Bovine leptospirosis: Field and experimental studies

Ellis, William Armstrong (1975) Bovine leptospirosis: Field and experimental studies. PhD thesis, University of Glasgow.

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Bovine leptospirosis is the infection of cattle by any serotype belonging to the genus Leptospira. It has now been reported from almost every part of the world and infections by strains belonging to the pomona, grippotyphosa, icterohaemorrhagiae and hebdomadis serogroups are of world wide significance. A variety of clinical signs such as haemoglobinuria, jaundice, mastitis and abortion have been associated with infection. Very little is known about the serotypes of Leptospira which may infect cattle in the United Kingdom. The purpose of the study described here was to carry out investigations into bovine leptospirosis in Scotland. The work consisted of two parts, firstly, a field study and secondly, an experimental study. The field study consisted of: (a) a serological survey of 3,600 cattle. This was carried out using the microscopic agglutination test incorporating antigens representing sixteen Leptospira serogroups on sera from "cast" cows, cows which had aborted and cows in 29 herds. In this way the serogroups which infect cattle were identified and their relative importance was assessed; (b) an attempt to correlate the serological findings with the clinical findings in the 29 herds by means of an epizootiological model and on a farm where an outbreak of icterohaemorrhagiae infection occurred in calves; (c) attempts to isolate leptospires from the kidneys of cows with serological evidence of infection; (d) attempts to demonstrate leptospires in aborted foetuses. Antibodies to serotypes representing one or more of ten Leptospira serogroups were detected in the sera of 1,766 (49.1 per cent) cattle. Antibodies to sejroe (hebdomadis serogroup) were found in 1,503 (41.8 per cent) sera; to icterohaemorrhagiae in 278 (7.7 per cent) sera; to ballum in 264 (7.3 per cent) sera. Antibodies to bratislava (australis serogroup), javanica, conicola, panama, cynopteri, pyrogenes and autumnalis were detected in a small number of animals. There was no evidence for pomona and grippotyphosa infections. It was concluded that infection with strains (probably serotype hardjo) belonging to the hebdomadis serogroup in susceptible pregnant cattle could result in abortion. This conclusion was based on; 1) Reports by farmers and practising veterinary surgeons of abortions of unknown aetiology in herds showing serological evidence of infection. 2) The occurrence of a much higher incidence of antibody titres of 1:300 or greater to sejroe (33-7 per cent) in cows from herds with a history of undiagnosed abortion, than in cows from other groups of animals tested. 3) The close relationship found between the incidence of cows with antibody titres of 1:10 or more and 1:300 or more to sejroe and the incidence of abortion of unknown aetiology in 29 herds over the 18 month model period. This conclusion was supported by the demonstration, for the first time, of leptospires belonging to the hebdomadis serogroup in the internal organs of two aborted foetuses and a premature live calf. The incidence of abortion in infected herds varied between 0 and 14 per cent per 9 month period and showed a marked seasonal variation. Abortions were more common in the months from October to March than in the remaining months. The results of the field survey suggested that Scottish cattle act as maintaining hosts for strains belonging to the hebdomadis serogroup whereas infections by other serogroups were incidental events resulting from the contamination of their environment by other maintaining hosts. Of the other serogroups infecting cattle only icterohaemorrhagiae was obviously associated with clinical disease. Icterohaemorrhagiae infection was diagnosed in calves on one farm and was associated with marked jaundice in one calf and stunted growth in two treated, in-contact calves. (Abstract shortened by ProQuest.).

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: S W Michna
Keywords: Animal diseases
Date of Award: 1975
Depositing User: Enlighten Team
Unique ID: glathesis:1975-72656
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 11 Jun 2019 11:06
Last Modified: 11 Jun 2019 11:06

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