W4: Equine Ambulatory rotation

Happy 2021 folks! Apologies for the long hiatus, no excuses (ok maybe I was a bit busy balancing vet work while attending the Part Time YouTuber Academy course by Ali Abdaal (link to his course here) , so I have been more consistent with posting vet school content on YouTube! Video attached at the bottom of post!)

This post will be a brief overview of the equine ambulatory rotation and common clinical conditions that we observed whilst on rotation.

Overview:

It was a 2-week long rotation which involved us students driving to calls located within a 30 minute radius from the vet school to observe first opinion clinical work. As there weren’t any students on the Equine Hospital rotation week, we got to observe some cool procedures at the equine hospital as well, which was really nice. Whenever we had down time or an early finish from ambulatory calls, the clinicians would discuss some cases with us or showed us radiographs to talk through a lameness work up etc. We were also given some powerpoint case studies to work through during the week to keep us busy.

Routine first-opinion equine work consists of vaccinations (tetanus and equine influenza), dental work, 2-stage or 5-stage pre-purchase examinations (vettings), lameness evaluation, colic work ups and wound management.

For vaccinations, we administer them intramuscularly (IM) usually in the neck, but other sites include the pectoral muscles and gluteal muscles. To locate the injection site on the neck, you place one hand cranial to the scapula, one hand below the nuchal ligament and avoid the S-shaped cervical vertebrae on the horse (to form a triangular area). However, if the horse has a known history of reacting to the vaccine resulting in myositis (stiff muscles), we are advised to avoid the neck as the horse would struggle to lower their head to eat and drink, instead you would administer the vaccine in the pectoral muscles.

image source: https://www.rvc.ac.uk/equine-vet/information-and-advice/fact-files/intra-muscular-injections-in-horses

For dental work it is useful to revise the dental formula of the horse and familiarise yourself with the equine teeth numbering system. It is numbered 1-2-3-4 from the right maxilla -> left maxilla -> left mandible -> right mandible. (Eg. the wolf tooth in the upper right arcade is numbered 105, first pre-molar on the left mandible is 306.) In the past, wild horses grazed on rough grasses so their teeth were worn more evenly. However, the domestication of horses have led them to graze softer, lush grasses and concentrates, reducing the amount of natural wear. Horses also have a wider upper jaw and narrower lower jaw, hence the shearing forces often lead them to have sharper edges on the outer-side of the upper arcade and on the inner-side of the lower arcade. This can cause their tongue and cheek to get caught and may lead to ulcers. This is where dental work comes in! We rasp the teeth edges down as well as conduct a thorough dental examination to check for any abscesses or impactions. This is commonly done under sedation (detomidine or xylazine in combination with butorphanol) for the patient and vet safety.

Image source: Google
List of dental equipment

Pre-purchase examinations (‘vettings’) are conducted when a buyer is interested in buying a horse from a vendor. The vet conducts a thorough clinical exam, inspects the documentation, obtains a blood sample to screen for any abnormalities and works the horse (trot up, lunge) depending on the stage of vetting (2- stage or 5-stage) and reports back to the buyer whether it is suitable for their intended use (hacking, dressage, racing).

An interesting case we saw involved a swelling of the hock joint (tarsus) on the horse. Prior to this, I did not know that there were a variety of disorders involving the tarsus of the horse.

In brief, an explanation of each one

  • Bog spavin -> inflammation of the synovial membrane of the hock joint resulting in excess fluid in the joint. Corticosteroids may provide short term relief or surgical removal of fluid with an endoscope could be performed.
  • Bone spavin -> osteoarthritis of the joint, often causes lameness. Corticosteroids and NSAIDs may minimise or eliminate signs
  • Curb -> thickening or bowing of the plantar tarsal ligament that runs down the back of the hock. Usually caused by a strain as the ligament becomes inflamed and thickened after falling, slipping, jumping or pulling injury. In acute cases, manage with cold packing and rest.
  • Capped hock -> distension of the calcaneal bursa
  • Thoroughpin -> tenosynovitis of the tarsal sheath. Tarsal sheath is the synovial sheath of the lateral digital flexor tendon at the level of the hock (tendon sheath of the DDFT). Could be of idiopathic cause or due to direct trauma. Treatment depends on the underlying cause and could include rest, systemic/ local anti-inflammatory drugs, cold therapy. Intrathecal medication with hyaluronan and/or corticosteroids may be useful in severe cases. If infectious, may need to lavage tarsal sheath and provide antibiotic therapy. One way to distinguish thoroughpin from bog spavin is that you would expect to see fluid filled swellings on both sides ABOVE the tarsal joint in thoroughpin.

Other topics that we discussed during the rotation include:

  • laminitis -> worked through radiographic findings and treatment options
  • PPID (a.k.a. equine cushings)
  • EMS equine metabolic syndrome

If you’d like to see what we got up to, here is a vlog of the 2 weeks! 😀 Enjoy and as always, stay safe and take care 🌻!

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