Vaccin lapin vhd

Dois-je faire vacciner mon NAC?

Il n’y a que deux espèces parmi les NAC pour lesquels il existe des protocoles de vaccination recommandés : le furet et le lapin. Il n’y a donc pas de vaccination obligatoire, à une exception près : la vaccination contre le virus de la rage chez le furet sous certaines conditions.

QUEL(S) VACCIN(S) POUR MON FURET ?

En effet, le furet est inclus dans la « famille » des carnivores domestiques et est donc soumis au mêmes règles que les chiens et les chats, à savoir : vaccination antirabique obligatoire de l’animal pour passer les frontières françaises (dans un sens comme dans l’autre!). Cette vaccination peut être également requises pour que votre animal soit autorisé à séjourné dans un camping sur le territoire français.

A savoir pour éviter les mauvaises surprises :

Il est également conseillé de vacciner les furets contre la maladie de Carré. Il s’agit d’une maladie virale très contagieuse et toujours mortelle qui ne se déclare que chez les individus non vaccinés. C’est une maladie que l’on rencontre également chez le chien. Les symptômes sont très divers : syndrome fébrile, signes respiratoires, signes cutanés, signes nerveux. Les cas sont rares grâce à la protection vaccinale de la population de furet domestique, ce qui justifie de continuer cette pratique. A ce jour, aucun vaccin ne contenant que la valence maladie de Carré n’est disponible ni autorisé sur le marché français. Pour vacciner les furets, il est donc nécessaire d’utiliser un vaccin à destination du chien qui contiendra le moins de valence possible afin d’éviter une stimulation inutile du système immunitaire contre des maladies qui ne concerne pas le furet.

Quel protocole vaccinal pour mon furet ?

En fonction de l’âge du furet, la primo-vaccination se fait en 2 à 3 injections. Concernant le rappel de vaccination, une étude récente montre que les anticorps vaccinaux protégeraient 95% des furets vaccinés pendant au moins 3 ans. Un rappel vaccinal tout les 3 ans serait suffisant. Cependant, une visite annuelle chez le vétérinaire reste nécessaire pour réaliser un bilan de santé!

QUEL(S) VACCIN(S) POUR MON LAPIN ?

Le lapin est le second NAC pour lequel une vaccination existe. On le vaccine contre le virus de la maladie hémorragique (VHD ou RHD) et contre le virus de la myxomatose. Il s’agit de deux maladies le plus souvent mortelles en l’absence de vaccination. La contamination se fait par contact direct (lapin à lapin) ou indirect (objet ou propriétaire qui a eu un contact avec un lapin malade) avec un lapin infecté et par des insectes piqueurs comme les moustiques. Tous les lapins peuvent donc être contaminés, peut importe leur mode de vie (accès à l’extérieur ou pas).

A savoir : la vaccination n’empêche pas à 100% ces maladies de se développer, la protection est de 90 à 95%. Mais si l’animal vacciné contracte la maladie, les symptômes sont souvent moins forts et le risque de mortalité est largement diminué.

De nombreux vaccins sont disponibles sur le marché français, protégeant contre l’une ou l’autre des maladies ou contre les deux. La durée et le délai d’efficacité et les protocoles vaccinaux varient en fonction du produit utilisé.

Depuis 2010, un nouvelle version du virus de la maladie hémorragique (VHD-2 ou variant 2) est à l’origine de nombreux cas en France et dans le monde, même chez les lapins vaccinés. Heureusement, un nouveau vaccin protégeant contre ce variant est disponible depuis 2015 : le FILAVAC K C+V. Ce vaccin protège contre les deux variants 1 et 2 pendant 12 mois et ne nécessite qu’une injections pour la primovaccination.

Quel protocole vaccinal pour mon lapin ?

Personnellement j’utilise le vaccin NOBIVAC Myxo-RHD car il ne nécessite pas de primo-vaccination et la protection dure 1 an. Je conseille également le FILAVAC K C+V puisque le VHD-2 a été incriminé dans les derniers cas de maladie hémorragique en français.

