. pallidum complex pathogen. Phylogenetic analyses comprising 71 T. pallidum complex-specific reads covering 2.37% of the T. pallidum subsp. pallidum reference genome sequence revealed an ancestral T. pallidum complex pathogen in the lesion. Paleoserology detecting T. pallidum-specific antigens confirmed positive serological findings in individual RS-1003. Individual R-1003 and the negative controls remained negative. CONCLUSIONS This case, predating by 8 centuries previous detections of T. pallidum complex treponematosis in Europe, indicated that European populations were not naive to these pathogens before the 1493 introduction of a Central American T. pallidum complex pathogen overwhelming the T. pallidum ones previously circulating in the Old World. These data break a century-old dogma in medical microbiology.
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Affiliation(s)
- Hamadou Oumarou Hama
- Aix-Marseille University, IRD, MEPHI, Institut Méditerranée Infection, Marseille, France
- Institut Méditerranée Infection, Marseille, France
| | - Mahmoud A Boualam
- Aix-Marseille University, IRD, MEPHI, Institut Méditerranée Infection, Marseille, France
- Institut Méditerranée Infection, Marseille, France
| | - Anthony Levasseur
- Aix-Marseille University, IRD, MEPHI, Institut Méditerranée Infection, Marseille, France
- Institut Méditerranée Infection, Marseille, France
| | - Yann Ardagna
- Aix-Marseille University, Centre National de la Recherche Scientifique, Etablissement Français du Sang, Anthropologie, Droit, Ethique et Santé, Marseille, France
| | - Pascal Adalian
- Aix-Marseille University, Centre National de la Recherche Scientifique, Etablissement Français du Sang, Anthropologie, Droit, Ethique et Santé, Marseille, France
| | - Annie-Claire Chaix
- Association pour la Sauvegarde du Patrimoine Historique et Culturel de la Commune de Roquevaire, Roquevaire, France
| | - Michel Drancourt
- Aix-Marseille University, IRD, MEPHI, Institut Méditerranée Infection, Marseille, France
- Institut Méditerranée Infection, Marseille, France
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4
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Sankaran D, Partridge E, Lakshminrusimha S. Congenital Syphilis-An Illustrative Review. CHILDREN (BASEL, SWITZERLAND) 2023; 10:1310. [PMID: 37628309 PMCID: PMC10453258 DOI: 10.3390/children10081310] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 07/19/2023] [Accepted: 07/25/2023] [Indexed: 08/27/2023]
Abstract
Congenital syphilis is caused by the spirochete, Treponema pallidum, which can be transmitted from an infected mother to her fetus during pregnancy or by contact with a maternal lesion at the time of delivery. The incidence of congenital syphilis is rapidly increasing all over world with 700,000 to 1.5 million cases reported annually between 2016 and 2023. Despite the widespread availability of Penicillin, 2677 cases were reported in 2021 in the US. Clinical manifestations at birth can vary widely ranging from asymptomatic infection to stillbirth or neonatal death. Low birth weight, rash, hepatosplenomegaly, osteolytic bone lesions, pseudoparalysis, central nervous system infection, and long-term disabilities have been reported in newborns with congenital syphilis. Prevention of congenital syphilis is multifaceted and involves routine antenatal screening, timely treatment of perinatal syphilis with penicillin, partner tracing and treatment, and health education programs emphasizing safe sex practices and strategies to curb illicit drug use. Neonatal management includes risk stratification based on maternal syphilis history, evaluation (nontreponemal testing, complete blood counts, cerebrospinal fluid, and long-bone analysis), treatment with penicillin, and followup treponemal testing. Public health measures that enhance early detection during pregnancy and treatment with penicillin, especially in high-risk mothers, are urgently needed to prevent future cases of congenital syphilis.
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Affiliation(s)
- Deepika Sankaran
- Division of Neonatology, Department of Pediatrics, University of California Davis, Sacramento, CA 95817, USA;
| | - Elizabeth Partridge
- Division of Infectious Diseases, Department of Pediatrics, University of California Davis, Sacramento, CA 95817, USA;
| | - Satyan Lakshminrusimha
- Division of Neonatology, Department of Pediatrics, University of California Davis, Sacramento, CA 95817, USA;
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5
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Kennedy DA. Death is overrated: the potential role of detection in driving virulence evolution. Proc Biol Sci 2023; 290:20230117. [PMID: 36987649 PMCID: PMC10050922 DOI: 10.1098/rspb.2023.0117] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Accepted: 03/03/2023] [Indexed: 03/30/2023] Open
Abstract
A common assumption in the evolution of virulence theory literature is that pathogens transmit better when they exploit their host more heavily, but by doing so, they impose a greater risk of killing their host, thus truncating infectious periods and reducing their own opportunities for transmission. Here, I derive an equation for the magnitude of this cost in terms of the infection fatality rate, and in doing so, I show that there are many cases where mortality costs are too small to plausibly constrain increases in host exploitation by pathogens. I propose that pathogen evolution may often be constrained by detection costs, whereby hosts alter their behaviour when infection is detectable, and thus reduce pathogen opportunities for onward transmission. I then derive an inequality to illustrate when mortality costs or detection costs impose stronger constraints on pathogen evolution, and I use empirical data from the literature to demonstrate that detection costs are frequently large in both human and animal populations. Finally, I give examples of how evolutionary predictions can change depending on whether costs of host exploitation are borne out through mortality or detection.
