Preliminary study on the status of feline leptospirosis in Kerala #

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Leptospirosis is a disease of zoonotic importance in the worldwide scenario and is caused by the infection of Leptospira species.It is reported in more than 150 species of mammals and identified to have more than 300 serovars (Picardeau, 2017).The spread of disease occurs as a result of contact with water contaminated with bacteria or contaminated urine.The transmission of disease in human beings occurs as a result of animal source or due to the recreational activities  *Corresponding author : snehalekshmia1994@gmail.com, Ph. 9495112826 engaged in contaminated water (Murillo et al., 2020).Rats are considered to be primary reservoirs for the infection and other mammals such as cattle, sheep, pigs, dogs and cats can also transmit the disease.To offer a rapid diagnosis in case of acute infection PCR can be used as a powerful tool meanwhile, MAT is recommended to identify infecting serovars of Leptospira species (Chandran et al., 2019).
The seroprevalence of leptospirosis varies according to geographical regions from 4.8 to 35 percent (Murillo et al., 2020;Spribler et al., 2019;Rodriguez et al., 2014;Mylonakis et al., 2009).Although the infection in cats has been demonstrated and has the ability to develop antibodies, studies on feline leptospirosis are rare.Hence the study was undertaken to assess seroprevalence of feline leptospirosis in Kerala.
A total of 200 serum samples were collected randomly from apparently healthy cats from different parts of Kerala such as Thiruvananthapuram, Kollam, Alappuzha, Pathanamthitta, Kottayam, Thrissur, Ernakulam, Malappuram, Kozhikode, Wayanad, and Kannur during the period from December, 2021 to November, 2022.Epidemiological data such as age, sex, breed, housing environment, presence of other animals in the housing, and whether animals had access to rodents or not were also collected.The blood samples were collected in 5 ml clot activator vials for serum separation.Immediately after receipt, samples were centrifuged and sera samples were stored in -20°C.
In the first step, 1:20 serum dilutions were prepared in PBS, 50 μL of which was taken and mixed with 50μL of each of the four to six days old live leptospiral serovars separately.Antigen controls were set with 50 μL PBS and 50 μL of different live leptospiral serovars and the plates were incubated at 37°C for two hours.After incubation, the result was read by examining a drop of serum-antigen mixture from each well under the 10X objective of DFM for agglutination of leptospires.
Samples positive at 1:20 dilution were again serially diluted up to 1:400.The combination at which 50 per cent or more leptospiral organisms were seen agglutinated was taken as positive.In the case of samples showing agglutination against more than one serovar, the reacting at the highest titre was presumed to be the infecting serovar.Sera samples show the same agglutination titres to more than one serovar were considered as mixed equals.
In the study, serum samples from apparently healthy 200 cats were collected from different parts of Kerala and among them, 12 showed seropositivity (6 per cent).This finding is in agreement with Murillo et al. (2020) who observed a seropositivity of 4.1 per cent in cats in Spain and most common serovar identified was serovar Cynopteri.Contrary to this finding, Lapointe et al. (2013) reported that 25 per cent of cats in Canada tested were seropositive by MAT and all the cats were positive for serovar Bratislava.Kakita et al. (2021) detected leptospiral antibodies in 16.6 per cent of cats tested in Japan and the predominant serovar was Javanica.Antibodies against Leptospira serovars Poi, Bratislava, Arborea, Ballum, Pomona and Lora were detected in 15.3 per cent of cats in Southern Italy.Among 12 samples two samples had mixed infection with two serovars and one sample had mixed infection with three serovars.Out of 12 samples, six samples (50 %) showed seropositivity to serovar Djasiman followed by serovar Autumnalis (25%) then followed by serovar Icterohaemorrhagiae (16.66 %) and serovar Australis, Grippotyphosa and Hardjo each of 8.33 %.The major serovar observed was Djasiman followed by Autumnalis, Icterohaemorrhagiae. Least were Australis, Grippotyphosa and Hardjo.
In the present study, six per cent of apparently healthy cats, in Kerala, showed seropositivity for leptospirosis which is in agreement with previous studies where seroprevalence for leptospirosis in cats ranged from 4 to 33.3 per cent in different geographical areas (Murillo et al., 2020;Sprißler et al., 2019;Rodriguez et al., 2014;Mylonakis et al., 2009).Studies on seroprevalence study of leptospirosis in cats in Kerala are scarce.Divya et al. (2021) reported that one out of 11 cats tested by MAT was positive for the serovar Sejroe.One study regarding the seroprevalence of Leptospira spp. in India which was conducted in Salem district of Tamil Nadu by Natarajaseenivasan et al. (2002) reported that six out of nine cats had antibodies to leptospira tested by MAT and also showed high seroprevalence in rice mill workers.
In the present study, 41.6 per cent of seropositive cats were under one year of age and 58.33 per cent were in age group between one and two years (Dorsch et al 2020).The present study showed that 41.6 per cent of seropositive cats were females and 58.33 per cent were males.In breed-wise classification, 66.66 per cent of seropositive cats were cross bred and the remaining were Persian cats.The housing condition of animals showed that 25 per cent of seropositive cats are reared exclusively indoor and 25 per cent of seropositive cats are reared exclusively outdoors and the majority (50 %) have both indoor and outdoor access (Rodriguez et al., 2014;Lehtla et al., 2022).When the presence of other animals or rodent status was considered, all seropositive animals, except one had the presence of at least one animal in the house or surroundings such as dogs, cats (Donato et al., 2022), and cattle (Ojeda et al., 2018).A study conducted in Chile by Azocar-Aedo et al. (2014) observed that contact of cats with livestock animals was significantly associated with the presence of Leptospira spp.antibodies and a study done on 90 asymptomatic cattle in the Alappuzha district revealed that 47 among them were seropositive which indicated that cattle can transmit the disease and can act as an asymptomatic carrier of the disease (Sreekutty et al., 2020).

table 1 .
., Details of leptospira seropositive cats by MAT