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The seasonal activity of ticks on sheep and goat populations was examined from December 2000 to November 2001 in the state of Tamil Nadu, India. This longitudinal study spread over four seasons and seven agroclimatic zones took into consideration the spectrum of species involved, the levels of infestations, the seasonal epidemiology of ticks and the associated management practices. The most common species of tick spread throughout the state was Haemaphysalis bispinosa followed by Rhipicephalus haemaphysaloides, Hyalomma marginatum isaaci and Hyalomma anatolicum anatolicum with mixed infestations being the rule. Although the infestations were found throughout the year, they were greater during the rainy season and rainfall seemed to be the most important climatic factor affecting seasonal variation. In general, most of the small-ruminant populations carried moderate tick burdens with mixed infestations and this varied with the management practices.

The objectives of the present study were to report the influence of factors like age, sex, breed, dung consistency and rearing system on prevalence of Cryptosporidium spp. in south Indian cattle. Two-step nested PCR was employed for detection of Cryptosporidium infection in dairy calves of south Indian states viz., Andhra Pradesh, Karnataka, Kerala, Tamil Nadu and union territory i.e., Puducherry. A total of 459 dung samples from the calves were subjected to nested PCR, 182 were found positive with prevalence percent of 39.65. Age wise comparison showed a high prevalence of Cryptosporidium in the age group of one month old calves. This concludes that the cryptosporidiosis is highly age dependent with young calves showed the highest prevalence. Depending on the group had consistency of dung, the highest prevalence of Cryptosporidium was observed in semi-solid dung, followed by formed and the diarrhoeic group animals. Female calves showed slightly higher prevalence rate than male animals. Cow calves had an overall prevalence percent of 40.75 and the infection rate in buffalo calves was 36.28 %. In relation to rearing system, individual animals had 42.18 % and farm animals showed 38.46 % of Cryptosporidium infection. In conclusion, the prevalence of Cryptosporidium in dairy calves should be correlated with the factors like age, sex, breed, dung consistency and rearing system of the animal to arrive at a reliable epidemiological data on bovine cryptosporidiosis.

Selected aspects of the ovine immune system were examined during the course of repeated infestations with the ixodid ticks, Haemaphysalis bispinosa and Hyalomma anatolicum anatolicum that naturally infest sheep, either individually or together. By the use of flow cytometry it was shown that total T-lymphocyte numbers were significantly reduced from the sixth through the ninth days of all infestations. Gamma/delta (gammadelta+) and CD8+ T-lymphocytes were significantly depleted during tick feeding in all infested groups. CD4+ T-lymphocyte levels were significantly increased during secondary H. bispinosa and mixed species infestations. Hyalomma anatolicum anatolicum caused a significant increase in circulating B-lymphocytes over several days in both initial and secondary infestations. All infested sheep had increased CD4/CD8 and decreased T/B lymphocyte ratios during exposure to both ticks. Bromodeoxyuridine (BrdU) ELISA was used to measure in vitro proliferation of peripheral blood mononuclear cells stimulated with the T-lymphocyte mitogen Concanavalin A (Con A) after their collection from infested sheep. Significant suppression of in vitro proliferation occurred during first and secondary infestations with H. bispinosa, H. a. anatolicum and with both tick species together, beginning on the sixth day of infestation in all cases. These important tick species of sheep significantly modulate the numbers of immune effector cells and proliferation of T-lymphocytes derived from infested animals.

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To evaluate higher-level affinities of Hepatozoon species within Apicomplexa, we sequenced the 18S rRNA gene from 2 parasites (Hepatozoon americanum and Hepatozoon canis) of dogs and 1 (Hepatozoon catesbianae) of bullfrogs. Sequences from other apicomplexans among the Sarcocystiidae, Eimeriidae, Theileriidae, Plasmodiidae, Cryptosporiidae, and Babesiidae, a Perkinsus species and 2 dinoflagellates were obtained from GenBank. Phylogenetic analysis indicated that Plasmodium, Cryptosporidium, and Hepatozoon form a monophyletic group distinct from representatives of other apicomplexan families. Although equivocal, our analysis indicated that Plasmodium and Cryptosporidium are sister taxa and that Hepatozoon is basal to them. To evaluate phylogenetic affinities among H. americanum, H. canis, and other species of Hepatozoon, we examined 18 morphologic and life-cycle features of 13 species currently assigned to Hepatozoon. This analysis indicates paraphyly of Hepatozoon (as currently arranged) because Hepatozoon lygosomarum was found most closely related to Hemolivia mauritanicum. These results, combined with results of previous studies, support elevating Hepatozoon to familial level (Hepatozoidae) as originally suggested by Wenyon in 1926. Both DNA sequence data and morphologic and life-cycle characters support a sister-group relationship between H. americanum and H. canis.

With the changing global scenario there is effect not only on the human survival but also on the prevalence of existing pathogens and appearance of new infectious agents among animal population. This paper emphasises the need for prevalence studies. A retrospective study for 6 years on prevalence of hemoprotozoans in dogs in Chennai showed Babesia gibsoni the predominant parasite of dogs. Details are discussed in this paper.

The occurrence of Kalicephalus sp. of hookworms in a Russell's viper snake maintained in Chennai snake park trust, Chennai is reported. These worms were found in the stomach and intestine. They were cylindrical, thread like and had an elongate body. Anterior end was obliquely truncated with bivalvular buccal capsule. Short, thick and muscularised oesophagus ending in a rounded bulb was observed. In males, a well developed trilobed bursa was observed and the spicules were short and equal. Typical strongyle type eggs were found in the uterus of female worms as well as in the intestinal contents.