Infection Kinetics and Tropism of Borrelia burgdorferi sensu lato in Mouse After Natural (via Ticks) or Artificial (Needle) Infection Depends on the Bacterial Strain

Borrelia burgdorferi sl is a complex of pathogen bacteria transmitted to the host by Ixodes ticks. European Ixodes ricinus ticks transmit different B. burgdorferi species, pathogenic to human. Bacteria are principally present in unfed tick midgut, then migrate to salivary glands during blood meal and infect a new host via saliva. In this study, efficiency of transmission in a mouse model of three pathogen species belonging to the B. burgdorferi sl complex, B. burgdorferi sensu stricto (B31, N40, and BRE-13), B. afzelii (IBS-5), and B. bavariensis (PBi) is examined in order to evaluate infection risk after tick bite. We compared the dissemination of the Borrelia species in mice after tick bite and needle injection. Location in the ticks and transmission to mice were also determined for the three species by following infection kinetics. After inoculation, we found a significant prevalence in the brain for PBi and BRE-13, in the heart, for PBi, in the skin where B31 was more prevalent than PBi and in the ankle where both B31 and N40 were more present than PBi. After tick bite, statistical analyses showed that BRE-13 was more prevalent than N40 in the brain, in the bladder and in the inguinal lymph node. When Borrelia dissemination was compared after inoculation and tick bite, we observed heart infection only after tick inoculation of BRE-13, and PBi was only detected after tick bite in the skin. For N40, a higher number of positive organs was found after inoculation compared to tick bite. All European B. burgdorferi sl strains studied were detected in female salivary glands before blood meal and infected mice within 24 h of tick bite. Moreover, Borrelia-infected nymphs were able to infect mice as early as 12 h of tick attachment. Our study shows the need to remove ticks as early as possible after attachment. Moreover, Borrelia tropism varied according to the strain as well as between ticks bite and needle inoculation, confirming the association between some strains and clinical manifestation of Lyme borreliosis, as well as the role played by tick saliva in the efficiency of Borrelia infection and dissemination in vertebrates

Interrupted Blood Feeding in Ticks: Causes and Consequences

Ticks are obligate hematophagous arthropods and act as vectors for a great variety of pathogens, including viruses, bacteria, protozoa, and helminths. Some tick-borne viruses, such as Powassan virus and tick-borne encephalitis virus, are transmissible within 15–60 min after tick attachment. However, a minimum of 3–24 h of tick attachment is necessary to effectively transmit bacterial agents such as Ehrlichia spp., Anaplasma spp., and Rickettsia spp. to a new host. Longer transmission periods were reported for Borrelia spp. and protozoans such as Babesia spp., which require a minimum duration of 24–48 h of tick attachment for maturation and migration of the pathogen. Laboratory observations indicate that the probability of transmission of tick-borne pathogens increases with the duration an infected tick is allowed to remain attached to the host. However, the transmission time may be shortened when partially fed infected ticks detach from their initial host and reattach to a new host, on which they complete their engorgement. For example, early transmission of tick-borne pathogens (e.g., Rickettsia rickettsii, Borrelia burgdorferi, and Brucella canis) and a significantly shorter transmission time were demonstrated in laboratory experiments by interrupted blood feeding. The relevance of such situations under field conditions remains poorly documented. In this review, we explore parameters of, and causes leading to, spontaneous interrupted feeding in nature, as well as the effects of this behavior on the minimum time required for transmission of tick-borne pathogens

Differential Protein Modulation in Midguts of Aedes aegypti Infected with Chikungunya and Dengue 2 Viruses

