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1.
This study was conducted to delineate potential sites of exit and duration of shedding of porcine reproductive and respiratory syndrome virus (PRRSV). Two experiments of 6 pigs each were conducted. Pigs were farrowed in isolation, weaned at 7 days of age, and housed in individual HEPA filtered isolation chambers. In each experiment, 3 pigs served as controls and 3 were inoculated intranasally with PRRSV (ATCC VR-2402) at 3 weeks of age. In a first experiment, on days 7, 14, 21, 28, 35, and 42 post inoculation (PI), pigs were anesthetized and intubated. The following samples were collected: serum, saliva, conjunctival swabs, urine by cystocentesis, and feces. Upon recovery from anesthesia, the endotracheal tube was removed, rinsed, and the rinse retained. In the second experiment, the sampling schedule was expanded and serum, saliva, and oropharyngeal samples were collected from day 55 to day 124 PI at 14 day intervals. Virus was isolated in porcine alveolar macrophages up to day 14 from urine, day 21 from serum, day 35 from endotracheal tube rinse, day 42 from saliva, and day 84 from oropharyngeal samples. No virus was recovered from conjunctival swabs, fecal samples, or negative control samples. This is the first report of isolation of PRRSV from saliva. Virus-contaminated saliva, especially when considered in the context of social dominance behavior among pigs, may play an important role in PRRSV transmission. These results support previous reports of persistent infection with PRRSV prolonged recovery of virus from tonsils of swine.  相似文献   

2.
The objectives of the study were to determine the site of porcine reproductive and respiratory syndrome virus (PRRSV) in individual houseflies, to assess whether an individual housefly could transmit PRRSV to a susceptible pig, and to compare the ability of PCR, virus isolation and a pig bioassay to detect PRRSV in houseflies. In the first experiment 26 houseflies were fed on a pig infected experimentally with PRRSV; 13 were processed as a whole fly homogenate, while an exterior surface wash and a gut homogenate were collected from the other 13. Infectious PRRSV was recovered from nine of the whole fly homogenates, 12 of the gut homogenates and one of the exterior surface washes. In the second experiment, two of 10 individual houseflies, which had fed on an infected pig, transmitted PRRSV to a susceptible pig in a controlled manual transmission protocol. In the third experiment, single flies or pools of 30 flies were immersed in different concentrations of a PRRSV inoculum, then tested by PCR, virus isolation and bioassay. The virus was detected at a concentration of 10(1) TCID50/ml by PCR, 10(2) TCID50/ml by the bioassay and 10(3) TCID50/ml by virus isolation.  相似文献   

3.
An experimental infection with porcine reproductive and respiratory syndrome virus (PRRSV) was established in 150 five-month-old pigs housed in a fan-ventilated finishing facility, the infected barn. To determine whether air exhausted from the wall fans contained infectious PRRSV, a trailer containing 10 four-week-old PRRSV-naive sentinel pigs was placed 10 m from the building from day 3 after the 150 pigs were infected until day 10. To connect the two airspaces, one end of an opaque plastic tube, 15 m in length and 5 cm in diameter, was fastened to the wall fan of the infected barn, and the other end was placed inside the trailer. Air from the building was exhausted into the trailer 24 hours a day for seven consecutive days and PRRSV infection was monitored in the infected pigs and the sentinel pigs. Air samples were collected from the infected barn and the trailer. PRRSV infection was detected in the infected pigs three and seven days after they were infected, but not in the sentinel pigs. All the air samples were negative for PRRSV by PCR, virus isolation and a pig bioassay.  相似文献   

4.
The current study was performed to determine if porcine reproductive and respiratory syndrome virus (PRRSV) could be transmitted to pigs by feeding muscle tissue obtained from recently infected pigs. Muscle obtained from pigs infected with either a European strain (EU donor pigs) or American strain (US donor pigs) of PRRSV was fed to PRRSV-free receiver pigs. The donor pigs were slaughtered 11 days post-infection (dpi). PRRSV was detected by conventional virus isolation in muscle at 11 dpi from 7 of 12 EU donor pigs and 5 of 12 US donor pigs. In contrast to conventional virus isolation, all muscle samples from infected pigs were positive for viral nucleic acid by PCR, except for muscle from one animal infected with the American strain of PRRSV. Five hundred grams of raw semimembranosus muscle from each of the donor pigs was fed over a 2 days period (250 g per day) to each of two receiver pigs (48 receiver pigs). The receiver pigs were housed separately in five groups. One of the five groups was fed muscle obtained from US donor pigs that was also spiked with the American strain of PRRSV. Sentinel pigs were placed in-contact with the group of receiver pigs fed spiked muscle. All receiver pigs became viraemic by 6 days post-feeding (dpf). There was evidence of horizontal transmission with sentinel pigs, in-contact with receiver pigs, becoming viraemic. The study demonstrates that PRRSV could be infectious through the oral route via the feeding of meat obtained from recently infected pigs.  相似文献   

