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Serological evidence for wide distribution of spotted fevers & typhus fever in Tamil Nadu.

Background & objectives: Although the re-emergence of spotted fevers and typhus was documented from southern India a few years ago, there was a paucity of community based data. Therefore a collaborative study was carried out in several districts of Tamil Nadu to understand the distribution of these infections.

Method: Blood (3 ml) was collected from patients presenting to primary health centres (PHCs) with fever >10 days duration in 15 districts of Tamil Nadu during January 2004 to December 2005. Patients negative for malaria, were tested by Weil-Felix test. Clinical data were collected from patients visiting two hospitals.

Results: A total 306 samples were tested in 2004 and 115 (37.5%) had titres of [greater than or equal to] 80 with OX K antigen, suggesting a diagnosis of scrub typhus. During 2005, 964 patients were tested and 89 (9.2 %) were positive for scrub typhus. An additional 44 (4.6%) were positive for other rickettsial illnesses. In both years majority of scrub typhus occurred in individuals above 14 yr of age. Cases increased from August until the earlier part of next year.

Interpretation & conclusion: This community based study from south India involving several districts in Tamil Nadu, showed that scrub typhus and rickettsial illnesses were widely distributed in the State. Measures to increase awareness and also to diagnose and treat this infection in the affected areas are essential.

Key words Spotted fevers--scrub typhus--Weil Felix test


Although the presence of spotted fevers and scrub typhus, vector borne illnesses with high mortality, was documented from Tamil Nadu in southern India a few years ago (1), there are little community based data available from this or any other state in India. Lack of access to reliable testing methods for hospitals functioning at a community level is the main reason. The specific 'gold standard' test, microimmunofluorescence test (2,3) is not available in India. Availability of tests based on ELISA principles is also limited. Therefore, at present, Weil Felix test which utilises antigens prepared from Proteus spp remains the only laboratory test available to investigate these infections occurring in communities in India. Evaluations done in our laboratory showed that this test had a specificity of over 98 per cent and a sensitivity of about 43 per cent (4). In several areas around the world, Weil Felix test has proved useful in documenting the presence of these infections for the first time:.

Based on hospital data, it was evident that this infection is likely to be prevalent in many parts of Tamil Nadu (5). Since there were no data available on the occurrence of these infections in the community, a collaborative study was undertaken by the Institute of Vector Control and Zoonoses, Hosur, and Christian Medical College (CMC), Vellore in several districts of Tamil Nadu to develop preliminary understanding of the distribution of these infections.

Material & Methods

3 ml of blood was collected from patients with fever of more than 10 days duration after obtaining informed consent from 32 health centres in 11 districts of 15 health units of Tamil Nadu during the period January 2004 to December 2005 and sent to Institute of Vector Control and Zoonoses, Hosur. The aim at this stage was only to document wide distribution. No attempt was made to document actual magnitude, due to logistical reasons. Blood samples were therefore collected from as many patients as possible. Serum samples of those patients who were smear negative for malaria were tested by Weil--Felix test at this centre. Antigen was prepared using standard protocol developed at CMC, Vellore (6). Titres of 80 or more were considered to indicate either spotted fever or scrub typhus (4). Clinical data were collected from patients visiting Government Pentland Hospital Vellore and the Primary Health Centre at Usoor.

Results & Disussion

A total 306 samples were tested in the year 2004 and 115 (37.6%) had titres of 80 or above with OX K antigen, suggesting a diagnosis of scrub typhus and four others had titres indicating other rickettsial illnesses. During 2005, 964 patients were tested and 89 (9.2%) were positive for scrub typhus. An additional 44 (4.6 %) were positive for other rickettsial illnesses (Table). In the year 2004, 80 of the 115 patients with scrub typhus (69.6%) were males while only 48 (53.9%) of the 89 patients were males in 2005. Among those affected with scrub typhus, during the two years under study, 102 (88.7%) and 85 (95.5%) respectively were above 14 yrs. All individuals with other rickettsial illnesses were above 14 yrs and 23 (52.3%) were men. The number of cases increased from August and continued to be high in the earlier part of next year. Very few cases were recorded during May, June and July in both years. Clinical feature could be recorded only for 48 and 32 cases respectively presenting to out patients clinics of Vellore Government Pentland Hospital and Usoor PHC. Head ache and myalgia were the most common manifestations along with fever and were observed in 45 (93.8%) and 23 (71.9%) cases respectively. Although 22 (27.5%) of individuals had rash, none had eschar. Conjunctival suffusion was present in 20 (25%).

