Retrospective studies of the trends of occurrence of ruminant mastitis pathogens in a veterinary teaching hospital in Northwest, Nigeria

A retrospective study to determine the pattern of isolation of mastitis causing organisms from milk samples of cattle, sheep and goats submitted to the Microbiology laboratory of the Department of Veterinary Pathology and Microbiology Ahmadu Bello University Zaria from 1980-1991 and 1999-2009 was conducted . The samples were subjected to cultural isolation and biochemical characterization. The results of the isolates were assembled, reviewed and summarised. A total of 227 milk samples were submitted from cattle (40), sheep (31) and goats (156) respectively, from the years 1980 to 1991 and 1999 to 2009 and subjected to cultural isolation and biochemical characterization. A total of 18 different organisms were isolated from 158 of the samples submitted. Six of the submitted samples were un-typeable while 63 were culture negative i.e showed no growth. The most commonly isolated mastitis causing organisms from all samples were: Staphylococcus aureus (26.51%), Escherichia coli (12.20%), Staphylococcus spp (10.24%), Streptococcus spp (6.63%) and Corynebacterium spp (7.32%). Other organisms are , Micrococcus (1.22%), α-hemolytic Streptococcus (1.83%), β- haemolytic Streptococcus (2.42%), Pseudomonas aeroginosa (4.88%), Enterobacter spp (1.83%), Proteus spp (4.89%), Lactobacillus spp (2.42%), Pasteurella spp (4.27%), Klebsiella spp (3.05%), Citrobacter spp (0.61%), Candida albican (0.61%), Flavobacterium spp (0.61%), Bacillus spp (3.67%), Acinetobacter spp (1.20%) and Sarcina spp (0.61%). Staphylococcus aureus was the most predominant organism isolated from cattle, sheep and goat milk. There was a significant reduction in occurrence of mastitis from 201 (88.55%) cases within 1980-1991 and 26 (11.45%) cases within 1999-2009.