Well, hello. My name is Doctor Steven White. I'm here at the School of Veterinary Medicine, University of California, and our topic today is working up the Pur course, specifically allergies, urticaria, and ectoparasites.

Let's start with an allergy that is sometimes overlooked in horses. That's atopic dermatitis. Now, what exactly is atopic dermatitis?

It's an allergic reaction to environmental antigens. a good way of, of thinking about this and also Sending it to owners is that this is a little like hay fever in human beings, except most of the time, the target organ of the in the horse and our other domestic animals is usually not the respiratory tract, but rather it's the skin. This seems to be mediated by IgE antibodies, although there also could be in the horse something called a barrier dysfunction, that is where the stratum corneum, the outermost layer of the skin of the epidermis doesn't function the way it should as far as keeping allergens out of the body and preventing them from progressing into the dermis and setting off an allergic reaction.

So all, all of these, the mediation by IgE antibodies and the potential barrier dysfunction, is basically what separates an atopic horse from a healthy horse. So what are these environmental allergens? Well, pollens, moulds, dust and storage mites.

And when I say dust and storage mites, I don't just mean mites that might be associated with, with the storage, but the dust mites, house dust mites, even though it, it seems unusual or or odd to think about house dust mites, in fact, being a problem. With an outside, basically an outside animal like the horse, but in fact, it's been shown that house dust mite and their allergens, which are often derived from their faeces, are actually not uncommon in blankets, and other materials in the barn. Now, these allergens usually gain access through the percutaneous route.

Now, that means, as I said before, that there may be a problem with the stratum corneum barrier to the outside. It also in the respiratory route, but we're not going to talk about that today, but, some horses will have problems with both routes, but, most The time when we're dealing with skin problems, it's a percutaneous route that's utilised by these allergens. These allergens bind to sensitised IGE which are sitting on the mast cell.

This causes degranulation and release of inflammatory substances from the mast cell, causing the pruritus that we see, or, and or causing the urticaria that can be related to atopic dermatitis. Now, the clinical signs of atopic dermatitis are certainly pruritus, which creates secondary alopecia, excoriations like kinification that is thickening and hyperpigmentation of the skin. The face and the trunk are probably most commonly affected, but it can be seen on just about any part of the body.

Atopic dermatitis can also cause urticaria. These can either be wheels, that is hives or less commonly actually linear urticaria, either horizontal or vertical. It commonly coexists coexists with insect hypersensitivity.

These horses have what sometimes is called an allergic personality, so it's not unusual to see them having an allergy to insects, i.e., fly bites, problems, as well as atopic dermatitis in much the same way that dogs with atopic dermatitis frequently also have flea allergy.

Now, again, the clinical signs based on a review of some 70 plus equids that we saw here at UC Davis as well as looking at some of the other recent studies, the mean age of onset was about 9 years. Of course, I ages can fall on either side of that. Here at UC Davis, Arabian.

I seem to have something of a genetic predilection that's been shown in at other places as well. You may or may not see a seasonality. That is to say, it depends on where you are practising.

If you are in a truly temperate climate, such I would say as Great Britain, then you may see more seasonality as such. That in the warm weather with pollens, you may see more of a problem with this, unless of course the animal has a problem, mainly with moulds, in which case you may see a problem more in the winter. Here at the University of California, we don't have as well defined seasons or our seasonality was less than 25% of the horses.

And what's very interesting with the horse, it may be unique to to equids, is that while 52% of these horses had urticaria, 15% were pruritic, and a third of them had both urticaria and pruritus. So basically, you can have, at least in the horse, non-pruritic urticaria that is caused, that is a a sign of atopic dermatitis. Now, these are some Mild cases, and we can see a little on the left, a little bit of alopecia and hyperpigmentation on the, face, and on the right, some hyperpigmentation and mild alopecia around the eyes.

More, more severe cases on the left, pruritus, associated, around the face, and on the right, a mule who has some pruritus and alopecia both around the head and as we can, see when we look around the eye as well. This is a horse that has, excuse me, has alopecia due to pruritus not only on the face as we can see the alopecia there, but also on the going down into the neck. And a severe case, the horse was rubbing against the side of the barn, the side of the stalls, and extremely pruritic here in this atopic horse.

