Factors Associated With Unsuccessful Rabies Tests in Utah, 2014-2023.

Abstract

Context: Testing potentially rabid animals is crucial for providing accurate recommendations to prevent rabies infection. When a test of the animal is unsuccessful, (ie, does not produce a positive or negative result) after a potential exposure, health officials cannot rule out rabies and must recommend rabies postexposure prophylaxis, presenting an economic burden to patients and health care systems.

Objectives: To better understand factors associated with unsuccessful rabies tests to inform interventions that would reduce preventable unsuccessful testing.

Design: We performed tests of independence between unsuccessful test rates and frequently submitted animal and submitter types. We used Cochran-Mantel-Haenszel (CMH) tests to assess the significance of the association between unsuccessful tests and animal type and submitter type, while controlling for the effects of each. Stratified bivariate analyses identified specific factors driving significant CMH results.

Results: Of 2 806 specimens submitted for rabies testing during January 2014-March 2023, 113 (4%) were unsuccessful. Bats, raccoons, and skunks each had higher unsuccessful test rates compared to dogs or cats (Ps < .001-.003) and together comprised 87 (77%) of the 113 unsuccessful tests. Submissions by citizens had a higher proportion of unsuccessful tests than submissions by animal control (P < .001); animal control had the lowest unsuccessful test rate of all submitter types. Unsuccessful test rates differed when controlling for submitter type (P < .001) and animal type (P = .01). Submissions of bats by citizens had a significantly greater proportion of unsuccessful tests than submissions of bats by animal control (P < .001).

Conclusions: More than three-quarters of unsuccessful tests were attributed to bats, skunks, and raccoons, emphasizing the need to improve submission quality for these animals. We recommend training Utah rabies response partners on proper specimen handling and submission. Efforts should also focus on educating citizens to route submissions through trained rabies responders. Conducting focus groups with specific entities that have the lowest unsuccessful test rates could yield model submission practices.