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1.
The survival of the street rabies virus in a 10% suspension, prepared from the salivary gland of a naturally infected fox, was studied under various conditions. A bioassay and titration on mice were used for the identification of the virus in different intervals. The heat inactivation of the virus in a suspension kept in a test tube at the temperatures of 20 degrees C and 37 degrees C was performed in two stages. The rapid reduction of the titre within 24 hours was followed by a slower decrease, reaching total inactivation after 96 hours at both temperatures. When the virus was tested by means of the contamination of various substrates (glass, metal sheet, plant leaf) with 0.1 ml of infection suspension in a thin layer, the longest survival of the virus was recorded at the temperature of 5 degrees C--144 hours. At the temperature of 20 to 21 degrees C the virus kept its activity on the glass and plant leaf for 24 hours and on the metal sheet for 48 hours although the applied drops looked like having dried. The temperature of 30 degrees C combined with intensive sunshine devitalized the virus within 1.5 hours, whereas without sunshine the virus still remained active, at the temperature of 30 degrees C, after 20 hours. 相似文献
2.
Specific-pathogen-free chickens orally inoculated at 4 days of age with a moderately pathogenic vaccine strain of infectious bursal disease virus (IBDV) and/or at 5 days of age with Cryptosporidium baileyi oocysts remained free of overt clinical signs throughout a 16-day period postinoculation (PI). The prepatency period for C. baileyi oocyst shedding was shorter in chickens receiving higher numbers of oocysts, but once shedding was detected, there were no obvious differences in shedding patterns among groups receiving 10(3) through 10(6) oocysts. On days 8 and 16 PI, cryptosporidia were located primarily in the bursae of Fabricius. IBDV exposure was associated with bursal follicle atrophy, whereas C. baileyi infection resulted in bursal epithelial hypertrophy and hyperplasia, mild follicle atrophy, and heterophil infiltration of the bursal mucosa. Examination of experimental groups of 30 birds each indicated that concurrent infection with both agents resulted in more severe bursal lesions, more infected birds, and greater numbers of cryptosporidia in infected tissues. At the termination of the trial, 16 days PI, Cryptosporidium infection was associated with a 6% decrease in mean body weight compared with controls. 相似文献
3.
Three similar flocks of broiler breeder parent chickens that had been given live infections bronchitis (IB) vaccines during rearing were injected at 20 weeks of age with three different oil emulsion vaccines: a commercial monovalent Newcastle disease (ND) vaccine (flock A); an experimental bivalent vaccine containing ND and infectious bursal disease (IBD) components (flock B); and an experimental trivalent vaccine containing ND, IBD and IB components (flock C). One week after vaccination 40 hens from flock A and 40 from flock C were taken to the laboratory and their egg yields individually recorded. At 37 weeks of age they were challenged by aerosol exposure to virulent IB virus. The egg production dropped significantly in the hens from flock A but not in the hens from flock C. On the farm, flock C showed a higher mean IB virus antibody titre four weeks after vaccination but titres rose in all three flocks indicating the presence of active IB virus infection. No differences in egg yields were found between the three farm flocks. 相似文献
4.
It has been demonstrated that after experimental infection of pig slurry from the space under the slatted floor (infection dose of 10(6)PFU per ml), the Aujeszky's disease virus (ADV) survived for 72 hours at the temperature of 15 degrees C and at pH 6.5, but was inactivated after 96 hours. When technologically treated pig slurry from the storage tanks was saturated with water and infected with ADV at the dose of 10(5)PFU per ml, the virus survived for 23 days when kept at 15 degrees C and 4 degrees C and at pH 6.8, but was inactivated under the same conditions after 30 days. When the infective ADV dose in the technologically treated pig slurry in the storage tanks was reduced to 10(4)PFU per ml, the virus survived 16 days at +4 degrees C and pH 7.0 and 8.0 but was inactivated within 23 days after infection. 相似文献
5.
6.
