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.

Increasing incidence of anemia among clinically ill Georgia broilers: 1988-89 vs. 1990.

The incidence of anemia in clinically ill Georgia broilers climbed from 66.4% (324/488) during 1988-89 to 80.9% (531/656) during 1990. The incidence of polycythemia fell from 1.6% (8/488) during 1988-89 to 1.5% (10/656) during 1990. Specifically, compared with 1988-89, the 1990 incidence of anemia increased significantly in chicks at age 7 days (P = 0.0002) and 28 days (P = 0.05). We have no certain explanation for this shifting incidence of anemia in clinically ill Georgia broilers. Anemic chicks have plasma that contains virus particles with morphologic characteristics consistent with a virus (chicken anemia agent [CAA]) known to cause anemia in chickens. If CAA is the predominant etiology for anemia in clinically ill Georgia broilers, then our observation could be easily explained. The increasing rate of anemia could indicate a decline in broiler health over time.

Relationship of the enzyme-linked immunosorbent assay to indirect immunofluorescent antibody test for the detection of so-called chicken anemia agent antibodies in serum from broiler breeders.

Serum samples collected from breeder chickens ranging in age from 1 day to 55 weeks were tested for CAA antibodies by enzyme-linked immunosorbent assay (ELISA) and indirect immunofluorescent antibody (IFA) test. The relationship of ELISA to IFA test was determined. The sensitivity of the ELISA relative to the IFA test was 82.64%, and the specificity of the ELISA relative to the IFA test was 56.25%. Agreement between the ELISA and the IFA test was highly significant (Kappa = 0.74, Z = 5.78). We concluded that the ELISA is as good as the IFA test for detecting CAA antibody in sera from chickens.

Incidence of anemia and polycythemia in clinically ill Georgia broilers.

The incidence of anemia and polycythemia was established in clinically ill Georgia broilers that were tested for packed cell volume (PCV) during 1988 and 1989. More than 66% (324/488 = 66.4%) of PCV-tested broiler chicks were anemic, and less than 2% (8/488 = 1.6%) of PCV-tested chicks were polycythemic. The incidence of anemia was significantly (P less than 0.001) higher than expected (2.5%) at age 7 days (56.9%), 14 days (83.9%), 21 days (74.7%), 28 days (58.7%), and 35 days (57.9%). The incidence of polycythemia was significantly (P less than 0.001) higher than expected (2.5%) in 35-day-old broilers (21.1%) but was not significantly different from the expected rate in broilers at age 7 days (0%), 14 days (1.8%), 21 days (0.3%), and 28 days (4.3%). The established rates for anemia were much higher than we would have hypothesized. This led us to believe that either 1) an etiology for anemia is present in epizootic proportions in Georgia broilers, or 2) the standard method for establishing reference intervals for anemia in animals does not apply to broiler chicks.

Relationship of common avian pathogen antibody titers in so-called chicken anemia agent (CAA)-antibody-positive chicks to titers in CAA-antibody-negative chicks.

Antibody titers for infectious bursal disease virus (IBDV), infectious bronchitis virus, Newcastle disease virus, and reovirus from chicks with chicken anemia agent (CAA) antibodies were compared with antibody titers from their CAA-antibody-negative counterparts. These comparisons were made in 396 chickens that were 1 day, 2 weeks, 8-9 weeks, 10 weeks, 17 weeks, or 29-32 weeks old. Only one serum sample was collected from any given chick or chicken. There were no significant differences between the antibody titers at any age for any antigen, with one exception: at 29-32 weeks, the IBDV titers were higher (t = 2.62, df = 142, P less than 0.01) in chickens with CAA antibody. Although not at all likely, we believe that the observation of high IBDV antibody titers in CAA-antibody-positive chicks could have been a spurious one.

Toxicological pathology of cockleburs (Xanthium spp.) for broiler chickens.

