Sarcocystis and sarcocystosis in India: status and emerging perspectives.

Sarcocystis spp. are a group of tissue cyst-forming coccidia which infect a vast range of animals as well as human beings. Found frequently in animal carcasses at slaughter, undermining their value, they have also been found associated with clinical disease. Dogs and cats are involved in the transmission. Studies in India point to a vast reservoir of infection with high prevalence rates in various livestock species. However, there is a glaring paucity of reports on the horse and Sarcocystis of the camel has remained totally unexplored so far. At least two different Sarcocystis spp. can parasitize each livestock host species. Experimental transmission studies have provided additional parameters for distinguishing the species. The clinical symptoms are generally non-specific and diagnosis in the living animal, by the presently available means, is almost impossible. Immunodiagnosis till now is beset with problem of cross-reactivity. Treatment with anti-coccidials presently tried do not seem satisfactory. Of the two zoonotic species with cattle-man and pig-man cycles, only the latter seems of some significance in India due to backyard pig-rearing and slaughter practices. It is a paradox that despite high prevalence of S. suihominis in pigs, reports of human cases are limited. This and some of the existing grey areas of information in the Indian context, have been highlighted as also possible directions for future research.

Polyclonal antibody-based antigen-detection immunoassay for diagnosis of Trypanosoma evansi in buffaloes and horses.

An enzyme-linked immunosorbent assay (ELISA) was employed for the detection of Trypanosoma evansi antigens in serum samples of field cases of buffaloes and horses in northern India. In 323 naturally infected/suspected buffaloes, circulating antigenaemia was detected in 180 (55.72%), whereas parasitaemia by wet blood smear examination was found in 62 (19.19%) only. The antigen-ELISA was positive in 47 of the 62 parasitologically proven cases and in 86 of the 116 cases with anti-trypanosome antibodies detected by ELISA. Of the 80 horses examined antigen-ELISA was positive in 45 (56.75%) sera. The antigen-detection assay was positive in 14 of the 19 parasitaemic cases whereas the antibody-detection assay was positive in 18 of the 30 parasitaemic cases. In the present study, antigen-ELISA was found to be more sensitive and specific compared with antibody-ELISA and wet blood examination, and could prove a useful tool for epidemiological studies of latent trypanosomosis in livestock.

Polypeptide profiles and antigenic characterization of cell membrane and flagellar preparations of different stocks of Trypanosoma evansi.

Polypeptides and antigens of cell membrane (CM) and flagellar (Fl) preparations of seven different stocks of Trypanosoma evansi were studied using sodium dodecyl sulphate polyacrylamide gel electrophoresis and by Western blotting. The stocks were collected from Bareilly, Bikaner, Hisar Karnal, Lucknow and Ludhiana localities of northern India and were isolated from either buffalo, equids or camel. Between two and five polypeptides with molecular weights (MW) ranging from 48.4 to 80.2 kDa (except one stock) were detected in the CM preparations and between four and 12 polypeptides ranging from 17.6 to 80.2 kDa were observed in the Fl preparations. The 78.3 kDa polypeptide was common to the CM preparation of all seven stocks. The number of antigens found in the CM of different stocks using homologous and heterologous hyperimmune sera (HIS) varied between three and 11 and were in the MW range of 25-98 kDa. Likewise the number of Fl antigens of different stocks varied between three and 14, predominantly in the MW range 17-98 kDa. Antigenic cross-reactivity among polypeptides of the CM and Fl preparations detected by various HIS was also high, indicating the possibility of less antigenic variability among these seven stocks.

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.

Toxoplasma seroprevalence in animals in northern India.

In a serological survey of latent Toxoplasma prevalence on 3761 animals in northern India by the microtitre indirect haemagglutination test, 23.7 per cent were found to have antibody titres ranging from 1:4 to 1:1024. Seropositivity was recorded in 25.3 per cent of 1227 sheep, 30.3 per cent of 961 goats, 11.8 per cent of 603 horses, 19.3 per cent of 243 cattle, 15.7 per cent of 108 water buffaloes, 31.5 per cent of 178 pigs, 30.9 per cent of 175 dogs, 33.7 per cent of 80 cats and in 9.7 per cent of 186 bandicoot rats. Relevant epidemiological data has been furnished. High seropositivity in food animals and frequent isolations of Toxoplasma highlight the likely public health implications of the findings.

Toxoplasma prevalence and human occupational groups.

Toxoplasma antibody prevalence was studied in four specialized groups of human population at Hissar, Haryana to study the influence, if any, of the degree of animal contact. While seropositivity among 64 persons of general population was 28.1 per cent, that in livestock and pet owners was found to be higher (35.0 per cent). Among other groups the overall positivity was similar to that in the general population, but there was greater concentration of higher serotitres among the laboratory animal handlers and postmortem attendants. It appears that the intimacy of animal contact is more important than the duration.

Evidence of cell mediated immune response in infection with Eimeria bareillyi in buffaloes.

