Introduction

Hydatidosis, one of the most important and a silent cyclozoonotic infection of global dimension caused by the larval stages of the dog tapeworm, Echinococcus granulosus.The direct economic relevance lies on the involvement of visceral organs by the slow growing cyst resulting in the condemnation of meat/carcass and thereby huge loss to meat industry due to subsequent restriction in the export of meat and meat products. This cyclozoonotic disease still remains a challenge to clinical medicine as the cysts are not be traced easily and pose serious entity as silent killer and public health  problem in many developing countries ( Erman et al., 2001; McManus et al.,  2003 and Samanta et al.,  2009). About 4 million people are estimated to be infected and other 40 million at risk (Aziz et al., 2011). Recently WHO has put hydatidosis as an important neglected zoonosis sub-group for its 2008-2015 strategic plans devoted to the control programme (Siracusano et al., 2012).

The Indian sub-continent is considered paradise of parasites and provides ideal conditions for the establishment, propagation and dissemination of hydatidosis both in humans (Sarma et al., 2000) and livestock (Gupta et al., 2011). The prevalence rate of hydatidosis varies from different parts of India in various food animals. The significance and control strategies for this silent cyclozoonosis were discussed by Samanta (2008). Although significant progress has been achieved in research on hydatidosis, but still there are no routine, reliable methods for diagnosis or surveillance and monitoring of the hydatid infection in living animals (Samanta et al., 2003). Through the detection of cysts during meat inspection or at post-mortem examination still remains the most reliable method. The present paper envisaged on some of the epidemiological studies on hydatidosis in buffaloes since only a clear picture can address the issues and therefore an efficient and sustained control programme can be implemented.

Materials and Methods

Study Area

The investigation was carried out in and around Bareilly district which is located in the state of Uttar Pradesh in the northern part of India. It is situated on the side of the river Ramganga (a tributary of the river Ganges), 243 km west of Lucknow, the capital city of Uttar Pradesh, and 254 km east of Delhi, the capital of India. The exact geographical location of the Bareilly District is between latitude 28.36 east and longitude 79.43 north. The climate is hot, humid subtropical, however, the winters are bit cold, with a temperature ranging from 4 to 15 C and the annual rainfall is around 500–700 mm. The buffalo slaughter house at Bareilly was regularly visited to screen the slaughtered animals for the presence and distribution of hydatid cysts in different organs along with recording of age and sex of animals. About 50-100 buffaloes were slaughtered every day.

Study Period

The present investigation was carried out for whole year from July, 2014 to June 2015. Seasons throughout the year study, were divided mainly into four seasons namely, summer (April to June), monsoon (July to Sep.), autumn (Oct. to Dec) and winter (Jan. to March). Age and sex of the animals were recorded before the slaughter of the animal.

Collection of Samples

The hydatid cysts were collected from local slaughter house of Bareilly. Inspections were done on different visceral organs such as lungs, liver, spleen, kidney and heart. Slaughtered buffaloes were thoroughly screened by palpation of these organs, especially the lungs and by making parallel cuts in the organs for the presence of the cysts, if any. The collected cysts were brought in a cool boxes containing ice to the lab separating according to sex and age of animal.

Processing of Samples

The collected cysts (n- 155) were washed with sterile PBS (pH-7.2) two times and the tissue surrounding the cyst was teased apart with a sterile scissor and the hydatid cyst was taken out. For the fertility status , the fluid was aspirated with sterile syringe aseptically and collected in   50 ml vials separately  for each cyst and centrifuged at 6000 rpm for 10 min. at 4°C  for the presence of protoscolices macroscopically as well as microscopically and classified in to fertile and sterile cysts accordingly. The sterile cysts usually had transparent membrane while as membrane of fertile cysts was thicker, more laminated and grayish to yellowish in colour. By visual inspection (white caseous plaques) and microscopical examination, the calcified cysts were determined. Size of the cyst was determined by measuring the circumference of the individual cyst by thread and the diameter was calculated and the size of the cyst expressed by diameter for record.

