Camelidae and Cervidae Pericarditis and Epicarditis – NAVLE Study Guide

Overview and Clinical Importance

Pericarditis (inflammation of the pericardium) and epicarditis (inflammation of the epicardium/visceral pericardium) represent important cardiovascular conditions in camelids and cervids. While relatively uncommon compared to cattle, these conditions carry significant clinical importance for veterinary practitioners working with llamas, alpacas, deer, and elk. The pericardium consists of two layers: the fibrous pericardium (outer layer) and the serous pericardium, which is divided into the parietal layer (lining the fibrous pericardium) and the visceral layer (epicardium, covering the heart surface). Inflammation of these structures leads to fluid accumulation, fibrin deposition, and potentially life-threatening cardiac tamponade.

In camelids, pericarditis most commonly occurs as part of polyserositis associated with septicemic bacterial infections, particularly Streptococcus equi subspecies zooepidemicus (alpaca fever). In cervids, pericardial disease is less well documented but can occur secondary to systemic infections, trauma, or as part of multisystemic disease processes.

Anatomical Considerations

Camelid Cardiac Anatomy

The alpaca heart is located in the middle mediastinum with a craniocaudal extension from the third to the sixth rib. Unlike domestic ruminants, no ligament connects the fibrous pericardium to the sternum or diaphragm in alpacas, which may have implications for pericardial mobility and disease presentation. The Purkinje fiber network in camelids penetrates completely through the ventricular wall from endocardium to epicardium (similar to sheep), resulting in distinctive ECG patterns that differ from dogs and cats.

Normal Camelid Cardiac Parameters

Cervid Cardiac Anatomy

Cervids (deer, elk, moose) share cardiac anatomical features with domestic ruminants. The heart is located in the thoracic cavity with similar positioning to cattle. Sarcocysts in the myocardium are commonly found in wild deer populations (affecting up to 42% of free-living deer in some studies) and may be associated with interstitial cellularity and myocardial changes. Cardiovascular disease in cervids can include aortic lesions ranging from lipid streaking to massive calcium deposits, coronary artery changes, and pericardial involvement.

Etiology and Pathophysiology

Classification of Pericarditis

Etiologies in Camelidae

Alpaca Fever (Streptococcus equi ssp. zooepidemicus)

The most clinically important cause of pericarditis in camelids is Streptococcus equi subspecies zooepidemicus septicemia, commonly called "alpaca fever." This gram-positive, beta-hemolytic, Lancefield group C organism causes characteristic fibrinosuppurative polyserositis affecting the pericardium, pleura, and peritoneum. The disease was first described in Peru, where morbidity in some herds reaches 5-10%, with mortality rates of 50-100% in untreated cases.

Alpaca Fever: Key Features

Other Causes in Camelids

• Clostridial infections: C. perfringens can cause enterotoxemia with hydropericardium and pulmonary edema
• Lymphoma: Most common cardiac tumor in camelids; heart involved in 25-40% of camelids with lymphoma; can cause pericardial effusion/tamponade
• Heart failure: Secondary mild pericardial effusion can occur with severe heart failure or hypoproteinemia
• Endocarditis extension: Mural endocarditis (more common in camelids than valvular) can extend to epicardium

Etiologies in Cervidae

Pericardial disease in cervids (deer, elk, moose) is less well documented than in camelids or cattle. Potential causes include:

• Septicemic infections: Histophilus somni, Pasteurella multocida, Mannheimia haemolytica can cause polyserositis similar to bovine disease
• Parasitic myocarditis: Sarcocysts commonly affect wild deer myocardium (up to 42% prevalence) and may involve the epicardium
• Traumatic pericarditis: Less common than in cattle due to different feeding behavior, but can occur in farmed cervids fed processed feeds containing wire or metal
• Cardiovascular degeneration: Aortic lesions and coronary artery changes have been documented in wild red deer

Clinical Signs and Presentation

Acute Pericarditis

The clinical presentation of pericarditis depends on the underlying cause, rate of fluid accumulation, and presence of concurrent disease. Acute pericarditis, particularly as part of septicemic polyserositis, typically presents with:

Cardiac Tamponade

Cardiac tamponade occurs when pericardial fluid accumulation raises intrapericardial pressure sufficiently to impair cardiac filling. Right-sided heart failure signs predominate because right atrial and ventricular diastolic pressures need to increase only from 5 mmHg to 10-15 mmHg to cause clinical signs, while left-sided pressures must exceed 20 mmHg.

