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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.
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
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Ferreira PG Costa-e-Silva A Monteiro E Oliveira MJ Aguas AP 《Research in veterinary science》2004,76(1):83-94
Young rabbits are naturally resistant to rabbit haemorrhagic disease (RHD) caused by the same calicivirus that kills, within 3 days, nearly all adult animals. We have investigated changes in blood leukocytes, and in the morphology and biochemistry of the liver (the organ where caliciviruses replicate) of young rabbits undergoing benign infection by the RHD virus. Four-week-old rabbits were infected with a calicivirus inoculum having a titre of 2(12) haemagglutination units either sacrificed 18, 24, 48 and 72 h later, or kept for follow-up studies up to 21 days after inoculation. The infection caused an acute and transient decrease in blood heterophils, and sustained enhancement in hepatic transaminases. Inflammatory infiltrates of the liver were seen in all animals after 24 h of infection; they had a predominant midlobular location. Hepatocytes could present different degrees of cell damage, including cell death; these lesions were limited to the liver cells located around the inflammatory infiltrates. Liver transaminases peaked 24-48 h after calicivirus infection; this was the same timing when liver infiltration and hepatocyte damage were more evident. No alterations of other parameters of liver biochemistry were observed. We conclude that calicivirus infection of young rabbits causes a subclinical disorder characterised by an acute and transient decrease in circulating heterophils, and focal liver damage that is expressed by intralobular infiltration by heterophils, initially, and, later on, by mononuclear cells. Our finding of persistence of increased values of liver transaminases suggests chronicity of the infection in young rabbits. We propose that, although resistant to RHD, young rabbits infected by calicivirus may be long-term carriers of the infectious agent and, thus, become a major source of transmission of the virus. 相似文献
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L Caron E F Flores R Weiblen C F C Scherer L F Irigoyen P M Roehe A Odeon J H Sur 《Veterinary microbiology》2002,84(4):285-295
Latent infection with bovine herpesvirus type-5 (BHV-5) was established in rabbits inoculated with two South American isolates (EVI-88 and 613) by intranasal or conjunctival routes. Nine rabbits (613, 8/27; EVI-88, 1/34) developed neurological disease and died during acute infection and other three (613, n=2; EVI-88, n=1) developed a delayed neurological disease, at days 34, 41 and 56 post-inoculation (p.i.). Between days 56 and 62 p.i., the remaining rabbits were submitted to five daily administrations of dexamethasone (Dx) to reactivate the infection. Twenty-five out of 44 rabbits (56.8%) shed virus in nasal or ocular secretions after Dx treatment. Virus shedding was first detected at day two post-Dx and lasted from one to 11 days. The highest frequencies of virus reactivation were observed in rabbits inoculated conjunctivally (10/15 versus 15/29); and among rabbits infected with isolate 613 (12/16 versus 13/28). Virus reactivation upon Dx treatment was accompanied by neurological disease in nine rabbits (20.4%), resulting in six deaths (13.6%). Virus in moderate titers and mild to moderate non-suppurative inflammatory changes in the brain characterized the neurological infection. Three other rabbits showed severe neurological signs followed by death after 31 to 54 days of Dx treatment. Virus, viral nucleic acids and inflammatory changes were detected in their brains. The late-onset neurological disease, after acute infection or Dx treatment, was probably a consequence of spontaneous virus reactivation. These results demonstrate that BHV-5 does establish a latent infection in rabbits and that clinical recrudescence may occur upon reactivation. 相似文献
7.
K Cerník 《Veterinární medicína》1983,28(2):81-88
The vaccination strain of infectious bursal disease virus, multiplied in cultures of chick embryo cells, was very resistant to heat. At a temperature of 56 degrees C the infection titre of the virus (TCID50) decreased by 0.9 log10 within two hours and by 1.2 log10 within five hours, but the virus remained infective still after 24 hours. At a temperature of 37 degrees C, a slight decrease in infection titre was recorded only after two days and a decrease by 1.2 log10 was recorded within ten days. After the 21st day the virus was almost inactivated. At a temperature of about 20 degrees C the infection titre of the virus decreased linearly from the third to the twelfth weeks. The control samples kept at +4 degrees C retained their infectivity for three months and at -20 degrees C even for six months. The discussion deals with the effect of the concentration of protein and magnesium chloride in the medium on the thermostability of infectious bursal disease virus. 相似文献
8.
