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A A Gajadhar

Publications and source records attributed to A A Gajadhar.

At least 19 recordsLinked to original sources
PubMed2006

Overview of food- and water-borne zoonotic parasites at the farm level.

Zoonotic parasites found in food animals include a wide variety of protozoa, nematodes, trematodes, and cestodes. Many of these parasites are emerging or already occur globally due to changes in farming practices and the increased movement of animals, food, and people. Some of the emerging or ubiquitous parasites, including Toxoplasma, Cryptosporidium, Trichinella, and Taenia, present enormous risks to global food production and consumer health. The parasite life cycle stages, such as eggs, oocysts, and cysts, typically resist adverse temperatures, desiccation, natural irradiation, chemicals, and disinfectants that are commonly used for controlling bacteria and viruses. Other important parasites include trematodes such as Clonorchis and Paragonimus, which are transmitted via fish or crustaceans and cause serious human disease in specific regions of the world. The potential for global occurrence of these parasites is increasing. Control of zoonotic parasites at the producer level requires education and the development and implementation of effective measures to eliminate the contamination of agricultural water and feed with viable stages of parasites. Standardisation, implementation, and documentation of control measures should increase confidence in global food trade.

Animals↗
PubMed2004

International Commission on Trichinellosis: recommendations on the use of serological tests for the detection of Trichinella infection in animals and man.

The use of serological tests to detect Trichinella infection in domestic and wild animals and in humans has not been standardised yet. This review provides an uniform set of recommendations for the development and use of serological tests to detect circulating antibodies in serum samples. The recommendations are based on the best scientific published information and on the unpublished data from laboratories with a great expertise in this field and represent the official position of the International Commission on Trichinellosis regarding acceptable methods and the evaluation of the sensitivity and specificity. These recommendations are subject to change as new scientific information becomes available.

Animals↗
PubMed2004

Experimental Toxoplasma gondii infection in grey seals (Halichoerus grypus).

Laboratory-reared animals were used to assess the susceptibility of seals (Halichoerus grypus) to Toxoplasma gondii infection. Four seals were each orally inoculated with 100 or 10,000 oocysts of T. gondii (VEG strain), and another 4 seals served as negative controls. Occasionally, mild behavioral changes were observed in all inoculated seals but not in control animals. A modified agglutination test revealed the presence of antibodies to T. gondii in sera collected from inoculated seals and mice inoculated as controls. No evidence of the parasite was found on an extensive histological examination of seal tissues, and immunohistochemical staining of tissue sections from inoculated seals revealed a single tissue cyst in only 1 seal. Control mice inoculated with 10 oocysts from the same inoculum given to seals became serologically and histologically positive for T. gondii. Cats that were fed brain or muscle tissue collected from inoculated seals passed T. gondii oocysts in feces. This study demonstrates that T. gondii oocysts can establish viable infection in seals and supports the hypothesis that toxoplasmosis in marine mammals can be acquired from oocysts in surface water runoff and sewer discharge.

Animals↗
PubMed2001

Ultrastructural characteristics of nurse cell-larva complex of four species of Trichinella in several hosts.

The nurse cell-larva complex of nematodes of the genus Trichinella plays an important role in the survival of the larva in decaying muscles, frequently favouring the transmission of the parasite in extreme environmental conditions. The ultrastructure of the nurse cell-larva complex in muscles from different hosts infected with T. nativa (a walrus and a polar bear), T. spiralis (horses and humans), T. pseudospiralis (a laboratory mouse) and T. papuae (a laboratory mouse) were examined. Analysis with transmission electron microscope showed that the typical nurse cell structure was present in all examined samples, irrespective of the species of larva, of the presence of a collagen capsule, of the age of infection and of the host species, suggesting that there exists a molecular mechanism that in the first stage of larva invasion is similar for encapsulated and non-encapsulated species.

Animals↗
PubMed2000

Historical perspectives and current global challenges of Trichinella and trichinellosis.

Trichinella spiralis and related species of Trichinella have had a long history of causing human disease, and as a foodborne pathogen have had a major impact on international commerce of pork and other meat animal species which are known to transmit the parasite. Our knowledge of Trichinella has increased substantially over the past few years particularly in the areas of phylogeny, host diversity, epidemiology and control. In this paper, we provide a brief overview of our understanding of Trichinella from its discovery to present time. Past and current challenges of the control of Trichinella and trichinellosis are summarized. As editors of this special issue of Veterinary Parasitology, we introduce a series of invited review articles prepared by experts from around the world, summarizing recent knowledge in Trichinella and trichinellosis.

Animals↗
PubMed2000

International Commission on Trichinellosis: recommendations on methods for the control of Trichinella in domestic and wild animals intended for human consumption.

