Leptospira interrogans serovar Valbuzzi: a cause of severe pulmonary haemorrhages in the Andaman Islands

Outbreaks of leptospirosis that present with predominant pulmonary signs and symptoms have been occurring in the Andaman Islands since the late 1980s. Before this, pulmonary haemorrhage had not been observed as a common complication of leptospirosis in India. During an outbreak on North Andaman in 1997, four leptospire isolates were obtained from blood of a fatal case and three other patients who recovered. These isolates were characterized using serological and molecular techniques. Cross-agglutination absorption tests and microscopic agglutination tests using mAbs were used for serological characterization. Genetic typing was done using DNA sequencing of PCR products. Serologically, the isolates were closely related to strain Valbuzzi serovar Valbuzzi of serogroup Grippotyphosa. The sequences of PCR products from these isolates were compared with those of 45 strains belonging to seven species. The isolates showed 97.5-100 % sequence similarity to reference strains belonging to Leptospira interrogans, indicating that the isolates belong to L. interrogans. Serogroups Icterohaemorrhagiae and Australis have been incriminated as the cause of pulmonary haemorrhage in China, Korea and Australia. The four isolates characterized in the present study were obtained from patients with similar symptoms. However, they belonged to serovar Valbuzzi of serogroup Grippotyphosa, indicating that serogroups other than Icterohaemorrhagiae and Australis can also cause pulmonary haemorrhage.

Antigenic and genetic relatedness of Leptospira strains isolated from the Andaman Islands in 1929 and 2001

Leptospirosis is a major public health problem in Andaman Islands. Several strains of Leptospira have been isolated from the Andamans over the years. Leptospires isolated recently from human cases were compared with one of the earliest available isolates from these islands, dating back to 1929, to study their serological and genetic relatedness. Randomly amplified polymorphic DNA (RAPD) fingerprints of the isolates, generated with a primer used previously to differentiate between Leptospira species and serovars, revealed that some of the recent isolates were genetically identical to the 1929 isolate. The antigenic properties of these strains, as revealed by microscopic agglutination tests with group-specific rabbit antisera and mAbs, were also similar. These findings suggest that a Leptospira strain originally isolated in 1929 has possibly persisted in these islands for over 70 years and continues to cause acute leptospirosis in humans.

Field application of Lepto lateral flow for rapid diagnosis of leptospirosis

The Lepto lateral flow assay for leptospirosis was evaluated at a primary health centre in the Andaman Islands, where leptospirosis is endemic. One hundred and seventeen suspected patients were included in the study; acute serum samples were collected from all of them and convalescent samples from 104. The standard criteria for diagnosis of leptospirosis were: (i) isolation of leptospires from blood, (ii) seroconversion in microscopic agglutination test (MAT) with a minimum titre of 100, (iii) a fourfold rise in titre in MAT or (iv) a MAT titre of 400 or more if only a single sample was available. The results of the lateral flow test were compared with these criteria. Lepto lateral flow had sensitivity of 52.9 % (37/70) in the first week of illness and 86 % (49/57) during weeks 2-4. The corresponding specificities were respectively 93.6 % (44/47) and 89.4 % (42/47). The sensitivity was 34.3 % (12/35) on days 2-3 of the illness, 63.3 % (14/22) on days 4-5 and 84.6 % (11/13) at the end of the first week. The test had a positive predictive value of 92.5 % (37/40) during the first week and 90.7 % (49/54) subsequently. Corresponding negative predictive values were respectively 57.1 % (44/77) and 84 % (42/50). Agreement of the results with the standard criteria was low during the first week, but high during weeks 2-4, with a kappa value of 0.7491. The positivity rates of the tests showed a logarithmic relationship with the MAT titres of samples (r(2) = 0.9271). All indices of validity and utility of lateral flow were similar to those of IgM ELISA and Lepto dipstick. The test can be performed at the bedside of the patient, as whole blood can also be used for testing.

