A Veterinarian's Perspective: 
Soremouth Facts
Heather J. Ludlam, DVM
Reprinted from the NASSA News

            As a small ruminant practitioner, I find myself constantly answering questions about infectious/contagious diseases of sheep and goats.  One of the most asked and talked about of these diseases is Soremouth. 

            The technical veterinary name for Soremouth is Contagious Ecthyma.  It is also known as Orf.  Soremouth is caused by a virus- specifically a Parapox virus.  Soremouth is a zoonotic disease- meaning that it can be spread from animals to humans. 

            The clinical signs of Soremouth are proliferative, crusting lesions which usually occur on the mouth and nose.  The lesions can start as pustules or vesicles that resemble pimples, but quickly progress to crusty scabs.  These lesions can also occur on other parts of the body- the legs, genitals and especially the udders of dams nursing their affected young.  The lesions typically begin to occur 4 to 14 days following exposure to the virus and regress spontaneously within 2 to 3 weeks time.  Depending on the size of the flock, it can take 4 to 8 weeks, or even longer, for the Soremouth virus to run through the entire flock.

            Soremouth most commonly occurs in young sheep and in adult sheep that have not been exposed to the virus.  Once exposed, immunity lasts for years.  Soremouth is most commonly spread from sheep to sheep by close association, but it can also be spread through contact with infected hands or equipment, or exposure to the infective scabs or virus in the environment.  The virus is contained in the scabs, which drop off of the infected sheep into the environment- the virus can survive in the environment for months.

            Humans contract Soremouth by handling infected sheep, usually by handling their mouths and touching the lesions.  In humans the disease typically occurs as round, ulcerative type sores on the hands or other areas that have contacted the infected sheep.   As with sheep, the lesions usually resolve spontaneously in 2 to 3 weeks.  Once infected with the Soremouth virus, most humans develop immunity lasting for years as well.  It is important to note that immune compromised humans should avoid contact with the Soremouth virus.  The disease in humans is called Ecthyma Contagiosum by physicians.

            There is no specific treatment for Soremouth and treatment is usually unnecessary.  Nutritional and fluid support may be needed for very young lambs or sheep that are unable or unwilling to eat and drink with the lesions.  There can be rare cases of bacterial secondary infection of lesions that require antibiotic treatment, maggot infestation that may require treatment, or mastitis requiring treatment in ewes with lesions on their udders.

            Although it is rare to experience death losses due to Soremouth, there can be economic losses due to inability to sell or ship sheep off of the farm during the outbreak (which can be a very prolonged period of time).  Sheep with Soremouth are denied entry to shows and sales, and most interstate health papers for sheep require a statement from the flock veterinarian that the flock is free of Soremouth.  This basically means that even sheep that are apparently not infected with Soremouth should not be shipped, sold, or shown if the flock is in the midst of a Soremouth outbreak.  These sheep could easily be carrying the virus without showing signs of the disease and be highly contagious.

            Prevention of Soremouth is extremely difficult due to these “silent carrier” sheep.  The best way to prevent Soremouth from entering a flock is to maintain a completely closed flock and to keep the sheep at home.  This is impractical for most shepherds, so the next best means of prevention is strict isolation and quarantine procedures for new additions to the flock and for animals returning home from shows.  Even with the utmost in biosecurity, however, Soremouth can still happen.

            Elimination of Soremouth from a flock is also extremely difficult.  If a naïve flock is infected with Soremouth, the virus will slowly spread through the entire flock.  After weeks to months the entire flock will have been exposed and infected and have immunity to the disease.  Typically the virus survives in the environment and infects the subsequent years lamb crop(s) and any new naïve additions to the flock.  This cycle tends to continue year after year, although the virus may eventually disappear altogether after several years.  Aggressive cleaning of the environment may help prevent future outbreaks in lambs, but this might be extremely impractical or impossible.

            There is a vaccine available for the management of Soremouth.  It is NOT recommended as a preventative measure in uninfected flocks.  It is a live, virulent vaccine that is scratched on the surface of the skin.  The vaccine actually CAUSES the Soremouth disease and creates infective scabs at the vaccination site.  These scabs will fall off and contaminate the environment.  The primary reason for using the Soremouth vaccine is so that Soremouth outbreaks can be timed- all sheep are infected at once and the outbreak will be started and finished in 3 to 5 weeks.  In this way losses at lambing or losses of sales can be prevented.  Typically the vaccine is given to lambs at about 2 weeks post-weaning age.  It is important to remember to wear gloves if using the Soremouth vaccine!

            In conclusion- if it looks like Soremouth it probably is Soremouth!  Any sheep with pimples or scabs on the nose, lips, or face should be considered contagious and treated accordingly.  The sheep should not be shipped, sold, or shown.  If even one sheep in a flock is showing these symptoms then it should be assumed that an outbreak of Soremouth is occurring, and no sheep from this farm should be shipped, sold or shown until it can be determined that the outbreak is finished.

            Remember to contact your flock veterinarian with any questions about Soremouth or other infectious/contagious diseases.

       

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