5.
The objective of this study was to determine whether porcine reproductive and respiratory syndrome virus (PRRSV) could be transmitted to naïve pigs by mosquitoes following feeding on infected pigs. During each of 4 replicates, mosquito-to-pig contact took place on days 5, 6, and 7 after PRRSV infection of the donor pig. A total of 300 mosquitoes [Aedes vexans (Meigen)] were allowed to feed on each viremic donor pig, housed in an isolation room. After 30 to 60 s, feeding was interrupted, and the mosquitoes were manually transferred in small plastic vials and allowed to feed to repletion on a naïve recipient pig housed in another isolation room. Prior to contact with the recipient pig, the mosquitoes were transferred to clean vials. Swabs were collected from the exterior surface of all vials, pooled, and tested for PRRSV. Separate personnel handled the donor pig, the recipient pig, and the vial-transfer procedure. Transmission of PRRSV from the donor to the recipient pig occurred in 2 out of 4 replicates. The PRRSV isolated from the infected recipient pigs was nucleic-acid-sequenced and found to be 100% homologous with the virus used to infect the donor pigs. Homogenates of mosquito tissues collected in all replicates were positive by either polymerase chain reaction or swine bioassay. All control pigs remained PRRSV negative, and PRRSV was not detected on the surface of the vials. This study indicates that mosquitoes (A. vexans) can serve as mechanical vectors of PRRSV.  相似文献   

6.
The aim of this study was to develop a model to evaluate the aerosol transmission of porcine reproductive and respiratory disease virus (PRRSV). PRRSV (MN 30-100 strain, total dose 3 x 10(6) virus particles) was aerosolised and transported up to 150 m and a portable air sampler was used to collect air samples at 1, 30, 60, 90, 120 and 150 m (five replicates at each distance) and the air samples were tested by TaqMan PCR and virus isolation. The infectivity of the aerosolised PRRSV was tested by exposing six PRRSV-naive pigs for three hours to aerosolised virus that had been transported 150 m. PRRSV RNA was detected in all five replicate air samples collected at 1, 30, 60 and 90 m, in four of the five collected at 120 m, and in three of the five collected at 150 m. Infectious PRRSV was detected by virus isolation at 1 and 30 m (all five replicates), 60, 90 and 120 m (three of the five) and 150 m (two of the five). There was a 50 per cent reduction in the log concentration of PRRSV RNA every 33 m. Three of the six pigs exposed to PRRSV-positive aerosols became infected, and PRRSV RNA was detected in air samples and on swab samples collected from the interior of the chambers that housed the infected pigs while they were being exposed.  相似文献   

7.
The purpose of this study was to evaluate the potential for houseflies (Musca domestica) to mechanically transport and transmit porcine reproductive and respiratory syndrome virus (PRRSV) between pig populations under controlled field conditions. The study employed swine housed in commercial livestock facilities and a release-recapture protocol involving marked (ochre-eyed) houseflies. To assess whether transport of PRRSV by insects occurred, ochre-eyed houseflies were released and collected from a facility housing an experimentally PRRSV-inoculated population of pigs (facility A) and collected from a neighboring facility located 120 m to the northwest that housed a naïve pig population (facility B). All samples were tested for PRRSV RNA by polymerase chain reaction (PCR). To assess transmission between the 2 populations, blood samples were collected from naïve pigs in facility B at designated intervals and tested by PCR. A total of 7 replicates were conducted. During 2 of 7 replicates (1 and 5), PCR-positive ochre-eyed houseflies were recovered in facility B and pigs in this facility became infected with PRRSV. Chi-squared analysis indicated that the presence of PRRSV in an insect sample was significantly (P = 0.0004) associated with infection of facility B pigs. Porcine reproductive and respiratory syndrome virus was not recovered from other reported routes of transmission during the study period, including air, fomites, and personnel. In conclusion, while an insufficient number of replicates were conducted to predict the frequency of the event, houseflies may pose some level of risk for the transport and transmission of PRRSV between pig populations under field conditions.  相似文献   

