Biomedical subjects

J F Davis

Publications and source records attributed to J F Davis.

30 records · Page 2Linked to original sources

PubMedDate not supplied

Comparisons of packed cell volumes (PCVs) from so-called chicken anemia agent (CAA; a virus)-free broilers to PCVs from CAA-free specific-pathogen-free leghorns.

Packed cell volumes (PCVs) from 3-, 7-, 14-, 21-, 28-, and 35-day-old clinically healthy chicken anemia agent (CAA)-free and specific-pathogen-free (SPF) leghorn chicks were compared with PCVs from age-matched clinically healthy CAA-free broiler chicks. The PCVs of the SPF chicks regressed significantly (F = 20.6, df = 2/3, P < 0.025) on age in a linear fashion. The PCVs of the broiler chicks regressed significantly (F = 9.56, df = 2/3, P < 0.05) on age in a cubic parabola. The mean PCVs of the broiler chicks were significantly (P < 0.05) higher than PCVs of SPF chicks at every tested time interval. Results indicate that PCV values are higher in broiler chicks than in SPF leghorn chicks, and that PCVs increase as chicks age. Clinicians, diagnosticians, and investigators who intend to work with chicken blood must be aware of these differences.

Anemia↗

PubMedDate not supplied

Packed cell volume reference intervals to aid in the diagnosis of anemia and polycythemia in young broiler chickens.

Packed cell volume (PCV) reference intervals were established for use in diagnosing anemia and polycythemia in young broiler chickens. Blood samples were collected from one hundred twenty 3-to-49-day-old clinically healthy conventionally reared broiler chickens. PCVs were determined and analyzed. PCVs regressed significantly (P less than 0.025) on age, which shows that neonatal physiologic anemia occurs in broiler chickens, as well as in mammals and specific-pathogen-free (SPF) chickens. The definition for anemia in broiler chicks varies with age. We defined anemia as a PCV less than or equal to 26%, 29%, 33%, 32%, 33%, 33%, 31%, and 28% for broiler chickens, 3, 7, 14, 21, 28, 35, 42, and 49 days old, respectively. We define polycythemia as a PCV greater than or equal to 42%, 43%, 41%, 40%, 42%, 42%, 41%, and 40% for broiler chickens 3, 7, 14, 21, 28, 35, 42, and 49 days old, respectively. Otherwise, broiler chickens have PCVs within established reference intervals. Results provide guidelines for detecting anemia and polycythemia in young broiler chickens of various ages.

Analysis of Variance↗

PubMedDate not supplied

Pathobiology of cryptosporidiosis (C. baileyi) in broiler chickens.

Pathologic and clinicopathologic changes were examined in broiler chickens inoculated with Cryptosporidium baileyi (Cb) alone or in combination with infectious bronchitis virus (IBV), infectious bursal disease virus (IBDV) or Escherichia coli (Ec). Concurrent infections with Cb and either IBV or Ec resulted in a greater respiratory inflammatory response than either agent given alone. Concurrent Cb, IBV or Ec infections resulted in a decreased density of respiratory cryptosporidial stages. No interactions between Cb and IBDV were observed. Clinicopathologic results in broiler chicks exhibiting signs of respiratory cryptosporidiosis indicated that pO2 decreased, pCO2 increased, HCO3 increased and CO2 increased. Changes in blood gases and serum electrolyte values correlated with signs of acute respiratory disease. Blood gases and serum electrolyte values were unchanged in birds with bursal and cloacal infections only. Results of these studies clarified pathogenetic events associated with avian respiratory cryptosporidiosis, and demonstrated that cryptosporidiosis may enhance the severity of respiratory disease caused by other avian pathogens.

Animals↗

PubMedDate not supplied

Diagnoses of infections by the so-called chick anemia agent: anemia and direct transmission electron microscopic detection of virus.

Blood from 48 chicks was examined for anemia (packed cell volume), and plasma was examined for virus particles by direct transmission electron microscopy (DTEM). There was agreement between the occurrence of anemia and the presence of CAA virus particles in plasma from anemic chicks (Kappa = 0.2425, Z = 2.096, P = 0.036). Although DTEM is a method that can be used to diagnose CAA in chicks, more sensitive, economical and less laborious diagnostic assays are needed.

