Explanation of brucellosis

Press, Volume CXI, Issue 32588, 23 April 1971, Page 14

Explanation of brucellosis

There have been frequent references in the newspapers in recent weeks to the disease of cattle known as brucellosis—to the need for a national scheme of testing and slaughter to safeguard the meat trade, the Government’s request to the Meat Board to meet half of the cost and its rejection by the electoral committee of the board, and the Government’s subsequent intention to proceed with the scheme on a reduced scale. While the term brucellosis is used very frequently, to those particularly on the fringes of farming the nature of this disease may not be clearly understood.

Mr H. G. Stockdale, regional veterinary officer of the Department of Agriculture in Christchurch, who earlier initiated the brucellosis testing and slaughtering scheme in Taranaki, said this week that brucellosis was caused by a bacterium or germ called Brucella abortus. It was responsible for abortion in cattle and if an animal aborted in about its seventh month of pregnancy the calf was usually bom dead and the mother’s milk production was markedly reduced—to the extent that often it was uneconomic to keep an animal in the herd. If the abortion occurred closer to the ususal calving

date —about eight to nine months through pregnancy —the calf could be bom alive and milk yield could be more or less normal.

Brucellosis was a highly contagious disease—particularly about the time that the animal aborted. Most of the spread of the disease took place then as a consequence of the foetal fluids, foetal membranes and uterine discharges, that were teeming with the disease organisms, contaminating the pasture which was then eaten by other animals. An animal that aborted usually continued to have uterine discharges containing these organisms for several weeks.

From a human point of view the danger in brucellosis is that it can cause of undulant fever, which can be caught by drinking raw milk or from contact with infected animals. Pasteurisation of milk, however, destroys the organisms in milk. There is little risk from meat, which is also rendered safe by cooking. Questioned about the place of vaccination, which is required to be done to all heifer calves between three and six months of age, in the control of the disease, Mr Stockdale said that preliminary vaccination was a recognised means of reducing the incidence of a

disease, such as brucellosis, to a point where a testing and slaughter policy was economically feasible. This meant that a reduced number of cattle had to be slaughtered. It was, however, usual to continue vaccination for a number of years, even after brucellosis had been controlled, as an insurance against the accidental reintroduction of the disease into brucellosis-free herds containing highly susceptible animals. Mr Stockdale recalled that the Government had allocated money to start a testing and slaughter scheme in December, 1969, in the Taranaki and Egmont counties and in the Helensville area. Subsequently more money had been made available for the continued testing in these areas and the scheme had also been expanded to take in the counties in Taranaki of Clifton, Inglewood, Stratford and Eltham. Recently the Government had allocated another sl.Bm to permit the expansion of testing in the Taranaki and Helensville areas and the introduction of a new scheme for five counties in the Waikato. For some time, said Mr Stockdale, a private scheme for brucellosis eradication had been in progress in the Christchurch town milk supply herd.