Toxoplasmosis in a calf.

Gross post mortem and histopathological changes are described in a calf with toxoplasmosis. The major pathological changes were restricted to the lungs and kidneys and comprised interstitial pneumonia with multifocal necrosis, and glomerular necrosis. Many pseudocysts were present in both organs. The calf had been in close contact with young cats, one of which was killed and examined and shown to have a high antibody titre to Toxoplasma gondii, although there was little histological evidence of infection. No antibodies to toxoplasma were detected in serum from the dam of the calf, and accordingly, it is suggested that the cat was the source of infection for the calf.     

Effect of salicylates on intestinal secretion in calves given (intestinal loops) Escherichia coli heat-stable enterotoxin

The inhibitory effect of salicylates on intestinal secretion in 1- to 5-day-old calves given Escherichia coli heat-stable enterotoxin (ST)-induced intestinal fluid response was investigated. Purified ST was diluted in isotonic saline solution to obtain 1:10, 1:25, 1:50, 1:75, and 1:100 dilutions. Each dilution (1 ml) was inoculated into ligated loops in the distal part of the jejunum of each calf. Acetylsalicylic acid (aspirin) given orally (100 mg/kg) at 4 hours before ST was inoculated did not substantially alter the intestinal fluid response to ST. Sodium salicylate (IV) infusion, begun simultaneously when, or at 1 hour after, ST was inoculated, significantly (P less than 0.05) decreased fluid accumulation in those loops inoculated with ST dilutions of 1:25 or greater. The sodium and potassium concentrations of the accumulated fluid did not differ significantly between or within treatment groups. These results indicate that sodium salicylate infusion may be beneficial in treating enterotoxic colibacillosis in calves. Aspirin given orally at the dose used in the present study, would not have any beneficial effect.     

Bovine genital campylobacteriosis (vibriosis): vaccination of experimentally infected bulls

The therapeutic efficacy of a Campylobacter fetus subsp venerealis bacterin was determined in experimentally infected bulls. Ten of twelve 5-year-old Angus bulls became infected after being infused intrapreputially with C fetus subsp venerealis. Of the 10 bulls, 6 were vaccinated with 5 ml of C fetus subsp venerealis vaccine on 2 occasions 4 weeks apart. Preputial washings of the vaccinated bulls were culturally negative by the 8th week after primary vaccination. None of the 18 heifers exposed to the vaccinated bulls became infected. The 4 infected, nonvaccinated bulls remained culturally positive to C fetus (P less than 0.002), and each bull infected at least 1 heifer (P less than 0.001). Two noninfected, nonvaccinated bulls remained culturally negative and did not infect any heifer. The 4 infected, nonvaccinated bulls were then vaccinated. Two bulls remained infected 9 weeks after primary vaccination, as determined by the virgin heifer test and cultural examination of preputial washings. Serologic data from 7 sampling periods were different (P less than 0.001) for vaccinated vs nonvaccinated bulls at 4 (against K antigen) or 6 (against O antigen) weeks after primary vaccination. Vaccination was effective in eliminating the infection in most of the infected bulls, but cannot be recommended as the sole measure of control in infected herds.     

Immunisation of pregnant sows with a live Salmonella cholerae suis vaccine

Sows were immunised subcutaneously with a live Salmonella cholerae suis (SCS) vaccine prior to farrowing. Serological tests demonstrated a high level of SCS colostral antibodies at parturition. Piglet sera negative for antibodies at birth contained a high level of SCS antibodies 24 h after the ingestion of vaccinated sow colostrum. Experiments were carried out to establish if these maternally derived antibodies could protect the piglets against an intranasal (IN) challenge with a field isolate of SCS. It was concluded that pregnant sows could be safely immunised with a live SCS vaccine thus providing their piglets with a passive immunity which protected them against an intranasal challenge.     

Lack of effect of selenium supplementation on the incidence of weak calves in dairy herds

A double blind controlled trial was carried out on four commercial dairy herds, to investigate the effect of one 50 mg injection of selenium, 10 days before parturition, on the incidence of weak calves. Although the treatment marginally increased the selenium status of treated calves it did not decrease the incidence of the weak calf syndrome.     

Lymphocyte alterations in zinc-deficient calves with lethal trait A46

Lymphocyte numbers and activities were evaluated at 2, 4, 8 and 12 weeks of age in two calves with lethal trait A46 (A46), a genetic disorder affecting intestinal zinc absorption. Plasma zinc concentrations declined to subnormal by 3 weeks of age, after which anorexia, diarrhea, alopecia and hyperkeratosis occurred. Lymphocyte response to phytohemagglutinin-P (PHA), concanavalin A (Con A) and pokeweed mitogen (PWM) stimulation was variably reduced. CD4+ T-lymphocytes were subnormal on at least one observation period following onset of zinc deficiency, and relative numbers of B lymphocytes were decreased at 8 weeks. Secondary antibody responses to bacteriophage phi X 174 were significantly reduced. The results demonstrate that calves homozygous for the A46 trait have normal numbers of functional lymphocyte subpopulations at birth, and that the activity of their lymphocytes is altered once the calves become zinc deficient.     

The humoral immune response of rainbow trout (Salmo gairdneri) immunised by various regimes and preparations of Aeromonas salmonicida antigens

Antibody production in rainbow trout to extracellular antigens was investigated. The following antigen preparations and immunisation regimes were used: native extracellular products (ECP) in Freund's complete adjuvant (FCA), intraperitoneally (i.p.) with and without booster; formalinized ECP in FCA, i.p. with and without booster; washed, formalinized A. salmonicida cells in FCA, i.p., with booster; native ECP in saline, i.m., four weekly injections at two different doses, 45 micrograms and 6 micrograms each injection (after the protocol of Shieh, 1985). Using crossed normal rainbow trout serum, i.p., single injection (after the protocol of Sakai, 1985). Using crossed immunoelectrophoresis all antisera contained precipitating antibodies to three to five ECP components except that from fish immunised i.m. with 6 micrograms protein where antibodies were undetectable. In no case were specific antibodies to ECP protease or haemolysin detected. In a rabbit immunised with formalinized ECP in FCA under a similar regime to the rainbow trout, antibodies to at least 15 ECP components, including protease and haemolysin, were detected. The assumption of a specific immune response to the protease, at least in respect of antibody production, in recent reports of protection afforded by vaccines composed of either crude ECP or partially purified protease (Shieh, 1985) or partially purified protease inactivated by normal serum (Sakai, 1985) is not supported by the present findings.