A comparison of immune responses of broiler chickens to different methods of vaccination against Newcastle disease.

One-day-old broiler chicks from 4 groups of broiler breeder chickens were immunized by different methods of vaccination: 1) aerosol; 2) intratracheal; 3) drinking water; or 4) unvaccinated. The breeder flock from which the chicks were derived was vaccinated by one of the following methods: 1) a single injection of an oil-emulsion Newcastle disease virus (NDV) vaccine; 2) two vaccinations with oil-emulsion NDV vaccine; 3) vaccination with a live NDV vaccine; and 4) unvaccinated controls. Aerosol vaccination induced higher serologic responses than water and intratracheal vaccination, as well as giving the highest levels of protection against challenge. Mortality ranged from 20% to 66% in all eight groups of birds vaccinated intratracheally and challenged at 6 weeks of age. Results of challenge tests, in agreement with results of HI tests, further demonstrated that intratracheal vaccination at one day of age does not elicit a satisfactory immune response in birds with a maternal antibody titer of 15 or higher.

Immunization of broiler breeder chickens against Newcastle disease with an oil-emulsion vaccine.

Antibody response was rapid and high in broiler breeder chickens receiving 1 or 2 vaccinations with oil-emulsion vaccine against Newcastle disease at 23 or at 23 and 26 weeks old. The antibody titers remained high during the 41-week experimental period. At 64 weeks old, about 41 weeks after vaccination, the geometric mean hemagglutination-inhibition antibody titer was 67 from the single vaccination, and 103 from the double vaccination. The immune response to live-virus vaccine given at 2, 9, 20, 30, 42, or 54 weeks of age via the drinking water was high, but uniformity was lacking in the antibody response in the breeders and maternal antibody response in the progeny. Maternal antibody levels in one-day-old chicks were related to the titers of antibody in the dams. Maternal antibody titers of chicks originated from breeder flocks that were vaccinated with the oil-emulsion vaccine remained high for all hatches.

Airsacculitis induced in broilers with a combination of Mycoplasma gallinarum and respiratory viruses.

Mycoplasma gallinarum was isolated from tracheas and air-sac lesions from broilers in flocks having higher than normal condemnations due to airsacculitis. A representative M. gallinarum isolant, given by aerosol or by air-sac inoculation, produced air-sac lesions in young chickens when given in combination with a vaccine combining Newcastle disease and infectious bronchitis or with a field strain of infectious bronchitis virus.

Studies on interferon induction by infectious bursal disease virus (IBDV). II. Interferon production in White Leghorn chickens infected with an attenuated or pathogenic isolant of IBDV.

Infectious bursal disease virus (IBDV) isolants that differed in virulence for chickens, were compared as to: 1) induction of interferon in serum and tissues; and 2) stimulation of IBDV serum antibody. Specific-pathogen-free chickens were infected at one day and four weeks of age by the subcutaneous and intranasal routes of inoculation. The pathogenic isolant induced a more generalized interferon response than the attenuated isolant, independent of age or route of inoculation. Pathogenic IBDV stimulated interferon in serum, kidney, lung, thymus, spleen, and bursa of Fabricius. The attenuated virus induced interferon only in the bursa. The serum interferon response was greater following inoculation with pathogenic IBDV than with the attenuated virus. Serum interferon titers peaked 2-3 1/2 days after inoculation. The pathogenic and attenuated viruses stimulated similar IBDV-neutralizing antibody responses, which occurred after peak serum interferon activity.

A comparison of the efficacy against Marek's disease of cell-free and cell-associated turkey herpesvirus vaccine.

One-day-old White Leghorn and broiler chicks with maternal antibody to turkey herpesvirus (HVT) were vaccinated with 300 or 1,000 plaque-forming units (PFU) of cell-free or cell-associated HVT vaccine and challenged with virulent Marek's disease virus (MDV) by contact exposure. Broiler chicks receiving 300 PFU of cell-associated HVT had a 3.3% incidence of MD lesions, whereas only 2.0% of those receiving 1,000 PFU had macroscopic lesions. Broiler chicks vaccinated with 300 PFU of cell-free vaccine had 6.8% gross lesions, and 0.67% of the birds receiving 1,000 PFU had MD lesions. Unvaccinated broiler chickens had a 28.3% incidence of MD lesions. Unvaccinated White Leghorn chickens had a 48.9% incidence of macroscopic lesions, whereas 5.4% of the birds receiving 300 PFU of cell-associated HVT had gross lesions, and 8.3% of the birds vaccinated with 1,000 PFU had lesions. In contrast, 6.7% of the chicks vaccinated with 300 PFU of cell-free HVT had MD lesions, and only 4.0% of those receiving 1,000 PFU of cell-free HVT had macroscopic lesions.

