Parasitic Skin DiseasesPart 1

Cheng-Hung Lai, DVM, PhD.Cheng-Hung Lai, DVM, PhD.Assistant ProfessorAssistant Professor

Department of Veterinary MedicineDepartment of Veterinary MedicineNational Chung Hsing UniversityNational Chung Hsing University

Small Animal Dermatology 2007/03/23

Animal skin is exposed to attack by many kindAnimal skin is exposed to attack by many kinds of animal parasites.s of animal parasites.

Each species has a particular effect on the skin;Each species has a particular effect on the skin; the effect can be mild, as in the case of an isol the effect can be mild, as in the case of an isolated fly or mosquito bite, or severe, as in the cated fly or mosquito bite, or severe, as in the case of generalized demodicosis or canine scabase of generalized demodicosis or canine scabies.ies.

When ectoparasites are vectors or intermediatWhen ectoparasites are vectors or intermediate hosts of bacterial, rickettsia, or parasitic disee hosts of bacterial, rickettsia, or parasitic diseases, they become more important than when ases, they become more important than when they produce only their own effect. they produce only their own effect.

The most serious dermatological concern occThe most serious dermatological concern occurs when the dermatosis produced by parasiteurs when the dermatosis produced by parasites living in or on the skin produces s living in or on the skin produces irritation irritation anandd sensitization sensitization..

The reaction of the skin to these insults varies The reaction of the skin to these insults varies from trivial to lethal but usually includes inflafrom trivial to lethal but usually includes inflammation, edema, and an attempt to localize tmmation, edema, and an attempt to localize the foreign body, toxin, or excretory products ohe foreign body, toxin, or excretory products of the parasite.f the parasite.

These secretions are often allergenic and causThese secretions are often allergenic and cause itching and burning sensations.e itching and burning sensations.

Helminth parasitesHelminth parasites Arthropod parasitesArthropod parasites Arachnids------parasitic ticksArachnids------parasitic ticks parasitic mitesparasitic mites Insects---- ----liceInsects---- ----lice fleaflea

Hookworm dermatitis is a skin reaction at siteHookworm dermatitis is a skin reaction at sites of percutaneous larval penetration in dogs prs of percutaneous larval penetration in dogs previously sensitized to hookworm.eviously sensitized to hookworm.

The disease is caused by The disease is caused by AncylostomaAncylostoma in the tr in the tropics and in worm temperate areas, and by opics and in worm temperate areas, and by UnUncinariacinaria in temperate and subarctic areas. in temperate and subarctic areas.

The highest incidence reported in dogs houseThe highest incidence reported in dogs housed or exercised in contaminated environments.d or exercised in contaminated environments.

Helminth

Hookworm Dermatitis

Helminth

Lesions are characterized by mildly to intensely pruritic, papular eruptions that appear interdigitally and on other skin areas that frequently contact the ground.

Affected skin becomes uniformly erythematous, alopecic, and thickened.

The feet often become swollen, hot, and painful.

Helminth

DiagnosisDiagnosis 1. Fecal flotation1. Fecal flotation 2. Dermatohistopathology2. Dermatohistopathology 3. Response to treatment3. Response to treatment

TreatmentTreatment 1. fenbendazole, mebendazole, or pyrantel pamoate 1. fenbendazole, mebendazole, or pyrantel pamoate twice 3-4 weeks aparttwice 3-4 weeks apart 2. environmental sanitation2. environmental sanitation

Helminth

Pelodera Dermatitis

Pelodera (Rhabditis) strongyloidesPelodera (Rhabditis) strongyloides is a small sais a small saprophytic nematode that lives in decaying orgaprophytic nematode that lives in decaying organic matter. nic matter.

On rare occasions, it can invade the mammaliaOn rare occasions, it can invade the mammalian skin, causing a pruritic, erythematous, alopecn skin, causing a pruritic, erythematous, alopecic and crusting dermatitis on skin sites that coic and crusting dermatitis on skin sites that come into contact with the ground.me into contact with the ground.