International audienceAbstract Background: Arthropod borne virus infections cause several emerging and resurgent infectious diseases. Among the diseases caused by arboviruses, dengue and chikungunya are responsible for a high rate of severe human diseases worldwide. The midgut of mosquitoes is the first barrier for pathogen transmission and is a target organ where arboviruses must replicate prior to infecting other organs. A proteomic approach was undertaken to characterize the key virus/vector interactions and host protein modifications that happen in the midgut for viral transmission to eventually take place. Methodology and Principal Findings: Using a proteomics differential approach with two-Dimensional Differential in-Gel Electrophoresis (2D-DIGE), we defined the protein modulations in the midgut of Aedes aegypti that were triggered seven days after an oral infection (7 DPI) with dengue 2 (DENV-2) and chikungunya (CHIKV) viruses. Gel profile comparisons showed that the level of 18 proteins was modulated by DENV-2 only and 12 proteins were modulated by CHIKV only. Twenty proteins were regulated by both viruses in either similar or different ways. Both viruses caused an increase of proteins involved in the generation of reactive oxygen species, energy production, and carbohydrate and lipid metabolism. Midgut infection by DENV-2 and CHIKV triggered an antioxidant response. CHIKV infection produced an increase of proteins involved in detoxification. Conclusion/Significance: Our study constitutes the first analysis of the protein response of Aedes aegypti's midgut infected with viruses belonging to different families. It shows that the differentially regulated proteins in response to viral infection include structural, redox, regulatory proteins, and enzymes for several metabolic pathways. Some of these proteins like antioxidant are probably involved in cell protection. On the other hand, we propose that the modulation of other proteins like transferrin, hsp60 and alpha glucosidase, may favour virus survival, replication and transmission, suggesting a subversion of the insect cell metabolism by the arboviruses

Case presentation and management of Lyme disease patients: a 9-year retrospective analysis in France

IntroductionLyme borreliosis (LB) is the most common vector disease in temperate countries of the northern hemisphere. It is caused by Borrelia burgdorferi sensu lato complex.MethodsTo study the case presentation of LB in France, we contacted about 700 physicians every year between 2003 and 2011. An anonymous questionnaire was established allowing the collection of 3,509 cases. The information collected was imported or directly entered into databases and allowed identifying variables that were validated in a multiple correspondence analysis (MCA).ResultsSixty percent of the cases were confirmed, 10% were probable, 13.5% doubtful, 10.2% asymptomatic seropositive and 6.3% were negative. The clinical manifestations reported were cutaneous (63%), neurological (26%), articular (7%), ocular (1.9%) and cardiac (1.3%). Almost all patients were treated. When focusing more particularly on confirmed cases, our studies confirm that children have a distinct clinical presentation from adults. There is a gender effect on clinical presentation, with females presenting more often with erythema migrans or acrodermatitis chronica atrophicans than males, while males present more often with neurological signs or arthritis than females.DiscussionThis is the first time that a comprehensive study of suspected Lyme borreliosis cases has been conducted over several years in France. Although we were not able to follow the clinical course of patients after treatment, these results suggest the interest of refining the questionnaire and of following up a cohort of patients over a sufficiently long period to obtain more information on their fate according to different parameters

Vectra 3D (dinotefuran, pyriproxyfen and permethrin) prevents acquisition of Borrelia burgdorferi sensu stricto by Ixodes ricinus and Ixodes scapularis ticks in an ex vivo feeding model