8.
A study was performed to evaluate the presence of porcine reproductive and respiratory syndrome virus (PRRSV) in pig meat collected at slaughterhouses and its potential transmission to pigs via pig meat. A total of 1039 blood samples were collected from pigs upon their arrival at the abattoir. The following day, meat samples (n = 1027) were collected from the carcasses of these same pigs. Samples originated from 2 Canadian slaughterhouses, 1 situated in the province of Quebec and the other situated in the province of Manitoba. Serum samples were tested for antibodies to PRRSV and both serum and meat samples were also tested for PRRSV nucleic acid by polymerase chain reaction (PCR). Seropositivity to PRRSV for all serum samples was 74.3%. Furthermore 45 (4.3%) of the total serum samples and 19 (1.9%) of the 1027 meat samples were positive for PRRSV by PCR. Sequence analysis of open reading frame (ORF) 5 performed on 15 of the 19 PRRSV strains identified in pig meat indicated that 9 were field strains and 6 were vaccine-like (98% to 99.7% nucleotide homology with the Ingelvac RespPRRS/Repro vaccine). One of these 6 strains presented an intermediate 2-6-2 restriction fragment length polymorphism (RFLP) cut pattern and the others showed the characteristic 2-5-2 RFLP pattern of the vaccine strain. All strains sequenced were determined to be North American strains. In only 1 of the 19 PRRSV-positive meat samples could PRRSV be isolated. To test the potential infectivity of meat samples containing residual PRRSV, 11 of the PCR-positive meat samples (weighing 1.05 to 1.8 kg) were each used in feeding experiments of 2 PRRSV antibody-negative specific pathogen-free pigs of 9 wk of age. Samples were cut into several pieces and fed to each pair of pigs on 2 consecutive days. Each pig pair was housed in a separate cubicle and serum samples were collected at -7, 0, 7, 14, and 20 to 21 days post exposure. Seven pig pairs were found to be infected by PRRSV following ingestion of meat samples, including meat samples containing vaccine-like virus, as judged by the demonstration of PRRSV antibodies and/or PRRSV nucleic acid in the serum. In summary, the present study indicated that low residual quantities of PRRSV may be found in a small percentage of pig meat collected at slaugtherhouses. Furthermore, when this meat was fed raw to pigs in the experimental setting designed, pigs could be infected by PRRSV.  相似文献   

9.
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10.
The ability of genetically diverse strains of porcine reproductive and respiratory syndrome virus (PRRSV) to coexist in a 1750-sow farm was assessed through the case study describing a chronically infected farm, and also by an animal experiment involving the use of swine bioassay. The case study employed a program of monitoring sera from suckling, nursery, and finishing pigs for the presence of PRRSV by polymerase chain reaction (PCR) and virus isolation (VI). The swine bioassay tested homogenates, consisting of lymphoid and pulmonary tissues, collected from 60 breeding animals from the same farm. The open reading frame (ORF) 5 portion of selected positive PRRSV detected from sera or tissues were nucleic acid sequenced and their phylogenies compared. The results indicated the presence of 3 genetically diverse groups, designated PRRSV-A, -B, and -C. Sequence heterology ranged from 5.8 to 11% between groups. Sequence homology ranged from 98.7 to 99.8% within groups. Swine bioassay verified the presence of PRRSV-A in 1 of 60 animals, and no evidence of strains B or C were detected. This paper indicates that based on the evaluation of ORF 5, genetically diverse strains of PRRSV appear to coexist, although the frequency and significance of this observation is not understood.  相似文献   

