Abstract
Purpose:
Leptospirosis is a waterborne zoonotic disease that primarily causes systemic illness, followed by uveitis. After heavy flooding in Madurai district, an epidemic outbreak of systemic and ocular leptospirosis occurred in 1994. Our data shows a transition to endemicity after each epidemic.
Aim:
The aim of this study is to report the clinical signs, epidemic outbreaks, and persistent endemicity of leptospiral uveitis, as well as the diagnostic dilemmas associated with it.
Methods:
A retrospective analysis of clinical signs was conducted using medical records of leptospiral uveitis patients over a period of 27 years (1994–2020) in a tertiary care eye hospital. The clinical workup of uveitis included a detailed clinical history, systemic, and ophthalmic examination. Microagglutination tests (MATs) was done at the Centers for Disease Control and Prevention (CDC) in Atlanta and later in our regional laboratory. Serum samples were collected from human systemic leptospirosis cases and a small group of animals in and around Madurai.
Results:
The first epidemic outbreak resulted in 200 seropositive patients. Subsequent epidemic outbreaks occurred in 1997, 1998, 2001, 2005, and 2012, with Madurai experiencing multiple outbreaks. However, the disease remained endemic, with 25–50 patients being observed per year in between the peaks. Ocular examination revealed acute non-granulomatous uveitis (94.9%), pan uveitis (59.8%), vitreous inflammatory reaction (55.4%), retinal vasculitis (29.5%), disc hyperemia (20.9%), and hypopyon. (16.2%). New serovars emerged every year, resulting in decreased sensitivity of the MAT. Over time, the MAT started to miss diagnoses.
Conclusion:
The persistent endemicity of leptospiral uveitis emphasizes the need for accessible diagnostic tests. The low performance of the MAT can be attributable to the use of an older panel. The incorporation of new isolates in the MAT by a national laboratory will improve the accuracy of diagnosis.
Keywords: Endemic, leptospiral uveitis, leptospirosis and eye, microagglutination test, ocular leptospirosis
Leptospirosis is a waterborne zoonosis, which is under-reported in developing countries due to the scarcity of laboratory techniques.[1,2] Physicians rely on clinical signs for diagnosis, but laboratory confirmation is necessary. In India, there is a need for a fully equipped national laboratory on the mainland.[3] In 1994, Tamil Nadu experienced an epidemic outbreak of leptospiral uveitis,[4] which has since remained endemic. Initially, samples were tested at the CDC in Atlanta, followed by a laboratory in our hospital that was established with welcome funding. In this study, we present clinical and laboratory data on leptospiral uveitis over a 27-year period. Additionally, we present the seroprevalence of a subgroup of systemic and veterinary leptospirosis.
Methods
Ethical approval for the study (RET199400401) was granted by the Institutional Review Board. Informed oral consent was obtained from all patients for routine clinical and laboratory examinations.
Uveitis workup
The clinical diagnosis of uveitis was based on a detailed clinical history, a thorough review of systems, and an ophthalmic examination, including slit-lamp and indirect ophthalmoscopy. This was followed by a tailored laboratory workup.[5] Additional laboratory tests, radiologic workup, and vitreous biopsy were performed as needed.[5] The anatomical location, grading of inflammation, and outcome measures were recorded initially according to the proposal of International Uveitis Study Group (IUSG) and later according to the Standardization of Uveitis Nomenclature (SUN) working group.[6,7] Based on our previous clinical experience with the initial outbreak and subsequent data from patients, we published a clinical diagnostic rule.[8] Non-granulomatous pan uveitis, hypopyon, vitreous cells and membranes, vasculitis, and disc hyperemia in the absence of retinochoroiditis in farmers were identified as important clinical predictors. Patients with these clinical findings and positive serology received a confirmed diagnosis of leptospiral uveitis.
