Vaccination of the brushtail possum (Trichosurus vulpecula) against Mycobacterium bovis infection with bacille Calmette-Guérin: the response to multiple doses.

In New Zealand, the brushtail possum (Trichosurus vulpecula) is the principal wildlife vector of bovine tuberculosis. Control of infected possum populations contributes to the control of tuberculosis in domestic livestock. Vaccination is potentially a complementary strategy to population control, but to be cost-effective, administration of the vaccine to possums would need to be from an appropriately designed automatic vaccinator. Possums themselves would activate the vaccinator so that it would deliver an aerosol spray of vaccine. There would be no direct way to prevent possums receiving multiple doses of vaccine. This study examined the effect on protective immunity of repeated vaccination. Captive possums were vaccinated with BCG strain pasteur 1173P2 either 12 times at weekly intervals, twice at 6-weekly intervals, or once. Vaccination was by a combination of intranasal aerosol and conjunctival instillation. Eight weeks after the last dose of vaccine, all possums were challenged intratracheally with Mycobacterium bovis strain 83/6235. Vaccination induced a significant immune response as measured by the lymphocyte proliferation assay (LPA). A significant level of protection, as measured by the response to challenge, developed in all the vaccinated possum groups, but protection was greatest in the group vaccinated 12 times. It was concluded that protection would be enhanced if vaccinations were repeated at short intervals (weekly), but no benefit or detriment resulted from revaccination after longer intervals (1-2 months).     

Nitrogen retention and performance of brown laying hens on diets with different protein content and constant concentration of amino acids and energy.

1. The aim of this study was to determine the nitrogen balance and the performance of laying hens fed on diets with a protein content lower than the diets currently used in commercial practice but with adequate concentrations of lysine, sulphur amino acids, tryptophan and threonine. 2. Ninety-six Hy-Line Brown hens, 24 weeks old, were divided into 3 groups of 8 replicates and received, for 16 weeks, diets formulated to have 3 different protein concentrations: 170 (control), 150 and 130 g/kg CP and the same energy content. For each protein concentration, the contents of lysine, methionine, methionine+cystine, tryptophan and threonine were maintained at minimum requirement concentrations by supplying synthetic amino acids. 3. In the first half of the trial, egg production and egg weight were similar in all groups. From the 9th week onwards group 150 CP laid heavier eggs and had a slightly lower egg deposition and total mass. Food conversion ratio was best in the control group. 4. Nitrogen intake was related to the protein concentration of the diet, the food intake being almost the same in the 3 experimental groups. Faecal nitrogen content significantly and linearly decreased with reduction in dietary protein content and was about 50% of the intake. Considering the nitrogen faecal/intake ratio, the 150 CP group showed better nitrogen utilisation at each sampling time.     

Evaluation of an enzyme-linked immunosorbent assay for diagnosis of trichinellosis in swine.

Experimental and field trials were conducted to evaluate an ELISA for its ability to detect Trichinella-infected domestic swine and to compare ELISA results with muscle-digestion test results. The ELISA used was a commercial double-antibody kit, containing an excretory-secretory antigen, and was evaluated principally for epidemiologic use. Experimentally induced infection in swine (4 groups of 3 pigs each; inoculated with 0, 50, 500 or 5,000 larvae) was detected as early as postinoculation week 4, with seroconversion of all inoculated swine by postinoculation week 8. The rate of seroconversion appeared to be affected by initial larval dose, time after inoculation, and immunocompetence of the individual host. Determination of antibody kinetics generally revealed rapidly increasing antibody titer, followed by its steady decrease in most pigs. Once seropositive, however, all pigs remained seropositive for the duration of the 10-week study. Presence of muscle larvae was confirmed in all infected pigs at termination of the study. We recognize that the experimental conditions may not be truly representative of those under which natural infection develops in pigs; however, the ELISA detected an infected pig with muscle larval density of 0.87 larvae/g of tissue. Results of a field trial (n = 310) indicated no muscle digestion test-positive pigs (35 g of diaphragm muscle digested/pig), but 3 samples tested positive by ELISA for specificity of 99.0%.     

Chronic partial obstructive urolithiasis causing hydronephrosis and chronic renal failure in a steer.

A 13-month-old Angus steer was examined with a 6-week history of lethargy, malaise and dribbling urine. Laboratory exam revealed crystalluria and poor renal function. Ultrasound revealed hydronephrosis and hydroureter. Euthanasia was chosen because of a poor prognosis for economic recovery. Necropsy demonstrated numerous calculi causing partial urethral obstruction approximately 25 cm from the end of the penis. Secondary renal changes were confirmed. Urolithiasis occurs commonly in ruminants. Secondary obstruction is usually complete with severe consequences. This is the first report of chronic partial obstructive urolithiasis resulting in endstage renal disease.     

Comparison of media to isolate Staphylococcus aureus from teat skin and milking unit liners.

Four procedures were compared for isolation of Staphylococcus aureus from swabbing solutions of teat skin and milking unit liners from commercial dairies. In 2 procedures, 0.1 ml of swabbing solutions were added to either 5 ml Vogel-Johnson or Baird Parker broth media and enriched at 37 degrees C, 4 h. Following enrichment, 0.1 ml culture was transferred to modified Baird-Parker agar and incubated at 37 degrees C, 48 h. In the other 2 procedures, 0.1 ml of swabbing solution was directly placed on either blood or modified Baird-Parker agar plates and incubated at 37 degrees C 48 h. Combining results from all methods, Staphylococcus aureus were isolated from 72 of 913 (7.9%) skin samples, and 34 of 268 liners (12.6%). On average, 43.1% (31/72) of the S. aureus isolates were found by the enrichment in liquid Vogel-Johnson procedure. The average isolation percentage for other methods ranged from 19.4% to 25.0%. Isolation of S. aureus from milking unit liner or teat skin swabbing solutions was approximately twice as likely after enrichment in Vogel-Johnson liquid media as opposed to other methods of isolation. This indicates that enrichment in Vogel-Johnson liquid media improved recovery of S. aureus from swabbing solutions.