11.
The purpose of this report is to validate a new protocol, the thermo-assisted drying and decontamination (TADD) system, for eliminating porcine reproductive and respiratory syndrome virus (PRRSV) from contaminated transport vehicles. Scale models of weaned pig trailers were used. The principle of TADD is to raise the interior temperature of trailers to 71 degrees C for 30 min to promote drying and degradation of PRRSV. Trailer interiors were artificially contaminated with 5 x 10(5) TCID50 of PRRSV strain MN 30-100, then treated with 1 of 4 treatments: 1) TADD; 2) air only (no supplemental heat); 3) overnight (8 h) drying; and 4) washing only. Following treatment, swabs were collected from the trailer interiors at 0, 10, 20, and 30 min post-treatment and from the overnight group after 8 h. Swabs were tested for PRRSV-RNA by polymerase chain reaction (PCR). As a measure of the presence of infectious PRRSV, sentinel pigs were housed in treated trailers for 2 h post-treatment and supernatants from swabs were injected IM into naive pigs (bioassay), the recipient pigs were then tested for PRRSV infection. All trailers were PRRSV positive by PCR immediately after washing, prior to treatment (pt). At 10 min pt, 7/10 swabs were positive from the TADD trailers; however, all swabs collected at 20 and 30 min pt were PRRSV negative by PCR, and trailer interiors were visibly dry. In contrast, 9/19, 6/10, and 6/10 swabs collected at 10, 20, and 30 min, respectively, from trailers treated with air only were positive and visibly wet. All swabs (10/10) collected from trailers treated with washing only were PRRSV positive by PCR and all swabs collected at 8 h of drying were PRRSV negative by PCR. All tests for the presence of infectious PRRSV were negative for trailers treated with TADD and overnight drying, while infectious PRRSV was detected in sentinel pigs and bioassay pigs in the other groups. Under the conditions of this study, the efficacy of the TADD system was equal to that of the overnight drying treatment, and it required a shorter period of time to complete its objective.  相似文献   

12.
OBJECTIVE: To determine whether flies can acquire porcine reproductive and respiratory syndrome virus (PRRSV) and disperse the virus throughout a designated area. ANIMALS: 60 four-month-old pigs. PROCEDURE: On day 0, 28 of 60 pigs were inoculated with PRRSV MN 30-100 (index variant). On the same day, 100,000 pupae of ochre-eyed houseflies and 100,000 pupae of red-eyed (wild-type) houseflies were placed in the swine facility for a release-recapture study. Flies were recaptured at 2 locations within the swine facility, 6 locations immediately outside the facility, and 30 locations 0.4, 0.8, 1.3, 1.7, 1.9, and 2.3 km from the facility. Traps were emptied on days 2, 7, 8, 10, and 14. Samples derived from flies were tested by use of a polymerase chain reaction assay, virus DNA was sequenced, and viruses were tested for infectivity by means of a swine bioassay. RESULTS: PRRSV RNA homologous to the index PRRSV was detected in trapped flies collected inside and immediately outside the facility and from 9 of 48 samples collected at 0.4 km, 8 of 24 samples collected at 0.8 km, 5 of 24 samples collected at 1.3 km, and 3 of 84 samples collected at > 1.7 km from the facility. Two samples collected at 0.8 km contained genetically diverse variants of PRRSV. Swine bioassays revealed the virus in flies was infectious. CONCLUSIONS AND CLINICAL RELEVANCE: Flies appeared to become contaminated with PRRSV from infected pigs and transported the virus > or = 1.7 km. Fly-born transmission may explain how PRRSV is seasonally transported between farms.  相似文献   

13.
OBJECTIVE: To evaluate retention of porcine reproductive and respiratory syndrome virus (PRRSV) in houseflies for various time frames and temperatures. SAMPLE POPULATION: Fifteen 2-week-old pigs, two 10-week-old pigs, and laboratory-cultivated houseflies. PROCEDURE: In an initial experiment, houseflies were exposed to PRRSV; housed at 15 degrees, 20 degrees, 25 degrees, and 30 degrees C; and tested at various time points. In a second experiment to determine dynamics of virus retention, houseflies were exposed to PRRSV and housed under controlled field conditions for 48 hours. Changes in the percentage of PRRSV-positive flies and virus load per fly were assessed over time, and detection of infective virus at 48 hours after exposure was measured. Finally, in a third experiment, virus loads were measured in houseflies allowed to feed on blood, oropharyngeal washings, and nasal washings obtained from experimentally infected pigs. RESULTS: In experiment 1, PRRSV retention in houseflies was proportional to temperature. In the second experiment, the percentage of PRRSV-positive houseflies and virus load per fly decreased over time; however, infective PRRSV was found in houseflies 48 hours after exposure. In experiment 3, PRRSV was detected in houseflies allowed to feed on all 3 porcine body fluids. CONCLUSIONS AND CLINICAL RELEVANCE: For the conditions of this study, houseflies did not support PRRSV replication. Therefore, retention of PRRSV in houseflies appears to be a function of initial virus load after ingestion and environmental temperature. These factors may impact the risk of insect-borne spread of PRRSV among farms.  相似文献   

