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Crellen T, Haswell M, Sithithaworn P, Sayasone S, Odermatt P, Lamberton PHL, Spencer SEF, Déirdre Hollingsworth T. Diagnosis of helminths depends on worm fecundity and the distribution of parasites within hosts. Proc Biol Sci 2023; 290:20222204. [PMID: 36651047 PMCID: PMC9845982 DOI: 10.1098/rspb.2022.2204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Accepted: 12/16/2022] [Indexed: 01/19/2023] Open
Abstract
Helminth transmission and morbidity are dependent on the number of mature parasites within a host; however, observing adult worms is impossible for many natural infections. An outstanding challenge is therefore relating routine diagnostics, such as faecal egg counts, to the underlying worm burden. This relationship is complicated by density-dependent fecundity (egg output per worm reduces due to crowding at high burdens) and the skewed distribution of parasites (majority of helminths aggregated in a small fraction of hosts). We address these questions for the carcinogenic liver fluke Opisthorchis viverrini, which infects approximately 10 million people across Southeast Asia, by analysing five epidemiological surveys (n = 641) where adult flukes were recovered. Using a mechanistic model, we show that parasite fecundity varies between populations, with surveys from Thailand and Laos demonstrating distinct patterns of egg output and density-dependence. As the probability of observing faecal eggs increases with the number of mature parasites within a host, we quantify diagnostic sensitivity as a function of the worm burden and find that greater than 50% of cases are misdiagnosed as false negative in communities close to elimination. Finally, we demonstrate that the relationship between observed prevalence from routine diagnostics and true prevalence is nonlinear and strongly influenced by parasite aggregation.
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Affiliation(s)
- Thomas Crellen
- School of Biodiversity One Health and Veterinary Medicine, Graham Kerr Building, University of Glasgow, 82 Hillhead Street, Glasgow G12 8QQ, UK
- Wellcome Centre for Integrative Parasitology, Sir Graeme Davies Building, University of Glasgow, 120 University Place, Glasgow G12 8TA, UK
- Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford OX3 7LF, UK
| | - Melissa Haswell
- Office of the Deputy Vice Chancellor, Indigenous Strategy and Services and School of Geosciences, John Woolley Building, University of Sydney, Sydney, New South Wales 2050, Australia
- School of Public Health and Social Work, Kelvin Grove Campus, Queensland University of Technology, Brisbane City, Queensland 4000, Australia
| | - Paiboon Sithithaworn
- Department of Parasitology, Khon Kaen University, 123 Thanon Mittraphap, Khon Kaen 40002, Thailand
| | - Somphou Sayasone
- Lao Tropical and Public Health Institute, Samsenthai Road, Sisattanak district, Vientiane, Lao PDR
| | - Peter Odermatt
- Department of Public Health and Epidemiology, Swiss Tropical and Public Health Institute, Kreuzstrasse 2, Allschwil 4123, Switzerland
- University of Basel, Petersplatz 1, Basel 4001, Switzerland
| | - Poppy H. L. Lamberton
- School of Biodiversity One Health and Veterinary Medicine, Graham Kerr Building, University of Glasgow, 82 Hillhead Street, Glasgow G12 8QQ, UK
- Wellcome Centre for Integrative Parasitology, Sir Graeme Davies Building, University of Glasgow, 120 University Place, Glasgow G12 8TA, UK
| | | | - T. Déirdre Hollingsworth
- Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford OX3 7LF, UK
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Liu JH, Liu DY, Yuan YF, Sun XJ, Shan SM. Comparison of the performance of MS enteroscope series and Japanese double- and single-balloon enteroscopes. World J Gastroenterol 2022; 28:1329-1337. [PMID: 35645541 PMCID: PMC9099188 DOI: 10.3748/wjg.v28.i13.1329] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Revised: 11/29/2021] [Accepted: 02/23/2022] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Small intestine disease endangers human health and is not easy to locate and diagnose.
AIM To observe the effect of the MS series of small intestine endoscopes on the gastrointestinal tract, the changes in serum gastrin levels and intestinal tissue, and the time required for the examination.
