Neospora caninum: diagnóstico e caracterização genética em fetos de fêmeas zebuínas abatidas
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2010-02-26
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Universidade Federal de Goiás
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One of the main causes of reproductive failure in cattle is infection by the protozoan Neospora caninum (Phylum Apicomplexa, Family Sarcocystidae). The bovine neosporosis is characterized by an asymptomatic infection in the non pregnant cow; however, during pregnancy, the vertical transmission of the parasite is responsible for the maintenance of the infection for successive generations. The highest frequency of infection occurs in the dairy production system and in the intensive management of animal breeding, with most of the available data for N. caninum related to Bos taurus, even for beef cattle. Thus, the presence of N. caninum has been little studied in Bos indicus. In Goiás, the prevalence of N. caninum is 29.61% in beef cattle and 30.4% in dairy cattle. As the prevalence of infection in adults should have a positive correlation to the incidence of fetal infection, this study aimed to evaluate the occurrence of vertical transmission of N. caninum in zebuine fetuses of various ages, obtained from females slaughtered in a slaughterhouse in the municipality of Senador Canedo, Goiás. For that, the serological analysis of abdominal fluid and molecular and histopathological analysis in tissue samples (brain, heart and liver) were performed. The fetal age was estimated by the measurement of crown-rump length. A total of 195 fetal fluids was randomly collected and tested by IFAT with a cut-off point of 1:16. 585 tissue samples were submitted to nested-PCR analysis of ITS-1 rRNA region and to histopathology. The results were related to the fetal age (first, second and third stages of pregnancy). Anti-N. caninum antibodies were detected in 12 (6.15%) fetal fluids, with IFAT titers observed at 1:64 (n=1), 1:128 (n=2), 1:512 (n=3), 1:1024 (n=5) and 1:2048 (n=1). The presence of the parasite was detected by PCR in 40 (20.5%) fetuses. On histopathological examination, 82 (42.05%) fetuses had characteristic and consistent lesions, compatible with protozoan infection, characterized by encephalitis, myocarditis and hepatitis with mononuclear cell infiltrates, with or without necrosis. Comparing the different gestational ages, there was a greater number of positive reactions by IFAT, PCR and compatible histopathological lesions in the sixth and seventh month of pregnancy. From the total of 585 tissue samples examined, 56 were positive, being 12 at serology and 44 (35 brains, seven hearts and two livers) at PCR from 45 fetuses. In histopathology, 10 samples (three brains, six hearts and one liver) showed characteristic lesions of protozoan infection such as N. caninum. The DNA from six PCR positive fetuses was analyzed by microsatellite markers for genetic characterization of isolates of N. caninum, demonstrating the existence of genetic profiles different from other isolates of the world and of Brazil infecting zebuine animals. The results confirm the occurrence of vertical transmission of N. caninum, the diagnosis of infection in zebuine fetuses, the need of association of techniques for determining fetal neosporosis and characterization of different regional isolates circulating in zebu herd from Goiás.
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FERNANDES, Paula Rogério. Neospora caninum: diagnosis and genetic characterization in fetuses of zebu cows slaughtered. 2010. 106 f. Tese (Doutorado em Ciências Agrárias) - Universidade Federal de Goiás, Goiânia, 2010.