| 1. |
- Barber, I., et al.
(författare)
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Effects of experimental Schistocephalus solidus infections on growth, morphology and sexual development of female three-spined sticklebacks, Gasterosteus aculeatus
- 2003
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Ingår i: Parasitology. - 0031-1820 .- 1469-8161. ; 126, s. 359-367
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Tidskriftsartikel (refereegranskat)abstract
- The use of naturally infected hosts in studies attempting to identify parasite-induced changes in host biology is problematical because it does not eliminate the possibility that infection may be a consequence, rather than a cause, of host trait variation. In addition, uncontrolled concomitant infections may confound results. In this study we experimentally infected individual laboratory-bred female three-spined sticklebacks Gasterosteus aculeatus L. with the pseudophyllidean cestode Schistocephalus solidus [Muller], and compared the morphology and growth patterns of infected females with sham-exposed controls over a 16-week period. Fish were fed a ration of 8% body weight per day. Non-invasive image analysis techniques allowed the growth of individual plerocercoids to be tracked in vivo throughout the course of infection, and patterns of host and parasite growth were determined. Females that developed infections diverged morphometrically from unexposed control females and exposed-uninfected females at 6 weeks post-infection, with the width of the body at the pectoral fins giving the earliest indication of infection success. When including the plerocercoid, infected females gained weight more quickly than controls, but when plerocercoid weight was removed this trend was reversed. There was no effect of infection on the increase in fish length. Plerocercoids grew at different rates in individual hosts, and exhibited measurable sustained weight increases of up to 10% per day. Final estimates of plerocercoid weight from morphometric analysis prior to autopsy were accurate to within +/-17% of actual plerocercoid weight. At autopsy, infected female sticklebacks had significantly lower perivisceral fat reserves but had developed significantly larger ovaries than controls. The results are discussed in relation to previous studies examining natural infections, and the value of utilizing experimental infections to examine ecological aspects of host-parasite interactions is discussed.
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| 2. |
- Billker, Oliver, et al.
(författare)
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Determination of mosquito bloodmeal pH in situ by ion-selective microelectrode measurement : implications for the regulation of malarial gametogenesis
- 2000
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Ingår i: Parasitology. - : Cambridge University Press (CUP). - 0031-1820 .- 1469-8161. ; 120, s. 547-551
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Tidskriftsartikel (refereegranskat)abstract
- Malarial gametocytes circulate in the peripheral blood of the vertebrate host as developmentally arrested intra-erythrocytic cells, which only resume development into gametes when ingested into the bloodmeal of the female mosquito vector. The ensuing development encompasses sexual reproduction and mediates parasite transmission to the insect. In vitro the induction of gametogenesis requires a drop in temperature and either a pH increase from physiological blood pH (ca pH 7.4) to about pH 8.0, or the presence of a gametocyte-activating factor recently identified as xanthurenic acid (XA). However, it is unclear whether either the pH increase or XA act as natural triggers in the mosquito bloodmeal. We here use pH-sensitive microelectrodes to determine bloodmeal pH in intact mosquitoes. Measurements taken in the first 30 min after ingestion, when malarial gametogenesis is induced in vivo, revealed small pH increases from 7.40 (mouse blood) to 7.52 in Aedes aegypti and to 7.58 in Anophĕles stephensi. However, bloodmeal pH was clearly suboptimal if compared to values required to induce gametogenesis in vitro. Xanthurenic acid is shown to extend the pH-range of exflagellation in vitro in a dose-dependent manner to values that we have observed in the bloodmeal, suggesting that in vivo malarial gametogenesis could be further regulated by both these factors.
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| 3. |
- Billker, Oliver, et al.
(författare)
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The roles of temperature, pH and mosquito factors as triggers of male and female gametogenesis of Plasmodium berghei in vitro
- 1997
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Ingår i: Parasitology. - : Cambridge University Press. - 0031-1820 .- 1469-8161. ; 115, s. 1-7
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Tidskriftsartikel (refereegranskat)abstract
- Developmentally arrested malarial gametocytes undergo gamete formation in the mosquito midgut immediately after ingestion of the infected bloodmeal. In the rodent malaria parasite Plasmodium berghei male gametogenesis (exflagellation) can be induced in vitro by a temperature decrease (from 39 degrees C in the vertebrate host to 20 degrees C) and a concomitant pH increase (from 7.3 in mouse blood to 8.0). We report the presence of additional Gametocyte Activating Factor(s) (GAF) present in Anopheles stephensi tissue extracts, which induce both male and female gametogenesis at the otherwise nonpermissive pH of 7.3 in vitro but are unable to overcome the low temperature requirement. All constituent cellular events of microgametogeneis studied here are induced by the same triggers in vitro. A temperature decrease is also required for exflagellation in the mosquito midgut. The possible role of GAF as a second obligatory natural trigger of gametogenesis is discussed.