Sánchez A Contreras A Jiménez J Luengo C Corrales JC Fernández C 《Veterinary microbiology》2003,94(1):71-77
With the aim of evaluating the effect of freezing goat milk samples on recovery of intramammary pathogens, 1200 milk samples from udder halves with subclinical intramammary infection were studied. Samples (20 ml) were frozen at -20 and at -80 degrees C. Thawing was carried out at room temperature at 7, 14, 21, 28, 58, 118, 178, 236 and 730 days after collection and bacteriological analyses were carried out to determine the number of colony forming units/ml (CFU/ml). Mixed model statistical analysis showed that bacterial group, temperature of storage, interaction of bacterial group and temperature of storage and the interaction of bacterial group, time and temperature of storage were statistically significant effects. For coagulase negative staphylococci (CNS), least squares means of log CFU/ml recovered at -20 and -80 degrees C were not different. Nevertheless, for Gram negative bacilli (GNB) a significant decrease was detected in samples frozen at -20 vs. -80 degrees C. At both temperatures and at different times of storage, significant increases were detected between log CFU/ml of CNS and values on day zero. At -20 degrees C, a significant decrease in GNB recovery was detected between freezing days zero and 730. This difference was not detected when goat milk samples infected by GNB were frozen at -80 degrees C. The results show that frozen milk samples can be useful in goat subclinical mastitis control programs. 相似文献
7.
Infectious Bursal Agent Vaccination of Chicks from Infectious Bursal Agent-vaccinated Dams 
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下载免费PDF全文 Chicks from infectious bursal agent-vaccinated broiler breeders were vaccinated with a commercial infectious bursal agent vaccine at intervals after hatching. Bursas from some of these chicks were examined for infectious bursal agent-specific fluorescence four days after vaccination and bursas from others were examined for histological lesions of infectious bursal disease 21 days after vaccination. Serological studies were conducted to determine if active immunity to infectious bursal agent followed vaccination.Chicks failed to develop immunity if their levels of maternally-derived serum neutralizing antibody were in excess of approximately log(2) 7 at the time of vaccination. When antibody titres fell below this level, vaccination usually resulted in infectious bursal agent virus replication in the bursa and consequential bursal damage but was followed by development of active immunity. 相似文献
8.
Experiments were undertaken to study the pathogenesis of VRI-33, a strain of fowl adenovirus serotype 8 isolated from the liver of a broiler chicken with inclusion body hepatitis. A 30% death rate resulted from oral infection of one-day-old specific pathogen free chickens with 106 plaque forming units of VRI-33. Chickens 10, 14, 21 and 28 days of age did not die following infection via natural routes but there were some motalities following infection via parenteral routes. Immunodepression by neonatal cyclophosphamide treatment, followed by infection with VRI-33 via non-parenteral routes, caused varying degrees of hepatitis with basophilic intranuclear inclusion bodies in hepatocytes. The mortality rate of cyclophosphamide-treated, VRI-33 infected chickens, was not significantly altered by post-infection temperature stress. Infection with infectious bursal disease virus, followed by infection with VRI-33 via natural routes at 14 days of age, was not associated with mortalities. 相似文献
9.
Survival of viruses in fermented edible waste material 总被引：1，自引：0，他引：1
R E Wooley J P Gilbert W K Whitehead E B Shotts C N Dobbins 《American journal of veterinary research》1981,42(1):87-90
The survival of selected viruses in fermented edible waste material was studied to determine the feasibility of using this material as a livestock feed ingredient. Seven viruses, including pseudorabies, Newcastle disease, infectious canine hepatitis, avian infectious bronchitis, measles, vesicular stomatitis, and a porcine picornavirus were inoculated into a mixture of ground food waste (collected from a school lung program) containing Lactobacillus acidophilus. Mixtures were incubated at 5 C, 10 C, 20 C, and 30 C for 96 hours. Temperature, pH, and redox potential were monitored. Samples for virus isolation were obtained daily. Newcastle disease virus and infectious canine hepatitis virus survived the entire test period. The porcine picornavirus was inactivated at 30 C after 74 hours, but survived for the entire test period at the other temperatures. Pseudorabies virus was inactivated at 20 C and 30 C within 24 hours, but survived for 48 hours at 10 C and 96 hours at 5 C. Avian infectious bronchitis virus was inactivated at 20 C and 30 C within 24 hours, but survived 72 hours at 5 C and 10 C. Measles and vesicular stomatitis viruses were rapidly inactivated at all 4 temperatures. 相似文献
10.
