1
|
Dorji T, Jayasingha Ellakkala Appuhamilage RMJ, Bird PL, Huang N, O’Connor TW, Patel KK, Strive T, Taggart PL. Optimising the Delivery of RHDV to Rabbits for Biocontrol: An Experimental Evaluation of Two Novel Methods of Virus Delivery. Viruses 2023; 15:1814. [PMID: 37766220 PMCID: PMC10536075 DOI: 10.3390/v15091814] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2023] [Revised: 08/21/2023] [Accepted: 08/24/2023] [Indexed: 09/29/2023] Open
Abstract
Rabbit haemorrhagic disease virus (RHDV) is established as a landscape-scale biocontrol that assists the management of invasive European rabbits and their impacts in both Australia and New Zealand. In addition to this, it is also available to land managers to augment rabbit control efforts at a local scale. However, current methods of deploying RHDV to rabbits that rely on the consumption of virus-treated baits can be problematic as rabbits are reluctant to consume bait when there is abundant, green, protein-rich feed available. We ran a suite of interrupted time-series experiments to compare the duration of infectivity of two conventional (carrot and oat baits) and two novel (meat bait and soil burrow spray) methods of deploying RHDV to rabbits. All methods effectively killed exposed rabbits. Soil burrow spray and carrot baits resulted in infection and mortality out to 5 days post their deployment in the field, and meat baits caused infection out to 10 days post their deployment. In contrast, oat baits continued to infect and kill exposed rabbits out to 20 days post deployment. Molecular assays demonstrated high viral loads in deployed baits beyond the duration for which they were infectious or lethal to rabbits. Based on our results, we suggest that the drying of meat baits may create a barrier to effective transmission of RHDV by adult flies within 10 days. We therefore hypothesise that fly larvae production and development on infected tissues is critical to prolonged viral transmission from meat baits, and similarly from carcasses of RHDV mortalities, via mechanical fly vectors. Our study demonstrates that meat baits and soil spray could provide additional virus deployment options that remove the need for rabbits to consume baits at times when they are reluctant to do so.
Collapse
Affiliation(s)
- Tshewang Dorji
- Biosecurity, Department of Primary Industries and Regions (PIRSA), Urrbrae, SA 5064, Australia; (T.D.); (R.M.J.J.E.A.); (K.K.P.)
- School of Food, Agriculture and Wine, The University of Adelaide, Urrbrae, SA 5064, Australia
| | | | - Peter L. Bird
- Waite Conservation Reserve, University of Adelaide, Urrbrae, SA 5064, Australia;
| | - Nina Huang
- Health & Biosecurity, Commonwealth Scientific and Industrial Research Organisation, Acton, ACT 2601, Australia; (N.H.); (T.S.)
| | - Tiffany W. O’Connor
- Virology Laboratory, Elizabeth Macarthur Agricultural Institute, Department of Primary Industries NSW, Menangle, NSW 2568, Australia
| | - Kandarp K. Patel
- Biosecurity, Department of Primary Industries and Regions (PIRSA), Urrbrae, SA 5064, Australia; (T.D.); (R.M.J.J.E.A.); (K.K.P.)
- School of Animal and Veterinary Sciences, The University of Adelaide, Roseworthy, SA 5371, Australia
| | - Tanja Strive
- Health & Biosecurity, Commonwealth Scientific and Industrial Research Organisation, Acton, ACT 2601, Australia; (N.H.); (T.S.)
