Sheep and goat pox are endemic in Africa, the Middle East, Asia Minor (Turkey) and Asia. In Europe, periodic outbreaks occur in Greece and Bulgaria (2013-2014, 2015, 2017). Affected animal species are sheep and goats. Infections of wild small ruminants have not been documented so far, but cannot be excluded. Human infection with sheep or goat pox virus is not known.
The import of sheep and goats from regions with endemic occurrence of sheep and goat pox (e.g. Turkey) is prohibited. The initial emergence of these animal diseases in Greece and Bulgaria could be attributed to illegal movements of individual infected animals in the course of transhumance and immigration movements, respectively, as well as to illegal trade in animals (EFSA Journal 2014;12(11):3885.). Movement of healthy animals within the affected EU Member States of Greece and Bulgaria only occurs with regard to breeding and slaughter. Further mechanisms of spread over geographically longer distances (e.g. via wild animals, birds or via vectors) have not been researched.
The causative agents of sheep and goat pox, sheep pox virus (SPPV) and goat pox virus (GTPV), belong to the genus Capripoxvirus. Sheep and goat pox viruses are double-stranded, enveloped DNA viruses (size: 170-260nm x 300-450nm). They occur in genetically distinct strains. Some of these viral strains may be specialized to the animal species named after them; however, some strains may infect both goat and sheep. Phylogenetically, sheep and goat pox viruses are distinct from Lumpy skin disease virus (LSDV), which is also a member of the capripox family; serologically, capripox viruses have yet to be differentiated.
The direct spread of the pathogens from infected to healthy animals takes place via aerosols containing pathogens through coughing, sneezing and vigorous head shaking. In the process, excretions containing pathogens (nasal and eye excretions, coughing mucus) are spread. Direct transmission of pathogens via open skin wounds in contact with infected animals is also possible. Sucking lambs and fawns can also become infected from the infected dam via skin lesions on the udder. Infected animals are already infectious at the first signs of skin lesions.
Indirect transmission occurs via arthropods (e.g. stable flies). Scientific studies on vectors are scarce. Virus-containing excretions in feed, water, wool, stable environment and transporters as well as poorly prepared or untreated hides of infected animals also contribute to the spread of the disease. The viruses can be detected in the saliva and nasal or ocular fluid of infected animals for up to 64 days, in skin lesions for up to 30 days, in crusts that have fallen off the lesions for up to 180 days, in urine for 15 days and in faeces for 61 days after infection. The viruses can persist in the environment for extended periods of time-for example, up to 180 days in pastures or 6 months in the shade in a barn building. The viruses are susceptible to temperatures above 70 °C (65 °C/30min., 56 °C/2h). Preferred pH environment is between 6.6 and 8.6. High alkaline or acid pH destroy most pathogens. 1 % formalin or chloroform, 2-3 % sodium hypochlorite and some other virucides can inactivate the viruses.
The severity of the disease depends on the virulence of the virus strain, the breed and the age of the host animals. The course of the disease and the severity of symptoms are more pronounced in homologously infected animals. Young animals are more severely affected than older animals; morbidity is 70-90 %, mortality over 50 %. Mortality can be close to 100 % in lambs and fawns. Recovered animals have immunity to new infections throughout their lives.
Infection of animals usually occurs through open skin wounds or through the respiratory organs by pathogen-carrying aerosols. The appearance of first skin lesions begins 6 days after infection. By day 6, most animals are not infectious. The first symptoms are nasal and ocular discharge, fever (40-42 °C), respiratory problems, loss of appetite and depressed behaviour. Skin lesions first appear on the face, around the lip and nose region, and on the eyelids. Skin lesions are often also found on the udder and base of the tail, and sometimes under the wool. Smallpox lesions may occur in almost all internal organs - the oral cavity, nasal cavity, tongue, lungs and mucous membranes of the digestive and respiratory tracts. Lymph nodes, liver and spleen are affected to a lesser extent. After 21 dpi, recovery of the animals is possible. Animals no longer show clinical signs but may shed pathogens for up to 64 days after infection. In lambs, disease symptoms are more pronounced. Due to the painful lesions in the mouth, nasal area, respiratory tract and digestive tract, the young animals often refuse to eat and starve to death.
Sheeppox and goatpox are notifiable animal diseases. The control of both diseases is therefore based on
- the prevention of the introduction and spread of the pathogen due to trade restrictions with regard to animal trade and trade in animal products from affected countries
- the early detection of the diseases
- the "stamping out" method (culling of infected and suspected animals).
In case of outbreaks of sheep and goat pox, restrictions on the movement of animals and animal products as well as the establishment of protection zones around outbreak foci or other disease-specific restrictions are to be expected. After the culling of affected livestock, intensive cleaning and disinfection of the stables as well as a waiting period before new stocking are a prerequisite for renewed stocking. The observation and examination of sentinel animals is important for the further occurrence of infections.Attentuated live vaccines are available, but these are not licensed in the EU. Diagnostically, it is not possible to distinguish between vaccinated animals and those infected with a field strain. Prophylactic vaccination is prohibited in all EU countries.