ABSTRACT. Pacheco A., Bahia M., Cordeiro M.D., Prado W.S., Scofield A., GoesCavalcante G., Fonseca A.H. [Frequency of antibodies against Toxoplasma gondii and Borrelia spp. in domiciled dogs at the Municipality of Castanhal in the State of Pará.] Frequência de anticorpos contra Toxoplasma gondii e Borrelia spp. em cães domiciliados do município de Castanhal, estado do Pará Revista Brasileira de Medicina Veterinária, 38(supl. 3): 122-128, 2016. Laboratório de Doenças Parasitárias, Departamento de Epidemiologia e Saúde Pública, Instituto de Veterinária, Universidade Federal Rural de Rio de Janeiro, BR 465, Km 7, 23890-000, Seropédica, RJ, Brasil. Email: firstname.lastname@example.org Domestic dogs can be infected by different zoonotic agents, assuming an epidemiological importance in the spatial distribution of these agents. The objective was to detect the frequency of antibodies against Toxoplasma gondii and B. burgdorferi lato sensu in dogs in the city of Castanhal, State of Para, Brazil. 186 dogs were studied (male = 88, female = 98) of different age groups (0-6 months> 6 months to 2 years> 2 years). Samples were collected for convenience in 148 animals domiciled in urban districts and 38 dogs resident in the rural area. Antibodies against T. gondii and B. burgdorferi lato sensu were detected in 59.7% and 80.1% of the animals examined, respectively. Antibodies against the two agents were detected in 48.4% (90/186) of the dogs. It is concluded that domestic dogs domiciled in urban and rural areas of the municipality of Castanhal, in the state of Pará, are exposed to infection by T. gondii and B. burgodoferi lato sensu, with animals aged over two years being the most frequent infected.