title: Impact of the shedding level on transmission of persistent infections in Mycobacterium avium subspecies paratuberculosis (MAP).
abstract: Super-shedders are infectious individuals that contribute a disproportionate amount of infectious pathogen load to the environment. A super-shedder host may produce up to 10,000 times more pathogens than other infectious hosts. Super-shedders have been reported for multiple human and animal diseases. If their contribution to infection dynamics was linear to the pathogen load, they would dominate infection dynamics. We here focus on quantifying the effect of super-shedders on the spread of infection in natural environments to test if such an effect actually occurs in Mycobacterium avium subspecies paratuberculosis (MAP). We study a case where the infection dynamics and the bacterial load shed by each host at every point in time are known. Using a maximum likelihood approach, we estimate the parameters of a model with multiple transmission routes, including direct contact, indirect contact and a background infection risk. We use longitudinal data from persistent infections (MAP), where infectious individuals have a wide distribution of infectious loads, ranging upward of three orders of magnitude. We show based on these parameters that the effect of super-shedders for MAP is limited and that the effect of the individual bacterial load is limited and the relationship between bacterial load and the infectiousness is highly concave. A 1000-fold increase in the bacterial contribution is equivalent to up to a 2-3 fold increase in infectiousness.
authors.affiliation: Gonda Brain Research Center, Bar-Ilan University, Ramat Gan, Israel. noa.slater@gmail.com.
authors.forename: Noa
authors.initials: N
authors.lastname: Slater
authors.affiliation: Department of Population Medicine and Diagnostic Sciences, Cornell University, Ithaca, NY, USA. rmm257@gmail.com.|Department of Mathematics and Computer Science, Emory University, Atlanta, GA, USA. rmm257@gmail.com.
authors.forename: Rebecca Mans
authors.initials: RM
authors.lastname: Mitchell
authors.affiliation: New Bolton Center, University of Pennsylvania, Kennett Square, Philadelphia, PA, USA. rhw@vet.upenn.edu.
authors.forename: Robert H
authors.initials: RH
authors.lastname: Whitlock
authors.affiliation: New Bolton Center, University of Pennsylvania, Kennett Square, Philadelphia, PA, USA. tfyock@vet.upenn.edu.
authors.forename: Terry
authors.initials: T
authors.lastname: Fyock
authors.affiliation: Department of Nutrition and Food Science, Center for Food Safety and Security Systems, University of Maryland, College Park, College Park, MD, USA. akp@umd.edu.
authors.forename: Abani Kumar
authors.initials: AK
authors.lastname: Pradhan
authors.affiliation: Utrecht University, Utrecht, The Netherlands. eknupfer85@gmail.com.
authors.forename: Elena
authors.initials: E
authors.lastname: Knupfer
authors.affiliation: Department of Population Medicine and Diagnostic Sciences, Cornell University, Ithaca, NY, USA. y.schukken@gdanimalhealth.com.|GD Animal Health, Deventer, The Netherlands. y.schukken@gdanimalhealth.com.|Department of Animal Sciences, Wageningen University, Wageningen, The Netherlands. y.schukken@gdanimalhealth.com.
authors.forename: Ynte Hein
authors.initials: YH
authors.lastname: Schukken
authors.affiliation: Gonda Brain Research Center, Bar-Ilan University, Ramat Gan, Israel. louzouy@math.biu.ac.il.|Department of Mathematics, Bar-Ilan University, Ramat Gan, Israel. louzouy@math.biu.ac.il.
authors.forename: Yoram
authors.initials: Y
authors.lastname: Louzoun
mesh_terms: D000818:Animals; D057138:Bacterial Shedding; D002417:Cattle; D002418:Cattle Diseases / Q000382:microbiology / Q000635:transmission*; D003612:Dairying; D005243:Feces / Q000382:microbiology; D005260:Female; D016013:Likelihood Functions; D008137:Longitudinal Studies; D008962:Models, Theoretical; D016927:Mycobacterium avium subsp. paratuberculosis / Q000502:physiology*; D009518:New York; D010283:Paratuberculosis / Q000382:microbiology / Q000635:transmission*; D010414:Pennsylvania; D014707:Vermont