Spiking mortality syndrome (SMS) in chickens resembles cocklebur toxicity in cattle, sheep, pigs, and rats. In order to determine if cockleburs are toxic to broiler chicks, crushed burs were fed (25% wt:wt) to broilers for 21 days. Ingestion of cockleburs resulted in significant failure to properly gain body weight. Otherwise, chicks did not develop clinical signs of illness or gross or microscopic lesions. Although there were some significant differences in serum chemistry values among chick groups, there were no consistent patterns. Severe hypoglycemia is said to be a characteristic finding in chicks that die with SMS. Because glucose levels were not low in chicks that were fed cockleburs, we feel certain that cockleburs do not cause SMS.

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.

Clinical, pathological, and epizootiological features of long-segmented filamentous organisms (bacteria, LSFOs) in the small intestines of chickens, turkeys, and quails.

Long-segmented filamentous organisms (LSFOs) are easily recognized gram-positive bacteria that infect several species of animals. The present study describes the epizootiological, clinical, and pathological characteristics of LSFOs in chicks, turkey poults, and quails in Georgia and California. LSFOs are most likely to be seen in young poultry that have gastrointestinal illnesses during winter. Concomitant infections with other bacteria and protozoans are common. Although inflammation and displacement of microvilli are characteristics of LSFO infections in these birds, LSFOs are not necessarily pathogens. They may be normal intestinal flora or commensal organisms that overgrow when certain unknown gastrointestinal conditions are correct or certain unknown events occur.

Pathogenicity of CL-1 chicken anemia agent.

Twelve-day-old broiler-type chickens had hemorrhagic necrotic wing tips. After 10 blind subcultures in an MDCC-MSB1 cell line, a virus (so-called chick anemia agent [CAA]) was isolated and designated CL-1 CAA. Five-day-old specific-pathogen-free chicken embryos from a commercial breeder flock that were found not to possess antibody against CAA were infected with CL-1 virus via yolk-sac injection. Many (49%) infected embryos were small and apparently had died from severe systemic hemorrhage. Hatched chicks were small and had pale feathers, skin, skeletal muscles, bone marrow, and viscera. All infected chicks had small thymuses. These thymuses often were so small that they could not be found grossly (P = 0.002). Anemia occurred within 4 days post-hatch. Microscopically, all hematopoietic organs were markedly atrophic. Septic necrotizing lesions were seen only in organs from CL-1-injected chicks. Physicochemical and pathological characteristics of this virus indicate that it is similar to other isolates of CAA found in Europe and Japan.

Comparison of histopathology to the direct immunofluorescent antibody test for the diagnosis of infectious laryngotracheitis in chickens.

Histopathology and direct immunofluorescent antibody (DIFA) tests were compared for diagnoses of infectious laryngotracheitis (ILT) in 144 cases of spontaneous respiratory disease in chickens presented to the Georgia Poultry Laboratory during 1988. For the 48 cases in which ILT was diagnosed, correct histologic diagnoses were made 100% (48/48) of the time and correct DIFA diagnoses were made 96% (46/48) of the time. For the 96 cases in which ILT was not diagnosed, correct histologic and DIFA diagnoses were made in every case. A Kappa test showed that DIFA was as effective as histopathology for the diagnosis of ILT in chickens (P = 0.0). It was concluded that increased use of DIFA could be instrumental in the abatement of ILT in chickens.

Use of delayed secondary enrichment for the isolation of Salmonella in poultry and poultry environments.

A conventional method of isolating Salmonella was compared with isolation using novobiocin-supplemented plating media and delayed secondary enrichment (DSE). The DSE greatly increased the ability to isolate Salmonella from poultry and environmental samples. Four hundred sixty-four isolations of Salmonella were made from a total of 4377 cultures (11%). Two hundred sixty-nine (58%) isolations of Salmonella were made following the 24-hour incubation; of these, 43 (9%) isolates were isolated only at this time. In comparison, a total of 421 (91%) Salmonella were isolated by DSE, of which 195 isolates (42%) were isolated only with DSE. The addition of novobiocin to the selective plating medium increased the isolation rate for Salmonella and reduced the level of contaminating bacteria growing on the plate.

Unexpected pattern of antibody response of hens following infectious bursal disease virus vaccine.