This is a horse that primary concern was not the, not pruritus so much, but it was the hives that we can see, chronic urticaria. And we'll talk about other causes of urticaria in, in just a few minutes. Another case, obviously, this animal has a widespread urticaria, the area that was the area that you see that was clipped and thus induced alopecia, if you will, and that's due to surgical and other intervention reasons, but it rather clearly shows the extent of the urticaria in this utopic courses.

And this is one of these unusual linear urticaria. We can see that it is occurring primarily vertically but also somewhat horizontally as the as the urticaria sweeps toward the shoulder. This is a miniature donkey that was seen by colleagues at Tufts University in New England and we can see severe evidence of severe pruritus, urticaria, alopecia, hyperpigmentation, in this animal.

So how do we diagnose atopic dermatitis? Well, it is a diagnosis of exclusion. We look and see if we have a seasonality.

We look at our clinical signs and then we want to rule out as best we can, ectoparasites, contact dermatitis, and anything else that we might think would be contributory to the pruritus. If these things have been ruled out or if we're able to rule them out to the best of our ability and we still are confronted with a pruritic or and or an urticarial horse then we usually say that the animal has atopic dermatitis. So if we're, if the owners are interested in hypersensitization, that is, if they're interested in putting the animal through either injectable or oral allergens in order to desensitise or hyposensitize the horse.

That's when we have a choice. We can either do intradermal skin testing, or refer it to for intradermal skin testing, or we can do serologic testing. Now, at here at UC Davis, we, we, we have shown that there are no difference between the type of test and the success of hypersensitization.

Whether the horse was had intradermal skin testing or had serologic testing or had both, the success rates, which we'll talk about in just a minute, were about the same. Now, one word of caution. Serologic testing for food allergies is, to put it kindly fraught with problems.

This is twofold. One is that, food allergy is actually extremely rare in herbivores. I think in the last, almost 40 years of, Of doing, doing a dermatology in horses.

I think I've seen maybe 5 cases that I felt confident. Truly had, a, food allergy. And the other is that serologic testing for food allergy, has the conclusion, must have the, the basis that food allergy like atopic dermatitis is governed by or modulated by IGE and there's no evidence to that effect in the horse.

So this is a horse who obviously has lots of positive reactions, although has some negative ones, 1234, 5th row down, but this would be a horse that certainly has some positive reactions to allergens. Now in the United, sorry, in UC Davis here, in California, these are the common allergens that we have found both using intradermal testing and serum testing. The top lines of dermatophagoides, horia and the terranicinus, those are house dust mites that I mentioned before, are found.

In in blankets in some cases we see various trees, Bermuda grass, a mould, and then at the bottom it says deer fly or chrysop species. It's important to remember that this doesn't really test for allergy to the bite of the fly, but rather to its exoskeletons which are part and parcel of the environment. So, if we use hypersensitization, what we found here was 84% of owners saw improvement and almost 60% of horses managed with only hypersensitization, and another 9% controlled with hypersensitization and the drug Doxepin.

This, this percentage is number one, roughly equivalent to what we see in our small animal, small animals with hypersensitization, and also was similar to a more recent study, done, from the eastern United States. Just to, just a word about oral hypersensitization, these are sublingual drops. These are drops that are placed as much as possible under the, tongue of the horse.

Several manufacturers, have the, you have the possibility of, of, of purchasing this from several manufacturers. I just listed the two that, we commonly use here at UC Davis, and the results in horse. Are at least as successful as the injections.

However, when you explain this to, to owners, it's important to tell them that the injections, while initially every other day for the first month, then drop back to generally once a week to every 10 days, whereas the drops should be used on a twice a day basis. So it depends on how often the horse or the trainers interact with these horses will probably be more of a, a, deciding factor as to which route. The the owners choose.

Now, certainly, there are other things that we can try. Hydroxyzine pamoate is an antihistamine, that, is, has been shown to be effective in some of our horses. Doxepin is an older antidepressant actually with antihistaminic effects.

And which one of these, the veterinarian uses, of course, will depend on, first of all, if they're available in, in the, country that you're practising in. Hydroxyzine palmo we carry here in our pharmacy, so that's usually the first one that we use. My philosophy is if there's no response within 10 days, probably time to try doxepin.

Cetirazine is actually an antihistamine that is the active ingredient of higher or the active metabolite rather of hydroxyzine pamoate. However, cetirazine in the United States comes in rather small size doses of 10 milligramme tablets. So getting enough into a horse.