Leptospirosis disease burden estimation and surveillance networking in India

Although leptospirosis is known to have occurred in India since the early years of the 20th century, no accurate data on disease burden exist. During the past two decades, leptospirosis cases have been reported with increasing frequency from different parts of the country. Several large outbreaks have occurred. In the year 2000, the Indian Council of Medical Research set up a Task Force on Leptospirosis. The Task Force conducted a multicentric study on disease burden due to leptospirosis. As part of the study, 3,682 patients with acute febrile illness, from 13 different centers in India, were investigated for the presence of current leptospiral infection using the Lepto-dipstick test. Of these patients, 469 (12.7%) were found to have leptospiral infection. The positivity rate ranged from 3.27% in the central zone to 28.16% in the southern zone. Fever, body aches and chills were the common symptoms observed. Urinary abnormalities, such as oliguria, yellow discoloration of urine and hematuria were found in 20%-40% of patients. Distribution of serogroups was studied based on microscopic agglutination test (MAT) titers. The southern zone had all the eleven serogroups in the panel, the eastern zone had nine, the northern zone eight, and the central and western zones had five circulating serogroups each. Among various risk factors studied, rat infestation of houses had the strongest association with leptospiral infection. Many other factors related to the environment, personal and occupational habits, etc, also had significant associations. The study had a few drawbacks. The Task Force has decided to continue the study with modified protocols to generate more accurate and detailed information about disease burden.

Molecular tools in leptospirosis diagnosis and characterization of isolates

The incidence of leptospirosis in human beings has been increasing in recent years. Early diagnosis and treatment can prevent complications and reduce mortality. The conventional laboratory methods for diagnosis rely on the demonstration of leptospires in clinical specimens, recovering the organisms in culture or the demonstration of antibodies to leptospires. Demonstration techniques have low sensitivity and specificity. Leptospires grow slowly and the positivity rate in culture is very low. Although microscopic agglutination test has been the cornerstone of serological diagnosis, the procedure is complex. New tests, like ELISA, dipstick test, lateral flow, etc, are relatively simple and rapid, but sensitivity is low during the early stages of the disease. The cross agglutination absorption test (CAAT) and typing with monoclonal antibodies (MCA) are the techniques used for serological characterization. These techniques are complicated and might not help in the case of certain serogroups. An alternate method for early diagnosis and characterization focuses on DNA-based techniques. Polymerase chain reaction (PCR), in situ hybridization etc are some of the methods used for early diagnosis, whereas restriction endonuclease analysis (REA), random amplified polymorphic DNA (RAPD) fingerprinting, arbitrarily primed PCR (AP-PCR), pulsed field gel electrophoresis (PFGE), ribotyping and DNA sequencing are useful for characterization. PCR is the most popular and quickest method for diagnosis. It can detect even if only a small number of organisms are present in a clinical sample. Fingerprinting tools such as RAPD, REA, RFLP, PFGE etc translate the complex genetic code into easily recognizable patterns, which facilitates characterization of the isolates up to sub-serovar level.

Evaluation of Lepto Dri Dot as a rapid test for the diagnosis of leptospirosis

Lepto Dri Dot is a new card agglutination test developed by the Dutch Royal Tropical Institute for the rapid diagnosis of leptospirosis. We evaluated the test in field conditions in The Andaman Islands. Patients suspected of leptospirosis who attended three primary health centres were included in the study. The test results were compared with blood culture or microscopic agglutination tests on paired serum samples; 74 of 124 patients were diagnosed as having leptospirosis based on these criteria. Lepto Dri Dot had a sensitivity of 67.6% (50/74) and a specificity of 66.0% (33/50) during week 1. During weeks 2-4 the values increased to 85.5% (47/55) and 80% (40/50) respectively. An IgM ELISA was also performed on the serum samples for comparison and this was marginally less sensitive, but more specific, during the first week of illness. The positivity rates for the Dri Dot test during days 2-3, 4-5 and 6-7 were 53.1% (17/32), 75.0% (18/24) and 83.3% (15/18), respectively. The corresponding values for ELISA were 28.1% (9/32), 54% (13/24) and 77.8% (14/18). Both Dri Dot and ELISA showed good agreement with the standard diagnostic criteria after the first week of illness (kappa= 0.65 and 0.74, respectively). The overall concordance of the two tests was 89.5 % (kappa = 0.79). The test does not require special storage or sophisticated equipment and can be performed by relatively low skilled personnel.

Outbreak of leptospirosis after the cyclone in Orissa

BACKGROUND

Two weeks after the cyclone during October-November 1999, several persons in Orissa suffered from a febrile illness with haemorrhagic manifestations. Serum samples from a few such patients tested positive for anti-leptospiral IgM antibodies. We conducted a study in four villages that were flooded after the cyclone to examine the possibility of leptospirosis being the cause of the outbreak.

METHODS

One hundred forty-two persons living in four flooded villages in the Jaipur district of Orissa were interviewed for their disease history and possible risk factors after the cyclone. Blood samples were collected and tested for anti-leptospiral antibodies using the microscopic agglutination test, IgM ELISA and lepto-dipstick. Follow up samples were collected from those who had inconclusive results on the first test and the microscopic agglutination test was repeated on these samples.

