Bacterial respiratory infections in horses are often secondary and primarily initiated by viral disease, since viral respiratory infections impair and/or destroy respiratory defense mechanisms. The most common organisms associated with pneumonia in horses are opportunistic bacteria originating from the resident microflora of the upper respiratory tract.1 Evidence of a secondary bacterial infection often includes mucopurulent nasal discharge, depression, persistent fever and abnormal lung sounds. 

Secondary bacterial infections may also result in mucosal bacterial infections such as rhinitis and tracheitis, or may produce more serious invasive disease such as pneumonia and pleuropneumonia. Streptococcus equi zooepidemicus is the most common opportunistic pathogen of the equine lung, although Actinobacillus equuli, Bordetella bronchiseptica, Escherichia coli, Pasteurella spp, and Pseudomonas aeruginosa also frequently occur. S equi equi, the causative agent of strangles, is a primary bacterial pathogen of the upper respiratory tract and is capable of mucosal invasion without predisposing factors. Rhodococcus equi is a primary pathogen of the lower respiratory tract of foals and produces pulmonary consolidation and abscessation. R. equi pneumonia has been reported in horses with compromised immune systems.1

Sulfadiazine and Trimethoprim for Equines

Sulfonamides are bacteriostatic agents, while trimethoprim is bactericidal. When used in combination, the resulting potentiated sulfonamides are bactericidal. Potentiated sulfonamides sequentially inhibit enzymes in the folic acid pathway, inhibiting bacterial thymidine synthesis. Sulfonamides compete with para-aminobenzoic acid (PABA) to reduce bacterial dihydrofolic acid (DFA) formation, and trimethoprim blocks the conversion of DFA to tetrahydrofolic acid by preferentially inhibiting bacterial dihydrofolate reductase.3

Where to buy Sulfadiazine + Trimethoprim 

Sulfadiazine + Trimethoprim is available in the U.S. through several pharmaceutical manufacturers and through veterinary custom compounding companies. SULFADIAZINE 416 MG/ML / TRIMETHOPRIM 83 MG/ML by NexGen Pharmaceuticals is indicated for the treatment of a variety of bacterial infections in the horse.

This product carries numerous potential drug interactions. Please consult your veterinarian prior to beginning any treatment regimen.

FOR RX ONLY: A valid prescription from a licensed veterinarian is required for dispensing this medication.

1Merck Veterinary Manual.

3equimed.com.