Even though it's been shown to be effective, is problematic. And of course, prednisolone will usually shut down the pruritus as well as the urticaria, as well, dexamethasone or other steroids, but because they're, we all know that steroids, corticosteroids carry their own baggage of side effects. It's something I usually, I do not use on a long-term basis.

The other thing about hydroxyzine and doxepin is if this is a performance horse, one has to check with the regulations of that society or organisation to make sure that these aren't illegal from the standpoint of participation in whatever performance the horse is doing. Another drug that all that we have here is pentoxaphyle. Pentoxaphyle is a, it's kind of like a second cousin of caffeine.

It's a methyl xanthine derivative. It, rarely, and I do say rarely can cause hyper excitability in the horse just as I suppose, caffeine could. In Canada, it's a as a granulated product.

However, in the United States it is available just as a tablet. These are 400 milligramme tablets. They are not miscible in water.

You can't break them up and mix them in water. Usually what we recommend if we're going to use this is to have the owner grind it up using a mortar and pestle or something similar and then put it into molasses or peanut butter or something along those lines. As we're talking also, about, adverse effects.

Let me just say with both hydroxyzine and Doxepin, as they are antihistamines or function as antihistamines. In rare cases, the horse can be drowsy or just like a little kids sometimes given antihistamines, the horses can become jittery. Again, I see this in less than 5% of the cases that I've given these drugs to horses, but it's something to, to warn the owner about.

What about topical medications? Certainly, people who are atopic, topical medications used a great deal. oatmeal-based shampoos or washes, although the exact, way that oatmeal reduces itching is not known.

Oatmeal probably, oatmeal probably would not be particularly helpful in one of these non-pyritic urticarial cases. And Cordovan spray, which is from Verbach, it's a hydrocortisone isoppoate is one of several corticosteroid sprays available in different countries around the world. Here we have examples on the far left Aveeno, which is an oatmeal powder that then put into baths or water and applied to the animal.

And then we have three different steroid products, two from Veback, one from Dera, and I would just like to say I do not get any sort of remuneration for listing these or any other products. This is a product that, to my knowledge, is only available in the UK. It is a, a product that contains nicotinamide or as we say in, in North America, niacinamide.

Given once a month, it comes with a topical gel which is an aloe base. It's marketed for summer itch. I have no experience with this, because it's not available in the United States.

What I can say is that if one goes online, And looks at various testimonials. It seems that it does work for some horses, but certainly not for all. Certainly, anyone who is listening to this who has experience should feel free to email me and let me know what their experience has been.

Dermocent, made, a product called Essential 6 spot on, which has some mild antiritic effects, for the horse. The, idea here being that these products help the or repair the stratum corneum and, and therefore help the barrier function of these horses. Just some examples before and after.

This is a horse, a 16 year old quarter horse gelding before hypersensitization, we can see the urticaria on the left, and after 3 months of hypersensitization, the urticaria, excuse me, the urticaria has resolved. You'll recall this miniature donkey that was quite pruritic as evidenced by the alopecia crusting and ulceration. And in this case, the authors of this poster, went ahead and used cyclosporin.

Now cyclosporin is quite effective in many cases of atopic dermatitis in, people as well as in dogs and cats. It it's rather expensive to use in a 500 kilogramme horse, but this is obviously a miniature. Donkey and they were able to use cyclosporin, cost wise and eventually wean the donkey down to getting it every 3 days.

So that's atopic dermatitis, just a a word about food allergies. I think it's very rare, as I mentioned before in horses as a cause of skin disease. It happens, but I think it's probably because it's very rare in any of our herbivore species.

Now again, as I said before, there's no good blood or skin test. The only way to diagnose is to use a so-called hypoallergenic diet for 8 weeks. That means if the horse is being fed, let's say, mainly alfalfa to switch it to Timothy.

Or a, or a sugar beet based diet or some of the other or old-based diet. Something else other than what it's getting and to eliminate all supplements, which is sometimes difficult for owners to attempt. Contact dermatitis is, I think, certainly more common than food allergy.

This is because of either medications that the veterinarian is at home or home remedies, wood shavings, particularly some of the more exotic, or oily ones, which can be anything from pine to some of the tropical woods that are sometimes used as castoffs, . Looking at the horse, we can sometimes see drip marks caused by gravity. Also progressing lesions.

Here, history is very important. Progressing lesions means that you would get a history of, well, I saw, I saw this lesion on my horse, so I went ahead. And got this stuff at the tax store, brought it home, applied it, but the lesion got bigger.

