Answering some questions about Myxomatosis and the new combined vaccine
Author: The Rabbit Welfare Fund
RWAF logo1 – How do pet rabbits get myxi?
The most likely source of infection for pet rabbits is via biting insects and other arthropods, mainly fleas, but also flying biting insects such as mosquitoes, transmitting the virus via their mouthparts, from local wild or domestic infected rabbits. Also possible, if wild rabbits have access to the garden, or can get close, eg through a mesh fence or run, is direct infection from rabbit to rabbit via respiratory tract secretions. Of course, once one rabbit in a group is infected, this route is also a worry with regard to the infection of the other rabbits (see later)
2 – What is the incubation period? (How long from one going down with it to keep fingers crossed until the rest are clear?)
The incubation is variable, depending on the route of infection and thus the site of disease. Skin lesions (from biting insects) may be seen from as early as 4 days, becoming very definitely noticeable by 10-14 days. One can expect by that point, that the eyelids will be noticeably swollen, and if biting insects are the route of infection, one is probably out of danger of infection at that point, as long as no infection been introduced after the suspected date of the initial case.
Lung infection can be seen in group housed rabbits, where aerosol spread into the environment, leading to inhalation, and subsequent pneumonia, may not be noted until up to 20 days after infection. This is much less common than the typical skin, face and eyelid swellings that are so familiar.
3 – If one rabbit in a pair or group gets it, will the rest?
Not necessarily, especially if they are rapidly separated, or steps are taken to reduce insect spread. Individual immunity obviously varies, otherwise all wild rabbits would have succumbed to it and died by now. Previous infection or vaccination will help afford immunity, but immunity is not long-lived, and not absolute. Different rabbits will have different health statuses, and be more or less susceptible. However, given the highly infectious nature of the disease, and the generally poor level of immunity present, the likelihood of infection of all in contacts is highly likely.
4 – Should infected rabbits be pets?
This depends on the virulence of the strain, the form of the disease, and the immunity of the rabbit. If the lesions are dry and nodular, and quite discrete, this cutaneous myxomatosis carries a good prognosis, and I would definitely not put such rabbits to sleep. If there is generalised disease, with swelling of the head, including ears and eyelids, and genitals, with or without lung involvement, then the outlook is far worse. If these rabbits have been vaccinated, they have a better chance of survival. Treatment with antibiotics (for secondary pasteurellosis and other bacteria), anti-inflammatories, nebulisation and drugs to improve respiratory function (to help breathing), nutrition, fluid therapy, and raised environmental temperatures (to 85 F / 29.5C), may effect a cure in a small number of cases, but this has to be weighed against the distressing and uncomfortable nature of the disease, and the welfare problems if a decision is made to treat. It is a horrible way to die, and extremely unpleasant for anyone watching it.
5 – If one rabbit in a pair or group gets it, should it be isolated straight away?
If a decision is made to treat one rabbit, then really I think it needs to be isolated from the others. Whilst that doubtless adds to that rabbit’s stress (and that of the healthy rabbits), the risks of infecting the others are significant, even if diligent insect vector removal is performed.
Treating ideally involves raising the ambient temperature to 85F / 29.5C for the infected rabbit, and that is not comfortable for healthy rabbits.
6 – Should the remaining partner, or group members also be isolated from other rabbits in case they are incubating the disease and able to transfer it to rabbits in the next run / enclosure? (either by direct contact or close proximity for mechanical vectors)
Ideally, yes. If all were infected at the same time, and one or more have lesions, the others may simply be a few days behind, and therefore potentially infective soon. They should all be treated for fleas, and placed in a separate airspace to definitely infected, and definitely unexposed rabbits.
7 – How can we prevent myxi in the first place:
Vaccination is the mainstay of preventative healthcare. Regular vaccination, either every 6 months, via the intradermal and subcutaneous routes, using Nobivac Myxo, or every year, by the subcutaneous route alone, with Nobivac Myxo-RHD, is advised.
Xeno or Advantage Spot On and Rearguard 2 days apart?
Insect control is vital. Rearguard DOES NOT prevent, kill nor deter fleas.
Permethrin based products eg Xenex spot on, repel and kill biting insects and fleas. This has the advantage of preventing them from biting and spreading myxomatosis
Advantage does not need the flea to bite, to take up the active ingredient and die, but it may take up to 12 hours to kill fleas, which obviously permits them time to attach and spread myxomatosis.
Environmental control, using insecticides, insect repellents, and physical barriers eg fine mesh on windows and doors, mosquito netting etc is helpful, especially at times of the day when they are active eg dusk.
Preventing other domestic pets from bringing either wild rabbits, or fleas from wild rabbits, into the home or garden, is important. Rabbit fleas may be carried by dogs and cats, after they have hunted wild rabbits. They typically line up on the edge of the ears. Domestic pets should be examined, treated, and not allowed near rabbits until it’s certain that there are no fleas present.
8 – How do I need to clean the environment (shed / hutch / paving / grass) before reintroducing rabbits to an area that had an infected rabbit in it?
Inside fleas it can survive for up to about 4 months, and the survival times in the wider environment are very much less than that, although to be sure, obtaining new rabbits within that length of time is unwise, and although stringent flea control and disinfection should be sufficient to minimise the risk, new infections are still possible from fleas and flying insects that gain access, so ongoing control is vital.
9 – If my rabbit has had myxi will they be immune? Should I still vaccinate (cover the vhd risk)
This is controversial, and it’s difficult to give firm advice here. I would prefer to err on the side of caution. Some references suggest lifelong immunity following recovery from natural infection, and others suggest absolute immunity for several months. Without performing antibody testing, it is best to assume that all animals are susceptible, and I would recommend vaccinating with both myxomatosis and RHD vaccines to afford the highest level of protection against both. The Myxo-RHD vaccine carries warnings to the effect that in rabbits with existing immunity to myxomatasis, there may not be a good level of post-vaccination RHD immunity. In such cases, a single RHD vaccine may be given 2 weeks after the combined vaccine.