RESULTS

Eighty-four of the 142 study subjects had suffered a febrile illness and 40 of them had positive results in one or more IgM-based tests and 28 had a positive microscopic agglutination test result as well. Thus, 19.2% of the study subjects (28/142) had serological evidence of symptomatic leptospiral infection after the cyclone. Also, 8.5% of the subjects had low levels of antibodies indicative of the level of background seroprevalence.

CONCLUSIONS

The results indicate that there was an outbreak of leptospirosis in the flooded villages and the attack rate was high. A carrier state might have existed in the animal population and the cyclone and floods changed the environment drastically making it conducive for transmission of infection. Large numbers of persons were continuously exposed to flood waters and this resulted in the outbreak.

Evaluation of microscopic agglutination test as a diagnostic tool during acute stage of leptospirosis in high & low endemic areas

BACKGROUND & OBJECTIVES

Making a diagnosis on the results of a single microscopic agglutination test (MAT) is difficult because of the uncertainties about the cut-off titre. The present study was conducted to determine the significant titre for a single MAT in areas of high and low endemicity for leptospirosis.

METHODS

A total of 1944 serum samples were collected from healthy individuals and confirmed patients residing in areas of high and low endemicity. All the sera were screened by MAT using 10 live leptospiral strains as antigens. From the distribution of titres among healthy individuals and in patients, the sensitivity and specificity at different cut-off titres were calculated. Likelihood ratio positive (LR+), likelihood ratio negative (LR-), and LR+/LR- were calculated. Receiver operating characteristics (ROC) curves were plotted for the early and late stages of the disease in both the areas.

RESULTS

The ROC plot was totally below the no benefit line during the first week of illness in high endemic area. During the second to fourth weeks it showed better characteristics and the best cut-off titre was 1:200, where the sensitivity was 93.4 per cent and specificity 74.7 per cent LR+ LR- ratio was 41.82 indicating reasonable separation between the positive and negative test results. In the other states the ROC plot was above the no benefit line even during the first week, the best cut-off being 1:50 where the sensitivity was 56.7 per cent and specificity was 90.6 per cent. During the second to fourth weeks the test showed the best characteristics in the low endemicity regions with an ROC curve having the ideal shape. Best cut-off was at 1:100 where the sensitivity was 96.6 per cent and specificity 94.8 per cent LR+ LR- ratio was 523.25 indicating a wide separation between the positive and negative test results.

INTERPRETATION & CONCLUSION

MAT does not have any diagnostic value during the first week, particularly in high endemic areas. The best cut-off to be used will be 1:50 in low endemicity areas during the first week, 1:100 during the second to fourth week and 1:200 in high endemicity regions during the second to fourth weeks.

Evaluation of darkground microscopy as a rapid diagnostic procedure in leptospirosis

BACKGROUND & OBJECTIVES

Although darkground microscopy (DGM) is the method employed for examining the growth of leptospires in culture, it is not useful for diagnosis when used directly on body fluids. However, it continues to be used as a method for diagnosing leptospirosis in many centres in India. The present study was undertaken to evaluate the diagnostic accuracy of DGM by comparing it with established tests like culture, microscopic agglutination test (MAT), IgM ELISA and Lepto-Dipstick.

METHODS

A total of 170 patients clinically suspected to have leptospirosis were included in the study. The gold standard for diagnosis was positive blood culture, or seroconversion, or a four-fold rise in titre in MAT. DGM was done on plasma after centrifugation at 1000 g and 3000 g and on serum. Indices of accuracy including sensitivity, specificity, predictive values and kappa value of agreement with the gold standard diagnostic criteria were calculated.

RESULTS

DGM had a sensitivity of 40.2 per cent, specificity of 61.5 per cent, a positive predictive value of 55.2 per cent and a negative predictive value of 46.6 per cent. It had agreement with the gold standard in only 50 per cent cases the kappa value being 0.017141.

INTERPRETATION & CONCLUSION

DGM has low indices of accuracy. The results obtained in patients who met the gold standard criteria for diagnosis and those who did not were identical indicating that the test results are not determined by the presence of leptospiral infection in the patient. DGM, therefore, is not recommended as a sole diagnostic procedure for early diagnosis of leptospirosis.

