Rabbit Populations Research Articles

Hepatitis E virus infection in wild rabbit (Oryctolagus cuniculus) in Italy and in the UK: a serological, molecular, and pathological study

A novel animal strain of HEV demonstrating zoonotic potential rabbit HEV (rHEV) has been recently identified in farmed rabbits in China. To investigate the presence of rHEV in wild rabbit population, serum and tissue samples were taken from 65 rabbits, 35 Italian and 30 from UK. Sera were submitted to a double antigen sandwich ELISA, whereas hepatic tissues and other organs to molecular and pathological investigations. Sixteen serum samples (24.6%) scored positive for anti-HEV antibodies, and six samples (9%) of hepatic tissue were positive for HEV RT-PCR, while the other organs were negative. Sequencing and phylogenetic analysis of HEV RNA-positive samples indicated that while two Italian rabbits were infected with strains closely related to wild boar and swine strains (HEV-3), the other four (2 Italian and 2 English) were clustered within rHEV clade. Megalocytosis and multifocal areas of hepatocytes degeneration and necrosis with a pericentrilobular pattern were observed in rHEV-infected rabbits. In those infected by the strain analogous to HEV-3, the lesions were mainly localized in the periportal areas and were less severe. In both cases, inflammatory infiltrates were predominantly composed of CD3-positive lymphocytes and a reduced number of macrophages. By immunohistochemistry, only liver samples taken from HEV RNA-positive rabbits scored positive for viral antigen. Our results indicated that HEV infection is present in rabbit population with different clades and is endemic in the Italian and English wild rabbit population, suggesting the possibility that this species may be infected with rHEV or swine HEV-3 strains.

Does red fox (Vulpes vulpes) predation of young rabbits (Oryctolagus cuniculus) enhance mortality from myxomatosis vectored by European rabbit fleas (Spilopsyllus cuniculi)?

On introduction to Australia, European rabbit fleas spread myxomatosis among young wild rabbits during winter; recruitment into the adult rabbit population was strongly reduced. Nonetheless, the reasons behind the high efficacy of flea-borne myxomatosis remain poorly understood. A 17-year data set from Witchitie, a semi-arid site in South Australia, was reviewed to ask whether red foxes, specialist rabbit predators, could have enhanced mortality by preying on disease-debilitated rabbits. Advantage was taken of a natural experiment where, after initial establishment of fleas, drought greatly reduced their abundance, providing two periods for comparison, one where fleas actively spread myxoma virus, followed by another where fleas were no longer effective vectors and myxomatosis reverted to former mosquito-vectored summer outbreaks. The hypothesis that foxes contributed to the efficacy of flea-borne myxomatosis was not rejected. Instead, the study showed that when myxomatosis was being actively spread by fleas, foxes were not only abundant enough to have eaten most of the young rabbits produced each year, but fox population dynamics were also strongly associated with rabbit productivity. Related studies support the likelihood that predators significantly enhance disease-related mortality and indicate that further experimental study of an interaction between flea-borne myxomatosis and predation would be worthwhile.

Monitoring of the novel rabbit haemorrhagic disease virus type 2 (GI.2) epidemic in European wild rabbits (Oryctolagus cuniculus) in southern Spain, 2013–2017