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Affiliation(s)
- David A. Kennedy
- Department of Biology, Center for Infectious Disease Dynamics, The Pennsylvania State University, University Park, PA, USA
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6
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van der Kuyl AC. Historic and Prehistoric Epidemics: An Overview of Sources Available for the Study of Ancient Pathogens. EPIDEMIOLOGIA 2022; 3:443-464. [PMID: 36547255 PMCID: PMC9778136 DOI: 10.3390/epidemiologia3040034] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Revised: 09/26/2022] [Accepted: 09/28/2022] [Indexed: 12/24/2022] Open
Abstract
Since life on earth developed, parasitic microbes have thrived. Increases in host numbers, or the conquest of a new species, provide an opportunity for such a pathogen to enjoy, before host defense systems kick in, a similar upsurge in reproduction. Outbreaks, caused by "endemic" pathogens, and epidemics, caused by "novel" pathogens, have thus been creating chaos and destruction since prehistorical times. To study such (pre)historic epidemics, recent advances in the ancient DNA field, applied to both archeological and historical remains, have helped tremendously to elucidate the evolutionary trajectory of pathogens. These studies have offered new and unexpected insights into the evolution of, for instance, smallpox virus, hepatitis B virus, and the plague-causing bacterium Yersinia pestis. Furthermore, burial patterns and historical publications can help in tracking down ancient pathogens. Another source of information is our genome, where selective sweeps in immune-related genes relate to past pathogen attacks, while multiple viruses have left their genomes behind for us to study. This review will discuss the sources available to investigate (pre)historic diseases, as molecular knowledge of historic and prehistoric pathogens may help us understand the past and the present, and prepare us for future epidemics.
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Affiliation(s)
- Antoinette C. van der Kuyl
- Laboratory of Experimental Virology, Department of Medical Microbiology and Infection Prevention, Amsterdam UMC, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands; ; Tel.: +31-205-666-778
- Amsterdam Institute for Infection and Immunity, 1100 DD Amsterdam, The Netherlands
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7
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Giffin K, Lankapalli AK, Sabin S, Spyrou MA, Posth C, Kozakaitė J, Friedrich R, Miliauskienė Ž, Jankauskas R, Herbig A, Bos KI. A treponemal genome from an historic plague victim supports a recent emergence of yaws and its presence in 15 th century Europe. Sci Rep 2020; 10:9499. [PMID: 32528126 PMCID: PMC7290034 DOI: 10.1038/s41598-020-66012-x] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Accepted: 03/30/2020] [Indexed: 12/30/2022] Open
Abstract
Developments in techniques for identification of pathogen DNA in archaeological samples can expand our resolution of disease detection. Our application of a non-targeted molecular screening tool for the parallel detection of pathogens in historical plague victims from post-medieval Lithuania revealed the presence of more than one active disease in one individual. In addition to Yersinia pestis, we detected and genomically characterized a septic infection of Treponema pallidum pertenue, a subtype of the treponemal disease family recognised as the cause of the tropical disease yaws. Our finding in northern Europe of a disease that is currently restricted to equatorial regions is interpreted within an historical framework of intercontinental trade and potential disease movements. Through this we offer an alternative hypothesis for the history and evolution of the treponemal diseases, and posit that yaws be considered an important contributor to the sudden epidemic of late 15th century Europe that is widely ascribed to syphilis.
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Affiliation(s)
- Karen Giffin
- Max Planck Institute for the Science of Human History, Jena, Germany
| | | | - Susanna Sabin
- Max Planck Institute for the Science of Human History, Jena, Germany
| | - Maria A Spyrou
- Max Planck Institute for the Science of Human History, Jena, Germany
| | - Cosimo Posth
- Max Planck Institute for the Science of Human History, Jena, Germany.,Institute for Archaeological Sciences, Archaeo- and Palaeogenetics, University of Tübingen, Rümelinstraße 23, 72070, Tübingen, Germany
| | | | | | | | | | - Alexander Herbig
- Max Planck Institute for the Science of Human History, Jena, Germany.
| | - Kirsten I Bos
- Max Planck Institute for the Science of Human History, Jena, Germany.
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8
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Abstract
Researchers from the Division of Paleopathology of Pisa University (Pisa, Italy) exhumed the well-preserved skeleton of Maria Salviati (1499–1543), wife of Giovanni de’ Medici, named “Giovanni of the Black Bands,” in Florence in 2012. Many lytic lesions had affected the skull of Maria on the frontal bone and on the parietal bones. These lesions are pathognomonic for syphilis. An ancient diagnosis of syphilis for Maria Salviati does not emerge from the historical sources, although the symptoms manifested in her last years of life are compatible with a colorectal localization, including severe hemorrhages, caused by syphilitic infection. The case of Maria Salviati can be compared with those of other famous Italian noblewomen of the Renaissance, such as Isabella of Aragon (1470–1524) and Maria of Aragon (1503–1568). Paleopathology made it possible to directly observe a “secret illness” to which noblewomen were susceptible as a result of the sexual conduct of their husbands.
