Displaying publications 1 - 20 of 22 in total

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  1. Distribution of rats infected with Rickettsia tsutsugamushi (scrub typhus) in an edge habitat
    Muul I, Chai KS
    Southeast Asian J Trop Med Public Health, 1978 Dec;9(4):489-93.
    PMID: 751214
    No focalization of rats (Rattus tiomanicus and R. argentiventer) infected with Rickettsia tsutsugamushi could be discerned over a 500 m trapping transect at the border between a forest and lalang grass (Imperata cylindrica). R. tiomanicus appeared to occupy 250 m of the transect on the average and had periods during which infections were observed which averaged 97 days. Calulations indicated that more than 50% of individuals become infected over their life-time. The high rate of infection in this and other areas described in earlier publications and the habits of the rats suggest that infected mites are densely and widely dispersed in the areas studied in Malaysia.
    Matched MeSH terms: Scrub Typhus/epidemiology*
  2. Recent studies in scrub typhus: a review
    Brown GW
    J R Soc Med, 1978 Jul;71(7):507-10.
    PMID: 359809
    Matched MeSH terms: Scrub Typhus/epidemiology
  3. The longevity of antibody to Rickettsia tsutsugamushi in patients with confirmed scrub typhus
    Saunders JP, Brown GW, Shirai A, Huxsoll DL
    Trans R Soc Trop Med Hyg, 1980;74(2):253-7.
    PMID: 6770503
    Serological surveillance for up to two years of 114 patients with laboratory confirmed scrub typhus showed that antibody to Rickettsia tsutsugamushi as demonstrated by the indirect fluorescent antibody test is short-lived. The mean reversion time from mean peak titre (1:499) was 48.9 weeks and the calculated annual reversion rate to a titre less than 1:50 was 61%. This can be used to estimate attack rates based on point prevalence of antibody. The relationship between antibody prevalence and attack rates observed by other workers was confirmed using this model. The possible uses of the finding and its implications in Malaysia are briefly discussed.
    Matched MeSH terms: Scrub Typhus/epidemiology
  4. The effect of habitat on the prevalence of human scrub typhus in Malaysia
    Cadigan FC, Andre RG, Bolton M, Gan E, Walker JS
    Trans R Soc Trop Med Hyg, 1972;66(4):582-7.
    PMID: 4561007
    Matched MeSH terms: Scrub Typhus/epidemiology*
  5. The prevalence of scrub typhus antibodies in residents of West Malaysia
    Robinson DM, Gan E, Donaldson JR
    Trop Geogr Med, 1976 Dec;28(4):303-8.
    PMID: 827831
    Based on the prevalence of antibody, an estimated 3% of the population of rural Malaysia is infected with Rickettsia tsutsugamushi each year, resulting in positive antibody rates in focal areas of 6 to 69%. Most of these infections do not appear to produce clinical scrub typhus. A wide range of seropositivity rates was found in areas otherwise resembling each other in predominant occupation, terrain, and nearby habitat. The prevalence rates however were significantly higher in people who worked in forested areas and significantly lower in people with urban occupations.
    Matched MeSH terms: Scrub Typhus/epidemiology*
  6. Serological evidence for a high incidence of transmission of Rickettsia tsutsugamushi in two Orang Asli settlements in Peninsular Malaysia
    Brown GW, Robinson DM, Huxsoll DL
    Am J Trop Med Hyg, 1978 Jan;27(1 Pt 1):121-3.
    PMID: 415625
    Two communities of Orang Asli (aborigines) in Peninsular Malaysia were observed for evidence of Rickettsia tsutsugamushi infection over periods of 1-8 mo. Sequential sera were examined for antibody by the indirect immunofluorescence test. The incidence of infection in the two self-selected populations in the two communities was calculated to be 3.9% per month and 3.2% per month.
    Matched MeSH terms: Scrub Typhus/epidemiology*
  7. Mammals and scrub typhus ecology in peninsular Malaysia
    Muul I, Liat LB, Walker JS
    Trans R Soc Trop Med Hyg, 1975;69(1):121-30.
