Febrile illness in Malaysia--an analysis of 1,629 hospitalized patients

We studied 1,629 febrile patients from a rural area of Malaysia, and made a laboratory diagnosis in 1,025 (62.9%) cases. Scrub typhus was the most frequent diagnosis (19.3% of all illnesses) followed by typhoid and paratyphoid (7.4%); flavivirus infection (7.0%); leptospirosis (6.8%); and malaria (6.2%). The hospital mortality was very low (0.5% of all febrile patients). The high prevalence of scrub typhus in oil palm laborers (46.8% of all febrile illnesses in that group) was confirmed. In rural Malaysia, therapy with chloramphenicol or a tetracycline would be appropriate for undiagnosed patients in whom malaria has been excluded. Failure to respond to tetracycline within 48 hours would usually suggest a diagnosis of typhoid, and indicate the need for a change in therapy.

Diagnostic criteria for scrub typhus: probability values for immunofluorescent antibody and Proteus OXK agglutinin titers

The sensitivities and specificities of the indirect microimmunofluorescent antibody (IFA) and Weil-Felix (OXK) tests for scrub typhus were established for a range of titers using groups of diseased and control (other febrile illnesses) patients diagnosed by other methods. At a cut-off point of greater than or equal to 1:400, the IFA test was 0.96 specific, and at greater than or equal to 1:320, the OXK was 0.97 specific. Using either these highly specific levels of antibody or other rigorous diagnostic criteria (isolation or 4-fold rising titers), the prevalence of scrub typhus infection was determined to be 0.22 in an unselected population of febrile patients in a rural Malaysian hospital. Probability values (Pr) for the correct diagnosis of scrub typhus were then calculated from the specificity, sensitivity and prevalence determination for a range of titers. The Pr for an OXK titer of greater than or equal to 1:320 was 0.79, and the Pr for an IFA titer of greater than or equal to 1:400 was 0.78. When both these titers were present in a single specimen, the Pr increased to 0.96.

Development of antibody to Rickettsia tsutsugamushi in soldiers in Malaysia

Malaysian, British and New Zealand soldiers were tested for evidence of infection with Rickettsia tsutsugamushi after several weeks' exposure to the infection during field exercises in Malaysia. 39 (5.0%) of 787 British and New Zealand soldiers developed immunofluorescent antibody (IFA) to R. tsutsugamushi to a titre of 1:50 and two (0.3%) to a titre of 1:100. 11 (1.5%) of 751 Malaysian soldiers also developed low titres less than or equal to 1:100. These low antibody levels were not correlated with clinical disease, and their significance is unknown. Seven (0.9%) of the Malaysians showed an IFA rise to greater than or equal to 1:200, and three of these experienced febrile illnesses, one lasting two weeks. An additional eight Malaysian soldiers had an IFA titre of greater than or equal to 1:400 when first tested and six of these also had a Proteus OXK agglutinin titre of greater than or equal to 1:160, indicating infection shortly before the study.

Serodiagnosis of tsutsugamushi fever (scrub typhus) by the indirect immunoperoxidase technique

The indirect immunoperoxidase technique was assessed for the serodiagnosis of tsutsugamushi fever (scrub typhus). The antigens were peritoneal smears prepared from mice infected intraperitoneally with the Karp, Kato, and Gilliam strains of Rickettsia tsutsugamushi. Treatment of the mice with cyclophosphamide apparently increased the number of the rickettsiae, and it minimized the exudate that interfered with the specific staining. The rickettsiae were seen as clusters in the juxtanuclear region of the mesothelial cells and also as free particles outside of the cells. By the indirect immunoperoxidase technique, the sera from all of the patients (49 samples from 30 patients) were positive for the R. tsutsugamushi antibody. The antibody titers (immunoglobulin G [IgG] and IgM) determined by the indirect immunoperoxidase technique correlated with those determined by the indirect immunofluorescence technique. Thus, the indirect immunoperoxidase technique was useful for quantifying both IgG and IgM antibodies to the rickettsia.

New paper enzyme-linked immunosorbent technique compared with microimmunofluorescence for detection of human serum antibodies to Rickettsia tsutsugamushi

A new paper enzyme-linked immunosorbent assay was developed for the screening and titration of human serum antibodies against the scrub typhus rickettsia, Rickettsia tsutsugamushi. The objective [corrected] was to provide a relatively simple method for antibody screening which required neither sophisticated laboratory equipment nor a high degree of technological skill. The technique develops an enzyme product from filter paper saturated with a 5-aminosalicylic acid substrate and enzymatically reacted with a commerically available anti-human immunoglobulin G peroxidase conjugate. The product of the enzymatic reaction can be interpreted visually. Comparison of 351 human sera tested by the immunofluorescent and paper enzyme-linked immunosorbent assays against a three-antigen pool of the Karp, Kato, and Gilliam strains of R. tsutsugamushi demonstrated an agreement of 96%. The sensitivity of the paper enzyme-linked immunosorbent assay as compared to immunofluorescence was 98.2%, and the specificity was 94.4%.

Presence of antibodies to scrub typhus and murine typhus in dogs from Selangor, Peninsular, Malaysia

Dog sera, collected from different communities throughout Selangor, Peninsular Malaysia, were investigated for the presence of antibodies to R. tsutsugamushi and R. typhi. Scrub typhus antibodies were present in animals from the rural areas only, whereas murine typhus antibodies were observed in equal numbers of dogs from both rural and metropolitan areas. Greater percentage of dogs from suburban areas had demonstrable antibody titers to murine typhus than from the urban area.

Clinical observations of scrub typhus on Penghu (the Pescadores Islands)

Between May and September 1973, 68 cases of scrub typhus in Chinese military personnel on the Pescadores Islands were studied. The common symptoms and signs were fever, chills, headache, eschar, myalgia, and lymph node enlargement. Most eschars were located in the axilla, waist, groin and genitals, and neck. These lesions were painless and not noticed by the patients themselves. Regional lymph node enlargement at the site of eschar drainage was common. Relative bradycardia with fever was observed in 40%, a skin rash in 35% of the patients. Leucopenia was noted more frequently in the febrile than in the convalescent stage, but more than half of the patients had a normal count. Lymphocytosis was prominent, especially during the convalescent period. An acceleration of ESR was noted. Instead of depression of the erythroid series in the marrow which was reported previously, 47% of examined patients were found to have erythroid hyperplasia. Two patients showed marked hypocellularity of the marrow in the acute febrile stage; later on became normocellular. Albuminuria was present in 15 and BUN increased in 12 patients. Elevation of serum bilirubin and SGOT was also noted. Biologic false positive VDRL tests were observed in nine patients. In 30 tests elevation of Proteus OX-K titres between 1:160 and 1:640 was noted. A geometric mean OX-K titre rise in the patients is presented; the mean titre reached a peak in the third week of illness, and then fell off. Most of the patients were treated with tetracycline 500 mg every six hours for about nine days. The fever usually subsided within 36 hours. Complications or mortality were not encountered.