Ces deux vaccins protègent contre le variant 1 de la maladie hémorragique. Il est légitime de s’interroger sur l’éventuel risque qu’il y a à vacciner deux fois en même temps votre lapin contre le même variant d’une maladie. Bien que certains vétérinaires estiment qu’il n’y ait aucun risque à injecter ces deux vaccins en même temps, il n’y a à ce jour aucune étude pertinente et à grande échelle prouvant l’absence d’interactions et d’effets secondaires entre ces vaccins. Le principe de précaution veut donc qu’il y ait 2 à 3 semaines d’intervalle entre les deux injections. (Voir le billet « Vacciner mon lapin FILAVAC + NOBIVAC ? »)

QUELS RISQUES REPRÉSENTE LA VACCINATION POUR MON ANIMAL ?

Toute administration de médicament peut avoir des effets secondaires. Ces derniers sont listés dans les RCP (Résumé des Caractéristiques du Produit) des produits que vous utilisez. C’est aussi le cas des vaccins. Même si votre vétérinaire ne vous le rappelle pas à chaque fois, il le sait et ne le cachera pas si vous lui posez des questions! Malheureusement, parfois certains effets secondaires non listé dans le RCP du vaccin utilisé peuvent survenir. Il convient alors d’en faire part à votre vétérinaire qui jugera en collaboration avec les organismes de pharmacovigilance si cela doit être mis en lien ou non avec le vaccin. Le vaccin n’est pas forcément responsable et il est parfois difficile d’être sûr qu’il soit impliqué!

Parmi les effets secondaires connus et communs à tous les vaccins, il peut y avoir des réactions locales suite à l’injection avec la formation d’un nodule ferme, d’un œdème ou de dépilations disparaissant spontanément en 2 à 6 semaines. Des symptômes généraux peuvent aussi survenir en fonction du type de vaccin avec l’apparition d’un syndrome fébrile, d’un abattement ou d’anorexie dans les jours suivant l’injection. Dans les cas les plus graves l’animal peut développer une réaction anaphylactique (ou réaction d’hypersensibilité) qui peut être mortelle si elle n’est pas prise en charge rapidement. Dans le cas de la myxomatose, il est possible que des symptômes atténués de la maladie apparaissent quelques jours après la vaccination ou que des myxomes (petits nodules sur la face) apparaissent. Cela tient à la nature du vaccin où le virus est vivant mais atténué.

EST-CE QUE L’ON « SURVACCINE » NOS ANIMAUX ?

C’est une question légitime, est-il utile de faire des rappels aussi fréquents? Mon animal est-il toujours immunisé 1 an après son vaccin?

Lorsque l’on utilise un vaccin, on se fie en premier lieu aux recommandations du RCP du produit utilisé qui indique la fréquence des rappels. Cette fréquence est établie après avoir fait de multiples prises de sang pour évaluer l’évolution de la quantité d’anticorps après l’injection du vaccin. Lorsque l’immunité devient trop faible pour la majeure partie de la population testée c’est qu’il est temps de faire un rappel. Ces études sont fiables quand lorsqu’un vaccin est utilisé pour l’espèce chez qui le vaccin a été testé. Lorsque l’ont utilise le vaccin pour une autre espèce que l’espèce cible (le vaccin de la maladie de Carré chez le furet par exemple) les études telles que celles dont nous avons parlé au début du billet permettent de déterminer la fréquence idéale des rappels.

Cependant toutes ces données sont fondées sur des statistiques, et il faut savoir qu’il peut y avoir des variations individuelles vis-à-vis de la protection vaccinale : un individu peut-être protégé plus ou moins longtemps qu’un autre avec le même vaccin. L’avenir de la médecine préventive repose donc surement sur les tests d’immunité individuelle à réaliser lors des bilans annuels de santé pour vérifier si l’animal doit être revacciné. Il existe déjà des tests rapides chez le chien et le chat pour certaines maladies, bien qu’il n’y ait pas encore beaucoup de recul sur leur utilisation, mais pas pour le lapin et le furet. Affaire à suivre donc…

Quoi qu’il arrive le choix de vacciner vous revient et votre vétérinaire saura vous conseiller au mieux pour votre animal en fonction de son état de santé!

BIBLIOGRAPHIE :

• Arrêté du 10 octobre 2008 relatif aux conditions et modalités de la vaccination antirabique des animaux domestiques
• WAGNER RA, BHARDWAJ N. Serum neutralizing antibody responses to canine distemper virus vaccines in pet ferret (Mustella putorius furo). Jour Ex Pet Med. 2012;21:243-247.
• CAPUCCI L, CAVADINI P, SCHIAVITTO M, LOMBARDI G, LAVAZZA A. Increased pathogenicity in rabbit haemorrhagic disease virus type 2 (RHDV2). Vet Rec. 2017;180(17).
• RCP du FILAVAC VHD K C+V SUSPENSION INJECTABLE POUR LAPINS
• RCP du NOBIVAC Myxo-RHD, lyophilisat et solvant pour suspension injectable pour lapins

Vacciner mon lapin FILAVAC + NOBIVAC ?

