Microorganisms in the ticks Amblyomma dissimile Koch 1844 and Amblyomma rotundatum Koch 1844 collected from snakes in Brazil

Knowledge about ticks (Acari) and screening of ticks parasitizing various hosts are necessary to understand the epidemiology of tick‐borne pathogens. The objective of this study was to investigate tick infestations on snakes (Reptilia: Squamata: Serpentes) arriving at the serpentarium at the Institute Vital Brazil, Rio de Janeiro. Some of the identified ticks were individually tested for the presence of bacteria of the genera Rickettsia (Rickettsiales: Rickettsiaceae), Borrelia (Spirochaetales: Spirochaetaceae), Coxiella (Legionellales: Coxiellaceae), Bartonella (Rhizobiales: Bartonellaceae), Ehrlichia (Rickettsiales: Anaplasmataceae), Anaplasma (Rickettsiales: Anaplasmataceae), and Apicomplexa protozoa of the genera Babesia (Piroplasmida: Babesiidae) and Hepatozoon (Eucoccidiorida: Hepatozoidae). A total of 115 hard ticks (Ixodida: Ixodidae) were collected from 17 host individuals obtained from four Brazilian states. Two species of tick were identified: Amblyomma dissimile Koch 1844 (four larvae, 16 nymphs, 40 adults), and Amblyomma rotundatum Koch 1844 (12 nymphs, 43 adults). Rickettsia bellii was found in A. rotundatum and A. dissimile ticks and Rickettsia sp. strain Colombianensi, Anaplasma‐like and Hepatozoon sp. in A. dissimile ticks. Among the tested ticks, no DNA of Borrelia, Bartonella, Coxiella or Babesia was found. The present findings extend the geographic range of Rickettsia sp. strain Colombianensi in Brazil and provide novel tick–host associations.     

Phylogenetic position of Cowdria ruminantium (Rickettsiales) determined by analysis of amplified 16S ribosomal DNA sequences.

The 16S ribosomal DNA sequence of Cowdria ruminantium, the causative agent of heartwater disease in ruminants, was determined. An analysis of this sequence showed that C. ruminantium forms a tight phylogenetic cluster with the canine pathogen Ehrlichia canis and the human pathogen Ehrlichia chaffeensis. Although a close relationship between the genus Cowdria and several members of the tribe Ehrlichieae has been suspected previously, the tight phylogenetic cluster with E. canis and E. chaffeensis is surprising in view of known differences in host preference and target cells.     

Synonymy of Boophilus Curtice, 1891 with Rhipicephalus Koch, 1844 (Acari: Ixodidae)

Recent molecular and morphological studies of the genera Rhipicephalus Koch, 1844 and Boophilus Curtice, 1891 revealed that the five species of Boophilus make the genus Rhipicephalus paraphyletic. Thus, Rhipicephalus Koch, 1844 is not a monophyletic (natural) lineage and some species of Rhipicephalus are more closely related to the species of Boophilus than to other species of Rhipicephalus. Here, we revise these genera: Boophilus is synonymised with Rhipicephalus, and Rhipicephalus (sensu lato) (including Boophilus) is redefined. By synonymising Boophilus with Rhipicephalus, we have changed the nomenclature so that it reflects our understanding of the phylogeny of these ticks. Boophilus is retained as a subgenus of Rhipicephalus, so the synonymy of Boophilus with Rhipicephalus does not result in the loss of the name Boophilus. In addition, Rhipicephalus is a well-known genus and the change proposed is simple -- all five species of Boophilus become members of Rhipicephalus (Boophilus).     

Amblyomma triste (Koch, 1844) (Acari: Ixodidae): morphological description of the ovary and of vitellogenesis

The present study presents the morphology, histology, and the dynamics of vitellogenesis in females of the tick Amblyomma triste. The ovary in this species is of the panoistic type, therefore it lacks nurse cells. It is composed of a layer of epithelial cells that outwardly form the wall of the ovary, but also originate the pedicel, the structure that attaches the oocytes to its external margin, as well the oocytes themselves. In Amblyomma triste, the oocytes develop in four synchronic stages, which differs from the process in other tick species. The classification of the stages of the oocytes was carried out based on the presence of four morphologic characteristics: cytoplasm appearance; site of the germ vesicle; presence, quantity, and constitution of the yolk granules and presence of chorium.     

Improved culture conditions forCowdria ruminantium (Rickettsiales), the agent of heartwater disease of domestic ruminants

The causal agent of heartwater disease of domestic ruminants,Cowdria ruminantium, can, with difficulty, be isolated and passaged in lines of bovine endothelial cells grown in the presence of the Glasgow modification of Eagle's minimal essential medium. However, when Leibovitz's L-15 medium supplemented with 0.45% glucose at pH 6.0–6.5 is used as maintenance medium for these cells, isolation and serial passage may routinely be achieved.     

