A cross-Sectional Study of Bovine Mastitis In and Around Bahir Dar and Antibiotic Resistance Patterns of Major Pathogens
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Date
2004-06
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Addis Ababauniversity
Abstract
Three hundred fifty one (195 local zebu and 156 Holstein x Local Zebu) lactating cows of
smallholder private farms in Bahir Dar milk shed were examined from September, 2003 to
March, 2004 to determine mastitis prevalence, isolate pathogens involved, evaluate the
antibiotic susceptibility profiles and to evaluate somatic cell count in identifying
intramammary infections. Clinical prevalence was determined through examination of
abnormalities of milk, udder or cow. California mastitis test (CMT) and culture were used for
subclinical mastitis determination. Agar disc diffusion was used for antibiotic susceptibility
test. Somatic cell count was conducted following standard procedures described in
International Dairy Federation for enumeration of cells with direct Microscopic method.
Clinical prevalence at cow level was 3.9% in crossbreds and none in local zebu breeds.
Subclinical mastitis at cow level based on CMT was high (34.4%) in crossbreds compared to
indigenous zebu (17.9%) (p < 0.05). Quarter subclinical prevalence based on CMT was
17.90% and 4.95% for crossbreds and local zebu, respectively. Among potential risk factors
considered, stage of lactation, parity and breed were found to affect the occurrence of mastitis
significantly (p < 0.05). The pathogens isolated from mastitic milk were coagulase negative
staphylococci (CNS), S. aureus, Str. agalactiae, Str. dysgalactiae, Str. uberis, Micrococcus
species, C. bovis, A. pyogens, B. cereus, and S. intermedius. Among these, the most frequent
isolates were CNS (49.6% of the total isolates), S. aureus (17.9%), Str. agalactiae (8.2%) and
Str. dysgalactiae (6.7%).
Seven antibiotics including sulfisoxazole, tetracycline, erythromycin, oxacillin,
chloramphenicol, clindamycin, and streptomycin were tested on 81 isolates. Except for
streptomycin, all isolates were sensitive to all antibiotics. All isolates were most sensitive to
sulfisoxazole. Staphylococcus aureus was susceptible to all drugs except streptomycin.
Staphylococcus aureus was 91.7% susceptible to oxacillin, however, CNS were less
susceptible (68.2%) in vitro.
To evaluate somatic cell count (SCC) in identifying intramamary infection for crossbreds, 10
cutoff points between 100000 cells/ ml and 300000 cells/ml were evaluated for their
sensitivity and specificity in comparison with cultural results. Similarly, cutoff points between
80000 cell/ml and 250000 cell/ml were taken for local zebu breeds. The sensitivity for
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crossbreds range from 79.16 % (at 300000 cells/ml cutoff point) to 95.80 % (at 100000 cells/
ml) and similarly specificity from 80.28% to 45.52%. For local zebu breeds in the same order,
sensitivity range from 58.82% to 88.23% and specificity from 45.82% to 85.15%. To
establish threshold level this study was a first attempt in Ethiopia and to use SCC as a
diagnostic tool on a national scale further study need to be conducted with improved cultural
technique and automatic cell counters. Cross breed cows had high SCC compared to local
zebu cows. The SCC was significantly (p<0.05) affected by infection status, breed and late
lactation stage.
Keywords: clinical / subclinical mastitis/ prevalence/ bacterial isolate/ antibiotic
susceptibility / Somatic Cell Count / threshold / crossbred / zebu
Description
Keywords
clinica, subclinical mastitis, prevalence, bacterial isolate, antibioticsusceptibility, Somatic Cell Count, threshold, crossbred, zebu