Abstract
Simple SummaryThe health and functionality of the mammary gland are important factors in animal welfare and milk production. Inflammation of the udder is associated with reduced milk yield and dairy product quality. Even though mastitis is usually caused by bacterial, fungal, or algae infections, some studies have suggested that infection with small ruminant lentivirus (SRLV), causing caprine arthritis-encephalitis (CAE), can also cause mastitis in small ruminants. Its pathophysiology is not, however, fully understood. Therefore, the aim of this study was to determine whether seropositive goats were more susceptible to bacterial infections of the udder than uninfected goats. A higher prevalence of pathogenic bacteria was identified only in seropositive goats in the 5th or further lactation. This indicates that a relationship may exist between a long-lasting SRLV infection and decreased resistance of the udder to bacterial infections, even though the seropositive goats enrolled in this study had no clinical signs of CAE.The aim of this study was to determine whether asymptomatic small ruminant lentivirus seropositive (SRLV-SP) goats were more susceptible to bacterial infection of the udder when lactating by comparing the presence and species of pathogenic bacteria in their milk with the values for seronegative goats (SRLV-SN). Milk samples were collected during morning milking on days 20, 40, 60, 150, and 210 of lactation for three consecutive years and subjected to bacteriological examination. Staphylococcus caprae and S. xylosus were the most frequent strains identified in both SRLV-SP and SRLV-SN goats. The prevalence of pathogenic bacteria was the highest in the 1st lactation, regardless of SRLV status. Moreover, the prevalence of pathogenic bacteria was significantly higher in SRLV-SP goats, but only those in the 5th or further lactation (p = 0.010). This suggests a relationship between long-lasting SRLV infection and susceptibility to bacterial infections of the udder.
Highlights
The health and functionality of the mammary gland are important factors in the welfare of dairy animals and milk production, as well as in dairy product quality and profitability for farmers and the dairy industry
S. aureus, a member of the coagulase-positive staphylococci (CPS), often causes mastitis in dairy cattle, and its presence is usually associated with increased somatic cell count (SCC)
100 μL of each milk sample were inoculated on BD Columbia CNA agar with 5% sheep blood to culture Gram-positive bacteria and MacConkey agar to culture Gram-negative bacteria (BioMérieux, Craponne, France)
Summary
The health and functionality of the mammary gland are important factors in the welfare of dairy animals and milk production, as well as in dairy product quality and profitability for farmers and the dairy industry. Mastitis is typically caused by bacterial, fungal, or algal infections, and usually manifests as an increase of milk somatic cell count (SCC) [1]; pathogenic bacteria, including Staphylococcus aureus, have been detected in about 20% of goat milk samples with SCC < 1 × 106/mL [2]. S. aureus, a member of the coagulase-positive staphylococci (CPS), often causes mastitis in dairy cattle, and its presence is usually associated with increased SCC. The presence of S. aureus in milk, and its thermostable toxins, which are resistant to pasteurization, can pose a threat to human health by causing food poisoning [8]. Another coagulase-producing staphylococcus—S. intermedius—has been isolated from goat milk [2]
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