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<strong>Canine</strong> <strong>Chronic</strong> <strong>Inflammatory</strong> <strong>Rhinitis</strong><br />

Rebecca C. Windsor, DVM*, and Lynelle R. Johnson, DVM, PhD, DACVIM †<br />

<strong>Chronic</strong> inflammatory rhinitis is commonly found in dogs with chronic nasal disease and is<br />

characterized by lymphoplasmacytic infiltrates in the nasal mucosa in the absence of an<br />

obvious etiologic process. The pathogenesis of lymphoplasmacytic rhinitis remains unknown.<br />

Animals respond poorly to antibiotics, oral glucocorticoids, and antihistamines,<br />

making primary infectious, immune-mediated, or allergic etiologies unlikely. Aberrant immune<br />

response to inhaled organisms or allergens may induce inflammation in some<br />

animals. Common clinical signs include nasal discharge, sneezing, coughing, epistaxis,<br />

and stertor. Diagnosis is made by performing a thorough history, physical examination,<br />

radiography or advanced imaging (via computed tomography or magnetic resonance imaging),<br />

rhinoscopy, and nasal mucosal biopsy to rule out primary etiologies of nasal<br />

discharge. Treatment strategies have included various antibiotics, antihistamines, oral and<br />

inhalant steroids, nonsteroidal antiinflammatories, and antifungal medications. Some dogs<br />

may respond partially to doxycycline or azithromycin, although it is unclear whether<br />

response is related to antimicrobial or antiinflammatory properties of these drugs. Hydration<br />

of the nasal cavity through nasal drops or aerosols may limit nasal discharge, and some<br />

animals may improve with inhalant (but rarely oral) glucocorticoids.<br />

Clin Tech Small Anim Pract 21:76-81 © 2006 Elsevier Inc. All rights reserved.<br />

Keywords rhinitis, nasal, canine, inflammatory, lymphoplasmacytic<br />

The most common causes of chronic nasal discharge in<br />

dogs include nasal neoplasia, fungal rhinitis, and lymphoplasmacytic<br />

rhinitis (LPR), also referred to as inflammatory<br />

rhinitis. Other causes of chronic nasal disease include<br />

nasal foreign body, rhinitis secondary to dental disease, parasitic<br />

rhinitis (Pneumonyssoides caninum), and primary ciliary<br />

dyskinesia. Idiopathic LPR is recognized with increasing frequency<br />

in the canine population and may be more common<br />

in certain geographic locations. Diagnosis is made via histopathologic<br />

identification of a lymphoplasmacytic infiltrate<br />

in the nasal mucosa with exclusion of specific causes of<br />

chronic inflammation. An effective therapeutic regimen for<br />

dogs with LPR has not been established, largely because the<br />

underlying pathogenesis is still unknown.<br />

Etiology<br />

The etiology of LPR has not been determined, although infectious,<br />

allergic, and immune-mediated mechanisms have<br />

*Department of Clinical Sciences at North Carolina State University, Raleigh,<br />

NC.<br />

†Diplomate of the American College of Veterinary Internal Medicine, Department<br />

of Medicine and Epidemiology at the University of California,<br />

Davis, CA.<br />

Supported in part by the Bailey Wrigley Fund and the American Kennel Club<br />

Grant 0389, and the Joseph and Mable Howe Research Scholarship.<br />

Address reprint requests to: Department of Clinical Sciences, North Carolina<br />

State University, 4700 Hillsborough Street, Raleigh, NC 27606.E-mail:<br />

rebecca_windsor@ncsu.edu.<br />

76 1096-2867/06/$-see front matter © 2006 Elsevier Inc. All rights reserved.<br />

