Prevalence of HCV among the Irula tribes
Hepatitis C infection is a major cause of chronic liver disease, with >185 million infection worldwide. HCV infection is chronic in 75% to 85% of infected individuals [12]. An estimate of approximately a quarter of a million deaths occur per annum due to chronic liver disease associated with HCV [13]. Epidemiological burden of HCV infection varies throughout the world, with country-specific prevalence ranging from1% to 10% and population based anti-HCV prevalence is important for the surveillance purposes as it provides an insight in to the burden of diseases [14].

Of the 372 samples included in this study, 19 samples are positive for anti-HCV antibodies with a prevalence of 5.10%, which is high, compared to the other reports. None of them (0.00%) are positive in Kolli hill tribes (9), 2.97%  and 2.25%is observed in East and  Northern region of India [15,16], none of them are found positive in tribal population in southern region of India and 0.3 % is positive in general population of Southern region of India [17].

Age wise prevalence of HCV among Irula tribes
There are both geographic and temporal differences in the patterns of HCV infection found in all over the world [18]. United States, Turkey, Spain, Italy and Japan has the similar and over all prevalence of HCV infection (1.0% – 1.9%) but have different patterns of age-specific prevalence will varies. In the United States, prevalence of HCV infection is highest among the persons who are 30-49 years old and lower than average among the persons less than 20 and greater than 50 years old [19]. In contrast, some countries like Egypt, Japan, China and most of the African countries, there is a high prevalence of HCV infection predominantly appeared in younger population [20]. And also in some states of India, high prevalence of HCV infection found on the age group of 20 to 30 years old [21].

Likewise, in the study, it is observed that the Irula tribal people had infection more prevalent in the middle age group 31 to 40 and followed by 21 to 30.  There is a sharp peak of HCV infection is found on the age group of 31 to 40 (10.75 %) years and a substantial prevalence till 60 years.

Gender wise prevalence of HCV among Irula tribes
Other than being a population based prevalence study, there are some special characteristics from the study which should be noted. The study compose of more number of females than the males, whereas many other previous studies have accounted almost exclusively on males, this is particularly tribals, general populations, blood donors and hospital based studies where the female population has always been much lesser than males [15,22,23]. High prevalence of HCV among males has also been reported in a study conducted among the tribals of North East India [24]. In contrast, the prevalence of Hepatitis C infection higher among Females (5.51 %) than males (4.23 %) of Irula tribal peoples.

Risk factors
The factors associated with HCV infection have been identified in this study; very few studies only in India have studied these factors. It is assumed that temporal association between the risk factors such as history of jaundice, jaundice in family, alcoholism, tattooing, and surgery with blood transfusion, surgery without blood transfusion, intravenous drug use, and series of injection, sexual promiscuity and migration.

Because of more variety of human activities that involve the potential for percutaneous exposure to blood or blood derived body fluids, there are numerous other biologically plausible modes of transmissions besides those with clearly demonstrated epidemiologic associations with infection. These include cosmetic procedures (tattooing, body piercing), intravenous drug use and religious or cultural practices such as ritual scarification, circumcision. In worldwide, there are insufficient data to determine whether these risk factors make any measurable contribution to the overall HCV transmission [21].

In the study, it is found that in Irula tribal population tattooing, surgery with blood transfusion and without transfusion, sexual promiscuity, series of injection, migration, jaundice in family and Intravenous drug use are the leading risk factors for HCV and these are statistically significant. History of jaundice and Alcoholism are not statistically associated with HCV but there is a high prevalence in getting infection among the Irula tribes (Table 2).

In the study from Kolli tribal population, none of them are positive for HCV and they could not predict the HCV risk factors and these combinations [8]. But in the present study, among the Irula tribes, A+IDU+SP, (100 %) HJ+A+IDU+SI+M (100%) and HJ+T+S+SP+M (50%) combinations are the highly associated risk patterns for Hepatitis C infection. It shows that every factor has a risk of getting a HCV infection but with combinations of some factors lead to high risk for getting an infection of Hepatitis C (Table 3).

Tattooing
Due to the accidental inoculation of contaminated blood during certain cultural practices like tattooing and piercing can transmit HCV virus. HCV transmission could occur at different stages of tattooing and piercing, from the reuse of non-disposable needles, inappropriate sterilization of equipment, or reuse of ink contaminated with blood from an infected person [25,26]. Risk of HCV infection is significant among the high risk groups when nonsterile tattooing equipment is used, especially in the unregulated settings, such as homes of prison [27,28]. Minor routes of HCV transmission includes multiple uses of unsafe injections and procedures by private practitioners and dental surgeons respectively, sharing of shaving kits and visiting roadside barbers have played an vital role of transmission [21,23].

Surgery with or without blood transfusion
Blood transfusion is an effective mode of transmission of blood-borne infections including Hepatitis C virus. Prior to the introduction of effective screening of blood donors, blood transfusions were recognized as the leading source of HCV infection [29,30].  In 147 Chilean patients with chronic hepatitis C, the most common risk factor was blood transfusion in 54% [31]. In India, transfusion of blood or blood product is considered as the most common route for HCV transmission [32]. In a study from Kolkata confirms that the blood transfusion has the most significant route of HCV transmission [33,34]. Blood transfusion was an important factor for transmission of HCV in hemodialysis patients.

Risk factors such as surgery, with or without blood transfusion were involved in HCV transmission and re-confirms the surgery with blood transfusion around 5.12% and surgery without blood transfusion was 1.85% as the most significant route of HCV transmission among the Irula tribes.