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9
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Acevedo MA, Dillemuth FP, Flick AJ, Faldyn MJ, Elderd BD. Virulence-driven trade-offs in disease transmission: A meta-analysis. Evolution 2019; 73:636-647. [PMID: 30734920 DOI: 10.1111/evo.13692] [Citation(s) in RCA: 74] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Accepted: 12/22/2018] [Indexed: 12/31/2022]
Abstract
The virulence-transmission trade-off hypothesis proposed more than 30 years ago is the cornerstone in the study of host-parasite co-evolution. This hypothesis rests on the premise that virulence is an unavoidable and increasing cost because the parasite uses host resources to replicate. This cost associated with replication ultimately results in a deceleration in transmission rate because increasing within-host replication increases host mortality. Empirical tests of predictions of the hypothesis have found mixed support, which cast doubt about its overall generalizability. To quantitatively address this issue, we conducted a meta-analysis of 29 empirical studies, after reviewing over 6000 published papers, addressing the four core relationships between (1) virulence and recovery rate, (2) within-host replication rate and virulence, (3) within-host replication and transmission rate, and (4) virulence and transmission rate. We found strong support for an increasing relationship between replication and virulence, and replication and transmission. Yet, it is still uncertain if these relationships generally decelerate due to high within-study variability. There was insufficient data to quantitatively test the other two core relationships predicted by the theory. Overall, the results suggest that the current empirical evidence provides partial support for the trade-off hypothesis, but more work remains to be done.
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Affiliation(s)
- Miguel A Acevedo
- Department of Wildlife Ecology and Conservation, University of Florida, Gainesville, Florida, 32611
| | - Forrest P Dillemuth
- Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana, 70803
| | - Andrew J Flick
- Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana, 70803
| | - Matthew J Faldyn
- Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana, 70803
| | - Bret D Elderd
- Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana, 70803
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10
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Mesía-Montenegro C. Julio Tello as a medical anthropologist: assessing the antiquity of syphilis in ancient Peru. ACTA ACUST UNITED AC 2018; 25:541-552. [PMID: 29898134 DOI: 10.1590/s0104-59702018000200013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Accepted: 09/26/2017] [Indexed: 11/22/2022]
Abstract
This paper explores the methods used by Julio Tello to address the antiquity of syphilis in ancient Peru, examining his thesis La antigüedad de la sífilis en el antiguo Perú to understand the logic behind the procedures he used to test his hypothesis. The contention presented here is that despite being a medical thesis, his text can actually be considered an exploration of the origins of syphilis using a truly anthropological method, making Tello a pioneer in the subfield of medical anthropology in the Andes.
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11
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The human female urogenital microbiome: complexity in normality. Emerg Top Life Sci 2017; 1:363-372. [PMID: 33525775 DOI: 10.1042/etls20170042] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2017] [Revised: 09/13/2017] [Accepted: 09/29/2017] [Indexed: 12/19/2022]
Abstract
Microbial communities of the urogenital tract have long been recognised to play an important role in disease states. A revolution in methodological approaches is permitting the assessment of complex urogenital tract microbiota-host interactions and the metabolic and protein milieu of the mucosal interface. There is now great potential for significant advances in biomarker discovery and disease risk stratification, and for the elucidation of mechanisms underpinning the microbial community dynamics involved in urogenital tract pathology. Microbiota-host interactions in the female genital tract have a particular significance, because unlike in the male, there is direct communication between the external genitalia, the uterus and the peritoneal cavity. This review examines the microbial community composition at differing sites of the female urogenital tract and its relationship with health and disease. Key factors involved in the modulation of vaginal microbiome stability and structure, such as endocrine, immune and inflammatory pathways, are considered in the context of a woman's life cycle and disease pathogenesis.
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12
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Antonovics J, Wilson AJ, Forbes MR, Hauffe HC, Kallio ER, Leggett HC, Longdon B, Okamura B, Sait SM, Webster JP. The evolution of transmission mode. Philos Trans R Soc Lond B Biol Sci 2017; 372:rstb.2016.0083. [PMID: 28289251 PMCID: PMC5352810 DOI: 10.1098/rstb.2016.0083] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/05/2016] [Indexed: 12/31/2022] Open
Abstract
This article reviews research on the evolutionary mechanisms leading to different transmission modes. Such modes are often under genetic control of the host or the pathogen, and often in conflict with each other via trade-offs. Transmission modes may vary among pathogen strains and among host populations. Evolutionary changes in transmission mode have been inferred through experimental and phylogenetic studies, including changes in transmission associated with host shifts and with evolution of the unusually complex life cycles of many parasites. Understanding the forces that determine the evolution of particular transmission modes presents a fascinating medley of problems for which there is a lack of good data and often a lack of conceptual understanding or appropriate methodologies. Our best information comes from studies that have been focused on the vertical versus horizontal transmission dichotomy. With other kinds of transitions, theoretical approaches combining epidemiology and population genetics are providing guidelines for determining when and how rapidly new transmission modes may evolve, but these are still in need of empirical investigation and application to particular cases. Obtaining such knowledge is a matter of urgency in relation to extant disease threats.This article is part of the themed issue 'Opening the black box: re-examining the ecology and evolution of parasite transmission'.
