A new research study at the Western College of Veterinary Medicine is investigating the prevalence of Chlamydia psittaci (C. psittaci) in aborted horse placentas.
Led by veterinarian Dr. Madison Ricard and her graduate supervisor at WCVM, veterinary pathologist Dr. Bruce Wobeser, the research is trying to see whether chlamydia is causing abortions among the horse population in Western Canada.
What causes equine abortions?
Currently, a large percentage of equine abortions in Canada have unknown causes. Ricard wants to eliminate that mystery and find out what the cause, or causes, might be.
Ricard says they started looking into chlamydia after hearing about a 2014 case in Australia. “A pregnant mare at a vet school had aborted and the people who handled her placental tissues became very sick,” Ricard says. An Australian research team looked at the placental tissues and confirmed it was Chlamydia psittaci, and that the veterinary students and technicians who were in contact with aborted tissues had contracted the infection.
Chlamydia psittaci is zoonotic, an infectious disease often carried by birds, with nearly 500 avian species known to be susceptible to infection that can be transmitted from animals to humans (or vice versa). After hearing about the case in Australia, Ricard was “curious to see if the same thing was happening here in Canada.
“The only other study about this topic in North America came out in 1985,” Ricard says. “Obviously, there’s a lot of room for things to have changed.”
Ricard and Wobeser tested 100 placenta tissue samples that had been submitted to the provincial veterinary diagnostic laboratory in Saskatchewan, Prairie Diagnostic Services, between 2009 and 2020. They found that 26 per cent of the samples tested positive for chlamydia, with 22 per cent testing positive for Chlamydia abortus, which Ricard says is “not the same as what was detected in Australia but very similar, potentially also zoonotic.
“We weren’t expecting to find that many,” Ricard says. “We expected to find zero.”
Ricard is hoping to do some further research this summer, including looking at normal placenta tissues. “We don’t know if chlamydia is truly causing abortion in these horses, or if we’re just randomly finding it,” Ricard says, “But if we don’t find it in normal placentas, it’s much more likely that it’s truly causing equine abortions.”
Potential dangers to humans
Chlamydia psittaci, which has been detected in Australia but not in Canada, can cause complications including pneumonia, endocarditis (inflammation of the heart valves), hepatitis, and inflammation of the nerves of brain, leading to neurologic problems.
Chlamydia abortus, which Ricard and Wobeser detected in their study in Canada, is familiar to those in the sheep industry, where Ricard says it’s been well known for causing a lot of illness in people, and has caused human abortions.
Chlamydia abortus is a cause of abortion and fetal loss in sheep, and human infections can follow the inhalation of infected material (such as diseased placenta, uterine discharges and feces) from livestock. There is a considerable risk for humans who have contact with aborting sheep, sheep at risk of abortion, dead lambs and placenta. Pregnant women are particularly at risk, as contracting the infection can result in spontaneous abortion, stillbirths or premature labour.
Implications for horse breeders, veterinarians and vet techs
According to WCVM Today, horses are the only routinely examined species for which veterinarians and registered veterinary technologists don’t put on personal protective equipment before handling aborted tissues. This new research might change that.
While they don’t know yet if the amount of bacteria present is enough to cause sickness, Ricard says that “the main thing for anybody handling a placenta or any aborted tissues from mares is that Chlamydia abortus is potentially zootonic.”
“At the time, we’re not recommending any crazy biosecurity changes,” Ricard says. “But if you’re a pregnant woman handling tissues, we’d advise gloving, masking.”