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Rickettsial diseases are increasingly found world-wide and should be considered in febrile patients returning from abroad. This case report describes the vasculitic complications of a patient returning from the Republic of South Africa with tick typhus.
To analyze the host dependency of rickettsial growth, NIAS-AeAl-2 insect cells (AeAl2) derived from mosquito were first used in this study. It was demonstrated that typhus group rickettsiae (TGR) grew well in AeAl2 cells, but spotted fever group rickettsiae (SFGR) failed. To elucidate the inhibitory process of the growth of SFGR in AeAl2 cells, the adherence and invasion were first analyzed. SFGR possessed abilities to adhere to and invade AeAl2 cells as well as TGR in contrast to their inability of the growth in the cells. Morphologically, generation of microvilli could not be observed on AeAl2 cells inoculated with either group of rickettsiae. On the contrary, Vero cells inoculated with rickettsiae generated a great number of microvilli that adhered to rickettsiae and engulfed them into the cells. The roles of rickettsial major outer membrane protein A and B (rOmpA and rOmpB) were later investigated using E. coli expressing either rOmpA or rOmpB on their surface. Bacteria expressing either one of the major outer membrane proteins of rickettsiae as well as bacteria not expressing these proteins showed adherence to and invasion of AeAl2 cells. Thus, it is yet to be elucidated whether these major outer membrane proteins have any roles in these steps.
A unique Rickettsia species (Rickettsia thailandii sp. nov.) was identified in an Ixodes granulatus by use of polymerase chain reaction heteroduplex mobility assay by use of segments of the citrate synthase gene. This tick was collected from Rattus rattus from Nakhon Ratchasima province in 1970. Another I. granulatus was infected with Thai tick typhus strain TT-118, Rickettsia honei sp. nov. Stenos, Roux, Walker & Raoult; this tick was removed from a R. rattus collected 4 years later from the same province. Ixodes granulatus is the first tick species in Australasia shown to be infected with R. honei and the unique Rickettsia species.
A new endemic focus of Queensland tick typhus was defined when two cases of Rickettsia australis infection were recognized in Sydney. Although the tick vector is distributed throughout coastal, eastern Australia these are the first cases diagnosed south of Lismore, New South Wales.
Twenty-six cases of a spotted-fever-like illness have been identified on Flinders Island, Tasmania, over a 17 year period. These patients and 335 healthy persons from the island were investigated serologically using the Weil-Felix agglutination test (Proteus sp. antigens OX2, OX19, OXK) and rickettsia-specific microimmunofluorescence. The antigens used in these latter tests comprised one member of the typhus group (Rickettsia typhi) and three members of the spotted fever group (Rickettsia rickettsii, Rickettsia australis and Rickettsia conorii). Patients with Flinders Island spotted fever showed a higher prevalence of positive reactions to the Weil-Felix tests (with OX2 and OX19 antigens) and a higher prevalence of positive results to rickettsia-specific serological tests (with the exception of antibodies to Rickettsia typhi) than did healthy persons; OX2 (36% v. less than 1%); OX19 (36% v. less than 1%); Rickettsia rickettsii (42% v. 1%); Rickettsia australis (46% v. 1%); Rickettsia conorii (42% v. 1%); Rickettsia typhi (4% v. 4%). In seven of the 26 patients (27%) seroconversion was demonstrated by means of Weil-Felix tests, confirming recent infection. In six of these patients seroconversion was also demonstrated in rickettsia-specific tests. Although these results support the clinical evidence that the illness on Flinders Island is caused by a rickettsia of the spotted fever group, the aetiological agent remains to be isolated.
At the acute period of tick-borne typhus an increase in the activities of the main nonspecific resistance factors of the body, and particularly lysozyme, betalysins, complement and properdin, is observed. During convalescence the concentration of lysozyme normalizes and the content of betalysins remains sufficiently high, this indicating that, even in the absence of clinical sings of the disease, the disturbances in homeostasis persist. A decrease in the levels of complement and properdin during convalescence is seemingly linked with their consumption for the formation of immune complexes, eliminated from the body.
A lipophilic thermostable lipopolysaccharide (LPS) complex was isolated by phenol extraction from purified suspensions of the typhus group rickettsiae. The LPS complex is antigenic and possesses some endotoxic properties such as toxicity for actinomycin D-treated mice, pyrogenicity for rabbits and guinea pigs, ability to elicit hypothermia in white rats and local Schwartzman reaction and active cutaneous anaphylaxis in rabbits.
Epidemiological and clinical features of Siberian tick typhus were evaluated in 106 patients. The disease has a tendency to seasonal variations as well as to increasing affection of urban and advanced-age population, less severe course, longer prepatent period, later appearance of exanthem, less frequent occurrence of face hyperemia, that of ocular injection and complications.
The acceleration of antibody formation in animals immunized with chemical typhus vaccine has been shown to occur under the influence of interferonogens (poly I--poly C, tyloron) and leukocytic interferon in experiments on guinea pigs and monkeys.
The data of the comparative study of the immunomodulating action of donor interferon and reaferon in experiments with typhus vaccine, used as an experimental model, on monkeys of different species and guinea pigs are presented. One of the main properties of interferons, besides their antiviral activity, is their capacity for producing an immunomodulating effect.
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