Browsing Virginia-Maryland College of Veterinary Medicine (VMCVM) by Issue Date
Now showing 1 - 20 of 1108
Results Per Page
- Virginia Maryland: Virginia-Maryland Regional College of Veterinary Medicine newsletter(Virginia Maryland: Virginia-Maryland Regional College of Veterinary Medicine, 1997)
- Examination of extraintestinal tissue cysts of Isospora belliLindsay, David S.; Dubey, Jitender P.; Toivio-Kinnucan, M. A.; Michiels, J. F.; Blagburn, B. L. (American Society of Parasitology, 1997-08)Relapse is common in immunocompetent and immunosuppressed humans infected with Isospora belli and is believed to be associated with the presence of extraintestinal stages. In the present study, we examined this important stage in an AIDS patient using histological, immunohistological, histochemical, and ultrastructural methods to better understand the development and structure of this stage and to develop better means of detecting infections. Antisera made in rabbits to Isospora suis, Toxoplasma gondii, Hammondia hammondi, Sarcocystis neurona, Neospora caninum, and Caryospora bigenetica were tested against I. belli tissue cysts in the avidin-biotin peroxidase complex (ABC) immunohistological test. Most antisera reacted positively in the ABC test at dilutions of 1:100 but not at dilutions of 1:250. Some antisera to N. caninum and H. hammondi reacted positively at dilutions of 1:1,000 in the ABC test. Most reactive antisera stained the tissue cyst wall and not the enclosed zoite. Eight histochemical tests were examined and most were nonreactive with I. belli zoites or tissue cysts. Transmission electron microscopy revealed that the tissue cyst wall was composed of granular material and was directly beneath the parasitophorous vacuole membrane. Zoites were in the center of the tissue cysts and were surrounded by fibrillar material that appeared to originate from the zoite surface. Tubulelike structures were present in the granular tissue cyst wall and in the fibrillar material that surrounded the zoite. Zoites contained a crystalloid body. New findings in the present study consisted of identifying what are probably early tissue cysts that lack a developed tissue cyst wall, demonstrating that more than 1 tissue cyst can occupy a host cell, describing the distribution of micronemes and the shedding of zoite membranes, and identifying tubular structures in the inner tissue cyst wall and inner compartment.
- Virginia Maryland: Virginia-Maryland Regional College of Veterinary Medicine newsletter(Virginia Maryland: Virginia-Maryland Regional College of Veterinary Medicine, 1998)
- Vaccination of mice with Neospora caninum: Response to oral challenge with Toxoplasma gondii oocystsLindsay, David S.; Lenz, S. D.; Dykstra, C. C.; Blagburn, B. L.; Dubey, Jitender P. (American Society of Parasitology, 1998-04)Neospora caninum is a protozoan parasite that can cause severe disease in mammals. Two experiments were conducted to examine the effects of subcutaneous (s.c.) vaccination with Hank's balanced salt solution (HBSS), 1 x 10(5) N. caninum NC-1 strain tachyzoites or 1 x 10(5) Toxoplasma gondii TS-4 strain tachyzoites on challenge oral infections in mice with sporulated VEG strain T. gondii oocysts (1 x 10(3) oocysts exp. 1 and 5 x 10(3) oocysts exp. 2). An additional study, experiment 3, evaluated s.c. challenge with 2.5 x 10(3) tachyzoites of the highly virulent RH strain of T. gondii after vaccination with HBSS, NC-1 tachyzoites, or TS-4 tachyzoites. Mice vaccinated with NC-1 strain tachyzoites survived significantly (P < 0.05) longer than mice given HBSS in experiment 1, but not in experiments 2 and 3. Mice vaccinated with TS-4 strain tachyzoites survived significantly longer than HBSS-vaccinated mice in experiments 1, 2, and 3 and significantly longer than mice vaccinated with the NC-1 strain in experiments 2 and 3. Toxoplasma gondii tissue cyst numbers were significantly lower for mice vaccinated with TS-4 strain tachyzoites than mice vaccinated with HBSS or the NC-1 strain tachyzoites in experiment 1. No difference was observed in tissue cyst numbers in mice vaccinated with HBSS or NC-1 strain tachyzoites in experiment 1. No HBSS-vaccinated mice survived experiment 2, and the numbers of T. gondii tissue cysts were significantly lower for mice vaccinated with the TS-4 strain tachyzoites compared to NC-1 strain tachyzoites. No HBSS- or NC-1-vaccinated mice survived RH strain challenge in experiment 3. Results of these experiments indicate that infection with N. caninum provides some protection against fatal oral infection with T. gondii oocysts of a moderately pathogenic strain but not tachyzoites of a highly pathogenic strain. The protection provided bq N. caninum is much less than that provided by previous exposure to T. gondii, and the numbers of tissue cysts in the brains of mice are not significantly (P > 00.5) lowered.
