In 2023, Dr. Isadora Machado published her research Assessment of changes in antibiotic use in grow-finish pigs after the introduction of PRRSV in a naïve farrow-to-finish system. The research identified that the PRRS virus significantly increases the need for antibiotics.1
In fact, Dr. Machado’s research found that antibiotic use for piglets increased by more than 3.5 times during the first 15 weeks after a PRRS outbreak on a farm. For older pigs, the use of antibiotics increased by more than 2.5 times.
We recently sat down with Dr. Machado to dig deeper into her research and the ways she hopes it benefits both the industry and consumers.
Question: Tell us more about your background?
Dr. Machado:
I graduated from veterinary school in Brazil in 2018. During my final year, I spent one year in Germany completing an internship in a breeding herd.
The farm had about 500 sows, and it was there that I learned the fundamentals of swine production, working closely with swine producers who had over 30 years of experience. It was a great learning opportunity. While in Germany, I also completed technical studies in agriculture and livestock production.
After returning to Brazil in 2018, I joined the Brazil Foods Company, the largest swine production system in the country. There, I worked as an extension swine veterinarian, and during my final year, I transitioned into a role focused on swine health assurance.
After that, I moved to the United States to pursue my graduate degree in epidemiology. Initially, I planned to complete only a master’s degree, but over time, I realized I wanted a deeper understanding of health solutions, which led me to pursue a PhD program.
Question: Why did you choose to focus your research during your master’s on antibiotics?
Dr. Machado:
This is a topic that interests me. When we see sick animals, we medicate them because we want them to recover as quickly as possible. When I came to the United States, I first came into contact with PRRSV. From my background in swine health assurance, I became interested in understanding how much antibiotic use was associated with PRRSV infection. We knew that PRRS could lead to antibiotic use, but we just didn’t know exactly how much. It’s always important to actually quantify a problem before taking action on it.
Question: How does PRRS increase the need for antibiotics?
Dr. Machado:
It’s an interesting question because we are talking about a virus and then about antibiotics, which at first does not seem to make sense, since antibiotics are primarily used to treat bacterial infections. But, ironically, PRRSV infects and replicates in immune cells, primarily macrophages, which are the line of defense against infections.
When a pig is infected with PRRSV, a virus that causes systemic disease, its immune system will be compromised, and the animal becomes more susceptible to other bacterial infections. As a result, you need antibiotics to treat those co-infections.
Question: The swine industry believes in the judicious use of antibiotics. At the same time, your research found a staggering increase in the need for antibiotics as a result of PRRS. With your background as both a veterinarian and a researcher, how can we prioritize reducing the need for antibiotics while also using them when necessary?
Dr. Machado:
That’s a great point. When we talk about reducing antibiotic use, it’s not like we are telling producers to not to use antibiotics. Animals need to be treated when they are sick, and producers should also comply with animal welfare regulations. We don’t want animals to suffer, so we need to treat them.
From an antimicrobial stewardship perspective, we need to understand the use of antibiotics within a system, such as what we did in our study. Another important aspect is understanding which pathogens are present in those systems, such as PRRSV, and whether we can prevent animals from becoming infected in the first place. So, now that we understand that PRRSV significantly increases the need for antibiotics, the focus can shift from simply reducing antibiotic use to addressing the cause of the problem, such as preventing PRRSV infection. Improving antimicrobial stewardship focuses on understanding why antibiotics are needed and identifying opportunities, such as reducing or eliminating pathogens within a system.
Question: The numbers in your research are significant. What do you think they tell us about the way PRRS impacts pigs?
Dr. Machado:
There are previous studies conducted in Denmark, Italy, and France that reported similar outcomes, although the increases observed were not as high as those we found. One important consideration is that the data from those studies came from production systems that were previously PRRSV-positive stable, meaning the farms had previously experienced PRRSV, and the animals likely had some level of immunity when they were exposed to another strain of PRRSV.
Unlike those studies, the one we conducted in the United States was from a multiplier production system that had never experienced a PRRSV outbreak before; in other words, they were naïve pigs to PRRSV. Thus, the lack of immunity likely contributed to the magnitude of the impact we observed. The results were surprising to me.
Question: Why is it important for the industry to try to reduce the incidence of PRRS?
Dr. Machado:
It’s important because PRRS is a systemic disease that critically affects swine health. If you don’t have control over it, it leads to multiple animal health challenges, such as increased mortalities, with survivor pigs often becoming very sick, resulting in a consequently increased need for antibiotic use. So, the impact of this virus extends beyond economic considerations.
Question: What do you hope the industry learns from your research?
Dr. Machado:
When it comes to PRRSV, we must continue to understand its impacts on production, and we need to continue improving our surveillance programs to prevent farms from becoming infected. Of course, advances in technology are also warranted, such as vaccination strategies. However, while many commercial vaccines are available, PRRSV remains challenging to control with vaccination because the virus mutates rapidly. Lastly, emerging technologies, such as gene-editing approaches, are very promising. We’ve been struggling with PRRSV for more than 30 years, and in many ways, the problem has continued to grow. New technologies offer an exciting opportunity to transform the way we manage PRRSV in the future.
The views, thoughts and opinions expressed in this article are those of Dr. Machado and do not necessarily reflect the views, policies or positions of PIC.
Sources:
- Machado, I., Petznick, T., Poeta Silva, A. P. S., Wang, C., Karriker, L., Linhares, D. C. L., & Silva, G. S. (2024). Assessment of changes in antibiotic use in grow-finish pigs after the introduction of PRRSV in a naïve farrow-to-finish system. Preventive Veterinary Medicine, 233, 106350. https://doi.org/10.1016/J.PREVETMED.2024.106350
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