Balantoides coli is an intestinal parasite common in pigs

The other day, I was looking at tissues from a pig under the microscope when I came across several unexpected parasites.

These round little creatures were within the lining of the colon, causing mild inflammation but otherwise minding their own business.

At about 50 micrometres across, they disrupt the normal repeating pattern of small circles that are the main feature in this part of the body.

Their outer surface is covered by a fringe of small hair-like structures, as you can see in the photo. These allow it to swim. Truly, they look like wee one-eyed, microscopic monsters.

My diagnosis was a parasite called Balantoides coli.

It is classified as a protozoan (prot-o-zoo-an), which are sometimes referred to as one-celled animals.

In the big fermentation vats that make up part of the stomach system in cattle, little creatures like this are common and help break down plants into absorbable components.

However, when they get into the large intestine of pigs, the results are very different.

Most pigs have the parasite with no associated disease. However, it can act as what we call an opportunistic pathogen, meaning it takes advantage of some change in the animal to cause disease.

Some pigs, including those with other infections, nutritional imbalances or overcrowded pens, can develop diarrhea.

Pregnant or lactating sows are also commonly infected by this parasite, and they are a source of infection for piglets.

Although not well understood, it is possible infections with this parasite also lead to more subtle effects, such as poor growth and decreased welfare.

For instance, a recent study on the microbiome of infected pigs showed that pigs with the parasite have altered gut bacterial communities.

When pigs had the parasite, they also tended to have more disease-causing bacteria strains, such as Campylobacter and E. coli, compared to those that were not infected.

The parasite develops cysts, which are passed in the feces, contaminate the environment and can be a source of infections for the next pig to come into that pen.

Infected pigs can be identified through laboratory testing. Beyond seeing the parasite in tissues, like I did, they can be found in feces from live pigs, and new molecular tests have improved detection.

The parasite is present worldwide, including Europe, where intensive pig production and high biosecurity is similar to Canada.

A recent study out of Norway, where they practice high biosecurity production, 70 per cent of pigs tested had this parasite.

The study also identified that older pigs were the most likely to be infected, which reflects increasing exposure with age.

It is unknown what percentage of pigs and farms in Canada have this parasite.

Pigs are the main animals to be infected, but it can also spread to other species, such as horses, sheep, cattle, camels and even guinea pigs.

Wild boar also carry this parasite in their intestines.

It is zoonotic, meaning it can spread from animals to people.

Infections in people occur through consumption of food or water that is contaminated with fecal matter.

While most people with this infection have no symptoms, it can cause diarrhea and stomach pains. Severe, untreated infections can lead to bowel rupture.

Infections are more common in developing countries where water sanitation is inadequate and where pigs are raised.

People who have frequent contact with pigs are at higher risk of infection, including farmers and those who work in slaughter facilities.

Because the parasite creates resistant cysts that can survive in the environment, it is challenging to control. Even high health herds in developed countries have a high prevalence of infection, despite intensive production and robust biosecurity practices.

Avoiding overcrowding while maintaining clean pens are the best options to reduce the impacts of this parasite.