Stress Response with Laminitis

Researchers at Colorado State University conducted a prospective hospital-based study to examine stress hormone profiles including thyroid hormone, adrenocorticotrophic hormone (ACTH), cortisol and histamine in 14 horses that presented with laminitis compared with a group of 12 horses affected by gastrointestinal (GI) disease and a group of 12 controls at the hospital for non-medical reasons such as prepurchase examination or dental work. Among the laminitis cases, nine were chronic and five were acute without a prior history of the condition. The GI disease group included nine surgical colic cases and three horses with colitis.

Stress hormone levels for horses with laminitis and GI disease were different from the controls, but not in a uniform, consistent manner. ACTH was higher in laminitis and GI groups compared with controls. Thyroid hormone was lower and cortisol was higher in GI horses compared with both laminitis and control horses. Histamine was significantly higher in horses with laminitis compared with GI horses and controls.

The authors conclude although the stress hormone profiles of horses with laminitis were variably different from the nonlaminitic horses examined in this study, stress hormone profiles may warrant further investigation as potential biomarkers for horses at risk for laminitis. Examining histamine levels over time may be particularly useful as a biomarker for laminitis.

— Moss A et al. J of Vet Sci 2023:e33

Sarapin Block Found Ineffective

Perineural injections of Sarapin, an extract of the pitcher plant, are promoted as a long-term nerve block to relieve lameness in the foot and lower limb such as that caused by navicular disease. This experimental study on five horses with chronic lower limb lameness examined the effects of a sesamoid nerve block using Sarapin to relieve lameness. The lameness had been confirmed to respond to a nerve block with mepivacaine, a short-acting anesthetic commonly used to diagnose lameness, before the experiment.

Using inertial sensors and a computerized gait analysis system, the horses were evaluated for lameness for 30 minutes and then three, seven, 14 and 21 days following the treatment. At 30 minutes, all the horses responded to the diagnostic nerve block. However, the Sarapin treatment had no significant effect on the lameness scores at any time. The authors concluded that Sarapin has no value for relieving lower limb lameness when injected as a regional nerve block.

— Livesey L et al. JEVS 2024:104974

A Review of Pastern Dermatitis

Commonly known as scratches, mud fever, grease heel, or dew poisoning; equine pastern dermatitis (EPD) is a common but challenging skin condition that affects the palmar/plantar pastern of light and heavy horses. More severe and sometimes proliferative forms can affect the entire circumference of the pasterns. This review, conducted by veterinarians in Switzerland and Germany, examined dozens of sources including historical accounts and peer-reviewed literature.

EPD becomes more common with age. Male horses, areas of unpigmented skin and the hind limbs seem to be more commonly affected. EPD, including more severe forms, is more common among draft horses. This is attributed to the longer hair or “feathers” on their lower limbs, but a genetic component has also been implicated. Unfortunately, there is no simple genetic pattern or test to identify animals with this predisposition. Surprisingly, although commonly thought to exacerbate the problem, rainfall and wet or muddy environmental conditions are not always associated with the condition.

Fungal infections have not been identified as an important factor in EPD; however, bacterial infections with various ubiquitous pathogens including staph, strep and occasional gram-negative organisms are common. Chorioptes mites are associated with some EPD, particularly in draft breeds, but while topical antiparasite treatments lessen the pain and itching associated with the condition there is rarely full resolution of the clinical signs. Topical antibiotics, corticosteroids, antibacterial compounds, fatty acid compounds, moisturizers and astringents as well as systemic antibiotics for more severe cases are all used with variable efficacy. The best approach is for early intervention and diagnostics including skin scrapings and biopsies for more serious cases to inform specific treatments.

—  Gerber V et al. JAVMA 2023;261:S58-S65

HA or PRP Following Arthroscopy

Intra-articular hyaluronic acid (HA) and platelet-rich plasma (PRP) injections are frequently given after arthroscopic surgery for osteochondrosis (OCD). This controlled experiment, conducted in Brazil, examined and compared the efficacy of these treatments to improve healing following surgical treatment for OCD of the distal tibia in the hock.

Eighteen Brazilian sport horses were included in the study with six each receiving HA, PRP, or lactated Ringer’s (LRS, a solution similar to saline) as a control treatment given 10 days after arthroscopic surgery to remove fragments and debride OCD lesions of the distal tibia. Follow-up examinations including clinical examination as well as X-rays, ultrasound and synovial fluid evaluation were performed at the time of surgery and after 10, 30 and 60 days.

All the operated horses had thickening of the joint capsule 30 days after surgery. Flexion tests improved 30 and 60 days after surgery for the LRS-treated controls. Flexion tests for horses treated with PRP were worse during this time. Both the HA and PRP groups had increased joint effusion, and the HA horses had increased white blood cells compared with the controls. The authors concluded neither HA nor PRP given post-operatively improved recovery following arthroscopy for OCD of the hock.

— Pereira MF et al. Vet Anim Sci 2024:100330