This is our Friday rubric: every week a new Science Page from the Bob Morrison’s Swine Health Monitoring Project. The previous editions of the science page are available on our website.
For today’s Science Page we bring you a study by Iowa State University researchers Isadora Machado, Thomas Petznick, Ana Paula Silva, Chong Wang, Locke Karriker, Daniel Linhares, and Gustavo Silva taking a look at the association between PRRSV-positive status and increased antibiotic usage in the growing pig population.
Highlights:
- PRRSV-positive epidemic and endemic grow-finish lots were associated with higher antibiotic use (ABU).
- In the nursery phase, the ABU via injectable and oral routes increased up to 3.8 times from naïve to PRRSV-positive epidemic status. Similar findings were observed when comparing mg/PCU between PRRSV statuses.
- In the finishing phase, ABU via injectable route increased by up to 2.7 times from the naïve to PRRSV-positive epidemic status.
Background: Porcine reproductive and respiratory syndrome virus (PRRSV) is a swine pathogen with immunosuppressive effects that can exacerbate the clinical impacts of bacterial co-infections. As a result, the increased need for antibiotics to treat affected animals increases treatment costs and affects antimicrobial stewardship. Thus, this study aimed to quantify the antibiotic use (ABU) increase associated with PRRSV infection in nursery and grow-finish lots after introducing PRRSV-2 in a previously PRRSV-naïve farrow-to-finish genetic multiplier system.
Material and Methods: Retrospective data was gathered from a 4,500-sows single-source farrow-to-finish genetic multiplier system in the United States. The system was negative for Mycoplasma hyopneumoniae and porcine coronaviruses, such as PEDV, PDCoV, and TGEV. Daily data on animal transfers, mortality, and ABU (oral [via water] and intramuscular [via injectable] routes) were collected from the nursery and finishing phases (from May 2020 to December 2021). The studied population was categorized into three PRRSV statuses determined by PRRSV circulation within the sow farm at the weaning phase: naïve, positive epidemic, and positive endemic statuses. For the ABU statistical analysis, the “Pig treatment per animal days at risk” (PTDR) metric was calculated per route by dividing the medicated animals by animal days at risk for each lot. To report antibiotic consumption and the biomass of the population for each lot, the milligrams per population correction unit (mg/PCU) by using the weight of the antibiotic active ingredient as the numerator and the population correction unit (PCU) as the denominator. Generalized linear mixed models and non-parametric tests were used to assess the differences between PRRSV status, and the statistical analyses were performed using the R program.
Results: ABU was assessed from 135,063 placed animals: 166 nurseries and 39 finishing lots.
- Ampicillin was the most common injectable antibiotic administrated (40% of total use), followed by lincomycin (39%) and enrofloxacin (21%). Neomycin was most common via oral (78% of total use), followed by penicillin (16%), sulfamethoxazole (3%), and tylvalosin (3%).
- Nursery phase:
- Overall PTDR (via oral and injectable routes): ABU increase of 3.8 and 2.5 times in the positive epidemic and endemic statuses, respectively, compared to the naïve status.
- Injectable PTDR: ABU increase of 2.2 and 1.4 times in the positive epidemic and endemic statuses, respectively, compared to the naïve status.
- Water PTDR: ABU increase of up to 3.5 times in the positive epidemic status compared to the naïve status.
- mg/PCU: 22.3 mg/PCU for naïve, 86.7 for positive epidemic, and 33.4 for positive endemic statuses.
- Finishing phase:
- Overall and Water PTDR: no statistical difference across PRRSV statuses.
- Injectable PTDR: ABU increase of 2.7 and 2.3 times in the positive epidemic and endemic statuses, respectively, compared to the naïve status.
- mg/PCU: 81.3 mg/PCU for naïve, 76.5 for positive epidemic, and 67.1 for positive endemic statuses.
Discussion and Conclusions: This study revealed a significant association between PRRSV-positive status and increased antibiotic usage in the growing pig population. While these findings are informative, they should be interpreted cautiously, as they pertain to a single production system. Nonetheless, the results underscore the potential rise in antibiotic consumption following the introduction of PRRSV-2 into a previously naïve farrow-to-finish operation. This emphasizes the critical need for effective control and prevention strategies against PRRSV-2 infections, given their role in exacerbating the impact of co-infections and consequently driving up antibiotic use.
The full article is available at https://doi.org/10.1016/j.prevetmed.2024.106350