title: Using molecular epidemiology to track Toxoplasma gondii from terrestrial carnivores to marine hosts: implications for public health and conservation.
abstract: BACKGROUND
  Environmental transmission of the zoonotic parasite Toxoplasma gondii, which is shed only by felids, poses risks to human and animal health in temperate and tropical ecosystems. Atypical T. gondii genotypes have been linked to severe disease in people and the threatened population of California sea otters. To investigate land-to-sea parasite transmission, we screened 373 carnivores (feral domestic cats, mountain lions, bobcats, foxes, and coyotes) for T. gondii infection and examined the distribution of genotypes in 85 infected animals sampled near the sea otter range.
  
  
  RESULTS
  Nested PCR-RFLP analyses and direct DNA sequencing at six independent polymorphic genetic loci (B1, SAG1, SAG3, GRA6, L358, and Apico) were used to characterize T. gondii strains in infected animals. Strains consistent with Type X, a novel genotype previously identified in over 70% of infected sea otters and four terrestrial wild carnivores along the California coast, were detected in all sampled species, including domestic cats. However, odds of Type X infection were 14 times higher (95% CI: 1.3-148.6) for wild felids than feral domestic cats. Type X infection was also linked to undeveloped lands (OR = 22, 95% CI: 2.3-250.7). A spatial cluster of terrestrial Type II infection (P = 0.04) was identified in developed lands bordering an area of increased risk for sea otter Type II infection. Two spatial clusters of animals infected with strains consistent with Type X (P ≤ 0.01) were detected in less developed landscapes.
  
  
  CONCLUSIONS
  Differences in T. gondii genotype prevalence among domestic and wild felids, as well as the spatial distribution of genotypes, suggest co-existing domestic and wild T. gondii transmission cycles that likely overlap at the interface of developed and undeveloped lands. Anthropogenic development driving contact between these cycles may increase atypical T. gondii genotypes in domestic cats and facilitate transmission of potentially more pathogenic genotypes to humans, domestic animals, and wildlife.
authors.affiliation: Wildlife Health Center, One Health Institute, School of Veterinary Medicine, University of California, Davis, Davis, California, United States of America.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: VanWormer
authors.affiliation: Wildlife Health Center, One Health Institute, School of Veterinary Medicine, University of California, Davis, Davis, California, United States of America; Marine Wildlife Veterinary Care and Research Center, California Department of Fish and Wildlife, Santa Cruz, California, United States of America.
authors.forename: Melissa A
authors.initials: MA
authors.lastname: Miller
authors.affiliation: Wildlife Health Center, One Health Institute, School of Veterinary Medicine, University of California, Davis, Davis, California, United States of America; Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, Davis, California, United States of America.
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Conrad
authors.affiliation: Laboratory of Parasitic Diseases, National Institutes of Health, National Institute of Allergy and Infectious Diseases (NIAID), Bethesda, Maryland, United States of America.
authors.forename: Michael E
authors.initials: ME
authors.lastname: Grigg
authors.affiliation: Wildlife Health Center, One Health Institute, School of Veterinary Medicine, University of California, Davis, Davis, California, United States of America; Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, Davis, California, United States of America.
authors.forename: Daniel
authors.initials: D
authors.lastname: Rejmanek
authors.affiliation: EpiCentre, Massey University, Palmerston North, New Zealand.
authors.forename: Tim E
authors.initials: TE
authors.lastname: Carpenter
authors.affiliation: Wildlife Health Center, One Health Institute, School of Veterinary Medicine, University of California, Davis, Davis, California, United States of America.
authors.forename: Jonna A K
authors.initials: JA
authors.lastname: Mazet
mesh_terms: D000818:Animals; D002140:California / Q000453:epidemiology; D002335:Carnivora / Q000469:parasitology*; D002415:Cats / Q000469:parasitology; D017720:Molecular Epidemiology; D010041:Otters / Q000469:parasitology; D012307:Risk Factors; D014122:Toxoplasma / Q000145:classification* / Q000235:genetics*; D014124:Toxoplasmosis, Animal / Q000453:epidemiology / Q000469:parasitology / Q000635:transmission