Aim of Study: Leptospirosis is a bacterial zoonotic disease transmitted through contact with animals that are harbouring leptospira. Knowledge of prevalent leptospira in a particular animal of a particular geographical area is essential to understand the epizootiology of disease, to understand the linkage between circulating serovars in animals and in humans, and to apply appropriate control measures, etc. Material and Methods: Animal samples from different districts of the south Gujarat region received in the Microbiology department during the year of 2020 for the Microscopic agglutination test (MAT) of leptospirosis were included in the study. Results of MAT which was already performed using 12 different serovars were analysed to prevent serovars in a particular animal. Quantitative data were analysed using frequency and percentage. Result: Out of 1406 animal samples, 151 (11 percent) were positive from animals like cows, buffalos, bullocks and goats. More prevalent serovars in cows were L. ictrohemorrahiae (22%), L. hardjo (19%), L. patoc (17%) and L. pyrogen (16%). In buffalo, L. patoc (58%) and L. hardjo (27%) were found. L. hardjo (50%) in bullock and L. automonalis (50%), L. australis (22%) and L. patoc (14%) in goat were found as prevent serovars. Conclusion: Different prevent serovars has been observed in different animals from the different district south Gujarat region which will be helpful to trace the source of infection in human, to apply control measures, to know the epizootiology of disease, for developing strategies in the future during vaccine development with emphasizing more on the prevalent serovars.
Leptospirosis is a globally widespread bacterial zoonosis caused by spirochetes belonging to the genus Leptospira [
Knowledge of prevalent leptospira serovars in particular animals of a particular geographical area is essential to understanding the epizootiology of disease. It would be helpful to understand the linkage between circulating serovars in animals and humans. So, this study was designed with the aim to detect the prevalent leptospira serovar of animals and humans circulating in the South Gujarat region and to decide the strategies to control the burden of leptospirosis disease [
Study Samples: In this retrospective study, a total of 1406 animal serum samples were collected during the year 2020 and stored at −20˚C. The animals included in the present study were from various sources representing the diverse livestock production system e.g. rural subsistence, periurban, semi-commercial and organized commercial dairy farms, where human leptospirosis cases were known to occur. The samples were collected randomly and not on the basis of Leptospirosis, like symptoms or any other indication of the disease. All the collected serum samples were subjected to MAT test for leptospirosis. The study was approved by Human Research Ethics Committee, Government Medical College, Surat, Gujarat for research purposes.
Microscopic Agglutination Tests (MAT): The MAT test was performed using standard procedure [
Preparation of Antigens: A 0.5 ml of each representative strain from the panel of 12 serovars was inoculated into 10 ml of liquid EMJH medium. A loopful of culture was checked under dark field microscopy to confirm the absence of contamination or clumps and the presence of viable leptospires. Incubation was done at 30˚C for five to seven days. Densities of approximately 2 - 3 × 108 leptospira/ml of media were used as an antigen.
Procedure: Doubling dilutions from 1 in 10 to 1 in 640 were prepared by using phosphate buffer saline as a diluent. 50 ul of the specific serovar was added to all the wells. One of the wells included only the antigen without the addition of antibodies and served as the antigen control. The final dilutions after adding the antigen were from 1 in 20 to 1 in 1280. The plates were closed with aluminium foil and incubated at 37˚C for 2 h. The highest serum dilution showing approximately 50% agglutinated leptospires or a reduction in the number of leptospiral cells as compared to the antigen control was taken as endpoint titre. A titre of 1 in 40 or more was considered positive.
District wise analysis is shown in
As shown in
District | Total No of samples | Positive by MAT Number (percentage) | Positive samples/total samples in different animals | |||
---|---|---|---|---|---|---|
Cow | Buffalo | Bullock | Goat | |||
Navsari | 546 | 76 (14%) | 18 (7%) 270 | 2 (3%) 68 | 0 2 | 56 (27%) 206 |
Surat | 105 | 14 (4%) | 8 (11%) 70 | 5 (45%) 11 | 0 0 | 1 (4%) 24 |
Tapi | 330 | 13 (12%) | 2 (1%) 213 | 5 (5%) 107 | 2 (20%) 10 | 2 (100%) 2 |
Valsad | 425 | 50 (12%) | 36 (11%) 325 | 12 (14%) 85 | 2 (13%) 15 | 0 0 |
Total samples | 1406 | 151 (11%) | 64/878 (7%) | 24/271 (9%) | 4/27 (15%) | 59/232 (25%) |
Animal | Total No of samples | Positive by MAT No (percentage) | Different Leptospira Serovars positive by MAT. No (percentage) | |||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
L.australis | L.automonalis | L.canicola | L.hardjo | L.hebdomadis | L.ictrohemorrahiae | L.patoc | L.pyrogen | L.pomona | L.griphotyphosa | |||
Cow | 878 | 64 (7%) | 3 (5%) | 6 (9%) | 3 (5%) | 12 (19%) | 5 (8%) | 14 (22%) | 11 (17%) | 10 (16%) | 0 | 0 |
Buffalo | 271 | 26 (10%) | 0 | 1 (4%) | 1 (4%) | 7 (27%) | 0 | 0 | 15 (58%) | 0 | 0 | 2 (8%) |
Bullock | 27 | 4 (15%) | 0 | 1 (25%) | 0 | 2 (50%) | 0 | 0 | 1 (25%) | 0 | 0 | 0 |
Goat | 232 | 59 (26%) | 13 (22%) | 29 (50%) | 0 | 0 | 0 | 1 (2%) | 8 (14%) | 0 | 3 (5%) | 5 (8%) |
During the year 2020, 1406 animal samples were tested for MAT from the villages of the district of Surat, Navsari, Tapi and Valsad, which had shown seropositivity for MAT test is 11%, 14%, 4% and 12%, respectively. This suggests that Navsari and Valsad areas have higher seropositivity in animals for Leptospirosis. The animal wise analysis had shown that Goat in Navsari, Bullock and buffalo in Valsad, buffalo in Surat and bullock in Tapi are more potential animals in that area for Leptospirosis transmission in between animals and also in humans.
Serovars wise analysis showed that Ictrohemorrahiae, hardjo, patoc and pyrogen in cow, patoc and hardjo in byffalow, hardjo in bullock and automonalis and australis in goat were predominant serovars. The predominant serovars pattern is similar to the studies conducted earlier by Balakrishnan et al. [
Still, there is a scope of test in other domestic and wild animals like pigs, dogs, etc., which may be harbouring the leptospirosis and causing zoonosis. Although there have been studies conducted in different parts of India, it is difficult to assess the true nature of the disease from an epizootiological point, due to inadequate sample size. Continuous observation every year from the same area was not analysed, which can be the future scope of more observation and improvement.
The seroprevalence of leptospirosis among different animals in different districts of South Gujarat was significant. These prevent serovars analyses will be helpful to know the epizootiology of leptospirosis. It is also helpful to trace the source of infection in leptospirosis infected human subjects. Moreover need for control measures can be strategies based on these data. Development of a vaccine against leptospirosis which is a challenging thing can be developed or prioritized for these areas on these prevalent serovars first as compared to focusing on all 20 serogroup or 200 serovars.
The authors declare no conflicts of interest regarding the publication of this paper.
Panwala, T., Mistry, Y. and Mullan, S. (2022) Analysis of Prevalent Leptospira Serovar in Different Animals of South Gujarat Region during the Year of 2020. Advances in Microbiology, 12, 327-332. https://doi.org/10.4236/aim.2022.125023