Rabbit hemorrhagic disease (RHD) is a highly infectious disease in European rabbits (Oryctolagus cuniculus), caused by a virus belonging to the genus Lagovirus (RHDV; family Caliciviridae). In 2010, a new genotype of RHDV (RHDV2 or RHDVb, currently designated GI.2) emerged in France, affecting both domestic rabbits, even those vaccinated for the classical RHDV genotypes (currently designated GI.1) and wild rabbits. GI.2 was subsequently identified in other European countries. The aim of the present study was to monitor the GI.2 epidemic in wild rabbits in Andalusia (southern Spain) during the period 2013–2017.At the beginning of summer 2013, high mortalities were detected in wild rabbit populations in southern Spain. A total of 96 affected hunting or protected areas were surveyed. The first outbreak was observed on June 2013. The number of outbreaks sharply increased in 2013 and 2014, with a decreasing trend being observed during the following years. The spatial distribution of GI.2 was not homogeneous, since most of the detected outbreaks were concentrated in the western part of Andalusia. The outbreaks peaked in winter and spring and have been detected in the last five consecutive years, which suggests endemic circulation of GI.2 in wild rabbit populations in Spain.A total of 190 dead rabbits from 87 of the 96 areas surveyed were collected during the study period. Mortality affected rabbits of different age classes, including kittens. RT-PCR confirmed the presence of GI.2 RNA in the livers of 185 of the 190 (97.4%) rabbits. Phylogenetic analysis performed on eleven samples collected in different provinces of Andalusia between 2013 and 2017, showed high nucleotide identity with GI.2 strains Spain, France and Portugal. The results constitute an important step in understanding of the emergence and spread of GI.2 in this country and will provide valuable information for the development of surveillance programs in Europe.

Abstract 1465: Priming immunity against SCLC with oncolytic virotherapy

Abstract Small cell lung cancer (SCLC) is an aggressive subtype of lung cancer with few treatment advances over the past 3 decades and poor survival. High levels of tumor infiltrating immune cells are associated with improved SCLC patient survival Independent of tumor stage, patient performance status or treatment. Oncolytic virotherapy presents a new approach where tumor specific infection and replication stimulate host immune responses and increase infiltrating immune cells. Myxoma virus (MYXV) has been widely tested in Australia to control rabbit populations with no toxicity to humans. We have now shown that MYXV selectively infects SCLC cells with no cytotoxicity to normal tissues. In vitro studies were performed using human, murine, and cisplatin-resistant SCLC cell lines. Efficient MYXV infection, replication, and cytotoxicity was observed in all SCLC cell lines with rapid induction of immunogenic cell death (ICD), demonstrating MYXV is effective for SCLC regardless of cisplatin resistance. In contrast, we did not detect productive infection or cytotoxicity in non-tumor cells. Using an optimized conditional genetically engineered mouse (GEM) model (Ad-Cre mediated p53/Rb1/p130 null) we show untreated advanced SCLC tumors are devoid of infiltrating immune cells. Following intrapulmonary MYXV treatment, MYXV localized exclusively within lungs of tumor bearing mice and was cleared by 7 days. Despite clearance within 7 days, a robust immune response was sustained 30 days after MYXV treatment. When intrapulmonary MYXV is administered in combination with anti-PD-1 or anti-CTLA-4, both combinations show greater reduction in tumor burden throughout the lung compared to MYXV alone at the 60 day post treatment timepoint. In addition, the immune cell population localized within SCLC tumors were enhanced following combined MYXV/anti-PD-1 at 60 days post treatment. In our GEM model, MYXV alone results in a statistically significant prolongation of survival compared to both PBS and cisplatin treated animals. To determine the effect of MYXV delivered by intratumoral injection we utilized patient derived xenografts (PDX) and newly developed subcutaneous syngeneic tumor models for SCLC in immunocompetent mice. Following MYXV treatment in PDX tumors we observed extensive necrosis and persisting virus detected 10 days post treatment. In our immunocompetent subcutaneous syngeneic tumor model, MYXV is cleared by 7 days, which is consistent with clearance following intrapulmonary MYXV delivery in our GEM model. This was accompanied by extensive necrosis, reduction in tumor volume, increased infiltrating immune cells, and induction of de novo endogenous tumor specific antibody responses. In conclusion, we demonstrate the potential for MYXV as an oncolytic virotherapy for SCLC, with selective infection leading to enhanced anti-tumor immune responses. Citation Format: Patrick Kellish, Connor Hartzell, Daniil Shabashvili, Masmudur M. Rahman, Maria V. Guijarro, Akbar Nawab, Grant McFadden, Frederic J. Kaye, Maria Zajac-Kaye. Priming immunity against SCLC with oncolytic virotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1465.

Auto-Allo Graft Parallel Juxtaposition for Improved Neuroregeneration in Peripheral Nerve Reconstruction Based on Acellular Nerve Allografts.

