Dog illnesses

Structural or functional abnormalities of the thyroid gland can lead to deficient production of thyroid hormones. A convenient classification scheme for hypothyroidism in dogs has been devised that is based on the location of the problem within the hypothalamic-pituitary-thyroid gland complex. Primary hypothyroidism in dogs is the most common form of this disorder; it results from problems within the thyroid gland, usually destruction of the thyroid gland.

The two most common histologic findings in this disorder are lymphocytic thyroiditis and idiopathic atrophy of the thyroid gland. Lymphocytic thyroiditis is an immune-mediated disorder characterized by a diffuse infiltration of lymphocytes, plasma cells, and macrophages into the thyroid gland. The factors that trigger the development of lymphocytic thyroiditis are poorly understood, but genetics factors undoubtedly play a role.

Idiopathic atrophy of the thyroid gland is characterized by loss of the thyroid parenchyma. There is no inflammatory infiltrate, even in areas where small follicles or follicular remnants are present. The cause of idiopathic thyroid atrophy is not known, but it may be a primary degenerative disorder. It may also represent an end stage of autoimmune lymphocytic thyroiditis.

Hypothyroidism symptoms in dogs

Clinical signs of the more common forms of primary hypothyroidism in dogs usually develop during middle age. Clinical signs tend to develop at an earlier age in breeds at increased risk than other breeds. There is no apparent sex-related predilection.

Dog Breeds that have an increased prevalence of hypothyroidism:

Pointer
English Pointer
German Wirehaired Pointer
Boxer
Kuvasz
American Staffordshire Terrier
American Pit Bull Terrier
Giant Schnauzer
Golden Retriever
Chesapeake Bay retriever
Brittany Spaniel
Australian Shepherd
Malamute
English Setter
Skye Terrier
Old English Sheepdog
Maltese
Petit Basset Griffon
Beagle
Dalmatian
Rhodesian Ridgeback
Shetland Sheepdog
Siberian Husky
Borzoi
Doberman Pinscher
Cocker Spaniel

Clinical signs are quite variable and depend in part on the age of the dog at the time a deficiency in thyroid hormone develops. Clinical signs may also differ between breeds. For example, truncal alopecia may dominate in some breeds, whereas thinning of the haircoat dominates in other breeds. In adult dogs, the most consistent clinical signs of hypothyroidism result from decreased cellular metabolism and its effect on the dog’s mental status and activity.

Most dogs with hypothyroidism show more mental dullness, lethargy, exercise intolerance or unwillingness to exercise, and a propensity to gain weight without a corresponding increase in appetite or food intake. These signs are often gradual in onset, subtle, and not recognized by the owner until after thyroid hormone supplementation has been initiated. Additional clinical signs of hypothyroidism in dogs typically involve the skin, less commonly, the neuromuscular system.

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Primary esophageal sarcomas in dogs are often due to Spirocerca lupi. Primary esophageal carcinomas are of unknown etiology in dogs and cats. Leiomyomas are found at the lower esophageal sphincter in older dogs. Thyroid carcinomas and pulmonary alveolar carcinomas may invade the esophagus in dogs. Squamous cell carcinomas are the most common esophageal neoplasm in cats.

Dogs and cats with primary esophageal tumors may be asymptomatic until the tumor is far advanced, and these animals are diagnosed fortuitously when thoracic radiographs are obtained for other reasons. Regurgitation, anorexia, and/or fetid breath may occur if the tumor is large or causes esophageal dysfunction. If the esophagus is involved secondarily, clinical signs may result from esophageal dysfunction or tumor effects on other tissues.

Plain thoracic radiographs may reveal a soft tissue density in the caudal lung fields. These tumors may be difficult to radiographically discern from pulmonary lesions and usually require contrast esophagrams to make this distinction. Esophagoscopy easily finds intraluminal and intramural masses or strictures and is sensitive in finding extraluminal masses causing esophageal stricture (i.e., the endoscopist will not be able to normally distend the esophageal lumen). Retroflexing the tip of an endoscope while it is within the stomach is the best method of identifying lower esophageal sphicter leiomyomas and leiomyosarcomas in dogs and cats.