METHODS In vivo experiments in 20 Living pigs were conducted, Bowel preparation was routinely performed, Intravenous anesthesia with propofol and ketamine was applied, the condition of the small intestine was observed and the detection time of the MS series of small intestine endoscopes were recorded, The changes in intestinal tissue using the MS series of small intestine endoscopes observed and compared before and after the examination, Venous blood (3-5 mL) from pigs was collected before and after the experiment; changes in intestinal tissue after use of the MS series of small intestine endoscopes observed after examination. After completion of each type of small intestine endoscope experiment, the pigs were allowed to rest and the next type of small intestine endoscope experiment was performed after 15 days of normal feeding. The detection time data of the single-balloon small intestine endoscope and double-balloon small intestine endoscope were collected from four hospitals.
RESULTS One case of Ascarislumbricoides, one of suspected Crohn's disease, one small intestinal diverticulum and one anesthesia accident were observed in pigs. The small intestine showed no differences in the MS series of small intestine endoscopes and there were no differences in serum gastrin between the groups (P > 0.05). The time required for inspection was recorded, and the overall detection time for the Japanese small intestine endoscopes was approximately 1.68 ± 0.16 h.
CONCLUSION Intestinal ascariasis is a common disease in pigs. Some pigs have abnormal intestinal variation. After continuous upgrade and improvement, the MS-3 and MS-4 small intestine endoscope appear superior in terms of detection time.
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Affiliation(s)
- Jin-Hua Liu
- Department of General Surgery, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an 710061, Shaanxi Province, China
- Department of General Surgery, Affiliated Dalian Municipal Friendship Hospital of Dalian Medical University, Dalian 116001, Liaoning Province, China
| | - Dan-Yang Liu
- Department of Endocrinology, Affiliated Dalian Municipal Friendship Hospital of Dalian Medical University, Dalian 116001, Liaoning Province, China
| | - Yong-Feng Yuan
- College of Computer Science and Technology, Harbin Institute of Technology, Harbin 150001, Heilongjiang Province, China
| | - Xue-Jun Sun
- Department of General Surgery, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an 710061, Shaanxi Province, China
| | - Shu-Mei Shan
- General Manager Office, Dalian Ming Sheng Technology Development Co., Ltd., Dalian 116001, Liaoning Province, China
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Retkute R, Touloupou P, Basáñez MG, Hollingsworth TD, Spencer SEF. Integrating geostatistical maps and infectious disease transmission models using adaptive multiple importance sampling. Ann Appl Stat 2021. [DOI: 10.1214/21-aoas1486] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Affiliation(s)
- Renata Retkute
- Epidemiology and Modelling Group, Department of Plant Sciences, University of Cambridge
| | | | - María-Gloria Basáñez
- London Centre for Neglected Tropical Disease Research and MRC Centre for Global Infectious Disease Analysis, Faculty of Medicine, School of Public Health, Imperial College London
| | - T. Déirdre Hollingsworth
- Big Data Institute, Li Ka Shing Centre for Health, Information and Discovery, University of Oxford
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Wilber MQ, Pfab F, Ohmer ME, Briggs CJ. Integrating Infection Intensity into Within- and Between-Host Pathogen Dynamics: Implications for Invasion and Virulence Evolution. Am Nat 2021; 198:661-677. [PMID: 34762573 DOI: 10.1086/716914] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
AbstractInfection intensity can dictate disease outcomes but is typically ignored when modeling infection dynamics of microparasites (e.g., bacteria, virus, and fungi). However, for a number of pathogens of wildlife typically categorized as microparasites, accounting for infection intensity and within-host infection processes is critical for predicting population-level responses to pathogen invasion. Here, we develop a modeling framework we refer to as reduced-dimension host-parasite integral projection models (reduced IPMs) that we use to explore how within-host infection processes affect the dynamics of pathogen invasion and virulence evolution. We find that individual-level heterogeneity in pathogen load-a nearly ubiquitous characteristic of host-parasite interactions that is rarely considered in models of microparasites-generally reduces pathogen invasion probability and dampens virulence-transmission trade-offs in host-parasite systems. The latter effect likely contributes to widely predicted virulence-transmission trade-offs being difficult to observe empirically. Moreover, our analyses show that intensity-dependent host mortality does not always induce a virulence-transmission trade-off, and systems with steeper than linear relationships between pathogen intensity and host mortality rate are significantly more likely to exhibit these trade-offs. Overall, reduced IPMs provide a useful framework to expand our theoretical and data-driven understanding of how within-host processes affect population-level disease dynamics.
