Acta Tropica 81 (2002) 21–31 Follow-up of experimental chronic Chagas’ disease in dogs: use of polymerase chain reaction (PCR) compared with parasitological and serological methods F.M.G. Arau ´jo a , M.T. Bahia b , N.M. Magalha ˜es c , O.A. Martins-Filho d , V.M. Veloso b , C.M. Carneiro c , W.L. Tafuri a , M. Lana c, * a Nu ´cleo de Pesquisas em Cie ˆncias Biolo ´gicas (NUPEB), Instituto de Cie ˆncias Biolo ´gicas, Campus Uniersita ´rio, Morro do Cruzeiro, Brazil b Departamento de Cie ˆncias Biolo ´gicas, Instituto de Cie ˆncias Biolo ´gicas, Campus Uniersita ´rio, Morro do Cruzeiro, Brazil c Departamento de Ana ´lises Clı ´nicas, Escola de Farma ´cia, Uniersidade Federal de Ouro Preto, Rua Costa Sena, 171 -Centro, CEP 35400 -000 Ouro Preto, Brazil d Centro de Pesquisas Rene ´ Rachou, FIOCRUZ-BH, A. Augusto de Lima 1715 -Barro Preto, CEP 30190 -002 Belo Horizonte, MG, Brazil Received 30 March 2001; received in revised form 27 June 2001; accepted 27 August 2001 Abstract In this study, the polymerase chain reaction (PCR) was compared with parasitological and serological methods to detect the infection in dogs, 5 – 12 years after experimental infection with Trypanosoma cruzi. The ability of parasitological methods to identify a positive animal was 22 and 11% by hemoculture and xenodiagnosis/xenoculture, respectively. On the other hand, the serological tests, including conventional serology and anti-live trypomastigote antibodies (ALTA) were positive in all infected dogs. Despite its low sensitivity, if considering only one reaction, the PCR analysis showed 100% of positivity, demonstrating the presence of parasite kDNA in all infected dogs. To identify a positive dog required at least two blood samples and up to nine repeated reactions using the same sample. Serial blood sample collection, ranging from 1 to 9, revealed that the percentage of dogs with positive PCR ranged from 67 to 100%. These findings suggested that, although the PCR is useful to detect the parasite in infected hosts, it should not be used isolated for the diagnosis of Chagas’ disease and warn for the necessity of serial blood collection and re-tests. Moreover, these data validate once more the dog as a model for Chagas’ disease since they demonstrate the permanence of infection by PCR, parasitological and serological methods, reaching relevant requisites for an ideal model to study this disease. © 2002 Elsevier Science B.V. All rights reserved. Keywords: Trypanosoma cruzi ; Dog; Chronic infection; PCR; Parasitological tests and serology www.parasitology-online.com 1. Introduction Dogs have been frequently used as experimental model to study Chagas’ disease. The acute phase * Corresponding author. Tel.: +55-31-3559-1680; fax: +55-31-559-1628. E-mail address: delana@cpd.ufop.br (M. Lana). 0001-706X/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved. PII:S0001-706X(01)00196-6