Nasal mites in dogs: symptoms, transmission and treatment

Overview

The scientific name of the canine nasal mite is Pneumonyssoides caninum. The same parasite is also known as Pneumonyssus caninum. It occurs worldwide. Nasal mites are reported particularly often in Scandinavia.

A typical nasal mite infection does not usually make a dog generally unwell. However, symptoms can interfere with hunting and tracking work. In a Swedish post-mortem study, around 20% of the dogs examined carried nasal mites. In Norway, infection was found in 7% of 250 dogs examined post mortem in 1993.

Symptoms are usually mild and mainly affect the upper airways. The parasite has also been described in silver foxes.

Causes

Nasal mites move along the surface of the nasal lining. Their long legs extend beyond the edges of the body. Mites have also been found in the frontal sinuses. Their movement can cause itching and irritation of the lining.

Female mites are around 1–1.5 millimetres long. They are around 0.6–0.9 millimetres wide. The body is oval and yellowish. The parasite is visible to the naked eye. Males and larvae are smaller than females.

Adult mites have four pairs of legs. Larvae have three pairs. The parasite's complete life cycle is unknown.

Direct transfer between dogs is a likely route of transmission. Indirect transmission through the environment is also possible. However, the exact routes of transmission are not fully understood. Rhinitis can make the nasal lining red and swollen.

Mites have been recorded moving at 1 centimetre per second.

Risk factors

Infections occur in dogs of all ages and breeds. One observation found more infections in dogs over three years old than in younger dogs. The same observation found more infections in large dogs than in small breeds. In the Norwegian post-mortem group, there was no significant association between infection and age, sex or breed distribution.

The infected Norwegian dogs ranged from four months to ten years old. They represented 14 breeds. Ten were male and eight were female. In Sweden, 48 dogs treated because of symptoms ranged from eight months to 14 years old. Fifteen were hunting dogs and 33 were companion or working dogs.

Whether infection can pass from a pregnant bitch to her puppies is uncertain.

Typical symptoms

Signs consistent with nasal mites include:

• More frequent sneezing or snorting.

• Reverse sneezing.

• Nasal discharge.

• Head shaking.

• An itchy muzzle and rubbing it on the ground.

• A reduced sense of smell or losing a scent trail more easily.

• Sometimes, nosebleeds.

Owners may overlook infection in a dog with mild symptoms. In a tracking dog, the first change noticed may be losing a trail during training or competition. Symptoms can be intermittent rather than continuous. Other nasal diseases can cause similar signs.

During a reverse sneezing episode, the dog rapidly draws air in through the nose. The dog often stands with the neck extended and the head tilted back. The mouth usually stays closed and the nostrils flare. An episode can last from seconds to minutes.

Complications and consequences

Infection may be associated with chronic sinusitis. More frequent tonsillitis has also been observed in dogs with nasal mites. A reduced sense of smell can hinder hunting and tracking work. The outlook after treatment for confirmed nasal mite infection is usually excellent.

Nasal tissues usually show no changes visible to the naked eye at post-mortem examination. Severe swelling and discharge associated with rhinitis can narrow the nasal passages. Treatment for nasal mites is estimated to be over 85% effective.

In the Norwegian post-mortem study, sinusitis was also found in 60% of the 16 dogs with moderate or heavy infestations.

Symptoms do not always disappear completely after antiparasitic treatment. Another upper airway disease present at the same time may explain persistent symptoms. In the Swedish group of 48 dogs selected on symptoms alone, 35 dogs, or 73%, were symptom-free at eight weeks.

Diagnosis at the vet

Distinguishing the symptoms from other nasal diseases

Upper airway symptoms may suggest nasal mites, but symptoms alone do not confirm infection. A nasal foreign body can cause similar signs. A nasal tumour is another possible diagnosis. Dental disease or an abnormal opening between the mouth and nose may explain nasal discharge.

Fungal infection is another possible cause of persistent nasal symptoms. Other chronic inflammatory disease may also be associated with inflammation of the nasal lining. Further investigation is needed if treatment for presumed nasal mites does not reduce symptoms.

Excitement can also trigger reverse sneezing. Pulling hard against a lead can cause the same reflex. Eating or drinking quickly are other possible triggers. An elongated soft palate may be associated with similar signs in a short-muzzled dog.

In rhinitis, watery discharge can become mucoid because of secondary bacterial infection. Pus in the discharge can be associated with inflammatory cells accumulating in the lining. Tracking ability is difficult to assess during a consultation.

Finding a mite confirms the diagnosis

A mite visible to the naked eye can sometimes be seen in a dog's nostril. Parasites may be found in nasal mucus or watery discharge. Occasionally, a mite is sneezed out with nasal discharge. However, owners rarely manage to see mites living inside the nose. Mites have sometimes been seen emerging from a nostril during anaesthesia.

Rhinoscopy and nasal flushing are the most useful investigations. Rhinoscopy can reveal mites moving inside the nasal cavity. A flexible endoscope can also examine the rear openings into the nasopharynx. To do this, the endoscope can be passed through the mouth and behind the soft palate.

Nasal flushing is usually performed under general anaesthesia. A cuffed tube placed in the windpipe protects the airways during the procedure. Saline is used for flushing. The collected fluid is examined under magnification for mites.

