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Bone marrow examinations were performed in a group of 10 Holstein-Friesian (HF) cows aged 2 years, which had been diagnosed with BVD/MD infection in a PCR screening test. Prior to bone marrow sampling, peripheral blood samples were collected for hematological analysis. Bone marrow was sampled from the third and fourth ribs in the sternal region, and it was placed in test tubes containing no anticoagulant. Smears were stained by the MGG method. The aim of this study was to demonstrate changes in the process of hematopoiesis in animals with clinical signs of BVD/MD. The results of the analysis revealed changes in erythrocyte, macrocyte-macrophage, lymphoid and granulocytic cell lines. There was a decrease in the number of red blood cells in the peripheral blood and polychromatic and ortochromatic erythroblasts in the bone marrow. A decrease in leukocyte counts below reference values resulted mainly from a decrease in the number of neutrophilic metamyelocytes, eosinophilic myelocytes and banded eosinophils. Moreover, a decrease in the number of megakaryocytes was observed in the megakariocytic system. BVDV infection causes changes in the activity of the hematopoietic system.
The paper presents the current state of knowledge on the prevalence and risk of a new type of bovine viral diarrhea virus known as type 3 (BVDV-3). The first discovered atypical pestivirus was the isolate D32/00_’HOBI’, detected in fetal calf serum (FCS) originating from Brazil. The isolates CH-KaHO/cont, SVA/cont-08 and IZSPLV_To are further examples confirming the presence of BVDV type 3 in the FCS. This new species of pestiviruses (BVDV-3) is a problem not only for research laboratories using bovine serum, but also for cattle breeders. Natural infections with this virus have been reported in Brazil, Thailand and Italy, which may suggest that the new species of pestivirus is also present in European cattle. The methods used for routine diagnosis of BVDV infection are ineffective in detecting atypical pestiviruses, which may pose a risk of false negative results. It may also influence the safety of vaccines and biological products produced on the basis of contaminated batches of fetal bovine serum.
Infection with bovine viral diarrhea virus is widespread in cattle populations all over the world and thus results in significant economic and breeding losses in herds of various sizes. The studies were conducted on 270 dairy cattle herds that have never been vaccinated against BVDV. Altogether 3732 samples were tested. Antibodies to BVDV were detected in 53.9% of herds. The correlation between herd size and seroprevalence was statistically significant and equal to 0.319 (p < 0.001). Analysis of clinical signs of BVD commonly observed in dairy cattle made it possible to conclude that a sudden drop of milk yield (OR = 2.037), diarrhea in calves (OR = 1.422), emaciation in young animals (OR=1.774) and emaciation in adults (OR = 1.715) were observed much more frequently in infected than uninfected herds. No increase was noted in the occurrence of other clinical signs regarded as typical for infected herds, such as spontaneous abortions and fetopathies in cows or respiratory and alimentary tract disorders.
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