Summary The medical records of 192 horses with septic arthritis/tenosynovitis 1979–1989 were reviewed. Forty‐three horses developed infection after an intra‐articular injection, 46 following a penetrating wound, 25 following surgery, 66 were foals less than 6 months old, and 12 were adult horses without a known aetiology. Haematogenous infection of a joint occurs in adult horses and should be considered as a differential diagnosis in horses with an acute onset of severe lameness. The aetiology of the infection had a significant effect on the type of bacteria identified by culture. Staphylococcus was cultured from most of the horses that developed infection following a joint injection or surgery, 69% of the horses from which an organism was identified. Horses that developed infection secondary to a penetrating wound frequently provided cultures of more than one organism; Enterobacteriaceae and anaerobes were more frequently isolated in this group. The most common organisms isolated from foals were Enterobacteriaceae; E. coli was identified in more than 27% of the foals. The hock was the most frequently involved joint. Multiple treatments were used over the 10‐year period of study. Survival rates were lowest in foals; only 45% survived to be released from the hospital. Survival was greater in adult horses; 85% of the horses that were treated were released from the hospital. Survival was significantly greater in horses with septic tenosynovitis; all 14 of the horses that were treated survived. Survival was not significantly affected by the joint involved or by the type of bacteria cultured from the synovial fluid. Follow‐up racing data were obtained for all horses of racing age that were released from the hospital; 56.5% of these horses returned to racing and over 45% of these horses were able to make at least 5 starts. We suggest that if the infection can be eliminated before irreversible damage to the articular cartilage occurs, horses can return to athletic function.

Background: Equine herpesvirus type 1 (EHV-1) infection causes neurologic disease in horses. However, risk factors for the disease and long-term prognosis are poorly characterized.Hypothesis: There are identifiable risk factors for equine herpes-1 myeloencephalopathy. Animals: The entire population of 135 horses housed within the equestrian facility. Methods: A descriptive study investigated the clinical, serologic, virologic, and management aspects of an outbreak of EHV-1 myeloencephalopathy.Results: Out of 135 horses at the facility, 117 displayed signs of EHV-1 infection. Forty-six horses developed neurologic deficits characterized by symmetrical hind limb ataxia and weakness. Twelve horses that developed neurologic deficits became recumbent and did not survive. The development of severe neurologic deficits during the outbreak was associated with the presence of residual deficits at the 6-month examination. Within 1 year of the outbreak onset, all horses that survived had returned to an exercise level comparable to that experienced before the outbreak. Factors associated with the development of neurologic disease included age of .5 years, location in the south or arena stall areas, and highest rectal temperature on day 3 or later of the febrile period.Conclusions and clinical importance: Being .5 years of age, having had a rectal temperature of .103.5uF, and highest rectal temperature occurring on or after the 3rd day of the febrile period were the factors most predictive of the development of neurologic disease and death. Data obtained during this outbreak substantiate previous findings relating to clinical aspects and diagnosis of EHV-1 myeloencephalopathy. The prophylactic and therapeutic use of acyclovir during this outbreak is described.

Background: Sepsis is an important cause for neonatal foal mortality. The hypothalamic-pituitary-adrenal axis (HPAA) responses to sepsis are well documented in critically ill humans, but limited data exist in foals. The purpose of this study was to evaluate the HPAA response to sepsis in foals, and to associate these endocrine changes with survival.Hypothesis: Blood concentrations of arginine vasopressin (AVP), adrenocorticotropin hormone (ACTH), and cortisol will be higher in septic foals as compared with sick nonseptic and healthy foals. The magnitude of increase in hormone concentration will be negatively associated with survival.Animals: Fifty-one septic, 29 sick nonseptic, and 31 healthy foals of 7 days of age were included. Methods: Blood was collected at admission for analysis. Foals with positive blood culture or sepsis score !14 were considered septic. Foals admitted with disease other than sepsis and healthy foals were used as controls. AVP, ACTH, and cortisol concentrations were measured using validated immunoassays.Results: AVP, ACTH, and cortisol concentrations were increased in septic foals. Septic nonsurvivor foals (n 5 26/51) had higher plasma ACTH and AVP concentrations than did survivors (n 5 25/51). Some septic foals had normal or low cortisol concentrations despite increased ACTH, suggesting relative adrenal insufficiency. AVP, ACTH, and cortisol concentrations were higher in sick nonseptic foals compared with healthy foals.Conclusions and Clinical Importance: Increased plasma AVP and ACTH concentrations in septic foals were associated with mortality. Several septic foals had increased AVP : ACTH and ACTH : cortisol ratios, which indicates relative adenohypophyseal and adrenal insufficiency.

Summary Bacterial culture and susceptibility results were analysed from 233 horses with septic arthritis/tenosynovitis or osteomyelitis that developed after fracture repair. Antibiotics were deemed highly effective, effective or ineffective if ≤85%, 70–84.9% or <70% of the isolates were susceptible respectively. In total, 424 bacterial types were isolated; 386 were aerobic or facultative and 38 were anaerobic. Enterobacteriaceae (28.8%) were the most common bacterial group isolated, followed by non‐beta‐haemolytic streptococci (13.0%), coagulase‐positive staphylococci (11.8%), beta‐haemolytic streptococci (9.4%), and coagulase‐negative staphylococci (73%). The remainder of the organisms were other Gram‐negative (15.8%), other Gram‐positive (2.3%) and miscellaneous (2.6%) bacteria. Penicillin and ampicillin were highly effective against beta‐haemolytic streptococci, but were ineffective against other bacteria. Ampicillin was no more effective than penicillin against most bacteria. Amikacin was the most effective antibiotic against the wide range of bacteria isolated in this study. Amikacin was highly effective against coagulase‐positive staphylococci, Enterobacteriaceae and Pseudomonas and was effective against coagulase‐negative staphylococci and Actinobacillus. Gentamycin was not highly effective against any bacterial group; but was effective against coagulase‐positive and negative staphylococci, Pseudomonas, Salmonella and Actinobacillus. Kanamycin was ineffective against all bacteria with the exception of Actinobacillus. Cephalothin was highly effective against beta‐haemolytic streptococci, coagulase‐positive staphylococci and Actinobacillus and was effective against coagulase‐negative staphylococci. Cephalothin is a very useful antibiotic for Gram‐positive organisms, especially staphylococci, which are an important cause of iatrogenic infections. Trimethroprim‐sulphonamides were highly effective against Actinobacillus and were effective against coagulase‐positive staphylococci, beta‐haemolytic streptococci, non‐beta‐haemolytic streptococci and Rhodococcus equi. Due to the narrow spectrum of activity of trimethoprim‐sulphonamides against the common pathogenic organisms, these drugs should be used only after culture and susceptibility results are known. Erythromycin was highly effective against coagulase‐positive staphylococci, beta‐haemolytic streptococci and Rhodococcus equi and was effective against coagulase‐negative staphylococci. Chloramphenicol was effective against a wide range of organisms, but it cannot be recommended because of the human health hazard associated with handling this drug. Other less commonly used antibiotics were effective against some types of bacteria. The combination of a cephalosporin and amikacin provides the best coverage against the bacteria isolated in this study. These are the antibiotics that should be considered when treating horses with musculoskeletal infection before culture and susceptibility results are known. However, these drugs are not recommended for prophylaxis in ...