Experimental infection of four horses with Ehrlichia phagocytophila.

The study experimented on four healthy horses to see how they would respond to infection with Ehrlichia phagocytophila, a bacteria causing bovine ehrlichiosis. Although the bacteria caused no visible side effects or illness in these horses, serological analysis showed they had developed antibodies against the bacteria, indicating an immune response.

Methodology

• The study began by selecting four horses that had no prior exposure to the bacteria Ehrlichia phagocytophila, which causes bovine ehrlichiosis, a condition transmitted by ticks to cattle.
• These horses were then exposed to the bacteria, which was contained in bovine leucocytes (a type of white blood cell) and injected into the horses intravenously.

Clinical, Haematological and Biochemical Examination

• The horses were examined daily for a period of four weeks. These daily physical checks were designed to identify any outward signs of illness resulting from the infection.
• Blood samples were also taken daily for testing. These tests included cytological, haematological and biochemical examinations to detect changes at cellular level and in the horse’s body chemistry that might not be visible from outward signs.

Polymerase Chain Reaction (PCR) Testing

• Daily samples were also tested using a nested PCR. This is a more sensitive version of regular PCR and was used to amplify and detect the DNA of the infecting bacteria from even tiny quantities.
• All PCR results came back negative, indicating that the bacteria were not present in the horses’ blood in detectable quantities.

Indirect Immunofluorescence Test

• This test was used to establish when the horses’ immune systems began to react to the bacteria (seroconversion) and how long they retained the antibodies against the bacteria.
• All horses developed reciprocal titers up to 1280 against Ehrlichia phagocytophila, and these remained for up to five months, indicating a sustained immune response in the absence of apparent illness.

In conclusion, while the horses didn’t develop any clinical signs of illness, their bodies did mount an immune response towards the bacteria. This can have significant value in understanding disease progression and immune response in not just horses but other animals as well.