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Abstract
This paper addresses the problem of extinction in continuous models of population dynamics associated with small numbers of individuals. We begin with an extended discussion of extinction in the particular case of a stochastic logistic model, and how it relates to the corresponding continuous model. Two examples of ‘small number dynamics’ are then considered. The first is what Mollison calls the ‘atto-fox’ problem (in a model of fox rabies), referring to the problematic theoretical occurrence of a predicted rabid fox density of \documentclass[12pt]{minimal}
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\begin{document}$$10^{-18}$$\end{document}10-18 (atto-) per square kilometre. The second is how the production of large numbers of eggs by an individual can reliably lead to the eventual survival of a handful of adults, as it would seem that extinction then becomes a likely possibility. We describe the occurrence of the atto-fox problem in other contexts, such as the microbial ‘yocto-cell’ problem, and we suggest that the modelling resolution is to allow for the existence of a reservoir for the extinctively challenged individuals. This is functionally similar to the concept of a ‘refuge’ in predator–prey systems and represents a state for the individuals in which they are immune from destruction. For what I call the ‘frogspawn’ problem, where only a few individuals survive to adulthood from a large number of eggs, we provide a simple explanation based on a Holling type 3 response and elaborate it by means of a suitable nonlinear age-structured model.
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Affiliation(s)
- A C Fowler
- MACSI, University of Limerick, Limerick, Ireland.
- OCIAM, University of Oxford, Oxford, UK.
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Davis EL, Reimer LJ, Pellis L, Hollingsworth TD. Evaluating the Evidence for Lymphatic Filariasis Elimination. Trends Parasitol 2019; 35:860-869. [PMID: 31506245 PMCID: PMC7413036 DOI: 10.1016/j.pt.2019.08.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Revised: 08/19/2019] [Accepted: 08/19/2019] [Indexed: 12/01/2022]
Abstract
In the global drive for elimination of lymphatic filariasis (LF), 15 countries have achieved validation of elimination as a public health problem (EPHP). Recent empirical evidence has demonstrated that EPHP does not always lead to elimination of transmission (EOT). Here we show how the probability of elimination explicitly depends on key biological parameters, many of which have been poorly characterized, leading to a poor evidence base for the elimination threshold. As more countries progress towards EPHP it is essential that this process is well-informed, as prematurely halting treatment and surveillance programs could pose a serious threat to global progress. We highlight that refinement of the weak empirical evidence base is vital to understand drivers of elimination and inform long-term policy.
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Affiliation(s)
| | - Lisa J Reimer
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
| | - Lorenzo Pellis
- University of Manchester, Oxford Road, Manchester M13 9PL, UK
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do Nascimento Ramos IC, Ramos RAN, Giannelli A, Lima VFS, Cringoli G, Rinaldi L, de Carvalho GA, Alves LC. An Additional Asset for the FLOTAC Technique: Detection of Gastrointestinal Parasites in Vegetables. Acta Parasitol 2019; 64:423-425. [PMID: 31069644 DOI: 10.2478/s11686-019-00059-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Accepted: 03/29/2019] [Indexed: 11/21/2022]
Abstract
INTRODUCTION Gastrointestinal parasites are considered amongst the most important threats to veterinary and human health worldwide. The transmission of these parasitic diseases usually involves the accidental ingestion of oocysts, cysts, eggs, and larvae, whose detection is generally achieved by classical coproparasitological methods, based on sedimentation and/or flotation techniques. These procedures might be inefficient or display a low sensitivity when performed on food matrices. This study aimed to assess the value of the FLOTAC technique for the detection of different parasitic stages of gastrointestinal parasites of domestic animals in fresh lettuce. MATERIAL AND METHODS Samples (n = 100) were purchased from public markets located in the metropolitan region of Recife (Brazil). RESULTS A total of 79% scored positive for eggs and/or cysts of gastrointestinal parasites. Protozoa and nematodes were detected in 32% (32/100) and 64% (64/100) of samples, respectively, with cysts of the genus Entamoeba (32%) and eggs of nematodes of the order Strongylida (30%) being the most frequently diagnosed. CONCLUSIONS The findings herein reported demonstrate that the FLOTAC technique can be successfully applied for recovering food-borne parasites of medical and veterinary concern in food matrices.
