Any foreign substance in the mammary gland will increase somatic cell count (bacteria, injury, etc.). Toxins from E. coli can cause acute mastitis leading to abnormal milk, high temperature, dehydration, and loss of the quarter and/or cow. Toxins are dangerous to the cow and can be released by a variety of organisms.
Mike Hutjens, Extension Dairy Specialist, University of Illinois - Illini DairyNET
Indeed, many mastitis-causing bacteria can release toxins that cause increased somatic cell counts (SCC) as well as the systemic signs described by Dr. Hutjens. This can include mastitis bacteria not so commonly thought of as "toxic," such as some strains of Staphylococcus aureus. Mycotoxins have been studied on a limited basis relative to SCC. Whether fed orally or infused into the mammary gland (infection through the mammary gland is considered unlikely, according to Dr. Duarte Diaz), no direct effect of mycotoxins on SCC has been observed in cows or goats. It is possible that because mycotoxins at a high enough dose are often found associated with suppressed immune response of cows, they may be associated with increased mastitis and thus indirectly with increased SCC as a result of mastitis. However, in mice fed the mycotoxin T-2 toxin, the immune response against E. coli mastitis was improved relative to control mice. At this time, there is no evidence that mycotoxins lead to increased SCC.
Dave Wilson, Dairy Extension Veterinarian, Utah State University
