Unmasking the microscopic occupants of dogs mouths
Niran Patel spent his early career investigating the cause of human acanthamoeba keratitis, a severe protozoal eye infection that if untreated can cause blindness. Protozoa are a class of single celled organisms that are more closely related to animal than bacterial cells, the most infamous being Plasmodium which causes Malaria.
Niran’s research interests ultimately brought him to study for a PhD at the WALTHAM Petcare Science Institute where he’s just published his first investigation of protozoa in dogs’ mouths*. “There is growing evidence of protozoan association with gum disease in humans. Research here first identified the bacteria associated with gum disease in cats & dogs mouths and importantly established that they are different to those in humans”. Niran was curious to know if the same was true for protozoa “Nobody knew if they were even present in dogs’ mouths”.
His biggest challenge was developing a fast and accurate system to identify different protozoan species. By comparing their DNA sequences he found unique regions for each species. He could then selectively amplify these regions from samples, meaning even if they were present at low levels, they could be identified. With a detection method in place veterinary dentist Lisa Milella, collected samples from 90 canine patients (Wey Referrals, Surrey) with either healthy gums or various levels of gum disease for comparison.
Two groups of protozoa Trichomonad and Entamoeba were found to be present in canine plaque. The Trichomonas were abundant during all stages of gum disease. Entamoeba were less prevalent and seen only in later disease stages. This was unexpected.
“I was surprised how similar these findings were to published research in human gum disease,” says Patel “We know that there are large differences in the bacterial populations seen in canine plaque so I expected the same for protozoa”.
To confirm these findings and ensure any less abundant species hadn’t been missed he used next generation DNA sequencing. Relative to traditional sequencing methods it enabled him to sequence and identify hundreds of thousands more individual protozoa per sample. Essentially amplifying the sensitivity of his screen over 100 000 times. This confirmed that both groups were associated with gum disease; compared with healthy teeth Trichomonad species were ten times more common in teeth with gum disease. The Entamoeba, which were rarely seen in healthy dogs, were over six hundred times more prevalent in severe disease.
The chances of a dog having gum disease at some point in its life vary but estimates are rarely below 70%. So what does this research mean if we’re to reduce gum disease in dogs?
“The key question is, are these protozoa causing disease or an effect of it?” says Patel. “Their association only tells us they are present at a given time but it doesn’t tell us why. So I’ve designed another approach. I’m going to screen a sample set designed to capture the microbial shifts as gums transition from health to very early reversible disease. That will conclusively tell us if their presence is important in driving the disease process as opposed to arriving late and taking advantage of the diseased environment.”