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Affiliation(s)
| | - Rafael Antonio Nascimento Ramos
- Academic Unit of Garanhuns, Federal Rural University of Pernambuco, Av. Bom Pastor, s/n, Boa Vista, Garanhuns, Pernambuco, CEP 55292-270, Brazil.
| | | | | | - Giuseppe Cringoli
- Department of Veterinary Medicine and Animal Productions, University of Napoli Federico II, Naples, Italy
| | - Laura Rinaldi
- Department of Veterinary Medicine and Animal Productions, University of Napoli Federico II, Naples, Italy
| | - Gílcia Aparecida de Carvalho
- Academic Unit of Garanhuns, Federal Rural University of Pernambuco, Av. Bom Pastor, s/n, Boa Vista, Garanhuns, Pernambuco, CEP 55292-270, Brazil
| | - Leucio Câmara Alves
- Department of Veterinary Medicine, Federal Rural University of Pernambuco, Recife, Brazil
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Cooper AJ, Hollingsworth TD. The impact of seasonality on the dynamics and control of Ascaris lumbricoides infections. J Theor Biol 2018; 453:96-107. [PMID: 29800536 PMCID: PMC6013298 DOI: 10.1016/j.jtbi.2018.05.025] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Revised: 05/09/2018] [Accepted: 05/21/2018] [Indexed: 11/24/2022]
Abstract
Intestinal nematode infections affect a huge proportion of the world's population. Increasingly these infections, particularly amongst the poorest communities, are controlled through mass drug treatment programs. Seasonal variations of climate and behaviour in these regions can be significant, but their impact on the dynamics of infection and implications for the effectiveness of any mass drug treatment program (a pulsed reduction in worm burden in hosts) is not clearly understood. Here the effect of seasonality on the dynamics of the soil-based helminth, Ascaris lumbricoides, is investigated using a reformulated version of the Anderson-May model for macro-parasitic infections. Explicit analytical expressions are obtained for the stable oscillatory solution over the annual cycle, which provides a means of relating times of peak numbers of eggs, larvae and mature worms to seasonal variations. Numerical and analytical techniques are then used to consider the impact of seasonality on the optimal timing of drug treatment. Our results show that there is a relatively large window for the timing of optimal treatment, and the impact of repeated annual mass drug treatments can be substantially improved if they are timed to coincide with the months when the number of eggs and larvae are at their lowest - minimising reinfection. In terms of a more measurable quantity, in our example this corresponds to the months when the seasonal temperature is highest. Multiple annual treatments at (or close to) the optimal time each year are predicted to achieve local elimination in the community, whereas treatment at other times has a more limited impact. A key finding is that even for pronounced seasonality, perturbations in mean worm burden, and hence seasonal variation in observed egg output, may be small, potentially explaining why seasonal effects have been overlooked. Taken together these results suggest that seasonality of soil-transmitted helminths requires further experimental, field and mathematical study if the impact for mass drug administration programs is to be exploited.
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Affiliation(s)
- A J Cooper
- Zeeman Institute for Systems Biology and Infectious Disease Epidemiology Research, University of Warwick, Coventry CV4 7AL, UK.