A negative flushing sample does not rule out nasal mites. Mites may be in sinuses that are difficult to reach. Infection is confirmed by identifying the parasite during rhinoscopy or in flushing fluid. Finding mites does not establish whether they explain all the dog's nasal symptoms.

Further investigations depend on the symptoms

Computed tomography shows the structures of the nasal cavities and sinuses. If imaging is performed, it precedes rhinoscopy, flushing or biopsy procedures that alter the tissues. Otherwise, changes caused by the procedure may be confused with the original disease changes.

A blood count and blood biochemistry can help investigate other diseases present at the same time. Nosebleeds may warrant checking platelet numbers and blood clotting. Blood antibody tests have no undisputed benefit in diagnosing nasal mites. An increase in eosinophils alone is not a useful confirmatory test.

Treatment

The vet plans antiparasitic treatment

Nasal mites are treated with prescription medicines prescribed by a vet. If the symptoms fit nasal mites but no parasite is seen, the vet may consider a treatment trial. Antiparasitic medicines belonging to the macrocyclic lactones may be used for this infection.

Antiparasitic medicines have been used as tablets and spot-on treatments.

Examples include milbemycin, selamectin and moxidectin. The risk of adverse effects is considered when choosing a medicine. Ivermectin can cause serious adverse effects, particularly in Collies and related breeds. An optimal general treatment regimen for nasal mites has not yet been established.

Monitoring symptoms during treatment

If snuffling does not improve within about a week of starting treatment, the dog is investigated further for other causes. In the Swedish group of 48 dogs, 19 were symptom-free at four weeks. At that point, 29 still had reverse sneezing.

Thirteen dogs still had symptoms at eight weeks. In ten of them, symptoms had decreased but had not stopped. The other three also remained symptomatic. Owners noticed mild tiredness in two dogs.

One dog's sneezing increased one to two weeks after treatment began. All 48 dogs had been diagnosed on symptoms alone, without mites being confirmed. Outcomes were assessed from owners' observations.

In a small experimental study, 12 Beagles were infected. Six received selamectin. The other six formed an untreated control group. No mites were found at post-mortem examination of the treated dogs.

Five of the six control dogs still had mites. The outcome was assessed 39–46 days after experimental infection. A clinical response to treatment is different from the absence of mites demonstrated at post-mortem examination.

Symptom assessments by the Swedish dogs' owners were not consistent with one another.

Prevention

Nasal mites can pass between dogs in close contact. Shared sleeping areas are a possible route of indirect transmission. Shared retrieving objects may also increase the risk of infection. Dogs in the same household are treated at the same time, even when some have no symptoms. Selamectin and the imidacloprid–moxidectin combination are considered potentially able to prevent infection.

Mites have been reported to survive outside the host for 19 days, and for up to three weeks in a humid environment.

In dry surroundings, mites die within a day or two.

Canine nasal mites pose no known infection risk to humans.

In humid conditions, survival has been observed both at room temperature and at refrigerator temperature.

Important for dog owners

Record when snorting occurs and whether it is continuous or episodic. In a tracking dog, also monitor the ability to find and follow a familiar trail. Reduced scenting performance may be the first sign noticed.

Tell the vet about other dogs in the household and any symptoms they have. A hunting dog with snuffling symptoms should be examined well before the hunting season begins. Dogs can usually use their sense of smell better after the parasites have been eliminated.

Keep the dog calm during a nosebleed. Do not put cotton wool or other material into the nostril. Touching the inside of the nose with material can increase sneezing and worsen bleeding. Persistent bleeding or difficulty breathing requires immediate veterinary assessment.

Do not give medicines for a nosebleed without veterinary advice.

You can take a short video of an intermittent snorting episode to show at the consultation.

Frequently asked questions

Does reverse sneezing always mean nasal mites?

Reverse sneezing is consistent with nasal mites, but other diseases can cause it too. A nasal foreign body, tumour or dental disease may explain similar symptoms. Seeing a mite during rhinoscopy or in flushing fluid confirms infection. Computed tomography can examine the structures of the nasal cavities and sinuses.

Can mites still be present after a negative flushing sample?

A negative flushing sample does not rule out infection. Mites may be hidden in sinuses that are difficult to reach. Rhinoscopy can also be used to try to find the parasite. If suspicion is strong, the vet may consider a treatment trial. Nasal flushing is usually performed under general anaesthesia.

How quickly should symptoms improve?

If snuffling does not improve within about a week of starting medication, the dog is investigated for other causes. Of the 48 Swedish dogs treated on the basis of symptoms, 35, or 73%, were completely symptom-free at eight weeks. Their infections had not been confirmed by finding mites.

Can a symptom-free pet dog carry infection?

A dog without symptoms can also carry nasal mites. The parasite probably spreads through close contact between dogs. Other dogs in the household are therefore treated at the same time as the symptomatic dog. Canine nasal mites are not considered a known infection risk to humans.

Could a poor sense of smell be caused by nasal mites?

Nasal mites can reduce a dog's sense of smell. A working dog may lose a familiar trail or fail to find it at all. Using the sense of smell usually becomes easier once the parasites have been eliminated. However, persistent nasal symptoms may be associated with another upper airway disease present at the same time.