Helminth

Clinical featuresClinical features A pruritic, alopecic, erythematous and crusting A pruritic, alopecic, erythematous and crusting

dermatitis affecting body sites in contact with dermatitis affecting body sites in contact with the ground was a typical clinical feature the ground was a typical clinical feature

Secondary pyoderma may be presentSecondary pyoderma may be present

Helminth

Diagnosis of the disease is based on case histoDiagnosis of the disease is based on case history (a dog living outdoors on damp straw beddiry (a dog living outdoors on damp straw bedding) with characteristic skin lesions and on the ng) with characteristic skin lesions and on the demonstration of typical larvae in skin scrapindemonstration of typical larvae in skin scrapings or biopsy.gs or biopsy.

Pelodera Pelodera (rhabditic) dermatitis cases have bee(rhabditic) dermatitis cases have been reported mainly from Central European coun reported mainly from Central European countries and the United States. ntries and the United States.

Helminth

(Saari and Nikander, 2006)

Helminth

Skin scrapings and histopathology as diagnostic tools

Skin scraping is an easy, fast, inexpensive and reliable method for the diagnosis of Pelodera dermatitis. The length of larvae in skin scrapings varied from 600 to 750 μm, and the width from 30 to 40 μm

Helminth

(Saari and Nikander, 2006)

Helminth

Hyperkeratosis

paired lateral alae (a)

The oesophagus of the larvae was of the rhabdThe oesophagus of the larvae was of the rhabditiform type, consisting of an elongated corpus,itiform type, consisting of an elongated corpus, followed by a distinct swelling midway down t followed by a distinct swelling midway down the oesophagus and narrow isthmus, ending ahe oesophagus and narrow isthmus, ending aborally with a clearly defined valvulated bulb. borally with a clearly defined valvulated bulb. The cuticle was distinctly transversally striateThe cuticle was distinctly transversally striated. The oral opening was surrounded by lips, bud. The oral opening was surrounded by lips, but their number and arrangement could not be t their number and arrangement could not be determined with LM. determined with LM.

Helminth

(Saari and Nikander, 2006)

Helminth

buccal capsule

narrow isthmus

(Saari and Nikander, 2006)

Helminth

DracunculiasisDracunculiasis

Dracunculiasis is a skin disease that is caused Dracunculiasis is a skin disease that is caused by by DracunculusDracunculus, a nematode that parasitizes s, a nematode that parasitizes subcutaneous tissues. Infection occurs when thubcutaneous tissues. Infection occurs when the mammalian host ingests an infected microsce mammalian host ingests an infected microscopic crustacean (intermediate host) while drinopic crustacean (intermediate host) while drinking contaminated water. Over the next 8 to 1king contaminated water. Over the next 8 to 12 months, the larvae develop into adults withi2 months, the larvae develop into adults within the mammalian host's subcutaneous tissue.n the mammalian host's subcutaneous tissue.

Helminth

In North America, In North America, Dracunculus insignisDracunculus insignis primari primarily parasitizes raccoons, mink, and other wild ly parasitizes raccoons, mink, and other wild mammals, with infection in dogs and cats occmammals, with infection in dogs and cats occurring uncommonly.urring uncommonly.

In Africa and Asia, In Africa and Asia, D. medinensisD. medinensis (the guinea w (the guinea worm) infects many mammals, including dogs, orm) infects many mammals, including dogs, horses, cattle, and humans.horses, cattle, and humans.

Lesions are often painful or pruritic, chronic, siLesions are often painful or pruritic, chronic, single or multiple subcutaneous nodules on the ngle or multiple subcutaneous nodules on the legs, head, or abdomen that eventually fistulatlegs, head, or abdomen that eventually fistulate (and through which female worms are stimule (and through which female worms are stimulated to discharge their larvae when the skin coated to discharge their larvae when the skin contacts water).ntacts water).

