Thursday, September 8, 2016


This 4-part series on the top 20 equine conditions will set you up for NAVLE® success.


Missed part 1? Find it here

Missed part 2? Find it here


5 More of Zuku’s top 20 equine conditions to know for NAVLE® success:

  1. Gastrointestinal parasitism
    • Classic case: Depends on type of parasite, but often weight loss, ill thrift, poor coat
      • Cyathostomes (small strongyles) – diarrhea, weight loss, colic
      • Large strongyles (Strongylus vulgaris) & tapeworms (Anoplocephala perfoliata) – colic
      • Roundworms (Parascaris equorum) – weight loss, colic, and—in foals—pneumonia
    • Dx: Fecal egg count
    • Rx: Use manure removal and pasture rotation!
      • Encysted cyathostome larvae – fenbendazole (2x dose for 5 d) or moxidectin
      • Large strongyles – adults susceptible to most anthelmintics; larvae to macrocyclic lactones
      • Tapeworms – praziquantel or 2x pyrantel
      • Roundworms – most anthelmintics work
    • Pearls:
      • Cyathostomes
        • Emerge in favorable climate conditions (wet and not too hot or too cold)
        • Cause damage to large intestinal wall and colitis
        • Currently biggest parasite of concern
      • Large strongyles
        • Larvae migrate through cranial mesenteric artery causing arteritis & loss of blood supply to large intestine
        • Cause nonstrangulating infarctive colic
      • Tapeworms
        • Attach at ileocecal junction
        • Cause damage, perforation, & motility disturbances
      • Roundworms
        • Large adult worm burden in small intestine leads to impaction
        • See clinical signs after deworming!

  2. Skin tumors
    • Classic case: 3 most common are:
      • Sarcoid
        • Raised spherical lumps (“nodular”)
        • Hairless areas w/ thinned skin (“occult”)
        • Warty & scaly (“verrucous”); hemorrhagic & ulcerated (“fibroblastic”)
        • Malevolent/malignant
        • Mixed (most common!)
      • Squamous cell carcinoma (SCC)
        • Thickened, reddened, & ulcerated areas
        • On non-pigmented skin of the face and eyes, penis, and perineal area
      • Melanoma
        • Gray horse over 10 years old
        • Black nodules under tail, at perineum, lips, prepuce, eyelids, parotid salivary glands, & guttural pouches
    • Dx:
      • Sarcoid – excisional biopsy (incomplete surgical removal can trigger more aggressive behavior of the lesion!)
      • SCC – excisional biopsy
      • Melanoma – clinical appearance or fine needle aspirate
    • Rx:
      • Surgical excision +/- cryotherapy, local chemotherapy (cisplatin, 5-fluorouracil), laser therapy
      • Immunotherapy for sarcoids
      • Radiation therapy for SCC
      • Cimetidine for melanomas
    • Pearls:
      • Sarcoid suspected due to bovine papillomavirus and spread by flies; guarded prognosis due to recurrence
      • SCC due to chronic irritation or UV exposure; often recurs but rarely metastasizes
      • Melanomas may become locally aggressive or [uncommonly] metastasize in grays; malignant melanoma more common in non-gray horses

  3. Equine viral encephalitis

                    Horse in sling with encephalomyelitis

    • Classic case: Altered mentation, cranial nerve signs, ataxia, paresis/paralysis
      • West Nile virus (WNV) – also has fever, fasciculations of face & neck, hyperesthesia, colic
    • Dx:
      • 4 Main etiologies:
        • WNV – throughout US and Canada
        • Eastern encephalitis virus – mortality 50-90%
        • Western encephalitis virus – less pathogenic and currently less active than others
        • Venezuelan encephalitis virus – mortality 50-75% and horses are NOT dead-end hosts (vs. they ARE for the other 3)
      • Cerebrospinal fluid analysis (for all)
      • IgM capture ELISA (for WNV)
    • Rx:
      • Supportive care
      • Prevent – vaccinate and minimize mosquito exposure
    • Pearls:
      • Poor prognosis if animal is recumbent
      • Rabies always on the list! – so handle all horses with encephalitic signs as if they have zoonotic disease

