title: Population genetics of Schistosoma japonicum within the Philippines suggest high levels of transmission between humans and dogs.
abstract: BACKGROUND
  Schistosoma japonicum, which remains a major public health problem in the Philippines and mainland China, is the only schistosome species for which zoonotic transmission is considered important. While bovines are suspected as the main zoonotic reservoir in parts of China, the relative contributions of various non-human mammals to S. japonicum transmission in the Philippines remain to be determined. We examined the population genetics of S. japonicum in the Philippines in order to elucidate transmission patterns across host species and geographic areas.
  
  
  RESULTS
  S. japonicum miracidia (hatched from eggs within fecal samples) from humans, dogs, pigs and rats, and cercariae shed from snail-intermediate hosts, were collected across two geographic areas of Samar Province. Individual isolates were then genotyped using seven multiplexed microsatellite loci. Wright's F(ST) values and phylogenetic trees calculated for parasite populations suggest a high frequency of parasite gene-flow across definitive host species, particularly between dogs and humans. Parasite genetic differentiation between areas was not evident at the definitive host level, possibly suggesting frequent import and export of infections between villages, although there was some evidence of geographic structuring at the snail-intermediate host level.
  
  
  CONCLUSIONS
  These results suggest very high levels of transmission across host species, and indicate that the role of dogs should be considered when planning control programs. Furthermore, a regional approach to treatment programs is recommended where human migration is extensive.
authors.affiliation: Department of Infectious Disease Epidemiology, Faculty of Medicine, Imperial College London, London, United Kingdom. james.rudge01@imperial.ac.uk
authors.forename: James W
authors.initials: JW
authors.lastname: Rudge
authors.forename: Hélène
authors.initials: H
authors.lastname: Carabin
authors.forename: Ernesto
authors.initials: E
authors.lastname: Balolong
authors.forename: Veronica
authors.initials: V
authors.lastname: Tallo
authors.forename: Jaya
authors.initials: J
authors.lastname: Shrivastava
authors.forename: Da-Bing
authors.initials: DB
authors.lastname: Lu
authors.forename: María-Gloria
authors.initials: MG
authors.lastname: Basáñez
authors.forename: Remigio
authors.initials: R
authors.lastname: Olveda
authors.forename: Stephen T
authors.initials: ST
authors.lastname: McGarvey
authors.forename: Joanne P
authors.initials: JP
authors.lastname: Webster
mesh_terms: D000818:Animals; D002417:Cattle; D002681:China / Q000453:epidemiology; D004285:Dogs / Q000469:parasitology*; D005243:Feces / Q000469:parasitology; D005828:Genetics, Population; D005838:Genotype; D006801:Humans; D010679:Philippines / Q000453:epidemiology; D051381:Rats / Q000469:parasitology; D012550:Schistosoma mansoni / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity; D012555:Schistosomiasis mansoni / Q000453:epidemiology / Q000635:transmission* / Q000662:veterinary; D013552:Swine / Q000469:parasitology