Caracterização e importância da Tristeza Parasitária Bo-vina e estudo da variabilidade genética de Anaplasma marginale (Theiler, 1910) em bezerros da região noroeste de Minas gerais, Brasil

Abstract

This work is divided into two chapters and aims 1) to characterize the importance of rickettsia Anaplasma marginale and the protozoan parasites Babesia bovis and Babesia bigemina in the occurrence of cattle tick fever (CTF) among calves in the Northwest region of Minas Gerais and 2) to evaluate the relationship between A. marginale genetic diversity and the anaplasmosis outbreaks occurrence in dairy farms same region. In the first chapter, Blood samples from 300 calves were collected and after DNA extraction Nested-PCR was performed using oligonucleotide primers that amplified fragments of the genes sbp-4 (B. bovis) and rap-1a (B. bigemina) and Semi-Nested for the gene msp5 (A. marginale). Blood smears were made from these animals. The prevalence of A. marginale 55,66% (167/300), B. bigemina. 15,33% (46/300) and B. bovis 4,0 % (12/300) of calves examined by techinques of PCR. Parasitic forms of A. marginale and B. bigemina were found in 36,33% and 2,66% of the blood smears while B. bovis was not detected. Infection rates by age in group 1 (10-70 days) were 41.12%, 26.16% and 3.73% for A. marginale, B. bigemina and B. bovis, respectively. While in group 2 (> 70-300 days) the prevalences were 63.73%, 9.32% and 4.14% for the same agents, respectively. Fifteen animals with fever, weight loss, jaundice and anemia were examined and nested-PCR confirmed the simple infection by A. marginale. For chapter II, Thirty previously positive calves (msp5 gene) for A. marginale with asymptomatic (n = 24) and acute (n = 6) infection were selected for the study of genetic diversity through semi-nested PCR targeting the msp1α gene. After sequencing of the samples, the genotype and tandem repeats structures were determined. Thirteen different strains were found: : αβFFF (9 animals), 13 27 27 (3 animals), τ 27 18 (3 animals), αββ 195 31 (3 animals), α 22 13 18 (3 animals), 80 FFFF (2 animals), α 22 13 13, αββГ, MφφφφF, 42 25 25 31, QQQM, BQBQBM, 1617FF (1 animal each). Genotype E was predominant in 93.33% of the samples (28/30), followed by genotypes C (3.33%) and G (3.33%). A new repeated tandem structure was described in the present work named BRA 1 (TDSSSASGVLSQSGQASTSSQLG). The αβFFF strain was present in six febrile animals that showed clinical sintoms of anaplasmosis like weight loss, jaundice and anemia. In the bovine herd studied anaplasmosis is the main cause of CTF. High genetic diversity of A. marginale occurred in persistently infected animals. However, during outbreaks of bovine anaplasmosis, low genetic diversity was observed. The αβFFF strain in northwestern Minas Gerais was associated with acute anaplasmosis. Genotype E was predominate.