SUMMARYThe potential risk of bacterial dissemination due to the presence of cockroaches (Blattella germanica, Blattellidae) in low-income flats was investigated. Cockroaches can carry a great variety of bacterial species; we identified 30 different species from 52 different flats. Klebsiella oxycytoca, K. pneumoniae and Enterobacter cloacae were the most frequently found. Pathogenic and potentially pathogenic bacteria represented 54 % of all the bacterial identifications. Bacteria were carried either on the cuticle or in the gut. Contamination through external contact is sufficient to insure bacterial diffusion. There was a very low level of overlap estimated by Pianka's index (a) between the bacterial flora of neighbouring blocks of flats, and (b) between bacterial flora of different flats in the same block.

Sanitation is an important problem in relation to the control of pests in urban environments. This investigation analysed the potential risk related to the presence of cockroaches and their capacity for disseminating bacteria in six different types of buildings: hospital nursing area and out-patient area, swimming-pool pool-side and toilet area, low-income flats and food-handling places. Fifty-six species of bacteria were identified from 157 samples, 14 of these have previously been reported as potentially pathogenic for man and vertebrates. Similarities were found between samples collected in (a) the hospital out-patient area and food-handling establishments and (b) the hospital nursing area and flats. Pool-sides possessed a poorer bacterial flora. There was a greater bacterial specific diversity in food-handling establishments, flats and swimming-bath toilet area. Enterobacter cloacae. Klebsiella pneumoniae and Klebsiella oxytoca were dominant species in flats and the hospital nursing area. Therefore, cockroaches can play a role in disseminating bacteria, which they can carry passively on their cuticle.

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Few studies have investigated the genetic structure of both host and parasite populations at a level of populations and at a level of individuals. We investigated the genetic structure of the urban cockroach Blattella germanica and its oxyuroid parasite Blatticola blattae. Random amplified polymorphic DNA (RAPD) markers were used to quantify genetic diversity between and within four populations (from two cities in France) of the host and its parasite. Diversity based on phenotypic frequencies was calculated for each RAPD marker using Shannon-Wiener's index. We used multivariate analyses to test the significance of genetic differentiation between host and parasite populations. Analysis of molecular variance was also used. Both methods gave similar results. Diversity between pairs of individuals was estimated by Nei & Li's index. Genetic diversity was higher within host or parasite populations (80% and 82%, respectively, of explained diversity) than between host or parasite populations (20% and 18%, respectively, explained diversity). The genetic distances between pairs of parasite populations (or individuals) were not correlated with the genetic distances between the corresponding pairs of host populations (or individuals).

WOS:000083273100011International audienceThe genetic structure of 31 populations of the German cockroach, Blattella germanica (L.), located in two French cities 900 km apart, was estimated by enzyme gel electrophoresis. A set of 41 loci was analysed. Eight loci (4 Est, 3 Lap and 1 Got) were polymorphic. Diversity was estimated at different geographical levels: the overall population, between cities and within a city. Hierarchical F-statistics indicated significant genetic differentiation between all populations and among populations within each city, but no differentiation between cities. F-ST values for populations within each city and for the overall sample were substantially dissimilar. In addition, a cluster analysis did not separate populations according to their geographical origin but according to the predominance of either of the two alternative Est-4 alleles. The results of this analysis point to the absence of genetic differentiation on a large geographical scale: no large-scale geographical distance effect was detected. However, we evidenced strong genetic substructuring on a local scale, within cities

L'objectif n'est pas de présenter ici les résultats de cette recherche qui a déjà donné lieu à plusieurs publications (Rivault, Mathieu, Cloarec, Blanc, 1993, 1994, 1995. Nous voulons, en les prenant certes pour appui, tenter plutôt un retour critique sur notre pratique de l'interdisciplinarité du point de vue de son efficacité et de ses retombées théoriques. Cette expé rience s'inscrit en effet dans le courant préconisant la recherche interdisciplinaire depuis plusieurs années (Legay, 1986 ; Jollivet dir., 1992). Trois de ses traits rendent -nous semble-t-il -exemplaire la mise à nu3 des problèmes posés par l'interdisciplinarité dans le champ de recherche en formation qu'est l'environne ment (Jollivet, Pavé, 1993), urbain en particulier.C'est d'abord le fait que, contrairement à ce qui est souvent prôné dans la plupart des programmes pluri disciplinaires depuis Plozevet4, celle ci est à caractère limité : seules deux disciplines ont été mobilisées, l'éthologie et la géographie. C'est sans doute l'une des raisons majeures qui expliquent l'impression de réussite pour l'ensemble des chercheurs qui y ont pris part.C'est ensuite qu'il s'agit d' une question délibéré ment finalisée autour d'un cas de figure type, un problème sanitaire qui se pose au niveau mondial (cf.Abstract: This paper is related to an interdisciplinary research (ecology and geography) centred on a very practical social question: how to improve the control of Blattella germanica (coakroaches) which are proliferating in dwellings, thus deteriorating the inhabitants' quality of life. Three mainpoints have been emphasized in this research. First, it has been pointed out that it is essential to sort out specific problems inherent to interdisciplinary praxis, together with the means to solve them. Second, the relationship between geography and animal ecology has been analysed in depth: third, interesting scientific and applied results have emerged from this joint research.

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