Antibiotic prophylaxis of lower respiratory tract contamination in horses confined with head elevation for 24 or 48 hours

The efficacy of N-acetylcysteine in decreasing airway inflammation and mucus accumulation in horses with 18 hours of head confinement

BACKGROUND

During transportation many horses develop post-transportation infection, which can be life-threatening and end their sport career. Preventing mucus accumulation and inflammation during transportation is vital, emphasizing the need for effective strategies to enhance overall horse health welfare.

OBJECTIVES

Assess the impact of N-acetylcysteine (NAC) on mucus accumulation and inflammation in horses subjected to 18 hours of head confinement.

ANIMALS

Six healthy crossbred horses, 5.3 ± 2.1 years of age and weighing 387 ± 30 kg.

METHODS

Prospective placebo-controlled cross-over design study. The horses' heads were restrained in their stalls for a period of 18 hours. They were studied under 4 conditions: Not confined (NC): before head confinement, placebo (P), and confined head (CH): 18 hours of head confinement without treatment, and N-Acetylcysteine (NAC): 18 hours of head confinement treated with NAC before confinement (15 mg/kg/day NAC PO for 3 days). Bronchoalveolar lavage (BAL) was performed in each condition. Mucus accumulation along the trachea was evaluated by endoscopy.

RESULTS

Endoscopic scores were significantly different between CH and other conditions, whereas no significant differences were found among NC, P, and NAC. The BAL cell count (34 291 ± 2624 cells/μL), neutrophil and lymphocyte count (18 601 ± 3193 cells/μL and 3337.4 ± 593 cells/μL, respectively) in CH were significantly higher compared to NAC. Neutrophil percentage was significantly higher in CH (53.8 ± 8%) compared to horses that received NAC (20.08 ± 8%). Conversely, in comparison to NAC (66.33 ± 9%), the percentage of macrophages was significantly lower in CH (35.7 ± 10%).

CONCLUSIONS

N-acetylcysteine was found to significantly decrease mucus accumulation and inflammatory cell counts in horses with head confinement.

Effects of a single dose of enrofloxacin on body temperature and tracheobronchial neutrophil count in healthy Thoroughbreds premedicated with interferon-α and undergoing long-distance transportation

OBJECTIVE

To evaluate effects of a single dose of enrofloxacin (5 mg/kg, IV) on body temperature and tracheobronchial neutrophil count in healthy Thoroughbreds premedicated with interferon-α and undergoing long-distance transportation.

ANIMALS

32 healthy Thoroughbreds.

PROCEDURES

All horses received interferon-α (0.5 U/kg, sublingually, q 24 h) as an immunologic stimulant for 2 days before transportation and on the day of transportation. Horses were randomly assigned to receive enrofloxacin (5 mg/kg, IV, once; enrofloxacin group) or saline (0.9% NaCl) solution (50 mL, IV, once; control group) ≤ 1 hour before being transported 1,210 km via commercial vans (duration, approx 26 hours). Before and after transportation, clinical examination, measurement of temperature per rectum, and hematologic analysis were performed for all horses; a tracheobronchial aspirate was collected for neutrophil quantification in 12 horses (6/group). Horses received antimicrobial treatment after transportation if deemed necessary by the attending clinician.

RESULTS

No adverse effects were associated with treatment. After transportation, WBC count and serum amyloid A concentration in peripheral blood samples and neutrophil counts in tracheobronchial aspirates were significantly lower in horses of the enrofloxacin group than in untreated control horses. Fever (rectal temperature, ≥ 38.5°C) after transportation was detected in 3 of 16 enrofloxacin group horses and 9 of 16 control horses; additional antimicrobial treatment was required in 2 horses in the enrofloxacin group and 7 horses in the control group.

CONCLUSIONS AND CLINICAL RELEVANCE

In horses premedicated with interferon-α, enrofloxacin appeared to provide better protection against fever and lower respiratory tract inflammation than did saline solution.

Towards an understanding of equine pleuropneumonia: factors relevant for control

OBJECTIVE

To review relevant literature on factors associated with the development of equine pleuropneumonia.

DESIGN

A review of the literature using a range of databases including Current Contents, Medline, ChemAbstracts, Biological Abstracts and CAB and a comprehensive search strategy which involved use of keywords, author and subject category searches. Additional sources included review of articles cited by key accumulated references.

RESULTS

Since the early years of this century, many of the "gaps" in our knowledge of the pathogenesis of this disease have been filled. We now know that equine pleuropneumonia results from contamination of the lower respiratory tract with bacteria similar to the normal oropharyngeal microbiota of the horse and that transportation of any mode, especially over long distances (and consequently with no or short rest periods), is the single most important predisposing factor for this disease. This is associated with restraint of horses such that they are unable to lower their heads, which leads to increased opportunity for lower respiratory tract contamination and a reduced opportunity for clearance. Strenuous exercise also results in lower respiratory tract contamination and exercise subsequent to transportation exerts additive detrimental effects on the defenses of the lower respiratory tract.

CLINICAL IMPLICATIONS

While modern veterinary medicine and surgery have significantly reduced the death rate from pleuropneumonia, horses that develop the disease have a high probability of not returning to their prior use. This underscores the importance of developing the most effective strategies for its prevention.