Experimental bovine pneumonic pasteurellosis. I. Prevention of the disease. 总被引：2，自引：2，他引：0 
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下载免费PDF全文 Fifteen three- to six-month old Hereford-cross calves were divided into three groups. The first group was inoculated with bovid herpersvirus 1 (Strain 108), the second with a commercial intranasal vaccine against bovid herpesvirus 1 and the third group acted as controls. At least three weeks after vaccination, all calves were weaned, placed in an environmental chamber at 25.0 degrees C (days) and -13.3 degrees C (nights) and challenged with an aerosol of bovid herpesvirus 1 followed four days later by an aerosol of Pasteurella haemolytica. All surviving calves were sacrificed four days after the second aerosol. None of the calves inoculated with bovid herpesvirus 1 virus or the commercial vaccine developed a generalized pneumonia, although there were one or two nodules (4--8 mm diameter) in two of the calves given the commercial vaccine. Four of the five control calves had extensive lobar pneumonia at necropsy, two of the five died from the disease. Details of the clinical, pathological, bacteriological, virological and some of the serological findings are reported. 相似文献
9.
The biology of Besnoitia besnoiti, the cause of bovine besnoitiosis, is poorly understood. Its definitive host is unknown, and information on potential intermediate hosts is scarce. In order to investigate potential definitive and intermediate hosts for European isolates of B. besnoiti, domestic dogs, cats, rabbits, guinea pigs (Cavia porcellus), gerbils (Meriones unguiculatus), common voles (Microtus arvalis) and NMRI-mice were inoculated with B. besnoiti isolated from naturally infected German cattle. Dogs and cats were fed 5×10(6)B. besnoiti tachyzoites (isolate Bb-GER1), or tissue cysts containing at least 2×10(7)B. besnoiti bradyzoites obtained from the skin of a naturally infected Limousin cow from the same herd where strain Bb-GER1 was isolated. Rodents and rabbits were subcutaneously inoculated with either 5×10(5) Bb-GER1 tachyzoites or 5×10(5) bradyzoites. Groups of 2-4 non-inoculated animals of each species were monitored as negative controls. Feces from all dogs and cats were daily examined by a sedimentation-flotation technique for at least 11 weeks after inoculation but no B. besnoiti oocysts were identified. Cats fed tachyzoites and dogs did not seroconvert, but specific antibodies to B. besnoiti tachyzoites were detected by IFAT (titer≥100) in 2 out of 3 cats fed tissue cysts since 5-7 weeks post infection. By immunoblot, these two cats exhibited a reaction pattern against tachyzoite antigens similar to that observed in naturally infected cattle. Antibodies against B. besnoiti tachyzoites were detected in all inoculated rodent species and rabbits by both, IFAT and immunoblot since 3 weeks post-inoculation. Rabbits and rodents, subcutaneously inoculated with same doses of inactivated bradyzoites remained serologically negative (IFAT titer<50). Clinical signs observed in the inoculated rabbits included fever, serous conjunctivitis and transient swelling of the testes. No clinical abnormalities were noticed in the other tested animal species. Voles developed pneumonia as observed by histological examination. B. besnoiti-DNA was detected by PCR in blood from rabbits, gerbils and voles at 9 days post-infection, and in skin, heart, lung, striated muscle and kidney tissues from voles at 19-21 weeks post-infection. Domestic dogs and cats could not be shown to be definitive hosts of B. besnoiti, but cats seroconverted after feeding on B. besnoiti tissue cysts indicating that B. besnoiti stages had invaded the cats' tissues. The molecular and serological results from this study indicate that European B. besnoiti isolates may infect cats, rabbits, guinea pigs, gerbils, mice and voles; however a persistence of the parasite could be demonstrated only in voles. 相似文献
10.
