Further evidence of long distance airborne transmission of Aujeszky's disease (pseudorabies) virus

Christensen, Laurids Siig; Mortensen, Sten; Bøtner, Anette; Strandbygaard, Bertel; Rønsholt, L.; Henriksen, C. A.; Andersen, Jens Bo

doi:10.1136/vr.132.13.317

Cited by 83 publications

(59 citation statements)

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“…Although the range in herd sizes (50-600 sows) was fairly small compared to other studies [18,46], we did find a positive association between herd size and ADV seroprevalence. This is consistent with results obtained by Anderson et al [2], Morrison et al [31] and Christensen et al [9], but it is in contrast with studies conducted by Weigel et al [46]. ADV is introduced more often in large herds because they usually have more frequent contacts outside the herd than small herds.…”

Section: Discussionsupporting

confidence: 92%

Herd factors associated with the seroprevalences of four major respiratory pathogens in slaughter pigs from farrow-to-finish pig herds

et al. 2000

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-The objective of this study was to investigate sero-epidemiological aspects of Mycoplasma hyopneumoniae (Mh), influenza H 1 N 1 and H 3 N 2 viruses and Aujeszky disease virus (ADV) in fattening pigs from 150 randomly selected farrow-to-finish pig herds. Different herd factors were examined as potential risk indicators for the percentage of pigs with antibodies against the 4 pathogens. The median within-herd seroprevalences of the pathogens were: Mh 76%, H 1 N 1 100%, H 3 N 2 40% and ADV 53%. There was a positive association between the seroprevalences of both influenza viruses, and a negative association between the seroprevalences of ADV and H 1 N 1 . The percentage of pigs seropositive for Mh increased with the purchase of gilts and with the season (slaughter date in MarchApril). The within-herd seroprevalences of both influenza viruses were higher in the case of a higher density of pig herds in the municipality. A higher number of fattening pigs per pen additionally increased the risk of being seropositive for H 3 N 2 . The percentage of pigs with anti-gE-antibodies against the wild type ADV increased with higher airspace stocking density in the finishing unit, increasing herd size, increasing number of pig herds in the municipality and slaughter date in March-April. Increased seroprevalences for these 4 respiratory pathogens were mostly associated with pig density in the herd and its vicinity, the winter period, and with the purchase of gilts. Purchase of gilts, number of fattening pigs per pen and airspace stocking density are risk factors that can be managed directly by farmers striving to attain a high respiratory health status of pigs. pig / respiratory infections / seroprevalence / epidemiology Vet. Res. 31 (2000) 313-327 313

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Section: Discussionsupporting

confidence: 92%

Herd factors associated with the seroprevalences of four major respiratory pathogens in slaughter pigs from farrow-to-finish pig herds

et al. 2000

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“…Demonstration of higher frequency of latency in the sacral ganglia instead of the trigeminal ganglia of naturally and experimentally infected feral or hybrid swine is consistent with previous results that indicate that the main route of transmission of PRVs indigenous to feral swine is venereal (Romero et al, , 2001 and not respiratory as is the case of PRV strains in domestic swine (McFerran and Dow, 1964;Christensen et al, 1993). An example of a herpesvirus primarily transmitted venereally is herpes simplex virus 2 (HSV-2), the cause of genital herpes in humans in which latency has been shown to occur mainly in the sacral dorsal root (S2-S4) ganglia (Aurelian, 1989).…”

Section: Discussionsupporting

confidence: 88%

“…Transmission of PRV in domestic swine usually occurs by the oropharyngeal route after direct contact of infected and susceptible animals and the ingestion or aspiration of infected aerosols, secretions, and excretions (McFerran and Dow, 1964;Christensen et al, 1993). Recently, we reported that transmission of PRVs indigenous to feral swine occurs mainly by the genital route during the mating of PRVinfected feral swine to susceptible feral or domestic swine (Romero et al, , 2001.…”

Section: Introductionmentioning

confidence: 99%

Potential Sites of Virus Latency Associated With Indigenous Pseudorabies Viruses in Feral Swine

Romero

Meade

Homer

et al. 2003

Journal of Wildlife Diseases

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Free-ranging feral swine (Sus scrofa) are known to be present in at least 32 states of the USA and are continuously expanding their range. Infection with pseudorabies virus (PRV) occurs in feral swine and the primary route of transmission in free-living conditions seems to be venereal. Between 1995 and 1999, naturally infected feral swine and experimentally infected hybrid progeny of feral and domestic swine, were kept in isolation and evaluated for occurrence of latent PRV indigenous to feral swine in sacral and trigeminal ganglia and tonsil. Sacral ganglia were shown, by polymerase chain reaction (PCR) amplification of the thymidine kinase (TK) gene of PRV, to be the most frequent sites of latency of PRV. Nine (56%) of 16 sacral ganglia, seven (44%) of 16 trigeminal ganglia, and five (39%) of 13 tonsils from naturally infected feral swine were positive for PCR amplification of TK sequences of PRV. These tissues were negative for PRV when viral isolation was attempted in Vero cells. DNA sequencing of cloned TK fragments from the sacral ganglia of two feral swine, showed only one nucleotide difference between the two fragments and extensive sequence homology to fragment sequences from various domestic swine PRV strains from China, Northern Ireland, and the USA. The hybrid feral domestic swine, experimentally inoculated with an indigenous feral swine PRV isolate by either the genital or respiratory route, acquired the infection but showed no clinical signs of pseudorabies. Virus inoculated into either the genital or respiratory tract could, at times, be isolated from both these sites. The most common latency sites were the sacral ganglia, regardless of the route and dose of infection in these experimentally infected hybrids. Nine of 10 sacral ganglia, six of 10 trigeminal ganglia, and three of 10 tonsils were positive for PCR amplification of TK sequences. No virus was isolated from these tissues in Vero cells. The demonstration of the sacral ganglia as the most common sites of latency of pseudorabies viruses indigenous to feral swine, supports the hypothesis that these viruses are primarily transmitted venereally, and not by the respiratory route as is common in domestic swine, in which the trigeminal ganglia are the predominant sites of virus latency.

