Contagious agalactia

Early signs are fever, inappetence, lethargy and reluctance to follow the flock. In lactating ewes and does the milk changes in colour and consistency and yield falls, often failing within 2 to 3 days. Lameness from arthritis and keratoconjunctivitis together affect about 5 to 10% of infected animals, and the three signs are rarely seen in one animal. Pregnant animals may abort. Kids fed infected milk develop septicaemia, arthritis and pneumonia. At necropsy the udder is atrophied and fibrotic, joint capsules are oedematous with fibrin, and the cornea shows oedema with purulent exudate.

Contagious agalactia is caused mainly by Mycoplasma agalactiae; M. capricolum subsp. capricolum, M. mycoides subsp. capri and M. putrefaciens produce a clinically indistinguishable syndrome, more often in goats. The organisms enter by oral, respiratory, mammary or possibly venereal routes, cause bacteraemia and localise in the udder, joints and eyes. In the udder they cause interstitial mastitis that ends in fibrosis, atrophy of glandular tissue and failure of milk production. In joints, synovial fluid accumulates and capsules become oedematous with fibrin deposits, sometimes progressing to ankylosis. Keratoconjunctivitis damages the cornea and can cause blindness. Septicaemia with arthritis and pneumonia, especially from M. mycoides subsp. capri and M. capricolum, kills young kids.

Sheep and goats are the main hosts; wild ibex and chamois are also infected, and antibodies have been found in South American camelids. The disease is endemic around the Mediterranean, in North Africa, and across much of the Middle East and Asia, with frequent outbreaks in Iran and reports from Turkey, Iraq, Jordan and Sudan; M. capricolum is highly pathogenic particularly in North Africa. Spread occurs through milk and colostrum, milking equipment and milkers' hands, and secretions from the eyes, nose and joints. Kids and lambs are infected by suckling. Carriers can excrete the organism in milk for years, and hot, humid summers favour flare-ups in carrier flocks. Incubation ranges from a few days to about two months.

Mastitis caused by staphylococci, streptococci, enterobacteria or Corynebacterium is separated by bacterial culture, and arthritis from small ruminant lentivirus infection is considered in lame animals. The four causal mycoplasmas cannot be told apart clinically and need isolation, PCR or serology; a putrid smell of the milk often first signals M. putrefaciens in a herd. Bulk-tank milk culture or PCR screens whole flocks.

Mammary gland, joints and synovial membranes, eyes (conjunctiva, cornea), lungs and pleura, reproductive tract, bloodstream

Monitor flocks by bulk-tank milk testing; test replacement animals; cull or isolate infected stock; improve milking hygiene; pasteurise milk. Inactivated and live M. agalactiae vaccines exist but protection is limited.

High morbidity, lower adult mortality; mortality reached over 40% in one Sicilian outbreak of Mycoplasma mycoides subsp. capri. Treated animals can remain permanent carriers, so culling or isolation is generally advised.