Clinical signs of transmissible gastroenteritis were not observed in newborn pigs orally inoculated with the high-passaged vaccinal transmissible gastroenteritis virus (TO-163 strain). Vaccinal viral multiplication in digestive tract of newborn pigs fed colostrum before inoculation and kept at 21 to 22 C was diminished, but was not diminished in those fed colostrum and kept at 10 to 11 C. Other groups of newborn pigs inoculated with the attenuated vaccinal virus and kept at 18 to 22 C or at 31 to 34 C were challenge exposed with virulent intestinal virus on the 1st, 2nd, . . ., or 6th postinoculation (PI) days. In the groups kept at 18 to 22 C, 2 of 7 inoculated pigs challenge exposed with virulent virus on the 3rd PI day, 4 of 7 pigs exposed on the 4th PI day, and all of the pigs exposed on and after the 5th PI day survived the exposure. In the groups kept at 18 to 22 C, the attenuated vaccinal virus was distributed mainly in the respiratory organs and lymphatic tissues. On the contrary, in the groups kept at 31 to 34 C, all of the pigs died in 2 to 5 days after challenge exposure, and the attenuated vaccinal virus was scarcely detected in any of the pigs. 相似文献
11.
J Guerrero B P Campbell Seibert K M Newcomb B F Michael J W McCall 《American journal of veterinary research》1983,44(12):2405-2406
A formulation of flubendazole was studied to determine the activity against developing stages of Dirofilaria immitis in artificially infected pups. Flubendazole suspension was administered subcutaneously at a dose rate of 50 mg/kg of body weight once a day for 1, 3, or 5 consecutive days at various times during the experimental period. The pups were necropsied 6 months after the experimental infection, and the heart and pulmonary arteries were examined for adult worms. Optimal activity was obtained when flubendazole suspension was administered subcutaneously for 5 consecutive days, either 1 or 2 months after infection. The formation of encapsulated deposits, containing white viscous fluid, was observed at the injection sites of all treated pups. 相似文献
12.
W A Webster 《Canadian journal of veterinary research》1987,51(3):367-369
A cell culture infection test was developed for the isolation of rabies virus from field cases submitted for rabies diagnosis. The procedure involved the addition of a suspension of suspect brain tissue to a suspension of murine neuroblastoma cells in 96-well microtiter plates. The cultures were then incubated at 35-36 degrees C for four days at which time they were fixed, stained with a fluorescein-labelled hamster antirabies antibody conjugate and examined with a fluorescence microscope. Rabies antigen in cells was readily visible as brilliant, apple-green fluorescent particles. This technique was compared with the standard mouse inoculation test and was at least as sensitive to infection with small amounts of virus, required a much shorter test period and was substantially more economical than the mouse inoculation test. The new cell culture test is now in use at this laboratory, replacing the mouse inoculation test. 相似文献
13.
Experimental transmission and electron microscopic demonstration of the virus of haemorrhagic disease of rabbits in Czechoslovakia 总被引：3，自引：0，他引：3
B Smíd L Valícek J St?pánek E Jurák L Rodák 《Zentralblatt für Veterin?rmedizin. Reihe B. Journal of veterinary medicine. Series B》1989,36(3):237-240
Intramuscular administration of the filtrate of organ suspensions, prepared from a dead rabbit, killed 62.9% of inoculated rabbits within 1 to 5 days, while 93.3% died after intranasal administration of the same inoculum. The virus survived freeze-drying and was resistant to treatment with 0.4% formaldehyde when incubated at 37 degrees C for 1 hour and 4 degrees C for the subsequent 12 hours, but lost its infectivity when the treatment was prolonged to 3 hours at 37 degrees C and 3 days at room temperature. Its infectivity was also inhibited by reconvalescent serum. The virus could not be detected after 3 passages in primary rabbit kidney cell cultures. Electron microscopy of negatively stained preparations demonstrated icosahedral virus particles with a diameter of 29 to 33 nm without an envelope. Accurate morphological classification has not yet been completed. Incubation with a reconvalescent serum, diluted 1:20 or 1:40, resulted in the formation of immune complexes, detectable by electron microscopy. 相似文献
14.