Pour rappel, les deux principaux vaccins utilisés chez le lapin sont :

• Le vaccin NOBIVAC Myxo-RHD, qui protège contre la myxomatose et le VHD 1 (VHD C), le virus classique ou ancien variant de la maladie hémorragique. C’est un vaccin sous-unité, exprimant une protéine de virulence du VHD1.
• Le vaccin FILAVAC VHD K C+V , qui protège contre le VHD1 et le VHD2 ou VHD nouveau variant. C’est un vaccin inactivé.

Ainsi, injecter les 2 vaccins en même temps revient à injecter 2 fois une protection contre le VHD1. Il est légitime de se demander si cela peut être dangereux pour le lapin. Bien que le principe de vaccination du FILAVAC et du NOBIVAC soient différents, les recommandations d’utilisation étaient de laisser entre 15 jours et 3 semaines minimum entre les 2 vaccins.

Cependant, certains vétérinaires affirment maintenant que les 2 injections NOBIVAC + FILAVAC peuvent être pratiquées en même temps. En effet, une récente étude présentée en congrès aux Pays-Bas fin 2017 a été citée pour affirmer que cela serait sans danger. Dans cette étude, 24 lapins répartis en 4 groupes de 6 lapins ont reçu respectivement :

• 0 vaccin,
• 1 vaccin FILAVAC,
• 1 vaccin NOBIVAC,
• 2 vaccins FILAVAC + NOBIVAC.

Le résultat ne montre aucun effet secondaire pour ces derniers. Cette étude ne regroupe donc que 6 lapins ayant reçu les 2 vaccins en même temps sans effets secondaires, ce qui est largement insuffisant pour conclure à un protocole vaccinal en une seule injection !

La réponse à notre question est donc :

Rappelons que les dossiers d’autorisation de mise sur le marché des médicaments réclament plus de 10 ans d’études sur un grand nombre d’animaux, et malgré cela, des effets secondaires peuvent être détectés a posteriori. C’est ce qu’on appelle la pharmacovigilance. Les statistiques aident à déterminer combien d’animaux doivent être étudiés pour que les résultats puissent être considérés comme fiables pour la réelle population de lapin (échantillon représentatif).

Aucune des 2 notices vaccinales FILAVAC ou NOBIVAC ne comprend d’ailleurs de conclusion sur cette question. Bien qu’intéressante, il faudrait élargir l’étude menée afin de pouvoir conclure à une absence de danger pour vos lapins.

Vaccinations for Rabbits

Introduction

There are three vaccines licensed for use in rabbits available in the UK:

• two for Viral Haemorrhagic Disease (VHD): Cylap® (Fort Dodge Animal Health) and Lapinject VHD® (Ceva Animal Health Limited)
• one for myxomatosis: NobivacTM Myxo (Intervet UK Ltd)

In young rabbits, maternal antibodies are said to start to disappear progressively between the 4th and 7th week of life.

VHD Vaccination

Vaccination against VHD is achieved by use of the oil-adjuvanted inactivated viral vaccines, Cylap® (Fort Dodge Animal Health) and Lapinject VHD® (Ceva Animal Health Limited), whereas myxomatosis is controlled by use of a heterologous live Shope fibroma virus NobivacTM Myxo (Intervet UK Ltd). Studies with Lapinject VHD ® have shown that vaccinating at 5 weeks of age stimulates the immune system, with antibody response being maximal 2-5 weeks after vaccination and field protection in 6-8 days and the product is licensed to be given from 5 weeks of age.

Cylap is available in single-dose and in 10-dose vials; Lapinject VHD in only 5-dose vials. Once a multiple-dose vial is broached, it must be used within eight hours and then discarded. Lapinject VHD is priced competitively to avoid waste. Both VHD vaccines are oil-adjuvanted so accidental self-injection requires prompt medical attention with surgical incision and irrigation of the area – see the Data Sheets.

Development of clinical signs of VHD is dependent on the presence of transaminases in the liver of the animal and these do not appear until 2 months of age. Vaccination should be started as soon as possible so that immunity is achieved prior to the appearance of these (« disease-enhancing ») enzymes. Annual boosters are required for both of the VHD products. VHD vaccines are safe to use in pregnant animals but Nobivac Myxo should not be used in pregnant or animals intended for breeding.