So I put more of the same stuff on it and it keeps getting bigger. I can't stay ahead of it. That's a progressing lesion.

Probably, whatever was the initial cause of the skin disease is probably gone now thanks to the inflammation caused by the contact dermatitis. So here's a case when one can nicely see the drip mark there of something being put on the, if you will, the elbow of this horse and then continuing to drip down and causing alopecia and a little bit of erythema. Same thing here.

Something's sprayed or placed upon this horse and dripping down and causing those, caused by gravity drip marks. Another case, in this case, Patern dermatitis, pastor dermatitis is kind of a, a catch-all. It can be passer dermatitis can be caused by bacteria, fungi, such as ringworm, it can be caused by allergies.

Probably the most common reason that I see, passer dermatitis is due to a vasculitis. But whatever the cause is, it's probably gone or overshadowed by this topical reaction. How do I know it's a topical reaction?

Well, there are two things that are giveaways. One is a tremendous amount of thickening that's been going on here, and the other is the rather odd orange colour. Obviously something's been placed on this horse's paster.

And another case where the something has been placed on, if, if I recall correctly, it may have been betady on this following some experimental work in this horse, with, with various injections to help the, this horse's lameness. It probably, this is probably not due to the injection but rather to the, the betaadine and we can see that, presumed contact, allergy here. So how do we treat contact dermatitis?

Well, here, of course, we want to remove whatever the contact and is, if we can wash just with water to remove as much of it as possible. Prednisolone on a short-term basis is quite effective, as is interestingly, even on a longer term basis, pentoxyhyine, which has sometimes been used for contact dermatitis in people and in dogs. We now come to urticaria.

What are some causes of urticaria? Well, arthropod and venomation, which is a fancy way of saying fly bites or bee stings, or or mosquito bites, atopic dermatitis, as we mentioned before, drug reactions, occasionally we see this with dermatophytes or ringworm. There's certainly idiopathic urticaria.

Vasculitis or purpura hemorrhagica, and purpura hemorrhagica is essentially a necrotizing vasculitis and then occasionally the autoimmune disease panmphigus foliatus. So look at each of these in a little more detail. This is due to Cleoides hypersensitivity, Ciccoides being the biting gnats are sometimes called noseums.

We can see the nice doughnut type of urticaria, and by the way, you have a donut urticaria, raised plaque urticaria, large circles of urticaria, the horizontal or vertical urticaria. These do not give you a hint as to what the cause of the urticaria is. This is a drug drug drug reaction to phenobutasone, and, we can see it for reasons that are not known, and it's primarily in this case, the front half of the horse, rather dramatic as we can see.

And also, concerning because it's now involving around the eyes and the next step would be angioedema. So this horse needs treatment, and, and soon. Another drug reaction to the drug acetazolamide, that's used by the ophthalmologists.

And here we have one of the rare cases of dermatophyte, causing alopecia and and at the same time causing vasculitis, and we can see that we have the alopecia, the, the, the quintessential ring for ringworm, but we also have these raised areas and what happens and we can take a closer. Look here on the right side of the circular circular area, beginning of circular area of alopecia, we see rays almost a half moon of the urticaria, and that's the progression. It will start as urticaria, presumably due to a hypersensitivity reaction to the dermatophyte or some of its byproducts, and then usually within 2 or 3 days progress.

To circles of alopecia, the, the, the ring of the ringworm. So, what's important here is to realise that if you have chronic urticaria, it's almost certainly not due to a dermatophyte. But if you go out and the urticaria happened just yesterday or two days ago, and you're beginning to see area, look very carefully for areas of alopecia because you may be dealing with a dermatophyte.

This is vasculitis, whether we call vasculitis whether we call it urticarial vasculitis or vasculitic urticaria, it's something that, the only way to diagnose this is by biopsy to see if the horse is having vasculitis. Vasculitis can be caused by We, we see it, unfortunately we see it idiopathically, but we also can see it due to drugs, and some of the, insect bites, and, occasionally we can see it associated with other diseases as well, as I mentioned before, a purpura hemorrhagica. Just another area on the body showing the rather round areas of, of urticaria due to vasculitis.