doi:10.1053/j.ctsap.2005.12.014<br />

been suggested. LPR may have a multifactorial etiology in<br />

some dogs and/or different etiologies in different dogs, making<br />

it difficult to develop general treatment guidelines.<br />

Primary Infection<br />

Primary bacterial infection of the nasal cavity is rare, and no<br />

single infectious organism has been identified in dogs with<br />

LPR. However some dogs respond anecdotally to certain antibiotics<br />

including doxycycline and azithromycin, leading to<br />

the speculation that certain bacterial organisms such as<br />

Chlamydophila, Mycoplasma, orBartonella could be involved<br />

in the pathogenesis of LPR. Chlamydophila is a primary upper<br />

respiratory pathogen in humans, cats, and other species. Bartonella<br />

has been associated with nasal discharge, 1 granulomatous<br />

rhinitis, 2 and epistaxis2,3 in dogs. A recent study investigating<br />

the role of infectious organisms in LPR quantified<br />

DNA loads of Chlamydophila, Bartonella, <strong>Canine</strong>-adenovirus<br />

2 (CAV-2), and Parainfluenza virus 3 (PI-3) in biopsy samples<br />

from dogs with LPR by the use of quantitative PCR, and<br />

a role for these organisms could not be established. 4 In addition,<br />

endpoint PCR was used to examine nasal biopsy samples<br />

for evidence of Mycoplasma spp. and this also failed to<br />

identify a specific pathogen in DNA extracted from formalinfixed<br />

nasal biopsy samples. 4 The poor long-term response to<br />

multiple antibiotics in dogs with LPR suggests that a primary<br />

bacterial infectious etiology is unlikely, although ongoing<br />

studies investigating serologic evidence of Bartonella in dogs


<strong>Canine</strong> chronic inflammatory rhinitis 77<br />

with LPR may provide valuable information on the role of this<br />

organism in the syndrome.<br />

Table 1 Common Clinical Signs in 37 Dogs with Idiopathic<br />

<strong>Rhinitis</strong> 5<br />

Secondary Infection<br />

Secondary bacterial infection is common in dogs with<br />

chronic nasal disease, which may explain the transient response<br />

to antibiotics seen in some dogs with LPR. Nasal<br />

cultures from dogs with LPR yield mixed bacterial growth of<br />

normal nasal flora including Staphylococcus, Streptococcus,<br />

Escherichia coli, Proteus, Pasteurella, Corynebacterium, Bordetella,<br />

and Pseudomonas. 5-7 A recent study demonstrated no<br />

significant difference in bacterial DNA loads among dogs<br />

with LPR, fungal rhinitis, and nasal neoplasia; however, all<br />

three disease groups had significantly higher bacterial loads<br />

than did healthy control dogs. 4 Accumulation of bacterial<br />

organisms in dogs with chronic nasal disease could result<br />

from mucus trapping and decreased nasal mucosal defense<br />

mechanisms.<br />

Role of Fungal Organisms<br />

Aspergillus and Penicillium spp. are common inhabitants of<br />

the canine nasal cavity, 6 and a positive fungal culture can be<br />

found in the absence of primary fungal rhinitis. Candida,<br />

Trichosporum, and Cladosporidium have also been cultured<br />

from dogs with LPR. 5 In the study assessing molecular con -<br />

tent of paraffin-embedded nasal tissue from dogs, higher fungal<br />

DNA loads were reported in dogs with LPR than in<br />

healthy control dogs and dogs with nasal neoplasia. 4 Mucus<br />

trapping and decreased nasal defense mechanisms alone cannot<br />

explain this difference because dogs with nasal neoplasia<br />

would be expected to have similar mucosal compromise to<br />

dogs with LPR. Further research is required to determine the<br />

significance of increased fungal DNA in dogs with LPR. Fungal<br />

hypersensitivity characterized by an aberrant immune<br />

response has been identified in human chronic rhinosinusitis<br />

(CRS) patients. 8-14 Humans with CRS exhibit a humoral and<br />

cellular (Th1 and Th2) response to airborne fungi. 8 T-cell<br />

sensitization to fungus leads to production of T-helper 2<br />

cytokine release, namely Interleukin-5. 11 Fungal hypersensitivity<br />

in humans appears to be characterized by IgG3 rather<br />

