Complicated Orf in Small Ruminants: Secondary Infections and Clinical Management

An animal with orf may initially have a familiar pattern of proliferative and crusting lesions. The clinical concern changes when those lesions become secondarily infected, interfere with feeding, or extend beyond the skin. When does a routine orf case become complicated, and what should the veterinarian watch for? 

Secondary Infection Can Change the Clinical Picture^[1] 

Orf develops after ORFV enters damaged skin and multiplies in epidermal cells. In grazing sheep and goats, abrasions caused by dry, stemmy or prickly feed can provide an entry point around the lips, nostrils and oral tissues. 

The primary viral lesions can subsequently become complicated by bacterial infection. Dermatophilus congolensis may invade orf lesions, making the clinical appearance more difficult to interpret. More extensive complications have been associated with Fusobacterium necrophorum, particularly when buccal mucosal lesions are involved. 

When F. necrophorum is associated with oral lesions, infection may extend through the digestive tract. Granulomatous lesions and hoof shedding have been described with visceral involvement, while vulval ulceration may occur in the generalised form associated with this organism. 

These changes should prompt closer clinical attention rather than being treated as part of an uncomplicated skin lesion. 

Feeding Problems are Clinically Important 

The location of orf lesions can make a relatively local disease clinically significant. Painful lesions around the mouth may restrict nursing and grazing, particularly in lambs and kids. Affected animals can develop anorexia and, in severe cases, starvation^[2]. 

This makes nutritional support and observation of feed intake important components of case management. Sick animals should be separated, nourished, and treated rather than left to compete with unaffected animals. 

The severity of disease should also be judged by what is happening beyond the visible skin lesions. Necrotic foci and ulcers may occasionally develop in the tongue, mouth, throat, rumen, and abomasum. Liver abscesses have also been reported. In severe disease, pneumonia may develop and can contribute to death^[1]. 

Management Should Target the Complication^[1] 

There is no specific antiviral therapeutic regimen for ORFV. Supportive care, including antibiotics, may help prevent or treat secondary bacterial infections. 

During an outbreak, affected animals should be kept apart from the rest of the flock or herd, adequately nourished and treated. Ceftriaxone and tazobactam have been recommended for affected goats. Antimicrobial treatment should, however, be considered in the context of suspected or established bacterial complications rather than assumed to be necessary for every uncomplicated orf case. 

Milk from animals with sores on the teats should not be consumed. Careful handling is also necessary because direct contact with lesions can expose people to infection. 

Recovery Does Not Guarantee Protection^[1] 

Clinical recovery does not necessarily mean that future infection is impossible. Humoral immunity contributes to the response to ORFV, while cell-mediated immunity has an important role in recovery. 

Recurrent infections can occur one to three months later and are generally less severe and heal more rapidly. Previous exposure therefore remains relevant when assessing recurrent lesions, although recurrence should still be assessed on its clinical presentation. 

Protect the Animal—and the Handler^[1] 

Orf is zoonotic, making protective handling particularly important when lesions are extensive or infected. Gloves and facemasks should be used when handling affected animals or administering vaccination. 

Isolation is equally important for controlling transmission. Direct contact between susceptible and infected animals is a primary route of spread, while newly introduced animals should be confined before being incorporated into the herd or flock. 

Clinical Bottom Line 

A complicated orf case is more than a worsening skin lesion. Persistent or extensive lesions, impaired feeding, suspected bacterial invasion, oral or visceral involvement and deterioration in the animal's condition should prompt closer monitoring and supportive management. 

Separating affected animals, maintaining adequate nutrition, addressing secondary bacterial infection when clinically indicated, and protecting handlers can help manage complicated contagious ecthyma while limiting further transmission.

References:

1. Bhagawati N, Shankarishan P, Habibi M. Contagious ecthyma in goat and sheep: a review of current status and future perspectives. https://mbimph.com/index.php/UPJOZ/article/view/4982/6394
2. Chan KW, Lin JW, Lee SH, Liao CJ, Tsai MC, Hsu WL, Wong ML, Shih HC. Identification and phylogenetic analysis of orf virus from goats in Taiwan. Virus genes. 2007 Dec;35(3):705-12. https://www.researchgate.net/profile/Wei-Li-Hsu-3/publication/6156481