Leptospirosis among the self-supporting convicts of Andaman Island during the 1920s--the first report on pulmonary haemorrhage in leptospirosis?

Several researchers had carried out investigations on the possibility of existence of Weil's disease in Andaman Islands during early 20 th century. The first report of a series of confirmed cases of leptospirosis that occurred during 1929 was published in 1931.There were several reports during 1995 to 2009 that described detailed account of leptospirosis including various clinical syndromes. The possibility of pulmonary involvement in leptospirosis being a manifestation historically overlooked rather than newly emerged during the past two decades is examined in this review in the context of Andaman Islands. Two case series of leptospirosis, one occurred in 1929 and the other in 1996-1997 were reviewed with special emphasis on pulmonary involvement and haemorrhagic manifestations. The similarities and differences in the clinical profile of patients of the two case series were analysed. The review shows that respiratory system involvement and pulmonary haemorrhage as evidenced by presence of haemoptysis as a complication of leptospirosis was occurring during 1920s in Andaman Islands. The incidence of pulmonary involvement, however, rose from 9.4 per cent during 1929 to 52 per cent in 1996-1997. The case fatality ratio in patients with pulmonary involvement, which was 50 per cent during 1929 and 42.9 per cent during 1996-1997, was higher than that in cases without pulmonary involvement.Fever, conjunctival congestion, jaundice, vomiting, diarrhoea, hepatomagaly, haemoptysis, haematemesis and subconjunctival haemorrhage were common in both series. The case series in Andaman Islands in 1929 was probably the first report of pulmonary haemorrhage as a manifestation of leptospirosis. The increase in the incidence of pulmonary involvement in leptospirosis in the recent past is probably due to the increase in the density and diversity of its animal vectors,the broadening of the range of circulating serovars and the interactions between the vector and the agent. An increased virulence of Leptospira through gene acquisition and loss on an evolutionary time scale and the resulting change in the gene content, gene order and gene expression cannot be ruled out.