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Affiliation(s)
- Janis Antonovics
- Department of Biology, University of Virginia, Charlottesville, VA 22904, USA
| | - Anthony J Wilson
- Integrative Entomology group, Vector-borne Viral Diseases programme, The Pirbright Institute, Pirbright GU24 0NF, UK
| | - Mark R Forbes
- Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario, Canada K1S 5B7
| | - Heidi C Hauffe
- Department of Biodiversity and Molecular Ecology, Research and Innovation Centre, Fondazione Edmund Mach, Via E. Mach 1, 38010 S. Michele all'Adige, Trentino, Italy
| | - Eva R Kallio
- Department of Biological and Environmental Science, University of Jyvaskyla, PO Box 35, 40014 Jyvaskyla, Finland.,Department of Ecology, University of Oulu, PO Box 3000, 90014 Oulu, Finland
| | - Helen C Leggett
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, UK
| | - Ben Longdon
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Cornwall TR10 9FE, UK
| | - Beth Okamura
- Department of Life Sciences, Natural History Museum, Cromwell Road, London SW5 7BD, UK
| | - Steven M Sait
- School of Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Joanne P Webster
- Department of Pathology and Pathogen Biology, Centre for Emerging, Endemic and Exotic Diseases, Royal Veterinary College, University of London, London AL9 7TA, UK
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13
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Ecological and evolutionary approaches to managing honeybee disease. Nat Ecol Evol 2017; 1:1250-1262. [PMID: 29046562 PMCID: PMC5749923 DOI: 10.1038/s41559-017-0246-z] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Accepted: 06/20/2017] [Indexed: 12/12/2022]
Abstract
Honeybee declines are a serious threat to global agricultural security and productivity. Although multiple factors contribute to these declines, parasites are a key driver. Disease problems in honeybees have intensified in recent years, despite increasing attention to addressing them. Here we argue that we must focus on the principles of disease ecology and evolution to understand disease dynamics, assess the severity of disease threats, and control these threats via honeybee management. We cover the ecological context of honeybee disease, including both host and parasite factors driving current transmission dynamics, and then discuss evolutionary dynamics including how beekeeping management practices may drive selection for more virulent parasites. We then outline how ecological and evolutionary principles can guide disease mitigation in honeybees, including several practical management suggestions for addressing short- and long-term disease dynamics and consequences. Multiple interacting factors have contributed to the rapid decline of honeybee populations worldwide. Here, the authors review the impact of parasites and pathogens, and how ecological and evolutionary principles can guide management practices.
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14
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Mariën J, Borremans B, Gryseels S, Soropogui B, De Bruyn L, Bongo GN, Becker-Ziaja B, de Bellocq JG, Günther S, Magassouba N, Leirs H, Fichet-Calvet E. No measurable adverse effects of Lassa, Morogoro and Gairo arenaviruses on their rodent reservoir host in natural conditions. Parasit Vectors 2017; 10:210. [PMID: 28449693 PMCID: PMC5408478 DOI: 10.1186/s13071-017-2146-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Accepted: 04/19/2017] [Indexed: 01/11/2023] Open
Abstract
BACKGROUND In order to optimize net transmission success, parasites are hypothesized to evolve towards causing minimal damage to their reservoir host while obtaining high shedding rates. For many parasite species however this paradigm has not been tested, and conflicting results have been found regarding the effect of arenaviruses on their rodent host species. The rodent Mastomys natalensis is the natural reservoir host of several arenaviruses, including Lassa virus that is known to cause Lassa haemorrhagic fever in humans. Here, we examined the effect of three arenaviruses (Gairo, Morogoro and Lassa virus) on four parameters of wild-caught Mastomys natalensis: body mass, head-body length, sexual maturity and fertility. After correcting for the effect of age, we compared these parameters between arenavirus-positive (arenavirus RNA or antibody) and negative animals using data from different field studies in Guinea (Lassa virus) and Tanzania (Morogoro and Gairo viruses). RESULTS Although the sample sizes of our studies (1297, 749 and 259 animals respectively) were large enough to statistically detect small differences in body conditions, we did not observe any adverse effects of these viruses on Mastomys natalensis. We did find that sexual maturity was significantly positively related with Lassa virus antibody presence until a certain age, and with Gairo virus antibody presence in general. Gairo virus antibody-positive animals were also significantly heavier and larger than antibody-free animals. CONCLUSION Together, these results suggest that the pathogenicity of arenaviruses is not severe in M. natalensis, which is likely to be an adaptation of these viruses to optimize transmission success. They also suggest that sexual behaviour might increase the probability of M. natalensis to become infected with arenaviruses.
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Affiliation(s)
- Joachim Mariën
- Evolutionary Ecology Group, University of Antwerp, Antwerp, Belgium
| | - Benny Borremans
- Evolutionary Ecology Group, University of Antwerp, Antwerp, Belgium
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, USA
| | - Sophie Gryseels
- Evolutionary Ecology Group, University of Antwerp, Antwerp, Belgium
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, USA
| | - Barré Soropogui
- Projet des Fièvre Hémorragiques en Guinée, Hôpital Donka, Conakry, Guinea
| | - Luc De Bruyn
- Evolutionary Ecology Group, University of Antwerp, Antwerp, Belgium
| | - Gédéon Ngiala Bongo
- Bernhard-Nocht-Institute for Tropical Medicine, Hamburg, Germany
- Department of Biology, University of Kinshasa, P.O. Box. 190, Kinshasa XI, Democratic Republic of the Congo
| | | | - Joëlle Goüy de Bellocq
- Institute of Vertebrate Biology, Research Facility Studenec, The Czech Academy of Sciences, Brno, Czech Republic
| | - Stephan Günther
- Bernhard-Nocht-Institute for Tropical Medicine, Hamburg, Germany
| | - N’Faly Magassouba
- Projet des Fièvre Hémorragiques en Guinée, Hôpital Donka, Conakry, Guinea
| | - Herwig Leirs
- Evolutionary Ecology Group, University of Antwerp, Antwerp, Belgium
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15
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Chee SP, Khairallah M. Global Variations and Changes in Patterns of Infectious Uveitis. EMERGING INFECTIOUS UVEITIS 2017. [PMCID: PMC7115009 DOI: 10.1007/978-3-319-23416-8_1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Before 1940, most uveitis cases were supposed to be due to infectious agents, mainly syphilis or tuberculosis [1]. Progress in the understanding of intraocular inflammation led to the discovery that uveitis can be of infectious and noninfectious origin and that many pathogens can cause infectious uveitis. Theoretically, Koch postulates must be fulfilled, in order to formerly demonstrate that a disease is due to an infectious agent. However, in infectious uveitis, most often, serological evidence, molecular or histological demonstration, and treatment response are usually the only available elements to suggest the infectious origin of the uveitis. Using those evidences, a large number of infectious organisms have been demonstrated to cause infectious uveitis. Some have a global importance around the world, while others have more limited niches. Many of them have been considered as emerging pathogens.
