Les hommes ont oublié cette vérité. Mais tu ne dois pas l'oublier, dit le renard. Tu deviens responsable pour toujours de ce que tu as apprivoisé.
Le Petit Prince, chap. 21

Saturday, 5 January 2013

Urban dogs as a source of virus for wild carnivores

Acosta-Jamett, G., Cleaveland, S., Cunningham, A. A., & Bronsvoort, B. M. D. (2010). Demography of domestic dogs in rural and urban areas of the Coquimbo region of Chile and implications for disease transmission. Preventive veterinary medicine, 94(3), 272-281.

A cross-sectional household questionnaire survey was conducted along two transects (80 and 45 km long) from Coquimbo and Ovalle cities to the Fray Jorge National Park (FJNP) in the Coquimbo region of Chile in 2005–2007 to investigate the demography of dogs in the context of a study of canine infectious diseases. Data were collected on the number of dogs per household, fecundity, mortality, and sex and age distribution. The results from 1021 households indicated that dog ownership was common, with a higher proportion of households owning dogs in rural areas (89%), than in towns (63%) or cities (49%). Dog density ranged from 1380 ± 183 to 1509 ± 972 dogs km-2 in cities, from 119 ± 18 to 1544 ± 172 dogs km-2 in towns, and from 1.0 ± 0.4 to 15.9 ± 0.4 dogs km-2 in rural sites. The dog population was estimated to be growing at 20% in cities, 19% in towns and 9% in rural areas. The human:dog ratio ranged from 5.2 to 6.2 in cities, from 2.3 to 5.3 in towns, and from 1.1 to 2.1 in rural areas. A high percentage of owned dogs was always allowed to roam freely in the different areas (27%, 50% and 67% in cities, towns and rural areas, respectively). Observations of free-roaming dogs of unknown owner were reported from a greater proportion of respondents in cities (74%), followed by towns (51%) and finally by rural areas (21%). Overall only 3% of dogs had been castrated. In addition, only 29% of dogs were reported to have been vaccinated against canine distemper virus (CDV) and 30% against canine parvovirus (CPV). The higher population size and density, higher growth rate and a higher turnover of domestic dogs in urban than in rural areas and the poorly supervised and inadequately vaccinated dog populations in urban areas suggest that urban areas are more likely to provide suitable conditions for dogs to acts as reservoirs of pathogenic infections.

Acosta-Jamett, G., Chalmers, W. S. K., Cunningham, A. A., Cleaveland, S., Handel, I. G., & Bronsvoort, B. M. (2011). Urban domestic dog populations as a source of canine distemper virus for wild carnivores in the Coquimbo region of Chile. Veterinary microbiology, 152(3), 247-257.

Urban areas can support dog populations dense enough to maintain canine distemper virus (CDV) and can be a source of infection for rural dogs and free-ranging carnivores. The aim of this study was to investigate the relationships between urban and rural domestic dog and wild carnivore populations and their effects on the epidemiology of CDV to explain retrospectively a CD outbreak in wild foxes in 2003. From 2005 to 2007 a cross-sectional household questionnaire survey was conducted in Coquimbo and Ovalle cities, in three towns and in rural sites along two transects from these cities to the Fray Jorge National Park (FJNP) in the Coquimbo region, Chile. Blood samples were collected from unvaccinated dogs at surveyed households and from free-ranging foxes in rural areas along the transects. The seroprevalence of CDV in domestic dogs was higher in urban than in rural areas and in the later was highest in dogs born before 2001–2002. The seroprevalence of CDV in foxes was higher in areas closer to human settlements. A high seroprevalence in dogs born before 2001–2002 further supports a link between CDV patterns in rural dog and fox populations. In our study area, urban dogs are proposed to be the source of CDV infection to wild carnivores. The large dog population size and density detected in Coquimbo and Ovalle provides optimal conditions for maintaining a large and dense susceptible population of dogs, which can act as a reservoir for highly infectious diseases and could have been the source of infection in the CD outbreak in wild foxes.

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