F. Renaud

Incidence of tick-borne relapsing fever in west Africa: longitudinal study

BACKGROUNDnThe ongoing drought in sub-Saharan countries has led to the colonisation of west African Savanna by Ornithodoros sonrai; this tick acts as a vector for Borrelia crocidurae, which causes tick-borne relapsing fever (TBRF). Our aim was to ascertain the incidence of TBRF in west Africa.nnnMETHODSnFrom 1990 to 2003, we monitored the incidence of TBRF in Dielmo, Senegal, by daily clinical surveillance and by blood testing of individuals with a fever. From 2002 to 2005, we investigated the presence of O sonrai in 30 villages in Senegal, Mauritania, and Mali, and measured by PCR the prevalence of B crocidurae.nnnFINDINGSnThe average incidence of TBRF over 14 years was 11 per 100 person-years (range from 4 in 1990 to 25 in 1997). All age-groups presented a high incidence of the disease. In addition to relapses, repeated infections in the same individuals were common, with some affected by up to six distinct infections during the study period. Epidemiological studies indicated that 26 of the 30 studied villages (87%) were colonised by the vector tick O sonrai and that the average B crocidurae infection rate of the vector was 31%.nnnINTERPRETATIONnThe incidence of TBRF at the community level is the highest described in Africa for any bacterial disease. The presence of the vector tick in most villages investigated and its high infection rate suggest that TBRF is a common cause of fever in most rural areas of Senegal, Mauritania, and Mali.

Manipulation of host behaviour by parasites: ecosystem engineering in the intertidal zone?

Understanding the influence of parasites on the community ecology of free–living organisms is an emerging theme in ecology. The cockle Austrovenus stutchburyi is an abundant mollusc inhabiting the sheltered shores of New Zealand. This species, which lives just few centimetres under the surface, plays a key role for many benthic invertebrate species, because in these habitats the cockle shell is the only available hard surface where invertebrates can establish. However, the behaviour of this cockle can be altered locally by a parasite, the trematode Curtuteria australis. Indeed, heavily infected cockles are unable to bury perfectly and typically lie entirely exposed at the surface of the mud. In this study, we investigated the ecological consequences of this behavioural alteration for two invertebrates species commonly associated with cockles, the anemone Anthopleura aureoradiata and the limpet Notoacmea helmsi. A field study first demonstrated that in both infected and non–infected populations of cockles, there was a negative relationship between the number of anemones and limpets found on cockles. In the laboratory, we showed that predation of limpets by anemones is possible when they share the same cockle shell. In a heavily infected population of cockles, limpets were significantly more frequent and more abundant on cockles manipulated by C. australis than on cockles with a normal behaviour. A colonization test conducted in natural conditions demonstrated that the predominance of limpets on manipulated cockles results from a direct habitat preference. Conversely, anemones were significantly less frequent and less abundant on manipulated cockles than on cockles manipulated by C. australis. A desiccation test revealed that, relative to limpets, they had a lower resistance to this physical stress. We discuss our results in relation to current ideas on ecosystem engineering by organisms.

A comparative analysis of parasite species richness of Iberian rodents

Data on parasites of rodents, collected over an 18-year period on the Iberian peninsula, were used to find the determinants of parasite species richness. A total of 77 species of helminth parasites (nematodes, cestodes and digeneans) was identified among 16 species of rodents. Parasites were classified into groups according to their specificity towards their host and their life-cycle. A working phylogeny of the rodents was proposed on the basis of molecular and paleontological data and for each host the following parameters were recorded: sample size, weight, geographical range, longevity, and life-style. Two comparative methods were used, the independent comparisons method of Pagel (1992) and the distance matrix method of Legendre, Lapointe & Casgrain (1995). The second method has the advantage of measuring the relative contribution of phylogeny. Both methods gave similar results. Overall parasite species richness correlated only with host sample size. Host body size does not correlate with any subset of parasite species richness. However, host phylogeny is a good predicator of specific parasites and the species richness of digeneans correlates with host geographical range. A phylogenetic reconstruction of host relations was performed using the parasites belonging to subgroups in which richness is correlated with host phylogeny. These parasite species were treated as Dollo characters, i.e. we made the assumption that the loss of a parasite species is irreversible. The consensus tree obtained reflects the major phylogenetic divisions of the host group. Finally, this study illustrates the relative importance of processes acting at different temporal and spatial scales (evolutionary time and actual geographical range of hosts) in determining the structure of helminth parasite fauna.