| | - Patrick L. Taggart
- School of Animal and Veterinary Sciences, The University of Adelaide, Roseworthy, SA 5371, Australia
- Vertebrate Pest Research Unit, Department of Primary Industries NSW, Queanbeyan, NSW 2620, Australia
- School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW 2000, Australia
| |
Collapse
|
2
|
Immunological Cross-Protection between Different Rabbit Hemorrhagic Disease Viruses—Implications for Rabbit Biocontrol and Vaccine Development. Vaccines (Basel) 2022; 10:vaccines10050666. [PMID: 35632422 PMCID: PMC9143016 DOI: 10.3390/vaccines10050666] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Revised: 04/19/2022] [Accepted: 04/20/2022] [Indexed: 11/17/2022] Open
Abstract
The use of rabbit hemorrhagic disease virus (RHDV) as a biocontrol agent to control feral rabbit populations in Australia, in combination with circulating endemic strains, provides a unique environment to observe the interactions between different lagoviruses competing for the same host. Following the arrival of RHDV2 (GI.2) in Australia, it became necessary to investigate the potential for immunological cross-protection between different variants, and the implications of this for biocontrol programs and vaccine development. Laboratory rabbits of various immune status—(1) rabbits with no detectable immunity against RHDV; (2) rabbits with experimentally acquired immunity after laboratory challenge; (3) rabbits immunised with a GI.2-specific or a multivalent RHDV inactivated virus prototype vaccine; or (4) rabbits with naturally acquired immunity—were challenged with one of three different RHDV variants (GI.1c, GI.1a or GI.2). The degree of cross-protection observed in immune rabbits was associated with the variant used for challenge, infectious dose of the virus and age, or time since acquisition of the immunity, at challenge. The immune status of feral rabbit populations should be determined prior to intentional RHDV release because of the high survival proportions in rabbits with pre-existing immunity. In addition, to protect domestic rabbits in Australia, a multivalent RHDV vaccine should be considered because of the limited cross-protection observed in rabbits given monovalent vaccines.
Collapse
|
3
|
Abrantes J, Lopes AM. A Review on the Methods Used for the Detection and Diagnosis of Rabbit Hemorrhagic Disease Virus (RHDV). Microorganisms 2021; 9:972. [PMID: 33946292 PMCID: PMC8146303 DOI: 10.3390/microorganisms9050972] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2021] [Revised: 04/26/2021] [Accepted: 04/27/2021] [Indexed: 01/10/2023] Open
Abstract
Since the early 1980s, the European rabbit (Oryctolagus cuniculus) has been threatened by the rabbit hemorrhagic disease (RHD). The disease is caused by a lagovirus of the family Caliciviridae, the rabbit hemorrhagic disease virus (RHDV). The need for detection, identification and further characterization of RHDV led to the development of several diagnostic tests. Owing to the lack of an appropriate cell culture system for in vitro propagation of the virus, much of the methods involved in these tests contributed to our current knowledge on RHD and RHDV and to the development of vaccines to contain the disease. Here, we provide a comprehensive review of the RHDV diagnostic tests used since the first RHD outbreak and that include molecular, histological and serological techniques, ranging from simpler tests initially used, such as the hemagglutination test, to the more recent and sophisticated high-throughput sequencing, along with an overview of their potential and their limitations.
Collapse
Affiliation(s)
- Joana Abrantes
- CIBIO/InBio-UP, Centro de Investigação em Biodiversidade e Recursos Genéticos, Universidade do Porto, 4485-661 Vairão, Portugal;
- Departamento de Biologia, Faculdade de Ciências da Universidade do Porto, 4169-007 Porto, Portugal
| | - Ana M. Lopes
- CIBIO/InBio-UP, Centro de Investigação em Biodiversidade e Recursos Genéticos, Universidade do Porto, 4485-661 Vairão, Portugal;
- Instituto de Ciências Biomédicas Abel Salazar (ICBAS)/Unidade Multidisciplinar de Investigação Biomédica (UMIB), Universidade do Porto, 4050-313 Porto, Portugal
| |
Collapse
|
4
|
Mahar JE, Read AJ, Gu X, Urakova N, Mourant R, Piper M, Haboury S, Holmes EC, Strive T, Hall RN. Detection and Circulation of a Novel Rabbit Hemorrhagic Disease Virus in Australia. Emerg Infect Dis 2018; 24:22-31. [PMID: 29260677 PMCID: PMC5749467 DOI: 10.3201/eid2401.170412] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The highly virulent rabbit hemorrhagic disease virus (RHDV) has been widely used in Australia and New Zealand since the mid-1990s to control wild rabbits, an invasive vertebrate pest in these countries. In January 2014, an exotic RHDV was detected in Australia, and 8 additional outbreaks were reported in both domestic and wild rabbits in the 15 months following its detection. Full-length genomic analysis revealed that this virus is a recombinant containing an RHDVa capsid gene and nonstructural genes most closely related to nonpathogenic rabbit caliciviruses. Nationwide monitoring efforts need to be expanded to assess if the increasing number of different RHDV variants circulating in the Australian environment will affect biological control of rabbits. At the same time, updated vaccines and vaccination protocols are urgently needed to protect pet and farmed rabbits from these novel rabbit caliciviruses.