Classic findings of tamponade:

• Muffled/distant heart sounds
• Jugular venous distension with or without pulsation
• Hypotension or weak arterial pulses
• Pulsus paradoxus (exaggerated decrease in arterial pressure with inspiration)
• Tachycardia

Diagnostic Approach

Laboratory Findings

Laboratory abnormalities in pericarditis are often nonspecific but support the presence of inflammation and may indicate organ dysfunction secondary to compromised cardiac output:

Echocardiography

Echocardiography is the gold standard for diagnosing pericardial disease and assessing hemodynamic impact. In camelids, standard echocardiographic examination is performed from the right parasternal window at the 4th-5th intercostal space using a low-frequency (2-3.5 MHz) transducer for adults or higher frequency (5-7.5 MHz) for crias.

Echocardiographic Findings in Pericarditis

Pericardiocentesis

Ultrasound-guided pericardiocentesis may be performed diagnostically or therapeutically through the 4th intercostal space on either side, taking care to avoid the heart. Analysis of pericardial fluid includes:

• Gross appearance: Color, turbidity, odor (septic pericarditis often has foul odor)
• Cytology: Cell count, differential, presence of bacteria (intracellular or extracellular)
• Culture: Aerobic and anaerobic bacterial culture with sensitivity testing
• Protein/specific gravity: Distinguishes transudate from exudate

Electrocardiography

Important limitation: ECG in camelids provides limited information about cardiac chamber size due to extensive Purkinje fiber penetration throughout the myocardium. However, ECG may show:

• Sinus tachycardia
• Decreased QRS voltage (with significant effusion)
• Electrical alternans (varying QRS amplitude with cardiac swinging)
• Premature complexes or arrhythmias

Treatment and Management

Antimicrobial Therapy

For septic pericarditis and polyserositis (particularly S. equi ssp. zooepidemicus), aggressive antimicrobial therapy is essential. Antimicrobial selection should ideally be guided by culture and sensitivity, but empirical therapy is often initiated while awaiting results:

Supportive Care

• Fluid therapy: IV crystalloid fluids for dehydration and cardiovascular support; avoid fluid overload in animals with significant effusion
• NSAIDs: Flunixin meglumine (1 mg/kg IV q 12-24h) for anti-inflammatory and analgesic effects
• Analgesia: Butorphanol (0.1 mg/kg SC) for additional pain control
• Diuretics: Furosemide (1-2 mg/kg) may provide short-term relief of congestive signs; use cautiously
• Nutritional support: Partial parenteral nutrition if anorexic; maintain hydration and caloric intake

Pericardiocentesis and Surgical Options

Pericardiocentesis can relieve cardiac tamponade and provide diagnostic samples. However, results in septic pericarditis are often disappointing as fibrinous/purulent material may be too thick for needle drainage. For valuable animals, options include:

• Repeated pericardiocentesis: May be performed daily with indwelling catheter for drainage and local antibiotic infusion
• Pericardiotomy: Fifth rib resection approach; allows evacuation and lavage of pericardial sac
• Pericardiectomy: Partial or subtotal removal of pericardium; may be considered for constrictive pericarditis

Prognosis

Prognosis varies significantly based on the underlying etiology and stage of disease at presentation:

Prevention and Herd Management

Prevention strategies focus on reducing stress and limiting exposure to infectious agents:

• Minimize transport stress: Adequate rest periods, appropriate climate control, minimize commingling
• Quarantine new arrivals: Isolate new animals for 2-4 weeks; monitor for clinical signs
• Separate species: Avoid housing camelids with horses (potential S. equi ssp. zooepidemicus reservoir)
• Reduce overcrowding: Adequate space reduces stress and disease transmission
• Biosecurity: Fomite disinfection, clean equipment, limit visitors
• Feed management (cervids): Use magnets in feed systems if feeding processed feeds; inspect hay and feed for metal contamination

Memory Aid - "ALPACA HEARTS":

A = Alpaca fever (S. equi ssp. zooepidemicus)

L = Lymphoma (most common cardiac tumor)

P = Polyserositis (pericardium + pleura + peritoneum)

A = Anechoic effusion on echo

C = Ceftiofur is first-line treatment

A = Acute onset with stress/transport