Studies on interferon induction and interferon sensitivity of avian reoviruses.

Four strains of avian reovirus were ineffective inducers of interferon (IFN) in chicken kidney (CK) cell cultures. All strains were similar in single-cycle replication curves. At multiplicities of infection between 0.20 and 10 plaque-forming units per cell, IFN was not induced in CK cells. Reovirus did not produce an IFN blocker in CK cells. Attenuated reovirus did induce IFN in aged chicken embryo fibroblast (CEF) cell cultures. By priming cells with a low dose of IFN before infection with reovirus, IFN formation by CEF could be enhanced. Ultraviolet-inactivated avian reovirus was an effective inducer of IFN in both CK and CEK cell cultures. The sensitivity of avian reoviruses (Fahey-Crawley, Reo-25, S-1133, Reo-V) to chicken interferon (Ch-IFN) was studied by the plaque-reduction method. Avian reoviruses were less sensitive to Ch-IFN than was vesicular stomatitis virus or Semliki Forest virus and appeared to be as resistant to IFN as was Newcastle disease virus.

Demonstration of Eimeria tenella in bursa of Fabricius of chickens.

Coccidial life-cytle stages were detected in the bursa of Fabricius of broiler chickens inoculated with Eimeria tenella, whether or not the chickens had previously been infected with infectious bursal disease virus (IBDV). Chickens infected only with E. tenella had developing parasites in the lining epithelium, whereas chickens with both infections had gametocytes also in the epithelial cells surrounding numerous degenerating bursal cysts.

Viral tissue tropisms and interferon production in white leghorn chickens infected with two avian reovirus strains.

Inoculation of 6-day-old and 4-week-old chickens with pathogenic or attenuated avian reovirus resulted in an inapparent infection. The virus had a greater tissue distribution and persisted longer in tissues of 6-day-old chickens. Interferon was detected in only the serum and lung of infected chickens and appeared to be related to route of inoculation. Titers of interferon were greater and appeared sooner in the tissues of older chickens. Reovirus-neutralizing antibody was not detected in the serum of chickens of either age 120 days postinfection.

Interaction of aflatoxin with infectious bursal disease virus infection in young chickens.

Young White Leghorn chickens fed 2.5 microgram of aflatoxin (Afl) per g of diet from hatching until 4 weeks old and infected with infectious bursal disease virus (IBDV) at 3 weeks old had significantly higher mortality and more severely depressed body weights than chicks with aflatoxicosis or IBD alone. Afl-IBDV chicks also had more extensive gross and microscopic changes characteristic of IBD than did IBDV-chicks. None of the treatments significantly reduced antibody responses to Newcastle disease(ND) and infectious bronchitis vaccines or increased susceptibility to challenge with virulent NDV. In a similar experiment chickens fed Afl from hatching to 7 weeks of age had no marked depression in immune response to ND vaccination.

Effect of infectious bursal agent on the response of chickens to Newcastle disease and Marek's disease vaccination.

White Leghorn chickens raised from one day old in an environment contaminated by the infectious bursal agent (IBA) had lower geometric mean titers (GMT) as measured by the hemagglutination-inhibition (HI) test to the Newcastle disease virus (NDV), than control Leghorns reared in an uncontaminated environment. Immunosuppression, defined as a reduction in GMT, was most pronounced at 35-56 days old for Leghorns vaccinated with NDV at 1 and 28 days or at 28 days. In a separate trial with broilers, immunosuppression was similar at 42-56 days old. This study also demonstrated that IBA infection in chickens increased susceptibility to Marek's disease (MD). The unvaccinated control chickens infected with IBA averaged 56.3% MD lesions, whereas unvaccinated controls not exposed to IBA averaged only 18.1% macroscopic lesions. It was also found that 20.7% of the HVT-vaccinated chickens exposed to IBA had gross MD lesions, whereas those HVT-vaccinated chickens reared in an environment free of IBA had 2.99% gross MD lesions.

Effect of infectious bursal disease on the response of chickens to Mycoplasma synoviae, Newcastle disease virus, and infectious bronchitis virus.

At 35 days of age, chickens which as 1-day-old chicks were inoculated with the infectious bursal disease virus (IBDV) had significantly lower antibody titers against Mycoplasma synoviae, Newcastle disease virus, and infectious bronchitis virus than did those never inoculated with IBDV. The IBDV also had a marked effect on the development of air-sac lesions. Birds infected with IBDV that were later inoculated with M synoviae (day 14), Newcastle disease virus (days 14 and 28) experienced an increased incidence and greater seversity of airsacculitis than did chicks which were not exposed to IBDV.

