Biomedical subjects

D H Ley

Publications and source records attributed to D H Ley.

At least 37 records · Page 2Linked to original sources

PubMedDate not supplied

Humoral immune response of turkeys to strain S6 and a variant Mycoplasma gallisepticum studied by immunoblotting.

Two putative variant Mycoplasma gallisepticum (MG) strains (M876 and M35), originally isolated from commercial turkeys, were compared with eight well-characterized MG strains by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). SDS-PAGE protein profiles indicated that the variant strains were correctly classified as MG based on homologous patterns in species-specific regions of the electrophoretic profiles. However, differences in protein profiles also indicated that variant strains M876 and M35 were different from each other and the other MG strains tested. Immunoblotting was used to assess the humoral immune response of turkeys to infection with the S6 reference strain or M876 variant strain of MG. Immunoblots using antisera to M876 showed that seroconversion to this isolate was slower, and to fewer MG proteins when compared with immunoblots using antisera to S6. Immunoblot analyses further indicated that pooled antisera from turkeys inoculated with either S6 or M876 reacted with each of 10 MG strains tested. However, pooled S6 antisera reacted with greater intensity and with more MG proteins than did pooled M876 antisera. The species-specific immunodominant proteins with the greatest potential for use as antigens in serologic tests appeared to be those of 64 (p64) and 56 (p56) kilodaltons molecular mass.

Animals↗

PubMedDate not supplied

Experimental infection of turkeys with Mycoplasma gallisepticum of low virulence, transmissibility, and immunogenicity.

Three-week-old turkeys were inoculated intranasally with approximately 10(6) colony-forming units (CFU) of putative variant Mycoplasma gallisepticum (MG) strains M876, M35, or the virulent S6 reference strain. Uninoculated turkeys in each group served as contact sentinels. The hemagglutination-inhibition (HI) test and enzyme-linked immunosorbent assay (ELISA) were used to determine serologic responses. MG was isolated from 100% and 92% of S6- and M876-inoculated turkeys, respectively, on day 7 PI. However, culture-positive rates among M876-inoculated turkeys declined more rapidly, transmission to contact sentinels took longer and occurred at lower rates, and serologic responses measured by HI and ELISA were lower than in S6-infected turkeys. Testing sera from inoculated turkeys for antibodies to MG in homologous and heterologous ELISA systems indicated that strain M876 was significantly (P less than 0.05) less immunogenic than S6 (days 62 and 95 PI), and that the homologous ELISA was more sensitive (P less than 0.005). MG strain M35 failed to infect turkeys in three attempts, even though the inocula used were viable on culture media.

Animals↗

PubMedDate not supplied

Pasteurellosis in bobwhite quail.

A flock of 5000 six-week-old bobwhite quails (Colinus virginianus) experienced high mortality (52%) over a 2-day period. Mortality was 99% within a 6-day period. Clinical signs were depression followed shortly by death. Gross lesions observed in dead quails were congested lungs and, in a few cases, mottled livers. Histopathologic examination revealed severe, diffuse, heterophilic interstitial pneumonia and multifocal areas of hepatic and splenic necrosis with numerous intracellular and extracellular short bacterial rods. Serotype 3, 4, 15, 16, Pasteurella multocida, isolated from the index case, caused 50% mortality in experimentally inoculated bobwhite quails within 9 to 24 hours. This report indicates that pasteurellosis can cause peracute disease in bobwhite quails with very high mortality.

Animals↗

PubMedDate not supplied

Immune-complex involvement in the pathogenesis of infectious bursal disease virus in chickens.

Frozen kidney sections from chickens inoculated with infectious bursal disease virus (IBDV) were stained with fluorescein-conjugated rabbit anti-chicken gamma-globulin. Fluorescence was observed in the renal glomeruli of infected chickens, indicating that gamma-globulins, probably in the form of immune complexes, had lodged in the glomeruli of IBDV-infected chickens. This suggests that immune complexes may play an important role in the pathogenesis of IBDV infections in chickens.

