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Parasitic Diseases of Skin

Skin diseases in small animals represent a big percentage of the total daily admisions in veterinary practice . Many skin problems have a difficult diagnosis and treatment , and require referral to a veterinary specialist , in order to shorten the time since the disease is discovered till the diagnosis is reached , treatment is started and a prognosis can be made .

Those diseases affecting skin and adnexa , might be classified by their cause .

Parasitic diseases are relatively frecquent in young animals , in those living in inapropiate environmental situations, when a large humber of animals is held on a same premise , or in the case of nutricional imbalances. 

Fleas still constitute the major cause of many skin problems in cats and dogs , and in their owners . Thoug many modern non toxic flea insecticides , are on the market nowadays , effective control of flea population in open air or extense premises , might be a big problem . In these cases , vet counseling and planning of the control measures , together with a wise choice of products , will be the clue to the erradication of the insects. 

Fleas are vectors of several diseases that might be dangerous both to animals and people . Many animals are allergic to flea bite , showing a severe allergic dermatitis even in the presence of a very small number of fleas .

Ticks constitute another problem , specially during summer , because it is in this season that they reproduce faster . They are blood eating parasites that bite their victims , causing irritation , pruritus , sometimes triggering an allergic episode , or they can inoculate microorganisms that might cause systemic disease of concern in animals and humans . Ticks might be erradicated succesfully using special products with prolonged activity , that lack toxicity .

Handling the infested environment might be difficult and it needs regular spray of insecticides with faster knock down effect , and elimination of wheeds where those insect can find a refuge .

Mange describes a group of highly contagious parasitic diseases of skin ,caused by arthropods named mites , that dig under the skin surface . Mange is common in young animals , in shelter conditions , or in immunedepressed animals . There is one type of mange that might be contagious to humans ( zoonotic ) , but does not constitute a danger to humans because it is easily controlled .

Mange treatment consists in an insecticide dip , or spray , or pour-on formula , together with environmental measures to reduce the continuation of the disease .

Demodectic mange or demodicosis in a very special case of parasitosis , mainly because it is non contagious and is related to immune imbalances . Demodicosis is not a zoonotic disease , and it has several clinical features , like the juvenile form , the localized form and the senile or adult-onset form . The localized form might be mistaken for ringworm .

The generalized form is severe enough to be of reserved prognosis , might be chronic , and needs liftime treatment and parasite count and watch .

There is another form called pododemodicosis , which affects the feet , causing nodules , fistulous tracts and abscesses , with a guarded prognosis .

Treatment is possible , reaching high percentages of healing , with a less dramatic prognosis . Adults that suffered from juvenile form of the disease , or those that had or are having a severe form of demodicosis , should never be bred , because the tendency to suffer the disease is inherited .

There are some other parasitic skin disease , like nodules caused by microfilaria or filaria , or other nematodes.

Allergic reactions to insect bite or hymenoptera stings can also be mentioned here . They can produce acute symptoms like facial edema , urticarial rash , pruritus , etc . , though dramatic , hardly represent a real danger to animals . These hypersensitivities can be diagnosed via skin test , like almost all allergies (not food allergy) , and a specific antivenom treatment might be instituted .

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Bacterial Infections of the Skin

Skin bacterial infections are rarely produced by contact or direct action of a microorganism . Most of the pyodermias ( pyo = pus , dermis = skin ) are a consecquence of of a contaminated skin suffering from an inflammatory process . Those microorganisms are normal inhabitants of the skin and lack pathogenicity , but under certain conditions , they can overgrow and cause symptoms , specially when the barrier function of the skin is interrupted and immune status of the animal is altered .

Citology of direct smears is the most cost-effective tool available , simple and fast , together with culture .

Bacteria most frecquently involved in skin infections in dogs and cats are Staphylococcus , but sometimes Escherichia coli or Pseudomonas can be isolated from lesions . Whenever a skin infection becomes chronic or relapses , it is important to rule out other underlying diseases , using aditional lab work to determine what is perpetuating the infection , and if the bacteria involved has become resistant to the drugs on use . This is done by culture , some times using biopsy samples .

Some skin infections might look worse than they really are . That is the case of hot spots , superficial infections or superficial folliculitis . These cases might be caused by an underlying allergy or hypothyroidism .

Acne is a deep form of pyodermia , that affects the hair shaft , with severe inflammation . Hair is kept on a microabscess and does not come out of the pore , acting as a foreign body . Owners should clean and treat the affected area once daily .