Serological data collected during two consecutive years show that scrub typhus and rickettsial illnesses are widely distributed in Tamil Nadu. This is probably the first community based study from India where data was collected from different districts in one state. Most reports from Tamil Nadu so far, are based on data from one tertiary level referral hospital (1,4,5).

The prevalence rates could not be assessed, since all cases with fever occurring in the area could not be tested because of logistical reasons. However, it is clear that, patients with scrub typhus and other types of rickettsial illnesses present to primary health care facilities. Therefore public health interventions and measures to increase awareness among doctors and general public are required to control and treat these infections. The numbers of cases identified increased during the cooler months following rains as described earlier (5).

These infections respond well to antimicrobials like doxycycline and chloramphenicol (2). However, mortality can be high if untreated (3). The mortality rate in a tertiary care hospital, where patients from this state are referred when complications develop, was found to be about 15 per cent (5).

Since manifestations are varied laboratory tests are required for diagnosis. Weil Felix test, though easy to perform, lacks sensitivity (4). The test becomes positive only after about two weeks after onset of illness and so cannot be relied upon to initiate therapy. Specificity of this test is however high and therefore can be used to identify new areas where rickettsial infections are prevalent.

In conclusion, it is possible that more areas in the country harbour these infections. Large scale studies in different parts of the country need to be undertaken to understand the magnitude of this infection in India.

Received July 18, 2006


(1.) Mathai E, Lloyd G, Cherian T, Abraham OC, Cherian AM. Serological evidence for the continued presence of human rickettsioses in southern India. Ann Trop Med Parasitol 2001; 95: 395-8.

(2.) Parola P, Paddock CD, Raoult D. Tick-borne rickettsioses around the world: emerging diseases challenging old concepts. Clin Microbiol Rev 2005; 18: 719-56.

(3.) Watt G, Parola P. Scrub typhus and tropical rickettsioses. Curr Opin Infect Dis 2003; 16: 429-36.

(4.) Prakash JA, Abraham OC, Mathai E. Evaluation of tests for serological diagnosis of scrub typhus. Trop Doct 2006; 36: 212-3.

(5.) Mathai E, Rolain JM, Verghese GM, Abraham OC, Mathai D, Mathai M, et al. Outbreak of scrub typhus in southern India during the cooler months. Ann N YAcad Sci 2003; 990 : 359-64.

(6.) Mathai E, Selwyn J, Serology/immunology. In: Myer's and Koshi's manual of diagnostic procedures in medical microbiology and immunology/serology. Vellore: Christian Medical College and Hospital; 2000 p. 137-62.

Reprint requests: Dr Elizabeth Mathai, Professor & Head, Department of Clinical Microbiology, Christian Medical College, Town Campus, Vellore 632004, India e-mail:

K. Kamarasu, M. Malathi, V. Rajagopal *, K. Subramani, D. Jagadeeshramasamy ** & Elizabeth Mathai (+)

Institute of Vector Control & Zoonoses, Hosur, * Zonal Entomological Team, Vellore, ** Directorate of Public Health & Preventive Medicine, Chennai & (+) Department of Microbiology, Christian Medical College, Vellore, India
Table. Health Unit Districts (HUD) wise distribution
of cases in the years 2004 and 2005

 2004 2005

Name of the
Health Unit No. No. No. No.
Districts (HUD) tested positive tested positive

Vellore 220 91 475 66
Thiruppathur 16 6 95 15
Thirvannamalai 1 0 133 8
Cheyyar 29 13 167 34
Perambalur 16 0 0 0
Erode 1 1 6 0
Coimbatore 22 7 14 6
Udhagamandalam 1 1 23 2
Thiruvallur NT NT 6 2
Dharapuram NT NT 5 0
Kanchipuram NT NT 1 0
Dindigul NT NT 5 0
Trichy NT NT 30 0
Tirupur NT NT 2 0
Madurai NT NT 2 0
Total 306 119 964 133

NT - Not tested
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Article Details
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Author:Kamarasu, K.; Malathi, M.; Rajagopal, V.; Subramani, K.; Jagadeeshramasamy, D.; Mathai, Elizabeth
Publication:Indian Journal of Medical Research
Article Type:Clinical report
Geographic Code:9INDI
Date:Aug 1, 2007
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