Collapse
|
5
|
Jennings S, Mutze G. Multiple warren use by subadult wild rabbits, Oryctolagus cuniculus, and its implications for disease transmission. WILDLIFE RESEARCH 2017. [DOI: 10.1071/wr17042] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Context
Contact rates are a key determinant of disease transmission. Territorial behaviour has generally been considered to limit contact between European rabbits occupying different warrens, particularly during the breeding season.
Aims
We investigated warren use by subadult rabbits during a period of low population density to determine their potential role in transmission of rabbit haemorrhagic disease and myxomatosis.
Methods
Subadult rabbits were radio-collared in late summer and relocated twice-weekly for 25 weeks, during which time they grew to adult size and breeding commenced.
Key results
Rabbits of both sexes used an average of four warrens each on a regular basis, even after older rabbits had commenced breeding. Warrens used by individual rabbits formed a continuously overlapping, irregular array. Subadult rabbits did not belong to separate social groups that utilised separate groups of warrens.
Conclusions
Subadult or young adult rabbits did not display the same territorial warren fidelity that had been previously described for rabbits. They have potential to carry pathogens between warrens at a landscape scale.
Implications
Movement of subadult rabbits between warrens is therefore likely to play a critical role in disease transmission, particularly when population density is low. This may help to explain the prevalent seasonality of RHD epizootics in spring when first-born litters of each breeding season typically reach that size.
Collapse
|
6
|
Liu J, Kerr PJ, Wright JD, Strive T. Serological assays to discriminate rabbit haemorrhagic disease virus from Australian non-pathogenic rabbit calicivirus. Vet Microbiol 2012; 157:345-54. [DOI: 10.1016/j.vetmic.2012.01.018] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2011] [Revised: 01/17/2012] [Accepted: 01/19/2012] [Indexed: 10/14/2022]
|
7
|
García-Bocanegra I, Astorga RJ, Napp S, Huerta B, Carbonero A, Perea A, Arenas A. Factors affecting the seroprevalence of lagovirus infection in wild rabbits (Oryctolagus cuniculus) in Southern Spain. Vet J 2010; 189:89-94. [PMID: 20643566 DOI: 10.1016/j.tvjl.2010.06.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2009] [Revised: 06/14/2010] [Accepted: 06/16/2010] [Indexed: 11/25/2022]
Abstract
Cross-sectional studies were carried out on wild rabbit (Oryctolagus cuniculus) populations in Southern Spain to assess the prevalence of lagovirus infection and to identify potentially associated risk factors. A total of 619 blood and 487 liver samples from wild rabbits were collected from seven hunting areas with different Mediterranean ecosystems. Logistic regression analysis was used to assess associations between seropositivity and an extensive set of variables. The seroprevalence was 29.2% (95% CI: 25.6-32.8) and lagoviruses were not detected in liver samples. Logistic regression indicated that seropositivity to lagoviruses was associated with seropositivity to myxomatosis, wild rabbit density, the existence of artificial feeding sites, mean maximum monthly temperatures of 20-30 °C, and annual accumulated rainfall of >600 mm.
Collapse
Affiliation(s)
- Ignacio García-Bocanegra
- Departamento de Sanidad Animal, Facultad de Veterinaria, UCO, Campus Universitarios de Rabanales, Apdo. 14071 Córdoba, Spain.