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Affiliation(s)
| | - Moncef Khairallah
- Department of Ophthalmology, Fattouma Bourguiba University Hospital, Faculty of Medicine, Monastir, Tunisia
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Gall GEC, Lautenschlager S, Bagheri HC. Quarantine as a public health measure against an emerging infectious disease: syphilis in Zurich at the dawn of the modern era (1496-1585). GMS HYGIENE AND INFECTION CONTROL 2016; 11:Doc13. [PMID: 27303653 PMCID: PMC4899769 DOI: 10.3205/dgkh000273] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Syphilis is considered as one of the most devastating sexually transmitted diseases in human history. Based on historical records, the "Böse Blattern" (German for "Evil Pocks") spread through Europe after 1495 and shared symptoms with what we know today as syphilis. Many cities took measures to protect their population. Here, transliterations of archival documents from the 15(th) and 16(th) century (provided in the appendix) are used to trace the steps taken by the governing authorities in Zurich to deal with this emerging infectious disease. One of the central measures taken by the city was to establish a quarantine facility referred to as the "Blatternhaus". The city doctors, including the well-known physician and naturalist Conrad Gessner, oversaw the obligatory quarantine and treatment of patients with symptoms. Treatment could range from better nutrition, herbal remedies and skin ointments to aggressive heat therapy and "smoking". Furthermore, the affliction was suspected as a sexually acquired disease, hence prostitutes and infected foreigners were extradited from the city. Meanwhile, the church used its social influence to promote a more "Christian" behavior. In several respects, the public health measures taken in the 16(th) century against a new and menacing epidemic do not diverge in their basic rationale from approaches used during the 20(th) century and today.
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Affiliation(s)
| | | | - Homayoun C. Bagheri
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, Switzerland
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Abstract
Parasites are thought to play an important role in sexual selection and the evolution of mating strategies, which in turn are likely to be critical to the transmission and therefore the evolution of parasites. Despite this clear interdependence we have little understanding of parasite-mediated sexual selection in the context of reciprocal parasite evolution. Here we develop a general coevolutionary model between host mate preference and the virulence of a sexually transmitted parasite. We show when the characteristics of both the host and parasite lead to coevolutionarily stable strategies or runaway selection, and when coevolutionary cycling between high and low levels of host mate choosiness and virulence is possible. A prominent argument against parasites being involved in sexual selection is that they should evolve to become less virulent when transmission depends on host mating success. The present study, however, demonstrates that coevolution can maintain stable host mate choosiness and parasite virulence or indeed coevolutionary cycling of both traits. We predict that choosiness should vary inversely with parasite virulence and that both relatively long and short life spans select against choosy behavior in the host. The model also reveals that hosts can evolve different behavioral responses from the same initial conditions, which highlights difficulties in using comparative analysis to detect parasite-mediated sexual selection. Taken as a whole, our results emphasize the importance of viewing parasite-mediated sexual selection in the context of coevolution.
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Rushmore J, Allison AB, Edwards EE, Bagal U, Altizer S, Cranfield MR, Glenn TC, Liu H, Mudakikwa A, Mugisha L, Muller MN, Stumpf RM, Thompson ME, Wrangham R, Yabsley MJ. Screening wild and semi-free ranging great apes for putative sexually transmitted diseases: Evidence of Trichomonadidae infections. Am J Primatol 2015; 77:1075-85. [PMID: 26119266 DOI: 10.1002/ajp.22442] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2015] [Accepted: 06/02/2015] [Indexed: 11/07/2022]
Abstract
Sexually transmitted diseases (STDs) can persist endemically, are known to cause sterility and infant mortality in humans, and could have similar impacts in wildlife populations. African apes (i.e., chimpanzees, bonobos, and to a lesser extent gorillas) show multi-male mating behavior that could offer opportunities for STD transmission, yet little is known about the prevalence and impact of STDs in this endangered primate group. We used serology and PCR-based detection methods to screen biological samples from wild and orphaned eastern chimpanzees and gorillas (N = 172 individuals, including adults, and juveniles) for four classes of pathogens that either commonly cause human STDs or were previously detected in captive apes: trichomonads, Chlamydia spp., Treponema pallidum (syphilis and yaws), and papillomaviruses. Based on results from prior modeling and comparative research, we expected STD prevalence to be highest in females versus males and in sexually mature versus immature individuals. All samples were negative for Chlamydia, Treponema pallidum, and papillomaviruses; however, a high percentage of wild chimpanzee urine and fecal samples showed evidence of trichomonads (protozoa). Analysis revealed that females were more likely than males to have positive urine-but not fecal-samples; however, there was no evidence of age (sexual maturity) differences in infection status. Sequence analysis of chimpanzee trichomonad samples revealed a close relationship to previously described trichomonads within the genus Tetratrichomonas. Phylogenetic comparisons to archived sequences from multiple vertebrate hosts suggests that many of the chimpanzee parasites from our study are likely transmitted via fecal-oral contact, but the transmission of some Tetratrichomonas sequence-types remains unknown and could include sexual contact. Our work emphasizes that only a fraction of infectious agents affecting wild apes are presently known to science, and that further work on great ape STDs could offer insights for the management of endangered great apes and for understanding human STD origins.