Not much a clinician can do for treatment of esophageal neoplasms in dogs and cats. Surgical resection is rarely curative (except for leiomyomas at the lower esophageal sphincter) because of the advanced nature of most esophageal neoplasms when they are diagnosed. Resection may be palliative though. Photodynamic therapy may be beneficial in dogs and cats with small superficial esophageal neoplasms. For all those reasons, the pronostic for dogs and cats with esophageal neoplasms is usually poor unfortunately.

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Allergies in dogs are basically an immune system overreaction. The nasal cavity is an uncommon primary site for allergic disease in dogs and it has not been well characterized yet. However, dermatologists provide anecdotal reports of atopic dogs rubbing the face (possibly indicating nasal pruritus) and experiencing serous nasal discharge, in addition to dermatologic signs. Dog allergies are generally considered to be a hypersensitivity response within the nasal cavity and sinuses to airborn antigens. Other antigens are capable of inducing a hypersensitivity response as well, and thus the differential diagnoses must include parasites, other infectious diseases and neoplasia.

Dogs with allergies experience sneezing and/or serous mucopurulent nasal discharge. Signs may be acute or chronic. Careful questioning of the owner may reveal a relationship between signs and potential allergens. For instance, signs of dog allergies may be worse during certain seasons; in the presence of cigarette smoke; of after the introduction of a new brand of furniture or fabric in the house.

Dog allergies treatment

Removing the offending allergen from the dog’s environment is the ideal treatment for dog allergies. When this is not possible, a beneficial response may be achieved with antihistamines. Chlorpheniramine can be administered orally. Glucocorticoids can be used if antihistamines are unsuccessful. If treatment is effective, the dog’s allergy signs will generally resolve within a few days. Medication is continued only as long as needed to control the signs.

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Signs and symptoms of rabies in dogs.

Rabies virus infection usually produces fatal encephalomyelitis in dogs and cats. The source of rabies infection is generally considered to be the bite of an infected animal that has rabies virus in the saliva. Bats, racoons, skunks, and foxes most commonly serve as the source of rabies exposure.

Rabies in dogs and cats can have a wide range of clinical signs, making it difficult to differentiate from other acute, progressive encephalomyelitis syndromes. Because of its public health significance, rabies should be on the list of differential diagnoses considered in every animal with rapidly progressing neurologic dysfunction.

In naturally occurring rabies in dogs and cats, the initial signs may include behavior changes of depression, dementia, or aggression. Excessive salivation, difficulty swallowing, and multiple cranial nerve deficits are usually seen, suggesting brainstem disease. Ataxia and rear limb paresis progressing to flaccid quadriparesis are common. There may be a history of contact with a known rabid animal. Animals may shed rabies virus in the saliva for up to 14 days before the onset of clinical signs. The incubation period from the time of the bite to the onset of clinical signs is extremely variable (1 week to 8 months). However, once neurologic signs are seen, the disease is rapidly progressive, with death occurring within 7 days in most animals.

Any unvaccinated animal with an acute, rapidly progressive course of neurologic disease should be considered a rabies suspect and handled with caution. There is no feature specific to rabies in dogs and cats. Dogs and cats should receive their first rabies vaccine after 12 weeks of age and then again 1 year later. Subsequent boosters are administered every 1 to 3 years, depending on the vaccine used and local public health regulations. Rarely, soft-tissue sarcomas have developed in cats at the site of rabies virus prophylactic inoculation.

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Lyme Disease in Dogs – Canine Lyme Disease

Lyme disease in dogs, or Lyme neuroborreliosis, resulting from infection of the CNS by the spirochete Borrelia burgdorferi, has been reported occasionally in dogs. Most affected dogs have had concurrent polyarthritis, lymphadenopathy, and fever. Signs of neurologic system involvement have include aggression, other behavior changes, and seizures.

There may be an increase in anti-B. burgdorferi immunoglobulin compared with a paired serum titer, indicating intrathecal antibody production in dogs with Lyme disease. Lyme neuroborreliosis, a well-documented manifestation of Lyme disease in humans, should be considered in the differential diagnosis of disease involving the CNS in dogs from endemic regions. Early antibiotic treatment may be effective, but it is important to select an antibiotic that is thought to act against the spirochete and that is capable of reaching high concentrations.