Contagious Ecthyma ( Orf or Contagious Pustular Dermatitis or Sore Mouth) in Sheep and Goats
Orf also known as:
Other name: Orf , Contagious Pustular Dermatitis , Sore Mouth,Scabby Mouth, Ecthyma Contagiosum, Contagious Pustular Stomatitis, Infectious Labial Dermatitis,
Orf is an infectious viral skin disease of mainly sheep and goats. It mainly affects the lips of young animals. The disease is more severe in goats than in sheep.
This is an acute contagious, debilitating and economically important zoonotic viral disease of sheep, goats and some other domesticated and wild ruminants. The affected animal manifests painful skin lesions around the mouth and muzzle on account of which anorexia or starvation usually noticed (Constable et al., 2017). Typical clinical signs in mucous membrane of the oral cavity, tongue, lips and teats are developed sequentially in form of papules, vesicles, pustules, scabs which are important for diagnostic point of view. Contagious ecthyma (Orf) virus belongs to the genus Parapoxvirus of the family Poxviridae (Murphy et al., 2012; Nadeem et al., 2010). Direct / Indirect contact can transmits the virus through broken, scarified or damaged skin. Orf cases are more often noticed in pasture or manual feeding under drought conditions. Orf virus is hardy as it can resist dry environment and can continue to live for considerable length of time ranging from months to years in dry environments (Radostits et al., 2007). Although this disease was reported in all seasons around the world (Nandi et al., 2011), however, outbreaks of the disease in grassland or flattening system are frequently noticed in late summer, autumn and winter. The probability of occurrence of orf infection is more in new born lamb or within a period of 3 to 4 months after birth (Lovatt et al., 2012; Reid et al., 2007). Herd prevalence rates of this disease usually are higher in goats than sheep (Mondal et al., 2006; Scagliarini et al., 2012). Some sheep and goats may act as carrier animals without showing any sign of disease.
It is characterised by the development of pus-filled and scabby wounds on the muzzle and lips of lambs and kids, by the appearance of similar lesions on the teats of nursing ewes and nanny goats and it can also produce lesions on the teats of cows.
The cause is a pox virus related to that which causes Pseudo Cow Pox and Bovine Papular Stomatitis. The disease occurs worldwide. It occurs mainly in young lambs and kids and occasionally in mature animals which do not have immunity from natural exposure.
Contagious ecthyma is a highly contagious, zoonotic, viral skin disease that affects sheep, goats and some other domesticated and wild animals. The skin lesions are painful and often occur on the mouth and muzzle, where they can cause anorexia or starvation. Lesions on the udder may result in the abandonment of offspring, and foot lesions can cause transient lameness. Secondary bacterial infections can occur and, in rare cases, the lesions may extend into the internal organs. Although contagious ecthyma usually resolves spontaneously and the mortality rate is generally low, deaths can occur from sequelae such as secondary infections or failure to nurse. The economic impact can be significant. Severe generalized infections have also been described occasionally. Most infections in humans are localized and heal spontaneously; however, large, poorly healing lesions can occur in people who are immunosuppressed.
Mode of spread
This is probably the most common viral disease of sheep. It is spread by contact. The source of new outbreaks in sucking lambs is believed to be a flare up of a persistent infection in a stressed ewe following lambing, not, as was previously thought, from scabs lying on the pasture. The virus then spreads rapidly to other lambs in the flock, both directly and indirectly. The incidence within a flock may be as high as 90%. The few deaths which occur are the result of extension of wounds within the respiratory tract, but the mortality rate may reach 15% if the lambs are badly cared for or if secondary infection or fly strike occurs.
The disease is commonest in lambs aged 3-6 months, although lambs aged 10-12 days and adults can be severely affected. Outbreaks can occur at any time but are most common in dry conditions. Recovered animals are solidly immune for 2-3 years but they do not transfer this immunity in their colostrum to their lambs, which are therefore susceptible to infection.
Clinical History and Diagnosis
The period of incubation the disease varies from 4 to 8 days with an slight rise in temperature intially, development of papules and pustules often at oral commissures, skin of lips and nose followed by thick, tenacious scabs covering a raised area of ulceration, granulation and inflammation. Similar skin lesions of few milli meters to several centimeters are also seen in the lips of the kids particularly below two months of age and disseminated to the skin of face, ears, feet, flanks, and scrotum . In the mouth of mountain-goats, dry, brown, proliferative lesions are prominent on the markedly edematous hyperemic lips, but severity diminishes toward the commissures. Lesions of the oral cavity especially on the gum become moist, reddish-brown and in certain sites, intensely hyperemic . The affected kids and lambs unable to graze and also unable to suckling from doe . The affected lesion and scabs are fragile and bleed easily and lead to anorexia. Some lesions may moist and dirty lead to foul smelling. In some cases, it may leads to mastitis due to secondary bacterial infection of other bacteria like Mannheimia haemolytica and Gram-negative Streptococci. The venereal form of Orf leads to appearance of papule and vesicles on the scrotum of rams and ulcers on the skin of the vulva of ewes .
