Sexual transmission of spotted fever group rickettsiae by infected male ticks: detection of rickettsiae in immature spermatozoa of Ixodes ricinus.

Electron microscopic evidence is provided showing that the newly described "Swiss agent," a spotted fever group rickettsia, is incorporated into the reproductive cells of its male tick vector, Ixodes ricinus. Rickettsiae were found in spermatogonia, spermatocytes, and maturing spermatids. The potential significance of these observations is briefly discussed in relation to published data on sexual transmission of rickettsiae by ticks.     

Ehrlichia phagocytophila genogroup rickettsiae in ixodid ticks from California collected in 1995 and 1996.

A total of 1,246 ixodid ticks collected in 1995 and 1996 from seven California counties were examined for the presence of Ehrlichia phagocytophila genogroup rickettsiae by using a nested PCR technique. Of 1,112 adult Ixodes pacificus Cooley and Kohls ticks tested, nine pools, each containing five ticks, were positive (minimum percentage of ticks harboring detectable ehrlichiae, 0.8%). Positive ticks were limited to four of the seven counties (Sonoma, El Dorado, Santa Cruz, and Orange). In Santa Cruz County, three positive pools were identified at the home of an individual with prior confirmed human granulocytic ehrlichiosis. In El Dorado County, positive ticks were found at sites where cases of granulocytic ehrlichiosis in a horse and a llama had recently occurred. Among 47 nymphal I. pacificus ticks collected in Sonoma County, one positive pool was identified. Fifty-seven adult Dermacentor occidentalis Marx and 30 adult D. variabilis Say ticks, collected chiefly in southern California, were negative. These data, although preliminary, suggest that the prevalence of E. phagocytophila genogroup rickettsiae in ixodid ticks of California may be lower than in cognate vector populations (i.e., I. scapularis Say = I. dammini Spielman, Clifford, Piesman, and Corwin) in the eastern and midwestern United States.     

Distribution of spotted fever group rickettsiae in select tissues of experimentally infected and field-collected Gulf Coast ticks

Salivary glands, midgut, Malpighian tubules, and ovaries were dissected from infected, colony-derived Amblyomma maculatum (Gulf Coast ticks) injected as nymphs with either Rickettsia parkeri (a spotted fever group rickettsia [SFGR]; treatment) or phosphate-buffered saline (negative control). For comparison, similar tissues were dissected from hemolymph-positive, field-collected ticks. Tissues were analyzed by indirect fluorescent antibody (IFA) tests. All phosphate-buffered saline-injected ticks were IFA negative, whereas SFGR were detected by IFA in 100% of the salivary glands and ovaries and 78 and 75% of midgut and Malpighian tubule samples, respectively, of R. parkeri-injected ticks. Nearly 22% (10/46) of the field-collected ticks were hemolymph positive. Of those, SFGR were detected by IFA in 80% of the salivary glands, 67% of the ovaries, and 60% in the midgut and Malpighian tubules. This is the first study to assess the distribution of SFGR in select tissues of A. maculatum ticks.     

Isolation by a sensitive centrifugation cell culture system of 52 strains of spotted fever group rickettsiae from ticks collected in France.

Boutonneuse fever caused by Rickettsia conorii is transmitted mainly by the brown dog tick, Rhipicephalus sanguineus. We collected 540 ticks in Marseille, France, and tried to isolate as many strains of rickettsia as possible. Ticks were evaluated for the presence of rickettsia by the hemolymph test and by a new culture system, the centrifugation-shell vial technique. We avoided contamination in the culture system. Prior to ticks being submitted to the hemolymph test, they were disinfected. Only 5.6% (27 of 478) of the cultures were contaminated. A drop of hemolymph from each of 478 R. sanguineus ticks was cultured in two shell vials, and another drop was stained by the Gimenez method or indirect immunofluorescence. Since Gimenez staining in our hands was not satisfactory, comparison of the hemolymph test and culture is based on the results of indirect immunofluorescence. Thus, 50 of 369 (13.5%) examined ticks were hemolymph test positive, and 44 (11.9%) cultures were positive. After disinfection, another pool of 62 ticks were examined by the hemolymph test. The ticks were kept individually in a sterile environment. A few days later, the hemolymph of these ticks was collected again and cultured. The contamination rate was not significantly higher (6.4%) than in the above-described conditions. It allowed us to isolate eight more strains. Thus, we recommend screening ticks with the hemolymph test and culturing only the hemolymph test-positive ticks.     

First molecular detection of the human pathogen Rickettsia raoultii and other spotted fever group rickettsiae in Ixodid ticks from wild and domestic mammals

Parasitology Research - Tick-borne rickettsioses are recognized as emerging vector-borne infections capable of infecting both human and animal hosts worldwide. This study focuses on the detection...     

Fatty acid composition of rickettsiae

The fatty acid compositions of selected strains of rickettsiae were studied by gas-liquid chromatography. The profiles of all the rickettsiae except Coxiella burnetii were qualitatively similar. The fatty acid composition of C. burnetii was similar to that of certain Legionella species.     

Biochemistry of rickettsiae: recent advances

The application of new biotechnology to the study of the biochemistry of rickettsiae was a prominent feature of the presentations at the 3rd International Symposium on Rickettsiae and Rickettsial Diseases, held in Smolenice near Bratislava in September 1984. This review is an attempt to summarize recent advances leading up to these presentations as well as the studies that have been reported in the two years since the meeting. Since rickettsiae are intracellular parasites, most reviews deal with the interaction of rickettsiae with host cells. It is useful, however, to focus also--as we have done--on the properties of rickettsiae that can be demonstrated in the absence of their hosts, although, undoubtedly, many of these properties reflect adaptation to an intracellular microenvironment.     

Differentiation of rickettsiae by groEL gene analysis

The nucleotide sequences (534 to 546 bp) of the groEL gene, which encodes the 60-kDa heat shock protein GroEL, from 15 rickettsial strains were determined and compared. In the phylogenetic tree created by the unweighted pair group method with arithmetic averages and the neighbor-joining method, rickettsial strains could be distinguished from Ehrlichia strains. Five spotted fever group strains, four typhus group strains, and six scrub typhus group (STG) strains were differentiated as distinct entities. Unlike gltA and ompA gene analyses, differentiation between members of the genus Rickettsia and the STG rickettsiae by groEL gene analysis was possible. In comparison with 16S rRNA gene analysis, the groEL gene has a higher degree of divergence among the rickettsiae. We therefore successfully developed rapid differentiation methods, PCR-restriction fragment length polymorphism analysis and a species-specific PCR, based on the groEL gene sequences. Four Korean isolates were identified by these methods and groEL gene analysis. The results suggest that the groEL gene is useful for the identification and characterization of rickettsiae.