Recent advances in filtered-air positive-pressure (FAPP) housing for the production of disease-free chickens.

Design and performance information on a filtered-air positive-pressure (FAPP) housing system for disease-free poultry flocks is presented. The system includes many special features that result in excellent biological security, easy cleanup and maintenance, efficient control of environment, and a centralized alarm in the event of problems. The system has now housed eight flocks without any major problems. Based on its performance thus far, it should be useful as a reliable housing system for disease-free poultry.

Pathogenicity of Escherichia coli in aerosols for young chickens.

The relative pathogenicity of Esherichia coli isolates from poultry was determined by aerosol exposure of young chickens. Evidence of colisepticemia with airsacculitis and/or pericarditis and perihepatitis was evaluated. A system was devised that included the intratracheal (IT) inoculation of strain SE-17 infectious bronchitis virus (IBV) of chicks at 7 days of age followed by their aerosol exposure to E. coli culture suspensions 2 days later. Each experiment was terminated 6 days later. For comparative purposes in some studies, chicks were housed at 17 C and others at 27 C. The IBV-E. coli challenge procedure proved to be an effective way to determine the relative ability of E. coli isolates to cause death and/or gross lesions in young chickens. With some E. coli isolates, there were minimal or no obvious adverse effects from exposure except when chickens were previously inoculated with IBV. When chicks were housed at 17 C instead of 27 C, slight increases in mortality and decreases in gross lesions were generally observed, probably because the earlier deaths did not allow time for the lesions to become as evident. The E. coli isolate #18344 (Congo Red-positive) was consistently more pathogenic than the Congo Red-negative version of that isolate. Cultures of E. coli previously demonstrated to be pathogenic (VA O1:K1 and DL #29) were among the most pathogenic isolates evaluated in these experiments and were similar to the Congo Red-positive #18344 isolate.(ABSTRACT TRUNCATED AT 250 WORDS)

Congo red binding by Escherichia coli isolates from chickens.

An attempt was made to use a recently reported special Congo red medium to determine the pathogenicity of Escherichia coli isolates obtained from chickens. The inclusion of bile salts in the Congo red medium as described in previous reports by others was found in the current experiments to cause the production of red colonies from almost all E. coli cultures tested, including known Congo red-negative control cultures. Cultures of E. coli, regardless of their pathogenic history, rarely produced red colonies on the Congo red medium without added bile salts. Numerous isolates of other bacterial genera were examined and found to produce red colonies on the Congo red medium with or without added bile salts.

Nonspecific reactions to Mycoplasma serum plate antigens induced by inactivated poultry disease vaccines.

Nonspecific serum plate agglutination reactions to some avian mycoplasma antigens were induced by injecting chickens with several commercial poultry disease vaccines. All of the vaccines were inactivated, and most of them had oil-emulsion adjuvants. The serum plate agglutination reactions appeared within 2 to 3 weeks post-vaccination and generally persisted for several weeks. The plate test reactions were noted with both Mycoplasma gallisepticum (MG) and M. synoviae (MS) antigens, although the degree and duration of the reactions varied with the vaccine involved and the source of MG and MS plate test antigens. Attempts to prevent the nonspecific reactions by heat-inactivation at 56 C for 30 minutes or by addition of equal volumes of solutions of 2-mercaptoethanol, dithiothreitol, or 3 M sodium chloride were ineffective. No hemagglutination-inhibition activity against MG or MS antigens was induced by the vaccines.

Serological monitoring of eastern wild turkeys for antibodies to Mycoplasma spp. and avian influenza viruses.

From 1981 through 1986, plasma or serum samples were obtained from 322 wild turkeys (Meleagris gallopavo) from Georgia (n = 111), Kentucky (n = 21), Louisiana (n = 22), North Carolina (n = 118), Tennessee (n = 19), Missouri (n = 24) and Iowa (n = 7). These samples were tested for antibodies to Mycoplasma gallisepticum (MG) and in most instances, M. synoviae (MS), M. meleagridis (MM), and avian influenza (AI) virus. All 322 turkeys were seronegative for MG by the rapid plate agglutination (RPA) test. All of a subsample (n = 147) also were negative (titer less than or equal to 1:40) for MG by the hemagglutination inhibition (HI) test. Five of 253 turkeys (2%) were seropositive (+4 reaction) for MS by the RPA test; however, HI tests for MS on these five turkeys were negative as were attempts to isolate MS from trachea and homogenized lung tissue. Three of 253 turkeys (1%) were seropositive (+1 to +3 reactions) for MM by the RPA test. None of 210 turkeys had antibodies to AI by the agar gel precipitation test. These data suggest that populations of native eastern wild turkeys are not important in the epizootiology of MG, MS, MM, or AI.

