Antibiotic therapy is a critical component of the programs for the control of mastitis, the most common and costly disease in dairy cows. The efficacy of a mastitis treatment protocol is usually assessed using bacteriological cure, clinical recovery, and milk somatic cell count (SCC), which will decrease gradually after bacteriological clearance. (1*)
Importance of Antibiotic Therapy in Cow Mastitis
Cow mastitis is caused by almost 200 microorganisms and new pathogens, including yeast, fungi, viruses and bacteria, are continuously detected and reported. The most prevalent etiologic agents associated with mastitis are bacteria. Over 150 different types of Gram-positive and Gram-negative bacterial species can cause the disease.
Types of Mastitis Pathogens and Their Control
Contagious Pathogens
Contagious pathogens (Staphylococcus aureus, Streptococcus agalactiae, Mycoplasma bovis) reside on the udder and the teat skin of cows, colonizing and infiltrating the teat canal.
These pathogens can spread from infected to uninfected teats during milking. Preventive measures, including proper maintenance of milking equipment, post-milking teat disinfection, culling, and dry cow therapy (DCT), are essential to control the spread of these infections. (2*)
Environmental Pathogens
Escherichia coli, Klebsiella pneumoniae, Streptococcus uberis, and Streptococcus dysgalactiae are the primary causes of environmental clinical mastitis. These pathogens, which thrive in bedding and housing, can enter the teat during milking. To prevent infections, it is crucial to minimize teat end exposure and to enhance the cow’s resistance to intramammary infections (IMI) through antibiotic therapy and vaccination. (2*)
Antibiotic Therapy Strategies For Cow Mastitis
Antimicrobials are most frequently used for the treatment of clinical mastitis or dry cow therapy.
Clinical Mastitis Treatment
In cases of clinical mastitis, affected cows are milked out to remove bacteria, milk clots, debris, and toxins before intramammary (IMM) antibiotics are infused.
Severe cases may require combined parenteral and IMM administration to counter inflammation that hinders antibiotic distribution. (2*)
Dry Cow Therapy (DCT)
Dry cow therapy (DCT) involves long-acting antimicrobial infusions during dry-off to treat existing infections and prevent new ones during the dry period. This method significantly lowers post-calving infection rates. (3*)
Cause-based treatment decisions for selective clinical mastitis treatment are a significant opportunity to reduce antibiotic use on commercial dairy farms by over 50% for mild and moderate cases. This approach maintains treatment efficacy while safeguarding the long-term health and production potential of the cow. (4*)
Explore Our Decision Tree: Diagnostic Tools For Mild, Moderate, Severe, and Subclinical Mastitis
Current recommendations are based on targeted antibiotic usage for most gram-positive cases while allowing time for spontaneous cure of most other cases. (5*)
On farms with a high prevalence of Klebsiella spp., a diagnostic test that can differentiate between E. coli and Klebsiella spp. (both gram-negative bacteria) is recommended to ensure that cases of Klebsiella will receive antimicrobial treatment. (6*)
Read more on setting up an effective farm treatment plan for mastitis
Concerns and Challenges in Antibiotic Use
Antimicrobial Resistance (AMR) in Cow Mastitis
The rise of Antimicrobial Restistance (AMR) in cow mastitis pathogens, such as methicillin-resistant Staphylococcus aureus (MRSA), poses significant public health risks. Multidrug-resistant Gram-negative bacteria have also been found in raw milk and products. (7*)
The prudent use of antimicrobials in dairy farms reduces the emergence, persistence, and spread of antimicrobial-resistant bacterial strains. Monitoring AMR patterns in mastitis pathogens can be highly beneficial before initiating the treatment. (8*)
Balancing Welfare and Resistance
Despite general concerns about AMR, studies show that there is no substantial scientific evidence of increasing resistance among pathogens isolated from dairy cows to antibiotics that have been extensively used in the dairy industry. Not using antimicrobials could result in severe consequences for animal welfare and health and would also affect food production, food quality, and costs significantly. (9*)
Research should focus on balancing animal welfare with societal concerns regarding antimicrobial use. Establishing comprehensive guidelines will benefit dairy production and public health.
