Novel bivalent vectored vaccine for control of myxomatosis and rabbit haemorrhagic disease.

A novel, recombinant myxoma virus-rabbit haemorrhagic disease virus (RHDV) vaccine has been developed for the prevention of myxomatosis and rabbit haemorrhagic disease (RHD). A number of laboratory studies are described illustrating the safety and efficacy of the vaccine following subcutaneous administration in laboratory rabbits from four weeks of age onwards. In these studies, both vaccinated and unvaccinated control rabbits were challenged using pathogenic strains of RHD and myxoma viruses, and 100 per cent of the vaccinated rabbits were protected against both myxomatosis and RHD.

Canine parvovirus type 2 vaccine protects against virulent challenge with type 2c virus.

The ability of dogs vaccinated with a live attenuated CPV type 2 (Nobivac Intervet) vaccine to resist challenge with a current CPV2c isolate was investigated. Six SPF beagle dogs were given the minimum recommended course of vaccination, comprising a single inoculation of vaccine (Nobivac Lepto+Nobivac Pi) at 8-10 weeks of age followed 3 weeks later with a parvovirus vaccine in combination with distemper, adenovirus and parainfluenza virus (Nobivac DHPPi) and a repeat leptospirosis vaccine. Six control dogs were kept unvaccinated. All animals were challenged orally with a type 2c isolate of CPV and monitored for clinical signs, virus shedding, white blood cell fluctuations and serological responses. All vaccinated dogs were fully protected; showing no clinical signs nor shedding challenge virus in the faeces, in contrast to control animals, which displayed all the typical signs of infection with pathogenic CPV and shed challenge virus in the faeces.

Efficacy of feline panleucopenia vaccine to prevent infection with an isolate of CPV2b obtained from a cat.

Cats vaccinated against FPLV were protected against infection with a feline isolate of CPV2b. Nonvaccinated cats developed a lymphopenia and excreted virus which infected susceptible in-contact cats.

Comparison of isolates of canine parvovirus by restriction enzyme analysis, and vaccine efficacy against field strains.

Canine parvovirus isolates from clinical cases of enteritis were obtained from the United Kingdom, Germany and the USA and differentiated by restriction enzyme analysis into three groups, namely CPV2, CPV2a and CPV2b. The three groups were readily identified by their HphI restriction profile. CPV2 was not prevalent in cases of canine parvovirus disease after 1986. Only two CPV2 strains (original type) were found among 110 strains isolated after 1980. In Europe the frequency of isolation of the CPV2a and CPV2b field strains was similar whereas in the USA the CPV2b strain predominated. Dogs inoculated with a vaccine strain were resistant to infection after challenge with UK isolates of CPV2a and CPV2b.

Isolation of lambda amp3 genomic recombinants coding for antigens of Eimeria tenella.

Eimeria are the causative agents of coccidosis, a disease which is of world wide economic importance in the poultry industry. Immunity resulting from infection is species-specific and both antibody and cell-mediated responses have been implicated. As an initial step in the development of a genetically-engineered vaccine against coccidiosis, libraries of EcoRI-digested genomic DNA from E. tenella have been constructed in Escherichia coli using the expression vector lambda amp3. Screening of the libraries with serum from chickens immunized by infection has identified at least 24 different recombinant phage which produce eimeria antigens fused to beta-galactosidase. A significant proportion of the Eimeria DNA inserts cross-hybridise with each other and contain sequences which are highly represented in the genome. The identification of these clones will enable the isolation of intact genes from E. tenella DNA and facilitate detailed analysis of the antigens and immune responses.

Biochemical changes in layer and broiler chickens when fed on a high-glucosinolate rapeseed meal.

Diets containing 500 g high-glucosinolate rapeseed meal/kg or an equivalent amount of soybean meal as the only protein supplement were fed to layer-type chickens and two broiler strains from 1 to 56 d of age. Additional groups of the former were maintained on the diets until they were 16 and 28 d old. The rapeseed meal produced thyroid hypertrophy in all strains but reduced the growth rate of only one of the broiler strains. The livers of chickens fed on rapeseed meal were enlarged and DNA analysis indicated hyperplasia, but no macroscopic lesions were found. The activities of aspartate transaminase, lactate dehydrogenase and alkaline phosphatase in the plasma were increased by rapeseed meal, suggesting liver damage. In all strains, feeding rapeseed meal increased plasma total protein, albumin and cholesterol and decreased urate. Hyperglycaemia accompanied by a decrease in plasma triglycerides occurred in the layer strain. Through its extra-thyroidal toxicity (-)5-vinyl-oxazolidine-2-thione (goitrin) was probably responsible for most of these changes.

The effect of thionamides and related compounds on trimethylamine oxidase activity in hepatic microsomes isolated from chickens (Gallus domesticus).

1. Thiourea, ethylene thiourea, methimazole and (+) 5-vinyl-oxazolidine-2-thione (OZT) gave similar inhibition curves when added to the reaction mixture. A concentration of 20 microM reduced the activity by over 75%. Thioacetamide and thiobenzamide also behaved as potent inhibitors. 2. (-) OZT had less effect than the (+) isomer. 3. Microsomes from chickens with an inherently low capacity for synthesising TMA oxidase and enhanced susceptibility to the goitrogenic effects of OZT were more sensitive to this inhibition than those from a high TMA oxidase strain. 4. Inhibition by thiourea was competitive and the apparent K1 for low oxidase microsomes was 2.5 x 10(-6)M. 5. The inhibitory property of thionamides was lost when the S atom was replaced by O but was retained when it was oxidised to the sulphinic acid or sulphoxide. 6. Incubation of microsomes with sodium diethyldithiocarbamate reduced their TMA oxidase activity. 7. Sulphonium compounds, glucosinolates and antithyroid compounds with no thionamide group, including potassium thiocyanate, had no marked effect on the activity of the enzyme.

Thyroid function in relation to trimethylamine oxidation in immature domestic fowl fed on rapeseed meal.

1. Two groups of 12-week-old female chicks were selected for their ability to oxidise 14C-trimethylamine (TMA) after being fed on a diet containing 100 g high-glucosinolate rapeseed meal (RSM)/kg for 14 d. A third group (control) was fed on a rapeseed-free diet. Measurements of thyroid activity and hepatic TMA activity were made after a further week on the diets. 2. After feeding RSM, hepatic TMA oxidase oxidase was very low (P less than 0.001) in one group (sensitive) but was unaffected in the other group (resistant). Thyroid size was increased in both groups receiving RSM but was larger (P less than 0.001) in sensitive birds. 3. Plasma half life of thyroxine (T4) and its metabolite clearance rate were not affected by feeding RSM; thyroidal secretion was reduced (P less than 0.05) to the same extent in both groups. 4. Plasma concentration of triiodothyronine was decreased in both groups after feeding RSM (P less than 0.05); plasma T4 concentration was increased (P less than 0.05) only in sensitive birds. 5. The results indicate that the short-term depression of TMA oxidation in birds sensitive to RSM is not mediated by the thyroid.