Mastitis

Subclinical mastitis shows nothing visible and is found only by a raised somatic cell count or the California Mastitis Test; in cows a count above 200,000 cells/mL signals infection. Clinical mastitis is first seen in the milk, as clots or otherwise visibly abnormal secretion, and the affected gland becomes swollen, hot and painful. Environmental mastitis ranges from these local signs to systemic illness: fever, depression, going off feed, rapid breathing and sometimes death. In camels, clinical and subclinical forms are both recognised, with subclinical cases far more common.

Mastitis is inflammation of the udder tissue, usually the result of bacterial infection inside the mammary gland. Organisms reach the gland through the teat (streak) canal and multiply; the cow's immune cells move into the milk to fight them, which is why the somatic cell count rises. More than 135 microorganisms have been recovered from bovine mastitis. The main contagious agents are Staphylococcus aureus, Streptococcus agalactiae and Mycoplasma bovis; environmental agents include coliforms (Escherichia coli, Klebsiella, Enterobacter), Streptococcus uberis, S. dysgalactiae and Enterococcus. During the dry period a keratin plug normally seals the teat canal, but many quarters stay open for days to weeks after drying off, and around calving the plug breaks down and white cell function weakens, so bacteria enter easily. Infections picked up then often surface as clinical mastitis early in the next lactation.

Contagious pathogens live in infected udders and spread cow to cow at milking on teat cups and milkers' hands; environmental pathogens come from bedding, manure and wet surroundings, and multiply as heat and moisture rise. Where contagious organisms have been controlled, environmental ones now cause more clinical cases, especially in the first 100 days of lactation. Over 60% of new infections arise in the dry period, most of them environmental, with high-risk windows just after drying off and around calving. In dromedary camels in northern Egypt, 38.5% of 390 lactating animals had mastitis (6.4% clinical, 32.1% subclinical); coagulase-negative staphylococci, E. coli and S. aureus were the commonest isolates, and age over five years, early lactation, tick infestation, poor milking hygiene and teat lesions raised the risk.

Mammary gland (udder quarters), teat and teat canal, milk

Pre- and post-milking teat disinfection, recommended milking procedures, clean dry cool housing and bedding, antibiotic dry cow therapy with internal teat sealants, culling chronically infected cows, and core-antigen coliform vaccines to reduce severity.

Local cases with abnormal milk and a swollen gland usually resolve; about 10% of clinical coliform cases become systemic, and some of those cows die. Staphylococcus aureus infections are much harder to cure, even with dry cow therapy.