Leptospiral serology in Scottish coal-miners.

The problem of leptospiral infection in coalminers became prominent in one area of the Scottish coaffields during the period 1940-52 when altogether 15 cases of Weil's disease were diagnosed or suspected in colliery workers out of a total manpower of some 8,000. Of those 15 cases, 11 were reported from a single colliery and four of these 11 died. Serological confirmation of the diagnosis was obtained in four of the non-fatal cases, but the swift course of the illness in the fatal cases did not permit the patients to survive long enough to enable typical antibodies to be detected. The clinical findings in most of the cases left little doubt as to the true nature of the disease. All those concerned were underground workers and worked in collieries known to harbour rats. The incidence of leptospirosis in rats in Scotland has been estimated at 44% of 117 rats in the Aberdeen district by Smith (1938) and 37% of 166 wild rats in East Lothian by Buchanan (1927). Since infected rats are known to shed numerous leptospirae in their urine over a long period, there was a strong possibility of frequent contamination of the pit with L. icterohaemorrhagiae and hence extensive contact with infection among the workers. In view of this, the relative rarity of clinical Weil's disease (an average rate over the 12 years of 0*02% per annum of 8,000 men in the area concerned) led us to investigate the possibility of the occurrence of further unrecognized infection. This possibility was illustrated by one of the Scottish cases which showed little constitutional upset and no jaundice, the diagnosis being established by a mounting titre of antibodies reaching eventually 1 in 10,000 for L. icterohaemorrhagiae. As far as subclinical infection is concerned, Smith and Davidson (1936) showed that 51 of 210 fish workers in Aberdeen gave serological evidence of previous infection with L. icterohaemorrhagiae. Of these 51 sera, 18 (866% of total) came from individuals with no clinical history. From the data supplied in a paper by Tiffany and Martorana (1942) on the incidence of leptospiral agglutinins in New York sera, the rates for positive findings among sewer workers and fish workers, showing no previous history of Weil's disease, were 11 of 515 (2-1%) and seven of 102 (6.9%) for these respective occupations. There appears to be no information available in the literature as to the occurrence of leptospiral agglutinins in the sera of normal coal-miners in Scotland.