Diagnosis of Orf is based on the history and clinical signs of disease. Other laboratory techniques like Electron microscopy(EM), serological techniques like agar gel precipitation test(AGPT), agglutination test, complement fixation test (CFT), enzyme linked immune-sorbent assays (ELISAs), serum neutralization test (SNT), histopathology of affected tissues, nucleic acid based assays including polymerase chain reaction (PCR) and restricted fragment length polymorphism (RFLP) analysis.
Signs of Orf
* The first wounds develop at the corners of the mouth, from here spreading onto the muzzle and nostrils and, to a lesser extent, into the mouth
* Occasionally wounds are found on the feet, usually between the toes or around the coronet
* Ewes nursing infected lambs may develop wounds on the udder and the teat may become encrusted with multiple wounds
* The wounds start as small pimples and progress pus-filled wounds before encrusting. Several small wounds may join together to form large scabs
* The scabs often split and are sore to the touch. They crumble easily but are difficult to remove from the underlying granulation
* Affected lambs suffer a severe setback because of restricted suckling and grazing
* During the course of the disease – 1-4 weeks- the scabs drop off and the tissues heal without scarring
* Lesions may also develop at castration and docking sites, and on the crown of the head of hornless rams due to head butting.
Treatment:
During the outbreak, the isolation of affected animals and the quarantine of new animals in the herd are maintained on compulsory basis. Sick animals should be separated, fed and treated after feeding the herd. Consumption of milk from does that present lesions on the teats and udder should be avoided. Proper preventive measures for the cure of disease should be maintained. Proper disinfection of the houses and premises of the animal herd and incineration of all infected materials extracted from sick animals are required to reduce the risk of new infection. Vaccination with live virus vaccine should not be recommended on a farm having no previous history of Orf outbreak as the live virus may contaminate environment. Although it is a self-limiting disease hence the symptomatic treatment can be given with antiseptic dressing is helpful. As to prevent the secondary bacterial infection a As secondary bacterial contamination in Orf virus infection is not uncommon, therefore topical and systemic antibiotics must be used in treatment schedule. Occasionally levamisole as an immunostimulant is indicated in Orf virus infection (Wilson et al., 2002) [32]. Debilitated sheep need to be treated with 10% glucose saline intravenously (Rao and Bandyopadhyay, 2000) [24]. Lesions should be washed with 1:100–1:10,000 KMnO4 lotion and application of 1:10 boric acid (Rao et al., 1994) [23] , mild antiseptic (Singari et al., 1990) [29] or antibiotic ointment (Nandi et al., 1999) [21] topically with parenteral antibiotic injection is recommended to prevent secondary bacterial complications.
Prevention and Control
In the early stages of an outbreak, affected animals should be isolated and the remainder vaccinated. Vaccination is of little value when a large number of animals are already infected.
Persistence of the disease in a flock is common and in such circumstances the lambs should be vaccinated when about 1 month old. A small amount of live vaccine is brushed over light scarification of the skin, usually on the inside of the thigh.
For best results a second vaccination about 2-3 months later is suggested.
A week after vaccination there should be a local reaction with the formation of scabs at the site of vaccination and vaccinated animals should be segregated from unprotected stock until the scabs have fallen off.
Sheep that have recovered from natural infection are highly resistant to re-infection and vaccination is completely effective for at least 2 years.
Contagious ecthyma, caused by parapox virus, is one of the most common skin diseases of sheep, goats and other domesticated as well as wild ruminants. It is responsible for producing skin lesions at the area of mouth, lips and nose for the incubation period of approximately, one week. At present, the CE and its allied impediments have the status of disease of worldwide occurrence which can arise in rural as well as urban areas due to less awareness, casual negligence and through religious or cultural practices involving animal handling and slaughtering. Since Orf is a zoonotic disease, so its handling and management should be done very vigilanty. Though the disease is self-limiting, secondary bacterial infections lead to complications that may lead to mortality. The most effective means of controlling losses is vaccination. Vaccination of susceptible animals with a potent and efficacious vaccine surrounding the infected flock(s) should be considered (ring vaccination).However, feasibility of eliminating infected and exposed flocks by slaughter, properly disposing of animals and contaminated material and cleaning and disinfecting contaminated premises and equipment should also be considered. Depopulation of infected and exposed flocks should be implemented if limited spread has occurred. If the disease has spread extensively, massive vaccination and control of animal movements from the area represent a viable and ideal strategy to control and then eradicate Orf (Nandi et al., 1999) [21]. Since the CE is a viral disease, there is no definitive treatment for infection in humans or animals. Antibiotics, anti-inflammatory drugs, antiviral drugs and surgical resection usually have only limited success.
Contagious ecthyma is a zoonotic disease that causes huge economic loses, so early detection and clinical management can resolve the condition early in the flock. Though, the disease is self-limiting and secondary bacterial infection causes the complication, so, antibiotics, antiinflammatory and topical therapy helpful in the recovery.
Compiled & Shared by- This paper is a compilation of groupwork provided by the
Team, LITD (Livestock Institute of Training & Development)
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Reference-On Request.
Contagious Ecthyma/Orf: A Debilitating Disease of Small Ruminants