Nerve repair poses a significant surgical challenge, and much research on this topic for improvement in reconstruction of segmental defects is ongoing. The aims of the study were to reconfirm the accuracy and safety of a previously described nerve decellularization method on a larger experimental population of rabbits, as well as on human nerves, and to establish in vivo the efficacy of a new-concept mixed graft, comprising autologous and acellular nerve allograft components within the same graft. Acellular nerve allografts were implanted into tibial nerve defects of 5 rabbits (group A), autografts were implanted, representing the criterion standard, in other 5 animals (group B), and the innovative technique was used in the remaining 5 (group C). Twelve weeks postoperatively, nerve conduction evaluations were performed; animals were euthanatized, and grafts were harvested and morphologically, histomorphometrically, and immunohistochemically analyzed. Eventually, a preliminary in vitro validation of the decellularization method was performed on human nerves from a cadaver. No clinical adverse effect was revealed during all the experimental times. No tissue reaction was observed, and in all groups, regenerated fascicles and bundles were shown by histology. However, both histology and histomorphometry demonstrated a better regenerative efficiency in group C. The morphological evaluation of the human nerve treated with the novel method showed complete decellularization. The microsurgical combined model demonstrated a better neuroregeneration than did pure autografts and acellular nerve allografts. The decellularization method seemed effective also on human nerves. Deeper investigations are necessary to further validate and transfer this new encouraging protocol to the clinical arena.

Carrion flies as sentinels for monitoring lagovirus activity in Australia.

Lagoviruses are an essential tool for managing wild rabbit populations in Australia. Our understanding of lagovirus epidemiology in Australia currently depends on members of the public submitting liver samples from dead lagomorphs (i.e. rabbits and hares) through a monitoring program called Rabbitscan. However, many wild lagomorphs die in inaccessible locations or are scavenged before sampling can occur, leading to considerable sampling bias. In this study, we screened field-caught carrion flies for the presence of lagoviruses to monitor virus circulation patterns in the landscape, with an aim to establish a less biased epidemiological surveillance tool. Carrion flies were collected from two study sites over a 22-month period and these samples were used to optimize and validate molecular testing methods in this sample type for the currently circulating lagovirus variants. Virus was clearly detectable in field-caught carrion flies using optimized SYBR-green RT-qPCR and RT-PCR assays. However, variant identification was frequently hindered by the low virus loads present in carrion fly samples and spurious RT-PCR amplification. This was overcome by frequent sampling, which effectively acts as replicate sampling to verify inconclusive results. There was generally good correlation between virus detections and variant identification in carrion flies and in samples recovered from wild lagomorphs. The methods reported here provide an additional surveillance tool to monitor lagovirus spread and circulation at a landscape scale, which in turn can help to guide more effective rabbit management programs.

Gastrointestinal parasites of the New England cottontail rabbit (Sylvilagus transitionalis) and eastern cottontail rabbit (Sylvilagus floridanus) in the Hudson Valley, New York.

The New England cottontail rabbit (NEC, Sylvilagus transitionalis) population has decreased dramatically in New York, USA, and the role of parasites in limiting the population has never been examined. The closely related and sympatric eastern cottontail rabbit (EC, Sylvilagus floridanus) was introduced into the range of NEC by humans and is currently thriving. This study aimed to investigate gastrointestinal parasites of the NEC and the EC and compare their parasite communities. Fecal pellets from 195 NEC and 125 EC were collected from the Hudson Valley, New York, in the winter of 2013-2014. Centrifugal fecal floats were performed in Sheather's sugar solution, and parasite ova and cysts were examined microscopically to identify gastrointestinal parasites present. For all pellets combined (n = 320), 91% were found to harbor at least 1 parasite species, with Eimeria species being the most common. Genetic analysis of pellets using microsatellite DNA identified 248 individual rabbits, with parasite prevalence (94%) similar to the prevalence estimate based on all pellets (91%). EC samples had a significantly higher (p < 0.05) parasite species richness (1.73, range 0-4) than NEC (1.20, range 0-3). EC and NEC shared 3 moderate to high (9-89%) prevalence parasites, in which EC prevalence was consistently higher. One parasite specieswas only found in NEC, and two were only found in EC, but the majority of these were of low abundance, precluding further statistical analyses.

