Babesia major in Britain: infectivity for cattle of cryopreserved parasites derived from Haemaphysalis punctata nymphs.

Babesia major-infected Haemaphysalis punctata nymphs, prefed for four days on rabbits, were ground in a modified Eagle's minimum essential medium containing N-2 hydroxyethylpiperazine-N1-ethane-sulphonic acid (HEPES) buffer using sterile sand or ground glass as triturating agents. The resultant supernatant fluids were shown to be infective for splenectomised calves. When attempts were made to cryopreserve the fluids using either dimethyl sulphoxide or glycerol to a final concentration of 10 per cent, only the former successfully maintained the intravenous infectivity of the organisms released by grinding with glass. A cooling rate of approximately 1 degrees C/min resulted in successful cryopreservation but a more rapid cooling rate did not.

Cell culture assay for toxigenic Pasteurella multocida from atrophic rhinitis of pigs.

A toxin produced by strains of Pasteurella multocida isolated from pigs with atrophic rhinitis caused a cytopathic effect in cell cultures derived from embryonic bovine lung. The toxin was produced during the late logarithmic phase of bacterial growth and inactivated by heating for 30 minutes at 56 degrees C. The cell culture assay was reproducible and 10(3) to 10(4) times more sensitive than a lethal assay in BALB/c mice. There was complete agreement between results in the two tests with 76 isolates of P multocida. Neutralising activity was demonstrated in both assays with sera from infected gnotobiotic piglets. It was concluded that embryonic bovine lung cell cultures provided a sensitive in vitro test for the differentiation of toxigenic from non toxigenic isolates of P multocida. The assay could be used in diagnostic laboratories and for characterisation of the toxin.

Isolation of viruses from cultures of bovine endometrial cells.

Endometrial cells from the uteri of pregnant and nonpregnant cattle were cultured. The presence of one or both of two viruses, noncytopathic mucosal disease virus and bovine syncytial virus, was demonstrated in seven of 19 endometria investigated. It was necessary to subculture the cells an average of four times to detect the viral infections. Difficulties were encountered in producing endometrial cell cultures from cows at term or near the end of term and also from older animals. The infections detected may be significant because both of the viruses isolated are capable of infecting the bovine fetus in utero and mucosal disease virus has been associated with bovine fetal diseases.

Antibacterial activity in colostrum and milk associated with protection of piglets against enteric disease caused by K88-positive Escherichia coli.

Piglets suckled by dams that had been vaccinated with K88 antigen were significantly more resistant to deaths caused by neonatal diarrhea after challenge with a large dose of a K88-positive enteropathogenic strain of Escherichia coli than piglets suckled by control dams. The factors most likely to be involved in protection of the piglets were investigated by comparing the antibacterial activities of serum and mammary secretions from the two groups of dams. Vaccination stimulated the production of K88 antibodies, which were associated with anti-adhesive activity directed against the adhesive properties of the K88 antigen, and of O8 antibodies; the latter antibodies were attributed to traces of O8 antigen in the vaccine. Neutralizing activity against heat-labile enterotoxin was present in several dams before vaccination but was not stimulated by bacteriostatic activities were similar in serum and mammary secretions from both groups of dams and appeared to play no significant role in the protective after parturition were atrributed to exposure of the dams to the challenge strain excreted by the piglets. It was concluded that neutralization of the adhesive properties of K88 antigen by K88 antibodies in colostrum and in milk contributed significantly to the protection of piglets from vaccinated dams. However, the contribution of antibacterial activities associated with the greater levels of O8 antibodies in colstrum from the vaccinated group cannot be entirely excluded.

A survey of virus infections of the respiratory tract of cattle and their association with disease.

A total of 1590 caves were investigated between May 1972 and December 1975. Twenty-two per cent were treated for respiratory disease and 2 . 5% died of pneumonia. Almost 80% of the respiratory illness occurred in six sharp outbreaks. Samples of virology were collected routinely from 127 healthy calves and from 354 calves treated for respiratory signs and comprised 1143 nasopharyngeal swabs and 1069 sera. Virus infections were detected on 540 occasions including 135 by parainfluenzavirus type 3 (Pi-3), 78 by respiratory syncytial virus (RSV), 103 by rhinovirus, 49 by bovine virus diarrhoea virus (BVDV), 29 by adenoviruses, 53 by reoviruses and 88 by enteroviruses. The seasonal and age distribution of infections differed between viruses. Only infections by RSV, Pi-3 and BVDV were significantly associated with disease.