title: Heterogeneities in Leishmania infantum infection: using skin parasite burdens to identify highly infectious dogs.
abstract: BACKGROUND
  The relationships between heterogeneities in host infection and infectiousness (transmission to arthropod vectors) can provide important insights for disease management. Here, we quantify heterogeneities in Leishmania infantum parasite numbers in reservoir and non-reservoir host populations, and relate this to their infectiousness during natural infection. Tissue parasite number was evaluated as a potential surrogate marker of host transmission potential.
  
  
  METHODS
  Parasite numbers were measured by qPCR in bone marrow and ear skin biopsies of 82 dogs and 34 crab-eating foxes collected during a longitudinal study in Amazon Brazil, for which previous data was available on infectiousness (by xenodiagnosis) and severity of infection.
  
  
  RESULTS
  Parasite numbers were highly aggregated both between samples and between individuals. In dogs, total parasite abundance and relative numbers in ear skin compared to bone marrow increased with the duration and severity of infection. Infectiousness to the sandfly vector was associated with high parasite numbers; parasite number in skin was the best predictor of being infectious. Crab-eating foxes, which typically present asymptomatic infection and are non-infectious, had parasite numbers comparable to those of non-infectious dogs.
  
  
  CONCLUSIONS
  Skin parasite number provides an indirect marker of infectiousness, and could allow targeted control particularly of highly infectious dogs.
authors.affiliation: School of Life Sciences, and Warwick Infectious Disease Epidemiology Research (WIDER), University of Warwick, Coventry, United Kingdom.
authors.forename: Orin
authors.initials: O
authors.lastname: Courtenay
authors.affiliation: School of Life Sciences, and Warwick Infectious Disease Epidemiology Research (WIDER), University of Warwick, Coventry, United Kingdom.
authors.forename: Connor
authors.initials: C
authors.lastname: Carson
authors.affiliation: School of Life Sciences, and Warwick Infectious Disease Epidemiology Research (WIDER), University of Warwick, Coventry, United Kingdom.
authors.forename: Leo
authors.initials: L
authors.lastname: Calvo-Bado
authors.affiliation: Laboratório de Epidemiologia e Imunologia aplicada às Leishmanioses, Seção de Parasitologia, Instituto Evandro Chagas, Belém, Pará, Brazil ; Centro do Ciências Biológicas e da Saúde, Universidade do Estado do Pará, Belém, Pará, Brazil.
authors.forename: Lourdes M
authors.initials: LM
authors.lastname: Garcez
authors.affiliation: School of Biology, University of Leeds, Leeds, United Kingdom.
authors.forename: Rupert J
authors.initials: RJ
authors.lastname: Quinnell
mesh_terms: D000818:Animals; D001853:Bone Marrow / Q000469:parasitology; D001938:Brazil; D002353:Carrier State / Q000469:parasitology / Q000662:veterinary; D004283:Dog Diseases / Q000469:parasitology*; D004285:Dogs; D005589:Foxes; D018314:Leishmania infantum / Q000302:isolation & purification*; D007898:Leishmaniasis, Visceral / Q000469:parasitology / Q000662:veterinary*; D059208:Parasite Load; D060888:Real-Time Polymerase Chain Reaction; D012867:Skin / Q000469:parasitology*