And this is a case of pemphigus foliaceous where the urticaria has these hairs sticking straight up, very similar to the progression that we see with dermatophytes is the progression we see with pemphigus foliaceous because what will happen is that Urticaria will be there for maybe 2 or 3 days, then the hairs usually become, the hairs either fall out or more commonly we start seeing lots of crust develop which is more common with pemphigus foliacious as its main clinical sign. And so, Again, if you see a chronic urticaria, it's probably not due to pemphigus foliacious. On the other hand, if when looking at the urticaria, if it's a new, if it just came up in the last 2 or 3 days, and you see, and if you look in between the hairs or you clip some of the hair away and there's lots of crusting, you may be dealing with pimphigus foliats and a biopsy is, is warranted.

This is a an odd case of of linear urticaria again primarily or pri primarily horizontal, presumably these are often due to ectopic dermatitis, although that's not been conclusively proven in each case. You know, something that we see in small animals a lot with allergies and pruritus is otitis, and you know, does otitis in fact occur in horses and it, it, it either it's rare or it's rarely reported and it may be, may actually rare because of the anatomy of the ear canal. Or just rarely reported, and the external ear canal narrows at the junction of a membranous and an osseous sections.

Causes are Oobbi's magnini, which is the spinos ear tic, a foreign body neoplasia, and, and maybe allergies. In fact, this is a horse that had allergies. One of our former residents when she was here, saw this horse and did cytology and we can see the bacteria, the rod-shaped bacteria within the neutrophils.

And so, Went ahead, took pictures with a video otoscope. Now, obviously this is only possible really in a, in a heavily sedated or in this case anaesthetized horse, and this horse was anaesthetized for other reasons, not for this, but we can see at the top left the junction of the cartilaginous or pigmented. In the osseous non-pigmented area portion of this ear canal.

And then on the bottom left we can see the video otoscope that we use. And then what this resident did, which I thought was very clever, was to take ear wicks, which are one can buy at almost any drugstore. And there are these cotton products that are look like little columns.

She tied two of them together and she impregnated them with a ear medication, for, that was. Use for small animals is that had both a steroid and antibacterial and an anti-fungal, so-called shotgun, product, and then put that into the ear, sewed it to the ear. The horse woke up, and then 2 weeks later was, due to be anaesthetized again for the same problem.

It was some orthopaedic problem. And so then pulled out that, those, ear wicks and ear wicks are basically white cotton so you can see there's all sorts of debris. More important than pulling out the debris was the fact that that medication was able to, to slowly leach out into the ear and the ear, the otitis external was was resolved.

So, having talked about allergies, and various causes of urticaria, I now wanna switch over to culicoides, . So chilocoides, as I mentioned before, this is the noseum or the the fly, I'm sorry, the nat that is probably most responsible for allergic responses around the world. It's called Swedish, Queensland itch, those are the more printable names.

Pruritus, and it usually starts young, between 2 to 4 years of age, assuming that the animals are exposed at that time to this gnat. It's a hypersensitivity reaction to the salivary antigens, and what we can see is, a clearcut genetics have been studied in a number of different breeds. It's seasonal and temperate climates, if you're in a tropical climate, it's probably almost year-round.

This is what the organism looks like, obviously, this is very, very much blown up, so one can see it. Clinical signs, different chilioide species like to feed in different parts of the body of the horse, and in fact, there are a number of different species and they vary not only, they vary not only in where they like to feed on the horse, but also they vary due to whatever geographic area they're in. So, mane, tail, and rump, they can also, affect the ventral midline dermatitis in a diffuse pattern.

Papules, crusts, ulcers, and thickened skin are what we see. So this is from a colleague in Sweden and we can see the alopecia and hyperpigmentation here of this pony that's been rubbing at its main. And also rubbing at its tail, it's one of the differentials for tail rubbers is chicoides hypersensitivity.

Here we have ventral midline dermatitis. Not a diffuse pattern throughout. Which enables us to distinguish this from some of the other flies that other insects that like to, affect this area of the body.

A more chronic case, and here we have that hyperpigment hyperpigmentation and, and, and lichinification that we associate with chronic dermatitis. What can we do for this? Well, repellents are very effective.

Permethrin repellents, usually between 2 to 3%. Fans, in the barn are effectively the overhead or the mobile fans because these insects are weak fliers and, in fact, horses will figure out sometimes if the fan is going around, if it's a mobile fan, they will actually stand facing into it so that the flies can't get to them. Steroids, of course, to reduce the pruritus and then dresses, things to cover the horses with.