Host-parasite relationships of the genus Hyalomma Koch, 1844 (Acari, Ixodidae) and their connection with microevolutionary process

Host-parasite relationships of Hyalomma species of the world fauna are analyzed. The majority of species infests predominately various mammals. Birds and reptiles are used as preferred hosts by several Hyalomma species, and only on certain stage: adults of H. aegyptium parasitize tortoises; immature stages of H. marginatum parasitize birds. It is hypothesized that relationships of H. aegyptium adults (subgenus Hyalomma s. str.) with reptiles are secondarily in origin. Immature stages of H. aegyptium retain the primary wide diapason of hosts, which are various small mammals, birds and reptiles. The life cycle of this species is the three-host type that is considered as a primary type in ixodid ticks. A typical scheme of relationships with their hosts in all well-examined Hyalommina species has following features: the adult stage parasitize large and medium sized mammals, immature stages parasitize small mammals, three-host life cycle. A variety of preferred hosts and types of life cycle is observed in the subgenus Euhyalomma. All species of this subgenus can be arranged into two groups. In the first group, the immature stages infest only small mammals and birds, and the adults parasitize large mammals; this type of host preferences is probably primary host-parasite relationships of Hyalomma. This group includes: H. albiparmatum, H. asiaticum, H. excavatum, H. franchinii, H. impeltatum, H. impressum, H. lusitanicum, H. marginatum, H. nitidum, H. schulzei, and H. truncatum. Hyalomma marginatum and H. schulzei are two-host species; H. excavatum is two- or three-host tick. All the remaining species (except H. albiparmatum, which life cycle is unknown) are three-host ticks. In the second group, the immature stages as well as the adult stage parasitize large mammals. This group includes: H. dromedarii, H. anatolicum, and H. scupense. These species are two- or one-host ticks.     

Correlation between antibodies to Cowdria ruminantium (Rickettsiales) in cattle and the distribution of Amblyomma vector ticks in Zimbabwe

Cowdriosis, caused by Cowdria ruminantium, is transmitted by Amblyomma ticks, which are widely distributed in Zimbabwe. To assess the distribution of this disease in Zimbabwe, cattle either exposed to Amblyomma ticks or maintained in areas free from these ticks were tested for antibodies to Cowdria. A total of 324 sera were tested using competitive ELISA and the indirect fluorescent antibody test (IFAT). At diptanks in Amblyomma-infested areas 52% (n=95) and 26% (n=47) of sera were positive by cELISA and IFAT, respectively. At diptanks in Amblyomma-free areas 11% (n=125) and 10% (n=134) of sera were positive by cELISA and IFAT, respectively. The results were significantly different between Amblyomma-infested and tick-free areas (²=24.73, P0.005 for IFAT and ²=57.53, P0.005 for cELISA). High background readings in field sera, possibly due to cross-reactive antibodies to Ehrlichia spp., complicated the determination of a realistic cut-off point, especially in cELISA. On the basis of the distribution of Amblyomma ticks, currently a large part of Zimbabwe can be considered endemic for the disease.     

History of the geographic ranges and migration routes of ticks in the genus Dermacentor Koch, 1844 (Ixodidae)

The mutually checking parasitological and zoogeographic criteria for the issue in question made it possible to express the viewpoint and present supporting data on the origin and spread of Dermacentor ticks. Their origin was dated back to Oligocene (38 mln years ago). Having appeared in Angar Mainland, the ticks spread by land in Europe, North America (Miocene, 25 mln years ago) and Africa (Pliocene, 5 mln years ago). The list of species according to zoogeographic regions is given.     

Description of a new species of Dermacentor Koch, 1844 (Acari: Ixodidae) from Laos and Thailand

Systematic Parasitology - Dermacentor laothaiensis n. sp. (Acari: Ixodidae) is described based on adults ex wild boar and vegetation from Laos and Thailand. Adults of D. laothaiensis n. sp. are...     

Studies on the ecology of Amblyomma marmoreum Koch 1844 (Acarnia: Ixodidae).

In the Eastern Cape Province of South Africa, larvae and nymphs of Ablyomma marmoreum Koch occur in habitats in which there is tree cover and herbaceous ground cover. Immatures of A. marmoreum are parasitic on reptiles, birds, and mammals. Adults occur only on reptiles. The major host for all stages is the moutain tortoise (Geochelone pardalis), and in the home areas of tortoises the density of ticks is high. Larvae are active in late summer and autumn. The rate of feeding is temperature-dependent, and some larvae which attach on tortoises in late autumn do not complete feeding until the following spring. Nymphs which occur in the home area of a tortoise become active in response to CO2 in early spring. Adults, and nymphs which occur outside the home area of a tortoise, become active in summer in response to rising temperatures. In nymphs which feed in spring, and hence develop into adults in midsummer, the life cycle is completed in 1 year. In nymphs which fed in midsummer, the life cycle is completed in 2 years.     

