边缘革蜱的生物学观察

本文在室内(T15～28℃和RH66％～87％)及自然环境条件下,初步观察研究了边缘革蜱(Dermacentor marginatus)的生活史和某些生物学特征,并获得了有关参数。其生活史各期经历平均时间为:卵期22天,幼、若虫期分别为24和37天,成虫滞育越冬时间为233天,越冬后寻找宿主吸(饱)血时间为17天,饱血雌蜱孕卵期为15天,产卵期17天,总计一个世代发育周期大约为365天。每只雌蜱日平均产卵264.8粒,一生平均产卵4501粒;卵长宽径值为394.1×340.3μm,卵的孵化率为87.7％;幼、若虫期吸血率分别为69.5％和54.6％,由幼虫到若虫和由若虫到成虫其蜕变率分别为80.1％和94.6％;子代成虫雄雌比例为1∶1.3。以上基础数据,填补了国内对该蜱种生物学研究的某些空缺,对有关自然疫源性疾病的研究具有一定的参考价值。     

Ecology of Amblyomma neumanni (Acari: Ixodidae)

The life cycle of Amblyomma neumanni was described studying the seasonal distribution of free-living stages and parasitic phases during two consecutive years. Development periods of engorged ticks under different photoperiod conditions were recorded. Larvae of A. neumanni have the peak of abundance in autumn. Nymphs reach the peak in winter. Females were collected on cattle from autumn to late spring. The seasonal distribution pattern of females showed a bimodal curve, with a peak in autumn and other during early and middle spring. The engorged females exposed at shortest photoperiod regimen (10 h light-14 h dark) under both laboratory and field conditions undergo morphogenetic diapause, expressed as a delay in the oviposition. It is concluded that females of A. neumanni that feed and copulate in autumn undergo morphogenetic diapause, and they will lay eggs in spring, simultaneously with the females that feed and copulate in this season. Climate niche analysis shows that adequate suitability for A. neumanni depends mainly from temperature (mean, absolute maximum and minimum, and mean temperature in wettest and driest quarters) as well as from rainfall in warmest and coldest quarters. Sequences of 16S rDNA gene belonging to different populations of A. neumanni, showed no intraspecific genetic differentiation.     

Transmission Dynamics of Francisella tularensis Subspecies and Clades by Nymphal Dermacentor variabilis (Acari: Ixodidae)

In the United States, the American dog tick, Dermacentor variabilis (Say) is considered an important biological vector of Francisella tularensis, the etiologic agent of tularemia. In this study, we evaluated the vector efficiency of nymphal D. variabilis infected as larvae with differing clades and subspecies (A1b, A2, and type B) of F. tularensis. In all cases, D. variabilis larvae were able to acquire, maintain, and transstadially transmit F. tularensis. Significant replication of the bacteria also occurred in infected nymphs. Transmission of F. tularensis to Swiss Webster mice was not observed with A1b, and low rates were observed with A2 (8.0%) and type B (13.5%). Negative effects on tick survivorship were also observed for A1b, A2, and type B infections. Our results provide evidence of a high fitness cost and low transmission rates during the immature stages, suggesting that D. variabilis may play a limited role in enzootic maintenance of F. tularensis.     

Morphometric features of tarsus in Dermacentor reticulatus (Fabricius, 1794) (Acari: Ixodida: Ixodidae) larvae from Polish and Slovakian populations

Dermacentor reticulatus is widely distributed dangerous tick that usually lives in the river valleys, boggy forests, meadows, and wooded pastures. Tick populations from various regions may exhibit morphological differences. In our study we compared morphometric features of tarsus in larvae D. reticulatus from Polish and Slovakian populations. I tarsus width, III tarsus length, and length of dorsal setae of I tarsus were significantly higher in Polish populations. Indices of width to length of tarsus I and tarsus III were also significantly different in both populations. The other examined morphologic features were similar, what may result from the same environmental conditions of both populations.     

Biochemical differentiation between species of ticks (Acari: Ixodidae)

An electrophoretic analysis of nine species of ticks representing three genera of the family Ixodidae was performed. Within the genus Ambylomma, the species are completely distinguished using ACPH and PEP-1. The phenotype of A. americanum is ACPH1-00 and PEP-1(1-00) or PEP-1(0-92); A. maculatum has phenotype ACPH0-92 and no expression of PEP-1; A. cajennense has phenotype ACPH1-04 and PEP-1(0-98); while the phenotype of A. inoratum is ACPH1-02 and PEP0-98. Among the Dermacentor, peptidase phenotypes completely distinguish the species. The species D. albipictus has phenotypes PEP-1(0-94) or PEP-1(0-88) and PEP-2(0-98); D. andersoni has phenotype PEP-1(1-00) and PEP-2(1-00); D. variabilis has phenotype PEP-1(0-94) and no expression of PEP-2; and D. nitens has phenotypes PEP-1(1-06) or PEP-1(0-98) and no expression of PEP-2. The final species, R. sanguineus can be distinguished from all the other species by its having the unique allele ACPH0-98.     

