Genetic diversity and frequency of bovine viral diarrhea virus (BVDV) detected in cattle in Turkey

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Abstract

The aim of this study was to investigate the frequency and diversity of bovine viral diarrhea viruses (BVDV) infecting cattle in Turkey. A total of 1124 bovine blood samples from 19 farms in 4 different Turkish regions were tested by antigen capture ELISA (ACE). BVDV antigen was found in 26 samples from 13 farms. Only 20 of the 26 initial test positive cattle were available for retesting. Of these, 6 of 20 tested positive for BVDV, by ACE and real-time RT-PCR, one month after initial testing. Phylogenetic analysis, based on comparison of the E2 or the 5′UTR coding regions, from 19 of the 26 initial positive samples, indicated that 17 belonged to the BVDV-1 genotype and 2 to the BVDV-2 genotype. Comparison of 5′UTR sequences segregated 8 BVDV-1 strains (strains 5, 6, 10, 11, 12, 13, 17, and 19) to the BVDV1f, 1 strain (strain 8) to the BVDV1i and 1 strain (strain 14) to the BVDV1d subgenotypes. One strain (strain 4) did not group with other subgenotypes but was closer to the BVDV1f. The remaining 6 BVDV-1 strains (strains 1, 2, 3, 7, 9, and 18) segregated to a novel subgenotype. The E2 sequence comparison results were similar, with the exception that strain 5 grouped with the novel subgenotype rather than BVDV1f subgenotype. It appears that among the diverse BVDV strains in circulation there may be a subgenotype that is unique to Turkey. This should be considered in the design of diagnostics and vaccines to be used in Turkey.

Introduction

Bovine viral diarrhea virus (BVDV), like other members of the Pestivirus genus in the family of Flaviviridae, is a small, enveloped virus with a single-stranded RNA genome of positive polarity [1]. BVDV strains are divided into 2 different genotypes known as BVDV type 1 (BVDV-1) and BVDV type 2 (BVDV-2). Phylogenetic analyses reveal sub-genotypes within the two types. At present, 15 BVDV-1 sub-genotypes (a–o) and 2 BVDV-2 sub-genotypes (a and b) have been proposed [2], [3], [4], [5].

Cattle and sheep can be infected by both BVDV genotypes resulting in reproductive, enteric and respiratory disorders. Clinical presentations range from mild subclinical in immuno-competent cattle to highly fatal disorders such as hemorrhagic syndrome, associated with infection with virulent BVDV-2 strains, and mucosal disease, associated with BVDV superinfection of cattle born persistently infected with BVDV [6], [7]. Viruses from either genotype may exist as one of two biotypes, cytopathic and noncytopathic. Non-cytopatic viruses of both genotypes may cause persistent infection in cattle resulting in fatal mucosal disease later in their life [3]. BVDV in cattle has been reported world wide including Turkey and has a significant economic impact on the cattle industry because of death and production losses [2], [3], [5], [7], [8], [9].

Virus isolation, serological and molecular techniques have been used for the detection and identification of genotypes and sub-genotypes of BVDV [10]. The aim of this study was to investigate the frequency of detection of BVDV is bovine serum samples collected from cattle in four different regions of Turkey and to evaluate the genetic diversity of BVDV isolated from Turkish cattle.

Section snippets

Samples and study population

Blood samples were collected from 19 farms located in 4 different regions of Turkey. Samples were collected between 2009 and 2011. A total of 1124 plasma samples (510 from Aegean, 580 from Marmara, 24 from Central Anatolia and 10 from the Black Sea region) were tested. Samples were transported to the laboratory in cold storage (4–8 °C). Plasma samples were analyzed for the presence of BVDV antigen by ELISA as described by the manufacturer (IDEXX antigen ELISA kit-43830-V971). Cattle that tested

Frequency of BVDV detected by ELISA

BVDV antigen was detected in 26 cattle out of 1124 tested (2.3%). BVDV was detected in 13 of 19 farms (68.4%). Of the positive cattle, 15 were from Marmara, 9 from Agean and 2 from Black Sea region. Of the 26 ELISA positive samples, 20 were available for resampling and were retested by ELISA, six were found to be positive for BVDV antigen, indicating persistent infections. These persistently infected cattle were from the Agean, Marmara and Black Sea regions.

Real-time SYBR Green assay for Pestiviruses

All samples tested positive by ELISA,

Discussion

It is important to determine the incidence of infection and diversity of BVDV strains circulating in a region in order to design effective surveillance and control programs. This study focused on the detection, identification and diversity of BVDV strains in cattle in Turkey. Numerous BVDV detection tests have been used including ELISA, RT-PCR, real time RT-PCR, IFA and immuno-histochemistry as well as virus isolation [4], [12], [15], [16]. Real-time PCR has many advantageous because of its

Acknowledgments

We would like to thank to University of Istanbul for funding this study (Project No: BAP-7002 and 23405). Particular thanks to Professor Ludwig Haas and Professor Volker Moennig for supplying positive control for PCR.

References (36)

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