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“…2 Airborne transmission is a possibility. 8,34 However, the closest genetic relationship between the C2a-D1a (both dogs) and D1b-A1-A2 (swine and sheep) subclusters was between the isolates from farm D1, implicating transmission between the dog and swine on that farm. A similar pattern of canine transmission may have been involved in the spread of ADV from D1 to A1 and A2.…”

Section: Discussionmentioning

confidence: 99%

“…7,8,24,26,38 Restriction fragment length polymorphism (RFLP) among viral isolates has been used to distinguish field and vaccine strains of ADV. 11,12,19,29 To utilize REA for epidemiologic purposes, it was necessary to establish that ADV is relatively stable genetically, both in vivo and in vitro.…”

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confidence: 99%

Application of a Quantitative Algorithm to Restriction Endonuclease Analysis of Aujeszky's Disease (Pseudorabies) Virus from a Geographically Localized Outbreak

et al. 1999

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Abstract. A retrospective epidemiologic study was conducted to evaluate the application of an objective quantitative algorithm for estimating genetic similarity from restriction endonuclease analysis data. The analysis was performed to assist the determination of chronologic trends in an Aujeszky's disease viral epidemic in a geographic region. DNA from each viral isolate obtained during the epidemic was digested with 4 restriction endonucleases and molar ratio labeled to generate separate fragment patterns that were simultaneously compared using the algorithm. The resultant estimates of genetic similarity were then used in conjunction with time of virus isolation and specific geographic location of the outbreaks to identify the probable sources of infection and the patterns of spread among swine herds. This type of quantitative analysis enabled a more precise and objective approach than previously has been applied to the interpretation of restriction endonuclease data, thereby demonstrating the benefit of this methodology for the investigation of infectious disease outbreaks.Restriction endonuclease analysis (REA) has been used as an epidemiologic tool to support hypotheses regarding the source of Aujeszky's disease (AD, pseudorabies) virus (ADV) infection for swine farms and individual animals. 7,8,24,26,38 Restriction fragment length polymorphism (RFLP) among viral isolates has been used to distinguish field and vaccine strains of ADV. 11,12,19,29 To utilize REA for epidemiologic purposes, it was necessary to establish that ADV is relatively stable genetically, both in vivo and in vitro. In previous study, there was enough viral genomic stability in a swine herd to enable the use of REA to categorize isolates into strains. 10 This type of first-order molecular characterization of DNA polymorphism has been based on visual comparisons and/or the use of 1-dimensional computerized dendrograms to produce phylogenetic trees representing the percentage of similarity or diversity.Considerations of an ADV epidemic within a geographic location must include animal sources other than swine, although such nonporcine species usually are dead-end hosts. Domestic livestock (cattle, goats, sheep) 3,5,13,14,25,30,35 and wildlife (wild rats, mice, mink, fox, deer, badger, coyotes, hare, raccoons) 21,28,37 are susceptible to natural ADV infections. Deaths from ADV infections also may occur in cats and dogs residing on or near premises with infected livestock. 4,6,15,16,20,22,23,31 Moreoever, ADV was genetically stable during in vivo passage through nonporcine species. 33 Epidemiologic applications of REA include documenting the occurrence of new ADV strains in an area and classifying isolates from a geographic location into groups to infer viral transmission. In this regard, REA was performed on ADV isolated from moribund lambs. 38 The infected lambs had both fence line contact with swine and exposure to a syringe, which had previously been used to vaccinate swine with a modified live ADV product. The resultant patterns indicate...

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Further evidence of long distance airborne transmission of Aujeszky's disease (pseudorabies) virus

Cited by 83 publications

References 0 publications

Herd factors associated with the seroprevalences of four major respiratory pathogens in slaughter pigs from farrow-to-finish pig herds

Herd factors associated with the seroprevalences of four major respiratory pathogens in slaughter pigs from farrow-to-finish pig herds

Potential Sites of Virus Latency Associated With Indigenous Pseudorabies Viruses in Feral Swine

Application of a Quantitative Algorithm to Restriction Endonuclease Analysis of Aujeszky's Disease (Pseudorabies) Virus from a Geographically Localized Outbreak

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