Lai-like leptospira from the Andaman Islands

BACKGROUND & OBJECTIVES

Leptospirosis has been an important public health problem in the Andaman Islands since 1988. As information about the exact etiological agent is not available, the present study was undertaken to isolate and identify Leptospira from human patients.

METHODS

An isolate coded AF61 was recovered from the blood of a patient clinically suspected to have leptospirosis, with fever, headache and body aches as the main symptoms. The isolation was done using Ellinghausen-McCullough-Johnson-Harris (EMJH) medium following standard procedure. The isolate was identified using microscopic agglutination test (MAT) with 'groupsera', cross agglutination absorption test (CAAT) and monoclonal antibodies.

RESULTS

Agglutination tests with rabbit antisera revealed that the isolate belonged to the serogroup icterohaemorrhagiae. The CAAT results showed that it was closely related to the serovar lai. Analysis of AF61 with monoclonal antibodies confirms our observation with CAAT that it is closely related to the reference strain Lai serovar lai.

INTERPRETATION & CONCLUSIONS

Serovar lai, has been associated with pulmonary haemorrhage in China and Korea. However, the strain AF61 was not isolated from a patient with pulmonary symptoms. Further studies are needed to understand the possible relationship between serovars and clinical patterns and the distribution of serovar lai and lai-like strains in Asia.

Randomized controlled trial of doxycycline prophylaxis against leptospirosis in an endemic area

Leptospirosis occurs as seasonal outbreaks, lasting for about 3 weeks during October-November in North Andaman. A randomized controlled trial was undertaken to assess the efficacy of doxycycline prophylaxis in the prevention of infection and clinical disease due to leptospires during the outbreak period. A sample population of 782 persons, randomized into two groups was given doxycycline 200 mg/week and a placebo. The microscopic agglutination test was done on blood samples collected on day zero, after 6 weeks and after 12 weeks. Infection rates and attack rates of clinical illness were calculated in the two groups based on the serological results. Statistically there was no difference in the infection rates among the two groups. However, a statistically significant difference was observed in the clinical disease attack rates (3.11 vs. 6.82%) between study group and control group. The results of the study indicate that doxycycline prophylaxis does not prevent leptospiral infection in an endemic area, but has a significant protective effect in reducing the morbidity and mortality during outbreaks.

Leptospiral infection among primitive tribes of Andaman and Nicobar Islands

The Andaman islands were known to be endemic for leptospirosis during the early part of the century. Later, for about six decades no information about the status of the disease in these islands was available. In the late 1980s leptospirosis reappeared among the settler population and several outbreaks have been reported with high case fatality rates. Besides settlers, these islands are the home of six primitive tribes of which two are still hostile. These tribes have ample exposure to environment conducive for transmission of leptospirosis. Since no information about the level of endemicity of the disease among the tribes is available, a seroprevalence study was carried out among all the accessible tribes of the islands. A total of 1557 serum samples from four of the tribes were collected and examined for presence of antileptospiral antibodies using Microscopic Agglutination Test (MAT) employing 10 serogroups as antigens. An overall seropositivity rate of 191% was observed with the highest rate of 53.5% among the Shompens. The seropositivity rates in the other tribes were 16.4% among Nicobarese, 222% among the Onges and 14.8% among the Great Andamanese. All of the tribes except the Onges showed a similar pattern of change in the seroprevalence rates with age. The prevalence rates were rising from low values among children to reach a peak in those aged 2140 years and then declined. Among Onges the seroprevalence rates continued to rise beyond 40 years. In all the tribes, seroprevalence rates were found to be significantly higher among the males. The commonest serogroups encountered were Australis followed by Grippotyphosa, Icterohaemorrhagiae, Pomona and Canicola.

LEPTO Dipstick: a rapid and simple method for serodiagnosis of acute leptospirosis

The LEPTO Dipstick assay is a newly developed test for the diagnosis of leptospirosis and uses a broadly reactive antigen for detecting IgM antibodies. The test was evaluated in the Andaman and Nicobar Islands, using 867 serum samples from known cases of leptospirosis and controls. The efficacy of IgM ELISA was also tested for comparison. The LEPTO Dipstick had a sensitivity of 78.7%, a specificity of 88.3% and a positive predictive value of 91.0%. The test had a good level of agreement with the standard criteria for diagnosis using paired microscopic agglutination tests (kappa = 0.64). These indices were similar to those of IgM ELISA (sensitivity 78.5%, specificity 87.6%, positive predictive value 90.5%, kappa 0.63). Both the LEPTO Dipstick and IgM ELISA had the highest sensitivity during the second, third and fourth weeks of illness (87.6% and 88.2%, respectively). Sensitivities during the first week and after 4 weeks were relatively low but acceptable. The test is very easy to perform and does not require any special skills for its performance. The reagents and dipsticks have a long shelf-life even at room temperature. As the test can be performed without the aid of sophisticated equipment, it is suitable for use at the peripheral level as a rapid screening test for the diagnosis of leptospirosis.

