STAPHYLOCOCCOSIS (EXUDATIVE DERMATITIS)

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Causative Agent(s)

Staphylococcus hyicus

It is a gram-positive cocci. It is a normal bacterial flora on the skin of adult swine. It is often found from the environment around piggeries. Virulent and avirulent strains of S. hyicus can be found on the skin of sick and healthy pigs. Virulence is closely associated with the production of exfoliative toxins.

At least six exfoliative toxins, ExhA, ExhB, ExhC, ExhD, ShetA, and ShetB are from strains of S. hyicus that have infected pigs. These toxins are similar to the toxins produced by strains of S. aureus that are isolated from staphylococcal scalded skin syndrome in humans. These toxins target the cells of the stratum granulosum in the epidermis.

Staphylococcus hyicus is the most common cause of disease in pigs. It causes exudative epidermidis. Staphylococcus aureus causes abscesses and other conditions. Other staphylococcal species such as S. chromogenes, S. epidermidis, S. sciuri, S. warneri, and S. xylosus are sometimes isolated from lesions as secondary pathogens.

Clinical Presentation and Epidemiology

Exudative epidermitis (EE) is the most common staphylococcal skin disease in pigs occurring worldwide. It is also known as Greasy pig disease and Marmite Disease. It is seen most frequently in new-born piglets up to about 8 weeks of age.

This disease has high morbidity and mortality in younger pigs. The clinical signs usually observed are anorexia, listlessness, depression, reddened skin, without pruritis, polyarthritis abortion and infertility. Later the lesions appear as brown-black crusts. Ulcers may develop in the mouth and on the tongue. Young pigs die within 24 hours, those that survive after 24 hours would usually die 3–10 days later. Pigs that have been weaned develop lesions on the feet, legs and the rest of the body. Pigs older than six weeks develop a few localized lesions mostly confined to the head.

Adult pigs sometimes have a few brown exudative lesions on the back and flanks and are often not connected to existing outbreaks in younger pigs.

Diagnostic Considerations

Diagnosis of the disease is based on determination of clinical signs and lesions for EE in young piglets.

The disease is confirmed by isolation of the bacteria from enlarged superficial lymph nodes or by histopathology.

Culture and sensitivity test of the organism is advised during outbreak.

The bacteria is cultured on blood agar however selective media containing potassium thiocyanate or less than 10% NaCl can be used.

Biochemical tests are also available for diagnosis.

The serological test used for the diagnosis for this disease is an indirect enzyme-linked immunosorbent assay (ELISA) test to detect the following toxins ExhA, ExhB and ExhC. Polymerase chain reaction can be used to identify toxins, but it is expensive.

Management and Treatment

This consists of fluid replacement, topical disinfectants, and antimicrobial therapy. Drug resistance is very common.

Early treatment is recommended to increase chances of success. Severely affected animals may not respond to treatment.

Antimicrobial drugs commonly used are:

Penicillin, 20,000 IU/kg b.w., q24h 5 days I.M. Streptomycin, 5-10mg/kg b.w., q24h 3-5 days I.M. Oxytetracycline L.A. 20mg/kg b.w., single dose. Erythromycin, 5-20 mg/kg b.w., q24h 3-5days I.M.

Antimicrobial culture and sensitivity tests of isolates is recommended before commencement of treatment.

In the absence of drug susceptibility results these antimicrobials can be used Enrofloxacin, 5mg/kg b.w., q24h 5 days I.M.

Lincomycin, 5-10mg/kg b.w., q24h 3-5 days I.M.

 

Other approaches to management include:

Use of autogenous vaccines containing strains isolated from the affected herd. Newly acquired sows or gilts should be vaccinated before they farrow.

Neonates should be made to take adequate colostrum.

Minimizing skin breaks by clipping needle teeth, removing rough and sharp surfaces. Pigs should be treated for mange if present.

Cleaning and disinfection of pens. Provision of dry well-ventilated pens. Avoiding high stocking densities.