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Volume 28, Number 8—August 2022
Dispatch

Culling of Urban Norway Rats and Carriage of Bartonella spp. Bacteria, Vancouver, British Columbia, Canada

Kaylee A. Byers1Comments to Author , Michael J. Lee1, Janet E. Hill, Champika Fernando, Laura Speerin, Christina M. Donovan, David M. Patrick, and Chelsea G. Himsworth
Author affiliations: The University of British Columbia School of Population and Public Health, Vancouver, British Columbia, Canada (K.A. Byers, M.J. Lee, C.M. Donovan, D.M. Patrick); The University of British Columbia, Vancouver (K.A. Byers, C.G. Himsworth); Canadian Wildlife Health Cooperative, Abbotsford, British Columbia, Canada (K.A. Byers, M.J. Lee, C.G. Himsworth); University of Saskatchewan, Saskatoon, Saskatchewan, Canada (J.E. Hill, C. Fernando, L. Speerin); British Columbia Centre for Disease Control, Vancouver (D.M. Patrick); British Columbia Ministry of Agriculture, Abbotsford (C.G. Himsworth)

Main Article

Table

Mixed effects logistic regression models of the effect of intervention on Bartonella spp. carriage by Norway rats (Rattus norvegicus), Vancouver, British Columbia, Canada*

Variable Bartonella prevalence, no. positive/no. tested (%) Bivariable models
 Final model†
Unadjusted OR (95% CI) p value in model LRT p value‡ Adjusted OR (95% CI) p value in model
Intervention
Rats caught before the intervention in all blocks 58/267 (22) Referent Referent Referent Referent Referent
Rats caught after the intervention in control blocks 24/109 (22) 1.26 (0.67–2.39) 0.47 <0.01 2.68 (1.22–6.67) 0.02
Rats caught after the intervention in flanking blocks 6/37 (16) 0.56 (0.18–1.46) 0.26 NA 7.26 (1.56–38.17) 0.01
Rats caught after the intervention in intervention blocks
 2/41 (5)
 0.12 (0.02–0.46)
 <0.01
 NA
2.03 (0.22–15.41)
 0.50
Sex
F 38/221 (17) Referent Referent Referent NA NA
M
 52/233 (22)
 1.32 (0.82–2.14)
 0.26
 0.26
NA
 NA
Sexual maturity
Juvenile 34/177 (19) Referent Referent Referent NA NA
Mature
 56/277 (20)
 0.98 (0.60–1.63)
 0.95
 0.95
NA
 NA
Wound presence
Absent 59/339 (17) Referent Referent Referent Referent Referent
Present
 31/115 (27)
 1.67 (0.97–2.81)
 0.06
 0.06
1.49 (0.83–2.63)
 0.17
Weight§
 NA
 1.04 (0.81–1.32)
 0.75
 0.75
NA
 NA
Presence of fleas on rats
Absent 46/261 (18) Referent Referent Referent NA NA
Present 44/193 (23) 1.39 (0.86–2.25) 0.18 0.18 NA NA
No. fleas on rat NA 1.02 (0.95–1.09) 0.50 0.52 NA NA
Flea index# NA 1.13 (0.90–1.43) 0.31 0.32 NA NA
Presence of positive fleas per rat
Absent 67/376 (18) Referent Referent Referent Referent Referent
Present
 23/78 (30)
 1.83 (1.00–3.25)
 0.04
 0.05
1.94 (1.00–3.69)
 0.05
Season
Summer, June–August 16/124 (13) Referent Referent Referent Referent Referent
Fall, September–November 65/208 (31) 3.16 (1.59–6.73) <0.01 <0.01 2.90 (1.32–6.31) <0.01
Winter, December–March 9/122 (7) 0.50 (0.18–1.30) 0.15 NA 0.16 (0.03–0.68) 0.02

*OR refers to the odds of Bartonella spp. carriage among rats in each group relative to the reference group for that variable. Variables were included in the final model if they confounded the relationship between the intervention; and the outcome (changed the effect of any level of the intervention by >10% and/or were associated with the outcome and intervention, p<0.25) or if they were independent predictors that improved the model as indicated by a significant (p<0.05 likelihood ratio test with all confounders and intervention present). LRT, likelihood ratio test; NA, not applicable; OR, odds ratio. †Final multivariable model: Bartonella status ~ intervention + wound presence + presence of positive fleas per rat + season + (city.block). ‡Likelihood ratio test comparing the generalized linear mixed model with and without the indicated variable; p<0.05 indicates that the variable significantly improved the model with all confounders and as such was a significant predictor and was retained in the final model. §Scaled and centered around its mean. #Average number of fleas per rat per city block.

Main Article

1These first authors contributed equally to this article.

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Page updated: July 20, 2022
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