Contagious Pustular Dermatitis

Syn: Contagious ecthyma, scabby mouth, sore mouth, Orf

• It is highly contagious viral disease of goat and sheep characterized by development of pustular and scabby lesion on muzzle and lips.
• Such eruptions like papules or vesicles of pox like lesion can be seen on cornea, nostril and eyes, vulva, udder and teats of sheep;
• Lesions are proliferative and lead to formation of scabs.

Etiology

• Parapox virus of Poxviridae family
• It is distinct from vaccinia virus but has antigenic similarity to goat pox virus but not with sheep pox virus.
• Virus withstand drying and survives at room temperature for at least 15 years.
• Virus particles are 270 x 160 µm in size

Epidemiology

• Disease is found globally in sheep and goat populations.
• Young animals, especially lambs and kids are more susceptible to severe form of disease.
• Outbreaks can occur more frequently during late summer, fall and winter or when animal are housed in feedlots.
• Morbidity of disease is usually high ~ 90% whereas mortality is around 15% but may reach 75%.
• The higher mortality was observed among flocks with mixed infections of orf and Peste des petits (PPR) or Orf and Hemonchosis as compared to other outbreaks.
• The Orf outbreaks were reported across various Indian states, viz., Uttarakhand, Assam, Meghalaya, Haryana, Uttar Pradesh, Rajasthan, Tripura, Kashmir, Tamil Nadu, and Odisha.

Transmission

• Disease may be transmitted through skin abrasion and contact with infected animals or contaminated fomites.
• Scab falling to ground during healing acts as source of infection.
• Direct contact between infected and healthy individual.
• Inhalation of droplets contaminated with viral particles.

Pathogenesis

• Virus gains entry through skin abrasion or direct contact with fomites or animals
• Virus invades epithelial cells of nostrils and commissure of lips and replicates there.
• Replication of virus leads to development of characteristic skin lesion. First papules, then progress to vesicles, pustules.
• Finally, pustules ruptures and form scabs that eventually dries off and fall off.

Clinical Signs

• IP= 2-3 days in sheep and goat
• Dullness, depression, anorexia and rise of temperature varying from 106-108°F.
• Profuse salivation, lacrimation accompanied with mucopurulent discharge
• Congestion of nasal and buccal mucosa with appearance of nodular eruptions on oral commissure, lips, mouth and nostril.
• Lesion develop initially as papules and then rapidly progresses to pustules and scabs.
• Scab forms within 1 week and peel off the skin within 4 weeks.
• more severely affected lambs do not eat normally, and they lose condition.

PM Findings

• Typical ulcerative lesion in nasal cavities and URT
• Erosion on mucosa of esophagus, abomasum and small intestine
• Lymph nodes congested and dark red in color
• Lesion appears on mucocutaneous junction of the lips and around erupting incisor teeth, and it may extend to the mucosa of the buccal cavity.
• Occasionally, lesions are found on the feet and around the coronet, where secondary bacterial infection with Dermatophilus congolensis commonly leads to strawberry footrot.
• Ewes nursing infected lambs may develop lesions on the teats that extend onto the udder skin.

Diagnosis

• On the basis of clinical findings
• On the basis of PM findings
• Serological test: CFT, AGDT, FAT
• Animal inoculation test: Vesicular fluids or suspension of scab materials may be swabbed into scarified skin of known immune and non-immune animals. They may be observed for the appearance of characteristics lesion.

Differential Diagnosis

1. Blue tongue:

• Severe systemic reaction
• Lesion occur on muzzle and coronet

2. Ulcerative dermatosis:

• It causes tissue dermatitis and ulcer
• It affects older animals.

Treatment and Control Measures:

• Application of 5% CuSO₄ after removal of scab (7% iodine or 3% phenol)
• Unattenuated live virus vaccine; age: 4-6 weeks, by scarification at hairless or wool less areas, Booster: 2-3 months later.
• Both parenteral and topical antimicrobials may help combat secondary bacterial infection of the skin lesions of contagious ecthyma.
• In endemic areas, appropriate repellents and larvicides should be applied to the lesions to prevent myiasis.
• Veterinarians and sheep handlers should exercise reasonable protective precautions and wear disposable gloves.
• vaccinated animals should be segregated from unprotected stock until the scabs have fallen off.