In continental France, in 1997, the number of leptospirosis cases decreased of more than 20 % in comparison with last year (1). However, it remains important with 344 cases(Table 1). In the whole French community (continental France plus French overseas territories), 950 leptospirosis cases were detected in1997.
A leptospirosis case is epidemiologically defined as an antibody level >/ 1/100 against a pathogenic Leptospira antigen in Micro Agglutination Test (MAT). However, in highly prevalent areas such as New Caledonia or French Polynesia, residual antibodies from previous undiagnosed leptospirosis (2) may lead to over reporting and the definition is more strict (3). Isolation of a Leptospira pathogenic isolate is also, of course, a criterium (less than 10 % of cases).
Particular features which were reported in 1996 (high frequency in urban areas and of Icterohaemorrhagiae) are no more present in 1997. In France, in 1997, on the point of view of leptospirosis looks like the beginning of the decenny or before (4). No more than 35 % of cases are due to Icterohaemorrhagiae (43 % in 1996) but Grippotyphosa increased to the usual rate of 20 % (10 % in 1996)(Table 1). The general diversity, when considering serogroups, slightly increased (Cynopteri, Sejroe ...).
On the geographical point of view, in continental France(Table 7), the region Aquitaine as before 1996 is the first one in absolute number of cases as well as in /100 000 hab. rate. It is noticeable that the 4 deaths associated to leptospirosis reported this year (not all are known) were associated with a small river of the south-west of France : the Adour. Franche-Comte, Pays de Loire and Champagne-Ardennes come at the 2nd rank as usual when considering rates/100 000.
On the seasonal point of view(Table 1), again 1997 differs from 1996 (no clear maximum) and shows a peak in september as usual.
Concerning overseas French territories, the total number of recorded cases is 585, similar to the 1996 one (569). Within this total, the New Caledonia part (366) (Table 8)is the main one (299 in 1996). However, in this particular area, PCR (routinely used) accounts for 132 cases detected by PCR alone (184 in 1996) (5). An increased number of serologically cases (85) is due to the introduction of a new serovar : Hurtsbridge (6) among the battery of antigens used in MAT, is somewhat questioning. Indeed, if this antigen is specific, it detects cases which should have been undiagnosed. If not, its use should be reconsidered.
The number of cases in other overseas territories is rather lower than usual : La Reunion - Mayotte : 96 instead of 125 in 1996(Table 2), French West Indies and Guyane : 75 instead of 104 in 1996(Table 3, Table 4, Table 5).
The endemicity rate in Tahiti (30/100 000) (Table 6)is increased when compared to previous ones (1, 2, 4), due to the fact that usually the whole population of French Polynesia was used to calculate the rate. In fact, leptospirosis biological diagnosis and reporting only comes from Tahiti sensu stricto. In this 1997 report, only Tahiti population was considered.
In conclusion, leptospirosis in France in 1997 is typical of what is usually recorded, which is in contrast with the 1996 situation (1).
References :
1. Baranton G., Postic D. 1997. Contribution à la surveillance épidémiologique de la leptospirose en France en 1996. http://www.pasteur.fr/Bio/Leptospira/(textcnr1996.html)
2. Duval G., Michault A., Baranton G., Law-Koune J.D., Folio G., Bertil G., Guiserix J. (1992) Etude sero-épidemiologique de la leptospirose humaine à l'ile de la Réunion. Revue epidem. Sante Publ. 39, 135-141.
3. Merien F., Perolat P. (1996) Public Health Importance of human Leptospirosis in the South-Pacific: a five years study in New Caledonia. Am. J. Trop. Med. Hyg. 55(2) 174-178.
4. W.H.O. Leptospirosis in France from 1985 to 1988. Wkly. Epidem. Rec., 40; 6th October 1989.
5. Merien F., Baranton G. Perolat P.. Comparison of Polymerase Chain reaction with Microagglutination Test and Culture for diagnosis of Leptospirosis J. Inf Dis. 1995; 172:281-5.
6. Perolat,P., Chappel R.J., Adler B., Baranton G., Bulach D.M., Billinghurst M.L., Letocart M., Merien F., Serrano M.S.. Leptospira fainei sp. nov., isolated from pigs in Australia Int. J. System. Bacteriol. 1998; 48:851-8
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