Myxomatosis Vaccination

Nobivac Myxo, being Shope Fibroma Virus, is obviously not homologous and timing of its use is critical. The vaccine should be administered at the time of maximum exposure and this varies seasonally with the time of emergence of the arthropod vector (usually mosquitoes). Duration of immunity is given on the Data Sheet as six months, not as long as with homologous vaccines, so the vaccine is usually administered twice yearly, in May and September but this may have to be varied with changes in climate and the reasons for your protocol should be adequately discussed and explained with the owner in advance (See the Data Sheet).

All of these products are administered subcutaneously but 10% of the Nobivac Myxo dose is administered intradermally. The procedure on the company’s data sheet for intradermal technique is technically challenging! The Cylap and Nobivac Myxo Data Sheets state that the vaccine should not be administered simultaneously with other vaccines so an interval of 14 days is usually allowed between the use of myxomatosis and VHD vaccines.

Rabbits: VHD outbreak in Kidderminster

We have recently been notified of an outbreak of suspected Rabbit Viral Haemorrhagic Disease in Kidderminster. Our sympathies are with the owners of any rabbits suffering this terrible, fatal disease, and it is worth reminding owners what steps they should take to avoid infection.
Vaccination is vital, even for totally indoor rabbits. The new combined Nobivac Myxo-RHD is now widely available, and also protects against myxomatosis. Sole vaccines against VHD are also available (Lapinject, Cylap and Anivac). Whichever vaccine you opt for depends on a discussion between you and your veterinary surgeon, but is is worth pointing out that as the weather warms up shortly, myxomatosis also becomes a risk.
The reason vaccination is vital even for indoor rabbits is that the virus is highly persistant in the environment, and may live for up to 200 days outside of the host animal, especially at low temperatures, as we currently have. This also allows it to travel on inanimate objects, such as shoes and clothing, car tyres, and also the feet of other pets. So it is possible to bring it back following walks through fields containing infected rabbits, or when visiting friends rabbits or sharing equipment, bedding, housing etc.
As a result, a pet safe, ant-viral disinfectant should be used, at a suitable dilution rate, in contact with surfaces for the length of time as specified by the manufacturer. It is no use simply applying disinfectant to dirty items, they must be cleaned thoroughly first, to allow the disinfectant to touch the surfaces properly. Foot dips might be useful, and should be changed regularly to avoid contamination with mud etc if used to clean dirty boots.
Speak to your vet about a suitable disinfectant, but brands including Virkon, F10, Ark Klens, are effective, when used as above. If you have any further questions or comments, don’t hesitate to get in touch.

Rabbit haemorrhagic disease and its variants (Lagoviruses)

Page last updated August 23rd 2018

Terminology

In 1984, a highly lethal disease broke out in rabbits in China. The disease was characterised by haemorrhages around the body and a calicivirus was identified as the cause. The disease was named ‘viral haemorrhagic disease’ (VHD) or ‘rabbit haemorrhagic disease’ (RHD) and the latter name has become the standard term in recent years. The acronym RHDV (‘rabbit haemorrhagic disease virus’) is used to describe the virus. Since the emergence of RHD, many variants of the virus have emerged that have been named (e.g. RHDV-K5, RHDV1 and RHDVb). Non-pathogenic strains of the calicivirus (RCV or ‘rabbit calicivirus’) have also been discovered. Recently, a variant (RHDV2) has appeared that differs from the original strain (RHDV1). The term ‘lagovirus’ encompasses all types of RHDV and its variants.

History of the infection

RHD was first identified in 1984 in the People’s Republic of China. It appeared to originate from a colony of Angora rabbits that were imported from Germany. Within a year, there was a loss of over 140 million rabbits and the disease was spread to Korea by rabbit fur (Abrantes et al, 2012). RHD was diagnosed in Italy in 1986 and by 1988, the disease been reported throughout Europe and in many other countries worldwide where it was probably introduced through rabbit meat. The disease spread into the wild rabbit population and in 1990, RHD reached Scandinavia where wild rabbits in the densely populated island of Gotland became nearly extinct within 1 week (Gavier-Widén, 1996). Hundreds of rabbits were seen dead in the fields and many more died in their burrows. In 1997, in Australia, RHD was released onto Wardang Island as a means of biological control of the wild rabbit population. Infection spread to the mainland where it has killed millions of wild rabbits. The infection was also surreptitiously introduced into New Zealand. The first confirmed case of RHD in the United States occurred in 2000 in a small breeding colony of exhibition rabbits in Iowa. Twenty five of the 27 rabbits died with no indication of the source of the infection (Percy and Barthold, 2008).