So this is a 2% product, one of many that are out there. Usually, one has to apply these more frequently than the label suggests. So every other day it would not be uncommon for us to have to use this.

This product says 10%, so you might think this would be even better, but in fact you, once you follow the directions, it comes out to 2%. Here we have the addresses again from our colleague in Sweden, showing how this covers the horse. Obviously, if this, if you're dealing with the ventral midline dermatitis, causing loosis is not going to, this particular dress is not going to be helpful.

There's one of the mobile fans. Stabling horses at sunrise and sunset is helpful because that's when these gnats are out. Ultrafine screens, 60 square inches, 60 squares per square inch.

That's, that's more fine than than mosquito netting. Remove standing water because that's where they like to breed, and then there are some questions in the literature, can we hypersensitize to kilooides? Hypersensitization to insects.

Antigens is perhaps less successful than, hypersensitization to environmental antigens. There are conflicting reports in the literature, and again, most of these horses have other allergies, other allergens are bothering them because many of them are atopic as well. This is a hornfly.

Hematobia species. Now horn flies can have a, a triangular look to them as you can see here. A little easier to see on this white horse.

And they cause ventral midline dermatitis, but focal dermatitis, as you can see here. The stable fly mixes calcitrans. It likes the front half of the horse, the, the ventral neck, the brisket, the face, the, the legs, front legs.

As we can see here on this other, horse, and we're beginning here to see some of that thickening of the skin, presumably due to a chronic irritation. And here's a bunch of the stable flies around us an ulcer. Just to give you an idea of the relative size of these creatures.

Obviously they're they're quite small. This is a black fly, sometimes called a buffalo gnat because of the hump that it, it has, and it's thorax. This fly likes the, again, the face and in between the mandibles, here we can see it on the ear of this of this animal, there, there it is.

And this is just something to remind us this horse had a fly worry primarily due to black flies and it has gone off its feet. You can see, you can begin to see its ribs and it's something to remember that chronic pruritus, chronic irritation, can affect, not only, the, the ability to ride the horse, but also just the quality of life. These large flies like horse flies or yeah deer flies, these large flies cause problems, not really with an allergy, but by just their bite.

Their bites are quite painful and they can really plague the horse, as can this mosquito, I'm sorry, this horse fly rather, shown here on a, a person. And a mosquito shown on a person as well. Mosquitoes can cause problems with pruritus as well, of course, as being vectors of various diseases.

So it's important to let the owners know about the environment. Where are these animals breeding? Kilcoides mainly standing water, although they can, in manure and decaying vegetation.

The horn fly is cattle manure the mixes, the stable fly is decaying vegetation, black flies like running water, the horse, flies, vegetation and water, and of course mosquitoes like water. So getting rid of standing water if possible, certainly cleaning up all manure, any decaying vegetation, this will help, take care of or help, limit the ability of these flies to reproduce. It's also important to know their feeding times, which unfortunately cover pretty much 24 hours, but, the culicoides, twilight to dawn, hematobia, that is to say the hornfly and the stable fly are daytime.

feeders, the, black flies morning and evening, the tabanist again, also the horse flies at daytime, mosquitoes are dusk for 2 hours past sunset. So you can see that, except, at, at night, these guys are kind of tag teaming the horse, so it's important to try to figure out which is bothering the horse and that you're dealing with. Fly predators are very interesting.

There are these tiny wasps that prey on the fly larva. They are helpful in cases of, manure, because that's where they're going to find the fly larva. They they don't do much for, flies that are breeding in water, but these are very small wasps and they don't harm animals or people, they just go after the fly larvae.

Especially stable flies, horn flies, other, flies that are, in, in manure, or in the barn floor. One can contact the laboratories that offer these, and, they usually send you the, either the, the eggs or the larval form and you place them on the the floor of the barn or wherever the manure is. So we leave flies behind now, we come to some other some other arthropods that cause problems, Coreopes, sometimes called the leg mangemite, likes the pastor and and fetlocks and in severe cases of ventral midline and infect the whole body.

Well, that tends to be uncommon. There's puritus with secondary crust and alopecia, and for reasons we don't completely understand, draught breeds seem to be predisposed. So here is an example of in, I believe this was a shire and we have a little, a little bit of erythema until we start clipping away the hair and we see the hyperpigmentation and erythema and thickening.

These horses oftentimes are rubbing their, their their patterns fed locks against each other or or the right against the left or against anything that's relatively rough. They're quite potic. This is a, another draught horse with you we can see the hyperpigmentation and alopecia, that is, coming with the purs due to the Coreopes.

