Bovine Brucellosis

Synonyms

'Bang's disease'

Introduction

Brucellosis is an abortive disease of cattle and also sheep and goats, caused by the bacteria Brucella abortus. It has been eradiated in the UK and other countries worldwide, and is now notifiable in this country, but it is still prevalent in Ireland. The disease is zoonotic and causes 'Undulant Fever' in humans. Transmission is by ingestion (faeco- oral) but may also be by entry through skin abrasions, inhalation or transplacentally. The disease in excreted in foetal fluids for 2- 4 weeks following abortion and at subsequent parturitions without abortion. It is also excreted intermittently in the milk for many years.

Clinical Signs

Abortion is the primary clinical sign, usually after five months of gestation, due to placentitis. In naive herds, this will often occur as an abortion storm and in affected herds, abortions will happen sporadially and there will be an associated infertility problem within the herd. There will be prevalence of decreased fertility in bulls, as well as cows.

Lameness, epididymitis, decreased milk production in cows and mastitis may be present in affected herds. The disease is not usually transmitted venereally, but the disease in males may cause orchitis.

Diagnosis

Clinical signs and history.

Samples should be taken from the recently aborted calf and sent to the laboratory. Samples for culture should include foetal lung or placenta. These can also be used for Brucella antigen testing by immunostaining technology. Serological tests are not of a high efficacy, but are also used. The ring test on milk is used on milk to survey the herd for signs of Brucellosis and the Rose Bengal complement fixation test is used on suspect cases.

Treatment and Control
 

Cattle are rarely treated for Brucellosis as it is either notifiable or an eradication system is in place (e.g in the United States), so most infected animals are destroyed. If treatment is required, oxytetracycline over a long period of time has been shown to reduce shedding, but not eliminated the disease.

Vaccination of heifers against B. abortus in endemic regions by Strain S19, a live attenuated vaccine, stimulating a cell-mediated immune response. The vaccination of young animals interferes with serological testing. The 45/20 bacterin vaccine is less effective and the newer RB51 vaccine has no LPS O-antigen therefore not detected by serological tests and gives good protection.

The control measures in place are as mentioned above- Test and slaughter program to eradicate bovine brucellosis. This has been effective in the UK. Other control measures in an outbreak include humane destruction of all infected animals, isolation of pregnant cows to prevent further infection and careful handling of all foetal tissues if an abortion does occur. Do not allow other cattle to be in contact with an aborted foetus. Disinfection of an area infected with Brucellosis is vital to try and eliminate it from a farm.

References

Andrews, A.H, Blowey, R.W, Boyd, H and Eddy, R.G. (2004) Bovine Medicine (Second edition), Blackwell Publishing
Radostits, O.M, Arundel, J.H, and Gay, C.C. (2000) Veterinary Medicine: a textbook of the diseases of cattle, sheep, pigs, goats and horses Elsevier Health Sciences