The parasites in question are two different tapeworms of the echinococcus species, including E. multilocularis and E. granulosus, which can usually grow to a length of 8 mm.

Although more often found in animals, if humans swallow the parasite eggs, the resulting larvae can sometimes penetrate the intestines and settle in the lungs, liver, or brain causing large cysts.

• Austrian researchers tested 152 pig farmers (avg. age 42 years) and 50 subjects who had not been exposed to farm animals (avg. age 41 years) for serum antibodies against a variety of viral, bacterial, and parasitic agents often found in farm animals.

• All subjects lived in the same province of Austria.

• Researchers compared their results to those of a similar study involving 137 veterinarians from the exact same Austrian province.

• Ten of the 152 farmers (6.6 percent) had serum antibodies against the parasites, as compared with none of the 50 unexposed subjects and none of the 137 veterinarians.

• A thorough examinations of the 10 positive-testing farmers revealed liver cysts in 3 of them (2.0 percent of the overall group of 152 farmers).

The authors therefore calculated that the rate of infection in these pig farmers (2%) was 50 times higher than the rate in the general Austrian population (in which it is 0.04 percent).

The authors suggest that a screening program be established for the detection of echinococcal parasitic infections in pig farmers.

New England Journal of Medicine September 7, 2000; 343: 738-9.