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A case of scrub typhus due to Rickettsia tsutsugamushi is reported. This imported rickettsial disease was contracted by a 30-year-old woman while traveling in Thailand, and was transmitted by an infected mite's bite. Diagnosis was confirmed by specific serology and resolution was obtained by tetracycline therapy. Current concepts of the disease are reviewed.
The indirect immunofluorescent technic, recommended by WHO, allows us to consider again, the problem of rickettsial diseases in Tunisia. This pathology, always actual, presents, also in epidemiological as in clinical aspect, a predominance for Mediterranean spotted fever by R. conori. Murin typhus by R. mooseri is still remained, but its incidence seems to be slight. The frequency of Q Fever must to be determined.
Rickettsioses have nonspecific clinical manifestations, making them difficult to diagnose in a clinical setting. Laboratory testing is usually needed to confirm the diagnosis. Rickettsial isolation is a sensitive and specific diagnostic technique, but the hazards associated with handling pathogenic rickettsiae usually preclude isolation attempts in most laboratories. Rickettsiae can also be detected in infected tissues by fluorescein-labeled antisera or by immunoperoxidase staining, but these techniques lack sensitivity, except when applied to postmortem tissue specimens. However, rickettsial DNA can be detected in acute phase blood specimens by polymerase chain reaction (PCR) technology, and this technique offers the prospect of prompt diagnosis and treatment. Serologic testing remains the most frequently used approach to diagnosis, although antibody tests usually fail to identify rickettsioses early enough to affect the management of individual patients. Available serologic techniques vary considerably in their sensitivity and specificity. Enzyme-linked immunosorbent assays (ELISA) are extremely sensitive, but the general unavailability of specific diagnostic antigens reduces the specificity of this and other serologic techniques. Molecular characterization of rickettsial antigens may soon allow the production of peptide antigens that are specific for each species and could maximize the specificity of test results. No diagnostic technique has any value unless it is applied successfully to the appropriate patient population. Improved surveillance of rickettsial diseases is urgently needed to identify specific areas in which rickettsioses are endemic. Such surveillance data would promote awareness of rickettsioses among local physicians and increase the probability that individual patients with rickettsioses would be identified promptly and receive appropriate therapy early in the course of their illness.
The use of filter paper is an inexpensive and convenient method for collecting, storing, and transporting blood samples for serological studies. In addition, samples occupy little space and can be readily transported without refrigeration. Rickettsial diseases often evolve according to an epidemic mode and are now considered reemerging diseases, especially in developing countries, under conditions where fieldwork could be difficult. The suitability of collecting whole-blood specimens on filter paper discs for rickettsial antibody assay was evaluated. Dried blood specimens from 64 individuals with antibodies to Coxiella burnetii, Bartonella quintana, or Rickettsia conorii were tested for rickettsial antibodies by microimmunofluorescence. Although occasional titers were 1 or 2 dilutions lower than those of tested serum samples, no statistically significant differences were observed. Among patients with negative serology, no false positives were found. This study demonstrated that the recovery of antibodies from finger-stick blood dried on filter paper after elution produces results comparable to those obtained by recovering antibodies from serum. Storing paper samples for 1 month at room temperature or at 4 degrees C did not significantly affect the level of antibodies recovered. This report shows the utility of this sample collection method in developing countries where refrigeration is not possible and venipuncture is problematic.
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Common isolation procedures on chick embryos and laboratory animals are not of great importance for routine diagnosis of rickettsioses. Detection of rickettsiae in skin lesions by immunofluorescence technique allows early diagnosis of Rocky Mountain spotted fever (RMSF). Broad spectrum of methods is at disposal for serological diagnosis of rickettsial diseases. Their choice is determined by laboratory equipment, professionality of laboratory staff, economy and simplicity of the given test. Though complement-fixation and microagglutination tests held their position and will certainly be used in future, the use of indirect immunofluorescence test is recommended for its sensitivity and simplicity. Latex agglutination test is valuable especially in the diagnosis of acute rickettsial infections. Recently introduced ELISA method is expected to fulfil the highest requirements as to sensitivity in differentiation of rickettsioses within the known classification groups. The efforts to obtain efficient antirickettsial vaccines have been limited to preparation of the vaccines against RMSF and Q fever. As to the latter, elaboration of chemovaccine and preparation of chloroform-methanol-treated phase I C. burnetii suspension of decreased reactogenity seem promising in field trials.
