IMMUNISATION OF CATTLE AGAINST VIBRIOSIS WITH VACCINES PREPARED FROM CAMPYLOBACTER FETUS SUBSP FETUS

Subcutaneous administration of vaccines prepared from cells of Campylobacter fetus subsp fetus strain A28 to heifers gave substantial protection against infertility due to C. fetus subsp venerealis strain B6. Strains A28 and B6 had different heat-stable antigens and conformed respectively to serotype B and serotype A of Berg et al (1971). The results suggested that the protective antigens were heat-labile antigens common to both strains. Although vaccines prepared from serotype B strains of C. fetus subsp fetus could be used to immunise cattle against vibriosis, the results did not suggest that their use in preference to those prepared from C. fetus subsp venerealis would offer any advantages.     

THE IMMUNISATION OF CHICKENS AGAINST INFECTIOUS AVIAN ENCEPHALOMYELITIS

An immune response was induced in chickens vaccinated with the NSW-1 virus by the intramuscular, eye drop, wing web or oral methods. The oral procedure was the most sensitive in inducing an immune response with the lowest dose of virus. The wing web method was the least sensitive. Clinical IAE developed in 1 chicken following intramuscular vaccination. The virus was recovered from the faeces of chickens vaccinated orally with 700 CID50 of the virus from the third to the tenth day after vaccination.     

COMBINED ACTIVE-PASSIVE IMMUNISATION OF HORSES AGAINST TETANUS

The protection afforded by active, passive and combined active-passive methods of immunisation against tetanus was examined in previously unimmunised horses. Three groups of horses were injected; one with tetanus toxoid alone, one with tetanus antitoxin alone and one in which the tetanus toxoid and tetanus antitoxin were injected simultaneously. The protection afforded was determined by monitoring the levels of antitoxin achieved in the horses by each of these methods.
The results obtained demonstrated the effectiveness of the combined active-passive method in affording rapid and prolonged protection and enabled the examination of some of the factors involved in active and in passive immunisation when used alone. The advantages obtained by the use of the combined active-passive method in protecting unimmunised horses suddenly placed at risk to infection are outlined.     

THE EFFECT OF DERMALLY APPLIED LEVAMISOLE AGAINST THE PARASITIC NEMATODES OF CATTLE

A series of trials to establish the anthelmintic efficiency of levamisole, when applied dermally to calves, is described. The levamisole base was formulated in a suitable solvent system at 100 g/l and applied dermally at a dose rate of 8 mg base/kg. This gave efficiencies of 97.1-100%, 88.5-100%, 100%, 98.7-100% and 89.2-100% against adult Haemonchus placei, Ostertagia spp, Cooperia spp, Oesophagostomum radiatum and Trichostrongylus axei, respectively. Activity against the immature stages of H. placei was recorded at 100%, and against immature Cooperia spp the range was 96.3-100%. Extremely variable results were obtained against immature Ostertagia spp, efficiency ranging from 0% to 100%. Efficiency against adult Dictyocaulus viviparus was in the range of 84-100%. The potential advantage of a dermally applied anthelmintic is discussed.     

ACTIVE IMMUNISATION OF HORSES AGAINST TETANUS INCLUDING THE BOOSTER DOSE AND ITS APPLICATION

Successful active immunisation of horses against tetanus is dependent on a number of factors of which the toxoid preparation used, its method of application and the ability of the individual horse to respond are fundamental. Two immunisation schedules using an aluminium-based toxoid preparation were examined and the protection determined by monitoring the level of antitoxin afforded by each schedule. The results obtained demonstrated that 2 doses of this toxoid are necessary to ensure 12 months protection in all horses. These results are discussed in relation to the factors involved in active immunisation against tetanus.
Reference is also made to the occurrence of a transient phase of reduced levels of antitoxin following booster doses of toxoid in immunised horses during which it is considered these horses could become more susceptible to tetanus. The effect of a booster dose on immunised horses was examined and while there can be a reduction in the level of antitoxin in some immunised horses following this dose its effect is minimal, short-lived and for all practical purposes can be disregarded. The application of the booster dose in practice is also discussed.     

EFFICACY OF ANTHELMINTICS AGAINST CATTLE NEMATODES

The efficacies of fenbendazole and thiabendazole against artifically acquired cattle nematodes and the efficacies of fenbendazole, prabendazole and levamisole against naturally acquired cattle nematodes were studied in western Victoria. Fenbendazole significantly (P less than 0.05) reduced numbers of late and early fourth stage larvae (greater than 96%), artificially acquired Cooperla spp (100%) and naturally acquired adult Ostertagia ostertagi (98%) and Trichostrongylus axei (90%). Thiabendazole significantly reduced numbers of artificially acquired late fourth stage larvae (83%) and parbendazole significantly reduced numbers of adult O. ostertagi (72%) in one group of cattle. Fenbendazole was the most effective anthelmintic.     

THE TOXICITY OF CASSIA OCCIDENTALS FOR CATTLE

SUMMARY An investigation into the toxicity of Cassia occidentalis seeds was undertaken to confirm the toxicity of this species and to more fully characterise the pathology of the condition. Hammermilled seeds were given to calves by stomach tube. Five calves died and 3 were killed in an advanced stage of intoxication 6 to 9 days after the last dose. Clinical signs observed included diarrhoea, anorexia, reluctance to move, stumbling swaying gait, recumbency, tachycardia and dyspnoea in the terminal stages. Red-brown urine was present in most calves from the fourth day. Terminally, there was a neutrophilia and greatly elevated serum GOT and CPK levels. Autopsy revealed pale skeletal muscles of the upper pelvic limb and a characteristic red stippling giving a banded appearance in some affected muscles. Marked pulmonary oedema was present and the myocardium had a streaky mottled brown appearance. Light and electron microscopic examination revealed severe myodegeneration of skeletal muscles, myocardiopathy and focal hepatic necrosis.