This document provides a uniform set of recommendations for the control of Trichinella at all levels (on the farm, at slaughter and in processed meats). These recommendations are based on the best scientific information available and represent the official position of the International Commission on Trichinellosis regarding acceptable control methods. These recommendations are subject to change as new scientific information becomes available.

Abattoirs↗
PubMed2000

Comparison of growth rates of Tritrichomonas foetus isolates from various geographic regions using three different culture media.

The growth rates of 16 isolates of Tritrichomonas foetus from three distinct geographic regions were investigated in modified Diamond's medium, liver infusion broth medium and a commercially available culture kit. While some differences in growth characteristics were detected for different isolates and in the three different media, all isolates grew. Trichomonads reached peak concentrations from an initial concentration of 10(4) trichomonads/ml on Days 2, 3 and 4 in modified Diamond's medium, on Days 2-6 (excluding CAPTF102) in the commercial culture kit and on Days 2-7 in liver infusion broth medium. Viable parasites were detectable for longer periods in liver infusion broth medium and the commercial culture kit than in Diamond's medium. Peak concentrations for isolates tended to be higher in modified Diamond's medium than in liver infusion broth medium or the commercial culture kit. Results show that these three media are suitable for the growth of all 16 T. foetus isolates from three continents and suggest that these media could be used effectively throughout the world.

Animals↗
PubMed2000

Prevalence of antibodies to Toxoplasma gondii in ostriches (Struthio camelus).

Serum samples from 973 ostriches (Struthio camelus) in Canada were examined for antibodies to Toxoplasma gondii by the modified agglutination test incorporating mercaptoethanol and formalin-fixed whole tachyzoites. Twenty-eight (2.9%) of the 973 birds were found to be seropositive for antibodies to T. gondii at titers of 1:25 in 15 birds, 1:50 in 12 birds, and 1:500 in 1 bird. This is the first record of T. gondii exposure in ostriches, and it supports the hypothesis that all avian species are susceptible to Toxoplasma infection. Nevertheless, the results of this study suggest that the risk of acquiring toxoplasmosis from ostriches as a food source is low.

Agglutination Tests↗
PubMed1999

Effects of temperature on the survival of Tritrichomonas foetus in transport, Diamond's and InPouch TF media.

The abilities of two isolates of Tritrichomonas foetus to survive and replicate in transport and Diamond's medium or in the InPouch TF system (Bio-Med Diagnostics) when exposed to different temperatures for different periods were determined in a series of experiments. Tubes containing thioglycollate transport medium or pouches were inoculated with 4000 to 5000 organisms and kept for up to seven days at 37 degrees C, 22 degrees C, 4 degrees C, or -20 degrees C. When the holding time had elapsed, the numbers of motile T foetus were counted. Samples in transport medium were transferred to Diamond's medium, and both the pouches and tubes containing Diamond's medium were incubated at 37 degrees C. The cultures were examined and counted four or five times during the 10 to 14 day culture period. The sensitivity of the test under the different conditions, expressed as the number of positive cultures/the total number of samples x 100, varied from zero to 100 per cent depending upon the combination of variables considered. In each medium, with both isolates of T foetus, all samples kept for up to four days at 22 degrees C or 37 degrees C were positive. All cultures of samples kept more than five days at 4 degrees C were negative. No positive cultures were detected when samples were kept more than three hours at -20 degrees C. The day on which the cultures reached mean peak concentration varied with the temperature at which the samples had been kept before they were cultured.

Animals↗
PubMed1999

A validated Trichinella digestion assay and an associated sampling and quality assurance system for use in testing pork and horse meat.

A revised digestion method, developed for efficiency and quality assurance, was validated for the detection of Trichinella larvae in pork and horse meat to meet requirements for food safety testing and facilitate access to international markets. The method consisted of a tissue homogenization step and a spin bar digestion procedure conducted at 45 degrees C to free larvae from muscle tissue, followed by two sequential separatory funnel steps to concentrate the larvae for detection using a stereomicroscope. Critical control points were determined for the method and monitored during testing. Under conditions of a defined protocol, test capacity was suitable for industrial applications, since multiples of up to 100 g of tissue could be analyzed at one time. The overall sensitivity of the test system depended on the size and origin of the sample taken from individual infected carcasses. Data from swine indicated that the currently accepted sample size of 1 g from individual carcasses consistently detected larval loads of > or =3 larvae per gram. Larval loads of 1.0 to 1.9 larvae per gram required 3- to 5-g samples of muscle tissue for reliable detection. Five-gram samples were considered optimal, because they consistently detected more tissues than 3-g samples, although the difference was not statistically significant. Tissue localization studies in experimental pigs indicated that the tongue and diaphragm were the tissues of choice for the most sensitive larval recovery. A system of analyst training, laboratory certification based on ISO guide 25, and on-site proficiency panel testing was used to ensure that external laboratories would consistently produce reliable test results. The system developed for pork was successfully modified for the testing of horse meat.

