Experimental Brucella abortus infection in the horse: observations during the three months following inoculation.

This study observed the effects of Brucella abortus infection in horses over a three-month period. It found that infection could lead to intermittent bacteraemia in mares and the development of antibodies, while not causing substantial changes in biochemical or haematological values.

Research Methodology

• The researchers infected five mares, a stallion, and a colt foal with Brucella abortus strain 544 through an intraconjunctival inoculation method.
• They noted the physiological reactions such as clinical signs of disease and temperature changes.

Observations

• No significant clinical signs of disease were observed except for mild fever.
• Intermittent bacteraemia was found in the mares but not in the other horses.
• The horses began to develop antibodies against B. abortus from the second week following inoculation. The titres in the serum agglutination and complement fixation tests began to decline significantly after six to eight weeks.

Haematological and Biochemical Changes

• Despite the infection, there were no consistent changes in either haematological or biochemical values.
• However, reactions to Coombs antiglobulin, 2-mercaptoethanol, and immunodiffusion tests were maintained throughout the experiment.

Post-Mortem Examination

• Upon eventual death, the researchers performed a post-mortem examination on the foal.
• They found granulomatous lesions in the lungs, liver, testes, and metatarsophalangeal synovial membranes.
• B. abortus strain 544 identical to the one used for inoculation was recovered from lymphoid and other tissues. This confirms that the organism successfully established an infection in the inoculated horses.

Based on the study, it was made clear that Brucella abortus could indeed cause infection in horses without triggering severe clinical signs. Furthermore, the pattern of antibody response and the presence of the bacterium in lymphoid and other tissues show persistence of the bacterium after the initial infection.