Genetic Characterization of a Recombinant Myxoma Virus in the Iberian Hare (Lepus granatensis).

Myxomatosis is a lethal disease in wild European and domestic rabbits (Oryctolagus cuniculus), which is caused by a Myxoma virus (MYXV) infection—a leporipoxvirus that is found naturally in some Sylvilagus rabbit species in South America and California. The introduction of MYXV into feral European rabbit populations of Australia and Europe, in the early 1950s, demonstrated the best-documented field example of host–virus coevolution, following a cross-species transmission. Recently, a new cross-species jump of MYXV has been suggested in both Great Britain and Spain, where European brown hares (Lepus europaeus) and Iberian hares (Lepus granatensis) were found dead with lesions consistent with those observed in myxomatosis. To investigate the possibility of a new cross-species transmission event by MYXV, tissue samples collected from a wild Iberian hare found dead in Spain (Toledo region) were analyzed and deep sequenced. Our results reported a new MYXV isolate (MYXV Toledo) in the tissues of this species. The genome of this new virus was found to encode three disruptive genes (M009L, M036L, and M152R) and a novel ~2.8 kb recombinant region, which resulted from an insertion of four novel poxviral genes towards the 3’ end of the negative strand of its genome. From the open reading frames inserted into the MYXV Toledo virus, a new orthologue of a poxvirus host range gene family member was identified, which was related to the MYXV gene M064R. Overall, we confirmed the identity of a new MYXV isolate in Iberian hares, which, we hypothesized, was able to more effectively counteract the host defenses in hares and start an infectious process in this new host.

Morphological diversity of wild rabbit populations: implications for archaeology and palaeontology

Abstract Morphometric characteristics of the European rabbit (Oryctolagus cuniculus) are regularly used in archaeological and palaeontological studies to explore aspects of prehistoric human hunting behaviour, to reconstruct past environments or to define new species. However, the variability of these characteristics is still both poorly understood and under-documented due to a lack of population-level data that are essential for reliably interpreting the fossil record of this species. Here we address the morphometric diversity of wild rabbits in seven current populations from south-western Europe. Size variations in different skeletal parts were analysed to explore the potential impact of sexual dimorphism. A geometric morphometric analysis of the third lower premolar (p3) – a tooth commonly used to distinguish leporid species – was used to evaluate the relative effects of size, phylogeny, geographical location and climate on shape variation. The results show a negligible impact of sexual dimorphism, contradicting previous studies. We also demonstrate geography and climate to be the main factors driving variation in p3 shape, potentially calling into question criteria typically used to identify rabbit species. These results are valuable not only for palaeobiologists studying the taxonomy and the evolutionary history of the leporid family but also for archaeologists interested in the socio-economic and behavioural aspects of Palaeolithic human groups.

Semen characteristics and seminal oxidative status of four breeds of rabbit in South\xa0west, Nigeria

BackgroundWithin the rabbit population in South West of Nigeria, four exotic breeds of rabbits consisting of Fauve de Bourgogne, Chinchilla, British Spot, and New Zealand White were evaluated for their reproductive response. This investigation was carried out within July and August, when the least temperature-humidity index (THI) (ranged between 23.41 and 25.30) is observed in Ibadan, South West, Nigeria, which depicts the highest thermal comfort in the study area. Thirty bucks per breed, housed individually and randomly allotted to experimental units, were used for this study. All bucks were made to serve an artificial vagina, libido was evaluated, and the collected ejaculates were assessed for semen characteristics, seminal biochemical parameters, and oxidative stress indices weekly for 4 weeks. Two ejaculates per buck were collected weekly. The first ejaculate for spermiogram and the second ejaculate was centrifuged at 4000 rpm for 15 min to separate seminal plasma and used for biochemical analysis using standard procedures.ResultThe result obtained revealed that sexual urge (reaction time) in the four breeds was similar statistically. British Spot and New Zealand White breeds despite recording a lower semen volume had apparently higher mass motility, individual sperm motility, and significantly higher (P < 0.05) sperm concentration compared with the other breeds. Genetic differences in breeds were evident in most oxidative stress markers, except for the total antioxidant activity of seminal fluid. New Zealand White had the highest antioxidant enzyme activity.ConclusionNew Zealand White had the best oxidative status among the four breeds, and this enhanced its semen quality parameters among the rabbit breeds.

