Tylvalosin, chemically known as tartrate acetylisovaleryl tylosin, has been a key tool for addressing the two major challenges of tylosin resistance and low blood concentrations in bacteria and mycoplasmas since its development in the early 1980s by Japanese scientists including Okamoto. Its mechanism of action is similar to that of other macrolide antibiotics: it binds to the 50S ribosome subunit of susceptible bacteria, blocking transpeptidation and mRNA displacement, thereby inhibiting peptide synthesis and elongation, ultimately affecting bacterial protein synthesis. Studies have shown that the effective mechanism of tylosin against drug-resistant bacteria lies in its tight binding to the 70S ribosome and its ability to increase cell membrane permeability.
Tylvalosin exhibits antibacterial activity against a wide range of Gram-positive bacteria, including Staphylococci, Micrococci, Microbacteria, Bacillus, Corynebacterium, Aerococcus, Campylobacter, Enterococci, Streptococci, Arthrobacter, and Clostridium. It also exhibits excellent antibacterial activity against mycoplasmas, especially at high concentrations. However, tylvalosin is inactive against most Gram-negative bacteria. Furthermore, it exhibits significant therapeutic activity against pathogens such as Mycoplasma hyopneumoniae, Brachyspira hyodysenteriae, and Lawsonia intracellularis.
Tylvalosin's primary functions can be summarized in three aspects: First, it effectively inhibits the replication of PRRS virus, thereby controlling outbreaks of PRRS on pig farms. Multiple studies have demonstrated that tylvalosin significantly inhibits the replication of both European and American PRRS viruses in vitro. Since its introduction to China in 2004, researchers have conducted numerous in vitro and in vivo experiments and field trials, further confirming its ability to inhibit PRRS virus replication in pigs. Furthermore, in practical applications, while the addition of appropriate amounts of tylvalosin to nursery pigs and lactating sows cannot completely prevent PRRS virus infection, it can significantly reduce mortality on pig farms. Furthermore, when used in combination with a live PRRS vaccine, tylvalosin can further reduce overall mortality, abortion, and culling rates.
Secondly, tyvalosin can significantly reduce the inflammatory response and lung damage caused by blue ear disease virus. Researchers have found that blue ear disease virus infection requires a low pH environment in the endosome, and tyvalosin can just increase the pH value of the endosome, thereby effectively inhibiting viral replication. In summary, as an important antibiotic drug, tyvalosin plays a key role in resolving bacterial and mycoplasma infections. Its unique mechanism of action and broad antibacterial activity against a variety of pathogens make it an important choice in veterinary clinical practice. (2) Control of mycoplasma pneumonia in pigs tyvalosin can directly and quickly reach the damaged area of cilia, continuously and efficiently kill mycoplasmas, and become the most sensitive drug for the treatment of mycoplasma infection. Japanese and British scholars have conducted clinical trials on the efficacy of tyvalosin against mycoplasma. The results showed that after piglets were artificially challenged with the virus, tyvalosin was administered through mixed drinking water, showing significant clinical therapeutic effects. (3) Control of Ileitis
Porcine ileitis is a digestive tract disease caused by Lawsonia intracellularis, characterized by hemorrhagic, persistent or intermittent diarrhea, and its incidence has continued to rise in recent years. Tylvalosin can quickly penetrate intestinal epithelial cells and act on the ribosomes of Lawsonia intracellularis, causing bacterial death and thus completely curing ileitis. Elizabeth et al., scholars from the United States and Canada, conducted an experiment on intracellular Lawsonia intracellularis infection in 5-week-old piglets. They used the method of administering tylvalosin in drinking water for treatment and successfully reduced the IHC positive rate of intracellular Lawsonia intracellularis in the infected pigs from 90% to below 40%.
