Abstract
Background and Aim:Mastitis is an important threat facing goat milk industry and is the most common cause of culling. Efficient control of mastitis, based on efficient diagnosis of diseased animals, would improve milk production and reproductive efficiency. In subclinical mastitis (SCM), infected goats demonstrate neither udder symptoms nor abnormal milk. Corynebacterium pseudotuberculosis is an infectious causative agent of mastitis, mostly results as an extension of infection from the supramammary lymph node, and causes financial losses in the goat industry. This study aimed to estimate the prevalence of SCM with emphasis on C. pseudotuberculosis mastitis in Egyptian dairy goats in the selected farms.Materials and Methods:A total of 336 half milk samples were collected from 177 dairy goats of various crossbreeds, in mid-to-late lactation period, after clinical examination. All samples were examined bacteriologically, while somatic cell count (SCC) was determined only in 180 half milk samples of the clinically healthy milk samples. The isolated and identified C. pseudotuberculosis was examined for evidence of virulence genes (Phospholipase D [pld] and β-subunit of RNA polymerase [rpoB]) by polymerase chain reaction (PCR).Results:The prevalence of clinical mastitis was 30.5%, while 69.5% of animals were apparently healthy and secreted milk was normal. Of those 180 clinically healthy half milk samples, 96 milk samples (53.33%) showed SCM as detected by SCC (SCC ≥1,000,000 cells/ml). Coagulase-negative staphylococci were the most prevalent bacteria (41.96%), then Staphylococcus aureus (37.5%) and C. pseudotuberculosis (7.14%). Molecular diagnosis of virulence genes revealed evidence of pld gene in 16 isolates (66.66%), and rpoB gene in 6 samples (25%) of the 24 bacteriologically isolated C. pseudotuberculosis. Here, we describe, for the 1st time, isolation and identification of C. pseudotuberculosis from milk of does suffering from SCM in Egypt.Conclusion:C. pseudotuberculosis must be considered for routine bacteriological examination of milk from dairy goats, particularly herds with a history of caseous lymphadenitis. Pld gene-based PCR is more reliable than rpoB gene-based ones for the diagnosis of C. pseudotuberculosis.
Highlights
The past two decades have seen intensification in dairy goat production with a significant increase in the number of goats worldwide [1,2], as nutritional qualities of goat milk are to great extent similar to human milk, and less allergenic for human than bovine milk [3].Mastitis is the most serious disease in dairy goats due to financial losses attributed to its negative impact on milk quantity and components [4,5] and is the main cause of culling for sanitary reasons [6]
C. pseudotuberculosis must be considered for routine bacteriological examination of milk from dairy goats, herds with a history of caseous lymphadenitis
Animals were diagnosed for clinical mastitis if suffer from pain on milking, swelling of udder, hardness, and necrosis in udder, decreased milk production, or changes in milk
Summary
Mastitis is the most serious disease in dairy goats due to financial losses attributed to its negative impact on milk quantity and components [4,5] and is the main cause of culling for sanitary reasons [6]. Mastitis is an important threat facing goat milk industry and is the most common cause of culling. In subclinical mastitis (SCM), infected goats demonstrate neither udder symptoms nor abnormal milk. Corynebacterium pseudotuberculosis is an infectious causative agent of mastitis, mostly results as an extension of infection from the supramammary lymph node, and causes financial losses in the goat industry. This study aimed to estimate the prevalence of SCM with emphasis on C. pseudotuberculosis mastitis in Egyptian dairy goats in the selected farms
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