| | | | | | | | | | | | | |
Collapse
|
8
|
McPhee SR, Butler KL, Kovaliski J, Mutze G, Capucci L, Cooke BD. Antibody status and survival of Australian wild rabbits challenged with rabbit haemorrhagic disease virus. WILDLIFE RESEARCH 2009. [DOI: 10.1071/wr08137] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
In Australia, the epidemiology of rabbit haemorrhagic disease virus (RHDV) is complicated by non-pathogenic forms of calicivirus (bCV) co-circulating with RHDV and providing variable protection from RHDV. Currently no bCV virus-specific antibody tests exist; however, a series of four ELISAs used to detect antibodies to RHDV provided an indirect means to detect antibodies to bCV, enabling antibody categories of seronegative, maternal RHDV, RHDV or bCV to be determined. Rabbits (188) from four locations were challenged with RHDV and logistic regression models determined that, for rabbits <15 months old, survival was dependent on antibody titres alone and the relationship did not vary with age, capture site, gender, liveweight or reproductive status. All rabbits survived challenge after reaching 15 months of age, irrespective of their antibody titres. Where bCV antibodies were prevalent in young rabbits, the bCV category did not adequately summarise all information about rabbit survival that can be obtained from antibody titres. Within antibody categories, 95% of rabbits with RHDV, 33% with bCV, 40% with maternal RHDV and 22% with seronegative antibodies survived. The high survival rate of adults implies that natural outbreaks or controlled releases of RHDV will have little impact on adult breeding rabbits. Therefore, where RHDV and bCV are endemic, conventional rabbit-control programs targeting the immune breeding populations should provide the most predictable outcome for long-term maintenance of low rabbit populations.
Collapse
|
9
|
Buddle BM, de Lisle GW, McColl K, Collins BJ, Morrissy C, Westbury HA. Response of the North Island brown kiwi, Apteryx australis mantelli and the lesser short-tailed bat, Mystacina tuberculata to a measured dose of rabbit haemorrhagic disease virus. N Z Vet J 2005; 45:109-13. [PMID: 16031964 DOI: 10.1080/00480169.1997.36004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Four North Island brown kiwis and six lesser short-tailed bats were inoculated intramuscularly with 300 000 rabbit lethal doses of rabbit haemorrhagic disease (RHD) virus. No clinical abnormalities were observed in the kiwis and bats throughout the study period. Although no viraemia was detected in any of the kiwis, all four birds produced a serological response to RHD virus above the positive cut-off by 14 days after inoculation, and in two of the birds, antibodies persisted for over 5 months. Two kiwis were killed 48 days after inoculation. Their tissues were examined for lesions, and for the presence of persistent virus by both reverse transcription polymerase chain reaction and by inoculation of tissue suspensions into rabbits. No gross or histological lesions suggestive of a viral infection were detected and tests for detection of virus were negative. The serological response in the kiwis was probably due to the birds responding to viral antigen in the inoculum rather than to multiplication of the virus. None of the bats showed a serological response to RHD virus above the positive cut-off by 14 days after inoculation and the results of the pathological and virological examinations were negative.
Collapse
Affiliation(s)
- B M Buddle
- AgResearch, Wallaceville Animal Research Centre, PO Box 40-063, Upper Hutt, New Zealand
| | | | | | | | | | | |
Collapse
|
10
|
Philbey AW, Kirkland PD, Saunders GR. Assessment of antibodies to rabbit haemorrhagic disease virus in fox serum as an indicator of infection in sympatric rabbit populations. Aust Vet J 2005; 83:97-100. [PMID: 15971829 DOI: 10.1111/j.1751-0813.2005.tb12207.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
OBJECTIVE To assess the value of foxes as indicators of rabbit haemorrhagic disease virus in sympatric populations of rabbits. DESIGN Serum samples from 341 foxes in central western New South Wales were tested for exposure to rabbit haemorrhagic disease virus using antibody cELISAs. Selected samples were tested for viral antigens by ELISA, viral nucleic acids by reverse transcriptase PCR and viral infectivity by rabbit inoculation. RESULTS Antibodies against rabbit haemorrhagic disease virus were first detected in foxes 4 months after rabbit haemorrhagic disease was observed in rabbits in the same area. There was evidence of exposure of foxes to the virus in two subsequent years. A proportion of antibody positive, inconclusive and negative serum samples from foxes gave false positive results in an antigen ELISA for rabbit haemorrhagic disease virus. These serum samples were negative for viral nucleic acid by reverse transcriptase PCR and for infectious virus by rabbit inoculation. Liver samples from foxes were negative for viral antigens. CONCLUSIONS Antibodies against rabbit haemorrhagic disease virus in fox serum can serve as an index of the occurrence of rabbit haemorrhagic disease in rabbit populations. Some fox serum samples exhibit false positive reactivity in an antigen ELISA for rabbit viral haemorrhagic disease virus.