| | - T Déirdre Hollingsworth
- Zeeman Institute for Systems Biology and Infectious Disease Epidemiology Research, University of Warwick, Coventry CV4 7AL, UK; Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford OX1 2JD, UK
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9
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Davis EL, Danon L, Prada JM, Gunawardena SA, Truscott JE, Vlaminck J, Anderson RM, Levecke B, Morgan ER, Hollingsworth TD. Seasonally timed treatment programs for Ascaris lumbricoides to increase impact-An investigation using mathematical models. PLoS Negl Trop Dis 2018; 12:e0006195. [PMID: 29346383 PMCID: PMC5773001 DOI: 10.1371/journal.pntd.0006195] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2017] [Accepted: 12/27/2017] [Indexed: 11/19/2022] Open
Abstract
There is clear empirical evidence that environmental conditions can influence Ascaris spp. free-living stage development and host reinfection, but the impact of these differences on human infections, and interventions to control them, is variable. A new model framework reflecting four key stages of the A. lumbricoides life cycle, incorporating the effects of rainfall and temperature, is used to describe the level of infection in the human population alongside the environmental egg dynamics. Using data from South Korea and Nigeria, we conclude that settings with extreme fluctuations in rainfall or temperature could exhibit strong seasonal transmission patterns that may be partially masked by the longevity of A. lumbricoides infections in hosts; we go on to demonstrate how seasonally timed mass drug administration (MDA) could impact the outcomes of control strategies. For the South Korean setting the results predict a comparative decrease of 74.5% in mean worm days (the number of days the average individual spend infected with worms across a 12 month period) between the best and worst MDA timings after four years of annual treatment. The model found no significant seasonal effect on MDA in the Nigerian setting due to a narrower annual temperature range and no rainfall dependence. Our results suggest that seasonal variation in egg survival and maturation could be exploited to maximise the impact of MDA in certain settings.
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Affiliation(s)
- Emma L. Davis
- Department of Mathematics, University of Warwick, Coventry, UK
- * E-mail:
| | - Leon Danon
- Data Science Institute, College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, UK
| | - Joaquín M. Prada
- Department of Mathematics, University of Warwick, Coventry, UK
- Faculty of Health & Medical Sciences, University of Surrey, Guildford, UK
| | | | - James E. Truscott
- Department of Infectious Disease Epidemiology, School of Public Health, Imperial College London, London, UK
| | - Johnny Vlaminck
- Department of Virology, Parasitology and Immunology, Ghent University, Merelbeke, Belgium
| | - Roy M. Anderson
- Department of Infectious Disease Epidemiology, School of Public Health, Imperial College London, London, UK
| | - Bruno Levecke
- Department of Virology, Parasitology and Immunology, Ghent University, Merelbeke, Belgium
| | - Eric R Morgan
- Institute for Global Food Security, School of Biological Sciences, Queen’s University, Belfast, UK
- School of Veterinary Science, University of Bristol, Langford, UK
| | - T. Deirdre Hollingsworth
- Department of Mathematics, University of Warwick, Coventry, UK
- School of Life Sciences, University of Warwick, Coventry, UK
- Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, UK
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Wilber MQ, Johnson PTJ, Briggs CJ. When can we infer mechanism from parasite aggregation? A constraint-based approach to disease ecology. Ecology 2017; 98:688-702. [PMID: 27935638 DOI: 10.1002/ecy.1675] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Revised: 10/05/2016] [Accepted: 11/29/2016] [Indexed: 11/09/2022]
Abstract
Few hosts have many parasites while many hosts have few parasites. This axiom of macroparasite aggregation is so pervasive it is considered a general law in disease ecology, with important implications for the dynamics of host-parasite systems. Because of these dynamical implications, a significant amount of work has explored both the various mechanisms leading to parasite aggregation patterns and how to infer mechanism from these patterns. However, as many disease mechanisms can produce similar aggregation patterns, it is not clear whether aggregation itself provides any additional information about mechanism. Here we apply a "constraint-based" approach developed in macroecology that allows us to explore whether parasite aggregation contains any additional information beyond what is provided by mean parasite load. We tested two constraint-based null models, both of which were constrained on the total number of parasites P and hosts H found in a sample, using data from 842 observed amphibian host-trematode parasite distributions. We found that constraint-based models captured ~85% of the observed variation in host-parasite distributions, suggesting that the constraints P and H contain much of the information about the shape of the host-parasite distribution. However, we also found that extending the constraint-based null models can identify the potential role of known aggregating mechanisms (such as host heterogeneity) and disaggregating mechanisms (such as parasite-induced host mortality) in constraining host-parasite distributions. Thus, by providing robust null models, constraint-based approaches can help guide investigations aimed at detecting biological processes that directly affect parasite aggregation above and beyond those that indirectly affect aggregation through P and H.
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Affiliation(s)
- Mark Q Wilber
- University of California, Santa Barbara, Santa Barbara, California, 93106, USA
| | | | - Cheryl J Briggs
- University of California, Santa Barbara, Santa Barbara, California, 93106, USA
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