Vertical nontransovarial transmission of Bartonella in fleas

Pathogens use diverse pathways to infect host populations by vertical and/or horizontal routes. Horizontal transmission of bacteria belonging to the Bartonella genus via haematophagous vectors is well known. Vertical transmission of Bartonella species was also suggested to occur but its routes remain to be unveiled. In a previous study, we showed the absence of transovarial transmission of Bartonella species OE 1‐1 in Xenopsylla ramesis fleas, and that fleas feeding on Bartonella‐positive jirds produced Bartonella‐positive gut voids. This current study aimed to investigate whether vertical nontransovarial transmission of Bartonella occurs in fleas. For this aim, the X. ramesis–Bartonella sp. OE 1‐1 model was used. Four groups of fleas including Bartonella‐positive and Bartonella‐negative female fleas and larval offspring had access to either Bartonella‐negative or Bartonella‐positive gut voids and faeces. Sixteen per cent of flea offspring that had access to Bartonella‐positive faeces and gut voids became Bartonella positive. Our findings demonstrate that Bartonella‐positive flea faeces and gut voids are proper infection sources for flea larvae and indicate that vertical nontransovarial transmission of bartonellae occurs in fleas. This information broadens our understanding of Bartonella transmission routes in flea vectors and enlightens pathways of bartonellae transmission and maintenance in flea populations in nature.     

Host discrimination by two desert fleas using an odour cue

We compared the responses of two fleas, Xenopsylla dipodilli and Parapulex chephrenis simultaneously exposed to the odours of their rodent hosts, Gerbillus dasyurus (specific host ofX. dipodilli ) and Acomys cahirinus (specific host of P. chephrenis). We hypothesized that fleas are able to discriminate between host species by using an odour cue and predicted that X. dipodilli andP. chephrenis would select an odour of an appropriate host species. Xenopsylla dipodilli choseG. dasyurus significantly more often than A. cahirinus, whereas P. chephrenis choseA. cahirinus significantly more often than G. dasyurus. The ability to select an appropriate host species did not differ significantly either between flea species or between individuals of different sex or age classes within flea species. No X. dipodilli, but 67 of 150 P. chephrenis, refused to choose a host. The latency to move in an experimental maze was significantly shorter for X. dipodilli than P. chephrenis. The flea species also differed in the time taken from the beginning of the movement to the choice of a host, withX. dipodilli being faster than P. chephrenis. Neither flea sex nor age affected this parameter in either species. Females of both flea species produced significantly more eggs when they fed on their specific host than when they fed on the other host species. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Sampling fleas: the reliability of host infestation data

The use of measures of host infestation as a reliable indicator of a flea population size to be used in interspecific comparisons was considered. The abundance of fleas collected from host bodies and collected from host burrows was compared among 55 flea species, controlling for the effect of flea phylogeny. The mean number of fleas on host bodies correlated positively with the mean number of fleas in host burrows/nests both when the entire data pool was analysed and for separate subsets of data on 'fur' fleas and 'nest' fleas. This was also true for a within-host (Microtus californicus) between-flea comparison. The results of this study demonstrate that, in general, the index of host body infestation by fleas can be used reliably as an indicator of the entire population size.     

Do Fleas Affect Energy Expenditure of Their Free-Living Hosts?

Background

Parasites can cause energetically costly behavioural and immunological responses which potentially can reduce host fitness. However, although most laboratory studies indicate that the metabolic rate of the host increases with parasite infestation, this has never been shown in free-living host populations. In fact, studies thus far have shown no effect of parasitism on field metabolic rate (FMR).

Methodology and Results

We tested the effect of parasites on the energy expenditure of a host by measuring FMR using doubly-labelled water in free-living Baluchistan gerbils (Gerbillus nanus) infested by naturally occurring fleas during winter, spring and summer. We showed for the first time that FMR of free-living G. nanus was significantly and positively correlated with parasite load in spring when parasite load was highest; this relationship approached significance in summer when parasite load was lowest but was insignificant in winter. Among seasons, winter FMRs were highest and summer FMRs were lowest in G. nanus.

Discussion

The lack of parasite effect on FMR in winter could be related to the fact that FMR rates were highest among seasons. In this season, thermoregulatory costs are high which may indicate that less energy could be allocated to defend against parasites or to compensate for other costly activities. The question about the cost of parasitism in nature is now one of the major themes in ecological physiology. Our study supports the hypothesis that parasites can elevate FMR of their hosts, at least under certain conditions. However, the effect is complex and factors such as season and parasite load are involved.     

Level of lactoferrin in serum and cerebrospinal fluid of patients with meningitis

Study showed 9-fold increase of concentration of lactoferrin (LF) in serum of patients with bacterial meningitis (BM) compared with normal concentration and 5-fold increase of LF concentration in patients with aseptic meningitis (AM). Level of LF in cerebrospinal fluid (CSF) of patients with BM and AM was 200-fold and 22-fold higher than in control group respectively. In 71% of patients with AM concentration of protein in CSF did not exceed minimal level observed in patients with BM. Level of LF in serum and CSF during treatment statistically significantly decreased. Concentration of LF (the latter is marker of neutrophilic granulocytes activation) can be used as a characteristic of acuteness and intensity of inflammatory process in central nervous system, whereas detection of LF in CSF--as additional criterion in differential diagnostics between bacterial and viral meningitis. Furthermore, repeated measurement of LF level can be useful for monitoring of disease course and assessment of effect of treatment.     

