13 Canine Rhinitis

Rhinitis is inflammation of the nasal mucous membranes. Infiltrates of inflammatory cells, including neutrophils, lymphocytes, plasma cells, eosinophils, macrophages, and mast cells, occur in response to organisms, foreign bodies, parasites, allergens, and immune-mediated disorders.

2. What type of dogs most often present with rhinitis?

Nasal cavity anatomy varies significantly over the range of head shapes, from dolichocephalic to brachycephalic breeds. Mesocephalic and dolichocephalic breeds are the ones that most often present with nasal discharge. Brachycephalic breeds less frequently have rhinitis but they are more likely to have congenital malformations that predispose them to other respiratory diseases.

3. What are the clinical signs of rhinitis?

Nasal discharge is the most common clinical sign of rhinitis. This discharge can be unilateral or bilateral. Sneezing, head shaking, reverse sneezing, pawing at the mouth/nose, nasal stridor, or dyspnea may be present.

4. What types of nasal discharges are observed?

Discharges may be serous, mucoid, mucopurulent, or hemorrhagic. Because goblet cells are distributed throughout the respiratory epithelium of the nasal cavity, serous or mucoid discharges are more common; a mucopurulent discharge is typical with chronic rhinitis or may be a sign of secondary bacterial infection. It is important to establish that a nasal discharge is originating in the nasal cavity and not from lower portions of the respiratory tract; if the discharge is from the lower tract, examination limited to the nasal cavity will be unrewarding and potentially dangerous if it delays diagnosis of a serious condition such as congenital ciliary dysfunction or bronchopneumonia.

5. What diagnostic tests are typically performed first in a dog that presents with any form of rhinitis?

There are three phases of diagnostic testing.

Phase 1

A complete history and physical examination are essential in the initial evaluation of rhinitis. Placing a feather, cotton fibers, or other lightweight material in front of the nasal openings and watching for signs of airflow can be used to identify complete or partial nasal obstruction. Examination of the external nasal cavity and oral cavity, as much as possible, is a critical step. Obtaining specimens of the nasal discharge for cytologic examination is also helpful. Either a direct impression of the nasal discharge or a swab of the rostral nares may help identify nasal mites (Pneumonyssoides caninum). Microbiological cultures are unlikely to yield reliable information, are difficult to interpret, and can be expensive at this point. If the animal has recently received an antibiotic medication, however, bacteria may not be present. A complete blood count, biochemistry profile, and urinalysis are necessary when a specific cause cannot be identified from the initial examination.

6. Can a therapeutic trial be initiated?

A therapeutic trial can be initiated if the client cannot afford additional diagnostic procedures or advanced diagnostic tests are not available. The trial therapy can be decided upon based on the results of a complete history (i.e., seasonal event, chronicity, etc.) and physical examination (oral examination) combined with the results of nasal discharge cytology. The effects of the trial therapy should be closely followed and the treatment adjusted based on the response.

Phase 2

A complete oral and nasal examination, including radiography, under anesthesia, is necessary to identify tooth root infections or fractures (periodontal probing), neoplasms, or foreign bodies. A dental mirror may help with examination of deep oral tissues. A rigid otoscope can be used for initial examination of the external nares and nasal area. Rhinoscopy, with a flexible endoscope, is an effective procedure to examine the mucosa and collect specimens of nasal tissues to culture for bacterial and fungal pathogens, if an infection is suspected. Another option is nasal flushing with sterile saline. Flushing saline from the pharyngeal region toward the nares will allow cellular material and debris to be collected on cotton gauze squares from which a specimen for culture can be taken. This procedure, which does not usually cause hemorrhage, is best performed after complete nasal examination but before tissue collection.

When tissue biopsy specimens are necessary they should be collected from both nasal passages. Taking a biopsy specimen from the nasal mucosa often causes hemorrhage because of the extreme vascularity of the submucosa, and the bleeding makes subsequent examination of the mucosa impossible. Therefore both nasal cavities must be examined completely before biopsy specimens are obtained. Cold saline infusion can be used to decrease the amount of bleeding during acquisition of biopsy specimens. When a “blind” biopsy is performed, it must be stressed that the biopsy instrument must not pass beyond the medial canthus of the eye, to avoid penetrating the cribiform plate during this procedure. Skull radiographs are critical to the success of this procedure, to measure distances for obtaining “blind” biopsies.

7. What other tests are available to assist with the diagnosis of nasal cavity disease?

Phase 3

Computed tomography (CT) and magnetic resonance imaging (MRI) can be used to diagnose nasal cavity disease. CT and MRI are much more expensive than plain radiography; however, they offer a more complete assessment. CT and MRI may help localize lesions before rhinoscopy is performed but often cannot provide a definitive diagnosis. Previous trauma may have caused a sequestrum with a subsequent secondary bacterial infection. This may be identified on radiograph examination, CT, or MRI.

Rickettsial infections such as Ehrlichia, Anaplasma, Rocky Mountain spotted fever (RMSF), or Bartonella may cause rhinitis. Testing for these pathogens can be performed in any phase of the examination.

