Muscle Diseases of Ruminants Flashcards
How does clostridial myositis present?
BLACK LEG = subcutaneous emphysema
MALIGNANT EDEMA = leg is cold to the touch, swollen, and edematous
What are the 4 causative agents of clostridial myositis?
- Clostridium chauvoei = black leg
- C. septicum = malignant edema
- C. novyi = black disease
- C. sordellii = sord
How do cattle become infected with clostridium?
exist as spores worldwide in the soil and manure and can be ingested via grazing or infect wounds
- macrophages engulf spores and bring them to tissues, where they will release toxins when an anaerobic environment develops
What causes clostridial myositis signs following infection?
ANAEROBIC ENVIRONMENTS - bruising from fighting
What ages of cattle are most commonly affected by clostridial myositis?
YOUNG and WELL-MUSCLED —> < 2 y/o, especially black leg (emphysema)
- suspected due to larger muscle mass
Is it likely for this cattle to be affected by clostridial myositis?
no
- not a good doer
What is indicative of classing black leg in cattle?
SQ emphysema - C. chauvoei
+/- sudden onset of death
What are the chances these calves died of black leg?
unlikely - laying together near a tree, outbreaks uncommon —> lightning?
How are cattle diagnosed with clostridial myositis antemortem and postmortem?
based on clinical signs
- impression smears with large G+ rods
- areas of black muscle necrosis that smell of rancid butter
- culture and sensitivity of aspirates of affected tissue
- PCR
What is the drug of choice for treating black leg? What 3 additional treatments are considered?
high dose of procaine penicillin G —> systemic + local
- NSAIDs for pain and inflammation
- skin incisions to oxygenate the area
- humane euthanasia - slaughter not an option, need to prevent further cases rather than save one
What 2 populations should be vaccinated for black leg? What population is this not necessary in?
- pregnant cows 1-2 months from calving
- calves less than 2 years (can have maternal Abs up to 6 months)
older cattle > 2 y/o —> immunity due to exposure
How long does it take for the black leg vaccine to provide protection? What else can be done to protect young stock while waiting for vaccine protection?
2 weeks
prophylactic antibiotic treatments (PPG)
Is routine vaccination of herds for black leg economical? Is one sufficient?
YES —> only need to vaccinate susceptible populations
unlikely, recommended vaccinate 2 times a year
What time of year is associated with higher chances of clostridial myositis development?
late summer to early winter
How should bodies be properly handled following death from clostridial myositis?
burned or buried deep and covered with lime
- filled with clostridium spores that can contaminate the pasture
What is clostridial myositis prognosis like?
guarded to grave —> even if animal survives, it can be permanently disabled
What is a common development in downer cows? How does this develop?
crush syndrome
increased intramuscular pressure and muscle swelling blocks drainage of venous blood from muscles, leading to ischemic necrosis (hopeless prognosis at this point)
How is crush syndrome relieved? What can be seen on necropsy?
get downer off of the muscles —> float tank, hip lift, sling, rolling (can be used to diagnose any neurologic disease)
blackened necrotic muscle
What is the most common cause of nutritional myodegeneration in cattle? What 2 syndromes develop?
white muscle disease = dietary deficiency of selenium and/or vitamin E
- cardiac - sudden onset, death
- skeletal
How does the skeletal form of white muscle disease compare to the cardiac form? How do these animals present?
slower onset of muscle weakness, stiffness, and trembling in limbs
- swollen, hard, painful muscles of front and hindlimbs
- recumbency, unable to stand
- respiratory distress with increased abdominal effort due to DIAPHRAGM and INTERCOSTAL muscle involvement
What are 3 signs of white muscle disease on clinical pathology? What is highly suggestive?
- elevated SCPK (CK) to the 1000s
- low whole blood selenium levels
- low glutathione peroxidase
history of typical clinical signs and lack of supplementation
Where in the US is white muscle disease most common?
COASTAL STATES and river bottom pastures —> selenium is leeched into the water from the soil
- most common in calves 2-4 months of age (young and rapidly growing!) during the spring and summer months
What form of white muscle disease is amendable to treatment? What treatment is recommended?
skeletal
selenium products —> BO-SE (1 mg/kg in calves), MU-SE (5 mg/mL in adults)
What is able to block selenium uptake?
sulfur blocks its uptake into the forage on pasture cows would be getting it from
How is white muscle disease prevented, especially in selenium-deficient areas?
availability of selenium mineral content to herd all year round
- intraluminal bolus
- long-term selenium injections are labor-intensive
How do cattle present with bilateral ruptures gastrocnemius?
plantigrade (dropped) hock with no weight bearing —> when hock is pulled on exam, stifle will not move
- hopeless prognosis
What is indicative of peroneus tertius rupture in cattle? What is the most common cause of this?
- skidding/dragging of hindleg causes irregular wearing on the claws on the top
- no resistance to pulling on legs
roping injury - yanking on leg
What causes gossypol toxicosis? In what large animals is this most common?
infection of cottonseed feed (common protein)
swine (can affect cows!)
What are the 2 major signs of gossypol toxicosis? What can be protective?
- cardiotoxic - diffusely pale, flaccid, dilated chambers
- multifocal myocardial and skeletal muscle necrosis
iron
What are the major differentials for gossypol toxicosis?
- monensin
- selenium/vitamin E deficiency
In what animals is doubling muscle (muscular hypertrophy) common? What does it commonly lead to?
- Belgian Blue cattle
- Piedmontese cattle
- pigs
myostatin gene mutation