Clinical and immunological characteristics of rubella in western Siberia

Evaluations of immune system of 155 patients with rubella and 90 contacts with patients were examined. Detection of viral genetic material in blood, urine, and nasopharyngeal swabs has been performed using RT-PCR method. Clinical diagnosis has been confirmed by RT-PCR in 114 (73.5%) patients. Changes of laboratory tests for rubella without clinical signs of the infection were observed in 20% of contacts. Complex ELISA- and PCR-assisted examination of patients can help to determine the stage of disease and characteristics of immune response. For differential diagnostic of rubella and other infectious diseases with exanthema it is rational to perform complex examination of patients using immunologic and molecular biologic methods.     

Effects of maternal and grandmaternal flea infestation on offspring quality and quantity in a desert rodent: evidence for parasite-mediated transgenerational phenotypic plasticity

Parasites can cause a broad range of sublethal fitness effects across a wide variety of host taxa. However, a host’s efforts to compensate for possible parasite-induced fitness effects are less well-known. Parental effects may beneficially alter the offspring phenotype if parental environments sufficiently predict the offspring environment. Parasitism is a common stressor across generations; therefore, parental infestation could reliably predict the likelihood of infestation for offspring. However, little is known about relationships between parasitism and transgenerational phenotypic plasticity. Thus, we investigated how maternal and grandmaternal infestation with fleas (Xenopsylla ramesis) affected offspring quality and quantity in a desert rodent (Meriones crassus). We used a fully-crossed design with control and infested treatments to examine litter size, pup body mass at birth, and pup mass gain before weaning for combinations of maternal and grandmaternal infestation status. No effect of treatment on litter size or pup body mass at birth was found. However, maternal and grandmaternal infestation status significantly affected pre-weaning body mass gain, a proxy for the rate of maturation, in male pups. Pups gained significantly more weight before weaning if maternal and grandmaternal infestation statuses matched, regardless of the treatment. Thus, pups whose mothers and grandmothers experienced similar risks of parasitism, either both non-parasitized or both infested, would reach sexual maturity more quickly than those pups whose mothers’ infestation status did not match that of their grandmothers. These results support the contention that parents can receive external cues such as the risk of parasitism, that prompt them to alter offspring provisioning. Therefore, parasites could be a mediator of environmentally-induced maternal effects and could affect host reproductive fitness across multiple generations.     

Phylogenetic signal in module composition and species connectivity in compartmentalized host-parasite networks

Abstract Across different taxa, networks of mutualistic or antagonistic interactions show consistent architecture. Most networks are modular, with modules being distinct species subsets connected mainly with each other and having few connections to other modules. We investigate the phylogenetic relatedness of species within modules and whether a phylogenetic signal is detectable in the within- and among-module connectivity of species using 27 mammal-flea networks from the Palaearctic. In the 24 networks that were modular, closely related hosts co-occurred in the same module more often than expected by chance; in contrast, this was rarely the case for parasites. The within- and among-module connectivity of the same host or parasite species varied geographically. However, among-module but not within-module connectivity of host and parasites was somewhat phylogenetically constrained. These findings suggest that the establishment of host-parasite networks results from the interplay between phylogenetic influences acting mostly on hosts and local factors acting on parasites, to create an asymmetrically constrained pattern of geographic variation in modular structure. Modularity in host-parasite networks seems to result from the shared evolutionary history of hosts and by trait convergence among unrelated parasites. This suggests profound differences between hosts and parasites in the establishment and functioning of bipartite antagonistic networks.     

Effect of abscisic acid and cold acclimation on the cytoskeletal and phosphorylated proteins in different cultivars of Triticum aestivum L

In winter wheat, the tubulin and 60 kDa-phosphorylated proteins/actin ratio is considerably higher in the roots than in the leaves. Differences in the content of the main cytoskeletal proteins were also found in the leaves of the different cultivars. It is suggested that the lower amount of the tubulin and 60 kDa-phosphorylated proteins and higher content of actin determine the greater tubulin cytoskeletal stability in the leaves and their higher frost resistance, as compared with the roots. Also, it is possible that the higher content of the tubulin and 60 kDa-phosphorylated proteins defines the lower microtubule (MT) stability in the leaves of the low frost resistant cultivar than in the leaves of the more frost resistant ones. In the roots and leaves of the low frost resistant cultivar, the low stability of the numerous tubulin structures is apparently one reason for the abscisic acid (ABA)-induced reduction of the cytoskeletal and 60 kDa-phosphorylated proteins in the cells. The cold acclimation compensated the ABA effect in the roots of the very frost resistant cultivar in the most extent. This suggests the existence of the different pathways in the increased plant cell frost resistance through the action of ABA and low temperature.