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Seroprevalence of Leptospirosis among Jarwas-a Hunter-gatherer Primitive Negrito Tribe of Andaman and Nicobar Islands, India
Abstract
The Jarwa, one of the four Negrito tribes of these islands, inhabit the west coast of the South and Middle Andamans district have been living in isolation for several centuries and recently they started coming out of the jungles shedding their hostility. Since than several disease outbreaks have been reported in these classical tribe. An attempt was made to screen the sera collected during one such outbreaks showed the prevalence of leptospirosis in these tribes. MAT, IgM and IgG ELISA were used for the detection of Leptospiral antibodies among Jarwas samples. Among 40 sera samples collected during a febrile out break, 40% of the samples showed antibodies against leptospirosis by MAT. Icterohaemorrhagiae was the major serogroup for the cause of leptospirosis among Jarwas and was followed by Hebdomadis and Pyrogenes. The highest titre observed was 1:320 against serogroup Icterohaemorrhagiae. IgM ELISA showed a seroprevalence rate of 20% where as IgG ELISA showed a prevalence of 63%. The highest titre observed for I gM ELISA was 1:320 and for IgG it was 1:160. The environment of the jungle where they live in is favorable for survival of leptospirosis and their association with domestic and wild animal has to be studied which could be one of the source for acquiring leptospiral infection.
... In this study, longer duration of employment was associated with contracting leptospirosis; this might be due to prolonged exposure. The magnitude of high-risk occupation and prolonged exposure to possible contaminated environments plays an important role in leptospirosis transmission [1,16]. Working as an urban sweeper is also significantly associated with leptospirosis. ...
This study was carried out to determine the risk factors of leptospirosis infection among local urban service workers in Sabah. This is a cross-sectional study involving 394 workers in Kota Kinabalu City, Sabah, conducted from February to March 2017. Information on demography, occupational exposures and environmental factors was obtained by a modified validated questionnaire. Polymerase Chain Reaction (PCR) was used to determine the prevalence of positive leptospirae. The overall figure for positive leptospirae was 9.4% (95% CI: 6.8-12.8). Urban sweepers and lorry drivers made up the highest proportion of positive leptospirae respondents, contributing 15.5% and 9.4%, respectively. The significant risk factors for positive leptospirae were older age (p-value = 0.001), higher monthly salary (p-value = 0.039), longer duration of employment (p-value = 0.011) and working as an urban sweeper (p-value = 0.021). Leptospirae was prevalent among healthy urban service workers and relates to their working activities.
... Several other studies reported the prevalence of many other serovars other than australis. [9,13] There is definitely a shift in the serovar distribution in different geographical areas and our aim to identify the predominant serovar in this area was fruitful. No such data was available in humans to the best of our knowledge from this part of Karnataka and our work will definitely be a milestone among the prevalence studies. ...
... Several other studies reported the prevalence of many other serovars other than australis. [9,13] There is definitely a shift in the serovar distribution in different geographical areas and our aim to identify the predominant serovar in this area was fruitful. No such data was available in humans to the best of our knowledge from this part of Karnataka and our work will definitely be a milestone among the prevalence studies. ...
Background:
Leptospirosis is a zoonotic disease of ubiquitous distribution. During rainy seasons, in spring and summer and also during harvest times, the risk of leptospirosis increases as there are chances of frequent contact with infected rat population which is common in Karnataka as farming is a main source of income to the people here. There is a paucity of data regarding the prevalent serovars from Karnataka. This study was undertaken as an attempt to compare a battery of tools such as immunochromatographic test (ICT), microscopic agglutination test (MAT), immunoglobulin M (IgM) enzyme-linked immunosorbent assay (ELISA) and in-house polymerase chain reaction (PCR) to detect leptospirosis.
Settings and design:
This study using consecutive sampling technique was conducted in a tertiary care centre, Mysore, Karnataka.
Subjects and methods:
Samples from 783 suspected cases of leptospirosis in and around Mysore between April 2013 and April 2016 were processed. Samples from 783 patients suspected of leptospirosis were subjected to ICT, IgM ELISA, MAT and in-house PCR.
