Clinical observations on bovine parasitic otitis in Tanzania.

Between January 1982 and December 1989 more than 5,000 clinical cases of bovine parasitic otitis were examined. Clinical signs were mild in early cases and were characterised by dullness, anorexia and occasional head shaking, but were severe in long standing cases where the major presenting clinical signs were dark brown aural discharges which soiled the hair below and in front of the ear, emaciation, central nervous signs, recumbency and death.

Distribution of Pasteurella haemolytica in the respiratory tracts of carrier calves and those subsequently infected experimentally with Dictyocaulus viviparus.

Distribution of Pasteurella haemolytica in the respiratory tracts of calves with no apparent clinical signs of illness and those infected experimentally with Dictyocaulus viviparus was determined so as to define carrier sites for this organism. The calves had been positive by nasopharyngeal swab for either P haemolytica A2 or A1 for at least two months or for over a month, respectively, before slaughter. P haemolytica A1 was acquired following horizontal spread from other infected calves. It was observed post mortem that P haemolytica A1 or A2 resided in the tonsils and retropharyngeal lymph nodes of calves of both groups. In addition to these sites, P haemolytica A1 was also isolated from the right cranial lung lobe of one of the calves from the D viviparus infected group although there was no evidence of pasteurella associated pneumonia. It was concluded that tonsil and retropharyngeal lymph nodes appear to be the most important carrier sites for P haemolytica when compared to other tissues of the bovine respiratory tract.

Comparing different isolates of Pasteurella haemolytica from beef calves using their in vitro antimicrobial sensitivity patterns.

In vitro studies, using disc diffusion and agar dilution techniques, were carried out to compare susceptibilities to selected antimicrobial agents of 30 isolates of Pasteurella haemolytica from healthy calves and 30 isolates from calves with transit fever. There was no difference in susceptibility patterns between isolates from healthy calves and isolates from diseased calves or between isolates of serotype A1 and isolates of serotype A2. Penicillin resistance was associated with production of beta-lactamase.

Experimental bovine pneumonic pasteurellosis: a review.

Whenever a 'new' disease is discovered and the putative agent responsible is isolated, it has been customary to attempt to reproduce the disease in similar animals under controlled experimental conditions. If an identical syndrome is produced, then the agent is considered to be responsible for producing the field disease. As early as 1892, Nocard did just that in relation to bovine pneumonic pasteurellosis (shipping/transit fever). His work however, appears to have escaped the attention of many subsequent workers. In the 1930s many workers attempted to reproduce the disease with crude preparations obtained from either sick or dead animals, but most of them failed. After 1950 several agents (bovine herpes virus 1 [BHV1], parainfluenza-3 virus [PI3] and mycoplasmas) were isolated from cases of shipping fever in North America. These, together with physical stress, were thought to be involved in the aetiology and pathogenesis of the disease, with pasteurellae playing the role of secondary invader. Many experimenters then used multiple agents in different combinations, but their degree of success in reproducing the disease was variable. Greater success was achieved when P haemolytica A1 was given to calves four days after exposure to BHV1. This success, although only moderate, reinforced the concept of the secondary role of pasteurellae. After 1977 however, it became increasingly clear that P haemolytica A1 was capable of causing the disease as a primary pathogen, provided that two conditions were fulfilled. First, the calves had to be susceptible, that is, non-immune, and secondly, P haemolytica A1 in the logarithmic growth phase had to be administered to the trachea or lungs in numbers greater than 5 x 10(9) colony forming units.

Changes in serum pepsinogen and haemoglobin concentrations in calves infected with Haemonchus contortus.

In four calves given Haemonchus contortus larvae, the serum pepsinogen concentration rose quickly to reach a mean of 3.5 iu tyrosine on day 14 after infection. The mean concentration dropped to 1.8 iu tyrosine by day 23 and remained around 2.0 iu tyrosine until an anthelmintic was given on day 57, when concentrations returned to preinfection values.