than IgE production, suggesting that the hypersensitivity is<br />

not a true allergic response, 8,12 although humans with CRS<br />

do exhibit a predominantly eosinophilic infiltration. 13 In humans,<br />

the quantity of fungal DNA does not correlate with<br />

disease severity. 15 Further research is needed to assess the<br />

immune response of affected dogs to resident fungal organisms.<br />

Allergy<br />

There is some speculation that respiratory allergy may manifest<br />

with signs of chronic rhinitis as is seen in humans, although<br />

evidence of allergic rhinitis as a recognized disease<br />

entity in dogs has yet to be established. It is possible that dogs<br />

with LPR exhibit a heightened immune response to inhaled<br />

environmental allergens; however, no published studies to<br />

date have demonstrated an allergic inflammatory pattern in<br />

dogs with naturally occurring LPR. Experimentally, nasal<br />

congestion has been induced using ragweed pollen in Beagle<br />

colonies, 16-18 Th2 immune response was identified in the peripheral blood<br />

mononuclear cells of three dogs with rhinitis. 19 Nasal mucosal<br />

biopsies were not collected from dogs in these studies so it<br />

is not known whether lymphoplasmacytic infiltration characterized<br />

the disease. Dogs with LPR generally respond<br />

poorly to antihistamines and glucocorticoids, making an allergic<br />

etiology unlikely.<br />

Immune-Mediated<br />

The initial report describing LPR suggested that the disease<br />

was likely immune-mediated because three of five dogs in<br />

that study demonstrated a favorable response to glucocorticoids.<br />

and evidence of allergic response to house dustmite<br />

antigen characterized by increased IL-4 expression and<br />

20 Historically, in our experience, most dogs with LPR<br />

have exhibited a poor response to oral glucocorticoid treatment,<br />

suggesting that a primary immune-mediated etiology<br />

is unlikely. Cats with nasal inflammation exhibit a heightened<br />

Th1 immune response that is more pronounced as inflammation<br />

becomes more severe 21 Mucopurulent, mucoid, or serous<br />

35/37 (95%)<br />

nasal discharge<br />

Sneezing<br />

Coughing<br />

Epistaxis<br />

Reverse sneezing<br />

Stertor<br />

Ocular discharge<br />

Pawing at the muzzle<br />

19/37 (51%)<br />

15/37 (41%)<br />

15/37 (41%)<br />

6/37 (16%)<br />

5/37 (14%)<br />

4/37 (11%)<br />

2/37 (5%)<br />

; however, information is<br />

not available in dogs. Further studies evaluating the immunoregulatory<br />

patterns in the nasal mucosa of dogs with LPR<br />

are required to determine the role of immune dysregulation<br />

in disease.<br />

History<br />

Important historical features in dogs with chronic rhinitis<br />

include duration and progression of clinical signs, character<br />

and laterality of nasal discharge, and response to previous<br />

medical therapies. LPR can be seen in any breed but occurs<br />

most commonly in large-breed dogs. There is no apparent<br />

age or sex predilection. Duration of clinical signs may range<br />

from weeks to years at the time of diagnostic evaluation. The<br />

most common clinical signs include nasal discharge, sneezing,<br />

coughing (likely secondary to pharyngitis caused by<br />

swallowing irritant nasal secretions), and episodes of epistaxis<br />

(Table 1). Although signs related to LPR are often bilateral,<br />

many dogs with LPR have unilateral or lateralizing<br />

signs on presentation. Laterality of clinical signs based on<br />

history and physical examination correlates poorly with computed<br />

tomography, rhinoscopy, and biopsy findings. 5 Therefore,<br />

while unilateral nasal discharge is classically considered<br />

more typical of nasal neoplasia, fungal rhinitis, foreign body<br />

rhinitis, or an oronasal fistula, LPR remains a consideration,<br />

and all dogs with unilateral nasal discharge historically or on<br />

physical examination should be evaluated for bilateral nasal<br />

disease. Other clinical signs of LPR may include reverse<br />

sneezing, stertor, ocular discharge, and pawing/rubbing at<br />

the muzzle.


