Research Summary - 4
Surveillance and risk assessment of Salmonella enterica serotype Dublin in Pennsylvania dairy herds using bulk tank testing and a mobile application
| Date/Time: |
9/13/2025
15:00
|
| Author: |
Grazielle Cioletti |
| Clinic: |
The Pennsylvania State University |
| City, State, ZIP: |
University Park, PA 16802 |
Grazielle Cioletti , BS
1
;
Sophia Kenney , PhD
1
;
Ernest Hovingh , DVM, PhD
2
;
Adrian Barrigan , DVM, MS, PhD
2
;
Melissa Cantor , MS, PhD
1
;
Erika Ganda , DVM, PhD
1
;
1Department of Animal Science, The Pennsylvania State University, University Park, PA 16802
2Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, PA 16802
Introduction:
Salmonella enterica serotype Dublin (S. Dublin) is a zoonotic, host-adapted pathogen increasingly isolated in northeastern U.S. dairy cattle. It causes high calf mortality (20-100%) due to severe respiratory illness, while many infected animals remain asymptomatic carriers. These carriers shed intermittently, often during periods of stress, complicating detection and control. S. Dublin spreads through high-risk management practices such as calf housing, maternity pens, and herd movement, making strong biosecurity and structured risk assessments essential for control. In Pennsylvania, herd-level prevalence remains unreported, and practical tools for producers to identify and manage S. Dublin risks are lacking. This project aimed to estimate S. Dublin herd prevalence using ELISA testing of bulk tank milk samples, and to develop a mobile application to help producers assess on-farm transmission risks.
Materials and methods:
From January to April 2023, 192 bulk tank milk samples were collected from 102 Pennsylvania dairy herds via Lancaster DHIA. Samples were tested for S. Dublin antibodies using the PrioCHECKTM (Thermo Fisher Scientific, USA) ELISA. Forty-one herds submitted one sample, while 61 submitted two or more. A herd was considered positive if at least one sample tested positive. Although quarterly testing is preferred to improve detection of intermittent shedding, sampling in this study occurred irregularly between January and April. Follow-up sampling is currently ongoing to expand coverage and improve precision of prevalence estimates. In 2025, a mobile risk assessment tool was developed using Flutter (iOS alpha) to evaluate farm management risk factors for S. Dublin. Adapted from a Danish advisory manual, the app includes an educational section and structured multiple-choice questions that generate a visual heatmap of high-risk practices. Internal and on-farm testing informed revisions to improve clarity and usability. Producer feedback is being collected during pilot evaluation.
Results:
Of the ELISA-tested bulk tank milk samples, 4% (8/191) tested samples were positive for Salmonella Dublin antibodies. The apparent herd-level prevalence was approximately 2.9% (3/102). All three positive herds were consistently positive (4/4, 3/3 and 1/1). Among the 99 negative herds, 59 were tested more than once and remained negative; 40 were tested only once. No herd had both positive and negative results. These findings support the importance of repeated testing for detecting persistent infections and highlight the limitations of single-timepoint sampling for identifying herds with intermittent S. Dublin shedding. Although testing was not performed strictly quarterly, additional herd testing is ongoing to improve prevalence estimates and better capture its regional variability. The mobile app is currently in alpha testing. Between July 9–27, 2025, it received 250 App Store views, 23 product page views, and 17 downloads (5.88% conversion rate), with no reported crashes and an average of 3.8 sessions per device. Academic reviewers provided initial feedback on usability and educational content, while additional farmer input is guiding improvements for on-farm applicability.
Significance:
This study provides initial herd-level prevalence data for S. Dublin in Pennsylvania and highlights the value of repeated bulk tank ELISA testing in identifying infections. Persistent positives across timepoints emphasize the need for longitudinal sampling to improve detection sensitivity. We also developed the first mobile app specifically for S. Dublin risk assessment, which received positive academic feedback and demonstrated strong early usability and engagement based on initial usage data. While broader validation is ongoing, the app shows promise as a practical tool for herd-level risk identification and education. These tools may improve early detection and control of a multidrug-resistant, underdiagnosed pathogen of increasing importance in U.S. dairy herds.
