Study explores EPEC and parvoviral enteritis
August 04th, 2012
By Robyn Thrasher
When a puppy comes into a veterinary clinic with clinical signs of vomiting and diarrhea, one of the top diagnoses on a veterinarian’s mind is parvoviral enteritis – a viral infection affecting the gastrointestinal tract.
But what about other pathogens that may look like parvoviral enteritis?
One such infectious agent is the bacteria known as enteropathogenic Escherichia coli (EPEC), which appears to be clinically indistinguishable from parvovirus infection.
Recently, a couple of canine patients presented to the WCVM’s Veterinary Medical Centre (VMC) with suspicions of parvovirus infection although no parvovirus was detected. What’s interesting is that clinicians eventually discovered a large number of EPEC were seen on the dogs’ fecal culture.
This incident triggered WCVM professor Dr. Anthony Carr to launch an investigation into EPEC and its role in gastrointestinal disease.
“We’re interested in this organism for two reasons,” says Carr, a specialist in small animal internal medicine.
“First, it has the capability of looking just like parvoviral enteritis. Secondly, we generally have very good success with treating parvovirus. Over 90 per cent recover with aggressive therapy, but at times, we have some very poor outcomes. We’re wondering if concurrent infection with EPEC might be causing these poorer outcomes.”
There are a number of different strains of E. coli, but EPEC can be differentiated from other E. coli by the presence of the eae gene.
“The eae gene encodes an attachment protein that allows these organisms to attach to the intestinal lining. That results in damage to the microvilli – the absorptive surface of the intestine,” explains Dr. Joseph Rubin, a postdoctoral fellow in the WCVM’s Department of Veterinary Microbiology and one of the study’s lead investigators.
Interested in looking at “old diseases” in a new way, Rubin believes that some people may think there’s nothing left to learn about parvoviral enteritis.
“What we’ve seen recently at the VMC is that some of the sickest parvovirus-infected dogs also seem to be infected with EPEC, suggesting that there’s something more going on than we usually consider.”
Although EPEC can be found in the feces of healthy dogs, Rubin points out that what’s normal for one animal isn’t necessarily normal for another.
“Many organisms that animals carry, including EPEC, have the potential to cause disease in the right situation.”
As well, EPEC is known to be zoonotic, meaning infection can spread between animals and people.
“EPEC infections most commonly occur in infants,” says Rubin. “Because small children don’t understand the importance of hand washing and often explore their environment by putting things in their mouth, the zoonotic risks of EPEC may be underappreciated.”
Oral contact with fecal material is the likely route of transmission for newly infected or colonized dogs, but it’s unknown what tips the balance from healthy colonization to clinical disease. The study’s research team predicts that infection with parvovirus may play a role.
The project, which began in June 2012, involves the collection of feces from 100 dogs less than two years of age that present to the VMC with signs of parvoviral infection. Dr. Casey Gaunt, another WCVM small animal internal medicine specialist, will identify suspected cases of parvovirus and co-ordinate the collection of samples.
Once the dogs are admitted to the VMC, clinicians will collect a fecal sample for bacterial culture and a parvovirus test. Due to inconsistent shedding of the virus, dogs that test negative for parvovirus will be retested when they’re discharged from the medical centre.
To rule out other common causes of diarrhea, all dogs will be tested for Giardia and Cryptosporidium – protozoal parasites that infect the gastrointestinal tract.
Rubin will test any E. coli isolated from the fecal cultures for the eae gene using a polymerase chain reaction (PCR) test developed in collaboration with Dr. Janet Hill, a WCVM associate professor in veterinary microbiology.
Hill’s research associate, Dr. Bonnie Chaban, is also currently developing a diagnostic assay that will include EPEC.
Medical records for patients with and without EPEC will be assessed for differences in survival, duration of hospitalization and cost of treatment.
Information regarding prevalence of EPEC in dogs, cats and people is very limited. Carr hopes to address that lack of knowledge with this project that’s supported by the veterinary college’s Companion Animal Health Fund (CAHF).
“Identification of eae positive E. coli (EPEC) in patients diagnosed with parvoviral enteritis will allow the formulation of specific treatment protocols that may shorten hospital stays and reduce the cost of care,” he says.
He adds that the correlation of EPEC infection with survival in affected dogs may serve as a prognostic indicator that will help veterinarians and pet owners make better informed decisions about patient care.
“The study will also raise awareness among veterinarians that any dog showing the classical signs of parvovirus may not necessarily be infected with parvovirus,” says Carr. “You have to consider other possible causes.”
Robyn Thrasher of Edmonton, Alta., is a third-year veterinary student at the WCVM. Robyn is a WCVM research communications intern as well as a summer student in the WCVM Veterinary Medical Centre during the summer of 2012.