title: Environmental contamination with Toxocara eggs: a quantitative approach to estimate the relative contributions of dogs, cats and foxes, and to assess the efficacy of advised interventions in dogs.
abstract: BACKGROUND
  Environmental contamination with Toxocara eggs is considered the main source of human toxocariasis. The contribution of different groups of hosts to this contamination is largely unknown. Current deworming advices focus mainly on dogs. However, controversy exists about blind deworming regimens for >6-month-old dogs, as most of them do not actually shed Toxocara eggs. We aim to estimate the contribution of different non-juvenile hosts to the environmental Toxocara egg contamination and to assess the effects of different Toxocara-reducing interventions for dogs.
  
  
  METHODS
  A stochastic model was developed to quantify the relative contribution to the environmental contamination with Toxocara eggs of household dogs, household cats, stray cats, and foxes, all older than 6 months in areas with varying urbanization degrees. The model was built upon an existing model developed by Morgan et al. (2013). We used both original and published data on host density, prevalence and intensity of infection, coprophagic behaviour, faeces disposal by owners, and cats' outdoor access. Scenario analyses were performed to assess the expected reduction in dogs' egg output according to different deworming regimens and faeces clean-up compliances. Estimates referred to the Netherlands, a country free of stray dogs.
  
  
  RESULTS
  Household dogs accounted for 39% of the overall egg output of >6-month-old hosts in the Netherlands, followed by stray cats (27%), household cats (19%), and foxes (15%). In urban areas, egg output was dominated by stray cats (81%). Intervention scenarios revealed that only with a high compliance (90%) to the four times a year deworming advice, dogs' contribution would drop from 39 to 28%. Alternatively, when 50% of owners would always remove their dogs' faeces, dogs' contribution would drop to 20%.
  
  
  CONCLUSIONS
  Among final hosts of Toxocara older than 6 months, dogs are the main contributors to the environmental egg contamination, though cats in total (i.e. both owned and stray) transcend this contribution. A higher than expected compliance to deworming advice is necessary to reduce dogs' egg output meaningfully. Actions focusing solely on household dogs and cats are unlikely to sufficiently reduce environmental contamination with eggs, as stray cats and foxes are also important contributors.
authors.affiliation: Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, P.O. box 80.165, 3508 TD, Utrecht, The Netherlands. e.r.nijsse@uu.nl.
authors.forename: Rolf
authors.initials: R
authors.lastname: Nijsse
authors.affiliation: Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, P.O. box 80.165, 3508 TD, Utrecht, The Netherlands. lapo.mughini.gras@rivm.nl.|National Institute for Public Health and the Environment, Centre for Infectious Disease Control, P.O. box 1, Bilthoven, 3720 BA, The Netherlands. lapo.mughini.gras@rivm.nl.
authors.forename: Lapo
authors.initials: L
authors.lastname: Mughini-Gras
authors.affiliation: Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, P.O. box 80.165, 3508 TD, Utrecht, The Netherlands. j.wagenaar@uu.nl.|Central Veterinary Institute of Wageningen UR, Houtribweg 39, 8221 RA, Lelystad, The Netherlands. j.wagenaar@uu.nl.
authors.forename: Jaap A
authors.initials: JA
authors.lastname: Wagenaar
authors.affiliation: National Institute for Public Health and the Environment, Centre for Infectious Disease Control, P.O. box 1, Bilthoven, 3720 BA, The Netherlands. frits.franssen@rivm.nl.
authors.forename: Frits
authors.initials: F
authors.lastname: Franssen
authors.affiliation: Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, P.O. box 80.165, 3508 TD, Utrecht, The Netherlands. h.w.ploeger@uu.nl.
authors.forename: Harm W
authors.initials: HW
authors.lastname: Ploeger
mesh_terms: D000818:Animals; D002371:Cat Diseases / Q000453:epidemiology* / Q000469:parasitology; D002415:Cats; D004283:Dog Diseases / Q000453:epidemiology* / Q000469:parasitology; D004285:Dogs; D004777:Environment; D005243:Feces / Q000469:parasitology; D005260:Female; D005589:Foxes / Q000469:parasitology*; D006801:Humans; D009426:Netherlands / Q000453:epidemiology; D010270:Parasite Egg Count / Q000662:veterinary; D015995:Prevalence; D014119:Toxocara / Q000302:isolation & purification*; D014120:Toxocariasis / Q000453:epidemiology* / Q000469:parasitology