Serratia marcescens mastitis in a dairy herd

Area of Science:

• Veterinary Medicine
• Bacteriology
• Animal Science

Background:

• Bovine mastitis is a significant economic concern in dairy herds worldwide.
• Serratia marcescens is an opportunistic pathogen that can cause mastitis, but its epidemiology in dairy cattle is not fully understood.

Purpose of the Study:

• To investigate the occurrence and persistence of Serratia marcescens-induced mastitis in a dairy herd.
• To identify potential sources of S. marcescens infection within the herd environment and management practices.

Main Methods:

• Bacteriologic cultures were performed on milk samples from clinical and nonclinical mastitis cases.
• Cultures were also taken from postmilking teat dip, environmental surfaces, and equipment.
• Infection progression was monitored over a 10-month period.
• Economic losses were estimated using Dairy Herd Improvement Association (DHIA) linear score reports.

Main Results:

• Serratia marcescens was identified as the causative agent in both clinical (5 cows) and nonclinical (21 cows) mastitis cases within a 190-cow herd.
• S. marcescens was not isolated from teat dip, environmental samples, or equipment, suggesting an endogenous source or transmission route not identified by standard sampling.
• Infection persisted in some cows for at least 10 months.
• Average nonclinical mastitis loss was estimated at approximately $22 per cow.

Conclusions:

• Serratia marcescens can establish persistent intramammary infections in dairy cows.
• The lack of environmental isolation highlights the difficulty in controlling S. marcescens mastitis and suggests further investigation into transmission dynamics is warranted.
• Persistent S. marcescens infections contribute to economic losses in dairy herds, emphasizing the need for effective management strategies.