68 | The step-by-step guide to fungal rhinitis for veterinary nurses

PodcastRespiratory
Written By Laura Jones

Today, we’re rounding off our mini-series on nasal disease by diving
into a condition we’re about to see a lot more of - fungal rhinitis.

 


I’m sitting at HQ recording this at the start of April. The sun is shining, it’s both warm and rainy, and I’m patiently awaiting the start of fungus season, knowing that in a month or so, I’ll be helping pull a LOT of fungus out of dog noses, drilling into heads, and going through a LOT of canesten.

And, as gross as it is, it’s SO satisfying. So let’s get prepared for these patients together by discussing what fungal rhinitis is, the patients we see it in, and how we manage it (as well as the skills we can use with these patients as nurses).

What is fungal rhinitis, and which patients get it?

As the name suggests, fungal rhinitis occurs when a fungal infection in the nose or sinuses leads to inflammation and upper respiratory signs. There are lots of different fungal species that cause rhinitis, but the two we most commonly see are aspergillosis and cryptococcosis.

Aspergillosis primarily affects dogs, particularly large-breed, dolichocephlaic (long-nosed) breeds like Siberian Huskies and German Shepherds.

Cryptococcosis is more commonly seen in cats, often affecting the nasal passages, central nervous system, skin or other organs.

Since canine aspergillosis is far more prevalent, we’ll focus primarily on that in this episode.

Let’s take a look at aspergillosis first.

Aspergillosis is the term for infection with a fungi of the Aspergillus species. In most cases, Aspergillus fumigatus is the particular species, though other species are being recognised increasingly commonly.

Aspergillus is found worldwide and thrives in soil and organic matter. It isn’t always pathogenic - in fact, if you want to feel REALLY gross right now, one paper I read mentioned that humans can inhale up to 200 Aspergillus spores per day - with our respiratory defence mechanisms and immune system taking care of them for us.

In dogs, problems arise when the fungal spores bypass these defences, typically in immunocompromised patients. Dogs can either ingest or inhale fungal spores, leading to colonisation and infection.

This infection is most commonly seen in the nose and sinuses, though disseminated forms, where the infection spreads to other tissues, are also possible.

Patients with disseminated aspergillosis can develop limb pain and lameness, spinal pain and neurological signs, uveitis, coughing, and chronic vomiting alongside lethargy and anorexia.

Thankfully, though, most patients have localised sinonasal infection only, limiting their clinical signs to things like sneezing and nasal discharge.

Aspergillus infection is usually seen in large-breed, dolichocephalic (long-nosed) breeds like Siberian Huskies and German Shepherds, though it can theoretically affect any breed.

What signs do we see in aspergillosis patients?

After inhalation, the fungi colonise the nose, causing nasal pain, ulceration and sneezing alongside nasal discharge. Discharge may be unilateral or bilateral, purulent or haemorrhagic.

Nasal depigmentation is also common in dogs with nasal aspergillosis. Fungal toxins in the nasal discharge can damage the pigment-producing cells within the nose, causing discolouration on the inside of the nares. Black-nosed dogs will often have an area of pink or white depigmentation.

Fungi are also really destructive - and in particular, they love to eat bone. Dogs with fungal rhinitis will often have severe nasal turbinate destruction, changes to their facial conformation, or even damage to their cribriform plate - the plate of bone separating the nose and the central nervous system. If the cribriform plate is damaged, spread to the CNS is possible, causing neurological signs.

In severe cases, frontal bone osteomyelitis can also occur, causing infection, bone pain, pyrexia and lethargy.

Usually, patients present relatively stable with a medium-term history of sneezing and nasal discharge, with evidence of nasal depigmentation or bony changes on examination.

So you think your patient could have aspergillosis. What next? 

Our approach to diagnosing these patients is similar to other nasal diseases - we’re going to need to perform diagnostic imaging, rhinoscopy, and sampling of the nose. However, we might need to take a peek into the sinuses too - particularly if you’ve got a strong suspicion of fungal rhinitis but the nose comes up empty on rhinoscopy.

Diagnostic imaging is our first port of call.

Once you’ve performed any relevant pre-anaesthetic tests and checked your patient has sufficient platelets +/- clotting ability for rhinoscopy and sampling, it’s time to perform imaging.

Like many other nasal diseases, CT is our modality of choice. It usually reveals a dramatic loss of the nasal turbinate bones, since the fungus can quickly destroy them.

Fungal granulomas can also be seen on imaging (though not always), and we must look for them not just in the nose but in the sinuses too. In some cases, the nasal cavity will be free of infection, with only the sinuses affected.

CT also allows us to examine the cribriform plate and determine whether it is intact. This is particularly important as topical antifungal treatments are often used inside the nose, and we need to ensure the cribriform plate is intact before we use these.

After we’ve CT’d our patient, the next step is rhinoscopy.

The throat is packed, and a rigid endoscope is inserted into the nose. Saline flushing and suction are used as needed to improve visualisation. In most cases, fungal granulomas are visible - these look like whitish, yellowish, greenish and greyish ‘mushrooms’ growing inside the nose.

Debriding as much of this material as possible is vital - our goal is to remove those granulomas and then prevent regrowth with antifungal treatment.

