Dermatophilosis (Mycotic Dermatitis)

Dermatophilosis (Mycotic Dermatitis) is also known as Cutaneous Streptothricosis, Lumpy wool of sheep and Cutaneous actinomycosis.

Dermatophilosis (Mycotic Dermatitis) is a disease of superficial skin of animals and man, manifested by exudation with matting of hairs, wools and formation of crusts and scab.

Etiology

The Dermatophilosis (Mycotic Dermatitis) disease is caused by Dermatophilus congolensis in cattle and D. dermatomanes and D. pedis in sheep.
It is a Gram positive, non-acid fast, multiphasic life cycle, organism produces motile spores known as zoospore.
The organisms is a facultative anaerobe.

Epidemiology

Prevalence of infection

Disease is prevalent through out tropical and temperate region of the world.

Economic Impact

Causes a major economic losses in Africa, Australia, New Zealand, Europe, Middle east N, C, South America, India and Bangladesh.

Predisposing factors

Moist and cold weather conducive for spread of the diseases and most of the outbreaks occur during rainfall.
Concurrent infection like contagious ecthyma in sheep.
Humidity and warm temperature. Abundance of biting arthropods (Amblyomma variegatum, Boophilus microplus, Hyalomma), Sarcoptes, Demodex, mosquitoes, stinging and bloodsucking flies.

Source of infection

Exposure of surface of the body to water retention area.

Transmission

Direct contact with infected materials and infected animals.
Mechanical transmission through instruments, brushes, harnesses, bedding materials are possible.
Transmission occurs through anthropod vectors like flies, Musca domestica, Lucilia cuprina, Stomoxys calcitrans and Calliphora spp.
Ticks and sheep acts as a mechanical vector.
The disease also spread from one animal to other while dipping.
Infection spread through abrasion.

Host affected

Most commonly seen in cattle, sheep and horse.
Reported also in goats, donkeys, dogs, fox, cat, deer, antelope, zebra, pig, monkey, racoons and wide variety of wild animals.
Experimentally transmitted in camel and rabbit.
Man is readily infected with dermatophilosis therefore, may be considered as zoonotic disease.

Pathogenesis

The organism invades hair follicles, sweat glands and other epidermal layer.
The organism is highly proteolytic and liberates urease, increased hydrolysing casein, liquifies gelatin and coagulates serum.
Three stages of development has been observed.
Hairs of the infected animals mats with exudates and form crust.
The hairs adhere strictly and difficulty to remove.
The greasy scabs removed and there is a formation of dry scabs.
Scars turn hard and confluent which make alopecia.
Mild cases disappear spontaneously.
Histological studies show filaments and mature multiple organisms in the cornified epithelial cells, leucocytes and dermis of animal.
Pathogenic changes are localised to epidermis and to some extent in the underlying dermal surface.

Clinical Signs

In Cattle

Purulent exudates below the crust and removal of crust will reveal moist and inflamed areas of granulation tissues.
Systematic signs are not apparent except the febrile reaction.
Milk yield reduced.
Acute cases with extensive lesions complicated by secondary bacterial infection may lead to death due to endotoxemia.
A chronic form of disease with deep encrustation is common.
Dermatophilosis – Bovine – rain scald or raised crusts

In Horses

Itching is absent, skin is thickened and dried up exudates mat together form scab and plague.
Removal of scab will exhibit a bleeding surface.

In Sheeps

Disease may appear in mild form, which may so unnoticed except loss of wool.
In sheep it is ascribed as mycotic dermatitis.
Exudates mat the fibres together at the base and form crust.
Crust spread in a pyramidal fashion, affect flank, rump occasionally sides and outer sides of legs.
Heavy mortality in young lambs. Dermatophilosis – Sheep Sore mouth are in sheep and goats.
Lesions prominently present on scrotum, coronet, mouth and nose.

In Dog and Cats

Exhibits the feature of exudative dermatitis manifested as discrete, multiple focal raised lesions.
The incidence is extremely rare in cat.

Necropsy Findings

Lesions on neck, body of the udder and extend down to the legs and assume a mosaic pattern with diameter 2.5 cm.
It is common in back, sides and on rump.
Lesion in muzzle, face, eyes, produces lacrimation and nasal discharge.
Lesion also observed in all parts of body, abdomen and thorax.
Proliferative dermatitis, known as strawberry foot rot is noted where scabs on removal would exhibit bleeding points.
On fleshy mass resembling fresh strawberry and this condition is ulcerative dermatitis which affect the skin of legs from the coronet to above the knee or hock.
Individual lesions coalesce, enlarge produce wart like masses and cover the entire legs.
The lesions may appear tumor like in mouth are known as oral dermatophilosis. It is characterized by granuloma affecting tongue and crypts of tonsil.

Diagnosis

Based on clinical signs and necropsy findings.
Identification and isolation of organism.
Specific fluorescent antibody test for detection of antigen.

Differential Diagnosis

FMD
Scabby mouth
Photosensitization

Prevention

Quarantine of affected animals.
Administration of bacterin or vaccine is effective.

Control

Contact with infected animals and materials should be avoided.
Control of tick and fly by spraying insecticide/acaricides.
Special care during rainy season.
After shearing or clipping dipping in 0.5% Zn So4 solution.
Alum should be applied after shearing.
To reduce the prevalence of infection whole flock should be dipped after shearing with cetrimide-zinc sulphate cream.
Control can be done either alone or in combination with organophosphate or synthetic pyrethroid chemicals.
Use of magnesium fluorosilicate, sulphur-rotenone dip.