[Increased immune response in broilers after administration of natural food supplements]. / Zvýsení obranyschopnosti brojleru po podávání biologických krmných doplnku.

The trial involved broilers from the 4th to the 56th day of life. The first group P1 (n = 30) received commercial mashes with supplements of 0.5% biomass of freshwater algae (Chlorella vulgaris). The second group P2 (n = 30) received 0.9% dried cow's colostrum and 0.9% dried brewer's yeasts in addition to the algae (0.2%). All the ingredients came from fluid-bed drying at temperatures maximally 50 degrees C. Control group K (n = 30) consisted of broilers which received commercial mashes only. At the age of 21, 33 and 56 days, 10 birds of each group were killed, and basic hematological values were determined in the blood samples and phagocytic activity of leucocytes was determined. Samples of the thyme, bursa Fabricii, spleen, ileocecal valve, Meckel's diverticulum, gonads, suprarenal glands and Harder's gland were subjected to histological examination. 22-day chickens of all three groups were vaccinated with Newcastle disease (the vaccine Avipest, Mevak Nitra) and the levels of specific antibodies in blood serum were determined on days 33, 46 and 56. 0.5% alga supplement to feed ration increased the live weight of experimental broilers at the end of the second week of life only (p < 0.05). On the 21st and 33rd day of life, phagocytic activity of leucocytes increased significantly (p < 0.01) in these individuals, while in the second month of life development of the intestinal lymphatic tissue and Harder's gland was largely stimulated. Combination of algae with other biological additives did not significantly influence the live weight of broilers, but it enhanced the above-mentioned effect on the phagocytic activity and lymphatic tissue development.(ABSTRACT TRUNCATED AT 250 WORDS)

[Isolation and study of biological properties of non-oncogenic Marek's disease herpesviruses in chickens. 1. Characterization in vitro]. / Izolace a studium biologických vlastností neonkogenních kurecích herpesviru Markovy nemoci. 1. Charakterizace in vitro.

The present paper deals with isolation of nonpathogenic chicken herpesviruses of Marek's disease (MD) and their in vitro characterization. Two strains of herpesviruses (denoted as VUB-M and -K isolates) were isolated from leucocytes separated from the blood of fattening chickens without clinical and pathomorphological symptoms of Marek's disease and from the blood of laying hens of a laboratory nonvaccinated flock without clinical symptoms, but with almost 100% incidence of precipitating MD antibodies. After in vitro adaptation, they were cytopathic for chicken embryonal fibroblasts in three days after infection. Isolates were identified as chicken herpesviruses of Marek's disease on the basis of the origin and nature of cytopathic effect in CEF (Biggs and Milne, 1972), lack of infectivity of culture medium and loss of infectivity of cells after their destruction through repeated cycles of freezing and thawing (Biggs and Payne, 1967), then serologically by agar gel immunodiffusion against specific serum (Chubb and Churchill, 1968) and electronoptically.

[Isolation and study of biological properties of non-oncogenic Marek's disease herpesviruses in chickens. 2. Characterization in vivo]. / Izolace a studium biologických vlastností neonkogenních kurecích herpesviru Markovy nemoci. 2. Charakterizace in vivo.

In a previous paper (Jurajda and Halouzka, 1992) the in vitro isolation of two chicken herpesviruses of Marek's disease (M and K strains) was described and results of their characterization were presented. The present paper deals with the in vivo characterization of both isolates: pathogenicity and immunosuppressive characteristics of isolates were observed in a five-week test period, along with the development and production dynamics of antibodies and viral antigen in the feathers of experimentally infected chickens of the Brown Leghorn breed. A technique of double immunodiffusion in agar gel according to Ouchterlony, modified by Woernl (1966), was used to determine the presence of antibodies to Marek's disease virus (MDV) in blood serum and of precipitating MDV-antigen in feather quills of tested chickens. Isolate multiplication and titration were performed in a system of chicken embryonal fibroblasts (CEF) (Jurajda et al., 1984). Chickens were infected i.m. with three virus doses - 10(2) to 10(4) PFU per chicken while the dose 10(4) corresponded to the titre of 10,800 PFU/0.2 ml for M isolate and to the titre of 8,600 PFU/0.2 ml for K isolate. The nature and rate of regressive changes in lymphatic organs were determined according to criteria described by Halouzka and Jurajda (1991). The results are summarized in Tabs. I and II. Neither of the isolates evoked clinical or pathomorphological macroscopic symptoms of the disease. M isolate induced microscopic MD-specific changes in the peripheral nerves (of C type) and only moderate and transient signs of immunosuppression in 11% of infected chickens.(ABSTRACT TRUNCATED AT 250 WORDS)

[Pathologic changes in the organs in chickens after infection with the turkey herpesvirus THV-BIO-I]. / Patologické zmeny orgánu kurat po infekci krutím herpetickým virem THV-BIO-I.