Variants of RHD

The virus that causes RHD is a calicivirus. Caliciviruses readily mutate. RHDV1 is a positive-sense, single-stranded RNA virus and the complete genomic sequence has been determined. It does not grow in tissue culture, which limits research. Several variants of RHD exist.

RHDV1

RHDV1 is the original strain of RHD. Most of the information that is known about the virus that causes RHD relates to this strain. In the UK, this strain seems to have died out and been replaced by RHDV2.

Non-pathogenic rabbit calicivirus (RCV)

Although fatalities from RHD were first reported in 1994, antibodies to the virus were detected in sera collected before that time and it is believed that non-pathogenic strains (RCV) could have been responsible for protecting rabbits by stimulating antibody production. In 1996, a non-pathogenic calicivirus was recovered from breeding rabbits in Italy that produced seroconversion and was found to protect rabbits against RHD. Subsequent investigations in Australia and UK have also revealed the presence of non-pathogenic strains that may or may not confer some natural immunity. Studies in Australia suggest that rabbits that live in areas of higher rainfall are more likely to be infected with RCV and therefore have some immunity to RHD (Liu et al.,2014).

New variant (RHDV2)

In 2010, an atypical outbreak of RHD occurred in a rabbitry in France in which 25% of the rabbits (that were vaccinated) died (Le Call-Reculé, 2013). Emergency vaccination appeared to stop the mortalities but in 7-15 days, compared with the usual 7-9 days. Similar outbreaks in wild rabbits with high mortality were also occurring. Samples from affected rabbits were analysed genetically and the virus that was causing the fatalities was found to be related to, but highly distinct from, the strains of RHD that were isolated from previous outbreaks. This variant is known as RHDV2. This new variant was identified in Italy in 2011 and in UK in 2013 although retrospective analysis of samples suggests that the infection has been in the British Isles since 2010. (Westcott and Choudhury, 2015). The infection has the potential to cause devastating effects on the wild rabbit population because it affects all ages. Unlike the original strain of RHD, rabbits under 4 weeks of age have no natural immunity to RHDV2. It also appears to affect hares.

RHDV-K5

RHDV-K5 is a variant of RHD that is more lethal than RHDV1 and appears to have less cross-immunity with non-pathogenic strains. It has been deliberately released in Australia to kill wild rabbits. Vaccination against RHDV1 protects pet rabbits from this disease

Differences between RHDV1 and RHDV2

A feature of RHDV1 is that baby rabbits can have a natural immunity, which is not maternally derived. Most rabbits under 4 weeks of age remain unaffected by RHDV1 and develop a life-long immunity if they are exposed to the disease. Unexposed rabbits become increasingly susceptible until 6–10 weeks of age when physiological resistance to the virus disappears. This age resistance is an interesting feature of the disease and appears to be due to a rapid and effective inflammatory response by the liver, with a sustained elevation in local and systemic B macrophages and T lymphocytes (Marques, 2012). Subsequent exposure to the virus boosts immunity that protects these young rabbits when they reach adulthood (Ferreira, 2008). This age immunity and background infections with non-pathogenic strains of RHD could explain the decline in RHDV1 as the main cause of rabbit haemorrhagic disease. RHDV1 only affects European rabbits (Oryctolagus cuniculus). It does not affect other lagomorphs, such as cottontails, or other small mammals such as chinchillas, guinea pigs, rats and mice.

Age immunity does not occur with RHDV2. Young and suckling rabbits may be affected. The variant can also affect hares.

Transmission of RHD virus

RHDV is difficult to kill and can survive harsh environmental conditions. It can survive temperatures of 50 ο C for up to an hour and is not inactivated by freezing. The virus can survive in the environment for many months (Henning et al, 2005) and carcases of dead rabbits can be a source of infection by spreading the virus via the faeces of scavengers, such as foxes or crows. Biting insects may mechanically transmit the virus in viraemic blood from one animal to another. Fleas, blowflies and mosquitoes are known to spread the disease. Fly ‘spots’ (faeces) are infective and can contaminate pasture (Asgari et al, 1998). Hay from contaminated pasture could be a source of infection. Cultivated vegetables may also be contaminated. Flies can travel long distances and be carried along by the wind and spread the disease far and wide. Only a few virus particles are needed to infect a rabbit.

