JPC SYSTEMIC PATHOLOGY
Signalment (AFIP #1946321): 3-year-old crossbred sow
HISTORY: An outbreak of disease occurred on a large swine breeding facility. Symptoms common to a majority of the sick animals were anorexia, high fever, cyanosis and abortion.
HISTOPATHOLOGIC DESCRIPTION: Kidney: Multifocally glomerular tuft and interstitial capillaries contain brightly eosinophilic, hyalinized fibrin thrombi. Mild edema and fibrin accumulation are present within the tunica adventitia and perivascular tissues of arcuate and intralobular arteries as well as hypertrophy of vascular endothelium. Multifocally, the interstitium contains a few small aggregates of lymphocytes, plasma cells, macrophages, and occasional neutrophils. Multifocally tubular epithelial cells exhibit one or more of the following changes: flattening and attenuation; increased cytoplasmic volume and vacuolation (degeneration); shrunken cells with bright eosinophilic cytoplasm, angular margins and dense to pyknotic nuclei (necrosis); sloughing of epithelium into tubular lumina, and accumulation of few erythrocytes and small amounts of flocculant eosinophilic debris. There are moderate multifocal autolytic changes.
MORPHOLOGIC DIAGNOSIS: Kidney, glomerular and interstitial capillaries: Fibrin thrombi, acute, multifocal, moderate with lymphoplasmacytic and neutrophilic interstitial nephritis, perivascular edema, and mild tubular degeneration and necrosis, crossbred pig, porcine.
ETIOLOGIC DIAGNOSIS: Renal erysipelothricosis
CAUSE: Erysipelothrix rhusiopathiae
CONDITION: Swine erysipelas; “diamond skin disease”
- Ubiquitous gram-positive, facultative anaerobic bacillus that is both a commensal and pathogen in wide range of vertebrates.
- Swine are the most important reservoir of the organism. 30-50% of healthy swine harbor the organism in their tonsils or other lymphoid tissue, and shed the organism in urine, saliva, vomitus, and feces
- Most common bacterial cause of embolic nephritis in pigs
- Swine 2-12 months old and pregnant sows are most susceptible; skin lesions may occur in pigs up to 3 years of age
- Disease manifestations include: septicemia (acute), cutaneous lesions (acute), polyarthritis (chronic), endocarditis (chronic), discospondylitis and septic emboli in the CNS
- Pigs encounter the organism via ingestion, contamination of cutaneous wounds, or bites of infected flies; rhusiopathiae is also a commensal and stress or other conditions may precipitate disease
- Neuraminidase may be a virulence factor that helps invade the mucus layer of the pharynx. The enzyme removes sialic acid from host cells possibly exposing receptors for the bacteria
- Other virulence factors include capsular polysaccharides, surface proteins, invasins (e.g. hyaluronidase to help invade tissues), superoxide dismutase, cell wall peptidoglycans and catalase.
- Acute systemic erysipelas: Invades through tonsils or GALT > infects and replicates in macrophages > travel to regional lymph nodes and infect additional macrophages > bacteremia > endothelial swelling of capillaries & venules > bacteria can invade endothelial cells> fibrinoid necrosis > fibrin thrombi > ischemia & infarction > necrosis
- Chronic erysipelas: Bacterial neuraminidase may activate the alternative complement pathway > complement-derived chemotactic messengers > injury to capillary beds; this may contribute to vegetative valvular endocarditis and arthritis that occurs in the chronic septicemic form of the disease
TYPICAL CLINICAL FINDINGS:
Porcine erysipelas occurs in all ages but most susceptible are pregnant sows and pigs 2-12 months old; manifestations vary from acute septicemic (epidemic-associated) and mild, chronic forms (endemic-associated)
- Acute erysipelas:
- Sudden onset, sometimes sudden death in one or more animals in the herd
- High fever (104-108 degrees F)
- Fibrinous polyarthritis
- Constipation or obstipation in older pigs and diarrhea in young pigs
- Erythematous rhomboid urticarial skin lesions, often over abdomen, ears, tail,