Sexual Promiscuity
HCV infection is transmitted predominantly by the parenteral route. Multiple sexual partners were one of the risk factors for the transmission of HCV and they observed 18.68% of patients had a history of multiple sexual partners. Female partners were highly infected with HIV & HCV controlled infection from their respective spouses [34]. The role of sexual activity in the transmission of HCV remains unclear and NHANESIII (National Health and Nutrition Examination Survey III) study showed that number of sexual partners (OR 2.54 for 249 partners) and age of the first sexual intercourse (OR 2.94) had a significant correlation with HCV Antibody and this has been confirmed in other studies [35]. Likewise, in a study among spouses in Egypt, it was wife to husband transmission was 34% and 10% among women with and without detectable HCV RNA. HCV transmission was estimated from Husband to wife as 3 %. In moreover, 6% was estimated to have contracted HCV from their spouse [36]. The transmission between spouses can only be assumed to be sexual in nature and there was lack of evidence found for sexual transmission of HCV among men who have sex with men [37]. These new evidences supports that sexual transmission of HCV is still rare, but for some reason is higher among those with high risk sexual activity [30]. HCV is mostly transmitted by sexual intercourse when the infected partner is in the early phase of acute infection [21].

In the present study, Irula tribal people are more traditional and religious and most of the participants did not accept to disclose such personal information and very poor response on these questions. From the obtained data, sexual transmission of HCV is observed as 2.77% among these Irula study population.

Intravenous drug abuse
Transmission of Hepatitis C virus has been strongly associated with the intravenous and percutaneous drug and needle use. These injection drug users are at high risk for blood borne infections including HCV virus [38]. In India very few studies are available on the intravenous drug abuse induced HCV infection and the prevalence of HCV antibody was ranging from 5 to 93 % among the intravenous drug users [39,40], 3.85 % of patients had a history of intravenous drug abuse in tertiary care hospital study in Kolkata [34]. Only few data exist regarding the prevalence of injection drug use and its contribution to HCV transmission among Irula tribal people. With the obtained data, it is found that there is high risk of HCV transmission is 12.82 % and occurs in intravenous drug abusers.

Series of Injection
The risk factors revealed that the needle prick or multiple injection, dental procedure and surgery etc., as cause of infection with Hepatitis C virus, among patients under study. This study has found that needle prick (33.3 %) as major risk factor for transmission of HCV. The reuse of disposable syringe and needles were soaking in the boiler or bowl with tepid water is common. The sharing of syringes, reuse of injection accessories, blood transfusions and drug abuse are strongly associated with HCV positivity among injecting and non-injecting drug users [41]. Present study found that series of injection as a major risk factor about 10.27% with HCV positivity among Irula tribal participants.

Migration
Among the many factors contributing to the changing epidemiology of viral hepatitis, the movement of people within and between countries is potentially important one. Migration and disease in today’s context of rapid global migration, there is a potential for any disease to be moved further and faster than previously possible. Despite the fact that viral hepatitis has become a global public health threat, both HBV and HCV have remained neglected and relative to the attention given to HIV and other diseases [42,43]. So is in the case of HCV, millions of migrant workers act as biological transporters. Likewise, from the obtained data about migration is 5.22% and the risk of getting HCV infection via migration is significant route of transmission.

Jaundice in family
The transmission routes of HCV is most common via mucous membrane exposure i.e., sexual or perinatal exposure to high risk body fluids like semen, saliva or cervical secretions. The most infections occur by exposure to infected body fluids through high risk sexual behaviors or injecting drug use [43]. Common modes of transmission in developing countries are perinatal, early childhood infections through close interpersonal contact with the infected household contacts, infected mother from child and infected wife from husband or infected husband to wife [44-46]. The seroprevalence of HCV was higher in the patients 6/25 (24%) who were contact with jaundiced person and the data are statistically significant [47]. Similarly, a study on the frequency of HCV among Irula tribes reported a high prevalence and  the exposure of jaundice in family lead to the transmission of Hepatitis C virus in 16/258 (6.20 %) participants got infected from their family members of Irula tribals.

History of Jaundice
One of the main symptom of Hepatitis C is jaundice, a yellowing of the skin and whites of the eyes occur, they usually appear within two weeks to six months after the exposure. It is possible to have HCV for years or even decades without symptoms [48]. The rate of chronic HCV infection is lower in the patients who develop jaundice or symptoms during the acute onset of HCV infection as compared to those who are without jaundice. In a study of 142 HCV-infected subjects with a history of illicit drug use, subjects with viral clearance were more likely to have the symptoms of jaundice (p=0.03) [49]. In Germany the long-term follow-up study of women infected with contaminated Rh immune globulin exhibited a rate of chronicity in 43% and with the history of jaundice, as compared to 60% among those who remained anicteric (p<0.001). Many have speculated that the jaundice may be associated with a more robust immune Th1 lymphocyte and cytokine response to the HCV [50,51]. In some study conducted in normal population of Tamilnadu state about HCV is not statistically significant with the history of jaundice [17,52]. Furthermore, in the present study explains about the history of jaundice may lead to Hepatitis C infection with the competency of immune response and 8.52% (17/199) had a history of jaundice with the Hepatitis C positivity among Irula tribes.

Alcoholism
The prevalence of anti-HCV antibodies among the alcoholic patients is higher when compared to the general population and the rate seems to vary according to the presence or absence of co-existing liver disease [52]. Regarding the epidemiology of HCV among the alcoholic patients, several studies found a strong association between serum markers for the HCV infection and the presence of parenteral risk factors [17,47,53,54]. High prevalence (15%) of anti-HCV antibodies among the unselected alcoholics consecutively admitted to a detoxification unit and 71% of patients had a serum HCV-RNA detectable by PCR, especially those with the elevated aminotransferases (92%) [55]. In the present study, among Irula tribes 8.90% (17/191) were positive for HCV infection but lacking of the statistical association with HCV (Table 2).