Infection is also easily transmitted between infected rabbits by the oral, nasal or conjunctival routes. Food bowls and bedding can transmit infection.

It is believed that rabbits that have recovered from RHDV1 are potentially infectious to other rabbits. The role of carriers is unknown. A laboratory study showed that the viral DNA could be recovered after 15 weeks in vaccinated rabbits that were exposed to infection (Gall and Schirrmeier, 2006) but subsequent attempts to show that the viral RNA was infective failed to transmit infection (Gall et al, 2007). The carrier status for RHDV2 is still unclear.

Vaccines against RHDV

Due to the devastating effects of RHD in China, a vaccine was quickly developed from inactivated virus obtained from the liver and spleen of infected rabbits. Although the immunological response to inactivated vaccines (Cylap, Lapinject) was good, in the UK, they have been superseded by a bivalent vaccine that protects against both myxomatosis and RHD (Nobivac Myxo-RHD). It is constructed from a laboratory-attenuated strain of myxoma virus and the capsid protein gene of RHDV. The vaccine is not protective against RHDV2 so rabbits that are vaccinated with Nobivac Myxo-RHD can still die from RHD. Vaccines against RHDV2 have been developed in countries where rabbit meat is popular and are now available in the UK. Filovac is the vaccine that is most commonly used in the UK. Eravac is also available.

Clinical signs of RHD

RHD has a short incubation period of 1–4 days. The virus replicates in many tissues, including the lung, liver and spleen with subsequent viraemia and haemorrhage. The RHD calicivirus has a predilection for hepatocytes and replicates within the cytoplasm of these cells and causing an acute necrotising hepatitis. Disseminated intravascular coagulation ensues and can produce fibrinous thrombi within small blood vessels in most organs, notably the lungs, heart and kidneys resulting in haemorrhages. Death is due to disseminated intravascular coagulopathy or to liver failure.

Three manifestations of the infection may be seen:

1. Peracute with animals found dead within a few hours of eating and behaving normally. This is the most common presentation.
2. Acute with affected rabbits showing lethargy, pyrexia (>40οC) with an increased respiratory rate. These animals usually die within 12h. Hypoglycaemia and a drop in haematocrit and total protein are features of the disease. Blood samples may also show leucopaenia, thrombocytopaenia, fibrin thrombi and markedly raised liver enzymes but a feature of the disease is a dramatic drop in blood pressure that makes it difficult to find a vein to take blood samples or set up intravenous fluids. Dying rabbits are pallid, shocked and collapsed. Haematuria, haemorrhagic vaginal discharges or foamy exudate from the nostrils may be seen. Vascular infarcts can occur within the brain and occasionally convulsions or other neurological signs are seen just before death. The ‘classic’ picture is a dead rabbit in opisthotonus with a haemorrhagic nasal discharge but this is not seen in every case. Rarely, a rabbit may recover from the acute phase, only to develop jaundice and die a few days later. Very occasionally, a rabbit can survive this period but with permanent liver damage.
3. Subacute with rabbits showing mild or subclinical signs from which they recover and become immune to further RHDV. This stage of the disease is difficult to diagnose with certainty. Clinical siigns of liver disease are vague and non-specific.

Clinical signs of RHDV2

The clinical signs of RHDV2 are the same as RHDV1 although experimental infections suggest a lower mortality rate. Clinical signs develop after 3-9 days instead of 3-4 days with experimental RHDV infection (Le Call-Reculé, 2013). Subacute or chronic infections are more frequent so more rabbits can survive. RHDV2 is more likely to cause a protracted disease with weight loss and jaundice. However, there is evidence that RHDV2 is becoming more virulent (Capucci et al, 2017).

Anecdotally, outbreaks in groups of pet rabbits can show sporadic deaths, with companion rabbits that survive with no obvious clinical signs. Sometimes other underlying diseases suddenly flare up (e.g.rhinitis or treponematosis) in a short period of time. This can complicate the diagnosis.

Diagnosis

The diagnosis of RHD is usually made at post mortem examination. RHD is suspected in any sudden death especially if more than one rabbit in the household has died. The post-mortem picture may be of a healthy rabbit with non-impacted food in the stomach and hard faecal pellets in the distal colon, suggesting that death was sudden.

