Nosodes, strictly speaking a form of isopathy but very much homeopathic in principle, have long been discredited as being of any use in protecting animals against disease. The Faculty of Homeopathy itself even advises they cannot be relied on to protect in this way and recommend vaccination instead:
‘Nosodes are sometimes offered as alternatives to conventional vaccines, in both the human and veterinary fields. The Faculty is of the opinion that there is currently insufficient evidence for it to promote this methodology. The Faculty follows the Department of Health guidelines on immunisation and recommends that immunisation be carried out in the normal way unless there are medical contra-indications.’
They also advise:
‘Those patients who seek to use nosodes in place of conventional travel vaccinations and malaria prevention, should note that this method is currently unlikely to be acceptable to insurance providers. Likewise, in veterinary applications, they will currently not fulfil ‘pet passport’, equine competition or official kennel requirements.’
Yet it seems some pet insurance companies—unlike travel insurers, boarding kennels and the Department for Environment, Food & Rural Affairs (DEFRA) who supervise pet passports—will accept the validity of the use of nosodes simply, according to their spokesperson, on the recommendation of a qualified vet. Direct Line were quoted as saying, ‘As an insurer, we are not in a position to advise on the vet's clinical judgement’.
When that judgement is flawed and so unbalanced as to represent a danger to our animal patients though, perhaps they should reconsider their position. Simply denying responsibility isn’t good enough. Then again, who can blame them when the Royal College of Veterinary Surgeons, the governing body for UK profession, tacitly endorses the use of pseudoscience and magical thinking in veterinary medicine because, according to then president, Bradley Viner, there is a ‘public demand’ for it and ‘there are strong views about these issues on both sides of the argument’. 
Well, there used to be a ‘public demand’ for the docking of dogs’ tails, bull baiting and cock fighting, but you don’t hear much from the RCVS about ‘both sides of the argument’ for them.
1] Price, A (2017) ‘Concern at insurance policies allowing nosodes’, Veterinary Times, vol. 47, no. 8, p. 35.
2] Viner, B. (2016) 'Homeopathy and Cancer' (letter), Veterinary Record, vol. 179, no. 3, p. 79. [doi:10.1136/vr.i3862]