Clinico-epidemiological study of hospitalized cases of severe leptospirosis

In an attempt to understand the clinical spectrum and pathological and biochemical abnormalities and their prognostic importance in leptospirosis, a prospective study was carried out in Port Blair during September 1996 to August 1997. Out of 80 patients suspected to have leptospirosis, 58 were proved to have current leptospiral infection using serological tests and among these, 14 died giving a case fatality rate of 24.1 per cent. The incidence of the disease showed two separate peaks roughly coinciding with the paddy sowing and harvesting season and the majority of the patients had history of exposure to wet and water logged environment prior to the attack of the disease. The disease presented as two separate clinical syndromes--the hepato-renal form and the pulmonary form though some degree of overlap was present. Hepatic and renal complications occurred in 30 patients each with 26 of them having both. These generally occurred late in the course of the disease and the mortality rate was relatively low. In contrast pulmonary complication occurred quite early and the case fatality rate in those patients was very high (6.7% vs 42.9%). The other complications encountered in the current series of cases were refractory hypotension probably due to myocarditis in 40 per cent and neck stiffness and altered sensorium due to central nervous involvement in 12.1 per cent of the patients. The chances of the patients developing complications were considerably low if treated early and very few of them developed any complications after 2 days of hospitalized treatment. The early occurrence of pulmonary complications indicates a pathogenesis totally different from that responsible for the other complications.

Risk factors in the transmission of leptospiral infection

An unmatched case control study was conducted to study the various risk factors for acquiring leptospiral infection in Diglipur tehsil of North Andaman. A random sample of 1014 persons residing in various villages of Diglipur was inducted into the study. Serum samples were collected from them and tested for anti-leptospiral antibodies using microscopic agglutination test (MAT) using Leptospira grippotyphosa, L. australis, L. canicola and L. icterohaemorrhagiae antigens. Persons with a titre of 1:50 or more were considered as the cases (550) and the seronegatives as controls (464). Information about 30 variables relating to household characteristics, occupation, contact with animals and behavioural factors was collected by interviewing the subjects. The prevalences of these variables in both the groups were calculated and the odds ratio with 95 per cent confidence intervals were computed. The seroprevalence rate was found to increase linearly with age and it was significantly higher in males. None of the risk factors studied had any association with seropositivity to serovar L. icterohaemorrhagiae. For the other serovars, some form of recent exposure to outdoor environment had significant association. Other factors which had association with infection with specific serovars included use of well or stream water and presence of dogs in the house for infection with L. grippotyphosa, farming families and presence of cattle in the houses for infection with L. australis and the habit of bathing in ponds for infection with L. canicola. These observed associations can be taken as clues of the transmission cycles and would help in guiding further investigations for understanding the epidemiology of leptospirosis in these islands.

Evaluation of leptospira micro capsule agglutination test (MCAT) for serodiagnosis of leptospirosis

A micro capsule agglutination test (MCAT) was evaluated for its usefulness in the diagnosis of leptospirosis. The test was performed on 180 serum samples from 120 patients suspected to have leptospirosis and the results were compared with those obtained by microscopic agglutination test (MAT). The overall sensitivity and specificity of the test in comparison with MAT were 84.7 and 87.0 per cent respectively. Further, to study the relative merits of MCAT and MAT in diagnosing leptospirosis early in the course of the disease, its sensitivity and specificity during the early stages of the disease were compared with those of a single MAT done on acute samples in 60 patients from whom paired samples were available. The test appeared to have a higher sensitivity than MAT during the early stages of the disease (75% vs 58.3%) though the specificity was less than that of MAT (83.3% vs 100%). The sensitivity of the test declined to 61 per cent three to four weeks after the onset of illness. MCAT detected antibodies against serogroups Australis (76.9%), Autumnalis (100%) Ballum (100%), Canicola (100%), Cynopteri (100%), Grippotyphosa (71.8%), Icterohaemorrhagiae (93.3%), Javanica (100%), Pomona (75%) and Pyrogenes (100%). MCAT appears to be a useful screening test for early diagnosis of leptospirosis. It is a simple and easy to read test which does not require any special expertise or equipment.