Results and Discussion

In order to know the prevalence of hydatidosis in buffaloes in and around Bareilly, a total of 1046 buffaloes were screened at the slaughter house for the presence of hydatid cysts located in different organs and their size and nature of the cysts with some epidemiological determinants such as age and sex of the animal along with seasonal effect. In our present study, out of 1046 buffaloes, 155 buffaloes were found to be positive for the presence of hydatid cysts, with an overall prevalence of 14.82% in buffaloes (Table 1) irrespective of age, sex and season. Higher prevalence was reported as 48% from north India by Singh et al (1989) , 34.5% from Bikaner, Rajasthan by  Khan and Purohit, (2006), 23.53% by Verma and Swamy (2009) and 50.96% from Chandigarh by  Arif et al. (2015 ) in slaughtered buffaloes from different parts of India. However, a lower prevalence rate of 6.52% from North East  by Kumar et al. (2008),  5.1% from Maharashtra by  Pednekar et al. (2009), 11.2% from Punjab by Jadhav and Satapathy (2013) and 2.90% from Mumbai by Ghodake et al. (2014). Variation in the prevalence rate in different parts of India might be due to multiple factors such as study design, host, agent, environmental and social factors often contributing to regional peculiarities in the pattern of many aspects of the disease including the prevalence rate.

Table 1: Prevalence of hydatid cysts in buffaloes (age and sex wise)

The prevalence rate among different age groups was found to be 6.8% (5.65% males; 8.6% , females) below 3 years of age and 14.97% ( 14.2% males ; 17.05% females) between 3- 5 year age group while as 17.46% (16.35% males ;17.46% females) above 5 years of age (Table 1). Our present study revealed higher infection rate with the increase in age of the animals which is in consonance with the report of Khan et al (2013) who found 3.52% in calves less than 2 years, 5.58% in 2-3 year and 54% in adults above 3 years of age, Khan and Purohit (2006) who reported 11.1% in younger and 43.6% in older animals. A prevalence of cysts higher in adults than calves was also documented by Gupta et al. (2011). The present findings revealed that age might be a significant factor on the prevalence and dissemination of hydatidosis. The infection is more prevalent in older animals as the cyst develops slowly over longer period, always a higher infection rate can be expected in older animals than the younger animals. Moreover, the infection has cumulative effect on the animal as the animal grows older and exposure to repeated infection increases. From the observation, it may be suggested that the slaughtering of food animals at an early age may considerably reduce the infection in intermediate hosts as well as in dogs.

The overall prevalence rate in males was found to be 13.92% while as in females it was found to be 16.6%. Our present study showed slightly higher prevalence in females than males as reported by earlier workers like Khan and Purohit (2006) who reported 40.9% in males and 44.1% in females from Bikaner, Khanmohammadi et al. (2008) who reported 22.36% of males and 26.49% of females whereas Lahmer et al. (1999) observed a higher prevalence in males (44.8%) than in females (25.2%). The slightly higher prevalence in females may be due to their physiological and hormonal effects.

Seasonal variation in prevalence rate was not found to be of much effect (Table 2).  Prevalence of hydatidosis in different seasons was recorded as 16.08% in summer (37 out of 230), 12.89%   in monsoon (33 out of 256), 17.015% in autumn (41 out of 241) and 13.795% in winter (44 out of 319). From these results no trends of seasonal effect has been assessed. Similar findings were recorded by Khanmohammadi et al. (2008) who reported 30% in spring and in winter 24.51%. Our study also did not show any significant variation in the seasonal prevalence which is contrary to the findings of Arif et al. (2015) who reported  higher occurrence in winter (54.28%) season than in other seasons (summer, 21.92%; spring. 28.14%; autumn, 20.92%) . No seasonal variations in the present study may be due to the fact that once the cyst developed is persisted for long period even throughout life unless caseation occurs. Therefore, when the cyst develops in one season can be persisted in other seasons also. So season does not show any orderly increase or decrease in prevalence rates as seen in trematodes like Fasciola spp., Schistosoma spp. etc.