Twenty calves, heifers of the Holstein-Friesian breed and crossbreds with the Slovak Pied breed, were divided into two groups at the average age of 19 days. The trial group was kept outdoors in wooden hutches and the control group was housed in an insulated building. Blood was sampled at the age of 20, 33, 48 and 60 days at the outdoor temperatures of 3 degrees C, -2 degrees C, -5 degrees C and -8 degrees C. The calves kept in hutches where temperatures were always lower than in the insulated calf-house had the higher level of nonesterified fatty acids in all observations. The largest, highly significant difference was determined at the age of 60 days at the outdoor temperature of -8 degrees C (271 mumol/l vs. 224 mumol/l), and the significance of differences was also observed in the first and third blood samplings at the temperatures of 3 degrees C and -5 degrees C. The differences were highly significant in the first group between the first and fourth, and second and fourth samplings. In the calves kept in the insulated building the difference was significant between the first and fourth observation because the content of free fatty acids was also gradually increasing in this case (Tab. I). Glycaemia values were also higher in the calves kept in hutches (Tab. II). The most noticeable (significant) difference was determined at the age of 48 days at the outdoor temperature of -5 degrees C (4.3 mmol/l vs. 3.9 mmol/l). Significant differences within the group were recorded only in calves from the trial group kept in hutches. Insulin concentrations increased gradually with the older age of animals (Tab. II). At the age of 20 days the values were identical in fact in both groups and the highest concentrations were recorded at the age of 60 days. The differences between the groups were not significant, the largest difference was observed at the end of milk feeding period at the age of 60 days (19 microUI/l in calves from hutches and 15.6 microUI/l in calves from the insulated building). Triiodothyronine concentrations decreased from the starting values of 0.8 nmol/l and 0.76 nmol/l in both groups at the age of 33 days to the values of 0.61 and 0.62 nmol/l.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献
15.
H Ishizaki Y Kariya 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》1999,61(5):487-492
An examination of the effects of artificial stress induced by adrenocorticotropin (ACTH) on total and differential leukocyte counts, plasma cortisol levels, metabolic profiles and peripheral blood polymorphonuclear leukocyte (PMN) function was performed on Japanese Black steers kept in a cold environment, with the following regimes; 1) -5 degrees C x ACTH (100 IU/day for 3 days), 2) 0 degrees C x ACTH, 3) 15 degrees C x ACTH and 4) 15 degrees C x PBS. Blood samples were collected before and at 1, 2, 24, 48, 72 and 96 hr prior to the application of the stressor. The plasma cortisol level was found to greatly increase at one hr after the first treatment of ACTH, particularly so in animals exposed to -5 degrees C. Total leukocytes (-5 degrees C and 0 degrees C experiments, respectively), the monocytes (-5 degrees C), neutrophils and eosinophils (-5 degrees C, 0 degrees C and 15 degrees C, respectively) obviously increased just after the first administration, although lymphocyte counts at -5 degrees C were inversely related to those described above. All of these tendencies were augmented by the cold environment except for eosinophils. The chemiluminescent (CL) response of PMN decreased in the ACTH-administered steers at an early stage of post-administration, however, it tended to recover from the lower-than-base value in the cold-affected steers. ACTH administration resulted in higher plasma glucose (Glu) compared to a control, although only steers housed at -5 degrees C evidently showed lower plasma inorganic phosphorus (IP). No abnormal serum acute phase protein, or immunosuppressor, was noted. ACTH thus appears not only to promote physiological reactions but also to temporarily suppress PMN cellular immune function in Japanese Black steers. Although, a cold environment rapidly restored the CL activity to over the pre-administrational value, suggesting that a vital response was activated by crymo-stimuli. 相似文献
16.
