Spatial analysis and identification of environmental risk factors affecting the distribution of Indoplanorbis and Lymnaea species in semi-arid and irrigated areas of Haryana, India.

Fasciolosis, amphistomosis and schistosomosis, transmitted by the freshwater snail species Indoplanorbis and Lymnaea, are important snail-borne diseases in India as they affect the entire spectrum of domestic animals causing substantial mortality and economic loss. Identifying any heterogeneity in the spatial distribution of these snail-borne diseases will allow for targeted disease control and efficient use of resources. The objectives of this study were threefold: (i) to describe and explore the spatial distribution of Indoplanorbis and Lymnaea in Rohtak and Jhajjar districts of Haryana, India (ii) to identify factors associated with occurrence of these freshwater snail species and (iii) to produce a map showing the predicted risk of occurrence of Lymnaea and Indoplanorbis spp. in the study area. Snails were collected from water bodies of 99 settlements out of a total of 453 in the study area. Kernel smoothing was used to generate a kernel ratio map while Kulldorff's spatial scan statistic was used to detect clusters of settlements with a high/low risk. Multivariable logistic regression showed that snails were almost ten times more likely to be present in rice-growing areas than in those not growing rice (OR 9.24) and that snails were less likely to be present with each 1 km increase in distance from a canal (OR 0.86). The regression model was used to produce a map illustrating the predicted risk of snail occurrence. Since the distribution of vector snails mirrors the distribution of snail-borne parasitic diseases, such spatial analysis helps to determine the relative risk of snail-infestation as well as snail-borne diseases' distribution and planning of control activities.

Infectivity rate and transmission potential of Hyalomma anatolicum anatolicum ticks for Babesia equi infection.

The infectivity rate of Babesia equi in the salivary glands of Hyalomma anatolicum anatolicum was assessed. The hungry nymphs were fed on a donkey experimentally infected with B. equi. The engorged dropped-off nymphs were collected at different levels of parasitaemia and kept in BOD incubator. After ecdysis, the hungry adults were prefed on rabbits for different time intervals, thereafter the salivary glands were dissected out and acini were examined after methyl green pyronin (MGP) staining. A total of 134 male and 139 female ticks were dissected out. Average infected acini per tick were found to be significantly higher (p<0.05) in male as compared to the female ticks. Further, maximum infected acini in both male and female ticks were found at 24h of prefeeding on rabbits and overall infected acini per tick increased with rise in parasitaemia. The release of infected ticks on susceptible donkeys resulted in development of clinical babesiosis.

Isolates of Theileria annulata collected from different parts of India show phenotypic and genetic diversity.

Phenotypic and genetic polymorphism was studied amongst four Theileria annulata isolates collected from three different parts of India. Amongst various markers studied for the comparison of growth characteristics of schizont cell lines established from these isolates, viability, non-viability counts and nitric oxide (NO) production showed significant variation. A negative correlation was observed between NO production and mRNA expression for TNF-alpha, a potent proinflammatory cytokine related to the pathogenesis of the disease. Phenotypic polymorphism was also revealed by T. annulata schizont-specific monoclonal antibodies (Mabs), viz. 1C7, 1E11, 2G2 and EU-106, which recognized variable number of cells in indirect fluorescent antibody and indirect immunoperoxidase tests, when tested against the four T. annulata isolates collected from India. Genetic polymorphism was recognized amongst the four isolates by restriction digestion analysis of Tams-1 gene PCR products. These observations revealed that the four isolates of T. annulata are different from each other and might be expressing different antigenic determinants on their cell surface.

Immunization of cattle with nymphal Hyalomma anatolicum anatolicum extracts: effects on tick biology.

Antigens derived from partially engorged nymphs of Hyalomma anatolicum anatolicum were used in immunizing crossbred (Bos indicus x Bos taurus) cattle against larval, nymphal and adult H. a. anatolicum and H. dromedarii. The cattle were either infected with Theileria annulata at low parasitaemia or were uninfected. Whole nymphal extract (WNE), nymphal membrane antigens (NMA) and nymphal soluble antigens (NSA) were used for immunization. The group immunized with WNE showed significant and better rejection of H. a. anatolicum ticks as compared to calves immunized with either NMA or NSA. The moulting rates of both engorged larvae and nymphs remained unaffected. Nymphs which engorged on the immunized calves were fully susceptible to infection by T. annulata as indicated by the intensity and abundance of Theileria infections in the resulting adult ticks from immunized and unimmunized Theileria infected cattle. These ticks also transmitted fatal theileriosis to susceptible calves.