    PMID: 806995
    The overall comparisons of habitats are given in (Table III). The habitats are arranged in order of extent of alterations by man, with the least disturbed at the top. The highest average blood isolation rates came from the least disturbed areas. The highest monthly maximal rickettsial isolation rates from blood and maximal prevalence rates of antibody per month were also obtained at Bukit Lanjan, the habitat least altered by activities of man. The lowest average blood isolation rate (6%) and the lowest monthly maximal rickettsial isolation and antibody prevalence rates were obtained at Bukit Mandol, the habitat most extensively and intensively altered by man. The intermediate habitats had intermediate rates. We caution anyone interpreting these observations, however, in terms of human disease, which seem to be associated with hyperendemic foci. Here we are not dealing with hyperendemicity from the standpoint of human disease, but present evidence of widespread endemicity from which hyperendemic foci may derive. Also, we have not yet identified the prevalent strains and do not know their infectivity to man.
    Matched MeSH terms: Scrub Typhus/epidemiology*
  8. Scrub typhus: a common cause of illness in indigenous populations
    Brown GW, Robinson DM, Huxsoll DL, Ng TS, Lim KJ
    Trans R Soc Trop Med Hyg, 1976;70(5-6):444-8.
    PMID: 402722
    An explanation was sought for the disparity between the low reported incidence of scrub typhus and the high prevalence of antibody to Rickettsia tsutsugamushi in the rural population of Malaysia. A combination of isolation of the organism, titration of antibody by indirect immunofluorescence, and the Weil-Felix test was used to confirm infections. Scrub typhus was found to be very common, causing 23% of all febrile illnesses at one hospital. The infection was particularly prevalent in oil-palm workers, causing an estimated 400 cases annually in a population of 10,000 people living on one plantation. The clinical syndrome, whether mild or severe, was difficult to distinguish from that due to other infections. Eschars, rashes and adenopathy were uncommon. When used to examine early sera, the Weil-Felix test failed to confirm the diagnosis in most infections.20
    Matched MeSH terms: Scrub Typhus/epidemiology*
  9. Tick-borne pathogens isolated from ticks, rodents, and a shrew in Gangwon and Gyeonggi provinces in the Republic of Korea
    Choi YJ, Kim JY, Kang TU, Park HJ, Kim HC, Lee IY, et al.
    Trop Biomed, 2024 Jun 01;41(2):176-182.
    PMID: 39154270 DOI: 10.47665/tb.41.2.007
    The prevalence of tick-borne pathogens (TBP), Orientia tsutsugamushi, Rickettsia and Borrelia spp. in wild small animals, namely wild rodents, is now widely investigated. This study is to present the prevalence and distribution of O. tsutsugamushi, Rickettsia and Borrelia spp. in wild small animals and ticks collected from Gyeonggi and Gangwon provinces, Republic of Korea (ROK) in 2014. A total of 131 wild small animals, rodents and shrews, and 2,954 ticks were collected from Gyeonggi and Gangwon provinces from May to November 2014. The wild small animals (KR1-9) and ticks (K1-17) were grouped in accordance with capture dates and locations. Among the wild small animals, a total of 393 tissues and blood samples were extracted from six selected small animal series (KR1-3, KR6-8). Also, each date and location-grouped ticks were identified for its species and pooled according to the stage of development. Molecular identification for Rickettsia, Orientia, and Borrelia species was performed using polymerase chain reaction (PCR). To detect TBPs among wild small animals and ticks, primer sets targeting the 56 kDa protein encoding gene of Orientia spp., outer membrane protein B gene (OmpB) of Rickettsia spp., and 5S-23S intergenic spacer region (IGS) gene of Borrelia spp. were used. Of the 393 wild small animals' blood and tissue samples, 199 (50.6%) were positive for Orientia spp., 158 (40.2%) were positive for Borrelia spp., and 55 (14.0%) were positive for Rickettsia spp. Moreover, a total of 14 tick pools (n = 377) was positive for Rickettsia spp. (n=128, 34.0%) and Borrelia spp. (n=33, 8.8%). High prevalence of Orientia spp. and Rickettsia spp. in rodents and shrews were observed. This study presents significant insights by presenting data collected in 2014 that the prevalence of TBP was already high in mid 2010s. This study highlights the sustainable routine surveillance model for TBP.