Leptospiral serology
Whenever the clinical diagnosis was leptospiral uveitis as per above-mentioned clinical diagnostic rule,[8] (presence of acute non-granulomatous uveitis, hypopyon, membranous vitreous inflammatory reaction, and retinal vasculitis disc hyperemia), 2 ml of serum was stored in −80° deep freezer. MAT was performed initially by the leptospirosis reference laboratory at the Centers for Disease Control and Prevention (CDC), Atlanta, USA, according to a standard methodology and in a regional laboratory at Tamil Nadu veterinary college Chennai.[4] A set of samples were tested also in Indian National reference laboratory at Andaman. In 1999, regional leptospirosis laboratory was established at the Aravind Medical Research Foundation, with a help of Welcome funds and National Leptospirosis Reference Center, Royal Tropical Institute, Amsterdam, Netherlands.[8] The quality of technique and the leptospiral cultures were tested yearly by the International Leptospirosis MAT Proficiency Testing Scheme by Royal tropical institute, Netherlands.[9] Since 2017, due to practical difficulties in maintaining leptospiral serovars and its very low sensitivity attributable to continuous use of older panel, we moved on to use Pan Bio ELISA commercial kits. The details of laboratory work up have been already explained in our previous publications.[4,8]
Systemic leptospirosis
Serum of clinically suspected systemic leptospirosis patients attending Government hospital, Madurai were sent to our laboratory as they did not have dedicated leptospirosis laboratory to carry out MAT and Enzyme-Linked Immunosorbent Assay (ELISA).
Veterinary leptospirosis
As we wanted to learn about the reservoirs, carriers, and the seroprevalence of this zoonotic disease, we studied a small group of animals in and around Madurai in 2008. Cattle urine was collected from paddy field. Goat urine samples were collected from slaughter house. Serum, urine samples, and kidney biopsy of field rats from Madurai were collected in our laboratory.
Data collection and analysis
The records of all patients who were diagnosed with leptospiral uveitis between 1994 and 2020 were reviewed retrospectively. Demographic details, history, and clinical findings were collected using a data collection form as explained earlier.[8] Over these decades several individual studies were conducted in same cohort of patients to study different aspects of the disease at different time period. Details of those data were compared with overall data to see any trend in presentation.
Results
During 27 years of the study from 1994 to 2020, eye hospital had seen total of 6,869,305 new outpatients with several ocular ailments (free patients: 2,006,014 and paying patients: 4,863,291). As per regular practice, the general ophthalmology units referred all uveitis patients to the uveitis clinic for detailed workup. Out of 6,869,305 ophthalmic patients, 87,216 (1.27%) were new uveitis patients of varying causes. During the study period, 3,658 (4.1%) were clinically diagnosed as leptospiral uveitis; of them 1,268 (34.7%) patients were seropositive for leptospirosis. For the analysis of demographic and clinical variables, we have taken only serologically proven patients into consideration. Of these 1,268 patients, 937 (73.9%) were men and 331 (26.1%) were women. 969 (76.4%) were from rural areas and 299 (23.6%) were from urban areas. Young male farmers were common in all our studies. Systemic past history of our leptospiral uveitis patients included fever in 936 patients (73.8%), severe headache in 451 (35.6%), joint pain in 440 (34.7%), severe fatigue in 420 (33.1%), diarrhea in 233 (18.4%), and jaundice in 75 (5.9%). Past history of exposure to risk factors were multifactorial, patients used unsafe water for bathing (79.6%) for drinking water (79.4%) had animal contact (30.2%) visited endemic region (11.6%). Demographic and clinical findings are given in Table 1 in which, all our previous publications results are compared to show the consistency. Seroprevalence over various periods are given in Table 2 to show varying consistency. Various clinical manifestations are given in Fig. 1. The frequency of clinical, seropositive, and seronegative cases over 27 years is given in the graph in Fig. 2. Serology in a small group of animal study done in our center earlier revealed 90% of cows and 70% of dogs to be Leptospira seropositive. The seroprevalence in animals, systemic human, and ocular human are given in Table 3. Major and minor diagnostic clinical predictors for leptospiral uveitis are given in Table 4.[8]
Table 1.