Gross post-mortem signs may be minimal or obvious. Suggestive findings include:

• An enlarged pale, friable liver with a distinct lobular pattern. The liver is always affected, although the gross appearance may not reflect the severe histopathological changes.
• An enlarged spleen. This is highly suggestive of RHD. There are few differential diagnoses
• A trachea filled with foamy exudate that may or may not be blood stained
• Haemorrhages in any part of the body may or may not be obvious. Free blood may be found in the abdomen or in the retroperitoneal spaces. Ecchymotic haemorrhages may be seen on the serosal surfaces or in the lungs. Petechiae may be seen in the muscles, including the heart.

Histopathology confirms acute hepatic necrosis. There may be many other changes such as pulmonary oedema, acute nephropathy or alveolar haemorrhage. Necrosis of lymphocytes in the splenic follicles and lymph nodes are typical findings. Fibrin thrombi may or may not be present in the small vessels of multiple organs, including kidney, brain, adrenals, heart, testes and lung. Erythrophagocytosis may be evident in the spleen. Apoptosis (extensive vacuolations, alterations in the mitochondrial structure, kryopyknosis and karoylysis) may be seen on electron microscopy.

Confirmation of the diagnosis is made by PCR testing. Although the clinical history and typical histopathological changes in the liver and/or spleen may be highly suggestive of RHDV infection, PCR testing confirms the diagnosis and determines the variant. Fresh or frozen liver is required by the laboratory. PCR testing on other samples, such as blood or faeces can give false negative results.

Treatment

There is no specific treatment for affected rabbits. The majority of them will die quickly. Generalised supportive care (fluid therapy, syringe feeding, warmth etc.) is indicated for rabbits that survive but it must be borne in mind that these rabbits can be infectious to others. Barrier nursing is required.

Current vaccination advice

Despite its name, Nobivac Myxo-RHD is not protective against RHD. It only vaccinates rabbits against RHDV1, not RHDV2, which is the virus that is causing the current outbreak of RHD in the UK at the present time.

Vaccination with the bivalent vaccine (i.e. against RHDV and RHDV2) offers the best protection against RHD. Vaccines have been developed to protect meat rabbits in other parts of Europe that are now available in UK. Filavac and Eravac are the brands that are licensed for use in the UK. Although they are available in multidose vials for vaccinating large numbers of rabbits, single dose vials suitable for vaccinating individual pet rabbits are also available

Although Filavac (and other RHDV2 vaccines) only offer protection against RHDV1 and RHDV2. They do not protect rabbits against myxomatosis so separate vaccinations against both diseases are be needed. At present (Agust 2018), Nobivac Myxo-RHD is the only vaccine that is available against myxomatosis so both Nobivac Myxo-RHD and Filavac (or Eravac) are required to protect pet rabbits against myxomatosis, RHDV1 and RHDV2. It is recommended that both Nobivac Myxo-RHD and Filavac are given annually. Eravac requires a booster after 9 months.

Owners may voice concerns about over vaccinating against RHDV1. At the present time, there is no alternative if rabbits are to be protected against RHD and myxomatosis. There is no evidence that it is a problem

Early vaccination at 4 weeks of age with Filavac is possible but the recommendation is to revaccinate at 10 weeks and then 12 months later. Eravac can be given from 30 days of age.

Source of RHDV in outbreaks in domestic rabbits

It is believed that RHDV2 was originally introduced into the British Isles from exhibition rabbits from Europe that came to rabbit shows in the UK (Westcott, personal communication). The source of new outbreaks and the spread of RHVD2 in pet rabbits are unclear. Infection may spread between rabbits at shows and by introducing a new rabbit from a breeder into a pet shop or rescue centre can introduce infection that may be spread further when the rabbit and its contacts are rehomed. Wild rabbits can act as a reservoir of infection. They may transmit infection directly by visiting a garden that is inhabited by pet rabbits. Or humans that walk in areas inhabited by wild rabbits may bring infection home on their feet. Insects and scavengers, such as foxes and crows, can spread the disease by feeding on a wild rabbit carcase and defaecating in areas where pet rabbits live or where their owners walk. Hay, grass, vegetables or wild plants may be contaminated. Visiting places where there are other rabbits, or people that have contact with them, increases the risk of infection. The results of a survey that is currently underway in order to gather and share information about RHDV outbreaks in domestic rabbits has found that many rabbits (or their owners) had visited a vet within the fortnight before their rabbit’s death..

