L16: Muscle Diseases Of Ruminants (Mallicote)

Question 1

Inflammatory muscular diseases

Answer 1

Clostridial myositis
Protozoal infection (Sarcocystis)

Question 2

Etiology of clostridial myositis

Answer 2

• anaerobic, spore-forming bacteria
• requires CREATION OF anaerobic conditions**
• initial entry routes: inoculation or ingestion of spores

Question 3

Organism that causes blackleg

Answer 3

Clostridium chauvoei

Question 4

Organism that causes gas gangrene

Answer 4

C. Perfringens

Question 5

Risk factors for clostridial myositis

Answer 5

• may occur repeatedly at same locale
• C. Chauvoei assoc. with warmer months
• C. Sordelli assoc. with older feedlot cattle
• wound infections: C. Perfringens, C. Septicum, C. Novyi
• sheep/goats: shearing, tail docking, dehorning
• IM injections
• parturition
• fighting rams
• shearing, docking, castration
• rapidly growing animals on high nutrition plane

Question 6

Pathogenesis of Clostridium

Answer 6

After ingestion/inhalation, spores disseminate to muscle. They can be vegetative until anaerobic conditions created (ie. Via trauma) –> proliferation of bacteria –> exotoxins released –> muscle damage, systemic effects

Question 7

CS of clostridial myositis (peracute)

Answer 7

• sudden death may be only finding

- peracute bacterial proliferation

Question 8

CS of longer (protracted) course of clostridial myositis

Answer 8

• fever
• tachypnea
• tachycardia
• lameness +/- swelling at site of infection
• swelling is hot, painful, fluctuant, malodorous sanguinous fluid, +/- draining, areas can be cold to touch
• very high rate of mortality
• cattle down, sheep reluctant to move

Question 9

Clin path of clostridial myositis

Answer 9

• severe hemoconcentration and dehydration
• normal to increased WBC with L shift
• muscle enzymes inconsistent

Question 10

Dx of clostridial myositis**

Answer 10

1) Hx, CS
2) Isolation of organism from live animal:
- smear: large G+ rods
- FA
- culture of fluid/muscle (won’t help patient directly)
3) Post-mortem:
- gross pathology: crepitus, bloody fluid, rancid butter odor
- IFA or direct smear

Question 11

Tx of clostridial myositis

Answer 11

-prognosis extremely poor
-penicillins** prevent further proliferation
anti-inflammatories
incision/drainage, flush w/ H2O2
-supportive care
-must convert anaerobic env. To aerobic env.!

Question 12

Prevention of clostridial myositis

Answer 12

• investigate potential sources of injury
• minimize chute trauma
• counsel clients
• passive Ab in calves is protective
• multivalent vaccines starting at 4 mo.: 7 or 8-way for cattle
• small ruminant vaccine

Question 13

Sarcocystis cruzi

Answer 13

-protozoa that encysts in muscle and can cause neuro dz

Question 14

White Muscle Disease etiology

Answer 14

• affects most rapidly growing calves, lambs, kids

- more common in areas with selenium deficient soil, poor quality forage

Question 15

Role of selenium

Answer 15

• protection from oxidation injury

- important for muscle cell membrane integrity

Question 16

Vitamin E role

Answer 16

Protects from superoxide damage

Question 17

Pathophys. Of white muscle dz

Answer 17

-lipid peroxidation of muscle membrane –> diffuse muscle degeneration

Question 18

2 forms of white muscle disease

Answer 18

Skeletal

Cardiac

Question 19

CS of skeletal form of white muscle dz

Answer 19

-stiffness, weakness, recumbency
-pain, m. Tremors
+/- resp. Signs (fx of muscles required for respiration affected)

Question 20

CS of cardiac form of white muscle dz

Answer 20

• heart murmurs
• pulm. Edema
• sudden depression, death

Question 21

Clin path of White Muscle Disease

Answer 21

Myoglobinuria
Increased CK, AST, LDH
Plasma Vitamin E

Question 22

White Muscle Disease on histology

Answer 22

-necrotic muscle fibers surrounded by macs

Question 23

Tx of White Muscle Disease

Answer 23

• Selenium preparations
• Vitamin E
• Antioxidants (ie. Vit. C, N-acetyl cystein)
• supportive care (ie. Abx if risk of pneumonia)
• find root of the problem

Question 24

Toxic myopathies

Answer 24

Gossypol (feed additive)
Senna (Cassia)
Tremetol-containing plants (rayless goldenrod, white snakeroot)
Ionophores (monensin, lasalocid)

Question 25

Etiology of gossypol

Answer 25

• comes from cottonseed meal
• toxic to monogastrics and pre-ruminants
• causes peritoneal, pericardial, and pleural fluid accumulation; myocardial necrosis, liver damage

Question 26

ionophores

Answer 26

Anti-coccidial and growth-promoting feed additives

• causes cardiac and skeletal m. Necrosis
• CS relate to cardiac dysfx

Question 27

Predisposing conditions to traumatic myopathy

Answer 27

• metabolic dz
• neuro dz
• recumbency

Question 28

Dx of traumatic myopathy (rhabdomyolysis)

Answer 28

• firm musculature in acute period
• myoglobinuria
• CK values >5000
• elevated AST (more useful with chronic recumbency and previous m. Trauma; longer half-life than CK)

Question 29

Tx of traumatic myopathy

Answer 29

• resolve underlying cause**
• fluids
• NSAIDs
• vit. E/Sel (anti-oxidants)
• nursing care

Question 30

Inherited myopathies

Answer 30

Phosphorylase deficiency: Charolais cattle
Myofiber hyperplasia: Belgian blues
Myotonia congenita: fainting goats

Question 31

Etiology of phosphorylase deficiency

Answer 31

• mutation in charolais
• exercise intolerance/collapse
• serum CK elevated
• genetic screening

Question 32

Etiology of myofiber hyperplasia

Answer 32

• inherited mutation of type 2B muscle fibers
• more likely to have elso heel, dystocia, jaw deformities
• belgian blues

Question 33

Etiology of myotonia congenita

Answer 33

• tetanic m. Contractions when startled
• delay in m. Cell relaxation (interruption of Cl channels in muscle cells)
• autosomal dominant w/ incomplete penetrance

Question 34

Types of muscular diseases

Answer 34

Inflammatory
Nutritional
Toxic
Traumatic 
Inherited