Ruminant Respiratory System
Amelia R. Woolums
Upper Respiratory Tract Diseases
Amelia R. Woolums
Diseases of the Nasal Cavity
Amelia R. Woolums
Mycotic or Bacterial Nasal Granuloma
Infectious granulomas in the nasal cavity of ruminants are not common.
Documented causes include the fungal organisms Rhinosporidium seeberi and other Rhinosporidium spp. (which cause rhinosporidiosis), Helminthosporium spp. (which cause maduromycosis), Drechslera rostrata, Aspergillus spp., Phycomycetes spp., Stachybotrys spp., and Bipolaris spp. Nasal granuloma caused by Nocardia spp. bacteria has also been reported. There is no apparent age, breed, or seasonal predilection, and cases are sporadic. The major clinical signs are upper respiratory noise (stridor), dyspnea, and mucopurulent nasal discharge, sometimes with epistaxis. Affected animals may rub the nose, suggesting pruritus or irritation. Nasal airflow may be reduced, and open-mouth breathing may occur in advanced cases. Hot or dusty weather may accentuate the signs, giving the appearance of seasonal exacerbation, but the lesions are progressive. The granulomas may be single or multiple, unilateral or bilateral, and located anywhere in the nasal cavity. They consist of 0.5- to 5-cm yellow to yellow-green or red nodules or polyps, which may be sessile or pedunculated. Rhinosporidiosis tends to be a single, unilateral polyp in the posterior nasal cavity, and maduromycosis tends to occur in the anterior cavity, but these distinctions are not consistent. Red and black spots (spores) may occur on the masses, and some may become secondarily infected with bacteria and ulcerate. Differential diagnoses include allergic rhinitis, foreign bodies, tumors, nasal actinobacillosis, nasal actinomycosis, and Oestrus ovis infection in small ruminants.Endoscopy, biopsy, and culture of the lesions aid in the diagnosis.
Histopathologic analysis reveals granulation tissue containing eosinophils, mononuclear cells, round sporangia, and sometimes hyphae or filamentous bacteria. The pathogenesis of the disease involves inoculation of eroded nasal mucosa with fungal spores or filamentous bacteria from the environment. The infectious agent causes a chronic delayed (type IV) hypersensitivity reaction, which eventually leads to the formation of a granuloma. Fungal granulomas can be more common in warm, wet climates. The granulomas can be difficult to treat, and although rarely fatal, the disease is chronically debilitating, with salvage often being the most practical solution.Recommended treatments include surgical removal of the granulomas when possible and long-term sodium iodide (NaI) therapy. NaI can be administered at a dose of 66 mg/kg IV as a 20% solution, repeated at 10- to 14-day intervals until remission or iodism occurs. Iodism is characterized by lacrimation, cough, and scaling of the skin. The use of antifungal drugs to treat this condition in ruminants has not been reported.
Allergic Rhinitis and Enzootic Nasal Granuloma
Allergic rhinitis occurs in cattle and in its chronic stages may lead to the formation of granulomas. A similar condition may occur in sheep. The inciting antigen is frequently a plant pollen or more likely a fungal spore. Once homocytotropic antibody (IgE or possibly other classes in cattle) to the allergen has developed, subsequent exposure results in a localized, ongoing, immediate (type I) hypersensitivity reaction. If recurrent exposure to the allergen occurs, repeated tissue damage by mast cell factors results in chronic epithelial, duct, and goblet cell hyperplasia and metaplasia, as well as mucous hypersecretion and granulomatous inflammation, suggesting that a type IV hypersensitivity reaction contributes to the chronic lesion.1
Any breed may be affected, but Channel Island breeds and Friesians seem most susceptible. The disease occurs sporadically in the United States.