- Complete development of the porcine coccidium Isospora suis Biester, 1934 in cell culturesLindsay, David S.; Quick, D. P.; Steger, A. M.; Toivio-Kinnucan, M. A.; Blagburn, B. L. (American Society of Parasitology, 1998-06)Development from inoculated sporozoites to unsporulated oocysts of Isospora suis Biester, 1934 is described in a swine testicular (ST) cell line. Sporozoites penetrated ST cells within 1 hr postinoculation (PI). Development was initially by endodyogeny to produce binucleate type I meronts and type I merozoites. Division by endodyogeny continued during the 13-day observation period and type I merozoites were the developmental stages most abundant at observation periods >3 days PI. Mutinucleate type II meronts and type II merozoites were first observed 7 days PI. Gamonts and oocysts were present 12 days PI. Oocysts did not sporulate in vitro. The ultrastructural features of stages were similar to those that occur in the pig host.
- Virginia Maryland: Virginia-Maryland Regional College of Veterinary Medicine newsletter(Virginia Maryland: Virginia-Maryland Regional College of Veterinary Medicine, 1999)
- Heifer inventory and the economics of replacement rearingBailey, Thomas L.; Currin, John F. (Virginia Cooperative Extension, 1999)
- Milk production evaluation in first lactation heifersBailey, Thomas L.; Currin, John F. (Virginia Cooperative Extension, 1999)
- Campylobacter jejuni - An emerging foodborne pathogenAltekruse, Sean Fitzgerald; Stern, N. J.; Fields, P. I.; Swerdlow, David L. (1999-01)Campylobacter jejuni is the most commonly reported bacterial cause of foodborne infection in the United States. Adding to the human and economic costs are chronic sequelae associated with C. jejuni infection-Guillain-Barre syndrome and reactive arthritis. In addition, an increasing proportion of human infections caused by C. jejuni are resistant to antimicrobial therapy. Mishandling of raw poultry and consumption of undercooked poultry are the major risk factors for human campylobacteriosis. Efforts to prevent human illness are needed throughout each link in the food chain.
- Characterization of temperature-sensitive strains of Neospora caninum in miceLindsay, David S.; Lenz, S. D.; Blagburn, B. L.; Brake, D. A. (American Society of Parasitology, 1999-02)Temperature-sensitive (ts) strains of the Neospora caninum tachyzoites were selected by chemical mutagenesis and selection for growth at 32 C. Three ts strains and the parental, N. caninum wild-type strain, NC-1, were examined in the present study for their ability to cause disease in inbred BALB/c mice, outbred ICR mice, and chemically immunosuppressed ICR mice. In BALB/c mice, all 3 strains failed to induce clinical disease, whereas infection with the NC-1 strain caused central nervous system disease and death in some mice. No disease was observed in ICR mice inoculated with the 3 ts strains or the NC-I strain. All immunosuppressed ICR mice inoculated with the NC-1 strain died, whereas no immunosuppressed mice inoculated with the NCts-4 strain and only 1 of 5 mice inoculated with the NCts-8 and NCts-12 strains died. The NCts-4 and NCts-12 strains reverted to a wild-type phenotype when grown at 37 C. Vaccination of BALB/c mice with live, but not frozen NCts-8 strain tachyzoites induced significant (P < 0.05) protection following NC-1 strain challenge.
- Development of Sarcocystis falcatula in cell cultures demonstrates that it is different from Sarcocystis neuronaLindsay, David S.; Dubey, Jitender P.; Horton, K. M.; Bowman, D. D. (Cambridge University Press, 1999-03)The development of Sarcocystis falcatula merozoites in bovine turbinate (BT) cell cultures is described and compared with development of Sarcocystis neurona merozoites. Merozoites of S. falcatula entered BT cell cultures and increased in size until 3 days post-inoculation when the nucleus of some merozoites developed lobes. Developing schizonts present at 4 days contained a lobed nucleus or appeared multinucleate. A single mature schizont was observed 4 days p.i. Schizonts were numerous 5 and 6 days p.i. Merozoites were produced from blastophores on the schizont. S. neurona merozoites developed to mature schizonts by 3 days p.i. in BT cells and a residual body was often present. Transmission electron microscopy revealed that S. falcatula merozoites possessed more micronemes than did S. neurona merozoites. Our study demonstrates that S. falcatula and S. neurona are not the same parasite.
