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  • Author: Mirosław P. Polak x
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Magdalena Larska, Aleksandra Kuta and Mirosław P. Polak

Abstract

Two issues concerning virus detection and identification of persistently infected (PI) cattle were analysed in the study: 1) interference by maternal antibodies and 2) discrimination between PI and transiently infected (TI) animals. Antigen ELISA and RT-PCR based methods were compared using serum samples from natural and experimental PI and TI calves. RT-PCR and realtime RT-PCR using primers within 5’UTR region were more sensitive in detecting PI animals than Erns and NS3 antigen capture ELISAs, and they were not influenced by the presence of colostral antibodies in serum or by bovine viral diarrhoea virus genotype. The serum samples with Ct values ≤ 29.10 (corresponding to 104.87 viral RNA copies/μL) identified PI animals with 100% probability, while all samples with Ct values > 32.06 (corresponding to viral RNA load below 104 copies/μL) indicated TI status. The samples with Ct values between 29.10 and 32.06 (17.2% of PI and 11.5% of TI) should be considered as PI suspect and retested.

Open access

Aleksandra Kuta, Mirosław P. Polak, Magdalena Larska and Jan F. Żmudziński

Abstract

The aim of the study was to evaluate the status of bovine viral diarrhoea virus (BVDV) infection in selected dairy herds in Poland with the use of commercial enzyme linked immonosorbent assay for the detection of specific antibodies (BVDV-Ab ELISA) and reverse transcription-polymerase chain reaction (RT-PCR) for the detection of viral RNA, using bulk tank milk (BTM) samples. Two hundred and thirty-one samples of BTM were collected from 99 dairy herds in Poland. The herds were divided into four different classes according to the Swedish system of classification. The results showed that 70.7% of herds were BVDV antibodypositive. High levels of antibodies in 52.85 % (37 herds in class 3) of all antibody positive herds indicated acute BVDV infection. Thirty five samples with the highest antibody levels were tested by RT-PCR and five of them were positive for viral RNA. Dairy herds in Poland have high levels of antibodies against BVDV in BTM. Since no vaccination was implemented in the herds tested, high seroprevalence of BVDV antibodies in cattle indicates the widespread of BVDV infection in Polish cattle.

Open access

Mirosław P. Polak, Aleksandra Antos, Jerzy Rola and Jan F. Żmudziński

Abstract

Introduction: Bovine viral diarrhoea (BVD), caused by the bovine viral diarrhoea virus (BVDV), is one of the most important diseases of cattle worldwide. The purpose of the study was to determine the BVDV infection status in a dairy herd vaccinated against BVD. Before vaccination started in 2008, there had been no prior identification or the removal of the possible source of infection (persistently infected animals). It was expected that vaccination itself would enable the elimination of viral shedders on a long term basis. Material and Methods: Serological screening for antibodies against BVDV with determination for antibodies titres, BVDV antigen, and the presence of the viral genome with phylogenetic analysis of positive samples in the herd were performed, despite the lack of any clinical problems indicating possible presence of BVDV infection. Results: 19 individuals persistently infected with BVDV were identified among calves and heifers but not in adult cattle. All virus shedders were antibody negative and the genotype of isolated virus was BVDV-1b, indicating a single source of infection. The vaccine used in the herd was composed of BVDV-1a strain. In each of the tested cowsheds, antibody titres against BVDV-1b were higher than against BVDV-1a (median values). Conclusion: Despite a long-lasting vaccination programme and relatively high sequence homology of vaccinal and field strains of BVDV (83.6%), it was not possible to avoid transplacental infections of foetuses and the birth of persistently infected calves from vaccinated heifers although the protection against clinical disease was accomplished.

Open access

Aleksandra Kuta, Mirosław P. Polak, Magdalena Larska and Jan F. Żmudziński

Abstract

Restriction fragment length polymorphism (RFLP) analysis was developed for genetic typing of Polish strains of bovine viral diarrhoea virus (BVDV). The method was applied using 60 BVDV isolates, which included BVDV genotype 1, subtypes a, b, d, e, f, and g, and genotype 2a. RT-PCR products of the 5’untranslated region (5’UTR) were digested using three enzymes. Restriction patterns classified the strains into seven groups, each with a specific and different pattern from other subtypes. These findings were confirmed by nucleotide sequencing and phylogenetic analysis. The results suggest that RFLP analysis is a simple, reliable, and fast genotyping method for BVDV strains in comparison with sequencing. This method can distinguish six subtypes of BVDV-1 including a new subtype 1e, identified exclusively by this method, and it allows differentiation of BVDV-1 from BVDV-2 genotype.

Open access

Małgorzata Kwaśnik, Ilona M. Góra, Jan F. Żmudziński, Jerzy Rola, Mirosław P. Polak and Wojciech Rożek

Abstract

Introduction

Traditionally, evolutionary analysis of equine influenza virus (EIV) is based on the HA gene. However, the specificity of the influenza virus enables the classification of viral strains into different phylogenetic groups, depending on the gene being analysed. The aim of the study was to analyse phylogenetic paths of EIV based on M gene with reference to the HA gene.

Material and Methods

M gene of Polish isolates has been sequenced and analysed along with all M sequences of EIV available in GenBank database. Phylogenetic analysis was performed using BioEdit, ClustalW, and MEGA7 softwares.

Results

The clustering of the strains isolated not only from Asia but also from Europe into one common Asian-like group of EIV was observed. Twelve nucleotide substitutions in the M gene of strains from the Asian-like group were crucial for the evolutionary analysis. We also observed homology in the M gene of the Asian-like and H7N7 strains.

Conclusions

M gene specific for the Asian-like group is present in strains recently isolated in Europe and Asia, which were classified previously in the Florida 2 clade based on HA. Therefore, Asian-like group does not seem to be assigned to a specific geographical region. Traces of H7N7 strains in more conservative genes like M of some contemporary EIV strains may indicate the link between the old phylogenetic group and recent H3N8 strains. Analysis of conservative genes may be more useful in tracking the direction of virus evolution than in the genes where the high variability rate may blur the original relationships.