Cholesteryl esters on the body surfaces of the camel tick,Hyalomma dromedarii (Koch, 1844) and the brown dog tick,Rhipicephalus sanguineus (Latreille, 1806)

Cholesteryl esters were found to constitute a major component of the lipids coating the body cuticle of females of the camel tick, Hyalomma dromedarii and the brown dog tick, Rhipicephalus sanguineus. One or more cholesteryl esters, alone or in combination, have been shown to serve as the mounting sex pheromone of several species of ixodid ticks. Consequently, knowledge of these compounds is important for an understanding of the mating behavior of these ticks. Based on thin layer chromatography, cholesterol and cholesteryl esters were the most abundant neutral lipids found on the body surfaces of fed females of these two species. Analysis using HPLC demonstrated significant quantities of the following compounds, tentatively identified as cholesteryl esters (expressed in micrograms per female equivalent), in H. dromedarii: Cholesteryl acetate 18.2; cholesteryl laurate, 6.8; cholesteryl linoleate, 24.8; cholesteryl oleate, 12.9; cholesteryl palmitate, 0.3; and cholesteryl stearate 1.7.In contrast, the same method revealed only 3 cholesteryl esters in extracts of females of R. sanguineus: Cholesteryl acetate, 2.0; cholesteryl linoleate, 8.5; and cholesteryl oleate, 3.0. In both species, two unidentified peaks, with the spectral characteristics of cholesteryl esters, were also observed. Identification of the cholesteryl esters was confirmed: by (1) positive bioassay results with conspecific (H. dromedarii) males and heterospecific (Dermacentor variabilis) males; (2) similarity of ultraviolet spectra between identified sample peaks and authentic standards; and (3) demonstration of cholesterol and the corresponding free fatty acid following enzymatic digestion of each of the HPLC-separated fractions containing the different cholesteryl esters. Comparisons with the cholesteryl ester composition of the mounting sex pheromone of other metastriate Ixodidae are discussed. These findings, along with studies reported previously, suggest that differences in the mounting sex pheromones of ixodid ticks are an important factor in minimizing heterospecific matings in nature.Supported by Cooperative Agreement No. 263-0152-A-00-2207 with the U. S. Agency for International Development to the Department of Infectious Diseases. College of Veterinary Medicine, University of Florida, Gainesville, FL and a subcontract, ODURF No. 536521, to the Department of Biological Sciences, Old Dominion University, Norfolk, VA     

Comparison of efficacy of American and African Amblyomma ticks as vectors of heartwater (Cowdria ruminantium) infection by molecular analyses and transmission trials

The ability of Amblyomma americanum, Amblyomma cajennense, Amblyomma maculatum, and Amblyomma variegatum to acquire and transmit Cowdria ruminantium infection was investigated. Uninfected nymphs were fed on clinically reacting C. ruminantium-infected sheep and then analyzed for infection by specific DNA detection assays and by tick transmission trials. By polymerase chain reaction (PCR), the mean infection prevalence of A. maculatum ticks (50.7%) was similar to that of A. variegatum, Elevage strain (43.5%; P = 0.83) and Petit Bourg strain (45.9%; P = 0.26) ticks. Though Amblyomma hebraeum were not tested by PCR, by DNA probe their infection prevalence was 94%. In contrast, A. americanum and A. cajennense ticks demonstrated very low susceptibility to C. ruminantium, and the prevalence of infection by PCR was approximately 1%. The higher susceptibility of A. maculatum and A. variegatum to C. ruminantium correlated with superior vector efficiency, depicted by similar prepatent periods and severity of disease transmissions to sheep. Amblyomma americanum and A. cajennense failed to transmit infection, confirming that low susceptibility to C. ruminantium correlates with the poor vector status of these species. These results highlight the importance of A. maculatum as a potential vector that is likely to play a major role in the establishment and maintenance of heartwater, if the disease were to be introduced to the U.S.A., Central, and South America.     

Ultrastructural detection of proteins, lipids and carbohydrates in oocytes of Amblyomma triste (Koch, 1844) (Acari; Ixodidae) during the vitellogenesis process

The ovary of the tick Amblyomma triste is classified as panoistic, which is characterized by the presence of oogonia without nurse and follicular cells. The present study has demonstrated that the oocytes in all developmental stages (I-IV) are attached to the ovary through a pedicel, a cellular structure that synthesizes and provides carbohydrate, lipids and proteins supplies for the oocytes during the vitellogenesis process. The lipids are deposited during all oocyte stages; they are freely distributed as observed in stages II, III and IV or they form complexes with other elements. The proteins are also deposited in all stages of the oocytes, however, in lower concentration in the stage IV. There is carbohydrate deposition from oocytes in the stage II as well as in stages III and IV. In addition, the present work has demonstrated that the oocyte yolk of A. triste has a glycolipoprotein nature and the elements are deposited in the following sequence: firstly the lipids and proteins, and finally the carbohydrates.