Parasites and ecosystem engineering : what roles could they play?

In recent years, there has been a growing interest in understanding the ecological importance of ecosystem engineers. In this paper we argue that parasites, through the phenotypic alterations they induce in their hosts, are likely to be involved in engineering processes for at least two reasons. First, when ecosystem engineers are themselves infected, phenotypic alterations induced by parasites can interfere with host traits involved in the engineering processes. Secondly, parasites themselves can be ecosystem engineers since the phenotypic alterations of hosts directly modify the habitat of all the species inhabiting free-living organisms. This new research area at the interface between ecology and parasitology should improve our understanding of the ecological consequences of phenotypic alterations induced by parasites in ecosystems.

Genetic Polymorphism of Aspergillus fumigatus in Clinical Samples from Patients with Invasive Aspergillosis: Investigation Using Multiple Typing Methods

ABSTRACT The genotypes of 52 strains of Aspergillus fumigatusisolated from 12 patients with invasive aspergillosis were investigated using three typing methods (random amplified polymorphic DNA, sequence-specific DNA polymorphism, and microsatellite polymorphism) combined with multilocus enzyme electrophoresis. Isolates were from patients hospitalized in three different geographic areas (Lyon, France; Grenoble, France; and Milan, Italy). In each case, the genetic polymorphism of several colonies (two to five) within the first respiratory clinical sample was studied. For the 52 isolates tested, random amplified polymorphic DNA identified 8 different genotypes, sequence-specific DNA polymorphism identified 9 different types, and microsatellite polymorphism identified 14 types. A combination of these results with multilocus enzyme electrophoresis study identified 25 different types within the sample studied. We identified 3 patients (of the 12 studied) who carried a single genotype; 6 patients were infected by two genotypes, 1 patient had four genotypes, while the last patient had five. A combination of typing methods provided better discrimination than the use of a single method. Typing methods revealed a population structure within each geographical site, suggesting that the epidemiology of A. fumigatus should be considered separately for each of these geographic areas. This study demonstrates the usefulness of combining several typing methods in reaching an understanding of the epidemiology of A. fumigatus and clarifies whether it is sufficient to type one isolate from each specimen to determine the strain involved in invasive aspergillosis.

The epidemiology and geographic distribution of relapsing fever borreliosis in West and North Africa, with a review of the Ornithodoros erraticus complex (Acari: Ixodida).

Background Relapsing fever is the most frequent bacterial disease in Africa. Four main vector / pathogen complexes are classically recognized, with the louse Pediculus humanus acting as vector for B. recurrentis and the soft ticks Ornithodoros sonrai, O. erraticus and O. moubata acting as vectors for Borrelia crocidurae, B. hispanica and B. duttonii, respectively. Our aim was to investigate the epidemiology of the disease in West, North and Central Africa. Methods And Findings From 2002 to 2012, we conducted field surveys in 17 African countries and in Spain. We investigated the occurrence of Ornithodoros ticks in rodent burrows in 282 study sites. We collected 1,629 small mammals that may act as reservoir for Borrelia infections. Using molecular methods we studied genetic diversity among Ornithodoros ticks and Borrelia infections in ticks and small mammals. Of 9,870 burrows investigated, 1,196 (12.1%) were inhabited by Ornithodoros ticks. In West Africa, the southern and eastern limits of the vectors and Borrelia infections in ticks and small mammals were 13°N and 01°E, respectively. Molecular studies revealed the occurrence of nine different Ornithodoros species, including five species new for science, with six of them harboring Borrelia infections. Only B. crocidurae was found in West Africa and three Borrelia species were identified in North Africa: B. crocidurae, B. hispanica, and B. merionesi. Conclusions Borrelia Spirochetes responsible for relapsing fever in humans are highly prevalent both in Ornithodoros ticks and small mammals in North and West Africa but Ornithodoros ticks seem absent south of 13°N and small mammals are not infected in these regions. The number of Ornithodoros species acting as vector of relapsing fever is much higher than previously known.

