Papers by Joelle Gouy de Bellocq
Host immunocompetence assessed by spleen size and response to phytohaemagglutinin (PHA) injection... more Host immunocompetence assessed by spleen size and response to phytohaemagglutinin (PHA) injection may give some indications on the control of parasite infection and on host mediation effect, through immunity, on parasite community structure. We investigated the helminth community and immunocompetence of the white-toothed shrew in a small area to test the relationship between immunocompetence and intensity of helminth infection. At the proximate level and if spleen mass and PHA response reflect the level of immunocompetence, we expected that individuals with a large spleen or a high PHA response should harbour a lower parasite load than individuals with relatively small spleen or low PHA response. In addition, we predicted that the structure of the helminth community should be mediated by the host's immune defence. Spleen mass was linked to helminth infection. Nematodes and cestodes were negatively associated within hosts. PHA response was not related to total helminth intensity of infection but was negatively related to cestode intensity and positively to nematode intensity. This result suggests either a differential modulating effect on immunity by the two groups of worms or the existence of an antagonistic association between nematodes and cestodes mediated by the immune response of the host.
Journal of Evolutionary Biology
Parasite-mediated selection on major histocompatibility complex (MHC) genes has mainly been explo... more Parasite-mediated selection on major histocompatibility complex (MHC) genes has mainly been explored at the intraspecific level, although many molecular studies have revealed trans-species polymorphism. Interspecific patterns of MHC diversity might reveal factors responsible for the long-term evolution of MHC polymorphism. We hypothesize that host taxa harbouring high parasite diversity should exhibit high levels of MHC genetic diversity. We test this assumption using data on rodent species and their helminth parasites compiled from the literature. Controlling for similarity due to common descent, we present evidence indicating that high helminth species richness in rodent species is associated with increased MHC class II polymorphism. Our results are consistent with the idea that parasites sharing a long-term coevolutionary history with their hosts are the agents of selection explaining MHC polymorphism.
Comparative Parasitology
We investigated the endo- and ectoparasitic fauna of 45 specimens of Rattus rattus and 44 specime... more We investigated the endo- and ectoparasitic fauna of 45 specimens of Rattus rattus and 44 specimens of Mus musculus collected in Sicily. This study is the second survey of the parasitic fauna of these 2 rodent species on this Mediterranean island. Four nematode species, 1 cestode species, 2 flea species, and 1 tick species were recovered from R. rattus. Six nematode species, 3 cestode species, 1 digenean species, 1 flea species, and 1 tick species were recovered from M. musculus. As noted on other western Mediterranean islands, both rodent species show a depauperate parasite species richness in comparison with continental situations.
Acta Parasitologica, 2013
Heterakis is a genus of parasitic nematodes, the majority of which are found in ground-feeding bi... more Heterakis is a genus of parasitic nematodes, the majority of which are found in ground-feeding birds and only rarely in mammals. The best-known species is Heterakis spumosa, a parasite associated with the cosmopolitan invasive rodent Rattus rattus of Asiatic origin. Heterakis dahomensis was described in 1911 as a parasite of the Gambian giant rat (Cricetomys gambianus) from Benin (Africa), subsequently synonymized to H. spumosa by . The study of helminths in African rodents is scarce and patchy. Since the original description of H. dahomensis, there have been only a few reports from Africa of species belonging to the genus Heterakis and the validity of this species has never in fact been confirmed or rejected. In the present study individual Heterakis spp. were collected from C. gambianus from Senegal. The morphological data taken point to differences between Heterakis dahomensis and H. spumosa, specifically in the number of tail papillae in males and in the vulva cuticular processes of females. In addition, molecular data revealed differences between these taxa and so H. dahomensis should be considered as a valid species. Moreover, recent changes in the systematics of the genus Cricetomys mean that it is now necessary to study the morphology and genetics of the Heterakis specimens collected from Cricetomys spp. (previously assigned to C. gambianus) in order to determine their taxonomic status as either H. dahomensis o H. spumosa.
Emerging Infectious Diseases, 2010
To determine the specifi city of Morogoro virus for its reservoir host, we studied its host range... more To determine the specifi city of Morogoro virus for its reservoir host, we studied its host range and genetic diversity in Tanzania. We found that 2 rodent species other than Mastomys natalensis mice carry arenaviruses. Analysis of 340 nt of the viral RNA polymerase gene showed sympatric occurrence of 3 distinct arenaviruses.