Collapse
Affiliation(s)
- A W Philbey
- Department of Veterinary Pathology, University of Glasgow, Bearsden Road, Glasgow G61 1QH, Scotland, United Kingdom.
| | | | | |
Collapse
|
11
|
Bruce JS, Twigg LE. The reintroduction, and subsequent impact, of rabbit haemorrhagic disease virus in a population of wild rabbits in south-western Australia. WILDLIFE RESEARCH 2005. [DOI: 10.1071/wr04025] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The natural arrival of rabbit haemorrhagic disease virus (RHDV) in south-western Australia in September 1996 resulted in a reduction in rabbit numbers of ~65% (~90% morbidity, with ~72% mortality of infected rabbits). As no signs of the disease (clinical or serological) were seen over the next two years, and as rabbit numbers over the last 12-month monitoring period at the site were similar to those observed before the natural 1996 RHDV epizootic (i.e. pre-RHD), RHDV was deliberately reintroduced into this rabbit population in April 1999 (autumn). Seven RHDV-inoculated rabbits were released prior to the main breeding season when <3% of sampled rabbits (n = 118) were seropositive for RHDV antibodies. Following the deliberate release, the overall decline in rabbit numbers (68%) was comparable to that seen during the natural 1996 epizootic. However, on the basis of the observed changes in rabbit numbers, and in their serology, the impact of the deliberate RHDV release appeared to be more variable across the six trapping areas than was seen during the natural 1996 spring epizootic. The reductions in rabbit numbers on these areas 6–8 weeks after RHDV-release ranged from 55% to 90%. The serology of the surviving rabbits on the trapping areas was also variable over this period, with the proportion of seropositive rabbits ranging from 5% to 90%. Overall, only 15% of the surviving rabbit population showed evidence of recent challenge by RHDV, giving a morbidity rate of 73% 8 weeks after the release. However, over 90% of infected rabbits died. This provides further evidence that some rabbits remained un-challenged by RHDV for up to 8 weeks after its release. The variable impact of the April 1999 release may have been partially caused by the observed differences in abundance of insect vectors, and/or an apparent increase in the incidence of non-virulent RHDV in the months preceding the release.
Collapse
|
12
|
Bruce JS, Twigg LE. Rabbit Haemorrhagic Disease Virus: serological evidence of a non-virulent RHDV-like virus in south-western Australia. WILDLIFE RESEARCH 2004. [DOI: 10.1071/wr04009] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Although several different cELISAs have been used to assess the exposure of European rabbits to rabbit haemorrhagic disease (RHD), the interpretation of the results of such assays is not always straight-forward. Here we report on such difficulties, and on the likely presence of a non-virulent rabbit haemorrhagic disease virus–like virus (nvRHDV-LV) in south-western Australia. Analysis of sera collected from European rabbits at Kojaneerup (near Albany) in Western Australia provided the first serological evidence of the likely presence of a nvRHDV-LV in wild rabbit populations outside the east coast of Australia and New Zealand, before the deliberate introduction of RHDV as biological control agent in both countries. Six out of 30 rabbits (20%) sampled 1–2 months before the known arrival of RHDV at Kojaneerup were seropositive to RHD on the basis of their IgG isoELISAs. However, none of these positive samples were positive for the RHDV antibody cELISA (1 : 10), indicating likely exposure to nvRHDV-LV. Subsequent serological analysis of 986 rabbits sampled between September 1996 and August 1999 at Kojaneerup indicated that nvRHDV-LV persisted in these rabbits following the natural arrival of RHDV in September 1996. At least 10–34% of rabbits appeared to have been exposed to nvRHDV-LV during the 3-year study. The presence of nvRHDV-LV seemed to offer only limited protection to rabbits from RHDV during the initial epizootic; however, persistence of nvRHDV-LV may have mitigated further RHDV activity after this epizootic. Fewer than 1% of rabbits (9 of 986) showed evidence of RHDV-challenge during the 30 months following the initial RHDV epizootic. Furthermore, except for the epizootic in September 1996, no clinical signs of the disease were apparent in the population until RHDV was deliberately reintroduced in April 1999. Mortality of rabbits exposed to RHDV at this time appeared to be correlated with their IgG isoELISA titre.