Chicken anemia virus (CAV) can cause a disease syndrome characterized by severe anemia, bone marrow atrophy, and severe immunosuppression in young chicks. Maternal antibodies prevent these clinical signs but do not prevent infection, transmission of the virus, or immunosuppression. The clinical disease is rare today because of the widespread practice of vaccinating breeders, but the subclinical form of the disease is ubiquitous. The dynamics of CAV infection, CAV antibody responses, relative lymphoid organ weights, and associated lesions were studied in two broiler flocks from a commercial producer. Both groups had detectable CAV antibodies at hatch, which waned over the first 3 wk of life. Both groups had detectable CAV DNA in both thymi and bursae over the same period. At 35 days of age, virus was detectable by polymerase chain reaction in 16 of 20 chickens, and 7 of 20 had detectable antibodies. By 42 days of age, virus was detectable in 18 of 20 chickens, and 18 of 20 had antibodies to CAV. We observed a decrease in relative thymic weights beginning at 35 days of age, coincidental withthe detection of CAV in the thymus. Bursal sizes began to decrease at 28 days of age, coincidental with a rise in antibody titers to infectious bursal disease virus. In this study, we demonstrated that under typical field conditions CAV infections in broilers have unique dynamics unlike those reported in egg laying strains of chickens managed under specific-pathogen-free conditions. 相似文献
11.
The level of maternal antibody to infectious bursal disease (IBD) virus in the circulation of one-day-old layer strain chickens was found to be on average, 45% of the antibody titre in their respective dam, while the minimum ELISA titre which protected against a challenge of 1000 CID50 of virus was 400. Maternal antibody was found to disappear from the circulation of these crossbred chickens with a half-life of 6.7 days. From these data it is possible to estimate the ELISA titre necessary in vaccinated hens to provide the desired duration of passive protection; protection being assessed by an ELISA which measures IBD viral antigen in the bursa of Fabricius following challenge. 相似文献
12.
Velhner M Mitevski D Potkonjak D Stojanović D Kovačević M Petrović T Aleksić-Kovačević S 《Acta veterinaria Hungarica》2010,58(4):499-509
The biological properties of an infectious bursal disease (IBD) virus isolated from bursas collected during an outbreak in a village chicken flock in Macedonia are described. The mortality rate was 50%. Two viruses coexisted in the bursas of infected chickens (IBDVwt and IBDVtc). The virus termed IBDVtc grows on chicken embryo fibroblast (CEF) cells from the first passage. Specific pathogen free chickens inoculated with IBDVtc at passage level 4 did not develop any clinical signs of disease. Some discrete bleeding on the leg muscles was seen and the bursa of Fabricius revealed pathological lesions similar to those caused by classical strains. However, the bursa recovered quickly (bursa lesion score 2) by 14 days post infection (PI). We also found evidence of bursal repopulation by means of perinuclear antigen staining. Strong CD3 influx was evident at 4 days PI, and at 33 days PI the CD3+ cell finding was comparable to the control. The mean antibody titre was 9.2 log 2 at 14 days PI. The amino acid composition of VP2 in IBDVwt (222 Ala, 242 Ile, 253 Gln, 256 Ile, 279 Asp, 284 Ala, 294 Ile and 299 Ser) is described. The same sequence was found in IBDVtc, except for two point mutations, at Gln253→His and Ala284→Thr. Such amino acid substitution is responsible for partial attenuation and the ability of the strain to replicate in cell culture. None of the commercial vaccine viruses has a similar arrangement of amino acids in the variable domain of IBDV. This strongly suggests that IBDVtc originates from a very virulent strain. To the best of our knowledge, this is the first report of a concomitant infection of chickens with highly pathogenic IBDV and its mutant counterpart. 相似文献
13.
Rabbit haemorrhagic disease: an investigation of some properties of the virus and evaluation of an inactivated vaccine. 总被引：1，自引：0，他引：1
An inactivated vaccine against rabbit haemorrhagic disease (RHD), developed and tested in our laboratory, is produced commercially by Bioveta, Ivanovice, Czechoslovakia. Rabbits developed full protection against infection 3 weeks after the administration of a single dose. Antibodies were detectable from day 5 after vaccination. Naturally acquired antibodies were demonstrated in some rabbits kept on commercial farms. The virus survived at least 225 days in an organ suspension kept at 4 degrees C, at least 105 days in the dried state on cloth at room temperature (around 20 degrees C), and at least 2 days at 60 degrees C, both in organ suspension and in the dry state. Experimental infection of rabbits younger than 2 months was successful in some animals. Hares, guinea pigs, white mice, golden and Chinese hamsters, chinchillas and hysterectomy-derived, colostrum-deprived piglets were resistant to infection. 相似文献
14.