Demographic and clinical variables in patients with leptospiral uveitis 1994–2021
| Year of publication | 1997 AJO4 | 2000 BJO46 | 2005 PhD Thesis Dr. MGR Medical university | 2016 OII8 | Present study |
|---|---|---|---|---|---|
| Duration of study | 1994 Jan–Sep | 1994–1997 Jan–Dec | 1996–2001 Jan–Dec | 2005–2012 Jan–Dec | 1994–2021 Jan–Dec |
| Demographic | |||||
| No. of patients (%) | 73 (%) | 276 (%) | 533 (%) | 172 (%) | 1,268 (%) |
| Age | |||||
| ≤20 | 7 (9.6) | 38 (13.7) | 61 (11.4) | 12 (7.0) | 181 (14.3) |
| 21–40 | 38 (52.1) | 171 (61.9) | 356 (66.7) | 96 (55.8) | 767 (60.5) |
| >40 | 28 (38.3) | 67 (24.2) | 116 (21.7) | 64 (37.2) | 320 (25.2) |
| Mean age (Yrs) | 37.1 | 33.5 | 37.1 | 37.28 | 33.29 |
| Gender | |||||
| Male | 60 (82.2) | 227 (82.2) | 404 (75.8) | 112 (65.1) | 937 (73.9) |
| Female | 13 (17.8) | 49 (17.8) | 129 (24.2) | 60 (34.9) | 331 (26.1) |
| Laterality | |||||
| Unilateral | 35 (47.9) | 158 (57.2) | 336 (46) | 87 (50.6) | 764 (60.3) |
| Bilateral | 38 (52.1) | 118 (42.8) | 394 (54) | 85 (49.4) | 504 (39.7) |
| Occupation | |||||
| Farmers | 47 (64.4) | 163 (59.1) | 315 (59.1) | 100 (58.1) | 736 (58) |
| Others | 26 (35.8) | 113 (40.9) | 218 (40.9) | 72 (41.9) | 532 (42) |
| Clinical variables | |||||
| No. of eyes (%) | 111 eyes (%) | 394 eyes (%) | 730 eyes (%) | 257 eyes (%) | 1,772 eyes (%) |
| Duration | |||||
| >90 days | 11 (9.9) | 87 (22) | 89 (12.2) | 31 (12.1) | 135 (7.6) |
| ≤90 days | 100 (90.1) | 307 (78) | 641 (87.8) | 226 (87.9) | 1,637 (92.4) |
| Location | |||||
| Pan uveitis | 106 (95.5) | 238 (86.2) | 489 (67) | 142 (55.2) | 1,060 (59.8) |
| Anterior, posterior, and intermediate | 5 (4.5) | 38 (13.8) | 241 (33) | 115 (44.8) | 712 (40.2) |
| Pathology | |||||
| Gran | 9 (8.1) | 1 (0.3) | 23 (3.2) | 17 (6.6) | 90 (5.1) |
| Non-gran | 102 (91.9) | 393 (99.7) | 675 (92.5) | 240 (93.4) | 1,682 (94.9) |
| Not applicable | - | - | 32 (4.3) | - | |
| Non-granulomatous | 102 (91.9) | 393 (99.7) | 675 (92.5) | 240 (93.4) | 1,682 (94.9) |
| Synechia | 27 (24.3) | 125 (32) | 187 (25.6) | 31 (12.3) | 386 (21.8) |
| Hypopyon | 14 (12.6) | 82 (21) | 130 (17.8) | 21 (8.2) | 287 (16.2) |
| Cataract | 10 (13) | 54 (14) | 160 (21.6) | 63 (24.5) | 327 (18.5) |
| Vasculitis | 57 (51.4) | 162 (41) | 218 (29.9) | 25 (9.7) | 523 (29.5) |
| Disc edema | 4 (3.6) | 74 (19) | 223 (40.8) | 53 (20.6) | 370 (20.9) |
| Vitreous reaction | 85 (76.6) | 316 (80) | 421 (57.6) | 176 (68.5) | 982 (55.4) |
| Pars Plana exudates | 2 (1.8) | Nil | 73 (10) | 1 (0.4) | 82 (4.6) |
| Choroiditis/Retinitis | 5 (4.5) | Nil | 24 (3.3) | 2 (0.8) | 53 (3.0) |
| Elevated intra ocular pressure | (-) | - | - | 2 (0.8) | - |
Comparison of data published at various time points from same population. Total number of patients=1,268, Total number of eyes=1,772 (Data are from different laboratories, hence presented as published before). Gran: Granulomatous, Non-gran: Non-granulomatous
Table 2.