The objective of our work was to investigate the dynamics of pathological lesions of chicken organs after infection with high doses of turkey herpesvirus THV-BIO-I. This virus strain is commonly used in form of the Marvak vaccine against Marek's disease of poultry in Czechoslovakia. High doses of the vaccine are used in practice with respect to the epizootological situation. The incidence of pathological lesions in the organs of Brown Leghorn chickens was investigated in a five-week experiment. One-day chickens were infected intramuscularly with the HVT strain at the doses of approximately 10(2), 10(3) and 10(4) PFU in 0.2 ml of infective inoculum per chick. The body weights of ten chickens of each group were recorded at intervals of 1, 2, 3 and 5 weeks after infection, serological examination was performed for precipitating antibodies to MDV and the feather was examined for MDV-antigen. Bursae Fabricii and spleens were weighed. Thymus, bursae Fabricii, spleens, peripheral nerves (n. ischiadicus and pl. brachialis) and gonads were sampled for histopathological examination. Neither maternal nor post-infection antibodies were found in any chick. Cytolytic lesion severity of lymphoid organs was scored using the scale of immunosuppression degrees (0-4). Morphological criteria were published in a previous paper (Halouzka and Jurajda, 1991b). The differences observed in the weights of bursa Fabricii and spleen between the infected and control chickens were not statistically significant. The observed lymphoid infiltrations in the skin, gonads, nerves and other tissues following the HVT infection are well-known and correlate with the infection dose.(ABSTRACT TRUNCATED AT 250 WORDS)

[Use of filter paper for blood specimen collection in poultry for use in the detection of antibodies to Newcastle disease virus]. / Pouzití filtraccního papíru k odberu krve u drubeze a k následnému vysetrení prítomnosti protilátek proti viru Newcastleské nemoci.

Trials were conducted to verify the possibility of poultry blood sampling with filter papers for subsequent examination of the eluates for the presence (and level) of haemagglutination-inhibition antibodies against the Newcastle disease virus (NDV). Qualitative examination was performed in 294 paired samples of sera and eluates, representing 10 selective sets, coming from three vaccinated poultry flocks. The numbers of positive sera (dilution ratios 1:20 and higher) and positive eluates of filter papers (dilution ratios of 1: 2 and higher) were compared and it was found that there were 238 positive paired samples (81%) and 30 were negative (10.2%), hence, there were like reactions in 268 paired samples (91.2% of the total number of samples examined). It was only in 25 paired samples that positivity was recorded just in the sera: 22 times with a titre of 1:20 and three times with a titre of 1:40. In one case, positivity was recorded just in the eluate. The final titres were compared in 181 paired samples of sera and eluates, all diluted at a ratio of 1:2, and it was found that the concentration of the haemagglutination-inhibition antibodies in the eluates corresponded to serum dilution ratio of 1:20. Under this assumption, the antibodies were found to have the same titre in 164 paired samples (55.8%) during the quantitative evaluation. A lower titre was recorded in 82 eluate samples (27.9%) and a higher antibody titre in 48 eluate samples (16.3%) (in comparison with the antibody titres in the respective sera). The over-all average geometrical titre (GMT) of antibodies was 1:65 in the eluates and 1:75 in the sera.(ABSTRACT TRUNCATED AT 250 WORDS)

[The occurrence of Marek's disease in genetically different groups of chickens]. / Výskyt Markovy nemoci u geneticky odlisných skupin kurat.