The indirect immunoperoxidase (HP) test has been used extensively in most government hospitals in Malaysia for the serodiagnosis of scrub typhus, murine typhus and tick typhus during the 1990s. The test was used to determine the IgG and IgM antibody titers in patients' sera for three rickettsial species, ie Orientia tsutsugamushi OT; the causative agent of scrub typhus), Rickettsia typhi (RT; the causative agent of murine typhus), and TT118 spotted fever group rickettsiae (TT; the causative agent of tick typhus). The serological findings obtained from Malaysian hospitals using the IIP test (1994-1999) were analyzed. During the six-year period, a total of 61,501 patients' sera were tested, of which 9.6%, 10.5%, and 12.9% had antibody (IgG and/or IgM of > or = 1:50) for OT, RT and TT respectively. A total of 8.6%, 9.8%, and 9.7% of sera had IgG antibody of > or = 1:50 for OT, RT, and TT respectively, indicating past infection. A total of 3.4%, 3.8%, and 6.4 % of sera had IgM antibody of > or = 1:50 for OT, RT, and TT respectively, indicating recent infection. A total of 2,986 (4.9%), 1,882 (3.1%), and 1,574 (2.6%) of sera had IgG and/or IgM antibody titers of > or = 1:400 for OT, RT, and TT respectively, suggesting active rickettsial infection. The seropositivity rates of OT, RT and TT varied according to geographical locations. While the seropositivity of OT remained constant during the six-year period, a reduction in the seropositivity of both RT and TT was noted during recent years. The serological findings reflect the endemicity of rickettsial diseases, including tick typhus, and endemic typhus in various parts of Malaysia. Awareness of these diseases by health and medical staff and by the general public is important if the mortality and morbidity associated with scrub typhus, tick typhus, and murine typhus in Malaysia, are to be reduced.
AIM: To describe the first cases of serologically proven riskettsial disease reported in non-travelling New Zealanders. METHODS: We used clinical and laboratory based surveillance, review of clinical records and patient interviews. Information collected included demographics, presenting signs and symptoms, laboratory results, treatment and outcome. A limited seroprevalence study of rural-living friends and relatives was performed. We tested for rickettsial antibodies in the sera of possums trapped on properties close to the area of residence of the first two cases. RESULT: Serological results support the diagnosis of a rickettsial disease in nine patients. Clinical findings at presentation were nonspecific but included fever, rigors and headache. A rash was noted in four (44%). All had abnormal liver enzymes. Eight were hospitalised. No patient died but two were admitted to intensive care. CONCLUSIONS: There is strong clinical and serological evidence that Rickettsia typhi (the causative organism of murine typhus) or a Rickettsia typhi-like organism is present in the greater Auckland region. To prove it, the organism will need to be cultured or rickettsial DNA detected by molecular methods. Rickettsial infection needs to be included in the differential diagnosis of patients presenting with fever, headache and myalgia, particularly in those with rural lifestyles at least in the greater Auckland area.
Rickettsia rickettsii and Rickettsia conorii are the causative agents of two common and serious diseases, Rocky Mountain spotted fever and Mediterranean spotted fever, respectively. In patients naturally infected with either of these organisms, antibodies are produced which cross-react with antigens of the other so extensively that diagnostic tests usually cannot identify the causative agents. The results of this study indicate that serodiagnostic tests with antigen from one of these two organisms could be used to detect antibodies in patients with either of the two rickettsial diseases.
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