In 2000, 5746 serological analyses and 90 bacteriological ones (+ 13 water samples) have been performed in the Reference National Center for Leptospirosis (RNC).

534 leptospirosis cases have been recorded. This number, concerning both continental France and overseas French territories, is among the lowest ones recorded during the last years.

In continental France, the 268 cases in 2000 are close to the number of recorded cases in 1998 (269) and inferior to the one of 1999 (306).

In overseas France, the total, 266, is quite low. However, it reflects the difficulties encountered to perform the biological diagnosis rather than a true decreasing in the number of cases.

In continental France, the seasonal maximum has been reached in October and mainly in September (60). Franche-Comté is the area where the incidence rate is the higher in 2000 (1.46/100 000 inhabitants).

Overseas, as usual, the higher incidence rates has been recorded in New Caledonia (28.06), Tahiti (11.33), French West Indies (8.92) and La Reunion-Mayotte (7.44).

Case definition differs according to the considered area :

- In high incidence areas (incidence usually over 20/100 000), the "clinical" serological cut-off (1/400) allows to differentiate between past infection (< 1/400) and recent infection (> 1/400).

- In low endemicity rates, the considered serological cut-off is much lower : 1/100. The reason is that in these areas, the prevalence of residual titers is usually insignificant and in practice does not interfere with acute infection diagnosis.

Conversely, using 1/400 would lead to not consider acute leptospirosis cases whose sampling has not been done at the optimal serological period or which have been treated early.

However, in Mayotte, although high endemicity area, the 1/100 cut-off has been used to prevent underestimation of Grippotyphosa infection which often leads to low antibodies levels : 1/100 or 1/200.

The low number of cases in continental France (268) (Table 1) in 2000 is inferior to the 2001 one (306) and close to the 1998 one (269) (Table 1bis98).

The seasonal distribution also is close to the 1998 one : 180 cases in the seconf half of the year with a maximum (60 cases) in September (Table 1bis98).

Concerning the serogroup distribution, 1998 trends (Table 1bis98) are further increased : few Icterohaemorrhagiae cases (58) which represent only 22 % of the whole, which has not been seen during the 15 last years. Conversely, Grippotyphosa (53 cases) represents 20 % of the cases. The other serogroups also are more represented : Australis : 36, Pomona : 13, and mainly Sejroe : 19, and Canicola : 18 (Table 1). Cynopteri too is prevalent (14 cases) but this may be due to overseas travelling.

At the regional scale, bias due to local Labs increasing their recruitment to a national (including overseas areas) level without giving any information on the patient origins, increased at Lille as well as (mainly) at Bordeaux. For instance, only 5 out of 19 cases from Bordeaux are documented. The 13 coming from a unique private Lab are not documented at all. A certain diversity in serogroups (5 serogroups for 13 patients) could suggest extra regioinal origin for those patients. A similar situation is noticed in Lille : 6 out of 16 patients are documented. In Lyon, the Merieux Lab, although not recording epidemiological data, transmits at least the patient origin, which prevents bias in geographical tables.

It is noticeable that in 2000 the number of cases in Ile-de-France (Table 7 is quite low (24 instead of 45 in 1998 and 42 in 1999). The decreasing in Icterohaemorrhagiae cases could be responsible for this point.

Conversely, Franche-Comté is this year the French region (on the continent) where leptospirosis endemicity is maximal (Table 7). Curiously, Icterohaemorrhagiae, which is usually largely prevalent in Franche-Comté, is almost absent in 2000 (2 out of 17 cases).

Overseas, as in 1999 the main variations in numbers are due to variations in the diagnosis potential rather than true epidemiological variations.

1) In Tahiti (Table 6, as in 1999 no MAT diagnoses have been locally performed. Therefore, all the Tahitian cases have been done in Paris (RNC).

In addition, Institute Malardé only asks for ELISA and not MAT on which is based the case definition. This explained the reduced number of cases in both 2000 (Table 6 and 1999 (Table 6 99 as compared to previous hears (Table 6 98.

2) In La Reunion, problems in the supplying of culture medium ingredients led to the loss of the reference strains used in MAT and here again most of the diagnoses have been done in PARIS (RNC). However, the number of cases (35 by serology and 6 by PCR = 41), although reduced as compared to previous years, remains noticeable (Table 2).

In Mayotte (Table 5), cases are reduced as compared to the 37 cases in 1998 (Table 5 98) but close to the 21 cases of 1999 (Table 5 99).

A particular feature in Mayotte is the relatively low number of cases due to Icterohaemorrhagiae : none in 2000, one in 1999 and 4 in 1998.