A historical account of the diagnosis and characterization of strains of Mycoplasma gallisepticum of low virulence.

Numerous chicken flocks were studied beginning in 1970 because of questionable results on their serologic tests for Mycoplasma gallisepticum (MG). Typically a low number of hens in the flocks were positive reactors to the rapid serum plate test and rarely had hemagglutination-inhibition (HI) titers over 1:80. Usually no clinical signs were observed. Isolates of MG eventually were cultured from most of the flocks that exhibited that type of marginal serologic pattern. In the laboratory, the MG isolates were frequently less virulent and less pathogenic than the typical field isolates recovered in previous years. Most isolates produced airsacculitis of varying severity when broilers were exposed to the MG cultures as aerosols following exposure to infectious bronchitis virus. They became positive on the rapid serum plate test and developed moderate to high HI titers. Egg-transmission appeared to be the most likely means of transmission, even though the infected progeny rarely showed clinical signs of disease.

Reversion to virulence of chicken-passaged infectious bronchitis vaccine virus.

Serial passage of two infectious bronchitis virus (IBV) vaccine strains in chickens enhanced their capacity to increase the incidence and severity of Mycoplasma synoviae (MS) airsacculitis. Included in this report were the mild Massachusetts-type Connaught strain and the Arkansas 99 vaccine strain of IBV. The Connaught strain and one of two Ark 99 vaccine strains passaged in chickens increased the incidence of airsacculitis markedly compared with nonpassaged virus. The other Ark 99 vaccine virus already exacerbated MS airsacculitis, before passage in chickens, and its influence did not increase on passage. All IBV strains studied to date have either possessed this trait or reacquired it on passage in the natural host.

Efficacy of experimental inactivated mycoplasma gallisepticum oil-emulsion bacterin in egg-layer chickens.

Six groups of white leghorn pullets were studied to determine the ability of beta-propiolactone-inactivated Mycoplasma gallisepticum (MG) oil-emulsion bacterins to counteract reductions in egg production caused by MG infection. The pullets were inoculated with 0.5 ml of MG bacterin subcutaneously in the neck at about 20 weeks of age and were challenged with MG near 28 weeks of age, when they were in peak egg production. Various challenge schemes with infectious bronchitis virus were used at the time of MG challenge to increase the reduction in egg production. MG bacterins afforded protection against moderate drops in egg production in at least three of the studies, where the unvaccinated challenged control hens exhibited reduced egg production.

Increased incidence of airsacculitis in broilers infected with mycoplasma synoviae and chicken-passaged infectious bronchitis vaccine virus.

Infectious bronchitis vaccine virus is thought to cycle (i.e., pass from vaccine-virus-infected to susceptible chickens) in commercial broiler and pullet flocks. To simulate the effect of this cycling, mild infectious bronchitis vaccine virus was passaged in chickens serially six times. This sixth passage virus was used to infect chickens, which were then exposed to a moderately cold environment of 10 +/- 2 C and to Mycoplasma synoviae. In two separate experiments, the chicken-passaged vaccine virus resulted in a marked increase in the incidence of airsacculitis compared with nonpassaged vaccine virus. Intermediate passage levels also increased airsacculitis incidence but not as much as the sixth passage virus. In another experiment, virus chicken-passaged by contact transmission also caused increased airsacculitis incidence.

Evaluation of inactivated Mycoplasma gallisepticum oil-emulsion bacterins for protection against airsacculitis in broilers.

