Gangrenous Dermatitis
(Necrotic dermatitis,
dermatomyositis)
Gangrenous
cellulitis,
Clostridial
Gangrenous dermatitis is characterized by a sudden onset,
sharp increase in mortality, and gangrenous necrosis of the
skin over the wings, thighs, breast, and head. It occurs
sporadically in chickens 61-4wk old, affects broiler and layer
replacement stocks, and occasionally causes outbreaks in
turkeys .
Etiology, Transmission, and Epidemiology :
Gangrenous skin necrosis may be associated with various
aerobic and anaerobic bacteria; however, Clostridium
septicum
,
Clostridium
perfringens
type
A,
and
Staphylococcus aureus , either singly or in combination are
most often involved. Combined infections are often more
severe. Young chicks immunosuppressed by infectious
bursal disease ( Infectious Bursal Disease: Introduction) or
chick anemia virus are predisposed. The disease may occur
secondary to avian adenovirus or reticuloendothelial virus
infections as well. Skin lesions due to trauma, wet litter,
picking, or treading wounds may provide entry sites for
causative bacteria. The disease has been reproduced by SC
or IM inoculation of S aureus , C septicum , or C perfringens
type A. Inoculated chickens develop gangrenous necrosis of
the skin and underlying musculature and can die within 21-61
hr. Systemic effects arise from invading bacteria and their
elaborated exotoxins .
Clinical Findings and Lesions :
The first sign is usually a sudden dramatic increase in
mortality in the affected flock. Overall mortality is %11-61.
Affected chickens are extremely depressed, lethargic, and
prostrate, and die within 14-8hr. Red to black patches of
moist, gangrenous skin are seen over the breast, abdomen,
wing tips, or thighs. Feather loss or sloughing of the
epidermis is common. When clostridial infection occurs,
palpation of the affected areas often reveals crepitation due to
gas bubbles in the subcutis and musculature. At necropsy,
there is an accumulation of gaseous, serosanguineous fluid
in the subcutis, and the musculature has a pale cooked
appearance. The liver and spleen are enlarged and may
contain infarcts or pale focal areas of necrosis. The kidneys
are usually swollen, and the lungs may be congested and
edematous or necrotic. Atrophy of the bursa of Fabricius may
be found in birds that were exposed to infectious bursal
disease virus in the first few weeks after hatching .
Diagnosis :
Histopathologic demonstration of gangrenous necrosis with
numerous coccoid bacteria or large, gram-positive rods with
or without spores in affected tissues is sufficient to confirm a
clinical diagnosis. Isolation of the etiologic agent ( C septicum
, C perfringens, or S aureus ), together with the history and
clinical findings, differentiate gangrenous dermatitis from
exudative diathesis and other diseases involving the skin .
Treatment and Control :
Maintaining proper litter conditions, minimizing traumatic
injury, and controlling cannibalism can help prevent the
disease. A program to vaccinate breeders against infectious
bursal disease to establish healthy, immunocompetent,
replacement stock has also been useful. Administration of
oxytetracycline in the feed at %1.11rapidly reduces mortality
in field outbreaks of clostridial infections. Chlortetracycline,
oxytetracycline, erythromycin, or penicillin in the water have
proved beneficial for staphylococcal infections, depending on
the results of antibiotic sensitivity testing .