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Affiliation(s)
- Julie Rushmore
- Odum School of Ecology, The University of Georgia, Athens, Georgia
- College of Veterinary Medicine, The University of Georgia, Athens, Georgia
| | - Andrew B Allison
- Baker Institute for Animal Health, Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, New York
| | - Erin E Edwards
- College of Veterinary Medicine, The University of Georgia, Athens, Georgia
| | - Ujwal Bagal
- Institute of Bioinformatics, The University of Georgia, Athens, Georgia
| | - Sonia Altizer
- Odum School of Ecology, The University of Georgia, Athens, Georgia
| | - Mike R Cranfield
- Gorilla Doctors, Wildlife Health Center, University of California Davis, Davis, California
- The Department of Molecular and Pathobiology, Johns Hopkins School of Medicine, Baltimore, Maryland
| | - Travis C Glenn
- Department of Environmental Health Science, The University of Georgia, Athens, Georgia
| | - Hsi Liu
- National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, Centers for Disease Control, Athens, Georgia
| | - Antoine Mudakikwa
- Rwanda Development Board, Department of Tourism and Conservation, Kigali, Rwanda
| | - Lawrence Mugisha
- Conservation and Ecosystem Health Alliance (CEHA), Kampala, Uganda
- College of Veterinary Medicine, Animal Resources and Biosecurity, Makerere University, Kampala, Uganda
| | - Martin N Muller
- Department of Anthropology, University of New Mexico, Albuquerque, New Mexico
| | - Rebecca M Stumpf
- Department of Anthropology, University of Illinois at Urbana-Champaign, Urbana, Illinois
| | | | - Richard Wrangham
- Department of Human Evolutionary Biology, Harvard University, Cambridge, Massachusetts
| | - Michael J Yabsley
- Warnell School of Forestry and Natural Resources, The University of Georgia and the Southeastern Cooperative Wildlife Disease Study, Department of Population Health, College of Veterinary Medicine, The University of Georgia, Athens, Georgia
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Walker D, Powers N, Connell B, Redfern R. Evidence of skeletal treponematosis from the medieval burial ground of St. Mary Spital, London, and implications for the origins of the disease in Europe. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2014; 156:90-101. [PMID: 25284594 DOI: 10.1002/ajpa.22630] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Revised: 09/17/2014] [Accepted: 09/20/2014] [Indexed: 11/06/2022]
Abstract
Treponematosis is a syndrome of chronic infectious diseases. There has been much debate on its origins and spread, particularly with regard to venereal syphilis, an unsightly and debilitating disease in preantibiotic populations. The osteological analysis of 5,387 individuals excavated by Museum of London Archaeology from the medieval burial ground of St. Mary Spital in London (dated c 1120-1539) provided an unprecedented opportunity to investigate the nature and prevalence of disease over a period of time. Twenty-five individuals were found with suspected treponematosis, originating from all but the earliest period of the burial ground. Descriptions of affected individuals from each period, together with supporting images, are provided. In this work, particular emphasis was given to the distribution of lesions on the skeleton and the variation in patterns by sex and over time. Little change was observed in the distribution of bony change between individuals dated to pre- and post-Columbian periods. However, a dramatic rise in the prevalence of the disease in the final period (c 1400-1539) may reflect documentary reports of a European epidemic from the late 15th century.
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Affiliation(s)
- Don Walker
- Museum of London Archaeology, London, N1 7ED, UK
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Abstract
Lyme disease represents a growing public health threat. The controversial science and politics of Lyme disease have created barriers to reliable diagnosis and effective treatment of this protean illness. Two major clinical hurdles are the absence of a therapeutic end point in treating Borrelia burgdorferi, the spirochetal agent of Lyme disease, and the presence of tickborne coinfections with organisms such as Babesia, Anaplasma, Ehrlichia and Bartonella that may complicate the course of the disease. From a pathophysiologic standpoint, the affinity of Borrelia burgdorferi for multiple cell types and the presence of nonreplicating forms of the Lyme disease spirochete have contributed to persistent infection and failure of simple antibiotic regimens. Newer approaches to the treatment of Lyme disease should take into account its clinical complexity in coinfected patients and the possible need for prolonged combination therapy in patients with persistent symptoms of this potentially debilitating illness. The optimal antibiotic regimen for chronic Lyme disease remains to be determined.
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Affiliation(s)
- Raphael B Stricker
- California Pacific Medical Center , 450 Sutter Street, Suite 1504, San Francisco, CA 94108, USA.
