Subclinical mastitis in dairy cattle and buffaloes among small holders in Egypt: Prevalence and evidence of virulence of escherichia coli causative agent

This study aimed first to estimate the prevalence of subclinical mastitis (SCM) among dairy cows and buffaloes of smallholders who sell milk directly to consumers through bulk tanks of milk distributors. The second aim is to estimate the prevalence of Escherichia coli in milk of SCM cases and identify its virulence genes and to emphasize the public health risk form drinking this milk. A total of 227 and 174 dairy cows and buffaloes, respectively from Kafrelsheikh Governorate, Egypt were examined with California Mastitis Test (CMT) to estimate the prevalence of SCM. Samples were also screened for E. coli using classical bacteriological and molecular methods. The prevalence of CMT-positive cows and buffaloes samples examined was 47.4% (49.9% and 44.3% for cows and buffaloes, respectively). Cows were found to be at a higher risk of getting high CMT score than buffaloes. E. coli was detected bacteriologically in 16.4% and in 27.2% of the CMT-positive cows and buffalo samples, respectively. A total of 83.1% and 75.6% of isolates were confirmed as E. coli using PCR technique. A multiplex PCR assay was used to identify five virulence genes in the E. coli isolates; the eae gene for enteropathogenic E. coli, stx for Shiga toxin-producing E. coli, elt and est for enterotoxigenic E. coli, and the hlyA of the enterohemolysin gene for enterohemorrhagic E. coli. Only one E. coli strain identified carried two virulence genes (eae and est). The high prevalence of SCM among dairy cows and buffaloes in the study area indicated that there is high risk to consumers who consume milk of these animals. Also, control of SCM is a prerequisite among smallholders in Egypt in order to minimize its deleterious effects such as microbial antibiotic resistance and public health hazards. To our knowledge, this is the first study that highlights the ecology of virulence by E. coli causing SCM in Kafrelsheikh governorate, Egypt. This study offers the basis for further phenotypic and molecular characterization of E. coli found in raw milk in order to guarantee safe consumption of raw milk and milk products.