The antibody titers to infectious bursal disease virus (IBDV) of a group of hens were determined every 2 weeks during the laying period using a kinetic-based enzyme-linked immunosorbent assay (ELISA). When the titers of the flock were regressed against time, the flock titer decayed with statistically significant linearity. However, when the antibody titers of individual hens were measured, their titers regressed on time in a significant quartic curvilinear fashion. Since these hens were not reimmunized, this suggests that a anamnestic response was stimulated from an unknown external source.

The relationship between the hemagglutination-inhibition test and the enzyme-linked immunosorbent assay for the detection of antibody to Newcastle disease.

An assay of 364 chicken serum samples for Newcastle disease virus antibodies determined that a commercial NDV enzyme-linked immunosorbent assay (ELISA) had a 98.2% sensitivity and a 91.7% specificity relative to the NDV HI test. The ELISA values regressed significantly (F = 930, df = 1/362, P less than 0.001) on the hemagglutination-inhibition (HI) titers. The correlational coefficient was 0.85. For individuals, two tests can have the same result based upon chance alone. Kappa is a measure of agreement between two tests that corrects for this chance agreement. The kappa between the ELISA and HI test was calculated to be 0.84 (Z = 7.74, P = 0.00001), which indicates a highly significant agreement between the two tests.

A survey for parvovirus-like virus (so-called chick anemia agent) antibodies in broiler breeders.

A prospective study to survey for the presence of parvovirus-like virus (PVLV; so-called chick anemia agent) antibody in broiler breeder pullets in Georgia, North Carolina, and Florida was conducted by collecting serum samples from 52 breeder flocks that ranged in age from 1 day to 55 weeks old. Results indicated that PVLV infection was widespread. Ninety-eight percent (51/52) of chicken flocks and 62% (530/861) of chickens had PVLV antibody. Rates of antibody-positive chickens among flocks ranged from 0% to 100% and averaged 76%. Upon initial examination, the percentages of chickens positive for PVLV appeared evenly distributed with respect to several convenient age groups and geographic locations. However, compared with young chickens (less than or equal to 19 weeks old), markedly significantly lower proportions of positives were present among chickens more than 19 weeks old (P = 0.00001) or chickens 30 weeks old or more (P = 0.000004). Also, there were significant (F = 7.7, df = 3/827, P less than 0.001) differences among the rates of PVLV antibody in chickens among various companies. The relatively high rate of PVLV antibody among broiler breeder chickens helps explain the low incidence of clinical disease among their offspring.

The relationship of egg yolk and serum antibody. I. Infectious bursal disease virus.

Eggs and serum samples were collected from hens every 2 weeks for 50 weeks from hens caged individually so that the yolk and serum samples could be paired. It was found that the antibody titer of the yolk sample regressed significantly (F = 403.3, df = 1/135, P less than 0.001) on the titer of the serum sample. This permitted the use of the yolk titer to predict the serum titer.

Respiratory cryptosporidiosis in chickens.

In order to better characterize spontaneous respiratory cryptosporidiosis in chickens, a retrospective examination of histopathology reports from the Georgia Poultry Laboratories for an 18-mo period (4/1/86 to 9/30/87) was made; 12 cases were found. Collected data were analyzed and certain epidemiologic and histologic features were identified. Eleven of the 12 cases involved broiler type chickens. The ages of chickens with respiratory cryptosporidiosis were evenly distributed between 17 and 52 days of age. The infected birds were always clinically ill. Viruses or bacteria or both often accompanied respiratory Cryptosporidium sp. infections. Histologic lesions (including those of ciliary-adherent bacteria) are described. As the inflammatory response in infected organs became progressively nonpurulent (lymphocytes and plasma cells predominate), numbers of Cryptosporidium diminished. Cytologic preparations were useful for making diagnoses of respiratory cryptosporidiosis in chickens. Identification of epidemiologic features of respiratory cryptosporidiosis, and improved ability to make accurate and prompt diagnoses of Cryptosporidium sp. infection, are vital for a more complete understanding of the impact of this disease on poultry health.