OAHN Companion Animal Research Project: Rabies titres in imported dogs

Project Lead: Scott Weese

Collaborators: Catherine Belanger, Katie Clow, Maureen Anderson

To view the full report, please download the PDF here: https://www.oahn.ca/wp-content/uploads/2023/04/OAHN-CA-Project-Summary-Rabies-Titres-FINAL-REPORT.pdf

To prevent the spread of canine rabies, several countries require rabies antibody titre testing, with a titre of ≥ 0.5 IU/mL as per the World Organization for Animal Health (1), prior to the importation of dogs. In Canada, a valid rabies vaccination certificate is required for importation of most dogs, but there is no requirement for titre testing. Several studies conducted in other countries have demonstrated that rabies antibody titres are highly variable even among dogs with current rabies vaccination certificates, and many dogs do not meet the recommended minimum threshold [2,3]. This raises many concerns, including the potential for falsification of rabies vaccination certificates and use of suboptimal vaccines. The objective of this study was to determine the rabies antibody titres in a convenience sample of dogs imported into Ontario, Canada between October 2021 and November 2022. Serum from 67 dogs was collected from imported dogs arriving through rescues and veterinary clinics from Egypt (46 dogs; 68.7%), China (9 dogs; 13.4%), the Bahamas (6 dogs; 9.0%), Antigua (2 dogs, 3.0%) and one each from Azerbaijan, India, South Korea, and Turkey. Samples were collected within a month of arrival, prior to any further rabies vaccination. Age of the imported dogs ranged from 3 months to 7 years and were split between male (52.2%) and female (43.3%), with the remainder unconfirmed (4.5%). The sampled dogs had been imported by six different rescues and one Humane Society. Serum samples were submitted to Kansas State Veterinary Diagnostic Laboratory and processed using the Rapid Fluorescent Foci Inhibition Test (RFFIT).

Overall, RFFIT titres ranged from 0.1 to 15 IU/mL. Almost half the dogs (32/67; 47.8%) had a titre less than 0.5 IU/mL. Twenty-three (23/67; 34.3%) dogs had no detectable rabies titre, despite all dogs having been imported within 1 month with a current rabies vaccination certificate.

Rabies antibody titres done prior to import were available for 29 dogs (29/67, 43.3%).  These titres were measured using an ELISA test performed at a laboratory in Egypt, and ranged from 0.5 – 3.00 IU/mL with a mean of 1.2 IU/mL. Almost half of these dogs (14/29, 48.3%), had an RFFIT titre that was greater than their pre-import titre. The other half (15/29, 51.7%) had an RFFIT titre that was at least 20% lower than their pre-import titre, and 11 of these 15 dogs had a titre below 0.5 IU/mL. Despite being required for importation, vaccination history was only available for 26 dogs (26/67; 38.8%). Of these dogs, twelve (12/26; 46.2%) had received a rabies vaccine that was approved for use in Canada. The median titre for dogs with an approved vaccine was 0.9 IU/ml with a range from 0.1 to 5.9 IU/ml.

This study demonstrates that rabies vaccination status may be suboptimal in many imported dogs. The reasons for this are unknown at this time and require additional research. There is no established protective rabies antibody titre for individual dogs and titre results do not impact the current legal requirement in Ontario for vaccination of all dogs over 3 months of age using a rabies vaccine product approved for use in Canada. Ontario veterinarians should review vaccination records of imported dogs and consider revaccination if there is any question regarding the adequacy of previous vaccinations for any reason.