78 R.C. Windsor and L.R. Johnson<br />

Dogs with LPR typically have a history of poor or transient<br />

response to medical treatment. Many animals demonstrate<br />

little improvement with antibiotics, antihistamines, and glucocorticoids<br />

alone or in combination, while some demonstrate<br />

a transient response with return of clinical signs when<br />

medications are discontinued.<br />

Physical Examination<br />

The most common physical examination findings in dogs<br />

with LPR include fresh or dry nasal discharge or crusting<br />

around the nares. Most animals have mucoid or mucopurulent<br />

discharge, but hemorrhagic or serous discharge may be<br />

seen. Nasal airflow should be assessed using a microscope<br />

slide or cotton ball wisp. When assessing the patency of airflow,<br />

each nostril should be manually occluded to watch for<br />

a stress response, indicating occluded nasal airflow in the<br />

contralateral nostril. Nasal airflow is normally preserved in<br />

dogs with LPR, since obstruction would be more typical of a<br />

mass lesion.<br />

Facial palpation is often unremarkable in patients with<br />

LPR, which may be helpful in differentiating it from fungal<br />

rhinitis and nasal neoplasia, where facial pain is more common.<br />

Dogs with nasal neoplasia may also exhibit facial or<br />

skull deformity, which is not seen in dogs with LPR. Ocular<br />

retropulsion should be performed to detect retrobulbar<br />

masses or abscesses as a cause for nasal discharge. Nasal<br />

planar depigmentation may rarely be noted in dogs with<br />

severe and long-standing discharge associated with LPR but<br />

is more commonly exhibited in dogs with fungal rhinitis or<br />

immune-mediated dermatologic diseases such as discoid lupus<br />

erythematosus. Assessment of regional lymph nodes is<br />

important in animals with nasal discharge due to the tendency<br />

for neoplastic processes to metastasize locally. Lymph<br />

nodes are often enlarged in dogs with LPR or fungal rhinitis,<br />

but aspiration cytology reveals a reactive inflammatory process<br />

rather than neoplasia.<br />

Diagnostic Evaluation<br />

Laboratory Evaluation<br />

Complete blood count, chemistry panel, and urinalysis are often<br />

unremarkable in patients with chronic rhinitis. Dogs with epistaxis<br />

should be evaluated for clotting abnormalities by performing<br />

a platelet count OSPT, APTT, and BMBT to rule out coagulopathies,<br />

thrombocytopenias, and/or thrombocytopathias.<br />

Dogs presenting primarily for epistaxis should also have blood<br />

pressure measured for detection of systemic hypertension.<br />

Imaging Techniques<br />

Radiography has been used in some cases to help differentiate<br />

LPR from nasal neoplasia but has become less popular due to<br />

the availability of superior imaging techniques. Some dogs<br />

with LPR have radiographic evidence of lucent foci and multifocal<br />

lesions, which are not typically seen in dogs with nasal<br />

neoplasia. 22 Neoplastic lesions are more likely to invade - sur<br />

rounding bone22 ; however, neoplastic lesions without obvi -<br />

ous osteolysis may be difficult to differentiate from chronic<br />

rhinitis cases as both diseases cause soft-tissue opacification.<br />

Although one study identified the absence of frontal sinus<br />

Figure 1 Computed tomographic images through the rostral nasal<br />

cavity of two dogs with idiopathic LPR. In the panel on the left,<br />

soft-tissue or fluid opacity is noted between nasal turbinates and is<br />

worse on the right than on the left. In the panel on the right, more<br />

extensive soft-tissue or fluid opacity is noted bilaterally.<br />

involvement on radiographs as a positive predictive indicator<br />

for LPR compared with neoplasia, 22 a recent study showed<br />

that a high percentage of dogs with LPR have frontal sinus<br />

fluid accumulation. 5 LPR is difficult to differentiate from -fun<br />

gal rhinitis via radiography as both can cause turbinate destruction<br />

and frontal sinus accumulation.<br />

Recent studies have demonstrated that computed tomography<br />

(CT) is more sensitive and specific than radiography in<br />

differentiating LPR, nasal neoplasia, and fungal rhinitis. 23-25<br />

The most common CT findings in dogs with LPR include<br />

fluid accumulation within the nasal passages, soft-tissue<br />

opacification, turbinate destruction, frontal sinus accumulation,<br />

and gas pocketing 5 (Figs. 1 and and 2 Table 2) Imaging<br />

abnormalities noted on CT are often diffusely distributed<br />

throughout the nasal cavity, but rostral or caudal localization<br />

may be observed. Turbinate destruction tends to be less severe<br />

in dogs with LPR compared with dogs with nasal neoplasia<br />

