Leptospirosis: An important infectious disease in North American horses.

North American horses are commonly exposed to Leptospira organisms. Leptospira Bratislava is the most common infecting serovar but this serovar has not been confirmed to cause clinical disease in North American horses. Leptospira Pomona type kennewicki is responsible for most of the clinical diseases (leptospirosis) in North American horses. Leptospirosis is most commonly associated with diseases of the placenta and fetus, the kidneys and the eyes in horses. In-utero infections in pregnant mares may result in abortion, neonatal illness or birth of an antibody positive healthy foal. Acute renal failure in younger horses and recurrent uveitis in adult horses are other well documented clinical syndromes of leptospirosis. Abortions, neonatal disease and acute renal failure are caused by a subacute infection, while horses with Leptospira associated recurrent uveitis develop ocular disease months or years after the initial Leptospira infection. Diagnosis of Leptospirosis is made by a combination of antigen or antibody testing methods. Mares that abort following Leptospira infection have no additional clinical signs at the time of abortion but may shed the offending Leptospira spp. in the urine for several weeks. Antibiotic treatments are sometimes used in hopes of decreasing Leptospira shedding in infected horses or prophylactically in exposed pregnant mares but documentation of efficacy is lacking. Horses with Leptospira - associated acute renal failure can be successfully treated with antibiotics and supportive care. Recurrent uveitis is commonly associated with leptospirosis in North American horses and although horses may have chronic intraocular infection triggering an immune disease, systemic antimicrobial therapy has not been effective in eliminating the organism from the eye. An equine approved Leptospira Pomona type kennewicki vaccine is now available in North America.

Ocular penetration of intravenously administered enrofloxacin in the horse.

REASON FOR PERFORMING STUDY: Information on antibiotic concentrations in the equine eye following systemic therapy is limited. Reports that Leptospira spp. are frequently present in the eyes of horses with recurrent uveitis, emphasises a need for studies on ocular concentrations of specific antibiotics. HYPOTHESES: 1) Enrofloxacin, administered i.v. at 7.5 mg/kg bwt q. 24 h, results in aqueous humour concentrations greater than the reported minimum inhibitory concentration (MIC) for Leptospira pomona. 2) Aqueous humour paracentesis sufficiently disrupts the blood-aqueous humour barrier (BAB) to cause an increase in aqueous humour protein and enrofloxacin concentrations. METHODS: Aqueous humour enrofloxacin and total protein concentrations were determined in 6 healthy, mature horses after i.v. administration of enrofloxacin. Paracentesis was performed on the left eye on Days 3 and 4, 1 h following enrofloxacin administration, to determine enrofloxacin concentrations in healthy eyes and in eyes with mechanical disruption of the BAB. Paracentesis was also performed on the right eye 23 h after enrofloxacin administration. Blood samples were collected from the horses at identical times to determine enrofloxacin aqueous humour:plasma ratios. RESULTS: Mean +/- s.d. enrofloxacin concentration in the aqueous humour 1 h post administration on Day 3 was 0.32 +/- 0.10 mg/l (range 0.18-0.47); and aqueous humour enrofloxacin, total protein and aqueous humour:plasma enrofloxacin ratios were higher on Day 4 than Day 3. CONCLUSIONS AND POTENTIAL RELEVANCE: Following disruption of the BAB, enrofloxacin concentrations were above the reported MIC for Leptospira pomona.

Topical treatment of Pseudomonas sp-infected corneal ulcers in horses: 70 cases (1977-1994).

OBJECTIVE: To determine which antimicrobial agents were most effective against Pseudomonas sp-infected ulcerative keratitis, and identify any trends in the various clinical conditions associated with these bacteria that might assist in effective treatment of the disease. DESIGN: Retrospective case series. ANIMALS: 66 horses with 70 Pseudomonas sp-infected corneal ulcers. PROCEDURE: We reviewed medical records of horses admitted to the George D. Widener Hospital for Large Animals, University of Pennsylvania between July 1977 and December 1994. Records of horses that had Pseudomonas sp isolated from a corneal ulcer scraping or deep swab were included in the study. RESULTS: Aggressive topical medical treatment was successful in 57 ulcers and most likely would have been effective in 5 additional ulcers. Antimicrobial susceptibility testing indicated susceptibilities of 87, 85, and 93% to tobramycin, gentamicin, and amikacin, respectively. Although concurrent fungal infections were identified in only 2 of 35 ulcers examined, almost three fourths of the ulcers were treated with antifungal medications prophylactically. Clinical outcomes of the 70 affected eyes included: excellent vision with minimal leukoma, 73%; enucleation, 19%; blind phthisical eye, 4%; peripheral vision only, 3%; and euthanasia of newborn, 1%. CLINICAL IMPLICATIONS: Aggressive topical medication with microbial agents effective against Pseudomonas sp can result in excellent vision with minimal leukoma in most horses with corneal ulcers.

Ocular lymphangiosarcoma in a cow.

Ocular lymphangiosarcoma was diagnosed in a Holstein cow with a progressively enlarging limbal mass. The cow was treated by exenteration. The cow survived for 2 years without clinical signs of recurrence. Lymphangiosarcoma is a vascular neoplasm that rarely has been reported in domestic animals. In other species, it has a high rate of metastasis and is associated with poor long-term survival.