Prevalence of scrub typhus among acute undifferentiated febrile illness cases provisionally diagnosed as dengue fever.
MATERIAL AND METHODS:
STUDY DESIGN: Prospective Descriptive hospital based pilot Study. The study was approved by the institutional ethical committee.
One hundred febrile patients admitted in medical and paediatric wards of Gandhi hospital during October 2011-November 2011 were included in this study.
INCLUSION CRITERIA WERE : patients of all age groups, having temperature >38.5C for >24 hrs and clinically diagnosed as having dengue fever. Exclusion criteria were : febrile cases with definite source of infection, history of bleeding tendency since birth and immunocompromised patients. I Consent was obtained. Information on demographic features and symptoms of the patients were collected by a structured questionnaire. A detailed physical examination and tourniquet test was done. Single serum samples collected from all these patients within 48hours of admission was subjected to the following serological assays--dengue NS1 antigen ELISA(Panbio), dengue IgM ELISA((NIV Pune), dengue IgG ELISA (Novatech), chikungunya IgM antibodies MAC- ELISA(Panbio), Widal tube agglutination test(Span diagnostics), Leptospira IgM antibodies ELISA (Panbio), Plasmodium falciparum, Plasmodium vivax antigen Parahit FandV(Span diagnostics), Weil Felix tube agglutination test(Tulip diagnostics), Orientia Tsutsugamushi IgM and IgG antibodies Rapid monochrome autographic test (SD bioline). All the tests were performed according to manufacturer's instructions. In Widal test "O "antibody titre of >1 1: 80 and "H "antibody titre of >1: 160 were considered positive. Other laboratory investigations included haemoglobin, total and differential leukocyte count, platelet count and liver transaminases. Statistical analysis was done by chi square test. P value <0.05 is considered significant.
RESULTS: Table 1 shows the serological profile of acute febrile illness patients. Thirty nine patients were positive for dengue NS1Ag and/or dengue IgM antibodies.19 samples were positive for scrub typhus by rapid immunochromatography.14 samples showed a titre of > 320 and 5 samples showed a titre of 80 to 160 by Weil Felix test.
Table 2 shows the clinical and laboratory differentiating features between dengue fever and scrub typhus.
Scrub typhus was more common in older age group (mean age-36.2yr) compared to dengue fever( mean age--20.8yr).
Tourniquet test and signs and symptoms suggestive of platelet dysfunction were common in dengue fever whereas these findings were uncommon in cases with scrub typhus.
DISCUSSION: Most of the acute fevers presenting with rash are presumptively diagnosed as dengue fever, especially during monsoon and post monsoon months in tropical countries like India. However only up to one third of the cases are confirmed as dengue. In our study even after including NS1 antigen test, dengue fever contributed to 39% whereas other infections contributed to 40% of cases. similar observations were done by other workers. 
In India, the presence of scrub typhus has been known for several decades. During world war II scrub typhus produced considerable mortality and morbidity among troops deployed in South East Asia. However in later years the disease virtually disappeared, probably because of wide spread use of insecticides to control other vector borne diseases. Recent reports from several parts of country including South India indicate that there is a re- emergence of scrub typhus. 
Diagnosis of scrub typhus is most often confirmed by serological testing. Specific gold standard tests like Immunofluorescence antibody test (IFA), Immunoperoxidase test (IP), ELISA and isolation are not available in our country. Many reports from Indian subcontinent are based on clinical findings and nonspecific Weil Felix test  Criteria suggested for diagnosis of scrub typhus is a single titer of 1:320 or four fold rise in antibody titer rising from 1:80. in weil Felix test. In our study antibody titer was 1:320 in 14 cases (73.7%) and low titer of 1:80-1:160 were detected in 5 cases. Rising antibody titer could not be demonstrated as we could not collect the convalescent sera. These samples tested positive with the immuno chromatography which employed a 56KDA recombinant protein specific for O. Tsusugamushi for detection of IgM and IgG antibodies with a reported sensitivity of 97% and specificity of 100% . Hence these samples were also considered positive for scrub typhus antibodies. Further none of these samples were positive for other serological tests performed.
Most cases of scrub typhus were from rural background. Tourniquet test, signs and symptoms suggestive of platelet dysfunction were common in dengue fever in contrast to scrub typhus. These features can be useful in clinical diagnosis in differentiating between dengue fever and scrub typhus and initiation of specific antibiotic therapy for scrub typhus which will reduce the morbidity and mortality. Similar observation was made by other workers .
In our study Scrub typhus contributed to 19% of the acute fevers. To the best of our knowledge except for a case report., there are no reports on the prevalence of scrub typhus in Andhra Pradesh . This study emphasizes the need for the general awareness of rickettsial infections in Andhra Pradesh. Diagnostic tests such as ELISA using 56 KDA antigens specific for Orientia Tsutsugamushi can provide a cost effective alternative diagnostic tool. More research is essential regarding the epidemiology, pathogenesis and lab diagnosis of diseases in Indian context particularly in Andhra Pradesh.
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Nagamani Kammili, A. Swathi, Sudha Madhuri Devara, P.R. Anuradha
(1.) Professor. Department of Microbiology, Gandhi Medical College. Secunderabad.
(2.) Post Graduate. Department of Microbiology, Gandhi Medical College. Secunderabad.
(3.) Assistant Professor. Department of Microbiology, Gandhi Medical College. Secunderabad.
(4.) Professor & Head of the department. Department of Microbiology, Gandhi Medical College. Secunderabad.
Dr. Nagamani Kammili, Professor, Dept. of Microbiology, Gandhi Medical College, Secunderabad.
TABLE 1 Serological profile of acute febrile illness patients (n=100) Serological test no of cases positive(%) Dengue NS1 Ag 5(5) Dengue IgM Antibody 28(28) Dengue NS1 Ag+ IgM Ab 6(6) WeiL Felix tube agglutination 14(14) test titre >1:320 + Positive ICT for O. Tsusugamushi WEIL FELIX tube agglutination test titre 1: 5(5) 80 to 1: 160 + Positive ICT for O. Tsusugamushi Leptospira IgM 9(9) Leptospira IgM+ dengueIgM 3(3) chikungunya IgM 4(4) chikungunyaIgM+ dengueIgM 1(1) malaria antigen 7(7) malariaAg+ dengueIgM 2(2) Widal test 1(1) TABLE 2 Clinical and laboratory differentiating features between dengue fever and scrub typhus. Dengue Scrub P value fever(N=39) typhus(N=19) Rural 15(38.4%) 15(78.9%) <0.05 Urban 19(48.7%) 04(21%) <0.05 Male: female ratio 1.3:1 1:1.2 >0.05 Mean age 20.8YR 36.2YR -- Mean hospital stay 1WEEK 1WEEK -- Mean duration 4.6 days 3.1days >0.05 of fever at the time of admission Rash 06(15.3%) 03(15.7%) >0.05 Arthralgia 18(46.1%) 03(15.7%) <0.05 Haemorrhagic 24(61.5%) 02(10.5%) <0.05 manifestations Positive 11 (28.2%) <0.05 tourniquet test Altered liver 22(56.4%) 02(10.5%) <0.05 function tests Thrombocytopenia 28(71.7%) 12(63.1%) >0.05
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|Title Annotation:||BRIEF COMMUNICATION|
|Author:||Kammili, Nagamani; Swathi, A.; Devara, Sudha Madhuri; Anuradha, P.R.|
|Publication:||Journal of Evolution of Medical and Dental Sciences|
|Date:||Apr 22, 2013|
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