Longitudinal Prevalence of Antibodies to Endemic Pathogens in Bulk Tank Milk Samples From Dairy Herds Engaged or Not in Contract Heifer Rearing

Abstract

Since the abolition of EU milk production quotas in 2015, Europe's dairy industries have undergone a period of rapid expansion with possible resultant increased inter-herd transmission of endemic pathogens. The aims of this study were (1) to establish the post-2015 prevalence of antibodies to selected endemic infectious diseases and (2) to determine if prevalences differed between herds where heifers were reared at home and those where heifers were sent out for contract-rearing. Three bulk tank milk (BTM) samples were collected annually between May and August of 2018–20 inclusively from 120 Irish dairy herds. Additionally, herd vaccination status was collected by questionnaire. Milk samples were tested using commercially available ELISAs for eight pathogens: bovine viral diarrhea virus (BVDV), bovine herpesvirus 1 (BoHv-1), bovine respiratory syncytial virus (BRSV), Mycoplasma bovis, Mycobacterium avium subspecies paratuberculosis (MAP), Salmonella Dublin (S. Dublin), Leptospira Hardjo (L. Hardjo), and Neospora caninum (N. caninum). The true prevalence of each pathogen was calculated using a Rogan-Gladen estimator. The true prevalences (95% CI) of BTM antibodies in unvaccinated herds across the 3 years were as follows (i) BVDV: 57, 86, and 73% (95% CI: 40.7–65.9, 74–94, and 58–85) (n = 56, 56, and 48), (ii) BoHv-1: 47, 49, and 19% (95% CI: 26.3–69.7, 25–75, and 1–56) (n = 21, 20, and 11), (iii) L. Hardjo: 34, 59, and 73% (95% CI: 12.5–63, 33–82, and 33–99) (n = 15, 21, and 10), (iv) S. Dublin 32, 57, and 11% (95% CI: 12.21–68.1, 30.2–90.1, and 0) (n = 19, 22, and 13), (v) BRSV: 100% (95% CI: 99.5–100, 100, and 100) (n = 120, 109, and 91), (vi) MAP: 0% (95% CI: 0, 0, and 0) (n = 120, 109, and 91) (vii) N. caninum 0% (95% CI: 0, 0, and 0) (n = 120, 109, and 91) and (viii) M. bovis (ELISA) 53, 0.42, and 30% (95% CI: 3.95–6.84, 0, and 21–41) (n = 120, 109, and 91). M. bovis was detected by PCR in 0, 1, and 0% of herds in 2018, 2019, and 2020, respectively. This study showed that expanding Irish dairy herds are endemically infected with several of the studied pathogens. No differences in herd prevalence of infectious agents were observed between farms with different heifer rearing strategies (contract-rearing vs. traditional rearing).

Economic analysis of biosecurity adoption in dairy farming: evidence from Ireland

“…The findings indicate that testing milk against diseases is associated with an economic gain of €103 GM/cow, which is significant at the 5% level. The importance of bulk tank milk screening has been documented in past studies (see Jayaro et al, 2003 ; Kelly et al, 2009 ; McCarthy et al, 2021b ). This provides further empirical evidence of the likely economic importance of adopting on-farm disease prevention measures.…”

Molecular Characterisation and Antibody Response to Bovine Respiratory Syncytial Virus in Vaccinated and Infected Cattle in Turkey

“…In the present study, antibody response to vaccination and infection was investigated using ELISA. Other studies have detected the seroprevalance of BRSV in Europe as between 11.6% to 100%; the rate was 11.6% in Spain [ 42 ], 69.1% in Italy [ 10 ], and 100% in Ireland [ 43 , 44 ]. It has been emphasized that low prevalence is correlated with the presence of maternal antibodies, while high prevalence (90%) is associated with a history of pneumonia [ 44 ].…”

Milk as a diagnostic fluid to monitor viral diseases in dairy cattle

“…Tests of pooled milk can be a cost‐effective tool for assessing disease status in a herd and for monitoring endemic viruses 1,2 . The combined milk collected from a dairy farm contains valuable target analytes that can identify infection or prior exposure to pathogens.…”

“…Tests of pooled milk can be a cost-effective tool for assessing disease status in a herd and for monitoring endemic viruses. 1,2 The combined milk collected from a dairy farm contains valuable target analytes that can identify infection or prior exposure to pathogens. Testing bulk milk has been critical in disease eradication programmes to determine herd infection status and to build confidence of freedom from infection for specific agents.…”