And this is a severe case where we have extreme thickening of the of the skin on the pastor and and fetlock. And in fact, it's been so chronic that we now see that flies are laying their eggs there and which you're seeing their the larvae flies you're you're seeing maggots. This is a donkey that had widespread coopes infestation.

We can see it affecting not only the legs but also the the on the chest and and and on the entire trunk. Another view of this, and again, severe problems on the legs as well as on the, on the trunk and neck. Diagnosis by superficial scrapings, this is not always easy to find, so multiple scrapings may be needed.

This is what I use to scrape. I don't use a scalpel blade anymore. I use a medical grade spatula.

Again, I don't get any remuneration for mentioning these. There are a number of different flat blades micro spatulas that you can buy from scientific company warehouses. What I would say is, get the flat blades, don't get the ones with the little spoons at the end because even though you think, oh, I'll get more product or more material with the spoon, you might, but it's very hard to get the product out.

So, it's better to get the use a a flat blade like this. And it's fine enough that if you, for some reason suspect edemadiosis in an animal, you could tense tense T E N S E, tense the skin and and scrape and get down to the. That first layer of blood, but because most of our ectoparasites in the horse that we're going to scrape for are very superficial.

You don't need to do that. And the nice thing is you cannot cut the horse with this the way you can unfortunately, inadvertently do that with a scalpel blade. So this is the organism, the choreoes as you can see on the top photo they're reproducing and the bottom left, you have the female with the egg and then just the eggs floating free.

This is the mite also on a biopsy. We don't see this very often because hopefully if there are this many mites, we've picked it up by scrape and I had to use a biopsy, but you can see the, the nice picture of the mite and on the half shell. Notice that these mites are quite superficial.

The epidermis on the, on the, all the way on the left is quite a bit below. These guys are in the stratum corneum. Treatment is somewhat controversial because some people feel that It, this is a difficult mite because they can live off the hose for, perhaps a few days and they frequently are having carriers that may not show clinical signs.

So all the incontact horses have to be treated. Here, we have different dosages for avermectins, whether it's ivermectin, ammoxidectin, or doramectin. But also, cleaning the environment, at least, sweeping out the area, washing with, with the high, high concentration of chlorhexidine, and a topical lime sulphur, if that's available in your country, is very helpful, not only because it kills the mites, but it also acts as an antipyretic.

Fipronil or frontline spray, is also effective, has been shown to be effective, but is, rather expensive and as a base has alcohol, so you, you cannot have someone smoking around while you're using it. Probably what's most important to realise is that none of these kill the eggs. So that if you're going to use them, you have to repeat them.

The, the topicals usually on an every other day basis for 6 weeks, the orals, anywhere from every other week to every, every week, in order to clean out the infection, infestation, and the more horses that are involved, the more difficult this is. There's products that we have available in the United States. Now, even with conscientious treatment, as I said before, sometimes they're difficult to eradicate in multiple horse situations.

So ventral midline dermatitis, just to review, diffuse, is, can be caused by culicoides, by black flies, and, and from Oncacirca, the yarid that is now almost an endangered species in many parts of the world because of the use of avermectins which are quite effective against it. And then focal horn flies and chorioptes. Lice.

There are two types of biting lights and one type of sucking louse that affect equids. These are more common in horses that are confined in poor sanitation areas and of course pruritus is the major major clinical sign. This is a, biting louse, we can tell from the, rather round mouth parts.

Whereas this is a sucking louse which has more of a narrow mouth part. This is very typical presentation, the horse reaching around for to, to bite, with its leg up, because of the lice. Of course, there are other reasons for horses to assume this posture, but I've seen it most commonly with lice problems.

And we can see here the, the little knits and a couple of the larger lice. Usually you can see this with a hand lens. You can certainly use that, you can certainly buy a hand lens.

There are a number of them that you can buy for relatively. small amounts of money, but you all probably already have a hand lens. It's just the otoscope in your practise, just take the cone off.

You have a magnifying lens there and you have a light source, it's pretty helpful. Lots of times we can see the lights with just the naked eye. And a donkey here with Going after the werenikiella Equi, and in almost the same posture as the, the horse that we saw and noticed large areas of alopecia both on the trunk, going down the back legs.

