Stray Dogs and Leishmaniasis in Urban Areas, Portugal

To the Editor: In southern Eu-rope, zoonotic visceral leishmaniasis caused by Leishmania infantum used to be considered a rural disease, but it is becoming more prevalent in urban areas. Outbreaks in urban/periur-ban settings are associated with the urbanization of natural zoonotic foci (1). The presence of a high number of stray dogs in urban/periurban settlements may contribute to the spread and increase of new infections. A canine survey was performed twice a month from December 1, 2002, through December 31, 2003. A total of 374 dogs from urban areas of Lisbon were screened for leishmani-asis. Owners voluntarily brought 277 domestic dogs; 97 stray dogs were from public shelters. Indirect fl uores-cent assay was used for detection of anti-Leishmania antibodies using a cutoff of 1/64, and popliteal lymph node aspirates for Novy, Nicolle, and MacNeal cultures were tested (2). A high overall prevalence (19.2%) of canine leishmaniasis was found, despite use of conventional tests only. The infection rate would probably have been higher had more sensitive techniques , such as molecular tools, been used. During the 1980s, Abranches et al. (2) performed a similar seroepide-miologic survey and found a prevalence rate of 5.5%. Our results show an increase of canine leishmaniasis cases in Lisbon. In our study, the prevelance of infection in domestic dogs was 18.4% (51/277), and the prevelance in stray dogs was 21.6% (21/97), with no statistical difference (p = 0.48, signifi cance level 95%). These results support the importance of the role of stray dogs in parasite transmission in Lisbon but differ from the 7.8% seroprevalence found in Madrid, where 1,803 stray dogs were studied over a 10-year period (3). However, the sample size and duration of both studies are different. In other urban areas of large European cities and Brazil, the existence of a high canine seroprevalence has shown an urbanization of the parasitosis (4,5). This is associated with an increase in 1-family homes with gardens in the peripheries of cities. Dogs are commonly kept in these gardens, which can provide good habitats for sandfl ies. On the other hand, the development of suburban areas can also lead to an increase of solid waste and defi cient sanitary conditions, thus attracting infected stray dogs. The difference in percentage of domestic dogs (39.21%) and stray dogs (28.57%) that appeared healthy, although infected, was not statistically signifi cant (p = 0.39). The percentage of apparently healthy dogs was lower …