Effect of aflatoxin on the humoral and cell-mediated immune systems of the chicken.

Chickens fed 2.5 microgram of aflatoxin/g of diet from 2 to 4 weeks of age or from hatching to 4 weeks were deficient in cell-mediated immunity, as measured at 4 weeks of age by the graft-versus-host reaction. Delayed-type hypersensitive skin reactions to tuberculin were also reduced in chickens given dietary aflatoxin from hatching to 7 weeks of age. Humoral immunity, as measured by the ability of 4-week-old chicks to produce natural agglutinins to rabbit red blood cells, was not significantly altered by dietary aflatoxin. A significant decrease in concentrations of serum immunoglobulins (Ig) IgG and IgA, but no IgM, however, did occur in chicks given dietary aflatoxin from hatching to 4 weeks or between 2 and 4 weeks of age. Aflatoxin consumption from 0 to 2 weeks of age produced no marked effect on either cell-mediated or humoral immunity in 4-week-old chicks.

Specific suppression of the bursa-dependent immune system of chicks with infectious bursal disease virus.

Chicks which had been inoculated with infectious bursal disease virus (IBDV) at 1 day of age had a severe depression of bursa-dependent humoral immune functions by day 42. Antibody responses against rabbit red blood cells or to immunization with bovine serum albumin were significantly suppressed. In contrast, chicks inoculated with IBDV at 21 days of age produced near normal antibody responses as compared with the responses in noninfected control chicks. The IBDV had no significant effect on the thymus-dependent cellular responses as measured by skin graft rejection or delayed type hypersensitivity reactions to tuberculin.

Application of the cell-free turkey herpesvirus vaccine by the aerosol route for the prevention of Marek's disease in chickens.

In field trials approximately 300,000 birds were vaccinated against Marek's disease (MD) by aerosol spray with 1,000 to 5,000 PFU of cell-free HVT vaccine per chick. Chicks were sprayed in the trays of the hatchers which still contained dust and down after hatching. Prior to spraying, the incoming and outgoing air ducts were closed. The chicks were sprayed for 12--15 min. with HVT in 250 to 300 ml. of diluent, and after completion of spraying the chicks remained in contact with the aerosol for approximately 10 minutes. In birds vaccinated by aerosol spray the incidence of MD ranged from 0.0% to 24.4%; while the incidence of MD in birds vaccinated by subcutaneous inoculation varied from 0.02 to 23.9%. In trial 1 the incidence of MD in birds vaccinated by aerosol spray was essentially the same as those vaccinated by subcutaneous inoculation; whereas, the incidence of MD (Trial 2 and 3) was higher in birds vaccinated by aerosol as compared to chickens vaccinated by subcutaneous inoculation.

A comparison of various routes of Newcastle Disease vaccination at one day of age.

Groups of 100 one-day-old chicks with moderate levels of maternal antibody were vaccinated with the B1 strain of Newcastle disease virus subcutaneously, intratracheally, intraocularly or by aerosol or were left unvaccinated. Certain of these groups were revaccinated at 9 or 9 and 28 days or at 14 or 14 and 28 days with the LaSota strain of Newcastle disease virus. Vaccination by all routes at one day of age resulted in an antibody response and increased resistance to challenge. The most effective route was by aerosol followed by the intraocular method. Intratracheal administration or subcutaneous inoculation led to a marginal response. Aerosol administration at 9 or 9 and 28 days or at 14 or 14 and 28 days gave adequate antibody responses and resistance to challenge.

Vaccination of chickens against Marek's disease with the turkey herpesvirus vaccine using a pneumatic vaccinator.

A pneumatic vaccinator has been successfully used to administer cell-associated turkey herpesvirus (HVT) vaccine without a loss in titer due to the pressure required to administer the vaccine. Laboratory studies have also shown that chickens vaccinated with graded doses of the HVT vaccine using doses as low as 41 PFU offered protection against Marek's disease (MD) when compared to the unvaccinated controls. The pneumatic vaccinator has also been successful in administering a combination of HVT vaccine and tissue culture fowl pox vaccine. Vaccinated birds were protected against challenge with virulent MD virus as well as fowl pox virus. Antibiotics such as spectinomycin pentahydrate or lincomycin hydrochloride monohydrate and spectinomycin sulfate tetrahydrate were used in combination with the HVT and fowl pox vaccine and none of the antibiotics appear to have an adverse effect on the efficacy of either vaccine.