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Butler CD. Infectious disease emergence and global change: thinking systemically in a shrinking world. Infect Dis Poverty 2012; 1:5. [PMID: 23849217 PMCID: PMC3710192 DOI: 10.1186/2049-9957-1-5] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2012] [Accepted: 09/23/2012] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Concern intensifying that emerging infectious diseases and global environmental changes that could generate major future human pandemics. METHOD A focused literature review was undertaken, partly informed by a forthcoming report on environment, agriculture and infectious diseases of poverty, facilitated by the Special Programme for Tropical Diseases. RESULTS More than ten categories of infectious disease emergence exist, but none formally analyse past, current or future burden of disease. Other evidence suggests that the dominant public health concern focuses on two informal groupings. Most important is the perceived threat of newly recognised infections, especially viruses that arise or are newly discovered in developing countries that originate in species exotic to developed countries, such as non-human primates, bats and rodents. These pathogens may be transmitted by insects or bats, or via direct human contact with bushmeat. The second group is new strains of influenza arising from intensively farmed chickens or pigs, or emerging from Asian "wet markets" where several bird species have close contact. Both forms appear justified because of two great pandemics: HIV/AIDS (which appears to have originated from bushmeat hunting in Africa before emerging globally) and Spanish influenza, which killed up to 2.5% of the human population around the end of World War I. Insufficiently appreciated is the contribution of the milieu which appeared to facilitate the high disease burden in these pandemics. Additionally, excess anxiety over emerging infectious diseases diverts attention from issues of greater public health importance, especially: (i) existing (including neglected) infectious diseases and (ii) the changing milieu that is eroding the determinants of immunity and public health, caused by adverse global environmental changes, including climate change and other components of stressed life and civilisation-supporting systems. CONCLUSIONS The focus on novel pathogens and minor forms of anti-microbial resistance in emerging disease literature is unjustified by their burden of disease, actual and potential, and diverts attention from far more important health problems and determinants. There is insufficient understanding of systemic factors that promote pandemics. Adverse global change could generate circumstances conducive to future pandemics with a high burden of disease, arising via anti-microbial and insecticidal resistance, under-nutrition, conflict, and public health breakdown.
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Affiliation(s)
- Colin D Butler
- National Centre for Epidemiology and Population Health College of Medicine Biology and Environment, Australian National University, Canberra, Australia.
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Harper KN, Zuckerman MK, Harper ML, Kingston JD, Armelagos GJ. The origin and antiquity of syphilis revisited: An Appraisal of Old World pre-Columbian evidence for treponemal infection. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2011; 146 Suppl 53:99-133. [DOI: 10.1002/ajpa.21613] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Staves PA, Knell RJ. Virulence and competitiveness: testing the relationship during inter- and intraspecific mixed infections. Evolution 2011; 64:2643-52. [PMID: 20394652 DOI: 10.1111/j.1558-5646.2010.00999.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Understanding the reasons why different parasites cause different degrees of harm to their hosts is an important objective in evolutionary biology. One group of models predicts that if hosts are infected with more than one strain or species of parasite, then competition between the parasites will select for higher virulence. While this idea makes intuitive sense, empirical data to support it are rare and equivocal. We investigated the relationship between fitness and virulence during both inter- and intraspecific competition for a fungal parasite of insects, Metarhizium anisopliae. Contrary to theoretical expectations, competition favored parasite strains with either a lower or a higher virulence depending on the competitor: when in interspecific competition with an entomopathogenic nematode, Steinernema feltiae, less virulent strains of the fungus were more successful, but when competing against conspecific fungi, more virulent strains were better competitors. We suggest that the nature of competition (direct via toxin production when competing against the nematode, indirect via exploitation of the host when competing against conspecific fungal strains) determines the relationship between virulence and competitive ability.
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Affiliation(s)
- Peter A Staves
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London, United Kingdom.
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25
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Farhi D, Dupin N. Origins of syphilis and management in the immunocompetent patient: Facts and controversies. Clin Dermatol 2010; 28:533-8. [DOI: 10.1016/j.clindermatol.2010.03.011] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Abstract
Daniel Turner 1667–1741 was the first English medical author to use the term syphillis incidentally, also mentioning early usage of the condom (condum). This paper shows that venereologists in 18th century London wrote on the use of condoms by some men, but who were sceptical about its usage. This paper also describes some of the contemporary spellings of condum and syphillis.
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Affiliation(s)
- M Waugh
- Nuffield Hospital, Leeds, UK
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27
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Abstract
Should emerging pathogens be unusually virulent? If so, why? Existing theories of virulence evolution based on a tradeoff between high transmission rates and long infectious periods imply that epidemic growth conditions will select for higher virulence, possibly leading to a transient peak in virulence near the beginning of an epidemic. This transient selection could lead to high virulence in emerging pathogens. Using a simple model of the epidemiological and evolutionary dynamics of emerging pathogens, along with rough estimates of parameters for pathogens such as severe acute respiratory syndrome, West Nile virus and myxomatosis, we estimated the potential magnitude and timing of such transient virulence peaks. Pathogens that are moderately evolvable, highly transmissible, and highly virulent at equilibrium could briefly double their virulence during an epidemic; thus, epidemic-phase selection could contribute significantly to the virulence of emerging pathogens. In order to further assess the potential significance of this mechanism, we bring together data from the literature for the shapes of tradeoff curves for several pathogens (myxomatosis, HIV, and a parasite of Daphnia) and the level of genetic variation for virulence for one (myxomatosis). We discuss the need for better data on tradeoff curves and genetic variance in order to evaluate the plausibility of various scenarios of virulence evolution.