Statistical analysis used:
The statistical analysis was carried out using SPSS software version.
Results:
Among 783 samples tested, only 14 (1.7%) were positive by ICT, 341 (44%) were positive by IgM ELISA, 368 (47%) were positive by MAT and 393 (50.2%) were positive by in-house PCR.
Conclusions:
Mysore can be considered endemic for leptospirosis. The in-house PCR based on LipL32 gene proved to be useful in the early diagnosis of leptospirosis.
... Agricultural workers, forest workers and animal handlers have been identified as one of the high risk groups [11][12][13] for acquiring leptospirosis on the rural environment. A holistic knowledge of the transmission dynamics of the disease is required to formulate intervention strategies for a particular geographical area. ...
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.
ELISA was used to detect specific IgM and IgG in sera from humans with current or past leptospirosis. A serological pattern of a high IgM titre (greater than or equal to 1280), or moderately increased IgM (160-640) in conjunction with a low IgG titre (less than or equal to 20), with serovar copenhageni antigen was characteristic for approximately two-thirds of the sera from serovar icterohaemorrhagiae patients obtained in the first two months of the disease. The antigen was the supernatant of a heated and centrifuged culture of leptospires. Antigens were prepared from serovars copenhageni, grippotyphosa, hardjo and patoc. Sera from patients with icterohaemorrhagiae, grippotyphosa and hardjo infections showed cross-reactivity when different antigens were used. In past infections the IgG titres were clearly higher with the homologous antigen. ELISA for IgM and IgG allows the rapid diagnosis of acute leptospirosis.
An outbreak of acute febrile illness with haemorrhagic manifestations and pulmonary involvement occurred in Diglipur of North Andaman during October-November 1993. Investigations were carried out to see whether leptospires were responsible for this outbreak. Serum samples were collected from suspected cases and tested for presence of antibodies to leptospires by microscopic agglutination test (MAT) using a battery of 19 antigens representing 16 serogroups. 66.7 per cent of the specimens showed significant titres of antibodies against leptospires, 18 of 23 paired sera (78.3%) showed sero-conversion or four-fold rise in antibody titres. The commonest serovar involved was Leptospira grippotyphosa followed by L. canicola and L. JEZ bratislava. In 7 patients L. grippotyphosa was the sole serovar against which antibodies were detected. Clinical and epidemiological observations of this outbreak were similar with that of earlier seasonal outbreaks of acute febrile illness with haemorrhagic manifestations occurring in the same area, indicating that the past outbreaks may also have been due to leptospires. This is the first report of pulmonary leptospirosis from India.
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.
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.
Jarawas, a classical hunter-gatherer tribe of Andaman and Nicobar islands have lived in isolation for several centuries. It is only recently have they started to come in contact with the outsiders, shedding their hostility. Since then, several disease outbreaks have been reported amongst them. Screening of sera samples collected during one such outbreak showed very high endemicity of hepatitis-B infection with over 60% of the individuals positive for hepatitis B surface antigen (HBsAg). The rates of HBsAg observed among the Jarawas are probably the highest ever reported in the world and warrant immediate control measures which would prevent further spread of this infection in the community.
A study was conducted with the objective of assessing the leptospiral carrier state and seroprevalence among animal population of Andaman and Nicobar Islands. A total of 494 sera samples from different domestic animals and 85 samples from rats (Rattus rattus) were tested by microscopic agglutination test using nine serogroups prevalent in these islands. Antibodies to leptospires were detected in 164 samples giving an overall seroprevalence of (33.11%). The seroprevalence was highest among cows (40.32%). Of 85 rat (Rattus rattus) samples tested for antileptospiral antibodies six (7.1%) were positive. Leptospires were isolated from kidney of two rats and urine of one cow. Isolate from urine of cow was heavily contaminated and was subsequently lost during further subculture. The two isolates were found to be pathogenic, belonging to serogroup Grippotyphosa. The isolates were further characterized by using a set of monoclonal antibodies. The agglutination patterns of isolates were similar to that of ratnapura and valbuzzi, however these did not completely match.