A familial predisposition has been reported.2 Most affected animals are between 6 months and 2 years of age. The signs are initially seasonal, usually occurring in warm, moist conditions; they include rhinorrhea, sneezing, nasal pruritus, a sudden onset of dyspnea, and stertorous inspiration. There is a profuse bilateral nasal discharge. Intense pruritus is characteristic and associated with sneezing, headshaking, and nose rubbing. In severe cases facial swelling, tachypnea, hyperpnea, and ulceration of the nasal mucosa may occur. Nasal foreign objects may result from the animal's attempts to scratch the nasal mucosa. Lacrimation, chemosis, and blepharitis may also be present. In the chronic stages (the “enzootic nasal granuloma”), the signs are more constant, with seasonal exacerbations. The granulomas tend to be multiple, firm, white, raised nodules 1 to 2 mm in diameter with an intact mucosa, or pale pink, flat plaques scattered throughout the nasal cavity. Differential diagnoses include fungal granulomas, foreign bodies, respiratory viruses, nasal actinomycosis or actinobacillosis, tumors, O. ovis infection (small ruminants), and irritation caused by inhalation of hot or irritant gases.Endoscopy; biopsies; cultures; antigen detection tests for viruses, bacteria, or fungi; and serologic analysis can be used to rule out these differential diagnoses. Eosinophil counts in nasal secretions correlate with the susceptibility of the animal and activity of the disease, but no absolute level is diagnostic. Intradermal allergen testing has been suggested to aid in diagnosis, but interpretation of results needs to be done in conjunction with historical and clinical findings.3 This condition should be differentiated from fungal or bacterial granuloma because the therapy is different.
Treatment and control entail removal of the allergen, or removal of the animal from the allergen, and therapy to block the hypersensitivity reaction. Recommended drugs include various antihistamines, meclofenamic acid, and corticosteroids at standard antiinflammatory doses (0.05 to 0.2 mg of dexamethasone per kilogram IM or IV or 1 to 2.2 mg of prednisolone per kilogram IM or IV daily).
Topical corticosteroid therapy can be considered in severe, acute occurrences of the disease. The adverse effects of corticosteroids on milk production and their potential to induce abortion or parturition should be considered before their use. Antihistamine therapy has had equivocal results.3Nasal Foreign Bodies
Cattle are more prone than small ruminants to the acquisition of nasal foreign bodies. Foreign objects may be acquired as a result of attempts to scratch the nose in cases of allergic rhinitis or because of the cow's aggressive eating habits. Depending on the size and duration of residence of the object, signs may include headshaking, stridor, sneezing, snorting, frequent nose licking, unilateral decreases in airflow, foul odors, and serous, mucopurulent, or hemorrhagic discharges. Differential diagnoses include fungal granulomas, allergic rhinitis, tumors, nasal actinomycosis or actinobacillosis, and O. ovis infection (small ruminants). Many objects can be visualized on careful examination of the nasal cavity with an adequate light source, but some may require endoscopy for diagnosis and removal.
Nasal Trauma and Fractures
Trauma to the facial bones, sinuses, and turbinates may result from fighting, accidents caused by improper restraint, farm machinery accidents, human maliciousness, and passage of excessively large nasogastric tubes. Severe fractures can lead to facial swelling, subcutaneous emphysema, obstruction of airflow, stertor, and epistaxis. Secondary infection causes foul odors and mucopurulent nasal discharge. Differential diagnoses for the acute external swelling of the head with stertor include snakebite, actinobacillosis, actinomycosis, and phlegmon (Fusobacterium, Clostridium spp.). Unless the development of severe depression fractures, formation of sequestra, or severe obstruction of airflow occurs, surgery is usually not indicated. Radiographs confirm the diagnosis and help determine the need for surgical removal of potential sequestra or elevation and fixation of large displaced segments.