Cleavage in Ixodes ricinus (L.) (Acari: Ixodidae)

The author analyzed the first 5 days of embryonic development of Ixodes ricinus. The cleavage takes 4 days, being terminated on the 5th day of embryogenesis, when the cells start to invaginate and differentiate. The karyomeres play a role in the initial mitotic divisions. Cellularization occurs on the 2nd and 3rd day of embryogenesis. The blastoderm cells maintain their potential for division, and as from the 5th day cellular differentiation starts.     

Tick-borne encephalitis virus as an amplifier of the metamorphosis of Ixodes ricinus (Acari: Ixodidae) tick nymphs under long-day photoperiodic conditions

The metamorphosis of tick-borne encephalitis virus (TBEV)-induced I. ricinus nymphs under long-day photoperiodic conditions (18 light hours and 6 darkness hours) occurs more rapidly than in uninfected specimens. The infected nymphs begin to develop to the imagoes 25-33 days earlier than do uninfected ones. The first imagoes from the infected nymphs emerge on day 24 after saturation whereas those from the uninfected nymphs appear on day 43. The interval from nymphal saturation to imago development in 50% specimens is 27.7 +/- 2.0 and 52.2 +/- 0.7 days, respectively. Reasons for geographical differences in the intensity of amplification of the metamorphosis of saturated I. nicinus nymphs are discussed in the paper.     

The ticks (Acari: Ixodida: Argasidae, Ixodidae) of Paraguay

The ticks reported in Paraguay, which are here reviewed, can be categorized as 'endemic or established' (Argas persicus or a sibling species, Ornithodoros hasei, O. rostratus, O. rudis, O. talaje/O. puertoricensis, Amblyomma aureolatum, Am. auricularium, Am. brasiliense, Am. cajennense, Am. calcaratum, Am. coelebs, Am. dissimile, Am. dubitatum, Am. incisum, Am. longirostre, Am. nodosum, Am. ovale, Am. pacae, Am. parvum, Am. pseudoconcolor, Am. rotundatum, Am. scutatum, Am. tigrinum, Am. triste, Dermacentor nitens, Haemaphysalis juxtakochi, H. leporispalustris, Ixodes loricatus, Rhipicephalus microplus, and Rh. sanguineus), 'probably endemic or established' (Ar. miniatus, Ar. monachus, Am. argentinae, Am. humerale, Am. naponense, Am. oblongoguttatum, Am. pseudoparvum, I. aragaoi/I. pararicinus, I. auritulus, I. luciae), or 'erroneously reported from Paraguay' (O. coriaceus, Am. americanum and Am. maculatum). Most Paraguayan tick collections have been made in the Chaco phyto-geographical domain, in the central part of the country. Argas persicus or a related species, Am. cajennense, D. nitens, Rh. microplus and Rh. sanguineus are important parasites of domestic animals. Ornithodoros rudis, Am. aureolatum, Am. brasiliense, Am. cajennense, Am. coelebs, Am. incisum, Am. ovale and Am. tigrinum have all been collected from humans. In terms of public health, the collections of Am. cajennense and Am. triste from humans may be particularly significant, as these species are potential vectors of Rickettsia rickettsii and Ri. parkeri, respectively.     

The activity of Dermacentor reticulatus Fabr. (Ixodidae) ticks in nature

The experimental population-based ecological parameters most closely associated with the age of ticks, including activity, were assessed in the D. reticulatus imago (Moscow Province). The activity rise of ticks in autumn is twice as low as that in spring, with their inactivity in summer. There are some seasonal variations in the ratio of males to females. Evidence has been first provided for the maximum duration (more than 2.5 years, about 1%) of active life till the third spring when the coloured imagoes are let free. Most new-generation individuals have been found to be inactive in autumn. There is a high repeated activity in ticks by seasons: as many as half of the spring individuals (48%) in autumn and more than a third (37%) in spring to come. The repeatedly active individuals whose age is less than a year are most among those in the autumn peak. The summer inactivity of hungry imagoes represents ticks' stable behavioral adaptation, by increasing their active life. This condition is regarded as a component of the "activation diapause" phenomenon.     

PCR-based survey of Anaplasma phagocytophilum in Portuguese ticks (Acari: Ixodidae)

A total of two-thousand and six ticks, collected from 2002 to 2006 in areas belonging to seven districts of Mainland Portugal and also in Madeira Island, were examined by polymerase chain reaction (PCR) for the presence of Anaplasma phagocytophilum. Active infections were detected exclusively in Ixodes species, including six questing I. ricinus nymphs from Madeira Island, one questing I. ventalloi nymph from Setúbal District, and two I. ventalloi adults found parasitizing domestic cats in both Setúbal and Santarém District. These findings confirm prior observations and suggest the persistence of A. phagocytophilum on Madeira Island. Moreover, it adds I. ventalloi and domestic cats to the list of potential elements of the agent's enzootic cycles in Portugal. Molecular analysis of PCR amplicons suggests the existence of two A. phagocytophilum genotypes in Portugal, one of which is identical or very similar to North American strains implicated in human disease.     