More lice, we can see a quite a really wonderful picture of a heavy infestation. The, the, eggs laid on the, and attached to the hairs and the large lice and, and we can see on the bottom, very nice picture of the Of the louse stages and it's incomplete metamorphosis. So lice don't live off the host, and lice also are very species specific.

So we find it by clinical signs, finding the the nits in the lice themselves. Ivermectin will work well for the sucking lice, but the biting lice, is controversial whether it works. So topical permethrin sprays, lime sulphur, and remember to treat all the intact animals.

Chiggers are seen in various parts of the world depending depending upon the part of the world will depend which species you see, . But, these are six-legged larval mites. It's the larvae that prey on the horses, and other species, including people.

Now the adult is a, a vegetation parasite. So the mite attaches to the skin, it takes blood, it falls off after 48 to 72 hours. This occurs in late summer, in the fall and early winter, in fields of natural vegetation where these, mites and the larval form.

Like to hang out. So because they fall off after 48 to 72 hours, you may just have a complaint that the horse is pruritic without actually seeing these mites. They tend to be in places where the horse would come in contact with vegetation, face, neck as it's reaching down to eat, legs, of course, as is walking through sometimes the thorax if it's the, the vegetation is quite high.

Ideally you want to see the bright orange or red larvae, they're quite small, they're in the centre of some lesions, and again, this would be where a hand lens would probably come in handy. This is a horse, obviously, he's got a ragged, it's got a ragged coat from its pruritus. And these are the, we saw lots of mites, we got these just actually with Scotch tape, here they're kind of a darker red brown, and here's one that's obviously orange.

How do we treat these? Pretty much the same way as we would treat sucking lice, ivermectin and or topical permethrin sprays are relatively easy to kill. And then we have oxyurru equi or pinworms, pinworms get blamed for a lot of tail rubbing horses, with the advent of, various anti, anti, .

warming medications such as parental pamoate, ivermectin, oxidectin. These are becoming, less and less common. The females migrate to deposit their ova in the perineal area and this cement that they use is gelatinous material that they use to cement the eggs to the perineal area.

That's what's very, very pruritic. So diagnosis is done by using scotch or clear tape impressions of the perineal region seeing that the ova. Excuse me, this is a a tail rubbing horse due to pinworms, and here are the adult worms themselves.

And this is what the oval looked like. So there are differential diagnoses of tail rubbing and as I said before, pinworms are probably not as common as they used to be as a cause. Ciccoides, as I mentioned before, will go after the top of the, the, the, the tail head.

Atopic dermatitis can do this. Food allergy, of course, which is rare. And then malacisia dermatitis, sometimes we see Excuse me, sometimes we see malocasia.

Which is a yeast, occur either between the mammary glands in females or in what I call the prepetual fossa. That is, if you think of the angle that the prep use makes with the body wall in the male horse. I'm not talking about what's sometimes called the bean inside the prepu.

I'm talking about On the the angle between the prepfuse and the body wall. There's oftentimes in these cases a dark brown greasy, almost graphite looking material that if you smear out on a microscope slide, heat fix and then use a stain. Take a look at it under oil immersion.

Oftentimes we see lots of malaysia or malacesia and bacteria, and these, when this does occur and it can cause a tail rubbing, then the best thing to do is to just wash it out with a 2 or 3% chlorhexidine shampoo. Now, there are things that are in the the pipeline, if you will, of treatingdic horses. There is there have been some studies, experimental work in, especially in Europe, immunisation of horses, who have insect hypersensitivity against their own interleukin 5, and.

This is a cytokine that's important in the in the dealing with eosinophils, and is related to the pruritus that horses experience with insect bite, hypersensitivity and, and some of the initial work is very exciting. I know my understanding was the company was going to go commercial with this, sometime in the next year or two. And then we have Olocitinib Apaquel which is already on the market in many countries for allergic dermatitis in dogs.

There's some anecdotal studies that suggest that 0.25 milligrammes. that, that on a once a day basis, that may be effective, in the horse.

So those are just some future thoughts and I look forward to hearing, stuff from our family researchers on these potentials. Finally, just wanna let you know that the World Congress of veterinary Dermatology, the 9th will be in Sydney, next, next October. Time to start making your plans.

There will be, a full day of equine dermatology. And for those of you who are in mixed practise, there'll be plenty of stuff about dogs, cats, exotic animals, large lecture halls, small workshops, posters, short communications, everything. So this includes my lecture, and I thank you for your attention.