Reeve-Johnson, L

English

The objective of this research was to investigate the relationship between ante mortem
assessments of disease severity and the gross pathological manifestations of disease
observed during necropsy. Many clinical assessments are subjective, the hypothesis
under investigation is that these correlate with the pathological state of the animal.

Bronchopneumonia due to Pasteurella haemolytica Al in calves, Actinobacillus
pleuropneumoniae infection in pigs, and Mycoplasma gallisepticum infection of
chickens were investigated. The diseases were induced by experimental infection and
animals were closely monitored. For calves and pigs, rectal temperature, respiratory
rates and clinical demeanour scores were recorded and at necropsy, the respiratory
tract and any other affected organs examined. For chickens, an auscultated respiratory
score was used, serological responses were recorded and, upon necropsy, inspection
of airsac lesions and mycoplasma isolation were performed.

Both graphical and statistical methods were used to correlate ante mortem measures of
disease severity with each other and with post mortem measures of gross pathological
lesions and bacteriological isolation of the infecting organism. Calves showed highly
correlated relationship between ante mortem and post mortem indicators of disease
severity. For pigs, the relationship between clinical variables and gross pathology was
much less clear and varied between the three serotypes of Actinobacillus
pleuropneumoniae used (serotypes 3,5a, 9). In chickens, there were few clinical
signs evident until the pathology compromised the physiological reserve capacity of
the airsacs. Beyond this `threshold', rapid increases in respiratory auscultation score,
mycoplasma isolation and serological response were all indicators of increasing gross
pathological changes.

The relationships between ante mortem assessments of disease severity and the gross
pathological lesions recorded at necropsy were usually non-linear and differed for
each pair of variables correlated. The strength of correlation between pairs of
variables also differed according to the stage of disease progression and severity of the
infective episode for each of the species studied. The relationships between clinical
variables being used as indicators of disease severity and the post mortem pathological
measures need to be clearly understood for each variable before conclusions
concerning the disease severity, prognosis or, in treated animals, efficacy predictions
can be made

Edinburgh Research Archive

The use of experimental infection models to investigate the correlation between clinical and pathological measures of the severity of respiratory disease in three species

https://era.ed.ac.uk/bitstream/1842/6943/1/514241.pdf

The use of experimental infection models to investigate the correlation between clinical and pathological measures of the severity of respiratory disease in three species

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