Serogroup distribution of all seropositive leptospiral uveitis patients comparison of data published at various time points from same population
| Year of publication | 199658 IJMR No (%) | 19974 AJO No (%) | 200046 BJO No (%) | 2005 PhD Thesis | 201259 JMM No (%) | 20168 OII No (%) | Present study No (%) |
|---|---|---|---|---|---|---|---|
| Duration of study | 1994 | 1994 | 1994–1997 | 1996–2001 | 2011–2012 | 2005–2012 | 1994–2020 |
| Mar–July | Jan–Sep | Jan–Dec | Jan–Dec | Jan–Dec | Jan–Dec | Jan–Dec | |
| L. Autumnalis | 3 (21.4) | 16 (21.9) | 101 (36.6) | 106 (19.9) | 25 (23.4) | 58 (33.7) | 224 (17.7) |
| L. Icterohaem | 5 (6.9) | 15 (5.4) | 66 (12.4) | 9 (8.4) | 22 (12.7) | 151 (11.9) | |
| L. Australis | 3 (21.4) | 18 (24.7) | 39 (14.1) | 88 (16.5) | 31 (29.0) | 25 (14.5) | 141 (11.1) |
| L. Canicola | 3 (4.1) | 19 (6.9) | 38 (7.1) | 53 (4.2) | |||
| L. Louisiana | - | 83 (15.6) | 14 (13.1) | 33 (19.2) | 45 (3.6) | ||
| L Bratislava | 39 (14.1) | 44 (3.5) | |||||
| L. Cynopteri | 22 ((4.1) | 18 (16.8) | 3 (1.7) | 40 (3.2) | |||
| L. Pomona | 6 (42.8) | 12 (16.4) | 29 (10.5) | 46 (8.6) | 8 (7.5) | 9 (5.2) | 38 (3.0) |
| L. Javanica | 2 (14.3) | 5 (6.8) | 6 (2.2) | 12 (2.3) | 2 (1.2) | 27 (2.1) | |
| L. Grippotyp | 11 (2.1) | 14 (13.1) | 1 (0.6) | 23 (1.8) | |||
| L. Bulgaria | 23 (8.3) | 19 (1.5) | |||||
| L. Jegathlara | 14 (19.2) | 10 (3.6) | 11 (0.9) | ||||
| L. Hardjo | 10 (3.6) | 10 (0.8) | |||||
| L. Semaranga | 82 (15.4) | 1 (1) | 2 (1.2) | 7 (0.5) | |||
| L. Andamana | 1 (1) | 6 (3.5) | 6 (0.5) | ||||
| L. Sejroe | 5 (6.8) | 4 (0.8) | 2 (1.9) | 8 (4.6) | 5 (0.4) | ||
| L. Pyrogens | 1 (1.4) | 12 (11.2) | 2 (1.2) | 3 (0.2) | |||
| Others | 8 (11.0) | 23 (8.3) | 176 (33.0) | 412 (32.4) |
Figure 1.
Various ocular manifestations of leptospirosis. (a and b) Bilateral free floating vitreous membrane in a young farmer. (c) Patchy retinal vasculitis of superior temporal vein. (d) string of pearl-like vitreous precipitates with floating vitreous membrane. (e) Dense vitreous membrane attached to the hyperemic disc. (f) Disc hyperemia. (g) Pearl-like mature cortical cataract with hypopyon. (h) Unilateral cataract with clear lens in the other eye
Figure 2.
From 1994 to 1999 all cases clinically diagnosed as leptospiral uveitis were all positive by MAT done at CDC Atlanta, however next three epidemics in 2000, 2006, and 2010 had different serovars negative cases were more than positive cases. 2012 again positive cases were more than negative
Table 3.