Borrelia afzelii gene expression in Ixodes ricinus (Acari: Ixodidae) ticks

Spirochetes belonging to the Borrelia burgdorferi sensu lato (s. l.) complex have evolved remarkable ability to survive in diverse ecological niches during transmission cycles between ticks and vertebrate hosts by variable gene expression. To understand the events during spirochete transmission from feeding ticks to hosts, mRNA levels of selected B. afzelii genes (bbk32, dbpA, ospA, ospC and vlsE) were measured by quantitative real-time SYBR Green PCR. B. afzelii infected Ixodes ricinus nymphs fed on laboratory BALB/c mice for 0, 24, 48, and 72 hours. The mRNA levels of the constantly expressed flagellin gene were used for the relative quantification of selected genes. Differences in gene expression profiles were observed in unfed ticks and during tick feeding. mRNA levels of bbk32 and dbpA showed distinctive decreasing patterns during the first 24 hours post-attachment, while ospC and vlsE mRNA levels increased significantly during the feeding process. In contrast, ospA levels decreased for the 48 hours of tick feeding and slightly increased by 72 hours. More detailed and comprehensive studies on regulation of gene expression in different Borellia genospecies on the vector-host interface would aid to develop effective strategies in preventing pathogen transmission.     

Biology of house dust mites (Acari: Astigmata: Pyroglyphidae)

This article is a first part of the rewiev of the house-dust-mite-atopy problem data. It includes informations on biology of these mites with emphasis of medical aspect and control. We hope that these informations will be of considerable interest to many readers because of the greatly increased investigations into the role of house dust mite sensitivity in allergic diseases.     

Life cycle of the nematode Contracaecum rudolphii Hartwig, 1964 (sensu lato) from northern Poland under laboratory conditions

Summary The study was aimed at following, under laboratory conditions, embryogenesis of the nematode Contracaecum rudolphii, and at identifying its intermediate hosts in northeastern Poland. Nematode eggs, isolated from the terminal part of the female uterus, were placed in 0.9 and 3% NaCl solutions, 1% formalin, and in tap water. Each solution batch was divided into 3 parts kept at 4, 15, and 23°C. Regardless of the temperature they were exposed to, the eggs placed in 1% formalin showed numerous deformations; as few as 5% of those eggs produced larvae. Embryogenesis was at its fastest in the eggs kept at 23°C. While still within the eggs, the larvae underwent two moults. The eggs hatched to produce the stage 3 larvae, which emerged surrounded by the cuticle of the preceding larval stage. Experimental infestations of zooplankton collected from Lake Kortowskie showed that only cyclopoid copepods could serve as the intermediate hosts. No differences in the infestation intensity were found between the guppies infested by the invasive larvae and those fed the infested cyclopoids.     

Phylogeography and demographic history of Amblyomma variegatum (Fabricius) (Acari: Ixodidae), the tropical bont tick

The genetic diversity of Amblyomma variegatum (Fabricius) from four Caribbean islands and five African countries was compared by analyzing the sequences of three gene fragments, two mitochondrial (12SrDNA and D-Loop-DL), and one nuclear (intergenic transcribed spacer 2 [ITS2]). Genetic variability of the ITS2 DNA fragment consisted of only uninformative single nucleotide mutations, and therefore this gene was excluded from further analyses. Mitochondrial gene divergences among African populations and between Caribbean and African populations were very low. Nevertheless, the data suggest that A. variegatum is divided into distinct East and West African groups, the western group including all Caribbean samples. Phylogenetic analyses of the 12SrDNA and DL gene sequences showed that the West African A. variegatum clustered in a well-supported monophyletic clade, distinct from eastern paraphyletic lineages. Sequences of A. variegatum from the Caribbean were embedded in the West African clade, which supports the known West African historical origin for these ticks.     

Investigation of the validity of species status of Ixodes dammini (Acari: Ixodidae) using rDNA.

The two internal transcribed spacers (ITS1 and ITS2) of rDNA of three members of the Ixodes ricinus "complex" (Acari: Ixodidae) were sequenced. Sequence variation was assessed for the North American species I. scapularis, I. dammini, and I. pacificus at three levels: within individual/population, between individuals of different geographic origin within a species, and between species. Both spacers are highly variable, particularly with regard to small deletions and additions which may arise via replication slippage. Homogenization of rDNA multigene arrays for particular sequence variants appears to occur at a relatively rapid rate, since I. pacificus sequences differ from the others at numerous invariant sites, facilitating the use of these sequences to assess sibling species relationships. Based on maximum parsimony and two distance methods (unweighted pair-group with arithmetic means and neighbor-joining), sequence variation in ITS1 and ITS2 suggests that I. scapularis and I. dammini are not distinct species and that even individuals from geographically isolated locations are very similar. Individuals from geographically separated populations of I. pacificus appear to be relatively less closely related to each other but distinct from those of I. scapularis/dammini. In I. scapularis/dammini, diversity within and between individuals from geographic populations contributed equally to total sequence diversity.