3) In the French West Indies, 43 cases in Martinique (Table 3), 37 in Guadeloupe (Table 4) and 6 in French Guyana are similar to those of previous years and comparable to one another. When taking into account the respective populations, incidence rate is : Martinique : 11.22/100000, Guadeloupe : 8.70/100000, Guyana : 3.82/100000.

4) In New Caledonia (Table 8), both serological cases and (mainly) PCR-based cases decreased in 2000. The reduction in PCR-based cases is in part due to a restricted use of this technique (PCR diagnosis has been supported by a territorial budget which decreased in 2000).

. In 1998, 161 PCR positive out of 1542 tests

. In 1999, 180 PCR positive out of 1647 tests

. In 2000, 65 PCR positive out of 418 tests

The mean age of patients (New Caledonia excluded) is 46 in continental France (52 in females and 44 in males) and 41 overseas (45 in females and 40 in males). Male predominance is similar in continental France and overseas : 80 %.

Documented cases represent 45 % of the patients.

In continental France, out of the 133 documented patients, 58 were considered as "inactive" (retired, workless + 2 homeless), 16 were students or pupils, 22 were involved in agriculture and breeding practices, 4 forest workers, 1 veterinarian, 2 in pisciculture, 6 in building, 2 employees in alimentary stores, 4 militaries, 1 gardener, 1 in rubbish dump.

Overseas, the 48 documented cases (New Caledonia excluded), show 12 retired people, 6 schoolboys, 9 patients involved in agricultural or breeding activities, 4 gardeners, 5 militaries, 3 bulding workers, 1 in pisciculture, 1 rat killing, 1 street sweeper.

Concerning risk activities, on the whole contacts with surface fresh waters in 80 %, with animals : 81 % (by order : rats : 61 cases, dogs : 56, rodents : 40). Canoe kayak was enjoyed by 6 patients, rafting/canyonning by 2 and jetski by one. Reports mention that 2 patients were victims of flooding, 4 of accidental falling in water, rat or dog (1) bites. One patient, infected by Sejroe, was validly vaccinated (serogroup Icterohaemorrhagiae).

. Noticeable in 2000 : 9 militaries have been infected in outbreak context :

- The first outbreak was a mundial one since 158 out of 304 participants to a raid (Ecochallenge 2000) in Malaysia (Sabah area from Borneo Island), which happened between August 20 and September 3, have been suffering from leptospirosis. France was represented by a single team : 4 militaries (3 males, 1 female) who all had serologically confirmed leptospirosis.

- The second outbreak took place in a strictly military context : 5 participants in a commando training in the bush (South of Martinique). All five contracted leptospirosis from Tarassovi serogroup.

As regards symptomatology, 240 patients were documented : symptoms frequency was as usual : fever : 87 %, algic syndrom : 61 %, renal signs : 47 %, icterus : 45 %, thrombopenia : 42 %, ocular symptoms (either early or delayed ones) : 21 %, encephalitis : 11 %, pulmonary symptoms : 12 %.

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A clonal subpopulation of Leptospira interrogans sensu stricto is the major cause of leptospirosis outbreaks in Brazil.

J. Clin. Microbiol., 38, (1), 450-452.

POSTIC D., RIQUELME-SERTOUR N., MERIEN F., PEROLAT P., BARANTON G. (2000)

Interest of partial 16S rDNA gene sequences to resolve heterogeneities between Leptospira collections : application to L. meyeri.

Res. Microbiol., 151, (5), 333-341.

POSTIC D., MERIEN F., PEROLAT P., BARANTON G. (2000)

Diagnostic biologique : Leptospirose - Borréliose de Lyme.

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COLLARES-PEREIRA M., KORVER H., CAO THI B.V., SANTOS-REIS M., BELLENGER E., BARANTON G., TERPSTRA W.J. (2000)

Analysis of Leptospira isolates from mainland Portugal and the Azores islands.

FEMS Microbiol. Lett., 185, (2), 181-187.

POSTIC D., BARANTON G. (2000)

Borrelia.

PEROLAT P., BARANTON G.

Leptospira.

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MARTI RAS N., POSTIC D., AVE P., HUERRE M., BARANTON G. (2000)

Antigenic variation of Borrelia turicatae Vsp surface lipoproteins occurs in vitro and generates novel serotypes.

Res. Microbiol., 151, 5-12.

MERIEN F., TRUCCOLO J., BARANTON G., PEROLAT P. (2000)

Identification of a 36-kDa fibronectin-binding protein expressed by a virulent variant of Leptospira interrogans serovar icterohaemorrhagiae.

FEMS Microbiol. Lett., 185, (1), 17-22.