Helminth

Helminth

DiagnosisDiagnosis 1. Cytology (fistulous exudate): eosinophils, 1. Cytology (fistulous exudate): eosinophils, neutrophils, macrophages, and 500neutrophils, macrophages, and 500μμm-long m-long nematode larvae that have tapered tailsnematode larvae that have tapered tails 2. Dermatohistopathology: subcutaneous 2. Dermatohistopathology: subcutaneous pseudocyst that contains adult and larval pseudocyst that contains adult and larval nematodes surrounded by eosinophilic nematodes surrounded by eosinophilic pyogranulomatous inflammationpyogranulomatous inflammation

Persian physicians removing Guinea worm from legs of patients (by Velschius, 1624-1677)

A plate by Fedchenko showing the Guinea worm rolled up on a stick, larvae in the body cavity of cyclops

Helminth

Helminth

Helminth

Pyogranulomatous inflammation surrounding an adult Dracunculus insignis with larvae

Treatment and PrognosisTreatment and Prognosis 1. Nodules should be surgically excised.1. Nodules should be surgically excised. 2. Water supplies should be decontaminated.2. Water supplies should be decontaminated. 3. The prognosis is good. However, 3. The prognosis is good. However, dracunuliasis is contagious to other animals dracunuliasis is contagious to other animals and humans via animal-crustacean-animal and humans via animal-crustacean-animal transmission.transmission.

Canine scabies

Highly contagious parasitic dermatosis caused Highly contagious parasitic dermatosis caused by the multiplication in the epidermis of an acby the multiplication in the epidermis of an acarine mite of the speciesarine mite of the species Sarcoptes scabiei var canis (200 to 400 μm). (200 to 400 μm).

Intensely pruriticIntensely pruritic.. Quite common.Quite common.

ArachnidsArachnids

ArachnidsArachnids

• Parasitic life cycle (egg-larva-nymph-adult) short, 2 to 3 weeks.

• The fertilised females on the skin surface move rapidly towards the warmer areas of the skin and burrow into the epidermis to lay eggs.

• Life expectancy of adult mites: 4 to 5 weeks.

• In the environment (off the host), the different parasitic stages survive for only short periods (2 to 6 days at 25°C). Nevertheless, at lower temperatures and high humidity, nymphs and females can survive for up to 3 weeks and may lead to reinfection.

■ Clinical signs ◙ There is severe and constant pruritus often l

eading to a rapid appearance of extensive excoriations.

◙ Primary lesions: erythematous papules, crusted papules. Typical primary lesions (to be scraped!) are crusted papules which represent the exact points where the fertilised females entered the epidermis. They appear either just prior to, or simultaneously with the development of increasing pruritus.

◙ Secondary lesions: crusts, excoriations, hyperpigmentation, lichenification.

ArachnidsArachnids

◙ ◙ Associated dermatological findings: scaling aAssociated dermatological findings: scaling and seborrhoeic problems, alopecia, pyotrau- nd seborrhoeic problems, alopecia, pyotrau- matic dermatitis, otitis externa affecting the mmatic dermatitis, otitis externa affecting the margins of the ear flaps.argins of the ear flaps. ◙ Lesion distribution: the favourite habitats of the mites and thus the sites of the lesions are the margins of the ear pinnae and the bony prominences, especially elbows and hocks, and then the ventral portions of the chest and abdomen. When the disease spreads, the entire body may be involved, but the dorsal midline is always spared.

ArachnidsArachnids

■ Diagnosis

ArachnidsArachnids

◙ ◙ Skin biopsiesSkin biopsies

◙ ◙ ScrapingsScrapings

◙ ◙ Pinnal-pedal reflexPinnal-pedal reflex◙ ◙ Clinical elementsClinical elements

◙ ◙ HistoryHistory

◙◙ Response to scabicidal treatment

Pinnal-pedal reflexPinnal-pedal reflex

■ Treatment ◙ Topical treatment • Selamectin (6 mg/kg) and moxidectin (2.5

mg/kg) are effective when applied as spot-on preparations at monthly intervals. Treatment for 2-3 months is advisable.

◙ Systemic treatment • Ivermectin (250 to 400 μg/kg, 2 or 3 times a

t 10 or 15 day intervals) by subcutaneous injection.

• Milbemycin oxime (2 mg/kg, 3 times at 1 week intervals) orally.

◙ ◙ Additional therapy.Additional therapy. • • Keratolytic, antiseborrhoeic, antipruritic and Keratolytic, antiseborrhoeic, antipruritic and

emollient topical shampoos and lotions.emollient topical shampoos and lotions. • • Possible systemic corticosteroid treatment fPossible systemic corticosteroid treatment f

or the first week in cases with very intense pror the first week in cases with very intense pruritus (prednisolone, 0.5 to 1 mg/kg/day oralluritus (prednisolone, 0.5 to 1 mg/kg/day orally, 2 or 3 days): only when a definitive diagnosy, 2 or 3 days): only when a definitive diagnosis has been made by scrapings.is has been made by scrapings.

