Bayesian Latent Class Models in Veterinary and Human Epidemiology Luzia Gonc¸alves, Ana Subtil, Nuno Brites, M. Ros´ ario Oliveira, Ana Margarida Alho, Jos´ e Meireles, Lu´ıs M. Madeira de Carvalho and Silvana Belo Abstract Latent class models have been widely used to evaluate the performance of veterinary and human diagnostic tests, in the absence of a gold standard. In this work, we explore Bayesian latent class models, with and without restrictions, in dif- ferent populations. We previously reported the Bayesian latent class analysis of the malaria dataset (n =3317) and now we apply a similar approach to a smaller dataset in the context of canine dirofilariasis (n =308). Although the last study presents a small sample size, it was important to obtain the first estimates of the prevalence (and performance measures of diagnostic techniques) of canine dirofilariasis in three districts of Portugal, taking into account the relationship with human dirofilariasis. Key words: Latent class model, Bayesian approach, conditional dependence, diag- nostic test, dirofilariasis. Luzia Gonc¸alves CEAUL and Unidade de Sa´ ude P´ ublica Internacional e Bioestat´ıstica, Instituto de Higiene e Medic- ina Tropical, Rua da Junqueira, 100, 1349-008 Lisboa, Portugal, e-mail: luziag@ihmt.unl.pt Ana Subtil CEMAT and Faculdade de Ciˆ encias da Universidade de Lisboa, Campo Grande Edif´ıcio C5, 1749- 016 Lisboa, Portugal. Nuno Brites Unidade de Sa ´ ude P ´ ublica Internacional e Bioestat´ıstica, Instituto de Higiene e Medicina Tropical, Rua da Junqueira, 100, 1349-008 Lisboa, Portugal M. Ros´ ario de Oliveira CEMAT and Departamento de Matem´ atica, Instituto Superior T´ ecnico, Universidade T´ ecnica de Lisboa, Avenida Rovisco Pais, 1049-001 Lisboa, Portugal Ana Margarida Alho, Jos´ e Meireles and Lu´ıs M. Madeira de Carvalho Laborat´ orio de Parasitologia - CIISA - Faculdade de Medicina Veterin´ aria, Universidade T´ ecnica de Lisboa, Avenida da Universidade T´ ecnica, 1300-477 Lisboa, Portugal Silvana Belo UPMM and Unidade de Parasitologia M´ edica, Instituto de Higiene e Medicina Tropical, Rua da Junqueira, 100, 1349-008 Lisboa, Portugal 1