Prophylactic antibiotics (typically penicillin, 22,000 IU/kg IM q12-24h) are recommended to prevent fracture infection and sinusitis, and NSAIDs (flunixin meglumine, 1.1 to 2.2 mg/kg IV daily or divided twice daily) may help relieve pain, swelling, and stridor. The prognosis is usually good.Nasal Tumors and Polyps
Tumors and polyps of the nasal cavity and sinuses are rare in ruminants. Nasal tumors reported in cattle include osteomas and osteosarcomas of the sinuses, squamous cell carcinomas, neuroblastomas, and adenocarcinomas of the ethmoid mucosa. Ethmoid adenocarcinomas are speculated to be caused by viruses on the basis of an endemic pattern in some cases. They tend to occur in cattle 6 to 9 years of age and are frequently unilateral. Metastasis occurs to the lymph nodes and lungs. Signs common to all nasal tumors include mixed or inspiratory dyspnea, stridor, nasal discharge, epistaxis, foul breath odors, unilateral decreases in airflow, open-mouth breathing, and distortion of the facial bones. Differential diagnoses include fungal granulomas, atopic granulomas, foreign bodies, sinusitis, fractures, and nasal actinobacillosis and actinomycosis. Treatment has not been investigated.
The majority of nasal neoplasms in sheep and goats are adenopapillomas, adenomas, or adenocarcinomas. Squamous cell carcinoma has also been reported. An enzootic form of nasal adenocarcinoma occurs in both sheep and goats and is associated with ovine nasal adenocarcinoma virus (ONAV)4 or caprine nasal adenocarcinoma virus (CNAV),5 respectively. These agents are β-retroviruses that are closely related to but distinct from jaagsiekte sheep retrovirus (JSRV), the cause of ovine pulmonary adenocarcinoma (OPA). Although nasal adenocarcinoma has been difficult to consistently reproduce experimentally, inoculation of kids with concentrated cell-free and bacteria-free filtrate containing virus from naturally infected goats has resulted in disease.6 Neoplastic transformation is limited to secretory epithelial cells of the nasal turbinates, but CNAV appears to have a wider tissue tropism than ONAV; in one study viral provirus incorporated into host DNA was found in many tissues of infected goats but was largely confined to tumor tissue of infected sheep.5 There is no breed or sex predisposition for enzootic nasal adenocarcinoma; affected animals are most commonly young adults, but the tumor has been identified as early as 4 months of age.
Signs include progressive inspiratory dyspnea; stridor; exercise intolerance; mouth breathing; serous, mucoid, or mucopurulent nasal discharge, which is typically profuse; tachypnea; decreased airflow; headshaking; sneezing; exophthalmos; and facial asymmetry. The lesions may be unilateral or bilateral, originating in the olfactory region of the ethmoid turbinates. The neoplasia arises either from Bowman's glands or serous glands of the nasal mucosa. The tumor begins as a small nodule that can grossly resemble the mucoid polyps that occur in animals with chronic rhinitis. Over time the adenocarcinoma grows into a soft, gray to grayish-pink, mucoid, nodular, cystic mass. The tumor is benign but locally expansive, often entering the sinuses and eroding overlying bone. Histologically the tumor is typically classified as a low-grade adenocarcinoma, but it may also be identified as an adenopapilloma or adenoma. Initially affected animals eat and drink normally and maintain body condition, but as the tumor expands, the animal begins to lose condition, and death eventually occurs as a result of inanition, asphyxia, or aspiration pneumonia. Necrosis or secondary bacterial infection of the tumor can occur and may lead to the production of foul-smelling, purulent discharge and systemic signs related to bacterial infection, such as fever, depression, and hyperemic mucous membranes.Differential diagnoses for nasal neoplasia in small ruminants include nasal fungal or bacterial granuloma, actinobacillosis, actinomycosis, O. ovis infection, and sinusitis. Endoscopy and radiology are helpful in establishing an initial diagnosis of a nasal mass. Preoperative or antemortem pinch biopsies and exfoliative cytologic analysis frequently are nondiagnostic, and findings may be misleading. Identification of tumors in multiple animals in a herd or flock supports a diagnosis of enzootic nasal adenocarcinoma. Definitive identification of infection with ONAV or CNAV can be difficult. Serologic tests are not reliable because animals do not consistently produce antibody to the viruses, possibly because of the presence of endogenous retroviruses that share epitopes with ONAV and CNAV and induce the development of immunologic tolerance. PCR has been used to specifically identify and differentiate ONAV, CNAV, and JSRV in tissues of affected animals. Surgical management of nasal adenocarcinoma in sheep has been 7 described.7