    Matched MeSH terms: Scrub Typhus/epidemiology
  10. Fulltext Serological evidence of natural infection of wild rodents (Rattus spp and Tupaia glis) with rickettsiae in Malaysia
    Tay ST, Kaewanee S, Ho TM, Rohani MY, Devi S
    Southeast Asian J Trop Med Public Health, 1998 Sep;29(3):560-2.
    PMID: 10437957
    Matched MeSH terms: Scrub Typhus/epidemiology
  11. Effectiveness of a dot-blot immunoassay of anti-Rickettsia tsutsugamushi antibodies for serologic analysis of scrub typhus
    Weddle JR, Chan TC, Thompson K, Paxton H, Kelly DJ, Dasch G, et al.
    Am J Trop Med Hyg, 1995 Jul;53(1):43-6.
    PMID: 7625532
    We compared a commercially available dot-blot immunoassay system with the indirect immunofluorescence assay (IFA) in tests of known negative and known positive sera from scrub typhus cases. Using a panel of 100 sera from patients with various rickettsial and nonrickettsial infections, we observed that the IFA was 99% specific and the dipstick assay was 98% specific. In tests of 91 sera (30 negative and 61 positive for scrub typhus antibodies) from a study of febrile patients in Malaysia, using the standard of an IFA titer < 1:64 as negative, an IFA titer > 1:128 as positive, and an IFA titer = 1:64 as either positive or negative (supported by clinical records), dipsticks were 83% specific and 90% sensitive. The quantitative correlation of the dipsticks to IFA titers was confirmed by significant differences in geometric means of inverse IFA titers corresponding to the number of positive dipstick spots (no dots = 8.5, one dot = 43.3, two dots = 206.7, and three dots = 676.9). The assay would enable physicians and public health workers who deal with patients to quickly diagnose and appropriately treat most cases of the disease, especially in areas of high prevalence where the proportion of false-positive results to true-positive results would be low.
    Matched MeSH terms: Scrub Typhus/epidemiology
  12. Scrub typhus 1980
    Twartz JC
    Ann Acad Med Singap, 1981 Jan;10(1):107-11.
    PMID: 6792975
    Scrub typhus is a widespread and at times serious infection in Asia. If results from central Malaysia can be applied, it appears to be economically important. Diagnosis is often difficult and treatment prone to fail if short courses of antibiotics are used. Prophylaxis is the key area of research with the development of a vaccine being the ultimate goal.
    Matched MeSH terms: Scrub Typhus/epidemiology*
  13. Diagnostic criteria for scrub typhus: probability values for immunofluorescent antibody and Proteus OXK agglutinin titers
    Brown GW, Shirai A, Rogers C, Groves MG
    Am J Trop Med Hyg, 1983 Sep;32(5):1101-7.
    PMID: 6414321
    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.
    Matched MeSH terms: Scrub Typhus/epidemiology
  14. Rickettsia tsutsugamushi antibody in mother/cord pairs of sera
    Shirai A, Brown GW, Gan E, Huxsoll DL, Groves MG
    Jpn. J. Med. Sci. Biol., 1981 Feb;34(1):37-9.
    PMID: 6790744
    Matched MeSH terms: Scrub Typhus/epidemiology
  15. Rickettsial diseases of the Far East: new perspectives
    Rapmund G
    J Infect Dis, 1984 Mar;149(3):330-8.
    PMID: 6425420
    The rickettsial disease of man found only in Asia is mite-borne (scrub) typhus, caused by Rickettsia tsutsugamushi. Unique to southern Japan is a little-known human mononucleosis-like disease caused by Rickettsia sennetsu. In 1981 and 1982, there was a remarkable resurgence in the number of reported cases of mite-borne typhus in Japan after some years of virtual absence. Recent studies of R sennetsu have resulted in its reclassification to the genus Ehrlichia, members of which until now have been exclusively pathogens of animals. The historical background of ecologic investigations, in Malaysia and elsewhere, of these two developments suggest directions for future research.
