Use of a Local Anaesthetic/Antiseptic Formulation for the Treatment of Lambs Experimentally Infected with Orf Virus

SIMPLE SUMMARY: Contagious ecthyma (orf) is a highly contagious eruptive skin infection of sheep and goats caused by the orf virus of the genus Parapoxvirus. Orf mainly affects young animals in their first year of life, although infection has occurred in other animals and in humans, so it is considered a zoonosis. The disease has high economic repercussions on sheep and goat farms worldwide and can compromise small ruminant value chains, so effective control and therapy are required. As treatment of orf lesions with topical antibiotics is a common practice, non-antimicrobial alternatives are indicated to promote antimicrobial stewardship and avoid increased antimicrobial resistance. A study with the wound formulation Tri-Solfen(®), a topically applied product containing two local anaesthetics (lignocaine and bupivacaine), adrenaline and an antiseptic (cetrimide) in a gel matrix, was conducted. This product was developed for surgical husbandry procedures in Australian livestock and more recently shown to be efficacious for the treatment of foot-and-mouth disease (FMD) in large ruminants, providing almost instant pain relief and faster healing of wounds with a likely viricidal impact. Results of therapy in lambs experimentally infected with orf appeared less encouraging, likely reflecting the relatively milder clinical signs than bovine FMD and deep basal epithelial location of orf lesions. ABSTRACT: Contagious ecthyma is a highly transmissible eruptive viral disease of the skin and mucosa of sheep and goats distributed worldwide. The treatment of orf lesions is usually based on the use of antiseptics and antibiotics for the management of presumptive secondary infections, increasing risks of antimicrobial resistance. The wound dressing formulation Tri-Solfen(®) (TS) containing two local anaesthetics (lignocaine and bupivacaine), adrenaline and an antiseptic (cetrimide) in a gel formulation has been demonstrated to reduce suffering and enhance recovery in cattle and buffalo with oral and skin lesions due to foot-and-mouth disease virus infection and reduced the orf viral load in lambs. In the present study, experimental infection with the orf virus was conducted in 50 newborn lambs and 25 animals were treated after the presence of the first lesions with TS and repeated three days later. Daily clinical examination, haematological, serological, biomolecular and post-mortem analyses were conducted during 34 days after treatment. Results indicated that treatment had no effect on weight gain and clinical progression of the lesions. It was determined that seroconversion after experimental infection occurs 34 days after infection and suggested that the deep basal epithelial location of the orf lesions may have prevented the therapy from having altered the clinical course.