Simultaneous vaccination of one-day-old broiler chickens with tenosynovitis virus and turkey herpesvirus.

An attenuated tenosynovitis virus vaccine and turkey herpesvirus (HVT) vaccine mixed prior to vaccination were injected subcutaneously into one-day-old chicks. In laboratory and field trials there did not appear to be any interference, because chickens vaccinated with both vaccines were effectively immunized against challenge with virulent Marek's disease virus or tenosynovitis virus when compared with unvaccinated chickens or chickens vaccinated with either HVT or tenosynovitis virus. The combined tenosynovitis and HVT vaccine had essentially the same virus titers when compared to the titers of each vaccine prior to mixing. Also, the HVT viremia levels and the serum neutralization titers of chickens vaccinated with both vaccines were essentially the same as those in chickens vaccinated with a single vaccine. In field trials, chickens vaccinated with the combined vaccines had fewer condemnations for parts and septicemia-toxemia and total condemnations when compared to chickens not vaccinated with tenosynovitis virus. There was less mortality in the majority of the flocks vaccinated with tenosynovitis virus vaccine and HVT when compared to flocks receiving only HVT vaccine.

Vaccination of chickens with a clone-selected Lastoa strain of Newcastle disease virus.

A cone-selected Lasota strain of Newcastle disease (ND) was found to be more immunogenic than the B1 strain but less immunogenic than the regular Lasota strain while having the same pathogenic index as the B1 strain. The geometric mean hemagglutination-inhibition (HI) titers induced in chickens vaccinated with the cloned Lasota strain were higher than those induced in chickens vaccinated with the B1 strain but were found to be slightly less than the titers obtained in chickens vaccinated with the regular Lasota strain. The clone-selected Lasota strain had essentially the same spreading potential as the regular Lasota strain, as indicated by geometric mean titers and challenge mortality of nonvaccinated chickens which were placed in contact with the vaccinated chickens. Oral, ocular, or aerosol vaccination of maternally immune chickens with the clone-selected Lasota strain gave essentially the same protection as those vaccinated with the regular Lasota strain.

Field trials with an oil emulsion Newcastle disease vaccine in broiler breeders.

Chickens vaccinated with live Newcastle disease (ND) vaccine and subsequently revaccinated with an inactivated oil emulsion vaccine had high and persistent hemagglutination-inhibition (HI) antibody titers for at least 40 weeks. The geometric mean HI antibody titers of flocks vaccinated with the inactivated ND vaccine ranged from 48.8 to 91.9, whereas the titers of flocks vaccinated every 90 days with a live ND vaccine ranged from 8.6 to 43.5. Breeder flocks revaccinated with a liver LaSota ND vaccine had lower egg production than the flocks vaccinated with the inactivated vaccine. The average egg production per hen for the 40 week laying cycle was 177.8 and 174.8 eggs per hen for hens vaccinated with the inactivated vaccine, whereas those hens vaccinated with the live virus vaccine averaged 163.0 and 155.6 eggs per hen. The increase in egg production would more than offset the additional cost of the oil emulsion NDV vaccine as well as the cost of injecting each individual bird at point of lay. Maternal antibody titers in one-day-old chicks were related to the titers in the dams. Maternal antibody titers in chicks originating from breeder flocks vaccinated with the oil emulsion vaccine were higher than the maternal antibody titers of chickens from breeders vaccinated with the live NDV vaccine.

Efficacy of intratracheal administration of Newcastle disease vaccine in day-old chicks.

Groups of day-old chicks with varying levels of parental antibody were vaccinated against Newcastle disease (B1 strain) with a commercially available device which simultaneously debeaks the chick and emits a fine spray of vaccine into its trachea. Some groups were also vaccinated (B1 or Lasota strain) with a commercially available vaccine sprayer at 9 days, 14 days, or 9 and 25 days of age. Response to vaccine was evaluated once each week during the experimental period of approximately 8 weeks HI titers were determined and 10 chicks were challenged with the Texas GB strain of Newcastle disease virus. In chicks with low to moderate levels of maternal antibody a satisfactory antibody response was attained by vaccination at 1 day of age, and in most cases resistance to challenge was evident by 3 weeks of age. Intratracheal vaccination of chicks with extremely high levels of maternal antibody had a minimal antibody response. All groups of chicks spray vaccinated at 9, 14, or 9 and 25 days of age showed a marked increase in antibody titer regardless of whether they had been vaccinated at 1 day of age.