Seroprevalence in animals and human from Madurai48
| *Seroprevalence in cows48 | Seroprevalence in human systemic leptospirosis | Seroprevalence in human Ocular leptospirosis |
|---|---|---|
| L. Cannicola (22%) | L. Icterohaemorrhagiae (26%) | L. Automonalis (17.7%) |
| L. Australis (11%) | L. Semaranga (26%) | L. Icterohaemorrhagiae (12%) |
| L Sejroe (11%) | L. Automonalis (16%) | L. Australis (11.1 (%) |
| L. Icterohaemorrhagiae (11%) | L. Australis (16%) | L. Louisiana (3.6%) |
| L. Automonalis (6%) | L. Louisiana (10%) | L. Canicola (4.2%) |
| L. Hebdomadis (6%) | L. Canicola (5%) | L. Bratislava (3.5%) |
| L. Tarassovi (6%) | L. Pyrogens (1%) | L. Cynopteri (3.2%) |
| L. Louisiana (3%) | L. Sejroe Nil | L. Pomona (3.0%) |
| L. Semaranga (3%) | L. Tarassovi Nil | L. Javanica (2.1%) |
| L. Pyrogens (3%) | L. Hebdomadis Nil | L. Semaranga (0.5%) |
*(Only common serovars are given here)
Table 4.
Clinical diagnostic predictors for Leptospiral uveitis[8]
| OR (95% CI) | P | |
|---|---|---|
| Major predictors | ||
| Non-granulomatous uveitis | 24.52 (10.89–55.21) | <0.001 |
| Farmer/Animal oriented job | 11.54 (5.34–24.94) | <0.001 |
| Pan uveitis | 6.49 (2.73–15.43) | <0.001 |
| Hypopyon | 6.09 (1.32–28.02) | <0.001 |
| Vitreous membranes and cells | 4.55 (2.18–9.49) | 0.020 |
| Absence of: Retinitis/choroiditis | 34.23 (2.19–535.14) | 0.012 |
| Absence of ocular hypertension | 7.56 (1.26–45.52) | 0.027 |
| Minor predictors | ||
| Male patients | 2.75 (1.40–5.37) | 0.003 |
| Bilateral | 2.16 (1.11–4.19) | 0.023 |
| Disc hyperemia* | 2.83 (0.37–21.84) | 0.318 |
| Retinal periphlebitis * | ||
| Rapidly maturing cortical cataract* |
OR – Odds ratio, CI – Confidence interval. *Statistically not a significant predictor, However, clinically they were very significant
Discussion
Leptospirosis is an important spirochetal, waterborne zoonosis. Millions of leptospires get excreted from infected animal urine, contaminating the water and the soil. It enters intact mucus membrane or an abraded skin of human to cause systemic febrile illness in the population that work with animals or contaminated paddy field. Leptospirosis has worldwide distribution[10,11,12,13,14,15,16,17,18,19,20,21,22,23] and several reports have come out from India as well.[1,2,3,4,24,25,26,27,28,29,30,31,32,33,34,35,36,37,37,39] Primary infective stage/fever occur in monsoon season; however, ocular manifestation is late immune reaction. Hence, leptospiral uveitis patients come in post monsoon season. Being a dedicated ophthalmic hospital, we encountered an epidemic outbreak of ocular complication of leptospirosis in and around Madurai, Tamil Nadu in 1994.4 Following that we had multiple epidemics outbreaks in 1997,1998, 2001, and 2005 [Fig. 2], and we continue to have 25–50 new cases in between epidemics establishing its endemicity. The number of cases discussed in this analysis reflects only patients who developed ocular complication which is a tip of an iceberg. The exact incidence of uveitis in systemic leptospirosis is not known in India. European authors reported an incidence of 10–44% of uveitis out of all systemic leptospirosis,[40,41,42] while Brand and Heath reported 13% and 2% from Israel and United States, respectively.[43,44] The incidence of leptospiral uveitis probably depends on the awareness of clinical signs of leptospirosis. Almost all our patients had prior history of fever, severe headache, joint pain, severe fatigue, diarrhea, and jaundice. However, the primary physician had diagnosed it as seasonal fever, not even single case was suspected as systemic leptospirosis. The aim of this study is to reveal endemicity of a serologically proven systemic infection over 27 years in South India that caused secondary ocular complication, and to discuss pathognomonic clinical signs and clinical data that can predict the clinical diagnosis of leptospiral uveitis.[8]
