ARCHIVE: Contagious agalactia

If you suspect signs of any notifiable disease, you must immediately notify a Defra Divisional Veterinary Manager.

Animals affected

Sheep and Goats.

Clinical signs

Following an incubation period of 5 to 7 days from subcutaneous inoculation and up to 60 days from natural exposure, body temperature rises to a range from 41 to 42C. The period of fever corresponds to the time of septicaemia. During early stages, infected animals become depressed and anorectic, and some may die. As it progresses, the disease usually develops signs of keratitis and arthritis and, in female sheep, mastitis and abortion.

The acidity of the milk from infected udders changes from a normal pH 6.8 to pH 7.8, becomes yellow in colour and, on standing, separates into a light green supernatant layer and a grumous sediment. Gradually, the udder atrophies and the milk yield diminishes. Joints, especially carpal and tarsal, become swollen, painful, and lame. In some animals, a joint may rupture and discharge exudate.

One or both eyes may become infected, leading to impaired vision and blindness. Depending on the stage of disease development, the infected eye may show congestion and swelling, punctiform keratitis with. each opaque focus measuring up to 1mm in diameter, keratitis with yellow opacity of the cornea, or rupture of the cornea.

Ewes in the third trimester of gestation may abort either dead or living infected lambs and later develop vaginal discharges. Some outbreaks show a preponderance of either udder, eye, or joint involvement. Israeli veterinarians assert that the disease in their country rarely causes abortion.

At necropsy, animals that have died during early acute stages often present generalized peritonitis. In sacrificed sheep, the pathologic changes vary with the stage of lesion development. The infected udder is grossly atrophic in either one or both halves of the organ. Microscopically, the chronic inflammatory reaction in the stroma shows increased fibrosis and a reduced number of glandular acini.

Post Mortem

Infected joint capsules are oedematous, and the synovium may contain clumps of fibrin. Articular surfaces maybe eroded and occasionally ankylosed. In early stages of keratitis, the cornea is oedematous and infiltrated with leukocytes. In advanced stages, abundant purulent exudate infiltrates both cornea and the ciliary body. If corneal rupture has occurred, anterior synechia may have formed.

 

Page last reviewed: 20 December 2007
Page published: 5 February 2003