title: Focal Philophthalmus gralli infection possibly persists in Melanoides tuberculata over two years following the definitive hosts' removal.
abstract: Philophthalmosis is a zoonotic disease associated largely with the spread of the invasive freshwater snail Melanoides tuberculata, serving as an intermediate host. Here we examined Philophthalmus gralli focal fenced infection site reported recently as being associated with Tinamus major and M. tuberculata in Alajuela, Costa Rica. Removal of the definitive hosts allowed us to address also the long-term survival strategy of the parasite. Initially, the snail intermediate hosts displayed high prevalence of P. gralli infection across all its age cohorts. Two years following the removal of definitive hosts, the infection rate decreased by one order of magnitude, while the snails aging less than one year displayed zero infection prevalence. Additionally, phylogenetic analysis of mitochondrial (ND1) and nuclear (ITS1, ITS2) DNA loci revealed negligible intrasite DNA variability of the specimens obtained at the study site in Costa Rica (but not of those obtained earlier in Peru or New Zealand), supporting strongly the hypothesis on focal origin of the infection. The observed dynamics of infection suggests the explanation for the high variability in P. gralli prevalence in intermediate hosts experienced worldwide. We noticed that the reports claiming >20% prevalence of M. tuberculata infection by P. gralli originated exclusively from foci with known eye infection of the definitive hosts, while the P. gralli infection penetrance <2% is typically associated with sites, where the infection of definitive hosts was not observed, suggesting that the infected definitive hosts were present onsite only in the past, or were present only at a site upstream or downstream of the respective sampling site. Thus, this is the first evidence on the possible persistence of eye-trematode infection site for over two years following the last confirmed outbreak in its adult hosts.
authors.affiliation: Charles University in Prague, Third Faculty of Medicine, Prague, Czech Republic. Electronic address: petr.heneberg@lf3.cuni.cz.
authors.forename: Petr
authors.initials: P
authors.lastname: Heneberg
authors.affiliation: Universidad de Costa Rica, Facultad de Microbiología, Centro de Investigaciones en Enfermedades Tropicales, Laboratorio de Helmintología, San Pedro de Montes de Oca, San José 2060, Costa Rica.
authors.forename: Alicia
authors.initials: A
authors.lastname: Rojas
authors.affiliation: Charles University in Prague, Third Faculty of Medicine, Prague, Czech Republic.
authors.forename: Jiří
authors.initials: J
authors.lastname: Bizos
authors.affiliation: Charles University in Prague, Third Faculty of Medicine, Prague, Czech Republic.
authors.forename: Lucie
authors.initials: L
authors.lastname: Kocková
authors.affiliation: Charles University in Prague, Third Faculty of Medicine, Prague, Czech Republic.
authors.forename: Milena
authors.initials: M
authors.lastname: Malá
authors.affiliation: Universidad de Costa Rica, Facultad de Microbiología, Centro de Investigaciones en Enfermedades Tropicales, Laboratorio de Helmintología, San Pedro de Montes de Oca, San José 2060, Costa Rica.
authors.forename: Diana
authors.initials: D
authors.lastname: Rojas
mesh_terms: D000818:Animals; D001483:Base Sequence; D018509:DNA, Helminth / Q000737:chemistry / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000737:chemistry / Q000235:genetics; D004196:Disease Outbreaks; D004197:Disease Reservoirs; D005618:Fresh Water; D006801:Humans; D008969:Molecular Sequence Data; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D012908:Snails / Q000469:parasitology*; D014200:Trematoda / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D014201:Trematode Infections / Q000453:epidemiology / Q000469:parasitology*; D015047:Zoonoses
chemical_list: D018509:DNA, Helminth; D021903:DNA, Ribosomal Spacer
keywords: Caenogastropoda; DNA analysis; Echinostomida; Lacrimal secretions; Melanoides tuberculata; Philophthalmus gralli