The Bacteriology and Vaccine Therapy of Distemper in Horses.

This research article focuses on the study of distemper, also known as influenza or shipping fever, in horses, specifically focusing on its bacteriology and potential vaccine therapies. The research was conducted during an epidemic of the disease among the horses of Squadron C of the National Guard of the State of New York, in 1910.

Context and Methodology of the Research

• This study was conducted in response to an outbreak of influenza or distemper among horses of the National Guard of the State of New York. The disease showed symptoms such as elevated temperature, marked weakness, constipation, partial or complete loss of appetite, and extreme depression.
• In an attempt to study the bacteriology of the disease, the researchers autopsied a number of dead mice found in the stable, with the suspicion that they might be a factor in the spread of the epidemic.
• The researchers extracted blood from the jugular vein of the horses and inoculated it onto various media for analysis. Later, a horse died, and an autopsy was conducted to examine the organ changes caused by influenza.

Findings from Bacteriological Examination

• Through the bacteriological examination of the intracardiac blood, lungs, liver, spleen, kidneys, and cerebrospinal fluid, the research discovered two types of bacteria: a Gram-negative bacillus and a Gram-positive, encapsulated, lancet-shaped diplococcus. These bacteria were cultivated on various media and observed for growth and morphology.
• Two distinct types of bacterial colonies were identified from the cultures. One was small, round, moist, and granular, which upon further testing, turned out to be a typical pneumococcus. The other colony was much larger and comprised of plump bacilli that were motile and stained Gram-negative. This colony showed no spore formation.
• The large colony was noticed to lose its mucoid appearance and turn smaller in size during successive sub-cultivation. However, in a sugar medium with high moisture, the original colony appearance reemerged to a certain extent. This colony was also found to produce no indol on Dunham’s peptone.

Findings from Agglutination Reactions

• The large colony bacteria did not show any agglutination reactions when tested against typhoid serum. However, agglutination reactions did occur both with the serum of sick horses and those that had recovered from the disease. This agglutination persisted even six months after recovery at a dilution of 1 to 200.

Findings from Pathogenicity Testing

• The large colony bacteria was found to be pathogenic for several species including mice, rats, rabbits, and guinea pigs. Autopsy of these animals displayed marked degeneration of all the viscera, and the same organism was isolated. However, it was noted that the colony bacteria were not pathogenic for dogs.

Based on the findings of this research, there is a strong indication that distemper in horses is caused by a bacterial infection that can also affect several other species. The positive agglutination reactions in recovered horses suggest potential for the development of a vaccine therapy for the disease.