  4. Equine infectious anemia

                    Petechiation of the oral mucosa in equine infectious anemia

    • Classic case: Inapparent carrier is most common; also…
      • Acute – fever, lethargy, thrombocytopenia
      • Chronic – recurrent fever with anemia, weight loss, ventral edema, petechia
    • Dx:
      • Etiology: Lentivirus
      • Coggins test – AGID (gold standard, takes 24 h)
      • -or-
      • c-ELISA (takes 1 h, but more false positives)
      • Testing must be performed at US Department of Agriculture (USDA)-approved lab & submitted by licensed & federally accredited veterinarian
    • Rx: None; seropositive horses must either be:
      • In lifelong quarantine at least 200 yards from other horses
      • -or-
      • Euthanized
    • Pearls:
      • Lentivirus causes life-long infection
      • In the US, all horses moved interstate or sold within a state must have been tested negative for EIA at least within the last 12 months

  5. Severe lameness
    Equine infectious anemia
    • Classic acute case:
      • Lame at a walk or nonweight-bearing (4/5 to 5/5 lame on AAEP lameness scale) in 1 limb
      • 4 most common causes are –
        • Foot abscess – increased digital pulse, sensitive to hoof testers
        • Septic joint or tendon sheath – effusion of joint or tendon sheath
        • Cellulitis/lymphangitis – entire limb is swollen & hot, + fever
        • Fracture/suspensory apparatus breakdown injury – more focally swollen limb, no fever
    • Dx:
      • Foot abscess – hoof tester positive, maybe can locate abscess pocket with hoof knife
      • Septic synovial structure - synovial fluid has increased protein, neutrophils, and lactate
      • Cellulitis/lymphangitis - ultrasound, Dx of exclusion
      • Fracture – radiographs
      • Breakdown injury – ultrasound shows soft tissue injury
    • Rx:
      • Foot abscess – paring, poultice, +/- NSAIDs
      • Septic synovial structure – lavage, systemic and intrasynovial antimicrobials, NSAIDs
      • Cellulitis/lymphangitis - antimicrobials, anti-inflammatories (NSAIDs and/or steroids), bandaging, cryotherapy
      • Fracture/breakdown injury – emergency stabilization with splint/bandage; surgical repair for fracture
    • Pearls:
      • Prognosis for foot abscess is good
      • Prognosis for septic synovial structure depends on what structure is affected and how quickly and aggressively Rx’d
      • Prognosis for cellulitis/lymphangitis is guarded depending on whether acute or chronic, and how quickly and aggressively Rx’d
      • Prognosis for fracture/breakdown injury depends on location of injury, whether open or closed, degree of soft tissue injury & displacement

owl    Zuku-certified bodacious websites on equine conditions:

Skin tumors in horses

Great review with pictures and therapies.

Courtesy of the American College of Veterinary Surgeons.

  Equine Parasite Control Guidelines

The in-depth industry recommendations.

Courtesy of the AAEP.

EIA factsheets and distribution maps

Everything you wanted to know about EIA.

Courtesy of the Center for Food Security & Public Health and Iowa State University.

Eastern, Western, and Venezuelan equine encephalomyelitis

Broad-level info about these diseases and their human impacts.

Courtesy of Iowa State University.

Alternative therapies for cellulitis

Great overview of cellulitis and its therapies.

Courtesy of the American College of Veterinary Surgeons, written by Dr. Liberty Getman.


Example of NAVLE®-format equine question:

What is the advantage of the c-ELISA test for Equine Infectious Anemia over the Coggins (AGID) test?

   A. More specific-fewer false positives

   B. Faster-can be done in one hour

   C. Accepted in all U.S. states

   D. Can be done on saliva, serum or CSF

   E. Detects surface glycoproteins specific to EIA

Click here for the answer and explanatory text…




Images courtesy of Böhringer Friedrich (Haflinger Jungtier), eXtensionHorses (roundworms), Dr. Britta Leise (sarcoid), Dr. Cynthia Powell (squamous cell carcinoma), Dr. Stephanie Brault (horse in sling), Dr. Erwin Pearson (petechia), Immanuel Giel (horses grazing).