Strep suis resurfacing to challenge high-health herds
What’s old is new again — or at least that’s what some high-health herds are finding with Streptococcus suis (Strep suis).
“We have seen the Strep suis incidence increase in the past 5 years and, in some cases, the severity has increased tremendously,” Joe Connor, DVM, Carthage Veterinary Service, told Pig Health Today.
High-health herds may be particularly vulnerable because as other viruses and bacteria are eliminated, it opens the door for Strep suis to become a key component of residual mortality in growing pigs.
Although Strep suis can routinely be found in the sow population, its renewed impact is likely due to the combination of multiple factors. Among the reasons Connor cited:
- Reduced antibiotic use, both in-feed and injectable applications.
- Moving to larger groups of pigs in wean-to-finish barns.
- Virulence changes of a particular strain of the bacterium. “We still don’t fully understand virulence factors,” Connor noted.
- Advancements in detecting differences in Strep suis strains, thereby providing a better understanding of the bacterium.
“But we still don’t have the technology to recover a particular bacterial isolate and be confident that it’s the only one involved in the mortality and morbidity,” he added. “Producers and veterinarians commonly find there are three to four different strains involved.”
Early detection is key
It’s not feasible to eliminate the bacterium today, so the focus needs to be on treatment, control and prevention. And, starting with treatment, the key to success is early detection.
“From production records we know that early detection and treatment result in a 50% to 75% recovery rate,” Connor said. “Otherwise the recovery rate is well below 50%.”
Train and emphasize to pig caretakers to walk the pens each day and carefully look for clinical signs such as a single swollen joint or lameness of a single leg. Another sign, he added, is if a pig gets up and takes an awkward step, but steps 2 and 3 look fine. “This suggests that Strep suis hasn’t yet moved to the brain; so, there’s no encephalitic-type signs,” Connor noted.
Fast eye movements and elevated rectal temperatures — 105° F or 106° F (40° C or 41° C) — also are indicators of infection. Tissue samples from the brain or lung are needed to validate suspicions, as well as to determine the Strep suis strain’s antibiotic sensitivity for treatment.
With early detection and low prevalence, individual pig treatment is the preferred course of action. However, if piglet morbidity and mortality are beyond the farm’s threshold or infection continuously recurs, it calls for feed-grade or water-soluble antibiotic treatments indicated for Strep suis, Connor said.
Prevention is challenging
Prevention involves intensive navel-cord treatments for newborn piglets, thorough room and equipment sanitation, and providing proper environmental conditions in the farrowing house and early-weaning stage. “Look for stressors that might influence Strep suis, particularly in the first 30 days post-weaning,” he noted.
If morbidity and mortality are out of hand, the final preventive measure is to consider vaccinating sows pre-farrowing to protect nursing piglets, or vaccinate the piglets themselves to provide protection in the early-weaning phase. The only vaccination option is to develop a farm-specific, autogenous vaccine, which re-emphasizes the importance and challenge of identifying the strain or strains.
Ultimately, Connor concluded that Strep suis treatment, control and prevention depend on the producer’s or veterinarian’s persistence to identify the multiple isolates that contribute to increased morbidity and mortality.