- Descriptions of two new species of coccidia (Protozoa : Eimeriidae) and redescriptions of Eimeria ivensae and Eimeria odocoilei from captive white-tailed deer, Odocoileus virginianusLindsay, David S.; Upton, S. J.; Hildreth, M. B. (American Society of Parasitology, 1999-12)Two new species of Eimeria were observed in the feces of captive white-tailed deer fawns, Odocoileus virginianus, from Alabama. The first new species was easily recognized because of its small size. Sporulated oocysts are spherical, average 10.2 by 10.0 mu m, and lack a micropyle and oocyst residuum. Oocysts contain a polar granule and elongare-ellipsoidal sporocysts that measure 6.7 by 3.1 mu m. A Stieda body is present on the sporocysts. Oocysts were observed in the feces, and gamonts and oocysts were observed in the jejunum of a month-old fawn from Minnesota that died from enteritis due to this species. Oocysts of this small species were present in 5 of the 6 white-tailed deer fawns examined. Oocysts of a second new species are ellipsoidal and average 29.5 by 24.6 mu m. The oocyst encloses an oocyst residuum, polar granule, and elongate-ellipsoidal sporocysts that average 16.0 by 9.0 mu m. A Stieda body and substieda body are present an the sporocysts. Oocysts of the second new species were present in 4 of the 6 white-tailed deer fawns examined. Oocysts of E. ivensae are ovoid or flask-like and average 32.0 by 20.8 mu m The oocyst wall is rough, contains a micropyle, and encloses elongate-ellipsoidal sporocysts that average 16.5 by 7.8 8.8 mu m A Stieda body is present on the sporocysts. Oocysts of E. ivensae were present in 4 of the 6 white-tailed deer fawns. Oocysts of E. odocoilei are spherical or slightly subspherical and measure 24.7 by 21.5 mu m. They enclose ovoid sporocysts that average 12.7 by 8.8 mu m. A Stieda and substieda body are present on the sporocyst. Oocysts of E. odocoilei were present in 4 of the 6 white-tailed deer fawns.
- Current strategies in parasite control in Virginia beef cattleCurrin, John F.; Whittier, W. Dee (Virginia Cooperative Extension, 2000)
- Feeder and stocker health and management practicesCurrin, John F.; Whittier, W. Dee (Virginia Cooperative Extension, 2000)
- Determination of the activity of diclazuril against Sarcocystis neurona and Sarcocystis falcatula in cell culturesLindsay, David S.; Dubey, Jitender P. (American Society of Parasitology, 2000-02)Diclazuril is a benzeneacetonitril anticoccidial that has excellent activity against the extraintestinal stages of Toxoplasma gondii and Neospora caninum. It also is highly active against intestinal coccidia of poultry. The present study examined the efficacy of diclazuril in inhibiting merozoite production of Sarcocystis neurona and Sarcocystis falcatula in bovine turbinate cell cultures. Diclazuril inhibited merozoite production by more than 80% in cultures of S. neurona or S.falcatula treated with 0.1 ng/ml diclazuril and greater than 95% inhibition of merozoite production was observed when infected cultures were treated with 1.0 ng/ml diclazuril. Diclazuril may have promise as a therapeutic agent in the treatment of S. neurona-induced equine protozoal myeloencephalitis in horses and S. falcatula infections in birds.
- Sarcocystis campestris from naturally infected 13-lined ground squirrels, Spermophilus tridecemlineatus tridecemlineatus, from NebraskaLindsay, David S.; McKown, R. D.; Dubey, Jitender P. (American Society of Parasitology, 2000-10)Grossly visible sarcocysts were seen in the skeletal muscles of 1 of 12 13-lined ground squirrels, Spermophilus tridecemlineatus tridecemlineatus, collected in Nebraska. The tissue cyst wall was up to 5.0 mum thick and contained spikelike projections. Transmission electron microscopy of tissue cysts revealed they were similar to Sarcocystis campestris Cawthorn, Wobeser, and Gajadhar, 1983, previously known only from experimental infections in Richardson's ground squirrel Spermophilus richardsonii. Prominent electron-dense bodies were observed lining the microfilaments present in the spikelike projections of the sarcocyst wall. This is the first report of S. campestris in a natural intermediate host and the first report of this parasite outside of Saskatoon, Canada.