Systemic leptospirosis: Clinical features
Systemic leptospirosis presents with wide spectrum of severity ranging from asymptomatic, mild, and moderate-to-lethal multiorgan hemorrhage with failure and death.[1,2,12] Any organ may be primarily involved, and based on that organ, the symptoms and signs vary. As mentioned in results, our patients had fever, severe headache, joint pain, severe fatigue, diarrhea, and jaundice. However these patients were diagnosed as a case of pyrexia of unknown origin, pulmonary hemorrhage, cardiac failure or myocarditis, hepatorenal failure or jaundice, not as leptospirosis. Etiological diagnosis of these various systemic forms are often missed especially in rural setting where leptospiral diagnostic tests are not available, more so in poverty-stricken population who fail to go to tertiary centers for specific diagnosis.[3,11] Exact incidence, prevalence, mortality rate, geographical distribution of leptospirosis, and availability of laboratory diagnosis have not been a subject of serious concern in many developing countries.[1,2] Both public and medical students lack the awareness of existence of leptospirosis.[35,36,37,38]
A remarkable review on diagnostic tools used in the evaluation of acute febrile illness in South India showed a total of 40 studies, in tertiary care centers. Of them, only 15 out of 40 screened for leptospirosis. Out of 15, 6 studies did ELISA and only 1 study performed MAT; all others were unspecified tests.[45] Many deaths do not have the specific confirmed diagnosis in rural India and in some urban hospitals as well. Inadequacy of data on burden of leptospirosis in this agricultural country is multifactorial, which includes lack of awareness among medical practitioners and general public. In addition, farmers have a plenty of opportunities to get infected in the paddy fields. More critically, the lack of reliable diagnostic tools contribute to misdiagnosis and inadequate data.[3]
Ocular leptospirosis: Clinical features
Ocular leptospirosis follows systemic disease after a latent phase of around 3–6 months. Ophthalmologists often miss the diagnosis of leptospiral uveitis because of a symptom free latent phase between systemic and ocular symptoms and a vague past history of systemic illness of varying manifestations. Onset and severity of leptospiral uveitis were variable; the severity do not correlate with the severity of systemic disease. Even patients who had a mild fever had severe pan uveitis; sometimes patients who had leptospiral jaundice came with mild non-granulomatous uveitis. During the first epidemic, the severity was more and patients presented with pan uveitis, over period of time, anterior, intermediate, and posterior uveitis were also diagnosed.
Ocular examination revealed, acute non-granulomatous uveitis, which was predominantly followed by pan uveitis, membranous vitreous inflammatory reaction, hypopyon, retinal vasculitis disc hyperemia, and rapidly maturing cataracts (within 3–6 months) [Fig. 1a-h]. These clinical findings were consistent in all our previous publications from same population[4,8,46] [Table 1]. Absence of retinal or choroidal involvement was very marked, pars plana exudates, and elevated intraocular pressure were not common. Ocular signs that can predict the clinical diagnosis are given in Tables 1 and 4.
Cortical cataract, which was white and rapidly progressing in young patients, were often seen as clinical sign in this cohort as well as in our previous publications[3,4,8,46,47] [Fig. 1g, Fig. 1h]. Vitreous inflammatory cells ranged from 1+ to 4+. Vitreous veil like membranes were seen either attached to the disc or they freely floated in the vitreous. As described by Feigin, Rathinam, Duke Elder, and Woods, membranous vitreous opacities are the hallmark of the disease[3,4,8,40,41] [Fig. 1a-f].