Animals↗

PubMedDate not supplied

An infectious bursal disease virus outbreak in 14- and 15-week-old chickens.

Infectious bursal disease virus (IBDV) observed in a flock of 14- and 15-week-old chickens was typical of the acute symptomatic IBDV infections more common in younger birds. High flock morbidity was indicated by a marked decrease in feed consumption, although deaths were not excessive. At necropsy, affected birds had small hemorrhages in thigh muscles, creamy-yellow-colored bursae of Fabricius with prominent longitudinal striations, and swollen mottled kidneys. Histopathologic examination revealed bursal lesions typical of IBDV infection. One of six sera from necropsied birds was positive for antibody to IBDV in the agar-gel precipitin (AGP) test, and one week later all 35 samples tested were positive. Bursae were homogenized and found to contain IBDV as evidenced by precipitation, with antibody to IBDV, in the AGP test.

Age Factors↗

PubMedDate not supplied

Experimental reproduction of enteritis in bobwhite quail (Colinus virginianus) with Cryptosporidium and reovirus.

Five-day-old bobwhite quails were inoculated with reovirus and Cryptosporidium previously isolated from the intestinal contents of young, commercially raised bobwhite quails experiencing severe enteritis. Quails inoculated with reovirus alone did not develop clinically apparent disease, infection was localized principally in the intestinal tract, and no lesions were detected. Quails inoculated with Cryptosporidium, alone or with reovirus, developed severe enteritis with high mortality and marked growth depression. Cryptosporidia caused blunting of intestinal villi and provoked a mononuclear cell response in the lamina propria. The severity of intestinal lesions correlated with numbers of parasites. An apparent synergistic effect in dually infected quails was indicated by enhanced Cryptosporidium oocyst shedding, greater numbers of cryptosporidia in the intestinal tracts, and systemic reovirus infection. In addition, multifocal liver necrosis was detected in dually infected quails but was absent in quails infected with only reovirus or Cryptosporidium. The results suggest that Cryptosporidium promoted systemic spread of reovirus, and reovirus intensified Cryptosporidium infection, but no significant synergistic effect on mortality or weight gain was detected. The most important agent in the naturally occurring acute enteritis of bobwhite quails was Cryptosporidium.

Animals↗

PubMedDate not supplied

Interaction of reovirus and Cryptosporidium baileyi in experimentally infected chickens.

No clinical signs, gross lesions, or increased mortality were observed in specific-pathogen-free chickens orally inoculated at 5 days of age with Cryptosporidium baileyi, reovirus 2035, reovirus 2408, or combinations of these agents. Weight gain of chickens inoculated with only reovirus 2408 was depressed 0-8 days postinoculation (PI) (P less than 0.01) but not for the 21-day period PI. Weight gain of chickens inoculated with only reovirus 2035 was not affected. Cryptosporidium baileyi infection significantly depressed weight gain 8-14 days PI but not for the entire 21-day period PI. Weight gain of chickens infected with both C. baileyi and reovirus 2035 was significantly depressed 0-14 days PI and for the entire 21-day period PI. Dual infection with C. baileyi and either reovirus appeared to promote shedding of both agents. Cryptosporidia were found principally in the rectum 2-10 days PI and in the bursa of Fabricius 6-10 days PI. Reovirus infection did not cause any microscopic lesions and did not modify lesions caused by C. baileyi infection.

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PubMedDate not supplied

Experimental cryptosporidiosis and infectious bursal disease virus infection of specific-pathogen-free chickens.