Oxidative stress indicators of rabbit breeds in Ibadan, Southwest Nigeria

BackgroundWithin the rabbit population in Southwest of Nigeria, four breeds of rabbits consisting of Fauve de Bourgogne, Chinchilla, British Spot, and New Zealand White were evaluated for their oxidative status, as indices of physiological adaptation for optimal productivity. This investigation was carried out within July and August when least temperature-humidity index (THI) is observed in Ibadan, Southwest Nigeria. Thirty bucks per breed were housed individually and randomly allotted to experimental units. Blood samples were collected from all bucks and serum obtained using standard procedures. Serum oxidative stress indicators assay include total antioxidant capacity, lipid peroxidation, superoxide dismutase (SOD), catalase, and glutathione peroxidase activity was determined using standard procedures.ResultsResults revealed that serum lipid peroxidation, total antioxidant activity, catalase, and glutathione peroxidase were not significantly (p > 0.05) affected by the breeds of rabbit. Fauve de Bourgogne, Chinchilla, and New Zealand White had statistically similar serum SOD activity and were significantly (p < 0.05) higher than serum SOD activity of British Spot rabbits. This shows that British Spot has the least superoxide anion scavenging ability across the breeds.ConclusionThe breeds of rabbit assessed have similar oxidant generation capacity and antioxidant production, except British Spot that has the least superoxide scavenging which could increase oxidant accumulation within this breed of rabbit.

Locating myxomatosis resistance

Evolution![Figure][1] Rabbits around a waterhole at the myxomatosis trial enclosure on Wardang Island, Australia, in 1938 PHOTO: NATIONAL ARCHIVES OF AUSTRALIA Myxomatosis is a viral infection that was deliberately introduced from American cottontail rabbits into European rabbit populations to control their population. Over the past 60 years or so, similar resistance variants have emerged in parallel in the United Kingdom, France, and Australia. Alves et al. discovered that the basis for this resistance is polygenic, with selection converging on several host immunity and proviral alleles (see the Perspective by Miller and Metcalf). Interestingly, it now seems that the virus is counterevolving immune suppressive traits. Science , this issue p. [1319][2]; see also p. [1277][3] [1]: pending:yes [2]: /lookup/doi/10.1126/science.aau7285 [3]: /lookup/doi/10.1126/science.aaw8710

Isolation, identification and antibiogram of Pasteurella multocida isolated from apparently healthy rabbits in Al-Bayda, Libya

The aim of this study was to investigate the prevalence of Pasteurella multocida in upper respiratory tract (nasal cavities) of apparently healthy rabbits. Twenty adult and young rabbits were sampled, using sterile cotton swabs for sample collection from the nasal cavities of test animals. Swabs were put into nutrient broth and incubated at 37° C for 24 hrs. nasal swabs from 14 of the 40 samples rabbits (35%) showed visible growth suggestive of P. multocida, eleven (78.6%) of the isolates were males, and three isolates (21.4%) were females, whereas 26 samples (65%) were negative. Presumptive identification of the isolates was performed according to conventional bacteriological methods of gross colonial morphology, Gram staining reaction, microscopic characteristics and biochemical tests. Results achieved in this study indicate that P. multocida is harbored in the upper respiratory tract of nearly third of the rabbit population in the laboratory animal unit of the faculty of veterinary Medicine, Omer Al- Muktar university. Antimicrobial sensitivity of P. multocida isolated were tested against seven antibacterial antibiotics. 100% of the isolates were found to be sensitivity to Neomycin and 71.4% were sensitivity to Tetracycline; Erythromycin and Streptomycin should sensitivity of 50% and 14.3%, respectively. One of the hand all isolates found to be resistant to Ofloxacin, Amoxicillin and Cephalexin.

