Lumpy skin disease
Aetiology Epidemiology Diagnosis Prevention and control References
AETIOLOGY
Classification of the causative agent
Virus family Poxviridae, genus Capripoxvirus
Resistance to physical and chemical action
Temperature: Susceptible to 55°C/2 hours, 65°C/30 min pH: Susceptible to highly alkaline or acid pH Chemicals: Susceptible to ether (20%), chloroform, formalin (1%), and some detergents, e.g. sodium dodecyl sulphate Disinfectants: Susceptible to phenol (2%/15 min) Survival: Survives for long periods at ambient temperature, especially in dried scabs EPIDEMIOLOGY
- Morbidity rate 5-85%
- Mortality rate very variable
Hosts
- Cattle (Bos taurus, zebus, domestic buffaloes)
- Oryx (Oryx beisa), giraffe (Giraffe camelopardalis) and impala (Aepyceros melampus) are susceptible to experimental infection, but the role of wild fauna still has to be clarified. LSD virus will also replicate in sheep and goats following inoculation
Transmission
- Transmission may occur via infected saliva in the absence of an insect vector. Though no specific vector has been identified to date, mosquitoes (e.g. Culex mirificens and Aedes natrionus) and flies (e.g. Stomoxys calcitrans and Biomyia fasciata) could play a major role
Sources of virus
- Skin and cutaneous lesions (virus may survive 40 days in lesions), crusts
- Saliva, nasal discharge
- Milk
- Semen
- Muscles
- Spleen
- Lymph nodes
- There is no carrier state
Occurrence
Until 1988 LSD was confined to sub-Saharan Africa, but then spread into Egypt. As of 1995, there has been only one laboratory confirmed outbreak of LSD outside Africa, in Israel in 1989, which was eliminated by slaughter of all infected and in-contact cattle, and vaccination
For detailed information on occurrence, see recent issues of World Animal Health and the OIE Bulletin
DIAGNOSIS
Incubation period is approximately 12 days
Clinical diagnosis
LSD symptoms range from inapparent to severe disease
- Fever (40-41.5°C) either transitory or lasting up to 2 weeks
- Swellings or nodules of 1-5 cm in diameter and larger, in the skin. Generalisation usually occurs
- Depression, anorexia, excessive salivation, oculonasal discharge, agalactia and emaciation
- Painful nodules, especially in the skin of the muzzle, nares, back, legs, scrotum, perineum, eyelids, lower ear, nasal mucosa, oral mucosa and tail. Nodules affect the whole skin, the subcutaneous tissue and sometimes the musculature. In the course of the disease, the nodules may become necrotic and sometimes deep scabs form (which are called 'sitfast')
- Lameness resulting from inflammation and necrosis of tendons, and from severe oedema of brisket and legs
- Superficial lymph nodes draining areas of the infected skin may become enlarged to four-to-ten times their normal size
- Complications:
- secondary bacterial infection of teat - lesions which may lead to severe mastitis and loss of the quarter
- secondary bacterial infection of tendon and joint which may result in permanent lameness
- abortion, intrauterine infection, and temporary sterility in bulls and cows may occur
Lesions
- Nodules involving all layers of skin, subcutaneous tissue, and often adjacent musculature, with congestion, haemorrhage, oedema, vasculitis and necrosis
- Enlargement of lymph nodes draining affected areas with lymphoid proliferation, oedema, congestion and haemorrhage
- Pox lesions of mucous membrane of the oral and nasal cavities, and sometimes the pharynx, epiglottis and trachea
- Oedema and areas of focal lobular atelectasis in lungs
- Pleuritis with enlargement of the mediastinal lymph nodes in severe cases
- Synovitis and tendosynovitis with fibrin in the synovial fluid
- Pox lesions may be present in the testicles and urinary bladder
Differential diagnosis
- Pseudo lumpy skin disease
- Bovine herpes mammillitis
- Dermatophilosis
- Ringworm
- Insect or tick bites
- Besnoitiosis
- Rinderpest
- Demodicosis
- Hypoderma bovis infection
- Photosensitisation
- Bovine papular stomatitis
- Urticaria
- Cutaneous tuberculosis
- Onchocercosis
Laboratory diagnosis
Procedures
Identification of the agent
- Electron microscopy
- Inoculation of primary cell culture of lamb or calf testis and:
- microscopic examination
- haematoxylin and eosin staining of intracytoplasmic inclusion bodies
- direct immunofluorescent staining
- virus neutralisation
- ELISA
Serological tests
- Indirect fluorescent antibody test
- Virus neutralisation
- ELISA
Samples
Identification of the agent
- Skin biopsy from an early lesion:
- a portion is fixed for histopathological examination
- a portion dispatched in a transport medium is used for virus isolation (see Manual)
- Lesions (even dry crusts) removed from the skin, subcutis, or oropharynx of dead animals
Serological tests
- Frozen sera from both acute and convalescent animals
PREVENTION AND CONTROL
No specific treatment. Strong antibiotic therapy may avoid secondary infection
Sanitary prophylaxis
- Free countries: survey of importation of livestock, carcases, hides, skins and semen
- Infected countries:
- strict quarantine to avoid introduction of infected animals in to safe herds
- in cases of outbreaks, isolation and prohibition of animal movements
- slaughtering of all sick and infected animals (as far as possible)
- correct disposal of dead animals (e.g. incineration)
- disinfection of premises and implements
- vector control in premises and on animals
- With the exception of vaccination, control measures are usually not effective
Vector control in ships and aircraft is highly recommended
Medical prophylaxis
- Homologous attenuated virus vaccine:
- Neethling strain: immunity conferred lasts up to 3 years
- Heterologous attenuated virus vaccine:
- sheep pox vaccine, but may cause local, sometimes severe, reactions
- follow manufacturer's instructions. Not advised in countries free from sheep and goat pox
REFERENCES AND OTHER INFORMATION
- Reference experts and laboratories
- Classified as an OIE List A disease (A070)
- Chapter 2.1.7. in the Manual of Diagnostic Tests and Vaccines for Terrestrial Animals.
- Terrestrial Animal Health Code
- World Animal Health .
- Current Animal Health Status (Disease Information)
---------------------------------------------
Contact : scientific.dept@oie.int