A total of 415 adult domesticated ruminants, 130 cattle (Bos taurus), 108 buffaloes (Bubalus bubalis), 94 goats (Capra hircus) and 83 sheep (Ovis aries) inhabiting tribal rural areas of southern Rajasthan, India were investigated for evidence of gastrointestinal protozoan and helminthic infections. In southern Rajasthan humid ecosystem is predominant and has number of perennial freshwater bodies. Fresh faecal samples of these animals were examined microscopically by direct wet smear with saline and 1 % Lugol's iodine and formalin ether concentration. Of these 296 (71.32 %) were found to be infected with different species of gastrointestinal parasites. The highest (93.84 %) prevalence of these parasitic infections was found in cattle followed by goats (82.97 %), sheep (55.42 %) and buffaloes (46.29 %). Except cattle no other ruminants revealed protozoan infection. A total 8 species of gastrointestinal parasites were encountered. Among these parasites Fasciola hepatica was the commonest (15.18 %) followed by Haemonchus contortus (11.32 %), Ancylostoma duodenale (10.36 %), Trichuris trichiura (9.15 %), Amphistome species (7.95 %), Moniezia expansa (6.98 %), Strongyloides stercoralis (4.57 %) and Balantidium coli (3.37 %). The prevalence rate of these parasitic infections also varied seasonally. The highest prevalence rate was found in rainy season (84.21 %) followed by winter (73.9 %) and summer (52.8 %). The possible causes for variation in prevalence of parasitic infections are also discussed.

A total of 224 Bhil tribal individuals (115 males and 109 females) of different age groups inhabiting tribal rural areas of Udaipur district of Rajasthan, India were investigated for the prevalence of intestinal parasitic (protozoan and helminths) infections. Fresh stool samples of these tribal subjects were examined microscopically by direct wet smear with saline and 1 % Lugol's iodine and formaline ether concentration. Of these 116 (51.78 %) were found to be infected with diverse species of intestinal parasites. Male individuals showed relatively higher (56.52 %) prevalence of infection as compared to their counterparts (46.78 %). Out of 116 infected tribal subjects, 53 (23.66 %), 33 (14.73 %) and 30 (13.39 %) were infected with protozoan, helminths and mixed (protozoan ? helminths) parasitic infections, respectively. Maximum number of parasitic infections occurred in the age group of 6-10 years (69.23 %) in both sexes. Among the intestinal parasites, Entamoeba histolytica was the commonest (14.73 %) followed by Entamoeba coli (8.92 %), Taenia solium (5.35 %), Ascaris lumbricoides (4.46 %), Hymenolepis nana (2.23 %), Ancylostoma duodenale (0.89 %), Strongyloides stercoralis (0.89 %), Trichuris trichiura (0.44 %) and Hymenolepis diminuta (0.44 %). Data pertaining to distribution of parasite species in different age groups, and variation in prevalence of their infection in relation to age and sex were also analysed statistically and found to be significant. Possible causes for variation in prevalence of protozoan and helminthic infection are discussed.

Comparative histopathological effects were observed on the digestive glands (hepatopancreas) of freshwater snail species, Vivipara bengalensis and Lymnaea acuminata infected with single (furcocercous cercariae) and double infection of digenean trematode larvae (gymnocephalous cercariae + metacercariae), respectively. Digestive glands of both the snail species revealed degenerative changes in their digestive gland tubules. The latter became irregular in shape, reduced in size with enlarged lumen and inter-tubular space besides rupturing of digestive tubules. These changes were correlated with the size and types of trematode larvae, single or double infection and degree of parasitemia. Autolytic necrosis of numerous tubules was found in digestive glands infected with double and very severe single infection. None of the tubules was found to be invaded by sporocyst, redia and cercaria. However, metacercariae were seen to invade digestive tubules of Lymnaea species.

During the survey of freshwater snail hosts and their digenean larval trematode parasites, a rare cercaria larva belonging to family Transversotrematidae and subclass Digenea (Trematoda) was recovered from the snail species inhabiting perennial Som river of Udaipur district, Rajasthan, India. More than 28 % mature specimens of these snails were found to be infected with transversotrematid cercaria larvae in the spring season. Body of this cercaria is large, bowl-shaped, biocellate, spinose, transparent and laterally extended having two pigmented eye spots, two hold fast organs extended from the junction of body and tail, large tail with two foliated furcal rami, and cyclocoel intestinal caeca. As far as the authors are aware, this is the first record of a transversotrematid larva from Rajasthan, India. Simultaneously, other forms of cercariae viz., amphistome, echinostome, monostome, gymnocephalous, furcocercous and xiphidiocercous cercariae were also recovered from fifteen species of pulmonate and operculate snails including f., . f. ,. f., . f. ,. f., . f. . f. , () , and () ,, () , () ,, race and . race . The seasonal occurrence and host-specificity of diverse trematode cercaria larvae are also discussed besides the first record of a rare transversotrematid cercaria larva from Rajasthan, India.