Parallel adaptation of rabbit populations to myxoma virus.

In the 1950s the myxoma virus was released into European rabbit populations in Australia and Europe, decimating populations and resulting in the rapid evolution of resistance. We investigated the genetic basis of resistance by comparing the exomes of rabbits collected before and after the pandemic. We found a strong pattern of parallel evolution, with selection on standing genetic variation favoring the same alleles in Australia, France, and the United Kingdom. Many of these changes occurred in immunity-related genes, supporting a polygenic basis of resistance. We experimentally validated the role of several genes in viral replication and showed that selection acting on an interferon protein has increased the protein's antiviral effect.

Supplementary food reduces home ranges of European wild rabbits in an intensive agricultural landscape

Understanding use of space in free ranging populations that cause damage to agriculture can help in the design of measures aimed at reducing their impact. Food availability is known to determine use of space in terrestrial vertebrates so, providing alternative food sources during a specific time period may help the management of vertebrate pests by reducing their ranging behavior. We investigated space use by a crop damaging species, the European wild rabbit (Oryctolagus cuniculus), in an intensively-managed agricultural landscape within its native range and evaluated the potential of food availability to restrict areas of rabbit activity. We determined the size of day-time home range (95% minimum convex polygon, MCP) and core area (50% MCP) of rabbits before and after providing additional food to one rabbit population, while an unsupplemented population served as a control. Rabbits in the study area had large home ranges in comparison with those previously reported in the literature, probably linked to the heterogeneous and unpredictable distribution of resources in intensively-managed Mediterranean agro-ecosystems. There was a general reduction in size of home ranges and core areas between the experimental phases, but we found evidence that additional feeding restricted the space use of rabbits. The wide-ranging behavior of rabbits documented in the present study might explain why even moderate rabbit densities can cause widespread damage to crops. These findings may facilitate the design of management tools to mitigate damage in agricultural areas where rabbits are considered an agricultural pest.

Does short‐term habitat management for the European rabbit (Oryctolagus cuniculus) have lasting effects?

AbstractThe European rabbit Oryctolagus cuniculus, a keystone species of Mediterranean ecosystems, is the target of several recovery and management plans throughout the Iberian Peninsula. The majority of these plans are limited in time by budget constraints and lack postintervention monitoring of population trends. This study was conducted in south‐west Portugal and aimed to understand the effect of habitat management and its early cessation on rabbit populations. We assessed rabbit presence and relative abundance before management (2007), during the implementation of measures (2008), immediately after (2009) and 3 years after measures ended (2012). We applied a model selection approach, using generalized linear models to determine the relative importance of MANAGED and UNMANAGED habitat features on rabbit presence in each year. We used spatial eigenvector mapping to describe the spatial autocorrelation in rabbit presence and a variation partitioning approach to quantify the relative effects of management‐related variables, unmanaged environmental descriptors and spatial characteristics on rabbit presence. Rabbit presence and abundance increased shortly after the management intervention but decreased 3 years after. Rabbit presence was positively related to the proximity of installed crops and the existence of favorable soils for digging. Habitat management‐related variables explained most of the variation in all models. Habitat improvement actions, particularly the sowing of pastures, contributed to increased rabbit presence. We propose a continued long‐term intervention and the cultivation of crops with auto‐regeneration properties (e.g., subterranean clover—Trifolium subterraneum) with the aim of continuing to increase rabbit presence and abundance in areas where rabbit populations are scarce.

Is restocking a useful tool for increasing rabbit densities?