Lockdown

Once an outbreak has taken place in a place where there are rabbits, it can be difficult to know what to do. There is insufficient information at the present time to offer proven advice. Lockdown of infected premises is the most responsible way forward. The carrier status of surviving rabbits is unknown and it is probably impossible to eliminate cross infection in an infected premises. Any surviving rabbits have already been exposed by the time a death occurs. It seems sensible that rabbits are not taken to shows, sold or rehomed. Ideally, no rabbits should go in or out of the premises and owners should take care not to spread infection. Separate clothing, especially footwear for dealing with the rabbits and going out is recommended.

It is hard to know how long lockdown should continue. Four months from the date of the last death is recommended. Vaccination of surviving stock and a temporary halt in breeding programmes may be necessary for breeders to eliminate infection.

Disinfection

Any virucidal disinfectant that is effective againist feline calicivirus should be effective againist RHD. It should be used according to the manufacturers guidelines. Virkon (Vetoquinol) at a dilution of 2% is recommended. The manufacturers say that mixing 2 tablets in 500mls in a spray bottle and spraying the underside of shoes is more effective than a footbath.

Veterinary premises

As with any disease, veterinary premises are a potential source of infection. They are where ill rabbits are brought for treatment and infected rabbits may be hospitalised. Ideally, all rabbits that are admitted for any type of treatment should be vaccinated against RHD, including RHDV2. Careful disinfection and vigilance to prevent cross infection are needed.

Transmission from wild rabbits

There is also a risk of spreading RHDV2 into pet rabbits from outbreaks in wild rabbits. Recently, there has been a resurgence in popularity in picking wild plants to feed to pet rabbits (foraging) but many owners worry about introducing infection. Theoretically, wild plants could be a source of RHDV2 but this has not been demonstrated. Wild rabbits tend to graze locally and keep the plants short. Selecting tall plants from areas where rabbits do not graze is always a good option when foraging. There is also the possibility of introducing infection from other sources, such as flying insects or on footwear. Even hay could be a source of infection as it could be contaminated by urine, faeces or tissues of rabbits were hiding in the hay before they died of VHD. Foraging has so many health benefits that it seems wise to continue for vaccinated rabbits but not for unvaccinated ones.

It is possible that exposure to lagoviruses from the wild rabbit population is advantageous for a healthy, vaccinated pet rabbit. The rabbit may develop a stronger immunity if it is challenged. Not all lagoviruses are pathogenic so natural exposure could be protective. The situation is not clear and more information should come to light over the next few months or years.

Les vaccins ont été faits. C’est le rappel du vaccin nobivac myxo-rhd.
L’année dernière les deux loustics avaient eu de nombreuses réactions vaccinales, on surveille donc de près les oreilles de Linette et l’entrejambe de Malou.
Je refais un point sur le vaccin Nobivac myxo-rhd et ses effets secondaires car on me pose beaucoup de questions à ce sujet. Tout d’abord au sujet de la primo vaccination et du rappel :
– Lapin déjà vacciné myxo-VHD : 1 injection de Nobivac tous les ans
– Lapin déjà vacciné VHD seulement : 1 injection de Nobivac tous les ans
– Lapin n’ayant jamais été vacciné : 1 injection de Nobivac tous les ans
– Lapin ayant été vacciné contre la myxo seulement : 2 injections à un mois d’intervale de Nobivac puis 1 injection de Nobivac tous les ans Ensuite au sujet des réactions observées sur les lapins de compagnie vaccinés ces dernières semaines.
Deux types de réaction ont été régulièrement observés sur les lapins vaccinés:
1/ des myxomes situés au point d’injection mais aussi aux yeux, aux oreilles, à l’entrejambe
2/ des croûtes brun/doré/orangé situés principalement à l’intérieur du pavillon des oreilles Ceci a été constaté par les vétérinaires de tous les pays concernés par cette vaccination.
Plus rarement, on a constaté des anorexies passagères, de la fatigue ou de la fièvre.
Toutes ces réactions sont sans danger.
Dans de très rares cas, il y a eu des complications au niveau des myxomes qui se sont infectés. L’explication la plus plausible est que ces lapins aient été en contact avec le virus sauvage de la myxo avant/pendant ou peu après la vaccination ce qui a amplifié la réaction. Ceci reste une réaction vaccinale et n’est en aucun cas une myxomatose.