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| 4. |
- Björkman, Camilla, et al.
(författare)
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Cryptosporidium infections in suckler herd beef calves
- 2015
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Ingår i: Parasitology. - 0031-1820 .- 1469-8161. ; 142, s. 1108-1114
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Tidskriftsartikel (refereegranskat)abstract
- A study was carried out to investigate how common Cryptosporidium infections are in beef calves in Swedish suckler herds and to explore which species and subtypes that occur. We further aimed at identifying factors associated with shedding of Cryptosporidium oocysts in this type of calf management. The study was conducted in two regions in Sweden and included 30 herds. Faecal samples were collected from calves younger than 3 months. A brief clinical examination was done and a questionnaire was used to collect data on management routines. Faeces were cleaned and concentrated and oocysts identified by epifuorescence microscopy. Cryptosporidium positive samples were analyzed at the 18S rRNA and GP60 genes to determine species and Cryptosporidium parvum subtype, respectively. Logistic regression was used to identify factors associated with infection. Oocysts were detected in 122 (36·7%) calves from 29 (97%) herds, at 400 to 2·4 × 107 OPG. The youngest positive calves were only 1 and 2 days old. There was no association between age and Cryptosporidium infection. Cryptosporidium bovis, C. ryanae, C. parvum and C. ubiquitum were identified, with C. bovis being the major species. Two C. parvum subtypes, IIaA16G1R1 and IIdA27G1 were identified. Routines for cleaning calf pens and number of cows in calving pens were associated with infection.
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| 5. |
- Björkman, Camilla
(författare)
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Endogenous and exogenous transplacental transmission of Neospora caninum - how the route of transmission impacts on epidemiology and control of disease
- 2009
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Ingår i: Parasitology. - 0031-1820 .- 1469-8161. ; 136, s. 1895-1900
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Forskningsöversikt (refereegranskat)abstract
- Vertical transmission of the protozoan parasite, Neospora caninum is highly efficient and can take two forms - endogenous transplacental transmission resulting from activation of the quiescent bradyzoite stage during pregnancy or exogenous transplacental transmission resulting from ingestion of oocysts during pregnancy. Calves born carrying infection derived from either endogenous or exogenous transplacental transmission are capable of infecting their offspring when they start to breed. This review considers firstly the frequency with which exogenous and endogenous transmission occur, secondly the role of the immune response in controlling N. caninum infection and thirdly how the parasite persists in an immune-competent host and is re-activated during pregnancy.
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| 6. |
- Dubiec, Anna, et al.
(författare)
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Differential prevalence and diversity of haemosporidian parasites in two sympatric closely related nonmigratory passerines
- 2016
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Ingår i: Parasitology. - 0031-1820 .- 1469-8161. ; 143:10, s. 1320-1329
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Tidskriftsartikel (refereegranskat)abstract
- Haemosporidian parasites infecting birds show distinct heterogeneity in their distribution among host species. However, despite numerous studies on the prevalence and diversity of parasite communities across species, very little is known on patterns of differences between them. Such data is lacking because up to date the majority of studies explored the patterns of variation in infections in different years, different time of sampling within a year or a breeding cycle, different study sites or was based on a small sample size, all of which may affect the estimates of prevalence and parasite diversity. Here, the prevalence, richness and diversity of haemosporidian parasites from the genera Plasmodium and Haemoproteus were studied in two closely related non-migratory hole-nesting passerines: Great Tits and Blue Tits. Birds were sampled in sympatrically breeding populations during two seasons at the same stage of their breeding cycle - late nestling care. Great Tits were more prevalently infected with Plasmodium and Haemoproteus parasites (97.1 vs 71.2%), harboured a higher proportion of multiple infections (26.2 vs 3.2%) and had a more diverse parasite community (11 vs 5 parasite lineages) than Blue Tits. Observed differences between two host species are discussed with reference to their breeding densities and immunological and behavioural characteristics.
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| 7. |
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| 8. |
- Hellgren, Olof, et al.
