Antimicrobial-associated diarrhoea in three equine referral practices.

REASONS FOR PERFORMING STUDY: Although antimicrobial-associated diarrhoea (AAD) is the most frequently observed adverse effect of antimicrobial therapy in horses, few multicentred studies on the prevalence of AAD have been performed. OBJECTIVES: To determine the prevalence of AAD in horses that developed diarrhoea after antimicrobial treatment for nondiarrhoeic conditions and identify the antimicrobials used. METHODS: The 2009 database of 3 referral hospitals was searched to identify nonhospitalised horses (weanling age or older) treated with antimicrobials for nongastrointestinal conditions. Horses with these criteria that presented with diarrhoea during 2009 were included in the study. Additional information, including antimicrobial administered and results of faecal pathogen testing, was gathered on each hospitalised case. RESULTS: Of the 5251 horses treated with antimicrobials for nongastrointestinal signs, 32 were diagnosed with probable AAD, a prevalence of 0.6% (95% confidence interval: 0.43-0.86%). The AAD-diagnosed horses had an 18.8% (6/32) mortality rate. Horses with AAD had been treated for an average of 4.2 days. The most frequently used antimicrobials in horses with AAD were gentamicin in combination with penicillin (n = 7), enrofloxacin (n = 7) and doxycycline (n = 4). Clostridium difficile was identified in faecal samples from 4 horses, 2 of which died and Salmonella from 3 horses. CONCLUSIONS: Results indicated that the prevalence of AAD is low. Any antimicrobial class commonly used in equine practice is a potential cause of equine AAD. Other risk factors, such as opportunistic enteropathogens, may play a part in the development of diarrhoea secondary to antimicrobial usage. POTENTIAL RELEVANCE: Although the risk of equine AAD is low, this sequela of antimicrobial treatment is possible especially when opportunistic enteropathogens or other risk factors are present. Because drugs from any antimicrobial class can be potentially involved in AAD, clinicians have additional incentive to ensure the judicious use of antimicrobial agents.

Abnormalities in lung surfactant in horses clinically affected with recurrent airway obstruction (RAO).

BACKGROUND: Abnormalities in lung surfactant are well described in human respiratory diseases including asthma, but are poorly described in horses. HYPOTHESIS: Lung surfactant is abnormal in horses with clinical signs of recurrent airway obstruction (RAO). ANIMALS: Six healthy horses and 5 horses with RAO. METHODS: Bronchoalveolar lavage fluid (BALF) was obtained from all horses by standard procedures. Cell-free BALF was separated into crude surfactant pellets (CSP) and supernatant via ultracentrifugation. Phospholipid and protein content was analyzed from both of these fractions. Phospholipid composition of CSP was determined using high-performance liquid chromatography with an evaporative light scatter detector. Surface tension of CSP was measured with a pulsating bubble surfactometer. RESULTS: Compared with healthy horses, surfactant from RAO-affected horses was characterized by significantly decreased phospholipid content in total surfactant (median; range: 23.2; 14.7-62.2 microg/mL BALF versus 172; 111-267 microg/mL BALF, P = .0062) and CSP (20.2; 6.4-48.9 microL/mL BALF versus 155; 94.4-248 microg/mL BALF, P = .0062), and a significantly lower percentage of phosphatidylglycerol (PG) (4.5; 3.6-5.6% versus 6.6; 4.1-7.6%, P = .028). Furthermore, the ratio between the percentages of phosphatidylcholine and PG was significantly higher in RAO-affected horses than in healthy horses (20.9; 16.6: 25.9 versus 13.9; 11.8-22.8, P = .045). CONCLUSIONS AND CLINICAL IMPORTANCE: This study demonstrates that surfactant from RAO-affected horses is abnormal. Further studies are needed to determine if these abnormalities are related to an increased tendency for bronchoconstriction and to a decreased ability to clear airway mucus in RAO-affected horses.

Sedative effects of medetomidine and its reversal by atipamezole in llamas.

OBJECTIVE: To determine a dose of medetomidine that will induce sedation in llamas, to assess effects of medetomidine sedation on arterial blood gas variables, and to determine efficacy of atipamezole in reversing medetomidine-induced sedation. DESIGN: Prospective, randomized clinical trial. ANIMALS: 15 clinically normal adult llamas. PROCEDURE: 9 llamas received various doses of medetomidine (0.01, 0.02, or 0.03 mg/kg [0.005, 0.009, or 0.014 mg/lb] of body weight, i.m.). Heart and respiratory rates and sedative effects were recorded. Using the lowest dose that induced deep sedation, 6 different llamas were used to assess effects of medetomidine on arterial blood gas variables. These same 6 llamas were later given atipamezole (0.125 mg/kg [0.057 mg/lb], i.v.) 30 minutes after medetomidine injection. Heart and respiratory rates, sedative effects, and time from atipamezole injection to standing were recorded. RESULTS: Sedation began 6.67 +/- 1.15 minutes (mean +/- SD) after medetomidine administration (0.03 mg/kg, i.m.). Arterial blood gas variables measured 30 and 60 minutes after injection were not different from baseline. Llamas that did not receive atipamezole remained recumbent for 91.50 +/- 24.68 minutes. After atipamezole administration, llamas were able to stand in 5.80 +/- 3.27 minutes. CLINICAL IMPLICATIONS: Medetomidine induced light to deep sedation in a dose-dependent manner in clinically normal llamas. A dose of 0.03 mg/kg induced deep sedation with a short period of analgesia. Atipamezole rapidly reversed effects of medetomidine, and llamas recovered quickly and were soon able to stand.