14.
A series of three experiments, differing primarily in airflow volume, were performed to evaluate the likelihood of airborne transmission of Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) from infected to non-infected pigs. Pigs were housed in two units (unit A and unit B) located 1m apart and connected by pipes. The air pressure and diameter of the pipes, depending on experiments, were strictly controlled to allow desired airflow volumes from unit A to unit B. Either 25 (experiment 1 and experiment 3) or 26 (experiment 2) pigs infected recently with PRRSV, and either 25 (experiment 1 and experiment 3) or 17 (experiment 2) pigs from a PRRSV-free herd, were housed in unit A. Either 50 pigs (experiment 1 and experiment 3) or 43 pigs (experiment 2) from a PRRSV-free herd were housed in unit B. The amount of air transmitted from unit A to unit B, expressed as a percentage of ventilation intake, was approximately 70, 10, and 1% for experiment 1, experiment 2 and experiment 3, respectively. Blood samples were collected from all pigs once per week and analyzed for antibodies against PRRSV. Based on these methods, airborne transmission of PRRSV from infected to non-infected pigs was confirmed in each of the three experiments.  相似文献   

15.
Porcine reproductive and respiratory syndrome virus (PRRSV) is an RNA virus in the order Nidovirales, family Arteriviridae, genus Arterivirus. The virus induces a prolonged viremia, replicates in macrophages, and produces persistent infection. The purpose of this study was to determine if PRRSV could persist for 90 d or more in a large population of breeding-age gilts housed under environmental conditions typical of commercial swine production and to determine if experimentally infected gilts could shed virus to naïve sentinel gilts beyond 90 d postinfection. Using the intranasal route, we inoculated 120 PRRSV-naïve gilts, 4 mo of age, with 5 mL of cell culture fluid containing a total dose of 102.4 TCID50 of a field isolate (MN-30100) of PRRSV. The index gilts were organized into 3 groups (A, B, and C), 40 gilts per group. To assess the dynamics of the experimental infection, a monitor group of 30 index gilts was blood-tested on days 0, 3, 7, 14, 30, 60, 90, 120, 150, and 180 postinfection. PRRSV viremia was detected with the polymerase chain reaction (PCR) on days 3, 7, and 14 and by virus isolation (VI) on days 7 and 14. PRRSV antibodies were detected from day 14 by enzyme-linked immunosorbent assay (ELISA). To assess shedding, 30 PRRSV-naïve sentinel gilts were commingled with the index gilts on day 90 postinfection and tested by PCR, VI, and ELISA every 15 d until 180 d postinfection; all samples were negative. To assess persistence, 40 index and 10 sentinel gilts were slaughtered at 120 (group A), 150 (group B), or 180 (group C) d postinfection. Evidence of PRRSV was not detected by PCR or VI in any tissue samples from the 120 index gilts. These results indicate that persistence and shedding of PRRSV are of short duration in breeding-age gilts.  相似文献   

16.
The objective of this study was to evaluate if spray dried porcine plasma (SDPP) containing porcine circovirus type 2 (PCV2) genome supplemented in feed could transmit PCV2 to pigs challenged with porcine reproductive and respiratory syndrome virus (PRRSV). Twenty-three PRRSV-free pigs, non-viraemic for PCV2, were housed in bio-safety level 3 facilities and assigned to four groups in a 2×2 factorial design consisting of PRRSV challenge and a negative control. The diet contained 0 or 8kg SDPP per 100kg of feed. PRRSV challenge groups were inoculated intranasally with 2mL of a suspension containing 10(6) TCID(50)/mL PRRSV. The SDPP used in the study contained 7.56×10(5) PCV2 genome copies per gram. Dietary treatments were fed from 4days prior to PRRSV inoculation until 28days post-inoculation (PI). All challenged pigs developed PRRSV viraemia by day 3PI and PRRSV antibodies were detected in sera by day 14PI, with no difference between diet treatments. Neither PRRSV viraemia nor seroconversion was observed in non-challenged pigs. PCV2 was not detected in the serum of any pigs throughout the experimental period. SDPP containing the PCV2 genome supplemented in feed did not result in PCV2 transmission to either healthy or PRRSV-infected pigs under these experimental conditions.  相似文献   