Animals↗
PubMed1999

Differentiation of Trichinella genotypes by polymerase chain reaction using sequence-specific primers.

A method was developed to identify species and genotypes within the genus Trichinella using polymerase chain reaction (PCR) and specific primers. Enzymatic amplification of 2 partially conserved and repetitive genomic DNA sequences that have been shown to be variable in length within the different Trichinella genotypes form the basis of this test. Within these regions of the genome, 4 sets of primers were evaluated from which 2 were chosen for their ability to differentiate among the genotypes under stringent primer annealing conditions while maintaining high yields of amplification product. Differences in the size of PCR products from multiple isolates of each genotype indicate sufficient variation to identify 7 of the 8 parasite groups within this genus. One primer set can differentiate among some genotypes working from a single larva. Identification of Trichinella genotypes will assist in distinguishing between sylvatic and synanthropic life cycles. Such information will be critical in tracing sources of trichinellosis by easily and unambiguously identifying likely host reservoirs and will provide valuable information for instituting methods of control.

Animals↗
PubMed1998

Proficiency samples for quality assurance in Trichinella digestion tests.

A reliable method to produce proficiency samples containing known numbers of Trichinella spiralis cysts for use in quality assurance systems for Trichinella digestion tests was developed and validated. A filtrate containing Trichinella cysts was produced by homogenizing and filtering the muscles of an experimentally infected rat. Using a stereomicroscope and micropipette, intact cysts were removed from the filtrate and were transferred onto an agar substrate to allow accurate counting and subsequent transfer into a sample matrix. The proficiency sample matrix consisted of 20-g balls of lean ground beef and was combined with 80 g of a Trichinella-free muscle tissue to obtain the required 100-g sample weight for the assay. The mean overall larval recovery from 404 proficiency samples was 93.0%. Larval recoveries > or = 95, 85, and 75% occurred in 52.4, 84.4, and 94.3%, respectively, of the 404 samples tested. Results indicated that, after a short training period, technicians with no prior experience in digestion techniques performed as well as experienced technicians. The maximum shelf life of proficiency samples was not determined but was at least 3 weeks. Validation data were used to develop panels composed of proficiency samples prepared as described above and to establish guidelines for the interpretation of proficiency panel results.

Animals↗
PubMed1998

Trichinella spiralis in sylvatic hosts from Prince Edward Island.

Larvae of Trichinella sp. were found in two of 208 red foxes (Vulpes vulpes) and one of 125 coyotes (Canis latrans) obtained from trappers from Prince Edward Island (Canada) in 1995 and 1996. A polymerase chain reaction based DNA biotyping method revealed the larvae to be isolates of Trichinella spiralis. This is the first verified identification of T. spiralis in sylvatic hosts from Canada.

Animals↗
PubMed1998

Prevalence of Toxoplasma gondii in Canadian market-age pigs.

During 1991 and 1992, 2,800 market-age pigs were sampled at federally inspected abattoirs from across Canada. Anti-Toxoplasma gondii IgG at titers of > or =1:32 were found in 240 pigs examined by a commercial, latex agglutination test. Seroprevalences ranged from 3.5 to 13.2% in the different regions of the country. Tissue hybridization studies using a previously developed probe demonstrated T. gondii ribosomal RNA in 9 of 36 animals, whereas mouse bioassay testing of heart muscle and diaphragm from all 2,800 pigs failed to demonstrate the presence of infective stages of T. gondii in tissues. Although serology results from this study indicated that Canadian market-age pigs are infected with T. gondii at rates similar to those reported from other parts of North America, mouse bioassay results suggested that Canadian pork products contain low levels of infective organisms. This apparent discrepancy suggests that serological evidence of T. gondii infection in pigs alone does not accurately assess the public health risks associated with consuming improperly cooked pork products.

Abattoirs↗
PubMed1998

Tissue migration of Elaphostrongylus spp. in guinea pigs (Cavia porcellus).

Third-stage larvae of Elaphostrongylus cervi, originating from red deer (Cervus elaphus), first reached the central nervous system (CNS) of guinea pigs (Cavia porcellus) 11 days postinfection (DPI). Neurologic signs were seen between 11 and 62 DPI in 4 of a total of 18 infected guinea pigs killed up to 112 DPI. Animals showing signs had 3 or more larvae in the CNS. Only 1, of a total of 1,114 larvae recovered, had developed to the fourth stage at 40 DPI. A direct tissue migration by third-stage larvae to the CNS was revealed by pressing and digesting almost all body tissues and by histological examination. Larvae penetrated through the stomach wall into the peritoneal cavity and then through the diaphragm into the pleural cavity. Many became encapsulated by inflammatory cells in the omentum, abdominal mesentery, mediastinum, and just beneath the liver capsule and lung pleura. A total of 44 larvae succeeded in reaching the CNS, apparently by migrating from the body cavities into muscles of the lateral body wall and entering the vertebral canal, likely along spinal nerves. Data were not consistent with a hematogenous migratory route that has been proposed previously. Few third-stage larvae of E. alces, originating from moose (Alces alces), were able to penetrate the gut of guinea pigs and none reached the CNS.

