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Detection of ovine herpesvirus-2 in swine semen, Brazil

Background

Malignant Catarrhal Fever (MCF) is an often lethal viral disease of susceptible biungulates from Bovidae, Cervidae and Suidae subfamilies. Cases of porcine MCF have been associated with direct or indirect contact with sheep, the main reservoir of ovine herpesvirus-2 (OvHV-2). Pigs are terminal hosts and not considered in virus spread. Herein, we described the possible venereal transmission by infected semen in a pig herd.

Methods

In a breeding herd, it has been observed the occurrence of neurologic signs represented by excitation associated with high fever and abortion in pregnant sows and gilts for the last seven years. The mortality rate of disease ranged up to 5% of total sow breeding stock per year. Due the elevated biosecurity pattern, the pigs have no previous contact with sheep or any other ruminant. The histopathologic findings from brainstem samples of 5 sows collected from 2004 to 2008 outbreaks were consistent with MCF-like lesions, such as severe lymphocytic meningoencephalitis and necrotizing vasculitis. DNA was extracted from these samples and PCR was performed to detect ovine herpesvirus 2 (OvHV-2), pseudorabies and porcine cytomegalovirus.

Results

The OvHV-2 DNA was detected in 4 paraffin sections of brainstem. No amplification was observed for specific PCR assays for Aujeszky's disease and porcine cytomegalovirus. To confirm the member of MCFV group, one amplicon was sequenced and showed an identity of 99% with nucleotide sequences of OvHV-2 deposited in the GenBank. In order to find possible virus carrier, blood samples were collected from pregnant sows and breeding boars, being the viral DNA detection in three boars. To investigate the potential mode of OvHV-2 transmission, nasal swabs and semen samples were collected from these infected boars. The OvHV-2 DNA was detected only in semen samples. Two out of 3 semen had > 350 copy number/2 μg of total DNA, suggesting possible shedders. Important to mention that through out this period all infected boars remained clinically healthy.

Discussion

The combination of these results together with the absence of direct or indirect contact with sheep suggests the possibility of venereal transmission from infected semen to susceptible sows and gilts.

Author information

Correspondence to Erica Azevedo Costa.

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Open Access This article is published under license to BioMed Central Ltd. This is an Open Access article is distributed under the terms of the Creative Commons Attribution 2.0 International License (https://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Keywords

  • Meningoencephalitis
  • Semen Sample
  • Nasal Swab
  • Indirect Contact
  • Necrotizing Vasculitis