17.
The objective of this study was to develop and test a rapid (< 2 h) sanitation protocol designed for porcine reproductive and respiratory syndrome virus (PRRSV) positive commercial transport vehicles involving cold water washing and disinfection via fumigation using scale models of weaned pig trailers. The study consisted of 2 phases. Following experimental contamination of model trailers with PRRSV MN 30-100 (5 x 10(5)TCID50), phase 1 evaluated the presence or absence of PRRSV RNA by polymerase chain reaction (PCR) on swabs collected from the trailer interiors 0, 60, and 90 min after treatment. Phase 2 consisted of evaluating the infectivity of trailers 90 min posttreatment by monitoring changes in the PRRSV-status of naive sentinel pigs housed for 2 h. Treatments included washing only (treatment 1), washing plus formaldehyde fumigation (treatment 2), washing plus fumigation with glutaraldehyde-quaternary ammonium chloride (treatment 3), and washing plus overnight drying (treatment 4). Porcine reproductive and respiratory syndrome virus RNA was detected in all trailers (20 out of 20 replicates) at 60 and 90 min following the application of treatments 1 and 2. These trailers also contained infectious PRRSV, as determined by the infection of naive pigs housed in treated trailers and the testing of organic debris collected from the interior of trailers by swine bioassay. At 90 min posttreatment, all trailers treated with glutaraldehyde-quaternary ammonium chloride were PCR-negative, non-infectious to sentinel pigs, and swine bioassay negative. Similar results were observed in trailers allowed to dry for 8 h. Under the conditions of this study, it appears certain disinfectants may possess different levels of efficacy against PRRSV and PRRSV-positive models may be effectively sanitized in the absence of overnight drying.  相似文献   

18.
Experiments were designed to determine if porcine reproductive and respiratory syndrome virus (PRRSV) or Bordetella bronchiseptica could be transmitted through indirect airborne contact. Three principal pigs were infected with PRRSV, B. bronchiseptica or both. Five days after the principal pigs were challenged, the three principal pigs and one direct-contact pig were placed into one isolation tent together, and three indirect-contact pigs were placed into another isolation tent which received its air supply from the first isolation tent. Airborne transmission of B. bronchiseptica occurred in 5/5 trials where B. bronchiseptica was the only agent used, and in 3/5 trials where the principal pigs were coinfected with both agents. Airborne transmission of PRRSV occurred in 4/5 trials where PRRSV was the only agent used, and in 2/5 trials where the principal pigs were coinfected with both agents. Thus, airborne transmission of both agents over short distances, such as within a barn, is probable.  相似文献   

19.
The purpose of this study was to evaluate the ability of a commercial air-filtration system to reduce aerosol transmission of Porcine reproductive and respiratory syndrome virus (PRRSV). The system consisted of a pre-filter and 2 filters with EU8 and EU13 ratings. In each of 4 trials, 5 PRRSV-infected donor pigs and 1 naive recipient pig (each 25 kg) were housed in opposing chambers connected by a 1.3-m-long duct. The system filtered air entering 1 recipient-pig chamber (filtered facility) from the donor-pig chamber but not a 2nd recipient-pig chamber (nonfiltered facility). The donor pigs had been experimentally infected with PRRSV MN-184, an isolate previously documented to be shed at a high frequency in contagious aerosols. On days 3 to 7 after infection of the donors, the 2 groups were housed in their respective chambers for 6 h and then in separate facilities, where samples were collected for testing by polymerase chain reaction and enzyme-linked immunosorbent assay over 14 d. Aerosol transmission was observed in 6 of the 20 replicates in the nonfiltered facility, whereas all pigs remained PRRSV-negative in the filtered facility; the difference was significant at P < 0.01. Thus, under the conditions of this study, the air-filtration system evaluated appeared to be highly effective at reducing aerosol transmission of PRRSV.  相似文献   

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