Experimental Aujeszky's disease in pigs: excretion, survival and transmission of the virus 总被引：5，自引：0，他引：5
Airborne Aujeszky's disease virus was recovered from looseboxes containing groups of pigs infected with virus strains from England, Northern Ireland and Denmark from days 1 to 7 after infection. Pigs sampled individually excreted most airborne virus on days 2 and 3 after infection. On a 24 hour basis the maximum amount of airborne virus excreted per pig was log10 5.3 TCID50. Subclinical infection was transmitted from a clinically affected group of pigs to a seronegative group held in separate looseboxes when air was drawn through ducting connecting one box with the other. Tissues taken from pigs killed at varying times after infection showed that the main sites of virus replication were in the head and neck region. Aujeszky's disease virus was detected for up to 40 days in a range of tissues taken from pigs at the acute stage of disease and stored at -20 degrees C. 相似文献
15.
In an effort to develop alternate disinfectants for rotaviruses, pilot studies were conducted to determine if bacterial proteases could render simian-11 (SA-11) rotavirus non-infectious. SA-11 was found to be fairly temperature resistant, retaining a low-level of infectivity following 65 degrees C treatment for 2h at pH 8.5. It also resisted pH 8.5-5 at 45 degrees C for 2h. Alcalase, an alkaline protease, was the most effective of the various proteases (alcalase, durazym, neutrase, and savinase) tested. To analyze specific parameters for alcalase, SA-11 virus (10(5.5) median tissue culture infective dose/ml original titer) was treated at pH 6, 25 and 15 degrees C (simulated field conditions), with 0.1 and 1.0% alcalase. At pH 6.0 and 15 degrees C, 0.1% alcalase reduced SA-11 titer by 0. 75 log in 24h, and by 1.25 log in 120h. At 25 degrees C and pH 6.0, 0.1% alcalase reduced the titer by 2.25 log after 24h, and by 2.75 log in 120h. At pH 6.0 and 15 degrees C, 1% alcalase reduced SA-11 titer by 1.50 log in 24h and by 1.75 log in 120h. At the same enzyme concentration and pH, but at 25 degrees C the titer was reduced by 2. 75 log in the first 24h and by 3.25 log at 120h. These results show that the alkaline protease alcalase is capable of inactivating SA-11 virus to a certain degree depending on conditions. Further definition of operating parameters, demonstration of inactivation under field conditions and analysis whether the demonstrated degree of inactivation would decrease calf morbidity and mortality remain to be explored at this time. 相似文献
16.
A B?tner 《Veterinary microbiology》1991,29(3-4):225-235
Survival of Aujeszky's disease virus in pig slurry was investigated during anaerobic storage at 5, 20, 35, 40, 45, 50 and 55 degrees C using 100-ml laboratory models simulating the conditions in slurry tanks during winter and summer seasons and during anaerobic digestion in batch reactors. The inactivation rate was found to increase with increasing temperature. Virus was inactivated at 5 and 20 degrees C in 15 weeks and 2 weeks, respectively. At 35 degrees C (mesophilic conditions) the virus was inactivated in 5 hours and at 55 degrees C (thermophilic conditions) no virus could be detected after 10 minutes. 相似文献
17.
J J Zimmerman W J Berry G W Beran D P Murphy 《American journal of veterinary research》1989,50(9):1471-1474
In laboratory experiments, pseudorabies virus was readily recovered from within the body of houseflies (Musca domestica L) that had ingested the virus. Age of the fly and ambient temperature affected the rate of virus inactivation within the houseflies. Virus half-life in 3-day-old flies was 6.36 hours vs 2.81 hours in flies 8 or 13 days old. Half-life in 5-day-old flies was 12.92 hours at 10 C, 5.95 hours at 20 C, and 2.69 hours at 30 C. Virus half-life in dead flies was 9.06 hours at 10 C, 4.28 hours at 20 C, and 1.71 hours at 30 C. The data did not provide any evidence of virus replication in either living or dead flies. 相似文献
18.
