Correlating the immune response with the clinical-pathological course of persistent mastitis experimentally induced by Mycoplasma agalactiae in dairy goats.

Abstract

To correlate the clinical course of mycoplasma mastitis with its immune response, right mammary glands of 15 lactating goats were inoculating with 10(10) colony-forming units (cfu) of Mycoplasma agalactiae (Ma). Before sacrificing the animals at 5, 15 or 45 days post-inoculation (dpi), blood Ma antibody titres and milk mycoplasma colony and somatic cell counts were monitored. Ma colonised the mammary gland and milk counts increased to over 10(12)cfu/ml within 5 dpi. During this period, an innate immune response involving neutrophils and macrophages was observed, and Ma antigen appeared in the degenerated acinar epithelium. From 7 dpi, a specific antibody response coincided with reduced viable mycoplasmas in milk. The humoral immune response was limited; by 37 dpi, all animals scored negative for anti-Ma antibodies, and around 10(8)cfu/ml were shed. Results indicate an early immune response to Ma inoculation unable to control mycoplasmal invasion. An ensuing humoral response, despite reducing the mycoplasma burden, leads to chronic, persistent infection.