Pathogen-Specific Treatment Recommendations
Suggestions for antimicrobial treatment of clinical mastitis based on different pathogens (10*):
| Micro-organism | Species | Drug of choice | Alternative | Comments |
|---|---|---|---|---|
| Streptococci | Streptococcus agalactiae, Streptococcus dysgalactiae, Streptococcus uberis | Penicillin G | IMM treatment is preferable. | |
| Enterococci | According to susceptibility testing | Prognosis for bacteriological cure is poor. | ||
| Staphylococci | Staphylococcus aureus, Coagulase negative staphylococci β-lactamase -ve | Penicillin G | Combination treatment in S. aureus mastitis. | |
| Staphylococcus aureus, Coagulase negative staphylococci β-lactamase +ve | No antimicrobials | Cloxacillin, Macrolides, Lincosamides | IMM and/or systemic treatment depending on the drug used. Prognosis for S. aureus mastitis is poor. Cloxacillin may select for methicillin-resistant strains. | |
| Coliforms | Escherichia coli, Klebsiella spp. | No antimicrobials | Fluoroquinolones, Cephalosporins | Antimicrobials necessary in serious cases and during puerperal period. |
The availability of the substances on the market mentioned in the table may differ between countries.
Conclusion
Effective management of cow mastitis requires a multifaceted approach that balances animal health, productivity, and public health concerns. Prudent antibiotic use, guided by targeted therapies, minimizes the risk of antimicrobial resistance (AMR) while maintaining treatment efficacy. Regular monitoring, including AMR testing, ensures that treatments are appropriate and effective. Lastly, robust hygiene practices play a critical role in preventing the spread of pathogens, safeguarding both the health of dairy herds and the quality of milk production.
By adhering to these guidelines, dairy farmers can address mastitis effectively, promoting sustainable farming practices and contributing to the broader goal of antimicrobial stewardship.
Continue reading:
- Clinical Mastitis Treatment: Let’s be Selective!
- Guide to Testing for Subclinical Mastitis in Dairy Cows: Latest Diagnostic Methods and Technologies
- The Five-point Plan For Mastitis Control
BIBLIOGRAPHY
(1*) Sérieys F, Raguet Y, Goby L, Schmidt H, Friton G. Comparative Efficacy of Local and Systemic Antibiotic Treatment in Lactating Cows with Clinical Mastitis. J Dairy Sci. 2005;88 (1):93-9.
(2*) Cheng WN, Han SG. Bovine mastitis: risk factors, therapeutic strategies, and alternative treatments – A review. Asian-Australas J Anim Sci. 2020;33(11):1699-1713.
(3*) Biggs,A. Update on dry cow therapy 1. antibiotic v non-antibiotic approaches. In Practice. 2017;39(7):328-333.
(4*) Lago A, Godden SM, Bey R, Ruegg PL, Leslie K. The selective treatment of clinical mastitis based on on-farm culture results: I. Effects on antibiotic use, milk withholding time, and short-term clinical and bacteriological outcomes. J Dairy Sci. 2011;94(9):4441-56.
(5*) Ruegg PL. What Is Success? A Narrative Review of Research Evaluating Outcomes of Antibiotics Used for Treatment of Clinical Mastitis. Front Vet Sci. 2021;8:639641.
(6*) De Jong E, McCubbin KD, Speksnijder D, Dufour S, Middleton JR, Ruegg PL, Lam TJGM, Kelton DF, McDougall S, Godden SM, Lago A, Rajala-Schultz PJ, Orsel K, De Vliegher S, Krömker V, Nobrega DB, Kastelic JP, Barkema HW. Invited review: Selective treatment of clinical mastitis in dairy cattle. J Dairy Sci. 2023;106(6):3761-3778.
(7*) Naranjo-Lucena A, Slowey R. Invited review: Antimicrobial resistance in bovine mastitis pathogens: A review of genetic determinants and prevalence of resistance in European countries. J Dairy Sci. 2023;106(1):1-23.
(8*) Pascu C, Herman V, Iancu I, Costinar L. Etiology of Mastitis and Antimicrobial Resistance in Dairy Cattle Farms in the Western Part of Romania. Antibiotics (Basel). 2022;11(1):57.
(9*) Oliver S, Murinda S, Jayarao B. Impact of Antibiotic Use in Adult Dairy Cows on Antimicrobial Resistance of Veterinary and Human Pathogens: A Comprehensive Review. Foodborne Pathogens and Disease 2010;8(3):337-355.
(10*) Pyörälä, S. Treatment of mastitis during lactation. Ir Vet J 62 (Suppl 4), S40 (2009).