Vet360 Vol 3 Issue 04 August 2016 | Page 34

DERMATOLOGY
HOOKWORM DERMATITIS : Hookworm dermatitis is caused by Ancylostoma caninum where infected larvae , present in soil or mud , in poorly kept kennels or highly contaminated environments , penetrate the skin and burrow into the hair follicles of thin skinned areas ( axillae / inguinal regions / ventral abdomen ), the foot pads and interdigital areas where they continue their life cycle . Young animals living in groups in unhygienic conditions and hunting dogs are highly predisposed .
The thin skinned areas commonly have papules , crusts and excoriations and the foot pads are usually oedematous , thickened and ulcerated . Paronychia and deformed nails may be present in chronic cases . Systemic signs such as diarrhoea , anaemia and weight loss are often present . Diagnosis is made with faecal flotation . Histopathology usually reveals eosinophilic perivascular dermatitis and sometimes larvae can be found . Prognosis is good if the affected dog is dewormed and removed from the contaminated environment .
DEMODICOSIS : Demodicosis is a differential diagnosis for every case of pododermatitis . Usually this is a generalised skin disease that can involve the paws but rarely if may affect the paws only and in very rare cases the foot pads as well . The feet become inflamed and may show hair loss , redness , swelling , crusting and scaling . The foot pads become crusty and thickened .
The diagnosis can be made by microscopic examination of hair plucks or skin scrapings from the paws , but biopsy and histopathology are required in most cases . Treatment with systemic and topical parasiticides for many weeks to months is usually required for successful management . Secondary bacterial infections are common and should be treated .
HARD PAD DISEASE : There are 2 different types of hard pad disease : The first type is a crusting , thickened foot pad and is seen with e . g . pemphigus foliaceous , zinc responsive dermatosis , distemper infections and necrolytic migratory erythema . These foot pads may be painful and cause lameness .
Most commonly these cases will have other accompanying skin lesions and systemic signs , although rare cases of pemphigus foliaceus may present with foot pad lesions only . Biopsies are the most helpful diagnostic procedure . Treatment will depend on the underlying cause .
The second type is a foot pad with excessive fronds of normal appearing keratin . This is most obvious at the margins of the pads and represents overgrowth of the normal keratin mounds of the pads . Inflammation and exudate are not present . Lameness and pain are usually not detected . This condition appears more as if the pads grow abnormally fast and do not desquamate .
PEMPHIGUS FOLIACEUS : Pemphigus foliaceus is the most common of the pemphigus complex . It is characterized by a scaling , crusting and pustular dermatitis that usually affects the face , ear pinnae and foot pads . Some cases may become generalized . The foot pads are usually swollen and hyperkeratotic with scaling , crusting , hardening and fissuring . In severe cases there may be pustule formation , greenish / yellowish discoloration and significant epithelial loss of the foot pads . Cytological examination of the purulent material will reveal large numbers of neutrophils and / or eosinophils and acantholytic keratinocytes which are highly suggestive of pemphigus foliaceus . Bacteria are usually not present on cytology of intact pustules , but may contaminate ruptured lesions . There are usually not systemic signs , but lesions may be painful . The diagnosis is supported by cytology and should in all cases be confirmed by histopathology . This condition is treated with immunosuppressive dosages of prednisolone with or without azathioprine . Topical corticosteroid therapy may be useful for stubborn localised lesions . Pemphigus foliaceus affecting the footpad ( Photo : Dr Heidi Schroeder )
CUTANEOUS DRUG REACTIONS : Cutaneous drug reactions are adverse reactions following systemic and topical drug administration . The pathogenesis is complicated involving both immunological and nonimmunological reactions . All types of hypersensitivity reactions have been reported . Clinical signs are highly variable . In most cases the clinical signs are mild ( urticaria , erythroderma ), but can also be very serious and sometimes fatal ( erythema multiforme , toxic epidermal necrolysis and drug-induced pemphigus foliaceus ).
Cases present with various lesions which may include papules , plaques , erosions and ulcers on various parts of the body , including the foot pads and pad margin . Drugs that have been reported to cause such reactions include antibacterial ( sulphonamides , cephalosporins ), antifungal ( itraconazole , griseofulvin ) and antiparasitic drugs ( ivermectin , moxidectin ), vaccines , topical drugs , hormones and tranquilisers .
There is often a lag period of 5 to 21 days before clinical signs manifest . In most cases discontinuation of the medication and treatment of secondary infections , if present , results in resolution of the skin lesions . Some cases require more aggressive treatment e . g . glucocorticoids and other immunosuppressive drugs . Adverse effects can persist for 1 to 3 weeks after discontinuation of the offending medication . vet360
Issue 04 | AUGUST 2016 | 34