We all know there’s more to a cat than it’s coat and stroking the luxuriant fur of a puss full of purr is one of the great pleasures of feline ownership.  It’s not surprising, then, when a bald patch appears, often with an open sore, owners seek our advice early on. This is where the ‘pet investigations’ begin! The first thing is a really good look for unwelcome visitors. Harvest mites in autumn, fleas and ticks all the year round. Harvest mites are tiny, orange-red critters that collect in small colonies on ear tips and toes. They can cause intense irritation.  Fortunately, the nuisance is temporary – they’re only parasitic in August and September, being free-living the rest of the time.  

Fleas are the commonest cause of skin problems in cats. Sometimes by their presence, more often, by triggering an allergic reaction.  The paradox here is a flea-allergic cat (or dog) rarely has a living flea on it to be found.  The answer to this lies in the short life-span of a flea on an allergic animal as it is often regularly treated with anti-flea products and the over-grooming response of the host keeps the numbers down.  The problem here is the itchy allergic reaction continues after eliminating the culprit. So, when we look for a living flea, we often don’t find one.

Cats do like to over-activate a particular sort of white blood cell (the eosinophil, pronounced ee-oh-sin-o-fil). When behaving itself, it’s a useful defence against parasites, particularly internal worms.  For a proportion of cats, the eosinophils become far too enthusiastic and their capacity to produce excessive inflammation in the skin, the lung and the gastro-intestinal tract are well-recognised. 

Obviously for the not-so-humble flea, the skin is the target tissue and the result of over-zealous eosinophil activity is often irritation enough for the sandpaper tongue of the cat to not only remove fur but layers of skin as well.  This really looks quite shocking and the poor puss must be uncomfortable with the incessant itchiness.  Luckily, improved flea control (paying particular attention to the home environment where flea eggs may be lurking) and our old friends, the steroids prednisolone and dexamethasone, often provide if not a cure, at least good management of a bad state-of-affairs.

Now, I mentioned that the Ying-Yang eosinophil is also involved in allergic reactions that can affect not only the skin but the lung and the gut as well.  Cats, as you may well know, can suffer from asthma.  Like humans, inhaling an allergen triggers an allergic response. This causes airway inflammation and constriction, resulting in coughing and shortness of breath. Often affecting young to middle-aged cats (2-8 yrs) estimates suggest 1% of domestic moggies and up to 5% of Oriental cats suffer from asthma to varying degrees.  With patience and practice, we can successfully treat cats with an inhaler or nebuliser but sometimes we may also need steroid tablets.  

We all know about the legendary ability of dogs to exhibit vomiting and diarrhoea as symptoms. Usually, due to eating something disgusting.  But when a cat presents similarly, the cause is likely to be different – fresh is best for the discerning feline.  For kittens, a virus or a parasite is usually responsible.  For older cats, although there are many things to consider, inflammatory bowel disease (IBD) caused by over-activated eosinophils (amongst others) in response to parasites or a food intolerance/allergy is always a consideration.  In addition, cats that ingest fleas/excessive hair can trigger a gut response similar to what’s happening in the flea-allergic skin.  The result, a very upset tummy that needs some investigation before confirming a diagnosis.

But here’s the rub; ‘pet investigations’ are expensive! The trouble is, without them we are in the dark. Treatment becomes trial-and-error, which can waste time and money and cause frustration for owners, patients and vets. There is some good news though! The skin is nicely accessible to our probing and biopsies are quite easy, although a short anaesthetic is often necessary.  We can’t say the same for the gut and the lung. However, a blood test to count eosinophils in the circulation can point us in the direction of an allergic/inflammatory cause to the problem, be it respiratory or gastro-intestinal.  In general, whenever possible, we perform our pet investigations by diagnostic tests. Taking it step-by-step means if we diagnose early on in the process, treatment can start with minimal delay and expense.