Acta Tropica 120 (2011) 82–87 Contents lists available at ScienceDirect Acta Tropica j o ur nal homep age : www.elsevier.com/locate/ actatropica Seroepidemiological survey of Leishmania infantum infection in dogs from northeastern Portugal Susana Sousa a , Ana Patricia Lopes c , Luís Cardoso a,c , Ricardo Silvestre a , Henk Schallig d , Steven G. Reed e , Anabela Cordeiro da Silva a,b,∗ a Parasite Disease Group, IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, Portugal b Departamento de Ciências Biológicas, Faculdade de Farmácia, Universidade do Porto, Portugal c Departamento de Ciências Veterinárias, Universidade de Trás-os-Montes e Alto Douro, Vila Real, Portugal d KIT (Koninklijk Instituut voor de Tropen/Royal Tropical Institute), KIT Biomedical Research, Amsterdam, The Netherlands e Infectious Disease Research Institute, Seattle, WA, USA a r t i c l e i n f o Article history: Received 14 February 2011 Received in revised form 8 June 2011 Accepted 14 June 2011 Available online 2 July 2011 Keywords: Leishmania infantum Dogs Seroprevalence DAT ELISA a b s t r a c t Northeastern Portugal is a region where canine leishmaniasis (CanL) is endemic. In this study, a sero- epidemiological survey was conducted in 654 dogs from that geographical area. Serum samples were evaluated by the direct agglutination test (DAT) and also by enzyme-linked immunosorbent assay (ELISA) using five different defined antigens. Seroprevalence of infection was 21.3% based on the assumption that seropositive animals were positive for at least three tests. A high degree of agreement was found between DAT and LAM-ELISA (89%; kappa value [] = 0.67). A statistically significant difference (p < 0.05) of seropositivity was found between adult (23.4%) and juvenile dogs (12.2%), apparently healthy (14.8%) and sick dogs (40.2%), vaccinated (19.7%) and non-vaccinated (41.2%) animals, seropositive (26.9%) and seronegative (18.0%) for Toxoplasma gondii, living in rural (18.5%) or urban (32.6%) areas, and between animals living exclusively outdoors (18.2%) and those living in a mixed habitat (27.5%). Risk factors for canine Leishmania infection, as defined by multiple logistic regression analysis, were of clinical status (odds ratio [OR] = 3.1) and Toxoplasma infection (OR = 1.5). © 2011 Elsevier B.V. All rights reserved. 1. Introduction Leishmaniasis is a zoonosis caused by protozoa of the genus Leishmania and is the most important vector-borne disease after malaria and sleeping sickness (Solano-Gallego et al., 2009). The Mediterranean basin, the Indian subcontinent and South America are geographic areas where Leishmania infection is endemic (Bettini and Gradoni, 1986; Alvar et al., 2004). According to the World Health Organization (WHO), the public health impact of leishma- niasis worldwide has been grossly underestimated (Ready, 2010). In 2001, 350 million people were calculated to be at risk, with 12 million patients and 2 million new cases per year (Desjeux, 2001). About 2 million new cases of human leishmaniasis are considered to occur every year in the endemic regions (Ready, 2010). Dogs are considered the main reservoir of Leishmania infantum (syn. Leish- mania chagasi), the agent of zoonotic visceral leishmaniasis (VL). ∗ Corresponding author at: Parasite Disease Group, Instituto de Biologia Molecu- lar e Celular da Universidade do Porto, Rua do Campo Alegre 823, 4150-180 Porto, Portugal. Tel.: +351 222078923; fax: +351 222003977. E-mail addresses: susanasousa 76@hotmail.com (S. Sousa), cordeiro@ibmc.up.pt (A. Cordeiro da Silva). CanL is an emergent disease in several parts of the world, includ- ing non-endemic regions as consequence of the increasing number of travelling dogs (Menn et al., 2010). CanL is a systemic, chronic disease, ranging from asymptomatic subclinical to symptomatic infection. The clinical signs usually include lymphadenopathy, dermatitis, alopecia, cutaneous ulcerations, onychogriposis, lame- ness (abnormal locomotion), anorexia (poor appetite), weight loss, cachexia, ocular lesions, epistaxis, anaemia, diarrhoea and renal failure (Koutinas et al., 1999). Nevertheless, more than half of the infected animals are apparently healthy or asymptomatic (Solano- Gallego et al., 2001), but are still capable of transmitting the parasite to the vector, the phlebotomine sand flies (Guarga et al., 2000). This represents an important veterinary and public health prob- lem since it contributes to the maintenance of the Leishmania life cycle and transmission to humans. As a disease, the preva- lence of CanL is frequently lower than 10% in endemic regions (Solano-Gallego et al., 2009), but the prevalence of canine Leish- mania infection is thought to be considerably higher (Baneth et al., 2008). Current serological approaches to detect anti-Leishmania anti- bodies constitute a valuable alternative for early, rapid, and user-friendly diagnostic tests for both human and canine Leish- mania infection. These serological methods, such as the direct 0001-706X/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.actatropica.2011.06.003