The European rabbit (Oryctolagus cuniculus) is endemic to Mediterranean ecosystems in the Iberian Peninsula, where it is a key species. In recent years its populations have declined due to several factors including habitat transformation and viral diseases. At the same time, corrective measures including population restocking in areas with low population densities using rabbits from other geographical areas have been performed. In this study we evaluate the impact restocking has had on the population dynamics of native rabbits in the Doñana National Park. As part of the natural processes monitoring program carried out in the Doñana Biological Station (ESPN-EBD-CSIC), rabbit censuses were conducted in spring and late summer in 2005–2015 at dusk and at night along six fixed transects in habitats harbouring rabbit populations.In order to take into account restocked rabbit numbers, annual reports from the Doñana Natural Area and data provided by the Lynx team of the LIFE project were incorporated into the study. In all, 52 336 rabbits from different parts of western Andalusia were released in the Doñana Biosphere Reserve in 2005–2015. Yet, rabbit populations underwent significant declines, above all in 2013 and 2015, with decreases in some areas of up to 80%. These results show intensive rabbit restocking did not increase the native rabbit populations numbers. The impact of the release of rabbits on the population dynamics of the species in Doñana is discussed.

Lethal biological control of rabbits – the most powerful tools for landscape-scale mitigation of rabbit impacts in Australia

ABSTRACT The viral biocontrol agents Myxoma virus (MYXV) and Rabbit Haemorrhagic Disease Virus (RHDV1), released in 1950 and 1996 respectively, are the only control tools to have resulted in significant and lasting landscape-scale suppression of rabbit populations in Australia. Multiple conservation benefits and significant economic savings have resulted from the long-term and widespread reductions in rabbit numbers and impacts. In an effort to ‘boost’ rabbit biocontrol, an additional variant of RHDV1 ('K5') was recently released nationwide to counteract the decreasing effectiveness of both RHDV1 and MYXV that results from the evolutionary ‘arms race’ between viruses and their hosts. Two years prior to the K5 release, an exotic RHDV strain (RHDV2) appeared in Australia. The commercially available vaccine used to protect pet and farmed rabbits against the officially released K5 was ineffective against the exotic RHDV2, resulting in numerous deaths of domestic rabbits. This created substantial confusion about which strain was released as a biocontrol tool, as well as renewed concerns amongst pet rabbit owners and rabbit farmers about the use of viruses as lethal rabbit control tools in general. Ongoing effective control of wild rabbits in Australia is absolutely essential to protect the substantial conservation gains made by the long-term suppression of rabbit numbers over the past decades, and there is currently no alternative population control tool to achieve this at the required landscape scale. Vaccine formulations need updating to protect non-target farmed and pet rabbits from circulating field variants, including RHDV2, and to increase public acceptance for the ongoing use of viral biocontrol for feral rabbit populations.

Detection and characterisation of rabbit haemorrhagic disease virus strains circulating in Egypt

Rabbit haemorrhagic disease (RHD) is a highly virulent viral disease of Oryctolagus cuniculus which threatens the rabbit population in Egypt and worldwide. The etiological agent is the rabbit haemorrhagic disease virus (RHDV), a member of the family Caliciviridae. The aim of this study was to identify the possible evolutionary changes of the currently circulating RHDV in Egypt. Twenty suspected cases were collected from outbreaks that occurred in non-vaccinated rabbit flocks during 2015 and 2016. Liver homogenate samples were investigated for detection and identification of circulating RHDV using haemagglutination (HA) and reverse transcriptase polymerase chain reaction. Further characterisation of selected five viral strains was performed by nucleotide sequencing of VP60 gene. All twenty tested samples were haemagglutinin positive and VP60 gene was amplified. Based on nucleotide sequence analysis, four isolates were identified as classical RHDV strains, while one isolate was assigned as RHDVa variant strain but with the same HA pattern. The new RHDVb variant was not identified.

Recent production status, research results and development conditions of rabbit production in Vietnam - A review

Rabbit production is well developed in different regions of Vietnam due to abundant feed resources, suitable climate and good raising experiences with the total rabbit population of 5,844,000 in 2014. There are many production models created by producers, which show the technical and economic effectiveness for production contributing to the poor alleviation and prosperous income. Rabbit meat consumption is also increased in the cities and rural areas from year to year. In this paper the current situation development, research results on breeds, nutrition, feed resources, rabbit performance of meat and reproduction, markets and development strategies are presented. The constraints of production development such as low breed quality, few intensive large farms, limited necessary studies, poor marketing and less international co-operation are also discussed.herbivores, breeding, keeping, production improvement, benefits.