CONTRIBUTION TO LEPTOSPIROSIS SURVEILLANCE IN FRANCE IN 2005


Introduction
In 2005, the CNR received 5850 serological and 109 bacteriological analyses. The total number of observed cases (including those detected by PCR only) is 555. Among them, 212 (including 8 bacteriological cases) in continental France  (Table 1) and 8 from foreign countries.  A clear decrease is therefore noticed in both continental France and overseas departments/territories as compared to the 10 previous years (mean in continental France 308).

In continental France the incidence rate in 2005 is particularly low : 0.35/100000 inhabitants (Table 2)

Overseas, by range of order the incidence is higher in Guadeloupe (25.3) (Table 3) then in New Caledonia (20.3) (Table 8), Martinique (14.2) (Table 4), Mayotte (13.1) (Table 7) La Reunion (11.3)  (Table 6) Guyane (5.9) (Table 5) and Tahiti (3.7) (Table 9).

Epidemiological trends and surveillance

Three distinct cases definitions are used according to the considered area. The aim is to not take into account the residual low titers in serology, the frequency of which is quite different from an area to another one.

*1) In New Caledonia, the incidence is so high (often > 100/100000: excepted from 2000) that, if considered, the prevalence of residual low titers would lead to overestimation of the disease. Confirmed cases are defined as bacteriologically or PCR confirmed ones and/or seroconverted patients (four fold increase in titer). Probable cases correspond to 2).

*2) In high endemicity area (usually < 50/100000) such as La Reunion French west Indies and French Polynesia, a so-called "clinical" cut off (1/400 or more in Micro Agglutination Test: MAT against any of the pathogenic antigens) is used in order to prevent overestimation due to residual titers.

*3) In low endemicity areas, a so-called "epidemiological" cut off of 1/100 is considered. Indeed the low residual titers prevalence is unsignificant and, in opposition, if used, the 1/400 cut off would lead to underestimation of many cases due to the chronologically non-optimal sampling. It would also be the case for early treated leptospiroses or those due to Grippotyphosa serogroups (often characterized by low titers). This definition is used in French Guyana Mayotte (presence of grippotyphosa) and continental France. In these conditions, the case definition is a compromise between (serological) prevalence and incidence rates.

The number of reported cases in 2005 is particularly low : 212 with PCRs (Table 1) and 191 without PCR (Table 2). Such a low number in continental France has not been reported since 1989 : 179 (there was no PCR at this period). Another feature in 2005 is the absence of a true « peak ». In contrast the summer recrudescence is marked by a « plateau » of about 30 cases monthly from August to October (Table 1).

In what concerns the geographical distribution (Table 2) , as in 2004 but more markedly (Incidence 0.35 instead of 0.39), the decrease is generalized. It is particularly visible in the western part of the country (Brittany, Basse and Haute Normandy) and even in Ile de France, Aquitaine, Limousin and mainly Poitou Charentes. In contrast in the Eastern part of France some regions obtain scores higher than in 2004 : Centre, Nord-Pas de Calais and (anecdotically) Corse (2 cases instead of one) and overall Champagne-Ardennes which exhibits a top incidence at 1.35 (Table 2).

At the reduced scale of departments,(Table 10) the same characteristics are found but more markedly. Ardennes obtain the top incidence : 4.8 then Hautes Pyrenees : 1.4, Charente, Indre et Loire, Manche and Dordogne : 1.2 and Calvados : 1.

Concerning DOM/TOM (overseas areas), when considering the diffrent case definitions, the endemicity of leptospirosis in 2005 was close the 2004 one with 2 exceptions : New Caledonia where it increased (20.3 instead of 6.1) (Table 8) and Tahiti where it decreased (3.7 instead of 6) (Table 9).



News

From December 11th 2005, a Ministry decree modifies the nomenclature of medical biology acts.