Specific-pathogen-free chickens orally inoculated at 4 days of age with a moderately pathogenic vaccine strain of infectious bursal disease virus (IBDV) and/or at 5 days of age with Cryptosporidium baileyi oocysts remained free of overt clinical signs throughout a 16-day period postinoculation (PI). The prepatency period for C. baileyi oocyst shedding was shorter in chickens receiving higher numbers of oocysts, but once shedding was detected, there were no obvious differences in shedding patterns among groups receiving 10(3) through 10(6) oocysts. On days 8 and 16 PI, cryptosporidia were located primarily in the bursae of Fabricius. IBDV exposure was associated with bursal follicle atrophy, whereas C. baileyi infection resulted in bursal epithelial hypertrophy and hyperplasia, mild follicle atrophy, and heterophil infiltration of the bursal mucosa. Examination of experimental groups of 30 birds each indicated that concurrent infection with both agents resulted in more severe bursal lesions, more infected birds, and greater numbers of cryptosporidia in infected tissues. At the termination of the trial, 16 days PI, Cryptosporidium infection was associated with a 6% decrease in mean body weight compared with controls.

Animals↗

PubMedDate not supplied

Intestinal cryptosporidiosis and reovirus isolation from bobwhite quail (Colinus virginianus) with enteritis.

An acute enteric disease of young pen-raised bobwhite quails was studied. Affected quails had white, watery diarrhea accompanied by dehydration and subsequent death. Mortality from hatch to 17 days of age ranged from 30 to 45% in the three flocks examined. Small intestines were thin-walled and distended with fluid and gas. Microscopic lesions in the intestinal tract consisted of villus atrophy, villus fusion, and sloughing of cells at the tip of the villi in duodenum, jejunum, and ileum. Cryptosporidium sp. and reovirus were identified in affected quails.

Animals↗

PubMedDate not supplied

Intestinal and bursal cryptosporidiosis in turkeys following inoculation with Cryptosporidium sp. isolated from commercial poults.

Cryptosporidium meleagridis oocysts, originally isolated from droppings of commercial turkey poults with increased mortality due to viral (reovirus) hepatitis and enteritis, were treated with peracetic acid to kill companion bacteria and viruses and then propagated by passage in young turkeys. Thirty-eight 5-day-old large white turkey poults were inoculated by crop gavage with 500,000 cryptosporidial oocysts and compared with 40 uninoculated poults. Cryptosporidial oocysts shedding began 3 days postinoculation (PI), peaked on day 4 PI, and persisted at a low level for the duration of the 21-day trial. Low to moderate cryptosporidial infections of the ileal mucosa (days 3, 6, and 15 PI), cecal mucosa (days 3, 6, and 21 PI), and bursa of Fabricius (days 6, 12, 15 and 21 PI) were found on histopathological examination. There were no differences in mean body weights between the inoculated and uninoculated groups, and no mortality or clinical signs of disease were seen in either group.

Animals↗

PubMedDate not supplied

Cryptosporidia-positive rates of avian necropsy accessions determined by examination of auramine O-stained fecal smears.

Fecal smears from 112 avian necropsy accessions representing 431 birds were stained with auramine O and examined for Cryptosporidium oocysts by fluorescence microscopy. Stained Cryptosporidium oocysts fluoresced bright yellow-green and were easily differentiated from extraneous material by their uniform small size (approx. 5 micron) and morphology. The rates of cryptosporidia-positive accessions were 27.3% (9/33) of broilers, 10% (3/30) of broiler breeders, and 5.9% (1/17) of layers. Further analyses of available data for various risk factors that may have influenced rates of cryptosporidia-positive samples in broilers, broiler breeders, and layers failed to show significant relationships. However, it was apparent that positive samples were clustered within accessions and not scattered throughout the population sampled. This survey also resulted in the first reported identification of Cryptosporidium oocysts from a budgerigar, macaw, and tundra swan.

Aniline Compounds↗

PubMedDate not supplied

Staphylococcus-induced gangrenous dermatitis in broilers.