Deep pyodermia or furunculosis is commonly observed in german shepherd dogs and shepherd crosses . This disease is severe and related to an immunological deffect and other yet unknown causes . It needs an aggressive and long term planned therapy , where corticosteroids have no place . It is really helpful to entirely clip the dog´s coat , in order to bathe frecquently and obtain the most antiinflammatory and healing effect of topical therapy .

Bacterial folicullitis is very commun , specially in short coated dog breeds . Its clinical feature might be mistaken for ringworm or dermatophyte infection . It is strongly recommended that those dogs have a thorough allergy and thyroid screening .

Cats suffer from abscesses caused by bite wounds . Those wounds should be treated agressively with antibiotics and surgical access. Affected cats should be screened for feline leukemia virus and feline immunodefficiency virus.

Treatment of skin infections should be planned in advance , chosing the right antibiotic , which dosage and schedule should correspond to the diagnossis already made . Topical therapy sometimes results in less combination of oral or systemic drugs , because it reduces inflammation , pruritus , pain , irritation , and it helps healing and soothing the affected skin .

When the owner suspends treatment by his/her own , or when they modify the dosage already given by the specialist , this can result in bacterial resistance ( misuse of antibiotics ) .

Our advice is that , whenever your pet suffers from a skin infection that becomes chronic , difficult to be treated, or relapses despite treatment , you should contact a dermatologist . It saves you money , and saves suffering to your pet .

dermlink buenos aires ©Copyright2001 / 2005

Fungal diseases of skin
Dermatophyte or Fungal Infections of the Skin ( Ringworm )

From over 200.000 species of fungi on our planet , only less than 200 are able to produce infections or contaminations in humans and animals . Some fungi colonize skin and adnexa ( hair , nails ) producing ringworm or dermatomycoses . Others are inoculated via trauma or puncture wounds , causing deep mycoses . Some others are inhaled and can produce severe systemic illness . Some fungi can cause hypersensitivity .

Dermatophytosis or ringworm affects only skin surface , colonizing hair and nails . Some of these microorganisms are called yeast ( Candida , Malassezia ) , and are perpetuated under altered environmental conditions over the skin surface .

An animal or a person can get ringworm by spores on earth or premises ( furniture , fabrics , kennels ) , by direct contact with a carrier ( sound animal ) or an ill animal .

Diagnosis is relatively simple by culturing hair samples obtained by combing the entire coat with a dental brush, hair samples and nail pieces . Those samples should be submitted to a bacteriology-micology laboratory , speciallized in veterinary microbiology . The results are read after 3 to 4 weeks . Meanwhile , some quick tests like direct observation under microscope or DTM culture , that identify only spores , not species implicated .

Treatment consists in antimycotic drugs , given orally formover 3-4 weeks , plus shampoo therapy ( and rinses) . A special consideration : environment should be treated agressively with bleach on floors and walls , and special products on fabrics , vacuum bags , etc .

Yeast infections – overgrowth incidence has increased over the past years . Malassezia , Candida are contaminants that take advantage of altered environmental conditions on the skin surface . They produce an irritative dermatitis , often allergy-like . Previous treatments with antibiotics or corticosteroids for skin problems can favor yeast overgrowth .

The typical animal suffering from yeast overgrowth presents an allergic or seborrheic dermatitis , bad odor and itchiness . The major complaint is one of an animal that was responding to treatment but not any longer , and that bad odor returne quickly after bathing , together with redness and pruritus ( as soon as a couple of hours after bathing ) . This problem requires identification ( easily done by citology ) , and treatment with antimycotic and shampo .

Subcutaneous or deep mycosis constitue a risk for public health and should be address correctly by speciallized professionals . Treatment is often discouraging . Most of these severe infections are found on immune-impaired animals .

Mold hipersentivity is diagnosed by allergy testing ( mostly intradermal testing ) . Species most frecquently involved are : Aspergillus, Alternaria , Mucor , Cladosporium , Helminthosporium . Once identified , treatment is started with vaccines . It is important to keep in mind that mold spores are found on moisture ( walls , rooms , damp , garden debris kept moist , etc . ) .

Catteries are a special chapter . They need a special plan in order to obtain populations of kitties completely ringworm-free , to be given or sold . This special programmes should be instituted by a specialist .

dermlink buenos aires ©Copyright2001 / 2005

dermlink buenos aires ©Copyright 2005
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