Avaliação da infecção experimental por Neospora caninum em fêmeas bubalinas e bovinas, no terço inicial da gestação

Abstract

podem ser causados pelo N. caninum em búfalas. Palavras-chave: Neospora caninum. Búfala. Vaca. Abortamento. Isolados. ABSTRACT CHRYSSAFIDIS, A. L. Evaluation of experimental infection with Neospora caninum in bubaline and bovine females, in the first third of pregnancy. [Avaliação da infecção experimental por Neospora caninum em fêmeas bubalinas e bovinas, no terço inicial da gestação]. 2012. 127f. Tese (Doutorado em Medicina Veterinária) -Faculdade de Medicina Veterinária e Zootecnia, Universidade de São Paulo, São Paulo, 2012.Neospora caninum is a protozoan parasite with big importance all over the world, being considered the main cause of bovine abortion in some locations. While the implication of this parasite in bovine reproductive disorders is known, the available information within the buffalo species is scarce. This study evaluated and compared the consequences of experimental infection with N. caninum in buffaloes and cows on the initial stage of pregnancy, the most important regarding to the occurrence of fetal death. Protocols for fixed-time artificial insemination were used for greater control of fertilization. Two different isolates, Nc-Bahia and Nc-1, were utilized for inoculation, allowing the comparison between the national isolate and the standard isolate. All animals were inoculated with 5 x 10 8 tachyzoites, by endovenous route, at the 70th day of pregnancy. Three buffaloes and five cows were infected with the isolate Nc-Bahia and abortion was detected 42 days post-infection (DPI) in only one inoculated cow. Three buffaloes and two cows were inoculated with the isolate Nc-1 and fetal death was detected 35 DPI in all buffaloes and cows. A buffalo and a cow remained as negative controls, without infection. Vertical transmission was verified by semi-nested PCR in animals infected with Nc-Bahia and Nc-1. Different degrees of nonsuppurative inflamation were detected in maternal, foetal and placental tissues.All inoculated females showed humoral response against the infection. Although the infection was more disseminated withn the body of buffaloes (p <0.05), the humoral response was lower (p <0.05) and histological lesions were less frequent (p <0.05), indicating bigger adaptation between N. caninum and the buffaloes, in comparison with the results obtained in cows. Nc-Bahia isolate was less pathogenic than the Nc-1, as it caused less abortions (p <0.05) and lower frequency of histological lesions (p<0.05). The pathogenicity of the agent in the bubaline species was confirmed, considering the lesions found on histopathology analysis and the detection of the agent´s presence by semi-nested PCR in the different studied tissues, in addition to the positivity by immunohistochemistry test in bubaline placenta and foetal brain. This is the first detection of abortion caused by N. caninum in buffalo species, in females experimentally infected with the protozoan, confirming that reproductive disorders can be caused by N. caninum in buffaloes.