8. Do biopsy results always provide definitive answers?

No, they do not always provide a definitive diagnosis. Cellular infiltrates may change with chronicity. Occasionally, different inflammatory cells may replace the initial cellular infiltrates and mask the initial inflammatory response. For example, a biopsy specimen from a dog with long-term allergic rhinitis may demonstrate lymphoplasmacytic inflammation due to the chronicity of the disorder. Also, biopsies in cases of infection, foreign body, or neoplastic disease may occasionally fail to help in reaching a definitive diagnosis because histologic changes may have occurred over the course of the disease. Therefore often a second series of biopsies is recommended if the initial diagnosis appears incorrect. It is important that both nasal passages are examined and undergo biopsy even if the nasal discharge is only unilateral.

9. Can rhinitis be cured?

Yes and no, depending if a definitive cause can be identified. Often, rhinitis is frustrating to manage, however, because a definitive diagnosis cannot be established and empiric treatment may be unsuccessful. This leaves the veterinarian and owner searching for an answer while the nasal discharge continues. Controlling the disorder may be a more reasonable goal than curing the disorder. Again, this depends on whether the cause of the rhinitis can be identified.

BACTERIAL RHINITIS

Charles W. Brockus

10. What clinical signs are present in dogs with bacterial rhinitis?

Typically, dogs with bacterial rhinitis have a mucopurulent discharge, and they may also sneeze or paw at the nose. Other signs include coughing, retching, constant swallowing, signs of pain in the nasal region, open-mouth breathing, noisy breathing, and/or ocular discharge. Depending on the chronicity and exact cause of the bacterial rhinitis, epistaxis may also be present if the infection has invaded the deeper mucosal membrane.

11. Is bacterial rhinitis common?

Rhinitis caused specifically by bacteria is rare. Secondary infection of the mucous membranes or turbinates in dogs with allergy (hypersensitivity), foreign bodies, neoplasms, immune disorders, oronasal fistula, boney sequestration, or colonization with fungal organisms is common.

12. What are the bacteria most often associated with primary bacterial rhinitis?

Pseudomonas aeruginosa, Pasteurella multocida, and Staphylococcus spp. are the bacteria that most frequently cause primary bacterial rhinitis. These bacteria have also been cultured from the respiratory tracts of animals without signs of clinical disease.

13. Should I culture the nasal discharge?

Culturing the external nasal discharge is neither a high-yield procedure nor a good prognostic test. However, microbiological culture of material from the deeper recesses of the nasal cavity may be helpful. Culture and sensitivity testing will help identify bacteria species present and their susceptibility to antibiotics. Even if the bacteria present are secondary to another disease, they can establish themselves and cause further damage. Also, culture and sensitivity testing of deep nasal tissue may be helpful when an infection does not respond to initial antibiotic therapy or to identify the causative organism for initial management.

14. What changes are observed on skull radiographs with bacterial rhinitis?

Abnormalities on skull radiographs of the nasal passages usually are limited to diffuse increase in opacity associated with mucinous material within the nasal cavity. However, osteolysis or turbinate destruction may also be seen. In more chronic cases bone destruction can occur but other causes, including fungal infection or neoplasia, must be eliminated.

15. How do I treat bacterial rhinitis?

Acute cases may resolve without antibiotics if a primary condition is identified and treated. Often a broad-spectrum antibiotic is used to treat bacterial rhinitis. Culture and sensitivity testing of deep tissues are helpful to identify the specific bacteria involved and to determine the most effective antibiotic. If a broad-spectrum antibiotic is used and the disease is non-responsive, culture and sensitivity testing are necessary. In this case one must be concerned that the bacterial infection is secondary to another condition. Treating secondary bacterial rhinitis with antibiotics can be helpful in reducing the volume and character of the nasal discharge, but resolution of clinical signs is problematic.

16. How long should I treat with antibiotics?

In mild cases a 7- to 10-day course of antibiotic therapy will be adequate. If the infection is chronic, with osteolysis or involving deep tissues, generally, long-term treatment is necessary and complete resolution of the nasal discharge may not be achieved.

17. What antibiotics are appropriate?

Because a chronic infection may have involved bone or cartilage, drugs with anaerobic activity, including clindamycin or amoxicillin (amoxicillin, amoxicillin/clavulanic acid), are often used. Clindamycin has good activity against Gram-positive and anaerobic bacteria and penetrates into deeper tissues. Metronidazole has also been used with success and has other beneficial qualities, including antiinflammatory and T-lymphocyte modulator activity. Azithromycin, doxycycline, enrofloxacin, and marbofloxacin also have been used with success.

18. What is the prognosis?

The prognosis in a case of primary bacterial rhinitis can be excellent, depending on the chronicity of the infection and the extent to which bone has become involved. The deeper infections associated with osteolysis can be much more difficult to treat. Secondary bacterial rhinitis has an excellent prognosis if the primary cause can be identified and treated effectively.

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Tags: Canine Internal Medicine Secrets

Jul 31, 2016 | Posted by admin in INTERNAL MEDICINE | Comments Off

Veterian Key

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Canine Rhinitis

Phase 1

Phase 2

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Veterian Key

Fastest Veterinary Medicine Insight Engine

Canine Rhinitis

Phase 1

Phase 2

Phase 3

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