BACKROUND: We evaluated the efciency of an ex vivo feeding technique using a silicone membrane-based feeding chamber to (i) assess the anti-feeding and acaricidal efcacy of a spot-on combination of dinotefuran, pyriproxyfen and permethrin (DPP, Vectra® 3D) against adult Ixodes scapularis and Ixodes ricinus ticks, and to (ii) explore its efect on blocking the acquisition of Borrelia burgdorferi sensu stricto. METHODS: Eight purpose-bred dogs were randomly allocated to two equal-size groups based on body weight assessed on day 2. DPP was administered topically, as spot-on, to four dogs on day 0. Hair from the eight dogs was collected individually by brushing the whole body on days 2, 7, 14, 21, 28 and 35. On each day of hair collection, 0.05 g of sampled hair was applied on the membrane corresponding to each feeding unit (FU). Seventy-two FU were each seeded with 30 adults of I. scapularis (n=24 FU) or I. ricinus ticks (n=48 FU). Bovine blood spiked with B. burgdorferi sensu stricto (strain B31) was added into each unit and changed every 12 h for 4 days. Tick mortality was assessed 1 h after seeding. One additional hour of incubation was added for live/moribund specimens and reassessed for viability. All remaining live/moribund ticks were left in the feeders and tick engorgement status was recorded at 96 h after seeding, and the uptake of B. burgdorferi s.s. was examined in the collected ticks by applying quantitative real-time PCR. RESULTS: Exposure to DPP-treated hair was 100% efective in blocking B. burgdorferi s.s. acquisition. The anti-feeding efcacy remained stable (100%) against both Ixodes species throughout the study. The acaricidal efcacy of DPP evaluated at 1 and 2 h after exposure was 100% throughout the study for I. ricinus, except the 1-h assessment on day 28 (95.9%) and day 35 (95.3%). The 1-h assessment of acaricidal efcacy was 100% at all time points for I. scapularis. CONCLUSIONS: The ex vivo feeding system developed here demonstrated a protective efect of DPP against the acquisition of B. burgdorferi without exposing the animals to the vectors or to the pathogen.Ceva Santé Animalehttps://parasitesandvectors.biomedcentral.compm2022Veterinary Tropical Disease

Reappraisal of Vipera aspis Venom Neurotoxicity

BACKGROUND: The variation of venom composition with geography is an important aspect of intraspecific variability in the Vipera genus, although causes of this variability remain unclear. The diversity of snake venom is important both for our understanding of venomous snake evolution and for the preparation of relevant antivenoms to treat envenomations. A geographic intraspecific variation in snake venom composition was recently reported for Vipera aspis aspis venom in France. Since 1992, cases of human envenomation after Vipera aspis aspis bites in south-east France involving unexpected neurological signs were regularly reported. The presence of genes encoding PLA(2) neurotoxins in the Vaa snake genome led us to investigate any neurological symptom associated with snake bites in other regions of France and in neighboring countries. In parallel, we used several approaches to characterize the venom PLA(2) composition of the snakes captured in the same areas. [br/] METHODOLOGY/PRINCIPAL FINDINGS: We conducted an epidemiological survey of snake bites in various regions of France. In parallel, we carried out the analysis of the genes and the transcripts encoding venom PLA(2)s. We used SELDI technology to study the diversity of PLA(2) in various venom samples. Neurological signs (mainly cranial nerve disturbances) were reported after snake bites in three regions of France: Languedoc-Roussillon, Midi-Pyrénées and Provence-Alpes-Côte d'Azur. Genomes of Vipera aspis snakes from south-east France were shown to contain ammodytoxin isoforms never described in the genome of Vipera aspis from other French regions. Surprisingly, transcripts encoding venom neurotoxic PLA(2)s were found in snakes of Massif Central region. Accordingly, SELDI analysis of PLA(2) venom composition confirmed the existence of population of neurotoxic Vipera aspis snakes in the west part of the Massif Central mountains. [br/] CONCLUSIONS/SIGNIFICANCE: The association of epidemiological studies to genetic, biochemical and immunochemical analyses of snake venoms allowed a good evaluation of the potential neurotoxicity of snake bites. A correlation was found between the expression of neurological symptoms in humans and the intensity of the cross-reaction of venoms with anti-ammodytoxin antibodies, which is correlated with the level of neurotoxin (vaspin and/or ammodytoxin) expression in the venom. The origin of the two recently identified neurotoxic snake populations is discussed according to venom PLA(2) genome and transcriptome data