Five commercial broiler flocks, not vaccinated for infectious bursal disease virus, derived from infectious bursal disease virus-vaccinated breeder flocks were surveyed for evidence of bursal damage and infectious bursal disease virus infection. They were compared with two groups of birds raised in isolation. Serum samples from one day old chicks contained maternal anti-infectious bursal disease virus antibodies which declined to undetectable levels by four weeks of age. Serum antibody levels remained undetectable in both control groups and one commercial flock, whereas four of the five commercial flocks had actively produced anti-infectious bursal disease virus antibodies by slaughter age. The weight of bursae from infectious bursal disease virus-positive flocks declined as compared to controls after four weeks of age. The decline in weight correlated with the appearance of histopathological lesions. Infectious bursal disease virus antigen was demonstrated in selected infected bursae and infectious bursal disease bursae and infectious bursal disease virus was isolated from some of these damaged bursae. Clinical infectious bursal disease was not observed in any of the commercial flocks. The importance of subclinical bursal damage and immunosuppression is discussed. 相似文献
19.
In the present study, specific-pathogen-free, 2-week-old Leghorn chickens were experimentally infected with strain 73688 of infectious bursal disease virus (IBDV) in order to evaluate haematological and histological changes that might suggest a pathomechanism for haemorrhages in this disease. At 96 hours post infection (hpi) a significant increase in prothrombin time was detected in the absence of visible lesions in myeloid bone marrow tissue and of significant thrombocytopenia. The aforementioned findings suggest alteration of the secondary coagulation mechanisms and not a direct effect of virus on thrombocytes or its precursors. 相似文献
20.
S S Cloud J K Rosenberger H S Lillehoj 《Veterinary immunology and immunopathology》1992,34(3-4):353-366
To determine the functional impact of alterations in lymphocyte concentrations and ratios following infection with chicken anemia agent (CAA) alone or in combination with infectious bursal disease virus (IBDV) on the immune system of young chickens, in vitro lymphoproliferation assays and in vivo responses to vaccination with several common viral agents were assessed at various time intervals post-inoculation (PI). Concanavalin A (Con A), phytohemagglutinin (PHA) and pokeweed mitogen (PWM) stimulation of splenic lymphocytes (SPL) collected from control birds could not be detected until 10-14 days PI. Infection with CAA was characterized by significantly higher PWM stimulation of SPL at 17 days PI and significantly lower PWM stimulation of peripheral blood lymphocytes (PBL) at 14 days PI, compared with uninfected controls. Concanavalin A and PWM stimulation of SPL was significantly increased in birds inoculated with IBDV alone. Lymphocytes harvested from birds inoculated simultaneously with CAA and IBDV had significantly lower responses. Effects on humoral and cell-mediated immunity following CAA and/or IBDV were determined by evaluating vaccination responses to Newcastle disease virus (NDV), fowl pox virus (FPV) and infectious laryngotracheitis virus (ILTV) during the acute phase of CAA infection (2 weeks PI). Vaccination of birds 2 weeks following CAA infection at 1 day of age resulted in decreased protection against NDV (85.7%) and ILTV (7.1%) challenge compared with protection rates in control birds (100% and 53.3% respectively). Infectious bursal disease virus infection was associated with decreased protection against NDV (60%) only. Concomitant infection at 1 day of age resulted in a greater reduction in NDV challenge protection (33.3%), slightly decreased FPV protection (87.5%), increased numbers of persistent FPV vaccination lesions and increased protection against ILTV challenge (71.4%). Vaccination of birds 2 weeks following CAA infection at 2 weeks of age resulted in slightly decreased NDV humoral antibody, development of persistent FPV vaccination lesions (17%) and increased immunity to ILTV challenge compared with control birds (83.3% vs. 66.7%). Chickens inoculated with IBDV alone displayed a more severe depression in NDV antibody titers and only a slight decrease in ILTV protection. Vaccination following concomitant infection at 2 weeks of age resulted in a higher percentage of FPV persistent vaccination lesions (39%) and greatly enhanced immunity to ILTV challenge (100%). 相似文献