Mastitis, an inflammation of the mammary gland, is a common and costly disease in dairy cattle globally. While often associated with bacterial infections, Prototheca mastitis is a distinct and challenging form caused by microscopic algae. Understanding this algal infection is important for effective herd control.
Understanding Prototheca Mastitis
Prototheca mastitis is an infection of the udder caused by species of Prototheca, which are unicellular, colorless algae. The primary species associated with bovine mastitis are Prototheca bovis (formerly Prototheca zopfii genotype 2) and, less frequently, Prototheca blaschkeae and Prototheca ciferrii (formerly Prototheca zopfii genotype 1). These algae lack chlorophyll, meaning they do not perform photosynthesis.
The algal nature of Prototheca differentiates this mastitis from bacterial forms, especially in its response to treatment. Prototheca organisms are widespread in the environment, found in soil, water sources like streams and stagnant ponds, and decaying organic matter. They also thrive in high humidity and damp organic materials, such as manure, bedding, and milking parlor wash water.
Recognizing Infection and Spread
Prototheca mastitis often presents as a chronic, subclinical infection. Subtle changes in milk quality, such as discoloration, a watery consistency, or the presence of flakes and clots, may be observed. Infected cows typically do not exhibit severe systemic symptoms, but the infection can lead to a progressive decrease in milk production and persistently elevated somatic cell counts (SCC), sometimes exceeding 1,000,000 cells/ml.
Laboratory diagnosis is necessary to confirm Prototheca mastitis. Milk culture is the gold standard for identification, although Prototheca can grow slowly on traditional culture plates. Specialized selective media or advanced diagnostic tools like PCR can provide clearer and more rapid results. Infected cows can intermittently shed large numbers of the organism in their milk, making detection challenging.
Transmission within a herd primarily occurs through environmental contact. Contaminated water sources, bedding, and manure are common reservoirs. Poor hygiene practices during milking, such as inadequate teat sanitation or contaminated milking equipment, can facilitate cow-to-cow transmission in the parlor. This makes Prototheca mastitis both an environmental and a potentially contagious pathogen.
Strategies for Control and Prevention
Treating Prototheca mastitis poses a significant challenge because antibiotics are ineffective against these algal infections due to their different cell wall structure. Management strategies focus on limiting the spread of the infection and removing infected animals from the herd.
Segregation of infected cows into a separate group, to be milked last or with a dedicated milking unit, is recommended to prevent further transmission. Culling persistently infected animals is often the most effective way to control the disease and prevent its spread within the herd, especially if only a few animals are affected. This also helps prevent further environmental contamination.
Comprehensive prevention measures are important. Strict milking hygiene protocols are necessary, including pre-dipping teats with a bactericidal solution, stripping each teat to check for milk abnormalities, and thoroughly wiping teats with a clean towel. Applying a quality post-dip immediately after milking helps protect the teat from environmental contamination.
Environmental sanitation practices include ensuring clean and dry bedding, managing water sources to eliminate splash areas and standing water, and preventing access to manure. Routine testing of bulk tank milk and individual cows, especially those with elevated somatic cell counts or clinical mastitis that do not respond to antibiotic treatment, can aid in early detection. Prohibiting the feeding of milk from infected animals to calves, even if pasteurized, is also a recommended measure.