title: Meta-analysis to estimate the load of Leptospira excreted in urine: beyond rats as important sources of transmission in low-income rural communities.
abstract: BACKGROUND
  Leptospirosis is a major zoonotic disease with widespread distribution and a large impact on human health. Carrier animals excrete pathogenic Leptospira primarily in their urine. Infection occurs when the pathogen enters a host through mucosa or small skin abrasions. Humans and other animals are exposed to the pathogen by direct contact with urine, contaminated soil or water. While many factors influence environmental cycling and the transmission of Leptospira to humans, the load of pathogenic Leptospira in the environment is likely to play a major role. Peridomestic rats are often implicated as a potential source of human disease; however exposure to other animals is a risk factor as well. The aim of this report is to highlight the importance of various carrier animals in terms of the quantity of Leptospira shed into the environment. For this, we performed a systematic literature review and a meta-analysis of the amount of pathogen that various animal species shed in their urine.
  
  
  RESULTS
  The quantity of pathogen has been reported for cows, deer, dogs, humans, mice, and rats, in a total of 14 research articles. We estimated the average Leptospira per unit volume shed by each animal species, and the daily environmental contribution by considering the total volume of urine excreted by each carrier animal. Rats excrete the highest quantity of Leptospira per millilitre of urine (median = 5.7 × 106cells), but large mammals excrete much more urine and thus shed significantly more Leptospira per day (5.1 × 108to 1.3 × 109cells).
  
  
  CONCLUSIONS
  Here we illustrate how, in a low-income rural Ecuadorian community, host population demographics, and prevalence of Leptospira infection can be integrated with estimates of shed Leptospira to suggest that peridomestic cattle may be more important than rats in environmental cycling and ultimately, transmission to humans.
authors.affiliation: Pathogen & Microbiome Institute, Northern Arizona University, Flagstaff, AZ, 86011-4073, USA.|Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ, 86011-5640, USA.|Instituto de Microbiologia, Colegio de Ciencias Biologicas y Ambientales, Universidad San Francisco de Quito, Quito, Ecuador.
authors.forename: Veronica
authors.initials: V
authors.lastname: Barragan
authors.affiliation: Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ, 86011-5640, USA.
authors.forename: Nathan
authors.initials: N
authors.lastname: Nieto
authors.affiliation: Pathogen & Microbiome Institute, Northern Arizona University, Flagstaff, AZ, 86011-4073, USA.|Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ, 86011-5640, USA.
authors.forename: Paul
authors.initials: P
authors.lastname: Keim
authors.affiliation: Pathogen & Microbiome Institute, Northern Arizona University, Flagstaff, AZ, 86011-4073, USA. talima.pearson@nau.edu.|Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ, 86011-5640, USA. talima.pearson@nau.edu.
authors.forename: Talima
authors.initials: T
authors.lastname: Pearson
mesh_terms: D000818:Animals; D002417:Cattle; D003670:Deer; D004285:Dogs; D004484:Ecuador; D006801:Humans; D007919:Leptospira / Q000302:isolation & purification*; D007922:Leptospirosis / Q000453:epidemiology*; D051379:Mice; D011203:Poverty / Q000706:statistics & numerical data*; D051381:Rats; D012424:Rural Population / Q000706:statistics & numerical data*; D015047:Zoonoses / Q000453:epidemiology*
keywords: Animal reservoirs; Leptospira; Transmission; Urine