    Matched MeSH terms: Scrub Typhus/epidemiology
  16. Antigenic types of Orientia tsutsugamushi in Malaysia
    Tay ST, Rohani MY, Ho TM, Devi S
    Southeast Asian J Trop Med Public Health, 2002 Sep;33(3):557-64.
    PMID: 12693591
    The seroprevalence of various Orientia tsutsugamushi (OT) strains among Malaysian patients with suspected scrub typhus infections was determined using an indirect immunoperoxidase (IIP) assay. IgG against a single OT strain were detected in six sera (3 Karp, 1 Gilliam and 2 TC586), whereas IgM antibodies against a single OT strain (Gilliam) were noted in 3 sera (Gilliam). IgG reactive to all OT strains were present in 33 (47.1%) of the 70 sera and IgM reactive to all OT strains were present in 22 (78.6%) of the 28 sera. The fact that most sera were reactive to multiple OT strains suggests that group-specific antigens are involved in scrub typhus infections, whereas very few were due to strain-specific epitopes present on these strains. Peak IgG and IgM titers were noted more frequently against Gilliam, Karp, and TA763 strains: this suggests that these strains may be the commonest infecting strains among Malaysian patients. Two predominant OT polypeptides consistently reacted with patients' sera were the 70 kDa and 56 kDa proteins.
    Matched MeSH terms: Scrub Typhus/epidemiology*
  17. Fulltext Diagnosis of scrub typhus in Malaysian aborigines using nested polymerase chain reaction
    Tay ST, Nazma S, Rohani MY
    Southeast Asian J Trop Med Public Health, 1996 Sep;27(3):580-3.
    PMID: 9185274
    A rapid diagnostic system for scrub typhus using nested polymerase chain reaction (PCR) was applied to clinical samples from Malaysian Aborigines. Whole blood from twenty-four patients suspected of scrub typhus infection were tested using nested polymerase chain reaction and sera were evaluated by the indirect immunoperoxidase test. Antibody responses towards Rickettsia tsutsugamushi were observed in seventeen patients with the majority having high titers of IgG antibodies. Seven patients were seronegative. The nested PCR amplified R. tsutsugamushi DNA from six patients, of which two were negative serologically and four had high titers of IgG antibodies. Second samples collected seven days after treatment were negative by PCR testing. Nested PCR is highly sensitive and specific and may be used to provide rapid confirmation of scrub typhus cases in endemic region.
    Matched MeSH terms: Scrub Typhus/epidemiology
  18. Fulltext Antibody prevalence and factors associated with exposure to Orientia tsutsugamushi in different aboriginal subgroups in West Malaysia
    Tay ST, Mohamed Zan HA, Lim YA, Ngui R
    PLoS Negl Trop Dis, 2013;7(8):e2341.
    PMID: 23936576 DOI: 10.1371/journal.pntd.0002341
    BACKGROUND: Limited data is available on the current status of scrub typhus infection in the aboriginal population in Malaysia. This study was aimed to provide recent data on the degree of exposure of 280 individuals from seven aboriginal subgroups to Orientia tsutsugamushi (causative agent of scrub typhus) in West Malaysia. The environment, socioeconomic and behavioural risk factors associated with the disease were also investigated.

    METHODS/FINDINGS: The antibody prevalence to O. tsutsugamushi ranged from 0 to 36.4% in seven subgroups, with high prevalence rates noted in subgroups involved in agricultural activity and the lowest prevalence rates noted in subgroups whose main occupations were associated to fishing. Univariate analysis indicated populations with age above 18 years (OR = 1.15, 95% CI = 1.02-1.30, P = 0.015), working (OR = 1.99, 95% CI = 1.01-3.92, P = 0.044), working at agriculture area (OR = 1.18, 95% CI = 0.98-1.42, P = 0.031), receiving household income less than US$ 166.7 (RM500) per month (OR = 2.43, 95% CI = 1.16-5.11, P = 0.016) and having close contact with animal pets (OR = 4.06, 95% CI = 1.20-13.76, P = 0.016) are significantly associated with exposure to O. tsutsugamushi. Multivariate analysis confirms that participants who are above 18 years old, receiving household income less than US$ 166.7 (RM500) per month and having close contact with animal pets are 3.6 times (95% CI = 1.81-7.03, P<0.001), 1.3 times (95% CI = 1.14-1.64, P = 0.002) and 1.2 times (95% CI = 1.05-1.06, P = 0.006) more likely to have exposure to O. tsutsugamushi, respectively.

