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Myocarditis 675

repeat in 7-14 days) for dogs (negative for PROGNOSIS & OUTCOME Technician Tips
heartworms) can be used for killing maggots. Guarded to good, depending on the severity In warm weather, myiasis is one of the reasons
VetBooks.ir • Although not approved for myiasis, topical of the infestation and underlying predisposing scalding of the skin and haircoat) is so impor- Diseases and Disorders
CAUTION: avoid in susceptible individuals
hygiene (avoidance of fecal staining or urinary
(p. 638).
tant, especially for recumbent patients.
conditions
or orally-administered isoxazolines (NexGard,
Bravecto, Credelio, or Simparica), oral niten- PEARLS & CONSIDERATIONS Client Education
pyram (Capstar), or spinosad/milbemycin Basic hygiene care and early intervention when
(Triflexis) at routine dosages have shown a Comments a pet is debilitated for any reason are essential
maggot-cidal effect. In the United States, • Myiasis is a disease of neglect. for preventing myiasis.
these drugs are labeled by the U.S. Food and • Depending on the country, some types of
Drug Administration, not the Environmental myiases are reportable. SUGGESTED READING
Protection Agency. • Avoid crushing or cutting maggots in vivo Miller WH Jr, et al: Muller & Kirk’s Small animal
• Wound care (p. 1189) because remaining body parts may cause dermatology, ed 7, St. Louis, 2013, Saunders, pp
• House animal in fly-free area (e.g., indoors, allergic reactions. 331-332.
screened-in patio).
• Empirical antibiotic therapy for secondary Prevention AUTHOR: Adam P. Patterson, DVM, DACVD
EDITOR: Manon Paradis, DMV, MVSc, DACVD
bacterial infection (e.g., cephalexin 22-30 Animals with wounds (including perianal
mg/kg PO q 8-12h or clavulanic acid– fistulas) should be housed indoors.
potentiated amoxicillin 12.5-20 mg/kg PO
q 12h for 21-30 days)

Myocarditis Client Education
Sheet

Clinical Presentation
BASIC INFORMATION • Murmur
DISEASE FORMS/SUBTYPES • Lymphadenopathy
Definition Myocarditis encompasses a range of etiolo- • Skeletal muscle weakness
Myocarditis, which is inflammation of the gies resulting in many clinical and histologic • With traumatic myocarditis, evidence of
heart muscle that is typically associated with manifestations. For viral myocarditis, three blunt chest trauma or generalized signs of
myocytolysis, can result from infectious, chemi- phases of disease are recognized: trauma
cal, or physical causes. • Phase 1: acute myocarditis associated
with acute viremia, myocyte necrosis, and Etiology and Pathophysiology
Epidemiology macrophage activation Mechanism:
SPECIES, AGE, SEX • Phase 2: subacute myocarditis associated • The heart’s immune response to inflammation
Myocarditis occurs rarely and is recognized more with viral clearing and overzealous immune determines the structural and functional
often in dogs than in cats. No age predisposition response by cell-mediated and humoral abnormalities in the cardiomyocyte; may
(exception: parvoviral myocarditis in puppies immunity and cytokine activation result in subclinical disease that is often
3-8 weeks of age). • Phase 3: chronic myocarditis, or DCM, unnoticed, or substantial myocardial dysfunc-
associated with cardiac remodeling, fibrosis, tion and cardiac arrhythmias.
RISK FACTORS cardiac dilation, and CHF Etiology:
• Can result from an extension of infectious In veterinary medicine, myocarditis is most • Bacterial: Bacillus piliformis, Citrobacter
endocarditis (p. 294) often recognized in the chronic phase in a young koseri; streptococci, staphylococci, Bartonella,
• Dogs and cats that roam are at risk for dog that is not of a breed commonly associated Brucella, Leptospira, Salmonella spp
traumatic and vector-borne causes of with DCM and that presents with acute CHF, • Spirochete: Borrelia burgdorferi
myocarditis. DCM, and severe arrhythmias. • Protozoan: Trypanosoma cruzi, Toxoplasma
gondii, Neospora caninum, Babesia spp,
GEOGRAPHY AND SEASONALITY HISTORY, CHIEF COMPLAINT Leishmania infantum
• Chagas’ myocarditis (Trypanosoma cruzi): Presenting complaint can be vague or specific • Viral: parvovirus
southern United States, Latin America to the cardiovascular system and may include • Other: doxorubicin chemotherapy, cat-
• Lyme myocarditis (Borrelia burgdorferi): • Anorexia echolamines, lead, arsenic, stinging insect
more common in the northeastern United • Lethargy/exercise intolerance and snake venom, hyperthermia, radiation
States • Cough/dyspnea therapy, blunt or penetrating trauma
• Syncope
ASSOCIATED DISORDERS • Sudden death DIAGNOSIS
• Myocarditis is often associated with • With traumatic myocarditis, a history of
cardiac arrhythmias (especially ventricular having been hit by a car is common. Diagnostic Overview
tachyarrhythmias, but occasionally atrial A clinical classification system for myocarditis
tachyarrhythmias or atrioventricular [AV] PHYSICAL EXAM FINDINGS in humans is based on the level of clinical
block). Possible findings include certainty; it can be extrapolated to veterinary
• Myocarditis, if chronic, may lead to dilated • Signs of CHF (p. 408) medicine:
cardiomyopathy (DCM) and congestive heart • Cardiac arrhythmias ± pulse deficits • Possible subclinical myocarditis: sub-
failure (CHF). • Possible fever or history of febrile illness clinical patient with cardiac biomarkers,

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