Recipient Organization
IOWA STATE UNIVERSITY
2229 Lincoln Way
AMES,IA 50011
Performing Department
Veterinary Medicine
Non Technical Summary
Preweaning respiratory disease in the suckling beef calf has a significant negative effect on the profitability of Iowa's cow/calf operations. While the incidence of calf diarrhea is higher in the very young calf, calf pneumonia typically affects calves after they have been turned out on summer range. This increases the difficulty in handling these calves in order to make an etiological diagnosis and render effective treatment. It also explains in part, why well designed antemortum field investigations in this area of beef production have not been published. Research aimed at better defining the role of the various respiratory pathogens in suckling calves would be useful in refining preventative programs at the ranch level and improving vaccine efficacy. It is our belief that the basic research studying the etiology of suckling calf pneumonia is not conclusive. Studies that have explored the causes of this condition have typically utilized only diseased animals or postmortem diagnostics. Simply because a particular organism is isolated from a diseased calf does not necessarily mean that it was responsible for the clinical signs. This is especially true for calves that received antimicrobial prior to testing. Case-control studies allow investigators to evaluate the presence of pathogens in diseased and normal cohorts from the same herd. Differences in pathogen isolation between these two groups allow for a better understanding of how the presence of these organisms affects the incidence of disease.
Animal Health Component
(N/A)
Research Effort Categories
Basic
(N/A)
Applied
(N/A)
Developmental
(N/A)
Goals / Objectives
The objectives of this protocol are as follows: 1. Determine the cause of respiratory disease in suckling beef calves through the use of nasal swabs, skin biopsy ("ear notch"), and transtrachael wash (TTW). 2. Compare the rate of isolation / identification of respiratory pathogens in clinically ill animals with those identified from clinically normal herdmates. 3. Isolate and store bacterial pathogens so that future genotyping can be performed to determine differences based on location in the animal (TTW vs. nose) and disease status (clinical vs. control).
Project Methods
Approximately 30 Iowa veterinary practitioners will be recruited to identify client herds that have a history of respiratory disease in suckling beef calves while on summer pasture. Our plan is to identify at least 40 individual calves with respiratory disease and collect diagnostic samples from that calf and two normal herdmates. In order to be included in this study, calves must be at least 45 days of age and nursing their dam in a pasture environment. The age criterion is designed to eliminate calves exhibiting respiratory disease as a secondary complication of primary calf scours. Calves that have been vaccinated for respiratory disease are not eligible to be sampled. Diagnosis of respiratory disease will be made by the practitioner and based on clinical signs and a rectal temperature of 104˚F (40˚C). Calves are eligible to be enrolled in this trial between May 15 and September 15, 2011 provided that they have not been weaned or removed from a pasture environment. At the time a clinical calf is identified, two normal herdmates (control calves) will be randomly chosen from a list of all test eligible calves in the herd. This random selection will prevent practitioner and producer bias in selection of these control calves. Calves will only be used once in the control group to prevent multiple transtrachael washes and to simplify data analysis. However, if a "control" calf becomes clinically ill at a later date, they are eligible to be sampled with two additional normal herdmates. A maximum of three clinically ill calves with respiratory disease will be eligible for enrollment from any one specific herd. Clinical and control calves will all be sampled in the same way. A single nasal swab and transtrachael wash will be collected from all three calves and submitted to the ISU Veterinary Diagnostic Lab (ISU-VDL). Serum (red top tube) will be collected from each calf in order to determine haptoglobin level. Saline from the TTW will be submitted to the ISU VDL for bacterial culture and sensitivity and PCR for IBR, BRSV, BVD, BCV, and Mycoplasma bovis. Nasal swabs will be submitted to ISU VDL for PCR for M. bovis and IBR. All calves will be "ear notched" and screened by IHC for BVD-PI status by ISU VDL. The practitioner will be available to necropsy any dead calves. Necropsy samples from dead calves will be processed through ISU-VDL at the discretion of the pathologist (Cooper). Based on previous work in dairy calves, we are assuming that there will be a difference of at least 25% in respiratory pathogen isolation rate for the control calves compared to the clinically ill calves (30 vs. 56%). This isolation rate may originate from the TTW, the nasal swab, or a combination of both. This will give us a minimum detectable odds ratio of 3.0 that a particular bacteria or virus is associated with a case of respiratory disease.