or fungal rhinitis. 23 Dogs with nasal neoplasia com -<br />

monly exhibit a soft-tissue density with extensive turbinate<br />

destruction, while those with fungal rhinitis exhibit extensive<br />

turbinate destruction and hyperlucency of the nasal passages. 23<br />

Magnetic resonance imaging (MRI) is another excellent<br />

imaging modality for the nasal cavity, providing superior<br />

soft-tissue detail compared with CT. However no studies to<br />

date have compared the sensitivity and specificity of CT and<br />

MRI for differentiating causes of chronic nasal disease, and<br />

CT is currently the most popular imaging technique due to its<br />

lower cost compared with MRI.<br />

Rhinoscopy<br />

Rhinoscopic evaluation of patients with chronic nasal disease<br />

is essential. For complete assessment of the nasal mucosa and<br />

turbinates, a rigid or flexible endoscope is required. The most<br />

common rhinoscopic features in dogs with inflammatory rhinitis<br />

include mucoid or mucopurulent discharge, hyperemic,<br />

edematous, and/or friable nasal mucosa, and mild turbinate<br />

atrophy or destruction 5 (Fig. 3 and Table 3). Indistinct softtissue<br />

opacities noted on CT can be visualized rhinoscopically,<br />

allowing differentiation among nasal masses, nasal polyps,<br />

and mucus plugs. Fungal plaques or nasal mites may<br />

also be observed rhinoscopically, thus providing a primary<br />

etiology for nasal discharge. Representative biopsy specimens<br />

are best obtained by rhinoscopic identification of areas of


<strong>Canine</strong> chronic inflammatory rhinitis 79<br />

Figure 2 Sequential computed tomographic images through the<br />

frontal sinus of a dog with idiopathic LPR. The top panel shows<br />

soft-tissue or fluid opacification in the left frontal sinus. In the next<br />

7-mm slice, the frontal sinus has filled more completely and an<br />

air–fluid meniscus is present, suggesting that fluid is filling the<br />

frontal sinus.<br />

significant nasal mucosal pathology and visualization of the<br />

area sampled for histopathology.<br />

Other diagnostic techniques to perform after rhinoscopy<br />

are examination of the nasopharyngeal region using a<br />

dental mirror or retroflexed endoscope to look for nasopharyngeal<br />

polyps and dental probing to rule out oronasal<br />

fistula or dental disease as a cause for unilateral nasal<br />

discharge.<br />

Histopathology<br />

Nasal biopsy samples of dogs with chronic, idiopathic, inflammatory<br />

rhinitis are characterized by a primarily lymphoplasmacytic<br />

infiltrate, but concurrent neutrophilic or less<br />

commonly eosinophilic infiltrate may also be seen. Epithelial<br />

Table 2 Computed Tomography in 33 Dogs with Idiopathic<br />

<strong>Rhinitis</strong> 5<br />

Normal 4/33 (12%)<br />

Unilateral lesions 8/33 (24%)<br />

Bilateral lesions 21/33 (64%)<br />

Fluid accumulation 27/33 (82%)<br />

Soft-tissue opacification 25/33 (78%)<br />

Plaque-like lesions 24/33 (73%)<br />

Turbinate destruction 23/33 (70%)<br />

Gas pocketing 23/33 (70%)<br />

Frontal sinus opacification 14/33 (42%)<br />

Figure 3 Rhinoscopic image of a dog with idiopathic LPR. Marked<br />

hyperemia and mucus accumulation are evident. (Color version of<br />

figure is available online.)<br />

changes are usually mild but may include epithelial hyperplasia<br />

and erosion. Turbinate remodeling or destruction can<br />

also be evident. The majority of dogs with unilateral clinical<br />

signs have bilateral nasal mucosal pathology, and severity of<br />

inflammation between the two sides of the nasal cavity often<br />

varies.<br />

Culture and Cytology<br />

Obtaining a positive culture of bacterial and/or fungal organisms<br />

in dogs with inflammatory rhinitis is not uncommon<br />

and likely reflects normal nasal mucosal flora or secondary<br />

infection rather than primary infectious rhinitis. Culture results<br />

from the rostral nasal cavity may differ from the caudal<br />

nasal cavity. 26 Similarly, brush or lavage samples from super -<br />

ficial epithelium may not adequately reflect bacterial and fungal<br />

infiltration into the nasal mucosa. When culture is desired,<br />

collection of a deep nasal lavage using a protected<br />

catheter brush or submission of a nasal biopsy sample for<br />

culture should be considered.<br />

Nasal mucosal cytology may be used to identify fungal or<br />

neoplastic lesions in some cases; however, cytology has poor<br />

sensitivity and specificity compared with histology in nasal<br />

mucosal samples27-29 and is often unreliable for detecting<br />

chronic changes. 29<br />

Table 3 Rhinoscopic Findings in 37 Dogs with Idiopathic <strong>Rhinitis</strong><br />

