JPC SYSTEMIC PATHOLOGY

INTEGUMENTARY SYSTEM

November 2022

I-T02

 

Signalment (JPC# 1948001): Two-year-old cow

 

HISTORY: Four of 100 cattle developed crusty dermatitis over the face, neck, back and perineum over 3-4 weeks.  Some were salivating and dyspneic.  Two of the cows died after 1-2 weeks of illness.

 

HISTOPATHOLOGIC DESCRIPTION: Haired skin: The dermis is multifocally infiltrated by moderate numbers of periadnexal and perivascular eosinophils, macrophages, lymphocytes, and fewer neutrophils and plasma cells. The epidermis and follicular epithelium are mildly hyperplastic characterized by a thickened stratum spinosum (acanthosis) and mild orthokeratotic and parakeratotic hyperkeratosis; there is also widening of the intercellular spaces with prominent bridging (spongiosis) and keratinocytes often have increased intracellular clear space (intracellular edema) occasionally with pyknotic nuclei. The superficial dermal collagen is separated by increased clear space and occasional small lakes of amphophilic fluid, and there are occasional ectatic lymphatics (edema). Dermal capillaries are lined by reactive endothelium, and apocrine glands are often ectatic.

 

Heart: Separating, surrounding, and replacing approximately 30% of cardiac myocytes are multiple coalescing aggregates of moderate numbers of eosinophils and macrophages with fewer lymphocytes, neutrophils, plasma cells, and low numbers of multinucleated giant cells (foreign body and Langhans type). Affected myofibers are occasionally swollen with fragmented sarcoplasm and swollen to vesiculate nuclei (degeneration), or rarely have fragmented, shrunken, hypereosinophilic sarcoplasm, loss of cross-striations, and nuclear pyknosis or karyolysis (necrosis), or are lost with replacement by fibrosis. Randomly, rare myofibers contain few, ovoid, intracytoplasmic protozoal cysts that are up to 50 × 120µm with a thin (1µm) outer cyst wall and contain numerous 3 × 7µm basophilic crescentic bradyzoites (sarcocysts). 

 

MORPHOLOGIC DIAGNOSIS: 

1. Haired skin: Dermatitis, perivascular and periadnexal, histiocytic and eosinophilic, multifocal, moderate, with epidermal hyperplasia, breed not specified, bovine.

2. Heart: Myocarditis, granulomatous and eosinophilic, multifocal, moderate, with myofiber degeneration and rare necrosis. 

3. Heart, myocardium: Sarcocysts, multifocal, few.

 

ETIOLOGIC DIAGNOSIS:  Toxic dermatitis and myocarditis

 

CAUSE:  Hairy vetch (Vicia villosa Roth) toxicity

 

GENERAL DISCUSSION: 

• Vicia spp. are legumes used as pasturage, hay, or cover crop; several species have been reported to cause toxicosis in domestic animals (primarily cattle, less often horses) and humans
• Primarily holstein and angus cattle, three years of age or older, that have been grazing hairy vetch between April and June
• Diagnosis of vetch toxicity or vetch-like diseases is a diagnosis by exclusion
• Three distinct syndromes:

• Acute fatal neurologic disease and hemolysis: Due to ingestion of seeds containing cyanogenic glycosides (prussic acid)
• Swelling of the upper body, herpetiform eruptions of the oral mucous membranes, respiratory distress and death: Consumption of hairy vetch pasture 
• Dermatitis, conjunctivitis, diarrhea, and systemic granulomatous disease (SGD): Consumption of hairy vetch pasture; most common

 

PATHOGENESIS:

• Toxic principles and pathogenesis are unknown 

• Possible Type IV hypersensitivity: Ingestion of hairy vetch may involve adsorption of component as haptens or complete antigens, leading to antigen‑specific memory T‑cells; re-exposure leads to type IV hypersensitivity  and granulomatous inflammation
• Alternatively, vetch lectins may directly activate T-cells with subsequent lymphokine production and granulomatous inflammation
• Genetic predisposition possible in Holstein and Angus cattle

 

TYPICAL CLINICAL FINDINGS: 

• Morbidity is low; mortality ranges from 50-100% with death 10-20 days after illness onset
• Pruritic dermatitis develops 2-6 weeks after exposure with papular swellings and crusts in the skin on the udder, tailhead, and neck; progresses to face, trunk, and limbs
• Papules become confluent; often exude a clear to yellow fluid (superficial exudative crusts); often results in self-induced trauma and alopecia; +/- lichenification and excoriations
• Conjunctivitis, diarrhea, weight loss, pyrexia, drop in milk yield, sporadic abortion
• Red-tinged urine, lymphocytosis and hyperproteinemia

 

TYPICAL GROSS FINDINGS:

• Alopecic, thickened, "pleated" skin 
• Enlarged adrenal glands, lymph nodes, spleen, thyroid glands
• Yellow-gray well-demarcated nodular infiltrates/streaks in the ventricular myocardium, renal cortex, adrenal glands, lymph nodes, spleen, and thyroid glands

 

TYPICAL LIGHT MICROSCOPIC FINDINGS: 

• Polysystemic, multifocal to coalescing eosinophilic granulomatous infiltrates composed of monocytes, lymphocytes, plasma cells, eosinophils (in the cow), and multinucleated giant cells 
• Exudative perivascular dermatitis with dermal and epidermal edema and hyperkeratosis
• Vascular endothelial swelling, diffuse and perivascular inflammation

 

DIAGNOSIS:

 

DIFFERENTIAL DIAGNOSIS: 

Systemic granulomatous disease:

• Citrus pulp toxicosis:  Very similar findings to hairy vetch toxicosis
• Sylade poisoning (a commercial silage additive consisting of formalin and sulphuric acid):  Pyrexia, pruritis, hemorrhagic syndrome of dairy cows
• Diureido-isobutane (DUIB) poisoning:  Systemic granulomatous disease (SGD)
• Vetch-like disease (pyrexia/pruritis/hemorrhagic syndrome):  Systemic granulomatous disease of unknown origin; animals do not have access to pastures containing vetch species

Other diseases caused by vetch species:

• Vicia villosa, in addition to the chronic syndrome described above, can cause acute fatal neurologic disease and hemolysis due to consumption of the vetch seeds that contain prussic acid (cyanogenic glycosides) 
• Vicia sativa (common vetch):  Ingestion of seeds which contain prussic acid before maturity; gastroenteritis, hepatitis, icterus, and hepatogenous photosensitization

 

COMPARATIVE PATHOLOGY:

 

REFERENCES:

1. Mauldin EA, Peters-Kennedy J. Integumentary system. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals.  Vol 1. 6th ed. Philadelphia, PA: Elsevier Saunders; 2015:574.
2. Plassard V, Briand A, Laloy E, Gourreau JM, Pin D, Millemann Y. Cutaneous and systemic granulomatous disease associated with hairy vetch toxicosis in a French Holstein dairy herd. Vet Dermatol. 2021;32(2):196-199.
3. Sula MM, Lane LV. The urinary system. In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 7th ed. St. Louis, MO: Elsevier; 2022:748.
4. Welle MM, Linder KE. The Integument. In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 7th ed. St. Louis, MO: Elsevier; 2022:1223.

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