An infectious bursal disease (IBD)-vaccinated flock of 23,900 broilers, 17 days of age, experienced sudden onset of depression, dermatitis, and mortality. Postmortem examination showed extensive subcutaneous serosanguineous fluid accumulation over the pectoral muscles, discrete hepatic whitish foci, fluid-filled intestines, and small, flaccid bursae of Fabricius. Gram-stained impression smears from the affected areas revealed numerous gram-positive cocci. Aerobic culture of liver and subcutaneous tissue consistently produced heavy growth of penicillin-sensitive Staphyloccus aureus. Histopathologically, subcutaneous tissue showed diffuse hemorrhage and large numbers of gram-positive cocci with severe congestion and hemorrhage of the underlying skeletal muscle. Liver sections showed multiple, randomly scattered areas of acute coagulation necrosis with numerous gram-positive cocci. Bursal lesions were characterized by extensive follicular necrosis and collapse. A diagnosis of staphylococcal gangrenous dermatitis secondary to IBD was made. Mortality returned to preinfection levels within 72 hours after penicillin was added to the drinking water.

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PubMedDate not supplied

The pathogenesis of infectious bursal disease: serologic, histopathologic, and clinical chemical observations.

Infectious bursal disease in 35-day-old specific-pathogen-free (SPF) chickens was characterized clinically by its acute onset and brief duration. Clinical signs included depression, anorexia, diarrhea, and polyuria. A detectable precipitin antibody response occurred between 3 and 5 days postinoculation. Evaluation of pooled serum samples obtained from infectious bursal disease virus (IBDV)-infected chickens revealed transient changes in potassium, cholesterol, uric acid, lactate dehydrogenase, serum glutamic-oxalic transaminase, and serum proteins. Individual serum samples analyzed for uric acid concentration indicated that several IBDV-infected chickens had serum uric acid concentrations above the normal comparison range. Histopathologic examination of lymphoid and nonlymphoid tissues from IBDV-infected SPF chickens affirmed that the predominant lesion was lymphoid necrosis in the bursa of Fabricius. Other lymphoid organs were much less severely affected and possessed greater regenerative potential. Nonspecific and relatively mild changes were found in the liver and kidney: hepatic lipidosis and necrosis, renal intratubular crystalline deposits (probably urates), and increased ectopic lymphoid foci. There was no evidence of immune-complex-mediated arteritis/vasculitis in the sartorius muscle or any other tissue examined. Histopathologic and ultrastructural evidence of glomerulonephritis was rare but compatible with acute immune complexemia.

Animals↗

PubMedDate not supplied

Protective immune response to Mycoplasma gallisepticum demonstrated in respiratory-tract washings from M. gallisepticum-infected chickens.

Chickens inoculated with Mycoplasma gallisepticum (MG) produced IgA, IgM, and IgG detectable in washings from the upper respiratory tract (URTW; nasal sinuses and turbinates) and lower respiratory tract (LRTW; trachea, lungs, and air sacs). URTW and LRTW from infected chickens had significant protective effects in a MG-inoculated tracheal-ring-organ-culture system. Protective effects in vitro correlated positively with total MG-specific immunoglobulin titer, but not IgA titer, as determined by enzyme-linked immunosorbent assay. URTW and LRTW from infected chickens inhibited attachment of MG to tracheal-ring-organ cultures in a dose-dependent manner. This suggests that chickens produce a protective immune response to MG that locates in the respiratory tract and that attachment inhibition may be responsible for this protective effect.

Animals↗

PubMedDate not supplied

Inhibition of Mycoplasma gallisepticum growth and attachment to chick tracheal rings by antibodies to a 64-kilodalton membrane protein of M. gallisepticum.

A Mycoplasma gallisepticum (MG) strain R protein of 64 kilodaltons (p64) was partially digested from the surface of the bacterium by trypsin. Monospecific polyclonal anti-p64 IgG inhibited attachment of MG to chick tracheal rings by as much as 69%. However, trypsin treatment of viable MG cells did not reduce attachment to tracheal rings or hemagglutination titer. Anti-p64 IgG inhibited growth of MG strain R in broth and on solid media, inhibited the uptake of radiolabeled thymidine, but did not inhibit hemagglutination. Anti-p64 IgG inhibited growth of eight MG strains on solid medium. The degree of growth inhibition varied widely depending on the strain and correlated positively with the reported virulence of the MG strains with one exception (A5969). An IgG monoclonal antibody to p64 (MyG 001) inhibited growth of MG strain R on solid and in broth media. The strong attachment-inhibition activity of anti-p64 IgG may result from its growth-inhibiting activity. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of MG strains suggested that p64 is expressed in higher amounts in vitro in virulent strains (R, S6) than in strains of low virulence (F, M876, K503, K703, K730). P64 should be used to immunize chickens to determine if it can stimulate a growth and attachment-inhibiting response in the respiratory tract.

