B154 - CONTAGIOUS AGALACTIAE

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B154 - CONTAGIOUS AGALACTIAE

Nature of the disease
Contagious agalactiae is contagious disease of goat and sheep causing agalactiae, arthritis and keratoconjunctivitis. Several mycoplasma can cause the disease: Mycoplasma agalactiae, M. capricolum subsp. capricolum, M. mycoides subsp. mycoides LC (MmmLC) and M. putrefaciens.
Classification
OIE, List B disease
Susceptible species
Caprine and Ovine
Distribution
Mainly in the Mediterranean region, sporadically in America and Asia. In the Pacific Region, only M. putrefaciens has been reported in Australia.
Clinical signs 
The incubation period ranges from 1 to 8 week and the disease forms vary from chronic to acute. Symptoms include
  • Elevated temperature, loss of appetite,
  • Drop in milk yield or kids growth rate,
  • Mastitis,
  • Swelling of lymph nodes from the udder,
  • Arthritis mainly on the carpal and tarsal joints,
  • Occasionally abortion and vulvovaginitis,
  • Keratoconjunctivitis,
  • Pleuropneumonia,
  • Mortality can be high in kids, in adults it is usually lower than 20%
Post-mortem findings 
When animals die of the acute disease gross lesions include:
  • Congestion of the musculature, 
  • Congestion of the spleen and liver, 
  • Arthritis with periarticular oedema, joint cavities filled with turbid or hemorrhagic fluid. 
Differential diagnosis 
Specimens required for diagnosis 
Differentiation of the different mycoplasma can be realised by isolation, biochemical tests, serological tests and PCR. Specimens should include milk, blood and synovial liquid from live animals and specimens of liver, spleen and joint fluid from dead animals.

Several serological tests are available and include complement fixation and ELISA but they do not permit the specification of the agent.
Transmission   
The disease spreads by ingestion of contaminated material such feed, water, or milk. The virus is shed in milk, urine, faeces, nasal and ocular discharges.

Contaminated fomites can transmit the organisms between premises. Transmission may also be by direct entry to the teat opening at milking or by inhalation of contaminated dust. 

Chronic carriers can shed the mycoplasma for months 

Risk of introduction   
The diseases is more likely to be introduced through importation of unapparent carriers  
Control / vaccines  
Treatment can be tempted with different antibiotics including tetracyclines and macrolides. 

Hygiene and management are particularly important to control the spread of the disease. 

Killed vaccines for MmmLC. Live vaccines show good result against M. agalactiae infection, but are not acceptable in all countries.

References
  • Caprine arthritis/encephalitis, In Merck Veterinary Manual, National Publishing Inc. Eight ed, 1998, Philadelphia, p 523-526
  • Caprine arthritis/encephalitis, In Veterinary Medicine, Saunders, Eight ed, 1997, London p. 1110-1112
  • Office International des Epizooties, 2002
  • Office Vétérinaire Fédéral Suisse