The occurrence of Marek's disease was studied under laboratory conditions in four genetically different groups of chickens (Brown Leghorn, F1 hybrids of the CB x IA inbred lines, pullets of the paternal branch of the grandparent stock of the Hybro meat type, and final hybrids of the White Hisex layer type) after infection with the Georgia strain of Marek's disease (MD) virus, used in two doses (1600 and 16,000 PFU per one bird). MD was diagnosed on the basis of the occurrence of macroscopic tumours; when these tumours were absent in birds which had died within 105 days from infection, the dead bodies were subjected to microscopic examination (peripheral nerves, gonads, skin, bursa of Fabricius, thymus, spleen). The size of the parenterally administered dose of the virus had no significant effect on mortality, occurrence of tumours and the MD virus in any of the groups of chickens tested. However, there was a time shift in the mortality curve in chickens infected with a lower dose. The significantly highest occurrence of MD was recorded in BrL chickens (100%). A somewhat lower occurrence of MD was recorded in the Hisex White chickens (87.8%) and in the CB x IA hybrids (73.8%). However, the dead CB x IA chickens had a higher occurrence of tumours (96.6%) than the Hisex White chickens (77.1%). The lowest MD occurrence was recorded in the pullets of the Hybro meat type (25.5%). The organ most frequently affected by tumours after infection of the birds with the Georgia strain was the liver (24.1%).

[The effect of short-term isolation of vaccinated chicks on the incidence of Marek's disease]. / Vliv krátkodobé izolace vakcinovaných kurat na výskyt Markovy choroby.

In chickens immunized by normal and tenfold doses of MARVAK vaccine (100 and 1,000 PFU) we investigated protective effects against the natural contact infection of chickens that were exposed to the infection immediately after vaccination, or at the intervals of 48 and 72 hours, and 7 and 14 days. Studying the elimination of Marek's disease virus by feather follicles, the health condition of chickens, tumor frequency and mortality rate we demonstrated that neither of these doses could protect the chickens from the disease if they were exposed to contact infection just after vaccination. An expressive protective effect was observed in chickens isolated for 7-14 days and there was not recorded any difference in the protection against the disease after the doses of 100 and 1,000 PFU. The main and feasible measure against MD is to prevent an early infection of newborn chickens by improving the zoohygienic conditions.

[Dynamics of passive humoral immunity transfer against Marek's disease in the progeny of the grandparent breeding stock of broilers]. / Dynamika prenosu pasivní humorální imunity proti Markove nemoci na potomstvo prarodicovského chovu masného typu.

In the progeny of the grandparents of broiler type HYBRO, imported by the Dutch firm EURIBRID, neonatal humoral immunity was studied during the whole laying period, i.e. in laying hens at the age of 26-52 weeks. Precipitation test was used to examine 292 samples of sera from the parent chickens of sire stock AB and 299 samples of sera from the chickens of dam stock CD, for the presence of maternal antibodies to Marek's disease virus. The number of positive samples decreased with the growing age of the grandparent generation. In the sire stock it ranged from 41.7 to 82.6% (average number 57.5%); in the dam stock, it was from 50 to 90.9% (average number 71.6%). The average incidence of precipitation antibodies in the dam stock was significantly higher than in the sire stock (p less than 0.05). The relationship between laying hen age and percent incidence of passive antibodies in parent-generation chickens was characterized by a regression line and correlation coefficient. We discuss the problem that the incidence of heterologous passive antibodies in the produced parent-generation chickens can only minimally influence the onset of post-vaccination immunity after application of the Czechoslovak vaccine MARVAK, i.e. passive immunity in these chickens cannot be caused by insufficient prophylaxis in some of Czechoslovak multiplier flocks of broiler type.

[Postvaccination viremia in breeding flocks of layers and broilers after vaccination against Marek's disease of fowl]. / Postvakcinacní virémie v rozmnozovacích chovech nosných a masných po vakcinaci proti Markove nemoci drubeze.

The immunity state after vaccination against Marek's disease (MD) was studied in three multiplier flocks of laying fowl (MFL), five multiplier flocks of broiler fowl (MFB), and one commercial layer flock (CLF). The occurrence and average titres of post-vaccination viraemia in the selected sets of chickens from these flocks, examined at the age of three or twenty weeks, were used as the immunity criterion. The development of post-vaccination viraemia, following the administration of the MARVAK vaccine at the doses of 100 and 1000 PFU per bird in the HX-SL and Shaver layer hybrids, was examined under laboratory conditions at the same time. In the group of birds examined in the third week of age and coming from the MFL vaccinated with the recommended MARVAK vaccine (dose (100 PFU per bird), 64.3% of the chicks were viraemic, the average viraemia titre being 12 PFU/10(7) leucocytes. After the administration of a four-fold vaccine dose, 57.1% of the chicks were viraemic, the average titre being 3.2 PFU/10(7) leucocytes. After the administration of a ten-fold dose of MARVAK vaccine, 80% of the chicks were viraemic and the average titre of viraemia was 8 PFU/10(7) leucocytes. In the MFB vaccinated with the recommended dose of the MARVAK vaccine, the percentage of viraemic chickens was 48.3% and the average titre of viraemia was 6.5 PFU/10(7) leucocytes. In the pullets examined at the age of 20 weeks the number of viraemic birds ranged from 20 to 50% and the average viraemia titres were from 3.8 to 13.1 PFU/10(7) leucocytes. In the flock affected by acute MD, no post-vaccination viraemia was found in the clinically diseases pullets. In the chickens of the HX-SL line vaccinated with the recommended MARVAK vaccine dose, viraemia culminated in the third week after vaccination (31.5 PFU/10(7) leucocytes), and after the use of the dose ten times as high as the recommended one the culmination came a week later (47 PFU/10(7) leucocytes). In the Shaver chicks vaccinated with the recommended dose or with the ten-fold dose of the MARVAK vaccine, the post-vaccination viraemia culminated in the fourth week after vaccination (94.9 and 116.8 PFU/10(7) leucocytes). The post-vaccination precipitation antibodies were first detected in the eighth week after vaccination.