Animals↗
PubMed1997

beta-(1-->3, 1-->4) oat glucan enhances resistance to Eimeria vermiformis infection in immunosuppressed mice.

The effect of intragastrically or parenterally administered beta-glucan, extracted from oats, on the enhancement of disease resistance to Eimeria vermiformis was studied in C57BL/6 mice. Groups of mice were immunosuppressed with dexamethasone (DXM), infected with oocysts of E. vermiformis and treated with oat beta-glucan by the intragastric (i.g.) or subcutaneous (s.c.) routes. Faecal oocyst shedding was reduced in the beta-glucan-treated groups compared to the non-treated group. Immunosuppressed mice which received no beta-glucan treatment showed more severe clinical signs of the disease and a 50% mortality, while minimal clinical signs and no mortality were recorded in the beta-glucan-treated groups. Total IgG, IgG1, IgG2a, IgM and IgA immunoglobulins in the serum of beta-glucan-treated groups were overall higher than those in the non-treated group. Specific IgG anti-sporozoite and merozoite immunoglobulins in serum were significantly higher in the beta-glucan-treated groups than in the non-treated animals. No significant differences were found in the levels of intestinal IgA anti-sporozoite and anti-merozoite immunoglobulins. IFN-gamma- and IL-4-secreting cells, in response to sporozoite antigen, were detected in the spleen and mesenteric lymph nodes of the beta-glucan-treated groups only. In conclusion, the i.g. and s.c. oat beta-glucan treatment increased the resistance to E. vermiformis infection in immunosuppressed mice.

Adjuvants, Immunologic↗
PubMed1997

Experimental induction of equine protozoal myeloencephalitis in horses using Sarcocystis sp. sporocysts from the opossum (Didelphis virginiana).

Sarcocystis sp. sporocysts isolated from eight feral opossums (Didelphis virginiana) were pooled and fed to 18 commercially reared budgerigars (Melopsittacus undulatus), 14 wild-caught sparrows (Passer domesticus), one wild-caught slate-colored Junco (Junco hyemalis) and five weanling horses (Equus caballus). All budgerigars died within 5 weeks post inoculation (wpi). Histologic examination revealed meronts within the pulmonary epithelia and typical Sarcocystis falcatula sarcocysts developing in the leg muscles. Sparrows were euthanized 13 and 17 wpi and their carcasses were fed to four laboratory raised opossums. Sporocysts were detected in the feces of two opossums on 15 days post inoculation (dpi) and in a third opossum on 40 dpi. Fecal samples from the fourth opossum remained negative; however, sporocysts were found in intestinal digests from all four opossums. Sporocysts were not found in feces or intestinal digest of an additional opossum that was fed three uninoculated sparrows. Five foals were fed sporocysts (Foals 2, 3, 4, 5, and 7) and two foals were maintained as uninoculated controls (Foals 1 and 6). Sporocysts from two additional feral opossums also were fed to foals. Foal 5 was given 0.05 mg kg-1 dexamethasone sodium phosphate daily beginning 2 days before inoculation for a total of 2 weeks. Horse sera were tested three times per week, and cerebrospinal fluid (CSF) samples were tested biweekly for anti-Sarcocystis neurona antibodies by Western blot analysis. No foals had any S. neurona-specific antibodies by Western blot analysis prior to sporocysts ingestion. Seroconversion occurred in Foals 3, 5, and 7 by 24 dpi, followed by positive CSF tests on 28 dpi. Foals 2 and 4 seroconverted by 40 dpi. Cerebrospinal fluid from Foal 2 tested positive by 42 dpi, but Foal 4 remained seronegative throughout the study. Sera and CSF from control Foals 1 and 6 remained seronegative. All foals with positive CSF developed neurologic clinical signs. Neurologic disease was evident in Foals 2 and 3 by 42 dpi and in Foal 7 by 28 dpi. The severity of clinical signs progressed to marked spasticity, hypermetria and ataxia in Foal 7 by the end of the trial. Necropsy examination of inoculated foals did not reveal gross lesions; however, microscopic lesions consistent with equine protozoal myeloencephalitis (EPM) were found in Foals 2, 3, and 7. Protozoa were not observed in the tissue sections. Microscopic lesions consistent with EPM were not found in Foals 4 and 5 or in uninoculated control Foals 1 and 6. Foal 5 had unilateral non-inflammatory lesions in the cervical and thoracic spinal cord consistent with cord compression. These data indicate that the opossum is a definitive host of S. neurona.

Animals↗