5<br />

Normal 1/37 (3%)<br />

Unilateral lesions 7/37 (19%)<br />

Bilateral lesions 21/37 (57%)<br />

Mucoid or mucopurulent discharge 29/37 (78%)<br />

Hyperemic, or inflamed mucosa 26/37 (70%)<br />

Mucosal edema 8/37 (22%)<br />

Turbinate atrophy, destruction, or loss 8/37 (22%)<br />

Hemorrhage or blood clots 5/37 (14%)<br />

Mucosal friability 4/37 (11%)


80 R.C. Windsor and L.R. Johnson<br />

Treatment<br />

No effective treatment regimen for LPR has been established;<br />

therefore, animals are commonly treated with a variety of<br />

medications including antibiotics, antiinflammatory drugs<br />

(glucocorticoids: oral or topical, or nonsteroidal antiinflammatory<br />

drugs), antihistamines, and antifungal medications.<br />

Antibiotics<br />

Dogs with mucopurulent nasal discharge likely have some<br />

degree of secondary bacterial contamination. Antibiotic treatment<br />

in these animals may help to reduce the severity of the<br />

nasal discharge and alter the character of discharge from<br />

mucopurulent to serous, but complete sustained resolution<br />

of nasal discharge is rarely achieved. Most nasal bacterial<br />

infections are susceptible to multiple antibiotics. Some dogs<br />

respond well to doxycycline (3 to 5 mg/kg PO twice per day),<br />

which may be attributed partially to its antiinflammatory<br />

effects. Macrolides such as azithromycin (5 mg/kg daily for 5<br />

days, then twice weekly) have also been effective in some<br />

dogs.<br />

Although the long-term response to antibiotics has not<br />

been reported, it is unlikely that such treatment results in<br />

cure of disease. Extended courses of suppressive antibiotic<br />

therapy or intermittent treatment with such drugs may be<br />

required for control of signs. If the severity of the nasal discharge<br />

worsens when antibiotics are discontinued, it is advisable<br />

to reinstitute therapy with the same antibiotic to avoid<br />

development of antibiotic resistance by use of multiple antibiotics.<br />

Anti-<strong>Inflammatory</strong> Agents<br />

Oral glucocorticoids have not proven effective in treating<br />

most dogs with LPR; therefore, long-term use of oral steroids<br />

should be avoided because of systemic side effects. Topical<br />

nasal steroid drops may be applied if the dog will tolerate<br />

administration. Topical glucocorticoid sprays such as fluticasone<br />

propionate have been used with variable success in human<br />

chronic rhinosinusitis patients 30-32 and have shown an -<br />

ecdotal promise in some dogs and cats with chronic nasal<br />

discharge. Although typically used to treat lower airway disease,<br />

metered dose inhalers (MDIs) containing fluticasone<br />

may also benefit animals with rhinitis as the drug must first<br />

pass through the nasal passages before reaching the lower<br />

respiratory tract. Aerosolized steroids can be administered<br />

using MDIs attached to a spacer and tightly fitting facemask.<br />

The MDI must be well-shaken before actuation into the<br />

spacer, and the animal must take 8 to 10 breaths without<br />

panting to carry the drug into the respiratory tract. A commercially<br />

available spacer with facemask designed for cats<br />

(Aerokat) works well in brachycephalic dogs. For larger,<br />

dolicocephalic dogs, human pediatric spacers must be obtained,<br />

and appropriate face masks must be acquired from a<br />

local pharmacy or anesthetic supply company.<br />

Nonsteroidal antiinflammatory drugs may be somewhat<br />

efficacious in reducing nasal inflammation in certain cases.<br />

These drugs are also sometimes used in feline nonspecific<br />

rhinitis, when it is unclear whether an infectious etiology<br />

might be present. The most commonly used drug is likely<br />

piroxicam. Like all nonsteroidal agents, this drug can be as-<br />

sociated with gastrointestinal effects associated with GI ulceration<br />

and with renal dysfunction. When used at 0.3 mg/kg<br />

PO daily in healthy animals, it is unlikely to have untoward<br />

side effects, although owners should be instructed to watch<br />

for anorexia, vomiting, or abdominal pain.<br />

