Contagious pustular dermatitis

Contagious Pustular Dermatitis (CPD), also known as Orf or Sore Mouth, is a viral disease that affects sheep, goats, and occasionally humans. It is caused by the Parapoxvirus, which belongs to the Poxviridae family. This zoonotic infection is characterized by the development of pustular lesions primarily on the lips and muzzle of affected animals. In humans, it typically presents as a single lesion on the hands or fingers, reflecting the point of contact with the infected animal.

Symptoms and Diagnosis

In sheep and goats, CPD initially manifests as redness and swelling on the lips, progressing to the formation of pustules that eventually rupture and scab over. The lesions can cause significant discomfort, leading to reduced feed intake and weight loss. In severe cases, lesions may also appear on the udder or teats, which can lead to secondary bacterial infections and complications with nursing young animals.

In humans, the infection usually results in a single, painful pustular lesion where the virus entered through broken skin. The lesion goes through several stages, starting as a red bump, which then becomes a blister, ulcerates, and finally crusts over. The entire process can take several weeks, and while it is typically self-limiting, it can be highly uncomfortable.

Diagnosis of CPD is primarily based on clinical signs and the history of exposure to affected animals. Laboratory tests, including polymerase chain reaction (PCR) and electron microscopy, can confirm the diagnosis by identifying the virus in samples taken from the lesions.

Transmission

CPD is highly contagious among sheep and goats through direct contact with the lesions or indirectly via contaminated fomites. Humans can contract the disease through direct contact with the infectious lesions of affected animals or contaminated materials. The virus can penetrate the skin through cuts, abrasions, or other breaks in the skin barrier.

Prevention and Control

Preventive measures include isolating affected animals to reduce the spread of the virus and practicing good biosecurity measures, such as disinfecting equipment and facilities. Vaccines are available for use in sheep and goats to prevent CPD, but their use is typically reserved for herds with a history of the disease.

In humans, wearing protective gloves when handling animals known to be or suspected of being infected with CPD can prevent transmission. Prompt washing of any cuts or abrasions that occur while handling animals and applying appropriate disinfectants can also reduce the risk of infection.

Treatment

There is no specific antiviral treatment for CPD. In animals, management focuses on supportive care to ensure affected individuals continue to eat and drink, along with the application of topical antiseptics to prevent secondary bacterial infections. In humans, treatment is primarily supportive, involving the cleaning and dressing of lesions to prevent secondary infections and the use of pain relief medications as needed.