Using in vitro excystation as a measure of viability, it was found that at 4 degrees C Sarcocystis gigantea sporocysts survived considerably better in tap water (85% excystation after 174 days) than in either 2.5% potassium dichromate (15% excystation after 174 days) or 2% sulphuric acid (0% excystation after 5 days). Although they were able to resist 48 h suspension at room temperature in most laboratory reagents and disinfectants tested, six (sulphuric acid, ammonia, methanol, ethanol, potassium hydroxide, sodium hydroxide, Medol) had substantial sporocysticidal properties. Further investigation with three of these showed that sporocyst excystation was reduced from 65% to less than 10% following contact with 2.5% sulphuric acid for 1 h or with 2% ammonia or 4% Medol for 4 h. Sporocysts were either killed or had their ability to excyst severely impaired by heating to 60 degrees C and 55 degrees C for 5 and 60 min, respectively, by exposure to ultraviolet radiation at a dose of 4000 ET, or by prolonged storage in water at 24 degrees C. Sporocysts exposed to either constant or intermittent freezing at -18 degrees C suffered a comparatively slow decline in excystation rate with time, as did those subjected to desiccation. The duration of survival of desiccated sporocysts was inversely related to relative humidity and after 245 days at 33% relative humidity and temperatures of 15 degrees C or 24 degrees C, 60% of such sporocysts excysted. 相似文献
17.
Evaluation of the persistent efficacy of doramectin and ivermectin injectable against Ostertagia ostertagi and Cooperia oncophora in cattle 总被引：2，自引：0，他引：2
Vercruysse J Dorny P Claerebout E Demeulenaere D Smets K Agneessens J 《Veterinary parasitology》2000,89(1-2):63-69
The persistent efficacy of doramectin and ivermectin injectable against moderate and high infection levels of Ostertagia ostertagi and Cooperia oncophora were evaluated in cattle. Calves were allocated to six groups of six animals. On Day 0 animals of Groups I1/I2 and D1/D2 were treated with 0.2mg/kg ivermectin and doramectin injectable, respectively. Animals of the C1, I1 and D1 groups received a daily (moderate) infection of 1000 L3 of O. ostertagi and 1000 L3 of C. oncophora, and animals of the C2, I2 and D2 groups received a daily (high) infection of 10,000 L3 of each species. The animals were infected for 21 days with both species, the infections with C. oncophora and O. ostertagi started from Days 8 and 15 post treatment, respectively. Animals were necropsied on Day 40. The calculation of the persistent activity of ivermectin and doramectin was based on the efficacy against the different developmental and adult stages of both parasites. The present study confirmed that infection levels may influence the duration of persistent efficacy of an anthelmintic. Doramectin had at the moderate infection level a persistent efficacy of at least 35 days against O. ostertagi and at least 28 days against C. oncophora; at the high infection dose persistent efficacy was somewhat shorter i.e. up to 33 days and approximately 28 days, respectively. The duration of persistent efficacy of ivermectin against O. ostertagi at the moderate infection level was between 14 and 25 days, at the high dose level up to 25 days. Persistent efficacy of ivermectin against C. oncophora could, at both infection doses, not be measured, with the present experimental design. 相似文献
18.
