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.     

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     

湖南主要经济蛇类养殖场的设计与建造调查研究

目的研究出一种适合湖南地域理想的科学经济蛇类人工养殖场。方法采用调查研究法、试验法、归纳总结法等研究方法。结果总结出湖南省经济蛇类养殖场主要有蛇房、露天蛇场、室内外结合蛇场等3种模式,首创了“湖南立体蛇场”模式。结论在湖南省境内采用“湖南立体蛇场”模式进行经济蛇类的养殖效果较好,不仅简单易建、经济合算,而且科学合理、实用方便,达到了预期的目的。     

Ectoparasite loads decrease the fitness of alpine marmots (Marmota marmota) but are not a cost of sociality

Parasites arc often considered an unavoidable cost of livingin groups. We examined this hypothesis by investigating theectoparasite fauna of a free-living alpine marmot population,a highly social sciurid species. Only a single important ectoparasitewas found, the mite Echinonyssus blanchardi. Heavy infestationwith this mite correlated with reproductive success of marmotsin two ways. Infant winter mortality increased with ectoparasiteload, probably because ectoparasites reduced the ability ofparents and alloparents to warm infants during hibernation.Litters produced by females exposed to a high number of mitesduring the preceding winter were weaned later. Late weanershad a lower chance of surviving hibernation. However, we foundno relationship between ectoparasite load and group size ormarmot density. Instead, the number of E. blanchardi per animalwas lower in areas where marmot groups were clumped, i.e., infavorable habitats. Although ectoparasites most likely decreasethe fitess of alpine marmots to some extent, they should notbe considered a cost of social life in this species.     

黑龙江立克次体与黑龙江蜱传斑点热研究概况

黑龙江立克次体是近年发现的斑点热群立克次体新种,由其引起的疾病为黑龙江蜱传斑点热。综述了黑龙江立克次体的发现、分离鉴定、病原学和分子生物学特征,介绍了黑龙江蜱传斑点热的流行病学、临床表现及治疗与预防。     

The evolution of insect/vertebrate associations

The evolution of close vertebrate associations has occurred in seven orders of insects, resulting in a great diversity of interactions which range from commensalism to true parasitism. The evolution of each taxon of vertebrate associates is discussed in turn, some new ideas on the development of certain groups are presented and, on a broader scale, a general model for the evolution of ectoparasitic insects is proposed. It argues that all vertebrate associates have evolved along one of two macroevolutionary pathways which differ only in the sequencing of adaptations facilitating host association and host feeding. These pathways lead to parasite types which differ greatly in their life history and intimacy of host association.
Some microevolutionary processes influencing the diversification of ectoparasites are discussed, in particular the process of insect/vertebrate coevolution and the forms this may take. Host specificity, one consequence of coevolution, is recognised as an important factor influencing the structure of ectoparasite communities, and a hypothesis is presented that competition between ectoparasite species, mediated by host defensive responses, is also important in determining community structure.