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Happy Monday Everyone!
I’m not the best with social media content; I’m not savvy with the apps and so it puts me off posting a lot of the time. I endeavour to improve because there’s so much I want to say and spread information (evidence based information!) about exotic animals to both pet guardians and to other vets. I have so much passion for those animals who are often overlooked and misunderstood. As a veterinary community we often fall short in protecting these animals, not intentionally but due to the overwhelming amounts of knowledge required regarding the different species. It is impossible to be an expert on each species and we shouldn’t be expected to be. This means though, that there is a need for dedicated exotic veterinarians to be readily available to people to seek appropriate care for their fur babies.
Even within the exotic veterinary community there is a difference in experience and qualifications. There are vets, like myself, who are embarking upon their exotic veterinary career, in the middle of further qualifications but not yet a specialist. A true specialist has passed either European or American speciality examinations which are the highest qualification within the veterinary field in that area. It is important these distinctions are made and that pet guardians are aware of who is caring for their animal. Trust and transparency is so fundamental to a vet and a pet guardian.
This week’s topic is relating to vaccinations. I still see dogs and cats and unfortunately cared for a little puppy who was suffering from parvovirus. It got me thinking that the majority of people are unaware of the diseases we are vaccinating against, and I for one am poor at explaining the various diseases to people during consultations. It seems pointless explaining the various diseases when we are vaccinating against them but then how can we expect people to be motivated to complete the vaccination course and boosters?
Not many companion exotic animals require vaccinations. Rabbits are the most commonly vaccinated animal after dogs and cats. They are vaccinated against both myxomatosis and RHD-1 and RHD-2. These diseases are most often fatal, yearly boosters are required to maintain immunity.
Myxomatosis
Myxomatosis is a pox virus called the myxoma virus. It is found naturally in tapeti in Central and South America and brush rabbits in North America. In the above species the virus causes mild symptoms but in European rabbits it is usually fatal. The virus was introduced to Europe and Australia in an attempt to control the wild rabbit population.
Classic signs of myxomatosis include:
Swelling of the eyes and the genitals (Fig.1)
White milky ocular discharge
Fever
Lethargy
Anorexia
Figure 1. Swelling of the eyelids (Harcourt-Brown, 2000)
In highly virulent (more lethal) strain death often occurs on day 5 with only conjunctivitis as the sign. In less virulent strains rabbits often develop scabs on the body and can survive with nursing care. The latter is true also in previously vaccinated rabbits, the disease is often milder. Rabbits often suffer with respiratory disease as a consequence of myxomatosis and can die as a result of a secondary bacterial pneumonia. If the rabbit survives chronic (long lasting) respiratory disease is common.
Diagnosis is usually made by the classic signs but there are tests that can be performed (see below). There is no treatment for myxomatosis, aggressive supportive care is required but often euthanasia is recommended due to suffering.
Info for vets
The myxoma virus is a large double stranded DNA virus which relocated in the cytoplasm of the cell. Transmission is often via insects such as mosquitos, fleas or mites but can be by direct contact to another infected rabbit. The virus is shed in both ocular, nasal and genital discharge and can persist on formites. While stable in the environment the virus is sensitive to disinfectants.
Clinical presentation varies based on signalment of the rabbit, site of inoculation and virulence of the strain. According to Meredith (2013), the typical time course of the disease is as follows:
Days after infection | Clinical signs |
2–4 | Swelling at site of infection |
4 | Fever |
6 | Swelling of eyelids, face, base of ears, and anogenital area |
6 | Secondary skin lesions, including red pinpoint lesions on eyelids and raised masses on body |
6–8 | Clear ocular and nasal discharge that becomes mucopurulent and crusting |
Respiratory distress | |
8–9 | Hypothermia |
10 | Complete closure of eyelids due to swelling |
10–12 | Death |
Diagnosis can be by PCR or real-time PCR on swabs taken from lesions. Histopathology, electron microscopy or virus isolation are other alternate diagnostic tests.
The vaccination is a modified live vaccine by attenuating the myxoma virus or by Shope fibroma virus which can provide cross immunity. It is licensed from rabbits aged 5 weeks old and the onset of immunity starts 3 weeks later.
Rabbit Hemorrhagic Disease
Rabbit hemorrhagic disease (RHD, also known as viral hemorrhagic disease) is a calicivirus with a mortality rate between 70-100%. There are two types of the virus (RHD-1 and RHD-2) and both of these cause serious disease.
The virus is transmitted by direct contact and can persist in the environment for 2 months. This means bedding, food, equipment of infected pet rabbits need to be decontaminated or destroyed appropriately. Flying insects such as mosquitoes and fleas can spread the virus between rabbits.
Clinical signs of RHD varies:
Sudden death
Fever (42 degrees)
Bloody discharge (nose, genitals, mouth)
Coma
Convulsions
Death
RHD-2 causes milder disease: anorexia, lethargy, weight loss, jaundice (yellow skin). Death occurs due to liver failure.
Diagnosis is similar to myxomatosis and based on clinical signs.
Info for vets
Caliciviruses are highly resistant in the environment. They can withstand freezing and persist in meat for months.
The virus targets the liver and replicates here. This leads to profound hepatocyte death causing DIC, hepatic encephalopathy and necrosis, the latter being the hallmark of a post mortem diagnosis. Bleeding is a common symptom due to the depletion of clotting factors and platelets.
Clinical pathology:
Haematology: leucopaenia, thrombocytopaenia
Biochemistry: elevated liver enzymes, decreased glucose and cholesterol
Increased PT and APPT times are common
Urinalysis: proteinuria, bilirubinuria and high urinary GGT
RHD-1
Young rabbits are not likely to be affected, rabbits less than 4 weeks old cannot become ill. Those between 6-8 weeks are unlikely to become infected.
RHD-2
Rabbits as young as 15 days old have died due to the disease
Not all rabbits succumb to the disease. Asymptomatic carriers can exist and surviving rabbits develop a strong immunity to the virus.
A live recombinant vaccination is available in the UK and protects against myxomatosis and both RHD-1 and RHD-2.
So, long story short, vaccinate your rabbits! Even indoor rabbits are at risk so don’t delay.
Ferrets can also be vaccinated against two viruses: distemper virus and rabies. Thankfully in the UK these two viruses are not common/ present but it is still important for ferret carers to be aware of the risks. These viruses (particularly distemper) will be discussed in the next blog.
I will try to cover an interesting pertinent topic weekly which is useful to both pet carers and vets. Real cases will be sprinkled in sporadically too so watch this space!
In memory of little Bean who we couldn’t save but hope experienced a home and love for a short while 🐾 🐶
References:
Harcourt-Brown, F. (2000) Myxomatosis. Available at: https://www.harcourt-brown.co.uk/articles/infectious-disease/myxomatosis (Accessed: 08 July 2024).
Meredith, A.L. (2013) ‘Viral skin diseases of the rabbit’, Veterinary Clinics of North America: Exotic Animal Practice, 16(3), pp. 705–714. doi:10.1016/j.cvex.2013.05.010.
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