Biopsies of the nose are then taken for histology, bacterial culture and fungal culture as needed.

What about if there’s sinus involvement?

If you suspect your patient has sinus involvement, you may well need to go and look there. The frontal sinuses are bony, air-filled spaces above the nose (caudal to the eyes).

They are accessed (if needed) either by advancing a flexible endoscope through the nose into the sinuses (if possible), or by trephining the sinus and inserting a rigid endoscope directly into them.

Sinus trephination is performed aseptically using a Jacob’s chuck and a pin (this is as close to surgery as you’ll see us get in medicine!) to create a hole in the frontal bone. The rhinoscope can then be inserted and used to visualise any fungal plaques inside the sinus, and these are suctioned, flushed and debrided if present.

What other tests will we perform?

Aspergillus serology testing is also available but of limited use - it’s a poorly sensitive test, meaning that false negative results are common, and rhinoscopy and sampling will still be needed in suspected cases.

If a patient has disseminated aspergillosis, cytology, fungal culture and serology of the affected body fluids (CSF, BAL samples, urine, etc) is recommended.

Ok, so you’ve got a diagnosis. What about treatment?

Treating sinonasal aspergillosis is both fun AND frustrating. We’re going to treat them topically in most cases, under the same anaesthetic as their rhinoscopy - but repeated treatments are often needed, and they can be time-consuming.

After you debride as much of that fungus as possible, you’ll instill topical clotrimazole (canesten) to ‘soak’ the nose +/- sinuses as needed.

When doing this, we must be careful to prevent aspiration - we usually use a combination of well-cuffed ET tubes and throat packs to do this. You can also place a Foley catheter into the nasopharynx and inflate the balloon to block off the back of the nose if needed.

We also use clotrimazole cream, rather than solution, in most cases. This is thicker, meaning it’ll sit in the nasal cavity for longer. It can make it challenging to administer, though, since you have to force it through a syringe. To make it easier:

  • Warm the cream up by placing the tube in a jug of hot water

  • Don’t try and administer it through the endoscope channel (even if it’s going through an aspiration catheter - it’ll be too narrow)

Instead, I like to insert a cut-down 10-12F (the largest you can fit) rigid urinary catheter into the nose or sinus and administer the cream through this. It’s much easier and avoids getting cream everywhere!

We instill as much cream as we need to fill the nose and then leave it to work for around an hour, periodically turning the patient to maximise penetration. This has around an 80% success rate, so repeated procedures every 2-4 weeks are often required until signs improve and no fungal plaques are seen on rhinoscopy. Systemic treatments are available but are not as effective.

What about nursing considerations for these patients? How will we care for them?

Keeping these patients clean and comfortable is our biggest consideration. They’re usually stable and present for intermittent rhinoscopy and clotrimazole soaking procedures as needed, so our care is mostly aimed at supporting them during their procedure and in recovery.

Prioritise a slow, calm recovery.

These patients are prone to awful recoveries. They often wake up in a bit of a panic, feeling really congested and sneezing clotrimazole everywhere. Recovering them slowly, with a low dose of sedation on board if needed, can be very helpful. We like to keep ours recovering quietly in our procedure room until they’re calm and quiet, and then return them to their kennel.

Keep them comfortable.

These patients can feel uncomfortable - they often have bone pain and feel very congested with all of that fungal material (and clotrimazole, if you’ve soaked them!) - picture the worst sinus infection you could have, and you’ve got an idea of how they probably feel.

Good analgesia (using a combination of opioids, anti-inflammatories and ideally local anaesthetic techniques) is important. If you’re anaesthetising them for a rhinoscopy, an infraorbital nerve block can help desensitise the nose ahead of examination and sampling.

Prevent Clotrimazole aspiration and monitor respiration carefully.

Clotrimazole aspiration is a very real risk in these patients. They need to be protected from aspiration carefully throughout their anaesthetic and monitored for any respiratory changes indicating potential aspiration on recovery.

Fungal rhinitis cases are time-consuming and, at times, frustrating but ultimately really rewarding medical nursing cases. They need time, patience and repeated treatments, but seeing these patients go from feeling really congested and uncomfortable to symptom-free and comfortable again is so satisfying.

We’ve covered quite a bit today, so let’s recap. Sinonasal aspergillosis is by far the most common cause of fungal rhinitis in dogs. Affected dogs (usually long-nosed, large breed dogs) inhale or ingest aspergillus fungal spores, which colonise the nose, sinuses or both, leading to infection. 

Sneezing, nasal discharge, bone pain and destruction and nasal depigmentation are common, and we diagnose these patients with a combination of diagnostic imaging, endoscopy and sampling. Treatment is mostly topical, under anaesthetic, and repeated treatments are needed - providing us with lots of opportunities to give great care to these patients!

Did you enjoy this episode? If so, I’d love to hear what you think. Take a screenshot and tag me on Instagram (@vetinternalmedicinenursing) so I can give you a shout-out and share it with a colleague who’d find it helpful!

Thanks for learning with me this week, and I’ll see you next time!


References and Further Reading

Laura Jones
Next

67 | 5 key considerations to manage chronic rhinitis confidently as a vet nurse