When the uveitis is anterior, it had very good visual prognosis with any form of steroids. As it resolves without visual loss, they never get worked up for etiological cause by general ophthalmologist. Unless uveitis specialist has it in their differential diagnosis, etiological diagnosis is always missed. However, ocular picture is more specific in pan uveitis than that in systemic leptospirosis; hence, clinical decision rule (CDR) is available for ophthalmologists.[8] Authors claim that multiple logistic analyses identified clinical diagnostic predictors that can assist primary care ophthalmologists [Table 4]. When the patient has non-granulomatous pan uveitis, hypopyon, and vitreous membranes/cells in the absence of retinochoroiditis, CDR constituted the value of predictive signs, with the sensitivity and specificity of 86% and 90.7%.[8] Rapidly maturing cortical cataract in farmers and free floating vitreous membranes in vitreous are pathognomonic signs for clinical diagnosis.[4,8,40,41]
Serovar distribution
Top serovars found in our uveitis patients are given in Table 2. The last 10 years we also used Pan Bio ELISA kit; hence, we do have results of positive or negative for leptospirosis, conversely serovar identification was not possible. During the study period, in our ocular patients L. Autumnalis, L. Icterohaemorrhagiae, and L. Australis were seen predominantly [Table 2]. Serovars found in systemic leptospirosis patients referred from Government General Hospital were predominately L. Icterohaemorrhagiae and L. Semaranga [Table 3]. Field rats were found to be the major reservoir in our paddy fields of Madurai, and serovar L. Automonalis was the most common isolate in animals as well.[48] Serovar predominance in each of our study varied although L. Automonalis predominated always [Tables 2 and 3].
Another publication from two cities of Tamil Nadu state, the leptospiral seroprevalence was higher among Pudukkottai, miners (65.3%) when compared with Karur miners (10.8%).[49] Pudukkottai miners had high-risk challenges, for instance exposure to water bodies, rat infestation, wet mine areas, and cattle rearing. L. Autumnalis was found to be the commonest serogroup followed by L. Australis and L. Icterohaemorrhagiae. These data are very similar to our experience. Previous animal studies in Tamil Nadu also isolated L. Automonalis, L. Icterohaemorrhagiae, and L. Panama.[28,29] L. Pyrogens was the predominant serovar found in 100.0% of canine and 85.7% of rodents in Mumbai.[25] Identification of new serovar was reported by Gangadhar belonging to serogroup L. Australis and named it as L. Australis Bharathy.[28] Natarajaseenivasan described L. borgpetersenii, serovar L. Javanica infection among cattle, rats, and humans in the Cauvery river valley of southern India.[24] In a study on acute phase of illness from the island of Mayotte, 22 strains of leptospires were isolated from the patients.[50] Additional molecular characterization of the isolates allowed the identification of 10 pathogenic Leptospira genotypes that are previously unknown serovars. Author reports ten potentially new pathogenic Leptospira genotypes, in Mayotte.[50] Addition of these new serovars in the panel of MAT will increase the sensitivity of MAT. However, commercially available ELISA will not address any of these changes. All these serovars are seen in leptospiral uveitis patients as well [Table 2]. The risk factors include occupational exposure and the higher number of reservoir animals roaming around freely on streets and human living in close association with these animals. Farmers were not aware of their risk factors. Some of them mentioned they electrocuted the field which is illegal, but collected dead rats with bare foot and hands.[38,51] A public awareness program on this potential killer disease is a must.[38,39]
Seropositivity and seronegativity
In our study, clinically diagnosed leptospirosis cases were all seropositive in early on (1994). However, the positivity slowly started declining and negative cases increased over the period [Fig. 2], although same investigator examined all cases. SR Rathinam (SRR) Our study showed the uniformity in demographics, systemic, and ocular signs. However, it also showed marked discrepancy in incidence, seroprevalence, sero positivity, and negativity [Fig. 2], Similar to our experience, issues like endemicity, negative laboratory tests, and low sensitivity of tests are seen all over the world including Sri Lanka, Tanzania, Argentina, Brazil, China, Taiwan, India, Portugal, Middle Eastern countries, Uganda, and several other countries.[11,13,16,17,18,19,20,52,53,54] Argentina (1999–2005) reported 812 suspected cases. Of them, only 182 (22.4%) were positive for leptospirosis.[16] Brazil (2000–2015), data on 16 years showed a total of 2,48,616 suspected cases of leptospirosis of which 60,999 (24.5%) were confirmed on laboratory tests.[18] China (2005–2015) reported a total of 7,763 cases of which only 2,403 (31%) cases were laboratory confirmed. Taiwan had (2007 and 2014) 10,917 leptospirosis clinical cases, only 665 (6.1%) were lab confirmed.[19] A prospective study from Sri Lanka on acute illness patients, MAT missed the diagnosis in 80% even with paired serum sample.[11] Author says that MAT should be limited to epidemiological work. Chandigarh (2004–2008) gives an account of 232 clinically diagnosed cases over 5 years. Paired acute and convalescent serum samples were tested by PanBio IgM ELISA, of them only 86 (37%) patients were positive for Leptospira.[26] All the above studies obviously point out very low sensitivity of MAT and ELISA. MAT could still be a gold standard, provided we customize the panel according to the seroprevalence of that geographical area where new serovar appears.[55] The significance of this was shown in a Tanzania report, where the prevalence of antibodies to Leptospira increased 40-fold (0.26–10.75%) following the inclusion of locally transmitted serovars into the MAT panel.[56] It is possible in world reference labs but that is rarely done in regional laboratories.
