Island medical health officer explains why the rabies test was wrong and the response was right<\/p>\n
After a free-roaming kitten in Chemainus initially tested positive for rabies last month, Island Health issued a public alert, identified possible exposures and advised several individuals to undergo rabies post-exposure prophylaxis (PEP). Weeks later, the agency announced the test result was a rare false positive and that the kitten did not have rabies after all.<\/p>\n
The reversal left some residents confused and concerned: how could a sick animal test positive, then negative? Why was such an aggressive response warranted? And what exactly made the kitten so ill?<\/p>\n
To clarify what happened and why, the Courier spoke with Dr. Charmaine Enns, medical health officer for North Island and the Alberni West Coast. Enns walked through the timeline, testing process and rationale for the public health response while emphasizing that this case, although unsettling, is ultimately evidence that the system works as it should.<\/p>\n
\u201cAll is well in the world as we understand rabies and rabies risk and transmission in British Columbia,\u201d Enns said. \u201cThis is a good news story.\u201d<\/p>\n
The kitten was one of several feral animals rescued from a wooded area near the 8000 block of Chemainus Road in early July. While in the care of a rescue organization, one kitten began showing neurological symptoms. A veterinarian made the clinical decision to euthanize the animal and test for rabies.<\/p>\n
The initial test was conducted at the Canadian Food Inspection Agency\u2019s (CFIA) rabies lab in Lethbridge, Alta., using a fluorescent antibody (FA) test. The test detects the presence of rabies antigens in brain tissue by observing fluorescence.<\/p>\n
\u201cThe technician who looked at the test saw something fluoresce and reported a positive test,\u201d Enns said. \u201cThat\u2019s a very well-proven, very important test that very skilled people from CFIA do all the time.\u201d<\/p>\n
Because rabies is a fatal illness with no treatment once symptoms begin, even a suspected case triggers a full response from public health.<\/p>\n
\u201cNow we have a positive test, we have people who are exposed, we need to do our due diligence and offer you rabies post-exposure prophylaxis,\u201d Enns said.<\/p>\n
Approximately 20 individuals \u2014 mostly rescue and veterinary staff \u2014 were offered a four-dose rabies vaccine series. For those with potential bite or saliva exposure, the vaccine was accompanied by a one-time dose of rabies immune globulin, which provides passive protection while the vaccine takes effect.<\/p>\n
\u201cNo one refused rabies post-exposure prophylaxis who it was recommended to or offered,\u201d said Enns.\u00a0<\/p>\n
She acknowledged that the treatment can cause side effects for some recipients.<\/p>\n
\u201cYou might feel it at the injection site or feel off, but there\u2019s no anaphylactic reactions I\u2019ve heard of,\u201d she said. \u201cThere is no contraindication to rabies vaccine if you’ve had an exposure that warrants it, because no reaction is as bad as getting rabies.\u201d<\/p>\n
In the weeks following the initial result, CFIA conducted extensive follow-up testing to confirm the rabies strain and determine its origin. Enns said this deeper analysis is standard when a non-bat species tests positive.<\/p>\n
\u201cThey did weeks of testing to ensure accuracy,\u201d she said. \u201cAll of the subsequent tests were not able to identify the virus. There was no rabies virus detected so this kitten did not have rabies.\u201d<\/p>\n
She said this type of error is exceptionally rare.<\/p>\n
\u201cIn the last 20 years, we\u2019ve only had three false positives in all of Canada,\u201d she said. \u201cI\u2019ve been a medical health officer for 22 years. I\u2019ll never see this again in my career.\u201d<\/p>\n
The 2007 case of a domestic cat dying from rabies in B.C. was the last confirmed incident of its kind. That was linked to a rabid bat that had flown into a home.\u00a0<\/p>\n
Enns emphasized that bats remain the sole known vector of rabies in the province.<\/p>\n
\u201cIn B.C., the only species that’s a concern for transmission of rabies are bats,\u201d she said. \u201cSince the 1960s, we’ve had only seven non-bat animals test positive for rabies, and they all had bat variant rabies.\u201d<\/p>\n
Enns explained that the rabies virus only travels through nerves, not through the lymphatic or blood systems.<\/p>\n
Transmission of bat variant rabies from one species to a second and then a third, such as from bat to cat to human, is \u201calmost unheard of,\u201d she said.<\/p>\n
\u201cThere have been literally fewer than five cases globally where that has happened,\u201d Enns said. \u201cIn our context, in British Columbia, it just basically doesn\u2019t happen.\u201d<\/p>\n
Still, she said, the decision to offer prophylaxis was based on the evidence at hand and the severity of untreated rabies.<\/p>\n
\u201cWith rabies, because there is no treatment and it’s invariably fatal if you’re infected, it\u2019s risk versus benefit,\u201d she said.\u00a0<\/p>\n
She hopes the public sees the incident as a sign of accountability and transparency.<\/p>\n
\u201cWe made decisions based on the first test results,\u201d said Enns. \u201cAnd when exhaustive testing confirmed it was a false positive, we told the public. That\u2019s the system working.\u201d<\/p>\n