Typing of Saccharomyces cerevisiae Clinical Strains by Using Microsatellite Sequence Polymorphism

ABSTRACT It seems that S. cerevisiae, which was thought for about 30 years to be a nonpathogenic yeast, should now be considered an opportunistic pathogen. In this study, we estimated the discrimination ability of the microsatellite sequence amplification technique within a sample of clinical and reference S. cerevisiae strains and S. boulardii reference strains.

Genetic Structure of Candida glabrata Populations in AIDS and Non-AIDS Patients

ABSTRACT The genotypes of 63 strains (11 reference strains and 52 strains from hospitalized patients) of the haploid yeast Candida glabrata were determined from 33 putative gene enzymatic loci. This enabled the characterization of 26 different multilocus genotypes. Genetic differentiation was found between distant hospitals (located in Montpellier and Paris, France) but not for other parameters (anatomic origins or human immunodeficiency virus-positive [HIV+] and HIV− patients). Strong nonrandom association between loci could be seen. Such statistical linkages were confirmed upon comparing the patterns of 14 RAPD [random(ly) amplified polymorphic DNA] primers from 20 of these strains to results obtained from multilocus enzyme electrophoresis analysis. This finding suggests a mainly clonal mode of reproduction of C. glabrata. The consequences of the clonality displayed by C. glabrata populations on the epidemiology of this yeast are also discussed.

Trypanosoma cruzi discrete typing units (DTUs): Microsatellite loci and population genetics of DTUs TcV and TcI in Bolivia and Peru

Trypanosoma cruzi, the agent of Chagas disease, is usually subdivided into six discrete typing units (DTUs), TcI to TcVI, among which TcI and TcV are most common in human infections in Bolivia. Multilocus microsatellite typing (MLMT) was selected to further explore the structure of the natural populations belonging to these DTUs. The analysis showed that microsatellite clustering does not fully match the six DTUs, but it is relevant for the within DTUs analyses. Population genetics analysis was conducted on 11 relevant subsamples of stocks from Bolivia and Peru, belonging to TcI (6) and TcV (5), defined by four criterions: DTU, vector species, geographic origin, and date of isolation. Most TcV strains presented the same multilocus genotype over all subsamples with the puzzling characteristic that five loci were heterozygous and the other five homozygous. In TcI, four clusters were defined according to the vector species. Most of them appeared in agreement with clonal propagation (stocks isolated from Triatoma infestans and Triatoma sordida), while a few highly homozygous stocks (e.g. those isolated from Rhodnius stali) suggested that scarce sex events can occur. The poor role played by spatio-temporal factors in describing the observed genetic diversity suggested that ecology, in particular as regard to host played a significant role. These results highlight the extreme heterogeneity of T. cruzi and suggest that further population genetics surveys will need to target the most possible precise spatio-temporal and ecological scales.

Epidemiology of Tick-Borne Borreliosis in Morocco

Background The presence in Morocco of Argasid ticks of the Ornithodoros erraticus complex, the vector of tick-borne relapsing fever (TBRF) in North Africa, has been known since 1919, but the disease is rarely diagnosed and few epidemiological data are available. Methodology/Principal Findings Between 2006 and 2011, we investigated the presence of Ornithodoros ticks in rodent burrows in 34 sites distributed across Morocco. We also collected small mammals in 10 sites and we investigated TBRF in febrile patients in Kenitra district. The prevalence of Borrelia infections was assessed by nested PCR amplification in ticks and the brain tissue of small mammals, and by evaluation of thick blood films in patients. A high proportion of burrows were infested with ticks of the O. erraticus complex in all regions of Morocco, with a mean of 39.5% for the whole country. Borrelia infections were found in 39/382 (10.2%) of the ticks and 12/140 (8.6%) of the rodents and insectivores studied by PCR amplification, and 102 patients tested positive by thick blood film. Five small mammalian species were found infected: Dipodillus campestris, Meriones shawi, Gerbillus hoogstrali, Gerbillus occiduus and Atelerix algirus. Three Borrelia species were identified in ticks and/or rodents: B. hispanica, B. crocidurae and B. merionesi. Conclusions/Significance Tick populations belonging to O. erraticus complex are widely distributed in Morocco and a high proportion of ticks and small mammals are infected by Borrelia species. Although rarely diagnosed, TBRF may be a common cause of morbidity in all regions of Morocco.