Challenges in clinical diagnosis and laboratory confirmation
Clinical diagnosis on systemic leptospirosis is difficult because of inconsistent clinical forms from asymptomatic patients to lethal multiorgan failure.[1,2,12,15,16,17,18,19,20] Asymptomatic group never report to doctors. As the awareness is very low in many places, patients with severe multiorgan failure often die before the diagnosis, and they often fail to get leptospirosis in their differential diagnosis.[37] In addition, advanced laboratory diagnosis is not available to physicians. The National Reference Laboratory of India is in Andaman and not in the main land. Hence, shipping the serum of every critically ill patient is impossible. In a report from Chandigarh, the authors mention the difficulty of MAT, for which the samples had to be sent to the National Reference Laboratory for Leptospirosis, Port Blair, Andaman Islands, India. Shipping in cold storage by flight for each emergency case is impossible.[26]
Molecular diagnostics and ELISA tests will be more feasible than MAT. Current improvements in these tests should be made available as point of care investigations all over India by establishing one National Reference Laboratory and several regional laboratories. That can isolate circulating serovars which vary every year [Table 2]. New technology in laboratory diagnosis can be introduced and validated in our population. It is mandatory because it affects farmers and low socioeconomic population who cannot access the private tertiary care centers. Leptospirosis is neither notifiable disease nor listed as common infectious disease in farmers in India, which needs to be amended.
Brazil has one National Reference Laboratory that performs all the tests, including Polymerase Chain Reaction (PCR) and isolation of Leptospira. Five regional laboratories perform MAT and ELISA and then, state laboratory network to perform ELISA-IgM. The notification of leptospirosis cases is mandatory in Brazil.[18] In China, leptospirosis is one of 39 notifiable infectious diseases that must be reported within 24 hours (Category B disease), China noticed significant decline in death rate in leptospirosis, which is attributed to improvement in prevention and control measures, including health promotion activities, sanitation, and leptospirosis vaccination programs.[54] Widespread vaccination of dairy cows in New Zealand in the 1980s led to a marked fall in incidence of leptospirosis.[57] This point needs to be studied in detail in India.
Conclusion
Our data show several important issues. The foremost issue is the persistent endemicity of leptospirosis in and around Madurai for nearly three decades. We have shown only a late complication of the disease. Systemic leptospirosis in Madurai should be much more, which is not recognized. Leptospirosis should not be neglected as it remains as a potentially killing disease of the young, productive, and economically less-developed farmers. The clinical picture is similar to dengue fever, rickettsial infections, malaria, and covid-19. The lack of a rapid and accurate diagnostic test during the acute stage of the disease will lead to misdiagnosis. MAT cannot be considered “ the gold standard” unless it uses panels of recent isolates, representing circulating serovars from the area where the patient became infected.[55] India needs to increase the awareness among medical practitioners and public at risk. The national laboratory with improved investigations for early detection is certainly an urgent need.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
Acknowledgments
Laboratory technicians, Tamil Nadu veterinary college Chennai, CDC Atlanta, USA, Royal Tropical institute, Amsterdam, Netherlands, Indian National reference laboratory (ICMR), for leptospirosis Andaman, Regional leptospirosis laboratory at Aravind Medical Research Foundation. Medical officers and nurses who participated in management of patients.
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