Sinusitis can be a challenging condition in horses, particularly when trying to identify the cause of the problem.
The biggest hurdle can be distinguishing between a primary sinusitis and those secondary to other disorders, such as a dental issue.
In general practice, horses with a nasal discharge from one nostril are usually treated with antibiotics over varying periods of time, often without a permanent end to clinical symptoms. This can make the healing process frustrating for the owner and treating veterinarian.
Researchers in Germany have investigated whether identifying the bacteria present can provide important clues to the root cause of the condition, thus helping to treat the problem.
Hauke Gergeleit and her colleagues said a combination of different imaging tools are sometimes needed to discover the underlying cause.
The study team noted that the bacterial flora of healthy and diseased paranasal sinuses (six paired sinuses, all interconnected) have been studied only sporadically in horses.
The researchers from the University of Veterinary Medicine Hannover Foundation in Germany set out to determine whether microbiological assessment of the secretions from the paranasal sinuses provided useful diagnostic information to distinguish between different causes of sinusitis.
The study, reported this week in the journal Acta Veterinaria Scandinavica, involved testing samples taken through an endoscope from 50 horses diagnosed with paranasal sinusitis, all with a history of one-sided nasal discharge. Samples were also taken from 10 healthy horses for comparison.
The samples were cultured in a lab to identify the bacteria.
Fourteen of the horses had primary sinusitis, 11 of whom revealed growth of Streptococcus equi ssp. zooepidemicus in their sample, with three samples yielding pure cultures.
Anaerobes (bacteria which do not need oxygen) were found in 15 out of 26 samples from horses with sinusitis linked to dental causes.
Healthy sinuses revealed mainly α-haemolytic streptococci and coagulase-negative staphylococci or showed no growth.
Enterobacteriaceae, a large family of Gram-negative bacteria, were found more often in secondary sinusitis.
There were significant differences in the bacterial composition and diversity between primary sinusitis, dental sinusitis and healthy controls, they said.
The study team concluded that microbiological examination of secretions from horses with sinusitis collected using an endoscope can help to distinguish between primary and dental sinusitis.
It was, they concluded, a feasible ancillary diagnostic tool, but does not replace a meticulous examination procedure, including diagnostic imaging.
Discussing their findings, the researchers said they managed to culture the bacteria in all cases of primary sinusitis and dental sinusitus.
The overall culture rate for healthy sinuses was 73.3%, with all positive cultures revealing a median of two bacterial species. None of these samples revealed obligate anaerobes and only five showed low to moderate numbers of Enterobacteriaceae. Coagulase-negative staphylococci and alpha-haemolytic streptococci were the genera most often isolated.
The frequent occurrence of obligate anaerobes (these are anaerobes harmed by the presence of oxygen) in cases of dental sinusitis was a significant difference to primary sinusitis cases, they said.
The full research team comprised Gergeleit, Jutta Verspohl, Judith Rohde, Karl Rohn, Bernhard Ohnesorge and Astrid Bienert-Zeit, all from the University of Veterinary Medicine Hannover Foundation.
A prospective study on the microbiological examination of secretions from the paranasal sinuses in horses in health and disease
Hauke Gergeleit, Jutta Verspohl, Judith Rohde, Karl Rohn, Bernhard Ohnesorge and Astrid Bienert-Zeit.
Acta Veterinaria Scandinavica 2018 60:43 https://doi.org/10.1186/s13028-018-0394-4