Seroepidemiological Pattern of Leptospirosis in Bovine of South Gujarat, India

Aim: Seroepidemiological study of leptospirosis in cattle of various South Gujarat district (Navsari, Tapi, Surat, Valsad). Materials and Methods: Whole blood samples were collected randomly from different age groups, and breeds of cattle of either sex reared in different districts (Navsari, Surat, Tapi, Valsad) of South Gujarat. To obtain serum, whole blood was kept in slanting position in 9.0 ml plain vacutainers until serum extracted out of the whole blood. Then these 9.0 ml plain vacutainers were centrifuged at 7000 rpm for 10 min. The straw colored serum was then collected in 1.5 ml sterile cryo vials and aliquoted and stored at −20°C for microscopic agglutination test./121) among cattle. The seroprevalence rate of breed and sex wise did not differ significantly (p≤0.05). Maximum incidence of seropositivity was found above 4 years (16.32%, 39/239) of age group followed by animals between 1 and 4 years (9.68%, 12/124). Thus, the age was significantly influencing the seropositivity (p≤0.05). In cattle out of 398 sera screened, 51 were positive with one or more serovars. The highest seropositivity was recorded against serovar Pomona (28.89%). Conclusions: Overall 12.81% seroprevalence of leptospirosis in apparently healthy and clinically ailing bovine of South Gujarat indicating potential zoonotic risk to farmers, labor, and animal owners.


Introduction
Leptospirosis is worldwide distribution and occurs in man, cattle, buffaloes, pig, sheep, goat, dog, horse, etc. Due to its zoonotic nature, it is communicable from man to animals and vice versa.The earliest recorded outbreak of leptospirosis in India was reported among construction workers in the village of South Andaman in 1929 and was named as Andaman hemorrhagic fever [1].It is still of common occurrences in South and North Andaman.
In Gujarat, the disease reemerged in Surat district during 1997/1998.In the year 2005, the disease was noted in 392 persons and deaths occurred in 81 patients due to leptospirosis from various districts of South Gujarat.Since then, cases of leptospirosis were very often reported from Navsari, Valsad, and Surat districts [2].In neighboring state of Maharashtra, similar episodes have often been reported during postflood period especially in Mumbai [3,4].
Hence, it is very necessary to know the present status of bovine leptospirosis in the South Gujarat.The present study was planned to study seroepidemiogical pattern of leptospirosis among cattle in this region of Gujarat.

Ethical approval
The experiment was carried out according to the protocol of Institutional Animal Ethics Committee and the authors were permitted by animal owners for sampling.

Samples
A materials comprise whole blood/serum were collected randomly from different age groups and breeds of cattle (n=398) of either sex reared in different districts (Navsari, Surat, Tapi, Valsad) of South Gujarat (Tables-1-3).Whole blood samples were collected from the jugular vein of cattle in sterile 9.0 ml plain vacutainers.To obtain serum, whole blood was kept in slanting position in 9.0 ml plain vacutainers until serum extracted out of the whole blood.Then these 9.0 ml plain vacutainers were centrifuged at 7000 rpm for 10 min.The straw colored serum was collected in 1.5 ml sterile cryo vials and aliquoted and stored at −20°C for future use.

Statistical analysis
Chi-square test was used according to Web Agri Stat Package software developed by Jangam and Wadekar, ICAR research complex, Goa for statistical analysis of data [8].

Results and Discussion
The details of district, breed, sex, and age wise results of seroprevalence in cattle are given in Table 4.
District-wise (Navsari, Surat, Tapi, and Valsad) seroprevalence rate of occurrence revealed that the presence of leptospiral antibodies differed significantly (p≤0.05)among the districts.The highest  [22] and Agrawal et al. [23] opined that indigenous breeds are more susceptible than crossbreds and our present observations supported their finding.Contrary to this Balakrishnan et al. [24] noted that exotic pure breeds are more susceptible followed by indigenous pure breeds and cross breeds.They further mentioned that both HF and Jersey are equally susceptible to leptospirosis.Among Indian breeds, Red Sindhi was the most susceptible (66.66%) followed by Gir (40.00%),Kankrej (27.27%) and Sahiwal (25.00%).Thus, there appears to be the absence of unanimity in the literature about breed susceptibility.
Sex-wise seroprevalence in cattle did not differ significantly (p≤0.05)though the females showed higher seroprevalence (13.22%, 48/363) in comparison to male (8.57%, 3/35).This could possibly be due to number of sample tested from male and female cattle and supported the observations of Ramin and Azizzadeh [25] and Shafighi et al. [16] who too did not observed any sex bias in respect of seropositivity.Contrary to the above observations Mandal et al. [13] and Balakrishnan et al. [24] noted higher seropositivity in males than female cows/heifer.
Sera were tested from the cattle of three age groups viz., below 1 year, 1-4 years and above 4 years.Maximum incidence of seropositivity was found in cattle of above 4 years (16.32%,39/239) of age group followed by animals between 1 and 4 years (9.68%, 12/124).None of the cattle below 1 year showed seropositivity.Thus, age was significantly influencing the seropositivity (p≤0.05).These findings indicated that increasing age of cattle makes them more prone to leptospiral infection and supported the findings of Kocabiyik and Cetin (2004) who also opined that seropositivity markedly increase with age and Balakrishnan et al. (2011) mentioned that seropositivity was comparatively higher in the cattle of above 4 years of age.Contrary to this, Agrawal et al. (2005) studied the seroprevalence in cattle, buffaloes and goats and reported that the seropositivity among cattle of 6-8 year age was 10% which decreased to 3% at the age of above 9 years.
In the present study, the most prevalent serovar was Pomona (28.89%) as against earlier observations made by Balakrishnan et al. [24] from this region who noted Serovar Hardjo to be most prevalent among cattle.In addition a number of serovars from time to time were reported from other states of India such as serovars Hardjo, Bataviae, Canicola, and Australis from West Bengal [13], Grippotyphosa, Pomona and ictrohemorhagiae from Andaman and Nicobar [22], Pomona, Hebdomandis, Medanensis, Hardjo, Andamana and Saxkoebing from Andhra Pradesh [26,27], Icterohaemorrhagiae and Grippotyphosa from Uttar Pradesh [28].

Conclusions
Seroepidemiological study of leptospirosis in South Gujarat region revealed that this region is endemic for leptospirosis.It's prevalence in apparently healthy and clinically ailing bovine irrespective of breed, age, and sex indicating potential zoonotic risk.This study also determines the need for continuous monitoring of leptospirosis in animal and humans to combat this zoonotic infection.

Table - 1
: Details of age-wise sample collection in cattle.

Table - 2
: Details of breed-wise sample collection in cattle.

Table - 3
: Details of districts and sex-wise sample collection in cattle.

Table - 5
: Leptospiral serovar distribution in cattle of South Gujarat.
Surat, NIVEDI=National Institute of Veterinary Epidemiology and Disease Informatics, Bengaluru, NT=Not tested