Thomovsky EJ Backus RC Mann FA Richmond CK Wagner-Mann CC 《American journal of veterinary research》2008,69(5):652-658
OBJECTIVE: To determine whether lipid particle coalescence develops in veterinary parenteral nutrition (PN) admixture preparations that are kept at room temperature (23 degrees C) for > 48 hours and whether that coalescence is prevented by admixture filtration, refrigeration, or agitation. SAMPLE POPULATION: 15 bags of veterinary PN solutions. PROCEDURES: Bags of a PN admixture preparation containing a lipid emulsion were suspended and maintained under different experimental conditions (3 bags/group) for 96 hours while admixtures were dispensed to simulate IV fluid administration (rate, 16 mL/h). Bags were kept static at 4 degrees C (refrigeration); kept at 23 degrees C (room temperature) and continuously agitated; kept at room temperature and agitated for 5 minutes every 4 hours; kept static at room temperature and filtered during delivery; or kept static at room temperature (control conditions). Admixture samples were collected at 0, 24, 48, 72, and 96 hours and examined via transmission electron microscopy to determine lipid particle diameters. At 96 hours, 2 samples were collected at a location distal to the filter from each bag in that group for bacterial culture. RESULTS: Distribution of lipid particle size in the control preparations and experimentally treated preparations did not differ significantly. A visible oil layer developed in continuously agitated preparations by 72 hours. Bacterial cultures of filtered samples yielded no growth. CONCLUSIONS AND CLINICAL RELEVANCE: Data indicated that the veterinary PN admixtures kept static at 23 degrees C are suitable for use for at least 48 hours. Manipulations of PN admixtures appear unnecessary to prolong lipid particle stability, and continuous agitation may hasten lipid breakdown. 相似文献
19.
The aim of the present study was to examine consequences of sudden changes in ambient temperature over a 4-hour period (see part 1 [ELMER & REINHOLD, 2002]) on respiratory health in clinically healthy calves. Therefore, the relationship between short-term changes in ambient temperature and the occurrence of clinical respiratory disease was checked over a period of 3 weeks after exposure in 10 calves exposed to 5 degrees C, in 9 calves exposed to 35 degrees C and in 8 control calves (kept at 18-20 degrees C). Within the period beginning 3 days before exposure and lasting until up to 21 days after exposure, each calf was examined clinically. Rectal temperature and respiratory rate were measured daily. All calves were euthanised on day 21 after exposure. Macroscopically visible pneumonic lesions were evaluated using a semiquantitative system. Tissue samples from tonsils, bronchi, trachea, lung and mediastinal lymph nodes were examined bacteriologically. In contrast to non-exposed control calves, severe respiratory illness was observed in individual calves of both exposed groups (5 degrees C, 35 degrees C). Significant increases in body temperature, respiratory rate and animal losses (2 calves died in the group exposed to 5 degrees C, one calf died in the group exposed to 35 degrees C) were the main clinical findings. At necropsy (3 weeks after exposure), no pneumonic lesions were observed in control calves--despite the fact that this group had the highest microbiological colonisation rates in tonsils and in large airways, i.e. trachea and bronchi, within all groups. However, variable pneumonic lung lesions were seen in remaining calves exposed to cold or warm air (5 degrees C, 35 degrees C). The microbiological examination confirmed that mainly Mycoplasma spp. were identified in the lung tissue of calves exposed to 5 degrees C while Pasteurella multocida and/or Mannheimia haemolytica were the only germs found in the lung tissue of calves exposed to 35 degrees C. The results of parts 1 and 2 of the present study related to health issues of calves should be taken into account for future legislation on animal welfare. 相似文献
20.
Rabbit haemorrhagic disease virus (RHDV) and Pasteurella multocida bacteria cause severe losses among rabbit populations. The efficacy of a recently developed bivalent vaccine against pasteurellosis and RHDV was investigated. Doses exceeding 2 haemagglutinating units (HU) of viral antigen were sufficient to protect rabbits against infection with RHDV. The bivalent vaccine appeared to be safe for use in all age groups of rabbits, including pregnant females, even after treatment with 20 times the normal vaccine dose. Rabbits injected with 8 or 4 HU of bivalent vaccine showed high antibody titres against both organisms for 9 months after inoculation. The antibody levels against RHDV in young rabbits at 30 days of age were elevated when they originated from mothers with high antibody titres. The most suitable period for vaccination of offspring appeared to be around 50 days of age. The bivalent vaccine against pasteurellosis and RHDV combined speed and longevity of the immune response. Immune protection against pasteurellosis and RHDV can thus be achieved with only one manipulation. 相似文献