Feline ScabiesFeline Scabies

Feline scabies is a disease that is caused by Feline scabies is a disease that is caused by NoNotoedres catitoedres cati, a sarcoptic mite that burrows sup, a sarcoptic mite that burrows superficially in the skin. erficially in the skin.

Feline scabies is noted as intensely pruritic, drFeline scabies is noted as intensely pruritic, dry, crusted lesions that usually first appear on ty, crusted lesions that usually first appear on the medial edges of ear pinnae, then spread rahe medial edges of ear pinnae, then spread rapidly over the ears, head, face, and neck. Lesiopidly over the ears, head, face, and neck. Lesions may subsequently spread to the feet and pens may subsequently spread to the feet and perineum. rineum.

Infested skin becomes thickened, lichenified, Infested skin becomes thickened, lichenified, alopecic, crusted, or excoriated. alopecic, crusted, or excoriated.

DiagnosisDiagnosis 1. Microscopy (superficial skin scrapings): 1. Microscopy (superficial skin scrapings): detection of notoedric mites, nymphs, larvae, detection of notoedric mites, nymphs, larvae, or ovaor ova 2. Dermatohistopathology: superficial 2. Dermatohistopathology: superficial perivascular or interstitial dermatitis with perivascular or interstitial dermatitis with varying numbers of eosinophils and varying numbers of eosinophils and pronounced focal parakeratosis.pronounced focal parakeratosis.

TreatmentTreatment 1. Traditional therapy is to bathe the animal with a 1. Traditional therapy is to bathe the animal with a mild antiseborrheic shampoo to loosen crusts, mild antiseborrheic shampoo to loosen crusts, followed by a total body application of 2 to 3 lime followed by a total body application of 2 to 3 lime sulfur solution every 7 days sulfur solution every 7 days 2. Ivermectin 0.2-0.3 mg/kg PO or SC twice, 2 weeks 2. Ivermectin 0.2-0.3 mg/kg PO or SC twice, 2 weeks apartapart 3. Doramectin 0.2-0.3 mg/kg SC once3. Doramectin 0.2-0.3 mg/kg SC once 4. 0.015% amitraz solution applied to entire body q 7 4. 0.015% amitraz solution applied to entire body q 7 days for 21 daysdays for 21 days

Canine localized demodicosisCanine localized demodicosis

Canine localized demodicosis is associated witCanine localized demodicosis is associated with h overpapulation of the mitesoverpapulation of the mites Demodex canDemodex canisis, which are normal inhabitants of the hair foll, which are normal inhabitants of the hair follicle, and sometimes of the sebaceous glands.icle, and sometimes of the sebaceous glands.

Predisposing factorPredisposing factor endoparasitism, poor nutrition, immuno-surprendoparasitism, poor nutrition, immuno-surpr

essive drug therapy, transient stress (e.g., estressive drug therapy, transient stress (e.g., estrus, pregnancy, surgery, boarding)us, pregnancy, surgery, boarding)

Highest incidence in puppies Highest incidence in puppies 3 to 6 months old3 to 6 months old

Clinical features ◙ Canine localized demodicosis may appear as one to five patchy areas of alopecia with variable erythema, hyperpigmentation, and scaling localized to one region of the body. ◙ Lesions are most common on the face, but they can be anywhere on the body. ◙ Lesions are not usually pruritic unless they are secondarily infected.

DiagnosisDiagnosis ◙ ◙ Deep skin scrapingDeep skin scraping ◙ ◙ DermatohistopathologyDermatohistopathology TreatmentTreatment 1. Any predisposing factors and secondary pyoderma should be identified and treated. 2. Lesions should be treated topically with 2.5% to 3% benzoyl peroxide shampoo, lotion, or cream every 24 hrs. 3. 0.03% to 0.05% amitraz solution applied to lesions every 24 hours is often effective. 4. Topical therapy is continued until follow-up skin scrapings are negative and lesions have resolved.