Seasonal distribution of Theileria in Hyalomma anatolicum anatolicum ticks of an endemic area of Haryana, India.

The effect of season on the capacity of Hyalomma anatolicum anatolicum ticks to transmit Theileria was studied by detecting Theileria sporoblasts in the salivary glands of 647 adult ticks moulted in winter (November 1990 to March 1991) and 677 adult ticks moulted in the summer-rainy season (June to August 1991). The intensity (number of infected acini per infected tick) and abundance (number of infected acini per tick examined) of Theileria sporoblasts were significantly (P < 0.05) higher in winter moulted ticks (10.75 and 2.23 respectively) than the summer-rainy season moulted ticks (7.31 and 1.77 respectively). The prevalence of infected moulted ticks was not significantly higher in the summer-rainy season (24.22%) than in the winter (20.71%). A higher percentage of winter moulted ticks had high numbers of infected acini (> or = 11/infected tick) than the summer-rainy season moulted ticks, while the trend was reversed for low numbers of infected acini(5/infected tick), being 47.76% for winter and 73.78% for the summer-rainy season. It was concluded that the winter of Haryana is more favourable to the developing theilerial stages in the ticks than the summer-rainy season.

Folacin and cyanocobalamin in relation to natural Trypanosoma evansi infection in buffaloes.

The haematological values of haemoglobin (Hb), packed cell volume (PCV) and vitamin levels of folacin (folic acid), cyanocobalamin (vitamin B12) of buffaloes, in a surra endemic area of Eastern Haryana, India, were determined. Surra-positive buffaloes had significantly low levels of Hb, PCV, folic acid and vitamin B12. These low levels of folic acid and vitamin B12 may have enhanced the clinical signs of chronic trypanosomiasis, caused by Trypanosoma evansi.

Relative role of male and female Hyalomma anatolicum anatolicum ticks in Theileria transmission.

The relative role of male and female Hyalomma anatolicum anatolicum ticks in the epidemiology of Theileria transmission was studied by detecting Theileria sporozoites in the dissected salivary glands of 568 ticks by the methyl green pyronin staining method. Detailed frequency distribution of Theileria-positive acini in the salivary glands of the 264 (46.48%) positive ticks from a field collection in Haryana indicated that the number of infected salivary acini per positive tick was greater in females than in males. This suggests that female ticks have a more important role in Theileria transmission than male ticks. This finding assumes greater significance in the light of the observation that the natural male:female ratio is also in favour of female ticks.

Theileria infectivity of Hyalomma ticks in Haryana, India.

Theileria infection of Hyalomma ticks collected from three districts of Haryana was assessed in whole salivary glands by the methyl-green pyronin staining method. Of 1,662 ticks screened, 546 (32.8%) were found Theileria positive. Infection rate in 935 female ticks (36.9%) was more than that of 727 male ticks (27.6%). Density of Theileria infection (number of infected acini per infected tick) was also higher in female ticks. Theileria infection rate of ticks varied greatly in the three districts viz. only 12.0% in Rohtak, 25.8% in Hisar and 48.3% in Karnal. Per cent infection rate was high (63.7%) in ticks from indigenous cattle and low (18.6%) in those collected from buffaloes. However, the intensity of infection in infected ticks from cross-bred cattle was comparatively much higher. Frequency distribution of Theileria positive acini in infected ticks revealed a low density of infection per infected tick. This points to the largely stable endemic situation prevailing in Haryana. Only a single salivary acinus was found infected in 16.6% of the infected ticks, about 70% had up to 10 infected acini while only about 10% had over 25 infected acini per tick. The masses in acini presumed to be Theileria were confirmed by demonstrating parasitic masses on staining one of a pair of salivary glands and inoculating the suspension of the other half of the gland into two cross-bred cow calves which developed clinical signs and lesions typical of theileriosis.