[Protecting chickens against Marek's disease under laboratory conditions by the administration of Marvak, a Czechoslovak produced vaccine and vaccine imported from East Germany]. / Chránenost kurat proti Markove nemoci v laboratorních podmínkách po aplikaci cs. vakcíny MARVAK a vakcíny dovázené z NDR.

Laboratory trials were conducted to compare the efficiency of two vaccines against Marek's disease (MD) on the basis of the dynamics of post-vaccination viraemia and by means of a challenge test. Two groups of the HX-SL hybrid layers, each containing 40 birds, were vaccinated with the MARVAK cellular vaccine manufactured in Czechoslovakia (100 PFU per chick) or with the Insel Riems vaccine manufactured in the GDR (1000 PFU per chick). In weekly intervals, half the birds of each group were tested for post-vaccination viraemia and the other half, including 20 non-vaccinated birds, were infected by contact with the pathogenic virus of MD from the second day of age. The viraemia in the birds vaccinated with MARVAK culminated in the third week of age when it reached the average value of 25 PFU/10(7) leucocytes; later on, by the eighth week of age, it decreased to 0.62 PFU/10(7) leucocytes. The maximum number of viraemic chicks was found in the third and fourth week of age (80%); on an average it ranged from 60%. The average viraemia in the chickens treated with the vaccine from the GDR ranged from 1.6 to 3.6 PFU/10(7) leucocytes in the second to eighth week of age. A 100% positivity of the tested birds was found in the sixth week of age; it ranged around 70% on an average. In all the challenged groups of birds the precipitation antigen of Marek's disease was detected in feather follicles already 14 weeks from contact infection.(ABSTRACT TRUNCATED AT 250 WORDS)

Resistance to Marek's disease is controlled by a gene within the B-F region of the chicken major histocompatibility complex in Rous sarcoma regressor or progressor inbred lines of chickens.

Rous sarcoma "regressor" chicken lines CB and CB.R1 identical in the B-F region of the B complex (MHC) are susceptible to Marek's disease. On the contrary, the Rous sarcoma "progressor" line CC different in the B-F region from the CB and CB.R1 lines and identical in the B-G region with the CB.R1 line is considerably resistant to MD. The inbred chicken line M is susceptible to MD, although it carries the B21 allele which is generally considered to determine MD resistance. Analysis by means of sera specific for B-F and B-G antigens revealed that the B haplotype of the M line is composed of the B-G region coding for the typical B-G21 antigen and of a different B-F region coding for B-Fx antigen of thus far unknown specificity. Thus genetic resistance to MD is controlled by a gene located within the B-F region of the chicken MHC.

[Serological study of a breed of broilers with edema disease]. / Sérologické vysetrení brojleru postizených edémovou chorobou.

Twenty selected groups of chickens (835 birds on the whole) coming from randomly chosen broiler production cycles were studied for the occurrence of precipitation antibodies to the viruses of Marek's disease, infectious bronchitis, Newcastle disease, infectious bursitis, reovirus, Tipton virus and CELO. The occurrence of these antibodies was subjected to statistical evaluation and to comparison with the occurrence rate of oedema disease in the tested broiler production cycles (296 166 birds on the whole). Neither correlations nor synergistic effect was observed between the studied virus infections and the occurrence of oedema disease. Serological research demonstrated a high rate of the occurrence of reovirus. (positive proportion: 26% of samples and 100% of groups), infectious bursitis virus (56.8% and 75%) and Tipton virus (74.5% and 100%) in broilers.