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Affiliation(s)
- Benjamin M Bolker
- Department of Biology, University of Florida, Gainesville, FL 32611, USA.
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Tognotti E. The rise and fall of syphilis in Renaissance Europe. THE JOURNAL OF MEDICAL HUMANITIES 2009; 30:99-113. [PMID: 19169798 DOI: 10.1007/s10912-009-9079-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The rapid changes that syphilis underwent after the first major outbreak that occurred in Naples in the mid-1490s are believed to constitute the first well-documented example of a human disease. The new plague was of exceptional virulence, highly contagious and causing severe ulceration at the site of infection. According to medical and other historical sources, the 'genius epidemics' changed some years after this onset, and a slower-progressing form of syphilis seems to have replaced the initial severe form, as do many virulent epidemic infectious diseases that appear in devastating forms in a previously uninfected population. But what exactly were the features of the disease at the moment of its appearance in Europe at the end of the fifteenth century? How many years did it take for the early, virulent form to be replaced and become endemic? What was the pace of these changes through the decades following the onset of the epidemic? In this essay, I review these issues through an analysis of a large number of chronologically-ordered primary historical sources.
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Affiliation(s)
- Eugenia Tognotti
- History of Medicine and Humanities/Medical School, Department of History, University of Sassari(Italy), 07100, Sassari, Italy.
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Ermentrout B, Hastings S. Steady-state analysis of a continuum model for super-infection. J Math Biol 2008; 59:415-38. [PMID: 19002687 DOI: 10.1007/s00285-008-0232-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2008] [Revised: 10/02/2008] [Indexed: 11/25/2022]
Abstract
A large system of N strains of parasite and a single host is analyzed as a function of the degree of virulence in the strains when there is super-infection between hosts (more virulent strains can infect hosts that are already infected) and within-host transition between strains that is neutral. When this small amount of local switching is allowed, steady-state solutions converge to a continuous distribution as the number of strains increases. The resulting nonlinear-nonautonomous integro-differential equation is reduced to a fourth order boundary value problem (BVP) and the existence of positive solutions is proven. The methods here and associated BVP allow for a thorough exploration of parameter space for this class of models.
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Affiliation(s)
- Bard Ermentrout
- Department of Mathematics, University of Pittsburgh, Pittsburgh, PA 15260, USA.
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Abstract
During the rapid spread of HIV-1 in humans, the main (M) group of HIV-1 has evolved into ten distinct subtypes, undergone countless recombination events and diversified extensively. The impact of this extreme genetic diversity on the phenotype of HIV-1 has only recently become a research focus, but early findings indicate that the dominance of HIV-1 subtype C in the current epidemic might be related to the lower virulence of this subtype compared with other subtypes. Here, we explore whether HIV-1 has reached peak virulence or has already started the slow path to attenuation.
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Affiliation(s)
- Kevin K. Ariën
- the Department of Microbiology, HIV and Retrovirology Research Unit, Institute of Tropical Medicine, Nationalestraat 155, Antwerp, B2000 Belgium
- Present Address: the Department of Clinical Chemistry, Microbiology and Immunology, Faculty of Medicine and Health Sciences, Ghent University, De Pintelaan 185, Ghent, B-9000 Belgium
| | - Guido Vanham
- the Department of Microbiology, HIV and Retrovirology Research Unit, Institute of Tropical Medicine, Nationalestraat 155, Antwerp, B2000 Belgium
| | - Eric J. Arts
- the Division of Infectious Diseases, Department of Medicine, Case Western Reserve University, 2109, Adelbert Rd, Cleveland, 44195 Ohio USA
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Cohan FM. Towards a conceptual and operational union of bacterial systematics, ecology, and evolution. Philos Trans R Soc Lond B Biol Sci 2006; 361:1985-96. [PMID: 17062416 PMCID: PMC1764936 DOI: 10.1098/rstb.2006.1918] [Citation(s) in RCA: 161] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
To completely understand the ecology of a bacterial community, we need to identify its ecologically distinct populations (ecotypes). The greatest promise for enumerating a community's constituent ecotypes is held by molecular approaches that identify bacterial ecotypes as DNA sequence clusters. These approaches succeed when ecotypes correspond with sequence clusters, but some models of bacterial speciation predict a one-to-many and others a many-to-one relationship between ecotypes and sequence clusters. A further challenge is that sequence-based phylogenies often contain a hierarchy of clusters and subclusters within clusters, and there is no widely accepted theory to guide systematists and ecologists to the size of cluster most likely to correspond to ecotypes. While present systematics attempts to use universal thresholds of sequence divergence to help demarcate species, the recently developed 'community phylogeny' approach assumes no universal thresholds, but demarcates ecotypes based on the analysis of a lineage's evolutionary dynamics. Theory-based approaches like this one can give a conceptual framework as well as operational criteria for hypothesizing the identity and membership of ecotypes from sequence data; ecology-based approaches can then confirm that the putative ecotypes are actually ecologically distinct. Bacterial ecotypes that are demonstrated to have a history of coexistence as ecologically distinct lineages (based on sequence analysis) and as a prognosis of future coexistence (based on ecological differences), are the fundamental units of bacterial ecology and evolution, and should be recognized by bacterial systematics.
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Affiliation(s)
- Frederick M Cohan
- Department of Biology, Wesleyan University, Middletown, CT 06459-0170, USA.
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