    CONCLUSION: The present study indicates that scrub typhus is still an important disease in the aboriginal population in Malaysia. Awareness about the disease and education on the preventive measures are important in reducing the risk of acquiring scrub typhus in the population studied.

    Matched MeSH terms: Scrub Typhus/epidemiology*
  19. Antibodies to Orientia tsutsugamushi, Rickettsia typhi and spotted fever group rickettsiae among febrile patients in rural areas of Malaysia
    Tay ST, Ho TM, Rohani MY, Devi S
    Trans R Soc Trop Med Hyg, 2000 9 7;94(3):280-4.
    PMID: 10974999
    A serosurvey was conducted in 1995-97 among 1596 febrile patients from 8 health centres in Malaysia for antibodies against Orientia tsutsugamushi (OT), Rickettsia typhi (RT) and TT118 spotted fever group rickettsiae (SFGR) by using an indirect immunoperoxidase assay. A total of 51.4% patients had antibody against at least 1 of those rickettsiae. Antibody to SFGR was most prevalent (42.5%), followed by RT (28.1%) and OT (24.9%). The seroprevalences of antibodies to SFGR, RT or OT alone were 12.4, 3.6 and 4.3%, respectively. Antibodies against more than 1 species of rickettsiae were presence in 31.1% of the patients, suggesting the possibility of co-infection, previous exposures or serological cross-reactivities. Seroprevalence of the various rickettsiae varied according to locality, with SFGR antibodies being the most prevalent in most areas. There was no significant association of prevalence of rickettsial antibody with gender. The seroprevalence of OT, SFGR and RT increased with patient age but an increase of antibody titre with age was not significant. Those working in the agricultural sectors had significantly higher seroprevalence of OT, SFGR and RT than those not related with agricultural activities. Scrub typhus remains a public health problem with an estimated annual attack rate of 18.5%. Tick typhus and murine typhus as shown in this serosurvey appear much more widespread than scrub typhus in this country.
    Matched MeSH terms: Scrub Typhus/epidemiology*
  20. Seroepidemiologic survey of Orientia tsutsugamushi, Rickettsia typhi, and TT118 spotted fever group rickettsiae in rubber estate workers in Malaysia
    Tee TS, Kamalanathan M, Suan KA, Chun SS, Ming HT, Yasin RM, et al.
    Am J Trop Med Hyg, 1999 Jul;61(1):73-7.
    PMID: 10432060
    The seroprevalence of Orientia tsutsugamushi, Rickettsia typhi, and TT118 spotted fever group (SFG) rickettsiae in 300 rubber estate workers in Slim River, Malaysia was determined in December 1996 and March 1997. In December, which was the wet season, 23.3%, 3.0%, and 57.3% of the population had antibodies detected against the three rickettsiae, respectively. The highest seropositive rate of 40% was detected for single infection with SFG rickettsiae, followed by a rate of 15.3% for both O. tsutsugamushi and SFG rickettsiae among the rubber estate workers. Subjects less than 21 years old had a lower seroprevalence of SFG rickettsiae compared with the other age groups. Indians had a higher seroprevalence of O. tsutsugamushi compared with other ethnic groups. Rubber tappers had a higher seroprevalence of SFG rickettsiae compared with other occupational groups. During the dry season in March 1997, there was a significant increase in the seroprevalence of R. typhi. The seroconversion rates for IgM against O. tsutsugamushi, R. typhi, and SFG rickettsiae were 5.7%, 12.3%, and 15.1%, respectively, during the four-month period. Significant variations of antibody titers towards the three rickettsiae was noted among subjects who were bled twice. This suggests a significant and continual exposure of rubber estate workers to the three rickettsiae.
    Matched MeSH terms: Scrub Typhus/epidemiology*
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