Table 2: Seasonal prevalence of hydatidosis in buffaloes

Out of the 155 hydatid positive animals, 99 (63.87%) animals harboured hydatid cysts in lungs only, 24 (15.48%) in liver only and 30 (19.35%) involved both lungs and liver (Table 3). Thereby the cumulative incidence was observed for pulmonary hydatidosis (83.2%) against hepatic hydatidosis (34.8%).This indicates that lungs and liver are the predominant sites for the hydatid cyst development. However lung involvement  was seen higher than the liver which corroborates with the findings of  Sundaram and Natarajan (1960); Pednekar et al. (2009) ; Gupta et al. (2011);  Sangaran and Arunkumar ( 2013) and  Arif et al. (2015) who also have recorded higher incidence of pulmonary than hepatic hydatidosis. However, on the contrary, more liver involvement as compared to lungs was also reported Esatgil et al. (2007) and Jadhav and Satapathy (2013). Many a times cysts in lungs may be missed during inspection as the presence of cysts in lungs are not easily perceptible until palpation of lungs; however, in liver the cysts are clearly visible whether it is minute or large. The involvement of other organs was very less as compared to lungs and liver. Spleen and kidney involvement was observed in only one case each with a prevalence rate of 0.645%.  No cyst was found in the heart during the entire study period. This study is in consonance with earlier ones carried out by Singh et al., 1988, who reported 60% in lungs and 32% in liver 4% in spleen and 2% in kidneys in buffaloes. Among these organs, heavily infected lungs are often thrown out by butcher and stray dogs in the vicinity of the slaughter house may get the readymade infection from the offal’s especially from lungs. Therefore, infected lungs seem to be a potential threat in spreading infection.

Table 3: Location of hydatid cysts in different organs of buffalo

Out of 155 animals with hydatid cysts, 86 (55.48%) were found to be fertile, 65 (41.93%) were found to be sterile and 4 (2.58%) were found to be calcified (Table 4). Fertility status was reported by Sangaran and Arunkumar (2013) who reported 42.8% fertile; 61.03% sterile where as  Endalew and Nuradddis(2013)  reported 16.9% fertile and  55.8% sterile,  Arif et al. (2015) reported  37.9% fertile and  62% sterile in buffalo heifers. Since lungs were more infected in the present study, simultaneously the fertility rate was also on higher side which is in agreement of the findings of  Arif et al. (2015) who had shown that percentage of fertile cysts obtained more from lungs (88.23% in adult males).

The fertility status indicates the potential of dissemination of infection in definitive host and subsequently to the food animals. Regional peculiarities in several epidemiological factors viz, host, agent, environment, socio-economic and cultural phenomenon of the region, warrants identification of specific risk factors to deal with composite manner for food security and betterment of health and production.

Table 4: Nature of hydatid cysts in hydatid positive animals (n=155)

Conclusion

The present study shows an overall prevalence of hydatidosis in buffaloes as 14.82% in Bareilly region. Age has significant effect on infection rate as the nature of hydatidosis is progressive and cumulative. Older animals show higher prevalencethan younger ones. However season doesn’t show any significant effect because cysts survive inside body for years together once animal gets infection. Females (16.6%) show higher prevalence than males (13.92%) which may be due to physiological differences and hormonal stress associated with pregnancy and lactation. Slaughter of animals at younger age may considerably reduce the infection rate in both domestic animals and dogs as well. Furthermore, mainly lungs and livers need to be carefully examined on postmortem as these two organs predominantly harbour cysts. Palpation of lungs is necessary as smaller cysts may easily get missed during routine examination which helps in perpetuation of cycle. Sanitary measures need to be strengthened at all slaughter houses, along with proper disposal of carcass can go a long way in reducing prevalence of disease.

Acknowledgement

The authors are highly thankful to director Indian Veterinary Research Institute, Izatnagar, Uttar Pradesh, India for providing facilities and support to carry out the research work.

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