Collapse
|
13
|
McColl KA, Morrissy CJ, Collins BJ, Westbury HA. Persistence of rabbit haemorrhagic disease virus in decomposing rabbit carcases. Aust Vet J 2002; 80:298-9. [PMID: 12074312 DOI: 10.1111/j.1751-0813.2002.tb10848.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- K A McColl
- CSIRO Livestock Industries, Australian Animal Health Laboratory, Geelong, Victoria
| | | | | | | |
Collapse
|
14
|
Asgari S, Hardy JR, Sinclair RG, Cooke BD. Field evidence for mechanical transmission of rabbit haemorrhagic disease virus (RHDV) by flies (Diptera:Calliphoridae) among wild rabbits in Australia. Virus Res 1998; 54:123-32. [PMID: 9696121 DOI: 10.1016/s0168-1702(98)00017-3] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Field collected flies were screened for the presence of rabbit haemorrhagic disease virus (RHDV) by applying reverse transcriptase PCR (RT-PCR) in which primers specific to the capsid protein of the virus were used. The virus was detected in flies from locations where rabbit haemorrhagic disease (RHD) was reported and also soon after the release of RHDV in a 'clean' area. Oral and/or anal excretions of flies (flyspots) were found to contain viable virus and oral inoculation of rabbits revealed that a single flyspot was able to cause RHD. We conclude that flyspots are a major potential source of the virus for oral or conjunctival transmission of the virus to rabbits.
Collapse
Affiliation(s)
- S Asgari
- Department of Crop Protection, Waite Campus, Glen Osmond, SA, Australia.
| | | | | | | |
Collapse
|
15
|
Gould AR, Kattenbelt JA, Lenghaus C, Morrissy C, Chamberlain T, Collins BJ, Westbury HA. The complete nucleotide sequence of rabbit haemorrhagic disease virus (Czech strain V351): use of the polymerase chain reaction to detect replication in Australian vertebrates and analysis of viral population sequence variation. Virus Res 1997; 47:7-17. [PMID: 9037732 DOI: 10.1016/s0168-1702(96)01399-8] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The complete nucleotide sequence of the Czech strain of rabbit haemorrhagic disease virus (RHDV) was determined to be 7437 nucleotides in length with a 5-terminal non-coding region of 9 nucleotides and a 3'-terminal non-coding region of 59 nucleotides. Two open reading frames (ORFs) were found within this sequence coding for polypeptides of 2344 (nucleotides 10-7044) and 117 amino acids (nucleotides 7025-7378). The sequence of this isolate was approximately 1% different from that reported by Meyers et al., having 78 nucleotide changes which resulted in 30 amino acid differences, the majority of these clustering in the N-terminus of the large ORF and the middle of the viral coat protein. Only a single conservative amino acid change was seen in the smaller 3'-terminal ORF. Since the virus cannot at present be propagated in tissue culture, but isolated only after replication in rabbits, the reported sequence must be considered as a consensus sequence from the viral population. To gain some understanding of the possible sequence diversity within this virus population, 97 clones were sequenced from a polymerase chain reaction (PCR) fragment to determine the sequence diversity of the virus population. Four major classes of variant were described with mutations generally in the third base position of codons. A nested reverse transcriptase (RT) PCR (using sequence derived for the coat protein of RHDV) was used to determine the presence or absence of RHDV inoculated into non-host animal species. No replication of the virus was detected in 28 different vertebrate species other than rabbits. PCR tests on both mosquitoes and fleas feeding on RHDV infected rabbits were positive. The RT-PCR test was more sensitive when compared with an antigen capture ELISA to detect the presence of genomic RNA/or virus in infected rabbits.
Collapse
Affiliation(s)
- A R Gould
- CSIRO, Australian Animal Health Laboratory, Geelong Victoria, Australia
| | | | | | | | | | | | | |
Collapse
|