The zone is located in southwestern part of Rajasthan. It stretches between latitude 23°4’ and 27°5’ and longitudes 71°4’ and 74°42’ and is 550 meters above mean sea level. The study area covers all tehsils of Jalore, Pali, parts of Sirohi (Sheoganj and Reodar tehsils) and Jodhpur districts (Luni and Bilara tehsils). The average rainfall of the region varies from 300 to 500 mm and the maximum temperature goes beyond 39.7° during summer and lowers up 5.3° during winter (D.O.A., Govt. of Rajasthan, www. agriculture.rajasthan.gov.in).

A total of 625 faecal samples of dairy animals comprising of native cattle (224), crossbred cattle (184) and buffaloes (217) were collected randomly from the four districts of transitional plain in Luni basin of Rajasthan during winter, summer and rainy seasons from November 2018 to October 2019.The samples were placed in sterile polythene bags and labelled carefully indicating the host’s detail, location and season of collection, kept in a cool transport box and brought to the Laboratory for further examination.

The faecal samples were qualitatively examined by using centrifugal flotation and sedimentation techniques for detection of helminths eggs (Soulsby, 1982) and quantitatively by modified McMaster egg counting technique (Coles et al. 1992). Copro-culture study was also performed to harvest and identify strongyle larvae (Wyk and Mayhew, 2013).

An overall prevalence of 66.88% for GIH infection was recorded during present study which is in compliance with the reports from different states of India viz Maharashtra (Shirale et al., 2008), Madhya Pradesh (Gupta et al., 2012), Tamil Nadu (Vanisri et al., 2016) and from around the world viz Thailand (Yuwajita et al., 2014), Ethopia (Regassa et al., 2006) and Belgium (Agneessens et al., 2000). Contrary to present findings, a comparatively lower prevalence was recorded by Wadhwa et al. (2011) and Monika et al. (2017) from Rajasthan state whereas, a higher prevalence was reported by Singh et al., 2008 and Bushra et al. (2013) from Uttar Pradesh and Kashmir, respectively. The variations in prevalence rate could be attributed to the difference in number of faecal samples examined, period of study and geoclimatic conditions like temperature, rainfall and humidity etc. that affect the survival of infective stage of parasites and intermediate hosts, managemental conditions and deworming practices of the study animals in a region.

Among various helminth infections reported, strongyle types infection (60.00%) showed highest prevalence followed by Strongyloides sp (17.60%), Trichuris sp. (8.16%), amphistomes (5.76%), and Moniezia sp. (4.00%) whereas, meager infection of Capillaria sp. (0.48%) was also reported (Fig. 1). Various parasites reported from dairy animals in the present investigation are in congruence to the previous findings of Wadhwa et al. (2011); Swarnakar et al. (2015); Monika et al. (2017) from various parts of Rajasthan. Similar findings were also reported from Jammu (Singh et al., 2009), Punjab (Haque et al., 2011), Madhya Pradesh (Gupta et al., 2012), Sikkim (Rahman et al., 2012), Meghalaya (Laha et al., 2013) and Kashmir (Bushra et al., 2013). Zaman et al. (2014) and Vanisri et al. (2016) reported higher infection of nematode parasites as compared to trematodes and cestodes which is in agreement with the findings of present study. The high prevalence may be due to favorable climatic conditions, constant exposure of infestation and availability of infective stage larvae on the grazing ground by animals.

Animal type wise analysis revealed highest prevalence in native cattle (76.78%) followed by crossbred cattle (67.93%) and buffaloes (55.76%) (Table 1) with a highly significant difference (p<0.01). Among various infections reported in the study, strongyles was reported as the most dominants infection with the highest prevalence in native cattle is congruent to the previous findings of Chaudhri et al. (2014); Monika et al. (2017). Statistical analysis using multivariate binary logistic regression revealed a negative association in crossbred cattle and buffalo i.e. odd ratio of infection decreased by 0.782 and 0.604 in crossbred cattle and buffalo as compared to native cattle (Table 3). The higher prevalence in native cattle may be attributed to longer periods of communal grazing which increase the chances of exposure to infective stages of parasites along with marginal husbandry care of native cattle as compared to crossbred and buffaloes which are usually stall fed. (Renwal et al., 2017 and Monika et al., 2017).

Seasonal dynamics revealed highly significant difference (p<0.01) with highest prevalence during the rainy season (74.29%) followed by summer (67.77%) and winter (58.00%) seasons (Table 2). Seasonal dynamics of gastrointestinal helminth infections revealed highest prevalence during rainy season (74.29%) which is congruent to the reports of Monika et al. (2017); Choudhary et al. (2018); Gupta et al. (2012) and Singh et al. (2008). Statistical analysis using multivariate binary logistic regression model revealed a positive association in rainy and summer seasons i.e. odd ratio of infections increased by 1.431 and 1.286 during rainy and summer seasons as compared to winter season (Table 3). The highest prevalence in rainy season might be due to more suitable environmental conditions in terms of humidity and temperature for the development of pre-parasitic stages of most of parasitic nematodes, whereas cold and dry climate have destructive effects on the development of the helminthic stages and allow fewer pre infective larvae to reach the infective stage (Soulsby, 1982).

A statistically non-significant difference was reported among four districts with highest prevalence in Sirohi district (74.66%) followed by Jalore (65.90%), Pali (65.51%) and Jodhpur district (61.68%) (Table 2). Statistical analysis divulged a negative association in prevalence among Jalore, Jodhpur and Pali districts as compared to Sirohi district i.e. odd ratio of infection decreased by 0.855, 0.671 and 0.864 in Jalore, Jodhpur and Pali districts respectively (Table 3). The reason behind minute variation may be due to similarity in pasture management, climatic conditions, communal grazing and water sources (Monika et al., 2017; Renwal et al., 2017).

Intensity of the gastrointestinal helminths infections in dairy animals as eggs per gram (epg) were depicted in Table 4. Highest intensity was recorded for native cattle during present study followed by crossbred cattle and buffaloes. Variations may be due to the difference in number of faecal samples examined, period of study and geoclimatic conditions like temperature, rainfall and humidity etc that favor survival of infective stage, managemental condition and deworming practices of the respective study areas. Highest epg was recorded during rainy season in present study which is in compliance with the findings of Choudhary et al. (2018). The reason for high epg during rainy season may be the environmental condition (temperature and humidity) of this region which facilitate the development and survival of the pre-parasitic stages (Durie, 1961), leading to increased parasite burden on host and pasture. Parasite egg and oocyst counts reflect the ability of host to regulate the survival/expulsion, growth, or reproduction of parasites to which it has been exposed (Soulsby, 1982).

Coproculture analysis revealed Haemonchus (34.75%) as predominant species, followed by Oesophagostomum sp. (24.00%), Trichostrongylus sp. (17.25%), Bunostomum sp. (15.00%) and Strongyloides sp. (9.00%). Haemonchus sp. was reported to be highest during rainy season whereas Strongyloides sp., Oesophagostomum sp. and Trichostrongylus sp. were found to be higher during summer season with complete details in table 5. Various researchers in their respective studies on cattle and buffalo population have encountered these nematodes (Monika et al., 2017; Renwal et al., 2017; Choudhary et al., 2018) from Rajasthan and different parts of India (Jithendran and Bhat, 1999; Muraleedharan, 2005).