Indirect diagnostic tests for the detection of subclinical mastitis in dairy goats experimentally infected with Staphylococcus aureus

Testes diagnósticos indiretos na detecção da mastite subclínica em cabras leiteiras infectadas experimentalmente com Staphylococcus aureus

ABSTRACT:

The aim of the present study was to assess two diagnostic techniques (California mastitis test (CMT) and the somatic cell count (SCC)) that can diagnose mastitis in dairy goats. Experimental infection was conducted using 20 mammary glands, a strain of Staphylococcus aureus, an infectious dose of 1.2x10⁸CFU mL^-1 and a volume of 1mL per mammary gland. The CMT and the SCC were used to detect subclinical mastitis. Bacterial culture (BC) was performed immediately after milk collection and was used as the gold standard. Four experimental time points were established (0, 24, 48 and 72 hours post-inoculation). Analysis of the ROC curve confirmed that the best combination of sensitivity and specificity were obtained with a cutoff point of 405.5, 6030.0 and 729.5x10³ cells mL^-1, respectively at M1, M2 and M3. Furthermore, considering the drop in sensitivity throughout the experimental time points, the use of serial bacterial cultures are recommended, particularly in herds with a high prevalence ofS. aureus.

Key words:
bacterial culture; intramammary infection; small ruminant; somatic cell count