Delayed dermal hypersensitivity and leucocyte migrations were measured in buffalo calves experimentally inoculated with Eimeria bareillyi. Dermal hypersensitivity, characterized by increased thickness and local inflammation, was observed in calves inoculated intradermally with E. bareillyi antigen on Days 21 and 28 after infection. The highest inhibition of leucocyte migration was observed in infected buffalo calves on Days 21 and 28 post-infection.

Chemotherapeutic efficacy of sulphadimidine, amprolium, halofuginone and chloroquine phosphate in experimental Eimeria bareillyi coccidiosis of buffaloes.

Sulphadimidine, amprolium, halofuginone and chloroquine phosphate were administered to buffalo calves 10 days after experimental infection with Eimeria bareillyi. Animals given sulphadimidine or amprolium remained clinically normal and shed only a few oocysts in their faeces. Halofuginone was found partially effective and chloroquine phosphate completely ineffective in preventing faecal oocyst discharge and intestinal lesions. Sulphadimidine and amprolium treated calves gained weight, but chloroquine treated calves suffered progressive weight loss similar to that of infected untreated controls. No significant alterations of haematological values were observed either in the treated calves or in the untreated controls.

Experimental toxoplasmosis in buffalo calves.

Eight buffalo calves were inoculated with infectious oocysts of a virulent strain of Toxoplasma gondii, five with 1 x 10(5), and the other three with 5 x 10(5) oocytes each while two more were kept as non-inoculated controls. Infected animals developed pyrexia, anorexia, conjunctivitis and dyspnoea. The clinical symptoms, haematological changes and serological response were of a low order. The appearance of haemagglutinating antibodies at significant levels (greater than or equal to 1:64) was first observed at 21 days after inoculation (DAI), peaked at 42 DAI and rapidly declined after 63 DAI. The inoculated calves were killed (or died) at intervals from 11 DAI to 110 DAI. The organism could be recovered from several tissues of a calf that died 11 DAI, but was rapidly removed subsequently. Only the lymph nodes were infective till 32 DAI. Parasitism of the retina was demonstrated in one calf. The significance of these findings is discussed.

Toxoplasma infection and abortion in dairy goats.

Serological investigation by the indirect haemagglutination test for Toxoplasma antibodies was carried out in a flock of dairy goats. Antibody titres ranging from 1:4 to 1:1,024 were found in 34% of 371 apparently healthy animals. High antibody titres of 1:256 suggestive of recent infection were noted in 18(4.9%) animals including 13 nannies. The occurrence of a number of non-brucella abortions associated with high serological titres and the isolation of the parasite from the brain tissues of an aborted foetus suggested Toxoplasma as a probable aetiologic factor. Sera having significantly levels of haemagglutinating antibodies (greater than or equal to 1:128) were also found positive to the card agglutination test. Epidemiological aspects and the public health potential of subclinical toxoplasmosis in dairy goats are discussed.

Antibodies to Toxoplasma gondii in equids in north India.

The prevalence of antibodies to Toxoplasma gondii was investigated among equids in 3 localities of north India, using the direct haemagglutination test. Of the 603 animals sampled, titres ranging from 1:8 to 1:512 were found in 71 (11.8 per cent). Specific titres of 1:64 or more were found in 34 (5.6 per cent) sera. The number of positive titres at Babugarh (Uttar Pradesh) was considerably higher than at 2 other localities. Although the likelihood of positive sera appeared to increased with age, the animal's sex appeared to have little influence. Subjects with reproductive disorders or eye ailments did not have a high prevalence of positive titres compared with normal subjects.

Prevalence of toxoplasma antibodies in dogs in Chandigarh territory, North India.

Sera from 119 dogs examined by the indirect haemagglutination test for Toxoplasma antibodies showed an overall prevalence rate of 29.4 per cent; 10.9 per cent with antibody titre of 1:128 or more. The per cent of positive cases in a dog clinic was not significantly higher than in apparently healthy subjects. Higher titre levels were more frequent in the sera of older animals and in those having concomitant disease.

Effects of 60Co irradiation on virulent Toxoplasma gondii and its use in experimental immunization.

The effects of 60Co irradiation on the virulence and immunogenicity of the RH strain of Toxoplasma gondii was studied by infecting batches of mice with graded inocula of tachyzoites that had been exposed to radiation doses ranging from 0 to 20 000 rad. While doses of 15 000 and 20 000 rads appeared to be effective, and 10 000 rad nearly effective in annulling the virulence, irradiation at 5000 rad was only partially effective in rendering the organisms avirulent and could achieve only a prolongation of survival time of the inoculated mice. The survivors of higher irradiation inocula showed no evidence of the development of the parasite in them, but could resist a limited virulent challenge. The use of a booster inoculation improved both the quality and the duration of protective effect.

Occurrence of Toxoplasma gondii in slaughter pigs in India.

A serological and cultural investigation on the occurrence of T. gondii amongst slaughter pigs in north India has been carried out. Toxoplasma antibodies were found in the sera of 31.5% of the 178 pigs examined by the indirect haemagglutination test. Seropositivity at titres of 1:128 or more was shown by 11.8% of the animals. Isolation by mouse passage was successful in one out of the 26 tissue samples from 17 pigs. This is the first isolation of T. gondii from pigs in this country.