Anemia↗

PubMedDate not supplied

Markedly reduced pancreatic glucagon levels in broiler chickens with spiking mortality syndrome.

Pancreata from 19 hypoglycemic field broilers with spiking mortality syndrome and 19 clinically normal field broilers with normal blood glucose levels were collected and quick-frozen in liquid nitrogen immediately after the chicks were bled and killed. All chicks were 16 days old and were of the same genetic cross. Pancreata were weighed, and acid-alcohol extractions were made on each specimen. Radioimmunoassays for glucagon levels were made on each extract. Mean pancreatic glucagon content of the hypoglycemic chicks was depressed 14-fold (93.1%) compared with that of the non-hypoglycemic group. There was a close correlation between plasma glucose levels and pancreatic glucagon levels (P = 0.0001).

Animals↗

PubMedDate not supplied

Hypoglycemia, enteritis, and spiking mortality in Georgia broiler chickens: experimental reproduction in broiler breeder chicks.

The clinical signs, hypoglycemia, and mortality of "spiking mortality syndrome" were experimentally reproduced. Seven groups of day-old male primary broiler breeder chicks were orally inoculated with tissue and/or fecal-urate homogenates taken from field broilers with spiking mortality syndrome and from field broilers with enteritis and/or runting-stunting syndrome. All homogenates used as inocula were shown by transmission electron microscopy and negative staining to contain arenavirus-like particles. Inocula produced from field broilers with spiking mortality syndrome contained the highest numbers of the arena-virus-like particles and produced the highest percentage of hypoglycemic chicks 13-15 days postinoculation after a 5-to-9-hour fast. These homogenates also produced the most significant differences in mean plasma growth hormone and insulin-like growth factor-1 levels. The significance of the arenavirus-like particles is unknown but is currently being investigated.

Animals↗

PubMedDate not supplied

Enteritis (so-called runting stunting syndrome) in Georgia broiler chicks.

So-called runting stunting syndrome (RSS) afflicts chicks worldwide. The present study in Georgia chicks is the first report of unique histologic features of RSS pathology in chicks in the United States. Various combinations of avian nephritis virus, enterovirus-612, and reovirus were always isolated from chick small intestines. Ultrastructurally, only small round viruses were seen in small intestinal lesions. Although finding intralesional virus in small intestinal segments from chicks with signs and gross lesions consistent with RSS constitutes a reasonable criterion for making a diagnosis of this disease, chicks without intralesional viruses and with bacterial or protozoal enteritis may also be small and abnormally feathered. Because just what constitutes RSS remains a diagnostic dilemma, we recommend that the use of the imprecise acronym "RSS" be discontinued.

Animals↗

PubMedDate not supplied

Virus isolation accuracy: an evaluation of eight laboratories involved in poultry diagnostics.

A study was undertaken to evaluate the accuracy of diagnostic laboratories at isolation of common avian viral pathogens. Fourteen "unknown" samples were submitted to eight laboratories in seven states. All positive and negative samples were guaranteed pure by SPAFAS. Virus-isolation results were erroneous in many cases. Based on this study, it appears that protocol for virus isolation of avian pathogens should be standardized throughout the United States.

Animals↗

PubMedDate not supplied

Reovirus-associated enteritis in Georgia broiler chicks.

The histopathology of reovirus-infected small intestines from clinically ill commercial broiler chicks afflicted with so-called runting stunting syndrome is described. We do not speculate that a cause-and-effect relationship necessarily exists between intralesional reovirus and illness in chicks in the present study. We propose that, in the future, similar cases be termed reovirus-associated enteritis (RAE). RAE must be differentiated from lesions attributed to infections by enterovirus-like particles.

Animals↗

PubMedDate not supplied

Experimental reproduction of severe hypoglycemia and spiking mortality syndrome using field-derived and embryo-passaged preparations.