La dengue et autres infections à flavivirus

International audienceFlaviviruses are responsible for yellow fever, Zika fever and dengue, all of which are major human diseases found in tropical regions of the globe. They are zoonoses with a transmission cycle that involves primates as reservoirs and mosquitoes of the genus Aedes as vectors. The recent upsurge of urban epidemics of yellow fever, Zika fever and dengue has involved human-to-human transmission with mosquitoes as the vector. This paper is primarily concerned with dengue, which has become the pre-eminent arbovirosis in terms of public health.Les flavivirus sont responsables de la fièvre jaune, de la fièvre Zika et de la dengue qui sont des maladies humaines majeures retrouvées dans les régions tropicales ceinturant le globe. Ce sont d’abord des zoonoses dont le cycle de transmission fait intervenir des primates comme réservoirs et les moustiques du genre Aedes comme vecteurs. La récente recrudescence des épidémies urbaines de fièvre jaune, de fièvre Zika et de dengue implique une transmission homme-homme via le moustique vecteur. Cet article est consacré essentiellement à la dengue qui est devenue l’arbovirose prééminente en termes de santé publique

Phylogénie moléculaire et systématique du genre Vipera Laurenti, 1768 et des genres apparentés Macrovipera Reuss, 1927 et Daboia Gray, 1842 (SERPENTES, VIPERIDAE), génétique des populations de Vipera aspis aspis (Linné, 1758) et Vipera aspis zinnikeri Kramer, 1958 et commentaires sur l'évolution de la neurotoxicité chez Vipera aspis

Le groupe des Vipera s. l. comprend les nombreuses espèces du genre Vipera, mais aussi celles des genres apparentés Macrovipera et Daboia. La systématique de ce groupe basée sur les caractères morphologiques ainsi que sur les distances immunologiques est mal définie. Ces vipères présentent une morphologie relativement similaire, peu favorable à la détermination de synapomorphies. C'est l'apparition récente de la neurotoxicité du venin des V. aspis aspis du Sud-Est de la France qui nous a amené à étudier plus précisément le genre Vipera. Le venin de V. a. zinnikeri, localisée dans le Sud-Ouest de la France, présente une neurotoxicité déjà décrite depuis longtemps, mais la distance qui sépare les populations de ces deux taxons neurotoxiques ne favorise pas l'hypothèse de l'hybridation. Pour appréhender le problème, deux approches complémentaires ont été tentées pour étudier le polymorphisme génétique du groupe de V. aspis s. l. : (1) la phylogénie moléculaire de 43 taxons basée sur l'analyse de la variabilité nucléotidique de deux gènes mitochondriaux (Cyt b et ND2) et (2) la structure génétique des populations françaises de V. a. aspis et V. a. zinnikeri définie à partir de l'analyse de marqueurs neutres telles que les isoenzymes. Les résultats ont permis de (1) améliorer la systématique du groupe des Vipera s. l. définie par la tribu des Viperini, en dégageant quatre genres répartis en deux groupes (le groupe européen composé du genre Vipera, et le groupe oriental composé par Montivipera, Macrovipera et Daboia), trois clades à l'intérieur du genre Vipera (le complexe de V. ammodytes, le groupe de V. aspis et Pelias), et deux clades (italien et français) au sein des V. aspis, (2) caractériser les populations de V. a. aspis neurotoxiques du Sud-Est de la France qui forment un groupe émergeant très tôt de la lignée des V. a. aspis, (3) dégager les stratégies évolutives mises en place dans les différents taxons au cours de leur histoire, et (4) proposer une synthèse sur la répartition biogéographique des Viperini. Les perspectives à ce travail sont nombreuses et parmi elles, on peut citer : l'amélioration des relations phylogénétiques au sein des Viperini en réalisant davantage d'études moléculaires, morphologiques, écologiques, toxicologiques et des caryotypes de ce groupe. La poursuite et l'amélioration des études de génétique des populations et de phylogéographie devront être incitées pour mesurer l'impact des bouleversements de l'environnement sur l'organisation des populations de vipères.Vipera s. l. group includes numerous species belonging to the Vipera genus and to related genera Macrovipera and Daboia. Although neurotoxicity properties of the Vipera aspis zinnikeri venom is already known, it has never been described before 1992 for Vipera aspis aspis in the southeastern France. Two complementary approaches were conducted to study genetic polymorphism of Vipera s. l. and to better understand European vipers evolution: (1) molecular phylogeny inferred from mitochondrial DNA (Cyt b and ND2) for 43 taxa, and (2) genetic structure of French V. a. aspis and V. a. zinnikeri populations from allozymes analyses. Our results clarified the systematic of the Vipera s. l., defining the tribe of Viperini with four genera (Vipera, Montivipera, Macrovipera and Daboia). Three clades composed the Vipera genus with V. ammodytes complex, V. aspis group and Pelias, whereas the V. aspis complex was divided into two clades, an Italian and a French. The neurotoxic populations of V. a. aspis from southeastern France were clustered and branched out very early in the V. a. aspis history. We have discussed the patterns of evolution within Viperini and presented a synthesis of the biogeography of this group.PARIS-Museum Hist.Naturelle (751052304) / SudocSudocFranceF

