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Indian Journal of Medical Microbiology, Vol. 24, No. 4, October-December, 2006, pp. 329-331 Supplement Seroprevalence of leptospirosis in man and animals in Tamilnadu Koteeswaran A Center for Animal Health Studies, Tamil Nadu Veterinary and Animal Sciences University, Madhavaram Milk Colony, Chennai - 600 051 Code Number: mb06104 Leptospirosis, is a worldwide zoonosis caused by spirochetes of the genus Leptospira affecting humans and animals; humans are incidental hosts. Ayyar made the earliest record of leptospirosis in Tamil Nadu among Madras hounds.[1] Subsequently, Venkataraman and Jaganathan[2] reported the occurrence of an outbreak of leptospirosis in Madras state. Following this, a survey on the incidence of leptospirosis among domestic animals in and around Madras City (presently Chennai) was made by Jawad Hussain.[3] Since then reports on isolation of leptospires,[4],[5] seroprevalence among animals[6],[7],[8],[9],[10],[11],[12],[13] and in human beings[14],[15] were made from Tamil Nadu. However, most of the literature on leptospirosis is repetitive in nature.[16] Faine et al[17] observed that prevention measures included a knowledge on the number and frequency of both human or animal cases, the infecting serovar, serogroup or genetic group of leptospires, their maintenance host, means of transmission and the prevalence of antibodies indicating subclinical infection in the population. Here, we furnish data on the percent positivity to leptospirosis in blood serum tested since 1997. Detailed analysis has been done on the serogroup distribution in the past three years (April 2003 to March 2006), percent positivity and serogroup distribution among different sexes and age group of clinically suspected human patients in Chennai (October 2004 to December 2005) and apparently healthy individuals belonging to risk groups (veterinary professionals and conservancy workers). Seroprevalence in various animal species screened in Tamil Nadu during (April 2004 and March 2006) are also furnished. Serum samples (human and animal) and screening by microscopic agglutination test (MAT) Screening of human and animal serum samples was conducted at Leptospira Research Laboratory using microscopic agglutination test.[18] Reference Leptospira interrogans strains belonging to Australis, Autumnalis, Ballum, Canicola, Grippotyphosa, Sejroe, Hebdomadis, Icterohaemorrhagiae, Javanica, Pomona, Pyrogenes and Tarassovi serogroups were obtained from the Regional Reference Laboratory, (ICMR) andaman and Nicobar Islands. Serum from clinically suspected human patients (N=67013), from various parts of Chennai received between 1997 and 2006 showed 57.55% seropositivity. Samples received between April 2003 and March 2006 (N= 25, 449) were used to study the distribution of serogroups and prevalence trend studies, while samples from October 2004 to December 2004 were used to study the disease-distribution with reference to sex and age. Serum samples from apparently healthy human subjects belonging to two risk groups were screened. Group 1 comprised of 37 veterinary doctors and 76 supportive staff from Cuddalore district, a coastal area south of Chennai and Group 2 comprised of 151 conservancy workers in Coimbatore district, located in the western border of Tamil Nadu. Serum samples from domesticated animals (671 cattle, 219 buffaloes, 151 sheep, 144 goats, 62 pigs, 241 dogs, 1 cat and 4 horses), wild animals in captivity (8 elephants, 5 lions, 2 each jackal and bonnet macaque, one each long tailed macaque, spotted deer and barking deer, panther and 27 rodents- Rattus rattus ) were analyzed. Seroprevalence analysis Overall seropositivity by MAT in human samples was found to be 57.55%; highest (78.70%) during 1998-1999 and lowest (32.82%) in 2002-2003. Number of specimens received increased from 2054 in 1997-1998 to 10, 014 in 2005-2006. This reflected on the increased awareness about the disease. Analysis of the 25, 449 serum samples received between April 2003 and March 2006 showed that the seropositivity during the three years was found to be 43.16%, 60.89% and 67.62% respectively. The seropositivity during 2003 - 2004 was less when compared to the subsequent years, which may be due to failure in monsoon and the increase in 2004-2005 and 2005-2006 may be due to the Tsunami and heavy floods in Tamil Nadu. Seroprevalence of different serogroups Seropositivity was seen to all the 12 serogroups tested in MAT. During 2003-2004, Hebdomadis (19.71%) was predominant followed by Australis (19.39%), Javanica (18.06%) and Grippotyphosa (16.42%). During 2004-2005, Australis (21.67%) was predominant followed by Pyrogenes (13.95%), Grippotyphosa (12.28%), Autumnalis (9.53%) and Hebdomadis (8.41%). During 2005-2006, Australis was highly prevalent (57.36%) followed by Pyrogenes (7.84%), Canicola (7.53%) and Hebdomadis (7.22%). During this study, Australis was more prevalent as compared to Autumnalis that was predominant during 1990′s.