Gangrenous Dermatitis

   
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 4-16 wk 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 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 12-72 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 10-60%. Affected chickens are extremely depressed, lethargic, and prostrate, and die within 8-24 hr. 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.
 
Gangrenous dermatitis, necrotic skin   Gangrenous dermatitis, serous exudate, chicken
     
 
     

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 0.02% rapidly reduces mortality in field outbreaks of clostridial infections. Chlortetracycline, oxytetracycline, erythromycin, levofloxacin with colistin or penicillin in the water have proved beneficial for staphylococcal infections, depending on the results
Reference :- Merck Veterinary Manual
 
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