Orf causes lesions on the mouth of sheep. What type of virus is responsible?

Orf is caused by a virus belonging to the Parapoxvirus genus, which is known for its ability to infect sheep and goats, leading to characteristic lesions, particularly on the mouth and lips. This virus is a member of the poxvirus family and is specifically associated with orf, also known as contagious ecthyma. The lesions commonly manifest as scabby or crusty openings, which can be painful and interfere with feeding.

The other viruses listed do not cause the specific lesions associated with orf. Orthopoxviruses, for example, include smallpox and cowpox viruses, which are distinct and do not primarily affect sheep in the way that Orf does. Herpesviruses and adenoviruses have different pathogenic mechanisms and clinical presentations, neither of which encompasses the symptoms caused by parapoxviruses. Thus, identifying parapoxvirus as the causative agent of orf is essential for understanding the disease's etiology and for implementing appropriate management and treatment strategies in affected livestock.