Antihistamines<br />

Antihistamines are occasionally used in LPR dogs, although<br />

response is typically poor, and the sedative effects of some<br />

antihistamines may outweigh any therapeutic benefit. Also,<br />

antihistamines may have the undesirable side effect of drying<br />

nasal secretions and worsening mucus accumulation. However,<br />

if sneezing and nasal discharge worsen seasonally and<br />

an inhaled environmental allergen is suspected, an antihistamine<br />

trial may be employed.<br />

Antifungal Therapy<br />

A few dogs with LPR have been treated empirically with<br />

topical antifungal medications (clotrimazole, enilconazole)<br />

to treat a possible undiagnosed fungal rhinitis; however, improvement<br />

in clinical signs was not noted. 5 Response to oral<br />

antifungals has not been reported. Variable results have been<br />

reported in human chronic rhinusinusitis patients with suspected<br />

fungal hypersensitivity. Nasal amphotericin B resulted<br />

in deterioration of symptoms in one study, 33 while<br />

proving safe and effective in another. 34<br />

Other Therapies<br />

Some dogs with LPR may present with signs of reverse sneezing.<br />

Reverse sneezing occurs in response to irritation of the<br />

nasal mucosa, which may be caused by inhaled irritants or<br />

occasionally by the nasal mite, P. caninum. Dogs that exhibit<br />

reverse sneezing should be treated empirically with ivermectin<br />

(or milbemycin in Collie breeds) to rule out parasitic<br />

infestation as a cause of rhinitis before pursuing aggressive<br />

diagnostics.<br />

Increasing nasal hydration through the use of topical saline<br />

drops or with saline inhalation or nebulization can aid in<br />

evacuation of the nasal cavity. Dogs are variably tolerant of<br />

having saline nasal drops administered to the nasal cavity,<br />

but this is the least expensive alternative for liquefying nasal<br />

secretions and encouraging removal from the nasal cavity.<br />

Conclusion<br />

<strong>Inflammatory</strong> rhinitis is commonly found in dogs with<br />

chronic nasal disease. The etiology of this disorder remains<br />

unknown and may involve different pathogenic mechanisms<br />

in different dogs with chronic nasal disease. Some dogs may<br />

exhibit an aberrant immune response to commensal fungal<br />

organisms or other inhaled pathogens or irritants. The diagnosis<br />

of LPR requires a thorough history and physical examination,<br />

advanced imaging (CT or MRI), rhinoscopic evaluation,<br />

and biopsy. Culture and cytology may occasionally<br />

prove useful in differentiating LPR from other causes of rhinitis<br />

(ie, fungal rhinitis and neoplasia). The poor response to<br />

treatment with antibiotics, glucocorticoids, and antihistamines<br />

makes LPR a frustrating condition to treat. Current<br />

recommendations to be considered include the use of doxycycline<br />

or azithromycin for their antiinflammatory as well as


<strong>Canine</strong> chronic inflammatory rhinitis 81<br />

antibacterial effects, and trial therapy with piroxicam. Owners<br />

should be advised that antibiotics only treat secondary<br />

bacterial infections and nasal discharge will likely return<br />

once antibiotics are discontinued. Use of multiple antibiotics<br />

should be avoided. Oral corticosteroids have shown little<br />

therapeutic benefit and should be avoided due to unwanted<br />

systemic effects. However, inhalant corticosteroids may be<br />

effective in some patients. Further research is required to<br />

identify the pathogenesis of LPR with the aim of developing<br />

an effective treatment regimen.<br />

References<br />

1. Henn JB, Liu CH, Kasten RW, et al: Seroprevalence of antibodies<br />

against Bartonella species and evaluation of risk factors and clinical<br />

signs associated with seropositivity in dogs. Am J Vet Res 66(4):688-<br />

694, 2005<br />

2. Pappalardo BL, Brown T, Gookin JL, et al: Granulomatous disease<br />

associated with Bartonella infection in 2 dogs. J Vet Intern Med 14(1):<br />

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