Effect of Eperythrozoon ovis on the lysis of sheep erythrocytes in the complement fixation test.

When erythrocytes from sheep experimentally infected with Eperythrozoon ovis were used in the titration of reagents for a standardised complement fixation test, increased amounts of both haemolysin and complement were required for erythrocyte lysis compared with preinfection titrations. The haemolysin requirement increased by up to 125% at 55 days post-infection and complement requirement increased by up to 40% at 40 days post-infection. These changes appeared to correlate with the development of a macrocytic anaemia in affected sheep rather than E. ovis parasitaemia. The results emphasise the need to carefully monitor the haematological parameters of sheep used as sources of erythrocytes for the complement fixation test.

Histopathology of experimental brucellosis in rams following vaccination with Brucella ovis.

Lesions induced by inoculation of Brucella ovis into the epididymis were compared in rams previously vaccinated with B. ovis bacterin and unvaccinated rams. Inoculation of killed B. ovis did not produce significant lesions in either group whereas prior vaccination exacerbated epididymal lesions following inoculation of live B. ovis. Increased numbers of neutrophils, macrophages and lymphocytes were present in the interstitium and neutrophilic infiltration of the epididymal duct epithelium and intraepithelial cyst formation was more prominent. The inflammatory response surrounding extravasated spermatozoa was more severe in vaccinated rams but it was not determined if the response was directed at spermatozoa or intermixed brucellae, or both.

Comparison of the enzyme-linked immunosorbent assay and complement fixation test for detecting Brucella ovis antibodies in sheep.

A solid-phase, indirect, enzyme-linked immunosorbent assay (ELISA) was compared with the microtitre complement fixation test for detecting Brucella ovis antibodies in 220 ram sera. The ELISA was more sensitive than the complement fixation test; it demonstrated antibodies in 11 sera from known infected or vaccinated rams that were complement fixation test negative. No false positives were recorded with the ELISA and, in 36 sera positive to both tests, the ELISA titres were consistently higher than the corresponding complement fixation test titres.

Tracheitis in sheep after oral administration of a mineral supplement.

Outbreaks of illness and deaths in sheep after the concurrent administration of a cobalt, copper and zinc mineral supplement and laevamisole are described. Clinical illness was characterised by profound dyspnoea and inability to exercise. The consistent postmortem finding was severe, necrotising tracheitis with partial occlusion of the airway. This lesion was reproduced experimentally by intratracheal administration of the mineral supplement dissolved in one particular formulation of laevamisole but not in water or another preparation of laevamisole. Further experiments revealed that combined zinc sulphate and copper sulphate dissolved in the particular formulation of laevamisole would produce the tracheal lesions.

Pathology of experimental Histophilus ovis infection in sheep. II. Pregnant ewes.

Intravenous inoculation of Histophilus ovis to pregnant ewes at mid or late gestation resulted in acute bacterial endometritis, placentitis and foetal death. There were no lesions in the foetuses but H. ovis was recovered from the uteri of the ewes and the placentas. Oral or intravaginal administration had no effect.

Serological comparison between Histophilus ovis, Actinobacillus seminis and Brucella ovis.

The serological relationships between 4 strains of Histophilus ovis, the neotype strain of Actinobacillus seminis and Brucella ovis were examined using a cross-absorption complement-fixation technique. It was found that the 4 strains of H. ovis were serologically homologous and that an incomplete relationship existed between these organisms and A. seminis. Anteriserums prepared against one strain of H. ovis and the strain of A. seminis gave a weak, apparently non-specific cross-reaction with Br. ovis antigen. The practical significance of these results is discussed.

Pathology of experimental Histophilus ovis infection in sheep. I. Lambs.

Inoculation of lambs either intravenously or intranasally with Histophilus ovis resulted in septicaemia. There was bacterial thrombosis and vasculitis in the liver, lung, kidneys and heart. These lesions were similar to those in natural cases of the disease. With intravenous inoculation of a less virulent isolate there were abscesses in the subcutaneous tissues, muscle fascia and joint bursae.

Histophilus ovis infection in sheep in Western Victoria.

Organisms resembling Histophilus ovis were isolated from sheep in Western Victoria in association with synovitis, septicaemia and/or abscessation in 2 to 8 week old lambs. Histopathological lesions in these lambs were indicative of bacterial embolism with thrombosis. Similar organisms were also isolated from sheep in 2 flocks with a high neonatal mortality rate. These isolations were from vaginal swabs from the ewes, placentas and from one lamb which had meningitis, ependymitis, choroid plexitis, hepatic necrosis and focal myocarditis. The morphology, cultural characteristics and biochemical activity of the organisms are described and it is suggested that the organisms may be better classified in the genus Actinobacillus.