[The effect of the infective inoculum on the development of pathological changes in the skin of chickens with Marek's disease]. / Vliv infekcního inokula na rozvoj patologichých zmén v küzi kurat pri Markove chorobe.

Three groups of straight-run chickens were infected. The first group was infected with the homogenate of the skin of conditionally edible broilers, the second group was infected aerogenically by dust from halls with permanently high occurrence of Marek's disease, and the third with feather homogenate from experimental chickens with positive Marek's disease tests. All the chickens were killed in weekly intervals up to the age of eight weeks. The dynamics of the development of pathological changes was studied in the skin, ischiadic nerves, central lymphatic organs, and spleen in order to see whether different inocula or changes in central lymphatic organs would influence the occurrence of cutaneous and visceral lesions. The results indicate that the kind of infective inoculum does not influence the rise of cutaneous changes and that the central lymphatic organs have no substantial effect on the occurrence of the cutaneous form of Marek's disease; they are involved more significantly in the rise of changes in visceral organs. An exceptional finding was a neoplasm under the skin of the neck, histologically consisting of neoplastically proliferating lymphoid, reticular, fibrocytic and myxoid elements. The study also indicates that changes in the skin, nerves and in some cases also in bursa Fabricii are important for diagnostic practice particularly in dubious cases of Marek's disease.

[Experimental induction of the cutaneous form of Marek's disease in broilers]. / Experimentální indukce kozní formy Markovy choroby brojlerú.

Straight-run chickens of the Ross broiler hybrid were experimentally infected with the skin homogenates of sound broilers, broilers conditionally edible, and broilers confiscated for alternations in skin. The chickens infected with the homogenates of healthy skin were negative in the Marek's disease test. In 17% of the chickens infected with the skin from the conditionally edible broilers, macroscopically observable cutaneous lesions were induced and 60% of the infected chickens had microscopic changes in the skin; visceral organs were always affected by the infection. In the chickens infected with the skin of a confiscated bird, the long storage exerted its unfavourable effect and the infected birds were negative in the Marek's disease test. Our results indicate that the active form of Marek's disease was induced.

[Possibilities of Marek's disease transmission by dust in contaminated hatcheries]. / Moznost prenosu Markovy nemoci na kurata prachem v kontaminovaných líhních.

A short-term test in vivo was performed with dust collected in hatcheries on a contaminated farm. The results proved the presence of infective agents of Marek's disease (MN) in the dust. The chickens hatched in these hatcheries and taken to disease (MN) in the dust. The chickens hatched in these hatcheries and taken to a disease-free environment also showed microscopic MN-specific changes. In the set of 50 chickens of the Leghorn White (LW) breed, line 44, infected aerogenically with the dust from hatcheries, MN-specific changes were found in 26 birds, i. e. in 52.0%. The non-infected control birds were MN-negative. In the set of 182 White Cornish X White Plymouth (WC X WP) hybrid chickens, hatched in contaminated hatcheries, MN-specific changes were observed in 41 birds, i. e. in 22.5% of the chickens tested.

Disinfection of Marek's disease virus in poultry dust.

Dust samples from farms contaminated with Marek's disease virus (MDV) were exposed to various disinfectants under experimental and field conditions. After the disinfection treatment, examination was made for the presence and oncogenicity of surviving MDV by the inoculation of tissue cultures and susceptible chickens. A combination of formaldehyde vapour and a preparation based on iodine bound to organic carriers appeared to be the most effective for disinfection.

[Marek's disease--characterization of the VUB-70 strain in vivo]. / Markova nemoc--charakterizace kmene VUB-70 in vivo

In the course of serial passaging of the strain of Marek's disease (MD) (VUB-70) in White Leghorns the author investigated the morbidity, mortality, development of the MD-specific changes, and the effect of sex on these indices, for the purpose of characterization of the biological properties of an isolated strain of MD in vivo. The incubation period lasted from 41 to 46 days p. inf. on the first day of life. Pullets showed greater sensitiveness towards infection not only through higher morbidity and mortality, but also due to a larger number of tumorous changes. In MD-positive animals the same proportion of macroscopic and microscopic changes was found. The average occurrence of Marek's disease amounted to 74.4 p. c. On the basis of the biological properties in vivo the VUB-70 strain was characterized as a medium pathogenic strain of the acute form of Marek's disease.