Broiler chicks were vaccinated subcutaneously in the neck at various ages with a single 0.5-ml dose of beta-propiolactone-inactivated Mycoplasma gallisepticum (MG) oil-emulsion bacterin. Four weeks later, vaccinated and control chicks were placed in cold environmental cabinets, infected with infectious bronchitis virus intratracheally, and 2 days later challenged by aerosol exposure to live MG broth culture. All chicks were killed 21 days later and scored postmortem for the rate and severity of airsacculitis produced in each group. Broiler chicks vaccinated at 1 day of age had only slight protection against the development of airsacculitis. Results were variable when chicks were vaccinated at 7 days of age, with little evidence of resistance to airsacculitis. However, when broiler chicks were vaccinated with MG bacterins at 11 to 15 days of age, they acquired significant protection against airsacculitis compared with controls. Viable MG organisms were readily isolated from most of the sampled tracheas and air-sac lesions cultured 21 days post-challenge, indicating a lack of protection against infection of the respiratory tract. MG-vaccinated chicks generally produced antibodies readily detectable by the rapid serum-plate test, tube-agglutination, and hemagglutination-inhibition (HI) tests. Some of the vaccinated chicks, but none of the unvaccinated control chicks, developed positive reactions to agar-gel-precipitin tests following challenge. Low HI titers at challenge were not necessarily indicative of lack of protection against the development of airsacculitis, since good protection was often observed in chickens with low to moderate HI titers.

Influence of infectious bronchitis strains and vaccines on the incidence of Mycoplasma synoviae airsacculitis.

A model system was used to study infectious bronchitis virus (IBV) and Mycoplasma synoviae (MS) interaction. The system involved exposure of chickens to IBV, followed by exposure to MS 2-5 days later. The chickens were subjected to a cold environment (10 +/- 2 C) for 3 weeks starting one day before MS exposure. Under these conditions, differences in the capacity of various strains of IBV to exacerbate MS airsacculitis was demonstrated. Exposure to IBV field isolates generally resulted in more air-sac lesions than did higher-egg-passaged laboratory strains and vaccine strains. Use of lower-egg-passaged vaccines resulted in a higher incidence of airsacculitis than did higher-egg-passaged vaccines. When chickens were IBV-vaccinated before being used in the model system, the incidence of airsacculitis was lowered, even though the chickens became infected by the challenge virus. Vaccination of MS-free chickens with IBV had no effect on airsacculitis incidence when MS exposure occurred after the vaccine reaction was past.

Preparation of inactivated oil-emulsion vaccines with avian viral or Mycoplasma antigens.

The influence of the composition of water-in-oil emulsions on their physical characteristics was determined by preparing experimental emulsions with various water-to-oil ratios and various emulsifiers. Emulsions containing Tween 80 in the aqueous phase and Arlacel A or Arlacel 80 in the oil phase were lower in viscosity than emulsions containing only an oil-phase emulsifier. Viscosity decreased as the concentration of oil increased. Oil-emulsion vaccines prepared with aqueous- and oil-phase emulsifiers had low viscosity, were stable for more than 12 weeks at 37 C, and induced a marked primary antibody response in chickens.

Identification of avian mycoplasma isolates by the agar-gel precipitin test.

Recent isolates of Mycoplasma gallisepticum and Mycoplasma synoviae were readily typed by the agar-gel precipitin test with antigens prepared by freezing and thawing, sonic vibration, or sodium dodecyl sulfate. Specific antisera prepared in rabbits or in foot-pad-inoculated chickens were adequate for culture typing. Relatively few sera from chickens and turkeys in naturally infected flocks reacted positively. The precipitin reaction was highly specific, however.

Influence of environment on airsacculitis: effects of relative humidity and air temperature on broilers infected with Mycoplasma synoviae and infectious bronchitis.

Mycoplasma synoviae (MS) obtained from broiler chickens condemned for airsacculitis was used to determine the influence of air temperature and relative humidity on the severity of airsacculitis produced experimentally. Infectious bronchitis virus was administered to 3-week-old broilers 5 days before aerosol exposure to MS broth cultures, producing extensive airsacculitis within 21-day study periods. High (31-32 C), medium (19-24 C), and low (7-10 C) air temperatures were studied in conjection with high (75-90%), medium (38-56%), and low (23-26%) relative humidities. Airsacculitis was most extensive (45%) at low temperatures regradless of high or medium humidity. The incidence of airsacculitis was greater (39%) at low humidity than at high humidity (17%) when air temperatures were medium. At high temperature, the trend was toward more airsacculitis (12%) at high humidity than (5%) at low humidity. However, the effect of cold air temperature was more dominant than the effect of relative humidity.