(författare)
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De novo synthesis of thiamine (vitamin B1) is the ancestral state in Plasmodium parasites – evidence from avian haemosporidians
- 2017
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Ingår i: Parasitology. - : Cambridge University Press (CUP). - 0031-1820 .- 1469-8161. ; 145:8, s. 1084-1089
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Tidskriftsartikel (refereegranskat)abstract
- Parasites often have reduced genomes as their own genes become redundant when utilizing their host as a source of metabolites, thus losing their own de novo production of metabolites. Primate malaria parasites can synthesize vitamin B1 (thiamine) de novo but rodent malaria and other genome-sequenced apicomplexans cannot, as the three essential genes responsible for this pathway are absent in their genomes. The unique presence of functional thiamine synthesis genes in primate malaria parasites and their sequence similarities to bacterial orthologues, have led to speculations that this pathway was horizontally acquired from bacteria. Here we show that the genes essential for the de novo synthesis of thiamine are found also in avian Plasmodium species. Importantly, they are also present in species phylogenetically basal to all mammalian and avian Plasmodium parasites, i.e. Haemoproteus. Furthermore, we found that these genes are expressed during the blood stage of the avian malaria infection, indicating that this metabolic pathway is actively transcribed. We conclude that the ability to synthesize thiamine is widespread among haemosporidians, with a recent loss in the rodent malaria species.
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| 9. |
- Henriksson, J, et al.
(författare)
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Chromosomal size variation in Trypanosoma cruzi is mainly progressive andis evolutionarily informative
- 2002
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Ingår i: Parasitology. - 0031-1820 .- 1469-8161. ; 124:Pt3, s. 277-286
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Tidskriftsartikel (refereegranskat)abstract
- The evolutionary significance of chromosome size polymorphism was explored in a representative panel of 26 Trypanosoma cruzi stocks. We tested a progressive model (aCSDI) assuming that the larger the size difference between homologous chromosomes, the more divergent the parasites are. This was contrasted with a non-progressive model (Jaccard's distance), in which any chromosome size difference has the same weight. ACSDI-based dendrograms were very similar to those built-up from multilocus enzyme electrophoresis (MLEE) and random amplified polymorphic DNA (RAPD) data: structuring in 2 major lineages (T. cruzi I and T. cruz II) and 5 small subdivisions within T. cruzi II was identical, and branching was very similar. Furthermore, a significant correlation (P < 0.001) was observed between aCSDI and phenetic distances calculated from MLEE and RAPD data. In contrast, analysis of chromosome size polymorphism with Jaccard's distance generated dendrograms with relatively long branches, causing most branching points to cluster close together, which generates statistically uncertain branching points. Our results thus support a model of progressive chromosome size-variation and show that despite an extensive polymorphism, chromosomal sizes constitute valuable characters for evolutionary analyses. Furthermore, our data are consistent with the clonal evolution model previously proposed for T. cruzi.
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| 10. |
- Höglund, Johan
(författare)
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Distribution of large lungworms (Nematoda: Dictyocaulidae) in free-roaming populations of red deer Cervus elaphus (L.) with the description of Dictyocaulus skrjabini n. sp.
- 2023
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Ingår i: Parasitology. - 0031-1820 .- 1469-8161. ; 150, s. 956-966
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Tidskriftsartikel (refereegranskat)abstract
- Lungworms of the genus Dictyocaulus are causative agents of parasitic bronchitis in domestic and wild ungulates. This study investigates the distribution, morphology and genetic diversity of D. cervi and a new lungworm species, Dictyocaulus skrjabini n. sp. infecting red deer Cervus elaphus, fallow deer Dama dama and moose Alces alces in Poland and Sweden. The study was conducted on 167 red deer from Poland and on the DNA of lungworms derived from 7 fallow deer, 4 red deer and 2 moose collected in Sweden. The prevalence of D. cervi and D. skrjabini n. sp. in dissected red deer in Poland was 31.1% and 7.2%, respectively. Moreover, D. skrjabini n. sp. was confirmed molecularly in 7 isolates of fallow deer lungworms and 1 isolate of red deer lungworms from Sweden. Dictyocaulus skrjabini n. sp. was established based on combination of their distinct molecular and morphological features; these included the length of cephalic vesicle, buccal capsule (BC), buccal capsule wall (BCW), distance from anterior extremity to the nerve ring, the width of head, oesophagus, cephalic vesicle, BC and BCW, as well as the dimensions of reproductive organs of male and female. Additionally, molecular analyses revealed 0.9% nucleotide sequence divergence for 1,605 bp SSU rDNA, and 16.5-17.3% nucleotide sequence divergence for 642 bp mitochondrial cytB between D. skrjabini n. sp. and D. cervi, respectively, and 18.7-19% between D. skrjabini n. sp. and D. eckerti, which translates into 18.2-18.7% amino acid sequence divergence between D. skrjabini n. sp. and both lungworms.
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