European Aedes albopictus and Culex pipiens Are Competent Vectors for Japanese Encephalitis Virus.

International audienceJapanese encephalitis virus (JEV) is the causative agent of Japanese encephalitis, the leading cause of viral encephalitis in Asia. JEV transmission cycle involves mosquitoes and vertebrate hosts. The detection of JEV RNA in a pool of Culex pipiens caught in 2010 in Italy raised the concern of a putative emergence of the virus in Europe. We aimed to study the vector competence of European mosquito populations, such as Cx. pipiens and Aedes albopictus for JEV genotypes 3 and 5.After oral feeding on an infectious blood meal, mosquitoes were dissected at various times post-virus exposure. We found that the peak for JEV infection and transmission was between 11 and 13 days post-virus exposure. We observed a faster dissemination of both JEV genotypes in Ae. albopictus mosquitoes, when compared with Cx. pipiens mosquitoes. We also dissected salivary glands and collected saliva from infected mosquitoes and showed that Ae. albopictus mosquitoes transmitted JEV earlier than Cx. pipiens. The virus collected from Ae. albopictus and Cx. pipiens saliva was competent at causing pathogenesis in a mouse model for JEV infection. Using this model, we found that mosquito saliva or salivary glands did not enhance the severity of the disease.In this study, we demonstrated that European populations of Ae. albopictus and Cx. pipiens were efficient vectors for JEV transmission. Susceptible vertebrate species that develop high viremia are an obligatory part of the JEV transmission cycle. This study highlights the need to investigate the susceptibility of potential JEV reservoir hosts in Europe, notably amongst swine populations and local water birds

Infection of a French Population of Aedes albopictus and of Aedes aegypti (Paea Strain) with Zika Virus Reveals Low Transmission Rates to These Vectors’ Saliva

Disease caused by the Zika virus (ZIKV) is a public health emergency of international concern. Recent epidemics have emerged in different regions of the world and attest to the ability of the virus to spread wherever its vector, Aedes species mosquitoes, can be found. We have compared the transmission of ZIKV by Ae. aegypti (PAEA strain originating from Tahiti) and by a French population of Ae. albopictus to better assess their competence and the potential risk of the emergence of ZIKV in Europe. We assessed the transmission of ZIKV by Ae. albopictus in temperatures similar to those in Southern France during the summer. Our study shows that the extrinsic incubation period of Ae. aegypti for transmission was shorter than that of Ae. albopictus. Both vectors were able to transmit ZIKV from 10 to 14 days post-infection. Ae. aegypti, however, had a longer transmission period than the French population of Ae. albopictus. Although the salivary glands of both vectors are highly infected, transmission rates of ZIKV to saliva remain relatively low. These observations may suggest that the risk of emergence of ZIKV in Europe could be low