Concerning leptospirosis, this decree obligates to first screen any sera received for leptospirosis diagnosis by a technique of MacroAgglutination (Slide Test) called « TR » (for antigen Thermo-Resistant). Only positive or ambiguous sera may be later on tested by MAT.

The National Reference Center has not been consulted about this modification which lead to important changes :

-    Cases definitions have to be changed by addition of an initial sentence : « a serlogical case of leptospirosis (possible, probable or confirmed) is defined by a positive or ambiguous result by MacroAgglutination TR and…. ».

-     The performances of the « TR » as well as for any screening test for leptospirosis being low, the number of detected cases will decrease as compared to those detected by the previous procedure (MAT sysyematic)

-    The « TR » exhibits a systematic sensitivity bias concerning some serogroups : in continental France : mainly Grippotyphosa but also Panama, Australis…, in Guadeloupe : Ballum… which will lead to an under estimation of cases specifically due to these serogroups.

-    All previous data, reports, software developments (such as the alert software initiated by Y. Le Strat at the InVS)… could not be used for comparaison with new ones due to the case definition change.
Publications in 2005 concerning Leptospira (research and CNR)

Z. MAJED, E. BELLENGER, D. POSTIC, C. POURCEL, G. BARANTON, M. PICARDEAU (2005)
Identification of variable-number tandem-repeat loci in Leptospira interrogans sensu stricto.
J. Clin. Microbiol., 43, 2, 539-545.
PMID: 15695642

H. LOUVEL, I. SAINT GIRONS, M. PICARDEAU (2005)
Isolation and characterization of FecA- and FeoB-mediated iron acquisition systems of the spirochete Leptospira biflexa by random insertional mutagenesis.
J. Bacteriol., 187, 9, 3249-54.
PMID: 15838052

P. BOURHY, H. LOUVEL, I. SAINT GIRONS, M. PICARDEAU (2005)
Random insertional mutagenesis of Leptospira interrogans, the agent of leptospirosis, using a mariner transposon.
J. Bacteriol., 187, 9, 3255-3258.
PMID: 15838053

C. HERRMANN-STORCK, A. BRIOUDES, R. QUIRIN, J. DELOUMEAUX, I. LAMAURY, M. NICOLAS, D. POSTIC, JM. PEREZ (2005)
Retrospective review of leptospirosis in Guadeloupe, French West Indies 1994-2001.
West Indian Med. J., 54, 1, 42-46.
PMID: 15892389

P. BOURHY, L. FRANGEUL, E. COUVÉ, P. GLASER, I. SAINT GIRONS, M. PICARDEAU (2005)
Complete nucleotide sequence of the LE1 prophage from the spirochete Leptospira biflexa and characterization of its replication and partition functions.
J. Bacteriol., 187, 12, 3931-3940.
PMID: 15937155

F. MERIEN, D. PORTNOÏ, P. BOURHY, F. CHARAVAY, A. BERLIOZ-ARTHAUD, G. BARANTON (2005)
A rapid and quantitative method for the detection of Leptospira species in human leptospirosis.
FEMS Microbiol. Lett., 249, 1, 139-147.
PMID: 16006065

MA. NAHORI, E. FOURNIE-AMAZOUZ, NS. QUE-GEWIRTH, V. BALLOY, M CHIGNARD, CR. RAETZ, I. SAINT GIRONS, C. WERTS (2005)
Differential TLR recognition of leptospiral lipid A and lipopolysaccharide in murine and human cells.
J. Immunol., 175, 9, 6022-6031.
PMID: 16237097

G. BARANTON, D. POSTIC (2005)
La leptospirose. Actualité.
Biologie & Santé, 5, 1, 233-250.

G. BARANTON, D. POSTIC (2005)
La leptospirose en France de 2001 à 2003.
in Surveillance nationale des maladies infectieuses 2001-2003, 5th ed., Département des Maladies infectieuses, Institut de Veille Sanitaire.
Published online as: http://www.invs.sante.fr/publications/2005/snmi/leptospirose.html