How do I diagnose and treat urinary tract infection in rabbits, including E. cuniculi-related urinary disease?

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Urine culture via cystocentesis is the diagnostic cornerstone for bacterial urinary tract infection (UTI) in rabbits, with bacteria on urine microscopy serving as the best in-clinic screening test — sensitivity 71% and specificity 90% compared to culture results.5 For bacterial UTI diagnosis, urine should be collected by cystocentesis, which was the collection method in 94.8% of confirmed cases in the largest rabbit-specific UTI series.5 Bacteria on microscopic examination is the only parameter statistically associated with a positive culture; other clinical and ultrasonographic findings, including urinary sludge and signs consistent with pyelonephritis, do not reliably predict culture positivity.5 Urine culture should always be performed in rabbits with lower urinary tract signs, particularly when urinary stasis or sludge is present, as stasis is a recognized risk factor for secondary infection.10 The most common bacterial isolates are Escherichia coli (27.8% of isolates), Enterococcus faecalis (19.4%), and Staphylococcus spp (11.1%). Single-species infections account for 74.1% of positive cultures.5 Resistance rates are clinically significant: azithromycin 66.2%, penicillin 57.9%, sulfonamides-trimethoprim 31.4%, enrofloxacin 17.9%, and ceftiofur 17.1%.5 Overall, 52.8% of isolates are multidrug resistant, making empirical therapy unreliable — antibiotic selection should be guided by culture and susceptibility results in every case.5 For Encephalitozoon cuniculi-related urinary disease, serology is the appropriate in vivo diagnostic tool. A negative antibody titer rules out E. cuniculi as the cause of current clinical signs.6 Elevations in both anti–E. cuniculi IgM and IgG antibodies correlate with active infection, and antiparasitic treatment is indicated in rabbits with anti–E. cuniculi IgM antibodies.2 Urine PCR for E. cuniculi is unreliable for diagnosis of active infection: spores are shed in large numbers only during the first 2 months post-infection, sheddin