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PubMedDate not supplied

Clinical Mycoplasma gallisepticum infection in multiplier breeder and meat turkeys caused by F strain: identification by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, restriction endonuclease analysis, and the polymerase chain reaction.

In February 1991, a flock of North Carolina multiplier breeder turkeys experienced respiratory signs, sinusitis, airsacculitis, and increased mortality. Mycoplasma gallisepticum (MG) was isolated, and appropriate control measures were initiated. Ultimately, this outbreak involved several breeder flocks of an integrated turkey production company before the last infected flock was identified in May 1991. During this time, MG was also isolated from a flock of commercial layer-type chickens raised as pullets in close proximity to the index turkey flock. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and restriction endonuclease analysis indicated that these isolates were identical to each other and to examples of the vaccinal F strain. Additionally, MG isolates from the affected turkey breeder and layer flocks were identified as MG F strain by use of an F strain-specific DNA probe and polymerase chain reaction. A separate outbreak of MG disease in several meat-turkey flocks of a Midwest producer/processor yielded isolates identified as F strain by the polymerase chain reaction. These studies demonstrated: 1) the utility of newer technologies for disease outbreak investigations; and 2) the potential of MG F strain to cause disease in breeder and meat turkeys under field conditions.

Animals↗

PubMedDate not supplied

Efficacy of danofloxacin and tylosin in the control of mycoplasmosis in chicks infected with tylosin-susceptible or tylosin-resistant field isolates of Mycoplasma gallisepticum.

The efficacy of danofloxacin was compared with that of tylosin in the control of induced mycoplasmosis. In three experiments, disease was induced in broiler chicks by intrapulmonary injection of field isolates of Mycoplasma gallisepticum (MG) originating from Brazil, a different isolate being used for each experiment. Starting the day after inoculation, groups of chicks were medicated for 3 days via the drinking water with danofloxacin (50 ppm) or tylosin (500 ppm) or were left as unmedicated controls. Chicks were observed for 21 days. A severe mycoplasmosis was induced in unmedicated birds, characterized by mortality, depression, and respiratory signs. Danofloxacin was highly efficacious in controlling this infection in all three experiments, whereas tylosin was efficacious in only one. This difference could be related directly to the reduced in vitro susceptibility to tylosin displayed by the two isolates of MG. In the two experiments where isolates were tylosin-resistant, danofloxacin was significantly (P < or = 0.05) superior to tylosin in reducing mortality, maintaining weight gain, and reducing the prevalence of air-sac lesions, isolation of MG, and seroconversion.

Air Sacs↗

PubMedDate not supplied

A comparison of danofloxacin and tylosin in the control of induced Mycoplasma gallisepticum infection in broiler chicks.

Experimental mycoplasmosis was induced in 1-day-old chicks by intrapulmonary inoculation of Mycoplasma gallisepticum (MG). This method of infection proved to be useful for evaluating the efficacy of antimicrobial medication, by measuring mortality, weight gain, pathological responses, frequency of reisolation of MG, and seroconversion. Using this model, the efficacies of danofloxacin (a novel fluoroquinolone) and tylosin were compared for two MG isolates, a reference isolate (the R-strain) and a field isolate from California. Danofloxacin administered in the water at 50 ppm for 3 days was equivalent to tylosin at 500 ppm for 3 days in the degree of control of mortality and maintenance of weight gain. Danofloxacin was superior to tylosin in preventing air-sac lesions, reducing the frequency of reisolation of MG, and preventing seroconversion in surviving birds.

Air Sacs↗