Hayley de Ronde of Black Foxes UK, posted this as a comment on my Adenovirus post and, sadly, most people ignore comments. I think this adds far more to the subject and deserves a separate post. My thanks to Hayley.
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Historically, fox encephalitis been considered "a common disease of the silver or red fox in captivity" and is readily transmissible between foxes, dogs and other similar animals. Although the agent of the disease was unknown at the time of it's discovery, there was an understanding of a link between fox encephalitis and both distemper and the hepatitis virus'.
The fox encephalitis virus (or canine infectious hepatitis in dogs), is a highly contagious adenovirus, of which there are two strains; canine adenovirus type 1 or adenovirus type 2 (CAV-1 or CAV2). CAV-1 is the strain of most concern in the UK.
The virus invades the endothelial tissues, particularly the smaller blood vessels which results in local haemorrhaging and tissue damage at the affected site. This in turn, leads to inflammation of the brain and other organs.
"ICH was first identified in North America in silver foxes in 1925 (Green 1925), but the disease was only described in domestic dogs in 1947 (Rubarth 1947). Beside red and grey foxes, and other Canidae, such as coyotes, jackals and wolves, CAdV-1 can also infect members of the families... Mustelidae (skunks and otters) and Procyonidae (raccoons) (Spencer et al. 1999)."
As stated by the Merck Veterinary Manual; "Infectious canine hepatitis (ICH) is a worldwide, contagious disease of dogs with signs that vary from a slight fever and congestion of the mucous membranes to severe depression, marked leukopenia, and coagulation disorders. It also is seen in foxes"
Overview of Canine Infectious Hepatitis - Revised June 2013 by Kate E. Creevy, DVM, MS, DACVIM
A case study of three wild foxes from the UK found that; "Canine adenovirus type 1 (CAV-1) was isolated from all three foxes. In a serological study, antibodies to CAV-1 were detected in tissue fluid extracts taken from 11 of 58 (19 per cent) frozen red fox carcases from England and Scotland."
Transmission; Animals become infected though contact with contaminated body fluids, urine or faeces, or by breathing in the virus following contact with an infected animal . The virus can be shed in urine for up to a year after the initial infection, posing a risk to susceptible animals who come into contact with it. Contaminated enclosures, toys and bedding etc., can also serve as a source of transmission.
"The virus can be found in the brain, blood, spleen, upper respiratory tract and spinal cord. The reason the virus becomes pathogenic when large groups of foxes are put together is not positively known. Direct contact from quarrelling and the cannibalistic tendency of a fox, are thought to be causes as well as eating and drinking from the same containers.
The portals of entry are the respiratory tract, digestive tract. and skin wounds. Adult foxes (over one year old) are twice as resistant as are the younger foxes. When the disease occurs in a large group of mixed-aged foxes. the mortality rate is about 15-20 percent. Experimental inoculation shows about 80 percent mortality in foxes below the age of 6 months and approximately 15-20 percent mortality in adult foxes."
Encephalitis of the Silver Fox - Harold A. Kjar, 1943
Unusual Symptoms: Blue Eye: A condition caused by canine infectious hepatitis - Corneal clouding (“blue eye”) is the result of immune-complex reactions after recovery from acute or sub-clinical disease. This reaction is also observed in some animals vaccinated with the live attenuated vaccine.
Note: The example below is of a sick fox from a fur farm in Qubec, that has thankfully since been closed down and the owner prosecuted. It is unknown what conditions this fox was suffering.
Clinical signs;
Hepatitis (CAV-1)
Partial anorexia
Hyper-excitability
Fever
Vomiting and/or diarrhoea
Convulsions
Ataxia
Weakness of limbs and/or paralysis
Hallucination
Respiratory Disease (CAV-2)
Dry, hacking cough
Retching Coughing up white foamy discharge
Conjunctivitis
Treatment; There is no specific treatment for canine infectious hepatitis, treatment is symptomatic and supportive. The goal of treatment to limit secondary infections, to support fluid balance and to control any haemorrhaging. In mild cases foxes can recover, but severely sick foxes may require a blood transfusion. It is though up to 20% of those infected succumb to the disease, it is for this reason vaccination is recommended.
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