Brucellosis Indirect ELISA (iELISA)

Brucellosis is a bacterial disease of cows and buffaloes that can cause abortion in late pregnancy, retained placenta, weak calves, poor fertility and a fall in milk. Infected animals shed the bacteria in aborted material, birth fluids and milk, and the infection can spread through a herd. Brucellosis can pass to people, so wear gloves when handling aborted calves, the afterbirth, milk or other samples, wash your hands well and see a doctor if you feel unwell. Positive animals are handled under veterinary and government guidance.

ELISA stands for enzyme-linked immunosorbent assay. It is a lab method in which antibodies in the sample stick to Brucella antigen fixed in a small well, and a colour change shows how much antibody is present. The indirect ELISA, or iELISA, is more sensitive than plate tests such as the RBPT, so it can pick up lower antibody levels. It can be run on serum from one animal or on milk. A pooled milk sample from several animals, for example from the collection can, may be used to screen a herd, and individual animals are then tested if the milk result is positive.

Vets may use the iELISA after a positive plate test, for herd screening, or when brucellosis is suspected after an abortion. Animals vaccinated against brucellosis can also have antibodies, so the vaccination history matters. A negative result does not always rule out infection, especially soon after an animal was infected. A milk test only covers animals that are giving milk. A registered veterinarian reads the result together with the animal's history, signs and other tests, and decides on next steps with the animal husbandry department where needed.