BACTERIAL DISEASES: BRUCELLOSIS

This is an infectious contagious disease primarily affecting cattle, swine and goats. It is caused by brucella organisms characterized by abortion in females, orchitis and infection of accessory sex gland in males and infertility in both sexes. The disease affects sheep causing abortion and infertility. It affects horses causing abortion, poll evil and fistulous withers. It cause undulant or Malta fever in humans. It is worldwide in distribution. It has been eradicated in some Scandinavian countries such as USA, France and UK. The disease is important because it is of economic and public health significance.

Brucellosis in goats

It is caused by Brucella melitensis but occasionally, Brucella abortus is involved. Infection arises through ingestion of the organism, conjunctival, vaginal and by inoculation. Also by contact through intact skin. It causes abortion about 4th month of pregnancy.
Clinical signs
They are as follows:
Abortion
Keratitis
Chronic bronchitis
Mastitis
Lameness
Unthriftiness
Hygroma
Orchitis
Osteoarthritis
Synovitis
It may cause nervous signs in sheep.
Diagnosis
This is based by bacterial examination of milk (milk ring test) or of the aborted fetus.
It is also diagnosed by serum agglutination test.
Control
Vaccination
Slaughtering reacting animaland compensation paid to the farmer.
Two types of vaccines available are:
Attenuated Brucella melitensis vaccine (strain Rev. 1vaccine).
Killed Brucella melitensis H38 adjuvant oil vaccine.
Treatment 
Not advisable.

Brucellosis in sheep

It is caused by Brucella ovis. This has been reported in Australia and Brucella melitensis also affect sheep.
Clinical signs
They are as follows:
Acute edema and orchitis
Fever
Depression
Increased respiratory rate
Epididymis is enlarged and hard and testicles atrophy.
Abortion in ewes is characteristic of the infection.
Births of weak lambs and stillbirth
Treatment is not undertaken except in valuable rams.
In this case, streptomycin and chlortetracycline are given in high doses.
Control
Test and slaughter, pay compensation to the farmer.
Vaccination using Brucella abortus strain 19 vaccine because it gives high antibody titres of the serum or Brucella abortus killed adjuvant vaccine.
It is preferable to give Brucella melitensis strain Rev.1 vaccine.
Do not vaccinate within two months of mating.

Bangs disease/Bovine brucellosis

This is widespread and of economic and public health importance in most world countries especially in dairy cattle. It is characterized by abortion in late pregnancy and high rate of infertility. The causative organism is Brucella abortus. Brucella melitensis occasionally affects cattle. The organism can be recovered from pregnant uterus, fetus, fetal membranes, milk and hygroma fluid. Cattle of all ages are affected. Infection is by ingestion, through intact and broken skin, through intact or broken conjunctiva and contamination of the udder in the course of milking.
Clinical signs
Abortion after 5th month of pregnancy in cows
Retained placenta
Metritis which may be acute with septicaemia and death following or chronic leading to sterility.
In the bull, orchitis and epididymitis. Occasionally, one or both scrotal sacs may be affected with acute painful swelling leading to sterility. There may be necrosis of scrotum leading to sterility in bulls. Infected semen can spread the disease by artificial insemination. There is hygroma of knee joints. Isolation is by guinea pig inoculation or by culture.
There are several serological tests used in diagnosis of bovine brucellosis and they are as follows:
Rose Bengal plate test
Slide agglutination test
Tube agglutination test/serum agglutination test
ELISA
Coombs agglutination test
Brucellin skin test is also done. Brucellin is an antigen obtained from brucella
Control and eradication
The disease has been eradicated from Scandinavian countries like Sweden, Norway and Denmark.
Bovine brucellosis can be controlled with effective vaccination programme or eradicated using test and slaughter programme. The vaccine used are Brucella abortus strain 19 vaccine (attenuated live vaccine) and is given to cows at 4 months of age. It is known to protect animals for 7 years.
Brucella abortus killed 45/20 adjuvant vaccine protect animals from 2 years and used for diagnosis of carrier animals.