Milk-borne diseases. An epidemiological review

The epidemiology of raw milk-associated foodborne disease outbreaks reported in the United States, 1973 through 1992

OBJECTIVES

This study describes the epidemiology of raw milk-associated outbreaks reported to the Centers for Disease Control and Prevention from 1973 through 1992.

METHODS

Surveillance data for each reported raw milk-associated outbreak were reviewed. A national survey was conducted to determine the legal status of intrastate raw milk sales for the period 1973 through 1995.

RESULTS

Forty-six raw milk-associated outbreaks were reported during the study period; 40 outbreaks (87%) occurred in states where the intrastate sale of raw milk was legal.

CONCLUSIONS

Consumption of raw milk remains a preventable cause of foodborne disease outbreaks.

A study of the microbiological status of Irish farmhouse cheeses with emphasis on selected pathogenic and spoilage micro-organisms

Ninety-six 25 g samples from 25 Irish farmhouse cheeses, two Irish non-farmhouse cheeses and four foreign cheeses were evaluated for the presence of a variety of micro-organisms, namely, coliforms, faecal streptococci, Staphylococcus aureus, yeasts, moulds, salmonellas and shigellas. Seventeen cheeses, i.e. the soft and semi-soft types, were examined for Listeria monocytogenes. Most of the farmhouse cheeses are currently manufactured from raw milk, but some producers now use heat-treated milk. The incidence of coliforms and faecal coliforms was higher in soft, semi-soft and semi-hard cheeses than in hard types. High levels of contamination by faecal streptococci and non-pathogenic (coagulase-negative) Staph. aureus prevailed in a high proportion of the cheeses. Pathogenic (coagulase-positive) staphylococci, however, were also isolated from 50% of the cheeses, some of which were manufactured from pasteurized milk. Yeasts were found mainly in unpasteurized varieties, especially in the category of soft cheeses. Moulds were isolated from five non-mould-ripened cheeses, as well as from mould-ripened varieties. Salmonellas, shigellas and Listeria monocytogenes were not detected after direct enrichment.

Brucellosis in Northern Ireland. A serological survey

A serological survey for brucella antibodies has been carried out in Northern Ireland in an attempt to assess the effects of the brucellosis eradication programme in cattle which has been in progress since 1959. One thousand eight hundred and ninety four sera from blood donors, from farmer's lung tests, and from various groups occupationally exposed to cattle were examined by the serum agglutination test, the anti-human globulin (A.H.G.) (Coombs) test and the complement-fixation test.

The incidence of brucellosis in Northern Ireland is now less than it was 20 years ago, but is similar to that reported in a recent survey in England. It now appears that the principal method of transmission of brucellosis in the province is by occupational exposure rather than by drinking infected milk. Though it may be too early to make a serological assessment of the effects on human infections of brucellosis eradication in cattle, this survey provides a basis for future evaluation.

We thank Prof. O. L. Wade, Prof. P. C. Elmes and Dr W. R. Kerr for their encouragement and helpful advice; the Medical Officers of Health in Antrim, Armagh, Down and Fermanagh, Londonderry, and Tyrone, and in Belfast and Londonderry County Borough for help in obtaining blood samples; Dr M. C. Huth of the Northern Ireland Blood Transfusion Service, for sera; Dr D. W. R. Mackenzie and Miss H. E. Cairns for sera from the Mycology Diagnostic Laboratory; Dr J. H. Connolly for sera from the Virus Reference Laboratory, and for helpful advice; the farm workers and veterinary surgeons for volunteering blood samples; the technical staff of the Veterinary Research Laboratories for carrying out the tests.