The clinical signs, enteritis, weight depression, and hypoglycemia of spiking mortality syndrome were experimentally reproduced in broiler breeders and broiler chicks. Inocula included 1) virus-like particles from intestines of chicks with spiking mortality syndrome that had been banded in a discontinuous Renograffin gradient, 2) homogenized darkling beetles collected from litter of farms where spiking mortality syndrome had occurred repeatedly, and 3) homogenized embryos which had been inoculated with the Renograffin-banded material. Arkansas variant infectious bronchitis virus and arenavirus-like particles were identified in the inocula. Serology on samples from surviving chicks suggested the presence of an avian encephalomyelitis virus in one of the inocula. One-day-old (n = 172) and 2.5-day-old (n = 30) chicks were inoculated orally, and some were also injected intraperitoneally or subcutaneously, with 0.5 ml of the inocula. Twelve to fourteen days postinoculation, chicks were fasted for 4-6 hours, then briefly stressed with a cool water spray. Within 1.5 hours, inoculated chicks began dying with severe hypoglycemia and clinical signs of spiking mortality syndrome. Body weights were significantly depressed. Uninoculated controls (n = 130) from the same hatches, also fasted and stressed, were unaffected clinically and were not hypoglycemic. One group (n = 52) of inoculated chicks exposed to a controlled lighting program was unaffected clinically, had significantly higher mean plasma glucose levels, and had significantly less body weight depression than chicks exposed to continuous lighting. We concluded that exposure to controlled amounts of light/darkness can ameliorate much of the hypoglycemia, mortality, and runting-stunting associated with spiking mortality syndrome of chickens. The significance of the viruses and virus-like particles detected in the inocula is currently under investigation.

Animals↗

PubMedDate not supplied

Experimental reproduction of a spiking mortality syndrome of turkeys.

Two-day-old turkey poults were inoculated with either a chicken embryo homogenate used previously to produce spiking mortality syndrome in chickens (the "Oakwood Agent") or an intestine-pancreas homogenate collected from field turkeys with the syndrome known as spiking mortality of turkeys. Twelve days postinoculation, the mean plasma insulinlike growth factor-1 (IGF-1) level and mean body weights were significantly depressed, and the mean plasma growth hormone level was significantly elevated, in the poults receiving the turkey-derived homogenate (P < or = 0.0003), as was previously reported in chickens with spiking mortality syndrome. The depression in plasma IGF-1 levels may explain the runting seen in poults that survive spiking mortality of turkeys in the field. Following a 4-hr fast and a brief cool water spraying, poults exhibited clinical signs indistinguishable from those of chicks with spiking mortality syndrome. However, plasma glucose levels in the affected poults were within the normal range, unlike chickens with spiking mortality syndrome. Immunohistochemistry on formalin-fixed intestines, ceca, and bursae produced positive staining using an arenavirus antibody in epithelial cells of poults inoculated with the turkey homogenate and those inoculated with the Oakwood Agent. Tissues of uninoculated controls were negative. Poults inoculated with the Oakwood Agent did not show noticeable disease.

Animals↗

PubMedDate not supplied

Experimental reproduction of hypoglycemia-spiking mortality syndrome in broiler chickens with the use of homogenized brains containing arenaviruslike particles.

Severe hypoglycemia-spiking mortality syndrome was experimentally reproduced in broiler chicks. Inoculum was homogenized brains from 28-day-old commercial broiler chicks with central nervous system signs (50% [v/v] in phosphate-buffered saline with 2% fetal calf serum). Oral inoculations of 1.2 ml of the homogenate were given at 1 day of age to broiler chicks (n = 15). Fourteen days later, chicks were fasted and stressed with a 2-sec cool water spray. Six chicks (40%) developed clinical signs of spiking mortality syndrome and were severely hypoglycemic. Uninoculated control chicks (n = 15) from the same hatch, also fasted and stressed simultaneously, were unaffected. Examination of a banded fraction produced from the inoculum with the use of transmission electron microscopy with negative staining revealed viruslike particles indistinguishable from arenavirus particles stained and examined simultaneously. Avian encephalomyelitis virus was isolated by one of three laboratories attempting virus isolation with the use of embryonating chicken eggs.

Animals↗