Herd-level prevalence of bovine leukemia virus, Salmonella Dublin, and Neospora caninum in Alberta, Canada, dairy herds using ELISA on bulk tank milk samples

• Published in: Journal of dairy science 2024-10, Vol.107 (10), p.8313-8328
• Main Authors: Shaukat, Waseem, de Jong, Ellen, McCubbin, Kayley D., Biesheuvel, Marit M., van der Meer, Frank J.U.M., De Buck, Jeroen, Lhermie, Guillaume, Hall, David C., Kalbfleisch, Kristen N., Kastelic, John P., Orsel, Karin, Barkema, Herman W.
• Format: Article
• Language: English
• Subjects: Alberta - epidemiology; Animals; bovine leukosis; Cattle; Cattle Diseases - epidemiology; Coccidiosis - epidemiology; Coccidiosis - veterinary; Cross-Sectional Studies; dairy farms; Dairying; Enzootic Bovine Leukosis - epidemiology; Enzyme-Linked Immunosorbent Assay - veterinary; Female; Leukemia Virus, Bovine; Milk - microbiology; Neospora; neosporosis; Prevalence; Salmonella - isolation & purification; Salmonella Dublin; Salmonella Infections, Animal - epidemiology; surveillance
• ISSN: 0022-0302; 1525-3198
• DOI: 10.3168/jds.2023-24611

The list of standard abbreviations for JDS is available at adsa.org/jds-abbreviations-24. Nonstandard abbreviations are available in the Notes. Endemic infectious diseases remain a major challenge for dairy producers worldwide. For effective disease control programs, up-to-date prevalence estimates are of utmost importance. The objective of this study was to estimate the herd-level prevalence of bovine leukemia virus (BLV), Salmonella enterica ssp. enterica serovar Dublin (Salmonella Dublin), and Neospora caninum in dairy herds in Alberta, Canada, using a serial cross-sectional study design. Bulk tank milk samples from all Alberta dairy farms were collected 4 times, in December 2021 (n = 489), April 2022 (n = 487), July 2022 (n = 487), and October 2022 (n = 480), and tested for antibodies against BLV, Salmonella Dublin, and N. caninum using ELISA. Herd-level apparent prevalence was calculated as positive herds divided by total tested herds at each time point. A mixed-effect modified Poisson regression model was employed to assess the association of prevalence with region, herd size, herd type, and type of milking system. Apparent prevalence of BLV was 89.4%, 88.7%, 86.9%, and 86.9% in December, April, July, and October, respectively, whereas for Salmonella Dublin apparent prevalence was 11.2%, 6.6%, 8.6%, and 8.5%, and for N. caninum apparent prevalence was 18.2%, 7.4%, 7.8%, and 15.0%. For BLV, Salmonella Dublin, and N. caninum, a total of 91.7%, 15.6%, and 28.1% of herds, respectively, were positive at least once, whereas 82.5%, 3.6%, and 3.0% of herds were ELISA positive at all 4 times. Compared with the north region, central Alberta had a high prevalence (prevalence ratio [PR] = 1.13) of BLV antibody-positive herds, whereas south Alberta had a high prevalence (PR = 2.56) of herds positive for Salmonella Dublin antibodies. Furthermore, central (PR = 0.52) and south regions (PR = 0.46) had low prevalence of N. caninum-positive herds compared with the north. Hutterite colony herds were more frequently BLV positive (PR = 1.13) but less frequently N. caninum-positive (PR = 0.47). Large herds (>7,200 L/d milk delivered ∼>250 cows) were 1.1 times more often BLV positive, whereas small herds (≤3,600 L/d milk delivered ∼≤125 cows) were 3.2 times more often N. caninum positive. For Salmonella Dublin, Hutterite colony herds were less frequently (PR = 0.07) positive than non-colony herds only in medium and large strata but not in small stratum. Moreover, larger he