Study on Correlation of Maedi-Visna Virus (MVV) with Ovine Subclinical Mastitis in Iran

Abstract

Maedi-Visna is an important slow viral disease of sheep leading to progressive pneumonia, encephalitis and mastitis. Udder is one of the organs affected by MVV. Despite the fact that in Iran Maedi-Visna is known since 2000, to the authors' knowledge correlation of subclinical mastitis and infection with MVV has not been assayed. In this study 50 milk samples from 10 flocks in East Azerbaijan Province of Iran were tested. None of the animals exhibited any clinical signs of the disease. Forty samples were collected from CMT positive ewes and ten were taken from CMT negative ewes. Milk samples were analyzed using PCR targeting gag sequence. Presence of provirus DNA was detected in one sample from CMT negative and seven samples from CMT positive ewes. These data demonstrate that 16.5 % of sheep with subclinical mastitis were infected to MVV. Thus this virus can be considered one of the main pathogenic agents of mastitis and can be dramatically transmitted to lambs by milk.

Keywords: Maedi-Visna; Mastitis; Milk; PCR; Sheep.

Fig. 1

PCR products gel electrophoresis. L: DNA ladder (100 bp), 1: negative control (fish sperm DNA), 2–4: positive samples, 5: negative sample, 6: positive control, 7/8: negative samples, 9: water blank

Fig. 2

Alignment of the sequence of Iran’s isolate with nearest homologue sequence (Accession # HQ848062.1)

Fig. 3

Neighbour-joining phylogenetic tree based on 748 bp fragment of the gag gene. NCBI registered isolates are shown by name except “Iran’s isolate”