Virology, 2015
Despite its near pan-African range, the Natal multimammate mouse, Mastomys natalensis, carries th... more Despite its near pan-African range, the Natal multimammate mouse, Mastomys natalensis, carries the human pathogen Lassa virus only in West Africa, while the seemingly non-pathogenic arenaviruses Mopeia, Morogoro, and Luna have been detected in this semi-commensal rodent in Mozambique/ Zimbabwe, Tanzania and Zambia, respectively. Here, we describe a novel arenavirus in M. natalensis from Gairo district of central Tanzania, for which we propose the name "Gairo virus". Surprisingly, the virus is not closely related with Morogoro virus that infects M. natalensis only 90 km south of Gairo, but clusters phylogenetically with Mobala-like viruses that infect non-M. natalensis host species in Central African Republic and Ethiopia. Despite the evolutionary distance, Gairo virus shares basic ecological features with the other M. natalensis-borne viruses Lassa and Morogoro. Our data show that M. natalensis, carrying distantly related viruses even in the same geographical area, is a potent reservoir host for a variety of arenaviruses.
Vector-Borne and Zoonotic Diseases, 2011
The East African Mopeia virus (MOPV) is an arenavirus closely related to the highly pathogenic We... more The East African Mopeia virus (MOPV) is an arenavirus closely related to the highly pathogenic West African Lassa virus, even sharing the same reservoir rodent host Mastomys natalensis. Because MOPV is not known to cause human disease, it offers a unique alternative for studying Lassa virus transmission. We investigated how habitat, population density, and host characteristics are related to MOPV occurrence in M. natalensis populations in Morogoro, Tanzania. In 3 contrasting habitats, 511 M. natalensis individuals were trapped, 12.1% (58/480 tested individuals) of which tested seropositive for antibodies and 8.4% (41/489 tested individuals) for MOPV-RNA. Although population densities differ among habitats, density and habitat were not significantly correlated to MOPV-RNA or antibody presence. Antibody presence was not significantly correlated with any host characteristics. In contrast, MOPV-RNA presence was inversely related to weight, age, sexual maturity, and body mass index. The model with body mass index as predictor was the best at predicting infection probability. Thirty-five individuals were exclusively MOPV-RNA positive, 52 were exclusively antibody positive, and 6 were both MOPV-RNA and antibody positive. Interpreting these data using experimental infection results from studies on other arenaviruses, this would mean that these infections were very recent, old, and roughly 1-3 weeks after infection, respectively. The higher RNA prevalence in juveniles implies vertical transmission, or that horizontal transmission occurs mainly in this age group due to lack of immunity, higher susceptibility, and/or higher juvenile contact rates. This study demonstrates the strength of combining information on antibody and RNA presence with host characteristics, and how this information can provide valuable insights into transmission dynamics.
The design and performance of a high-resolution momentum-imaging spectrometer for ions which is o... more The design and performance of a high-resolution momentum-imaging spectrometer for ions which is optimized for experiments using synchrotron radiation is presented. High collection efficiency is achieved by a focusing electrostatic lens; a long drift tube improves mass resolution and a positionsensitive detector enables measurement of the transverse momentum of ions. The optimisation of the lens for particle momentum measurement at the highest resolution is described. We discuss the overall performance of the spectrometer and present examples demonstrating the momentum resolution for both kinetics and for angular measurements in molecular fragmentation for carbon monoxide and fullerenes. Examples are presented that confirm that complete space-time focussing is possible for a two-field three-dimensional imaging spectrometer. © 2013 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.
The mammalian major histocompatibility complex (MHC) is a tightly linked cluster of immune genes,... more The mammalian major histocompatibility complex (MHC) is a tightly linked cluster of immune genes, and is often thought of as inherited as a unit. This has led to the hope that studying a single MHC gene will reveal patterns of evolution representative of the MHC as a whole. In this study we analyse a 1000km transect of MHC variation traversing the European house mouse hybrid zone to compare signals of selection and patterns of diversification at two closely linked MHC class II genes, H-2Aa and H-2Eb. We show that although they are 0.01 cM apart (that is, recombination is expected only once in 10 000 meioses), disparate evolutionary patterns were detected. H-2Aa shows higher allelic polymorphism, faster allelic turnover due to higher mutation rates, stronger positive selection at antigen-binding sites and higher population structuring than H-2Eb. H-2Eb alleles are maintained in the gene pool for longer, including over separation of the subspecies, some H-2Eb alleles are positively and others negatively selected and some of the alleles are not expressed. We conclude that studies on MHC genes in wild-living vertebrates can give substantially different results depending on the MHC gene examined and that the level of polymorphism in a related species is a poor criterion for gene choice.
Emerging Infectious Diseases, 2012
We investigated synanthropic small mammals in the Ethiopian Highlands as potential reservoirs for... more We investigated synanthropic small mammals in the Ethiopian Highlands as potential reservoirs for human pathogens and found that 2 rodent species, the Ethiopian white-footed mouse and Awash multimammate mouse, are carriers of novel Mobala virus strains. The white-footed mouse also carries a novel hantavirus, the second Murinaeassociated hantavirus found in Africa.
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Papers by Joelle Gouy de Bellocq