posterior thighs and jowls
- Chronic erysipelas:
- Arthritis is common; varying degree of severity; diskospondylitis
- Slow growth rate
- Signs of cardiac insufficiency, especially after exertion
TYPICAL GROSS FINDINGS:
- Cutaneous vasculitis with dermal infarcts
- Characteristic erythematous cutaneous lesions are rhomboid (diamond-shaped), slightly raised, light pink to dark purple, and vary in number; the skin lesions may be necrotic and eventually peel off
- Edematous and congested lungs
- Petechiae and ecchymoses of the epicardium, atrial myocardium, and renal cortex
- Multifocal regions of pinpoint hemorrhage in renal cortex (in glomeruli), OR multifocal tan-white foci of infiltrate in interstitium
- Hemorrhagic gastritis
- Congested liver and markedly congested and enlarged spleen
- Congested to hemorrhagic lymph nodes
- Chronic villonodular synovitis
- Joints (most commonly hock, stifle, elbow, and carpal): excessive serosanguinous synovial fluid, variably hyperemic and proliferative synovial membrane, fibrous synovial “tags” that project into the joint cavity, and synovitis and articular cartilage destruction leading to ankylosis
- Vegetative valvular (mitral valve most common) and mural endocarditis
TYPICAL LIGHT MICROSCOPIC FINDINGS:
- Capillaries & venules in skin, heart, kidney, lung, liver, CNS, skeletal muscle and synovium may have swollen endothelial cells with adherent monocytes, fibrin thrombi and bacteria often arranged side by side in a radial fashion near the surface of the thrombi
- Small foci of encephalitis common in pigs with valvular endocarditis, in addition to renal lesions
- Perivascular lymphocytes and macrophages predominate, with fewer neutrophils
- Circulatory stasis may cause focal necrosis in affected tissues
- +/- Glomerular hemorrhage and inflammation and rare tubular necrosis
- Mononuclear, proliferative synovitis, cartilage erosion, and osteitis
- Valvular granulation tissue with fibrin and masses of bacteria
ADDITIONAL DIAGNOSTIC TESTS:
- Gram stain
- PTAH- highlights thrombi purple/blue
- For “Turkey egg kidney”
- Hog Cholera (Pestivirus) – Splenic infarction, if present, is pathognomonic
- Salmonella choleraesuis – Paratyphoid nodules in the liver
- African Swine Fever (“Asfarviridae”)- Splenomegaly
- Porcine dermatitis and nephropathy syndrome – Severe necrotizing and leucocytoclastic (presence of neutrophils with nuclear fragments) vasculitis; red to purple macules and papules that often coalesce forming irregular patches and plaques over perineum and lower limbs
- Septicemia due to other bacteria such as Streptococcus and Actinobacillus spp
- For cutaneous lesions
- Dermatosis vegetans; porcine juvenile pustular and psoriasiform dermatitis; swine pox
- Sheep: Percutaneous infection via umbilicus, docking/shearing/castration wounds; no history of contact with swine; bacteremia/septicemia with fibrinopurulent polyarthritis & osteomyelitis in lambs usually around the fetlocks; necrotizing glomerulonephritis and amyloid deposits in liver and spleen in chronic cases, as well as necrosis of purkinje cells in brain
- Turkeys: Acute septicemia or chronic arthritis and/or endocarditis; birds have cyanotic skin (“blue comb”) and hemorrhages of leg and breast muscles, various serosal surfaces (esp. heart), and gizzard and enteric mucosa **many birds can be infected**
- Calves: Rare arthritis (tibiotarsal, stifle, and carpal) and encephalomeningitis
- Lab animals (rats): Fibrinopurulent polyarthritis, myocarditis, and endocarditis
- Chickens: Enteritis, salpingitis and peritonitis, petechiation of pericardial and abdominal fat, splenomegaly and hepatomegaly with multifocal areas of necrosis. disease is more severe in older birds
- Dolphins: Cutaneous vasculitis (“Diamond Back”) or peracute to subacute septicemia
- Dogs: Case report of skin lesions in immunosuppressed dog; unusual cause of endocarditis in dogs
- Pribilof arctic foxes: shaggy, lame fox syndrome (suspected)
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