Three groups, each of five calves, four to seven months old, were inoculated intranasally with different numbers of Mycobacterium bovis. Infection was established readily in the calves which received an inoculum containing either 10(6) or 10(4) colony forming units (cfu). After every infection there was a lag period during which the organisms could not be isolated from specimens of nasal mucus. All the animals excreted M bovis and the time of commencement, quantity and duration of excretion appeared to be related to the inoculation dose. Excretion continued for many weeks, and for two calves excretion became intermittent over many months. All the calves which were given inocula of 92 cfu failed to develop the disease and no immunological responses were detected; however, M bovis was isolated from nasal secretions from one of these animals 100 days after inoculation.

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Summary Thirteen strains of pathogenic leptospires were isolated from 12 of 91 horses; seven strains belonged to the Australis serogroup (serotype bratislava) with three, two and one strains belonging to the Icterohaemorrhagiae, Hebdomadis (serotype hardjo) and Autumnalis serogroups respectively. Using leptospires isolated from horses and others representing the known parasitic Leptospira serogroups, a sample of 650 mares' sera was tested for agglutinating antibodies. Antibodies were found in 89.1 per cent of sera. The predominant reaction was to serotype bratislava, strain S/1334/79, isolated in this study, antibodies to which were detected in 81.8 per cent of sera. It is suggested that serotype bratislava may be adapted to, and maintained by, the horse population in Northern Ireland. Résumé On a isolé 13 souches de leptospiroses pathogènes sur 12 individus d'une population de 91 chevaux; sept souches appartenaient au sérogroupe Australis (serotype bratislava); trois souches appartenaient au sérogroupe Icterohaemorrhagiae, deux au sérogroupe Hebdomadis (sérotype hardjo) et un au sérogroupe Autumnalis. En utilisant des leptospires isolés sur des chevaux et d'autres représentant les sérogroupes connus de leptospires parasites, on a testé 650 juments et recherché des anticorps agglutinants. Des anticorps furent trouvés dans 89.1 pour cent des sérums. La réaction dominante fut celle avec le sérotype bratislava souche s/1334/79 isolée au cours de cette étude (81.8 pour cent des juments). On avance l'idée que le serotype bratislava peut s'être adaptéà la population équine d'Irlande du Nord et peut s'y maintenir. Zusammenfassung Dreizehn pathogene Leptospirenstämme wurden aus zwölf von 91 untersuchten Pferden isoliert. Sieben Stämme gehörten zur Australis‐Serogruppe (Serotyp Bratislava) — drei, zwei und ein Stamm zu Icterohaemorrhagiae, Hebdomadis (Serotyp Hardjo), beziehungsweise Autumnalis. Die Pferdeisolate und andere Repräsentanten der pathogenen Leptospiren‐Serogruppen wurden zur Untersuchung von 650 Stutenseren verwendet. Agglutinierende Antikörper konnten in 89.1 prozent der Seren festgestellt werden. Die häufigste Reaktion erfolgt gegen den Serotyp Bratislava S/1334/79, isoliert im Laufe dieser Arbeit) mit 81.8 prozent positiver Seren. Es wird vermutet, dass der Serotyp Bratislava sich in Nord‐Irland ans Pferd adaptiert hat und dass er über das Pferd erhalten bleibt.

Kidneys of cattle, mice and badgers were cultured for leptospires in an attempt to evaluate the relative importance of these species in the epidemiology of bovine leptospirosis caused by the Hebdomadis serogroup. Leptospires closely related to serotype hardjo were recovered from 57 (28.5 per cent) of 200 cattle examined but no evidence of infection was found in either badgers or mice, indicating that cattle act as the maintenance host for serotype hardjo. Many cattle were seronegative carriers.

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