Development and Application of a Minnesota Dairy Health Surveillance Network

NON-TECHNICAL SUMMARY: Infectious pathogens in food animal production systems are of great significance to food animals, producers, and consumers, as well as to local and national economies. Federal agencies (USDA-APHIS-NAHSS) have stated the need to develop national animal disease surveillance systems. However, it may be necessary for individual States to take the lead in initiating such programs. We propose the creation of an ongoing dairy health surveillance network in MN. Once the platform of the surveillance network is established, the second goal will be to initiate a series on ongoing long-term surveillance projects and pilot studies, applied within the network. The surveillance program will allow us to identify and better understand possible relationships between herd management practices and issues of food safety or public health concern, to describe trends in disease rates and agents over time, or to identify when important changes occur. This information may be used to develop new strategies to limit their impact on animals and producers, and to reduce or eliminate risks to consumers through the food supply. Programs must also be in place to rapidly detect and react to new (foreign, emerging or introduced) infectious disease threats, to detect new virulence patterns in existing pathogens, or to detect shifts in antimicrobial resistance patterns for pathogens of concern to both animal and public health. The network will initially focus on two surveillance projects describing contagious mastitis pathogens in cows and enteric pathogens in calves. <P>Objective 2. We will describe the proportion of surveillance herds positive for S. aureus in bulk tank milk, the prevalence of S. aureus isolates classified as MRSA, antimicrobial sensitivity patterns for S. aureus, and within-herd and between-herd genetic variation for S. aureus isolates. Objective 3a. We will describe the within-herd prevalence of fecal shedding of E. coli in calves, the prevalence of STEC, and how genetic variability and antimicrobial sensitivity patterns for these isolates change over time. Objective 3b. We expect to identify several associations between calf- or herd-level management factors and shedding of E. coli in calf feces. The results of the surveillance projects will be reported to describe and establish a baseline for outcomes of interest (e.g. within and between herd prevalence and level of shedding, genetic diversity, antimicrobial sensitivity patterns) for the targeted infectious agents. Once a baseline is established, changes in patterns of shedding, diversity of isolate serotypes, or antimicrobial sensitivity patterns for targeted infectious agents will be reported, if they are seen to arise. The associations identified will serve to generate new hypotheses surrounding the epidemiology of these infectious agents (e.g. risk factors for introduction, methods of prevention). Once risk factors are identified, this should lead to the development of new technologies or strategies to reduce or minimize the risks these infectious agents pose to either animal or public health. The efficacy these proposed interventions would be tested in future studies.<P>

APPROACH: Objective 1. Initiate a Minnesota Dairy Health Surveillance Network. Fifty dairy herds, representing the three major milk producing areas in MN, will be enrolled. We will electronically capture monthly Dairy Herd Improvement (DHIA) test day records. Twice annually the study technician will administer a questionnaire to participating producers describing facilities and management strategies. DHIA records and questionnaire information will be entered into a comprehensive database and used to establish baseline patterns within herds, to identify when important changes occur, and to investigate if certain herd management-related factors are associated with outcomes (e.g. specific infectious pathogens) under surveillance. <P>Objective 2. Surveillance Project 1 - Staphylococcus aureus: Describe the epidemiology of Staphylococcus aureus in MN dairy herds, with emphasis on methicillin-resistant Staphylococcus aureus (MRSA). Producers will record clinical mastitis events and treatments. Three times per year bulk tank milk samples will be collected for culture. Isolates of S aureus will undergo further testing to describe antimicrobial sensitivity patterns (MIC) and to detect the presence of oxacillin resistance. <P>Objective 3.a. Describe the epidemiology of Escherichia coli in MN dairy calves, with emphasis on Shiga toxin producing E. coli (STEC). Producers will record all clinical disease events in calves and methods of treating sick calves. The study technician will visit herds 3 times per year to collect fecal swabs from five randomly selected calves between the ages of 21 to 42 days of age. Fecal swabs will undergo laboratory testing to identify E. coli isolates, shiga toxin-encoding E. coli, and antimicrobial sensitivity patterns of E. coli. Objective 3.b. Investigate the relationship between specific herd- and animal-level factors and antibiotic resistance patterns in fecal Escherichia coli of dairy calves (Cohort study). This study will include a subset of 15 of the surveillance herds feeding preweaned calves either i) medicated milk replacer, ii) non-medicated milk replacer and iii) non-saleable whole milk (5 herds representing each cohort). Five calves between 1-7 days of age will be enrolled on each farm. Enrolled calves will be sampled using fecal rectal swabs at: 1-7 days, 21-42 days, and 10-12 weeks of age. Fecal swabs will undergo culture and further testing to identify the presence of E. coli, description of E. coli subtypes, and the variation in antimicrobial sensitivity patterns for these isolates.