Historical and recent evidence for close relationships among Rickettsia parkeri,R. conorii,R. africae,and R. sibirica: Implications for rickettsial taxonomy

Rickettsia parkeri, a member of the spotted fever group rickettsias, was first described in 1939 and was thought to be non‐pathogenic until recently, when it was found to cause a spotted fever‐like illness in humans and areas of necrosis (eschars) at the sites of tick bites. Accordingly, there is currently much interest in this emerging pathogen. In this study, all published articles concerning R. parkeri were reviewed and analyzed for evidence of relatedness among this agent and other spotted fever group (SFG) rickettsiae which also produce similar clinical syndromes and/or eschars, including R. conorii, R. africae, and R. sibirica. A synthesis of the historical (antigenic) and recent (molecular) data supporting a phylogenetic sub‐grouping of these SFG organisms is presented and comments are offered about the taxonomy of rickettsial organisms in general, and R. parkeri in particular.     

Rickettsia amblyommii infecting Amblyomma sculptum in endemic spotted fever area from southeastern Brazil

The Rickettsia bacteria include the aetiological agents for the human spotted fever (SF) disease. In the present study, a SF groupRickettsia amblyommii related bacterium was detected in a field collected Amblyomma sculptum (Amblyomma cajennense species complex) tick from a Brazilian SF endemic site in southeastern Brazil, in the municipality of Juiz de Fora, state of Minas Gerais. Genetic analysis based on genes ompA,ompB and htrA showed that the detected strain, named R. amblyommii str. JF, is related to the speciesR. amblyommii.     

The natural hosts for larvae and nymphs of Amblyomma neumanni and Amblyomma parvum (Acari: Ixodidae)

Based on the hypothesis that birds and rodents are important hosts for subadults of the Neotropical Amblyomma neumanni and Amblyomma parvum ticks, a survey of these type of hosts was carried out from July 2004 to March 2006, in Quilino (A. parvum) and Dean Funes (A. neumanni), Córdoba province, Argentina. Additionally, monthly tick counts were performed on cattle and goats with occasional tick search in other domestic hosts. Records of questing height of subadult ticks on vegetation were also carried out monthly. Rodents (n = 123) and birds (n = 122) captured in Dean Funes showed no infestation with A. neumanni. Apart of few nymphs found on horses, all larvae and nymphs of A. neumanni were on cattle with a larval prevalence and mean number of 22.2%, and 7.7 ± 22.52, respectively, and a prevalence of nymphs of 47.8% with a mean of 7.9 ± 18.49. The average questing height of larvae and nymphs of A. neumanni was 23.5 ± 17.1 cm and 30.7 ± 26.7 cm, respectively. A total of 138 rodents and 130 birds were captured in Quilino but the Caviidae rodent Galea musteloides carried 99.3% of larvae and 99.8% of nymphs of A. parvum, and no immature stages were detected on cattle, goat or vegetation. Tick counts on G. musteloides (n = 74) showed a prevalence of 42% and a mean number of 9.9 ± 24.83 for larvae, while nymphal infestation had a prevalence of 56.5% and a mean of 8.7 ± 11.31. Cattle appear to be suitable hosts to sustain the complete cycle of A. neumanni in nature (adult ticks infest cattle too) and questing height of subadults indicates that they are expecting to feed on medium and large-sized mammals, such as cattle and other ungulates. At least in the study site, G. musteloides is the principal host for the survival strategy of A. parvum subadults; adult ticks are common on cattle and goats. These hosts are introduced in the Neotropics but A. neumanni was able to develop a surrogate cycle independent of native hosts while A. parvum still depends on probably primeval hosts to sustain their larvae and nymphs.     

Fine Structure of the Sporogonic Stages of Nosema parkeri

SYNOPSIS The fine structure of sporogonic stages of Nosema parkeri Krinsky, a microsporidan from the argasid tick, Ornithodoros parkeri Cooley, is described. Developmental changes in the spore coat and cytoplasmic organelles are discussed. As a sporoblast transforms into a spore, the organelles become more compact and the membranes surrounding them appear to become more taut. It is suggested that the polaroplast complex is involved in fluid transport during development of the spore. Organelles in the mature spore include 2 contiguous nuclei enveloped in a lattice containing ribosome-like particles, a polaroplast complex composed of laminar and saccular regions, and a coiled tubular polar filament attached to a polar sac. Sporogonic stages do not appear to have mitochondria, Golgi apparatus, or a posterior vacuole. The fine structure of the spore of N. parkeri is very similar to that of species of Nosema found in insects, crustaceans, and trematodes.     

Amblyomma Tigrinum (Acari: Ixodidae) in Relation to Phytogeography of Central-Northern Argentina with Notes on Hosts and Seasonal Distribution

The findings of Amblyomma tigrinum in continental Argentina north of 40°S are presented according to phytogeographic domains (Andean–Patagonic, Amazonian and Chaco) and the seasonal distribution is depicted on a monthly basis. A total of 718 adult ticks and four nymphs were found. A. tigrinum ticks were present in all domains. Adult ticks were found all year round but they were more abundant during the summer. Most ticks were found on domestic dogs but the survey has a bias to domestic hosts. It is speculated that the cycle of immature is bound to shelters that mitigate extreme climatic conditions, thus explaining the finding of this tick species in contrasting ecological areas.     

Distributions of the vectors of heartwater, Amblyomma hebraeum and Amblyomma variegatum (Acari: Ixodidae), in Zimbabwe

The tick vectors of heartwater (Cowdria ruminantium infection) in Zimbabwe, Amblyomma hebraeum and Amblyomma variegatum, historically were believed to be confined to the low-lying regions of the south and north-west of the country. However, country-wide surveys performed in 19751980 and 19881991 demonstrated that both species were also established in western parts of the highveld plateau and had started to encroach on the predominantly heartwater-free central and eastern highveld regions. To determine the current distributions of both the vectors and evaluate the potential threat of heartwater to animals in the highveld, a survey of ticks infesting cattle was performed in 1996 at 2994 locations in small-holder and large-scale commercial farming areas throughout Zimbabwe. Amblyomma hebraeum was collected at 1329 locations, A. variegatum at 72 locations and both A. hebraeum and A. variegatum at 13 locations. The results demonstrated that A. hebraeum was present, as previously recorded, throughout the southern half of the country and appeared to have undergone further limited spread into the central and eastern highveld regions. Only the northern-most region of the country appeared to be free of this species. Amblyomma variegatum was collected mainly in the north-west, as previously recorded, but was also found at isolated locations across the central highveld region and along the eastern border with Mozambique. This species was, however, still absent from the southern half and the northern-most regions of the country. An overlap of the distributions of the two species existed within a zone along the southern and eastern regions of the distribution of A. variegatum. These results suggest that the vectors of heartwater are spreading and threaten to introduce heartwater into intensive livestock-producing regions of the country.Exp Appl Acarol 22: 725740 © 1998 Kluwer Academic Publishers     

高山倭蛙消化道结构初步观察

高山倭蛙食道粘膜上皮为复层柱状上皮,且固有膜中有丰富的复泡状腺;胃贲门部粘膜上皮无杯状细胞,PAS反应显示固有膜中有深红色颗粒分布,胃体中胃腺丰富;肠分为小肠、大肠、直肠3部分.小肠和直肠上皮中杯状细胞数量多.无尾类消化道结构与海拔高度无明显相关关系.