Identification of Bartonella henselae in an aborted equine fetus.

This research study identified the presence of Bartonella henselae, a bacterium, in a miscarried horse fetus, suggesting a probable cause of equine abortion.

Summary of findings

• The research focused on characterizing a case of Bartonella henselae, a bacterium usually associated with diseases in humans and other animals, present in an aborted horse fetus. The methods of investigation involved examining the fetus’ tissue in various ways such as visually (gross), under a microscope (histologic), with dye staining (immunohistochemical), at the molecular level (ultrastructural), and via DNA analysis (molecular methods).
• This bacterium has been documented in multiple mammalian species but only recently in horses (equids). Nevertheless, there wasn’t any proven link between this bacterium and abortion in horses.

Detailed examination of the fetus

• The fetus displayed evidence of tissue death (necrosis) and inflammation of the blood vessels (vasculitis) across various tissues. Within these damaged areas, bacteria that appeared as short rods to a spiral-shaped (Gram-negative short-to-spirillar) were found. These signs suggested a bacterial infection.

Molecular analysis

• Nucleotide sequence analysis, a process for identifying the order of nucleotides in DNA, of the bacterial 16S rRNA gene, a portion frequently used for bacterial identification, showed a 99.9% match with the gene of B. henselae, confirming the organism’s presence.
• The presence of B. henselae was also verified by polymerase chain reaction (PCR) amplification, a technique for making numerous copies of a specific DNA segment, and sequencing analysis of other species-specific Bartonella genes. This method further substantiates the initial identification.

Immunohistochemical and ultrastructural characterization

• The bacteria stained positively with a monoclonal antibody specific for B. henselae during an immunohistochemical examination. This means that the bacteria in the tissue was recognized and bound by the antibody, once again confirming the identification.
• Ultrastructural characterization, a method for observing the structure and features at a very detailed level, was done to provide further confirmation.

Conclusion

• Efforts to detect other known causes of equine abortion were not successful, ruling out alternative reasons for the miscarriage.
• The severe inflammation of the blood vessels and presence of bacteria within these inflamed tissues led the researchers to conclude that the infection by B. henselae was responsible for the abortion of the horse fetus.