[7],[15] Similar observations were made in cattle and pigs in Primorskii Krai, a far eastern part of the Soviet Union.[19] Their seroprevalence data comparing that of 1980 with that of 1961-1973, showed that among cattle, there was a significant increase in the sero- converters for Pomona (15.26%) Tarassovi (8.05%) and Javanica (3.14%) and decline in serogroup Hebdomadis. Among pigs, seroconverters to Pomona and Tarassovi, which were 39.92% and 26.47% between 1961 and 1973, changed to 99.64% and 0.36% respectively during 1980. Gender and age wise seroprevalence Samples received between October 2004 and December 2004 (N=2169) indicated that the seroprevalence was found to be more in males (859/1499; 57.30 %) than in females (640/1499; 42.70%). In the age-group analysis, five age groups were made separately for males and females; up to 5 years, 5-10 years, 10-20 years, 20-40 years and above 40 years. The seropositivity distribution for the above groups within positives were 11.41%, 12.11%, 18.16%, 40.16% and 18.16% among male patients and 11.25%, 11.56%, 17.19%, 34.84% and 25.16% among female patients. The mean seropositivity was found to be more in patients above 20 years of age in both sexes. Such information on human population in Tamil Nadu was not available from the literature screened. However, percent positivity was positively correlated in clinically suspected dairy cattle[11] and dogs[12] Seroprevalence among risk groups Group 1 consisting of 103 Veterinary Department staff, Cuddalore District, Tamil Nadu showed that 2 out of 30 veterinary doctors (1.94%) and 12 out of 73 para-technical supportive staff (11.65%) were seropositive, with an overall seropositivity of 13.59%. They were between the age group of 29-56 years and the percent positivity 13.33% (2/15), 9.30% (4/43) and 17.77% (8/45) were recorded in age groups upto 29-39, 40-49, 50 and above age groups. Seropositivity was observed only among male staff and all the 3 female staff were negative. The serovars included Australis (28.57%), Hebdomadis and Tarassovi (21.43%), Sejroe (14.29%), Autumnalis and Grippotyphosa (7.14%). In the Group 2 of conservancy staff (N= 151) in Coimbatore District, Tamil Nadu, the overall seropositivity was 12.58% with males being 15/113 (13.27%) and females showing 4/38 (10.52%). 11 out of 19 (57.89%) was Australis, 3/19 (15.79%) Javanica and the rest included onecase each of Autumnalis, Canicola, Icterohaemorrhagiae, Pyrogenes and Tarassovi. Earlier studies[15],[16] showed the seroprevalence among urban population included 33.9% in Madurai comprising of people of different occupations, 24.8% among conservancy workers in Madras, 17.6% and 25.2% among agricultural workers in Cumbum and Bodi. But it is notable that the seroprevalence among industrial workers of Madras city was relatively low (8.7%). Sero-prevalence among rice mill workers in Salem District was high (68.30%; 78/532). Seroprevalence among animals Seropositivity was 57.47% among domestic animals and 72.73% in wild animals in captivity and 37.03% in rodents with an overall percent positivity of 56.68% was seen. Among domestic animals, Australis was 20.28% followed by the other serovars; Hebdomadis (14.31%), Sejroe (12.85%), Pomona (12.51%), Pyrogenes (8.23%), Tarassovi (7.89%), Autumnalis (6.42%), Canicola (5.41%), Ballum (4.28%), Icterohaemorrhagiae (3.72%), Grippotyphosa (2.37%) and Javanica (1.75%). Among wild animals in captivity, Tarassovi was 30.43% with the other serovars being Javanica (26.09%), Pyrogenes (17.39%), Australis (8.69%) and Sejroe, Hebdomadis, Icterohaemorrhagiae and Pomona (4.35%). This frequency to serogroups among rodents (Rattus rattus ) was found to be Australis and Icterohaemorrhagiae (22.73%), Javanica (18.18%), Autumnalis (13.64%), Canicola and Pomona (9.09%) and Grippotyphosa (4.55%). Conclusions In this study, it was concluded that Australis was the most predominant serogroup among humans and animals in Tamil Nadu during this study period. This study however, is based on MAT and conclusive data can only be obtained by isolation and typing of the different serovars. References
Copyright 2006 - Indian Journal of Medical Microbiology |
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