Feline conjunctivitis is a doxycyline deficiency!
If you have been to any of our CE sessions you may have heard the mantra “feline conjunctivitis is a doxycycline deficiency”. But surely no feline ever expired through lack of doxycycline! So do we mean? The two most common causes of infectious feline conjunctivitis are feline herpes virus (FHV) and Chlamydophila felis.
FHV is of course a virus and won’t respond to doxycyline but coinfections are common. Other less common causes are Mycoplasma felis, which will respond to doxycycline, and rarely calicivirus which is usually self-limiting.
How to identify FHV and C.felis conjunctivitis
Kittens: Upper respiratory disease is a common comorbidity. FHV can result in serious sequelae such as symblepharon (conjunctival tissue adhering to the cornea or eyelids), corneal ulceration, and in serious cases, corneal perforation. Many kittens end up with scarred nasolacrimal ducts that become narrowed and result in watery eyes for life that are unresponsive to any treatment.
Adults: URT disease is much less common as some immunity exists. Generally the clinical presentation gives a clue to the underlying cause. Any corneal ulceration (Fig 1A, 1B) indicates FHV as the cause. A severe chemosis (Fig 1C) is more suggestive of C.felis, especially if there was a 10 day interval between unilateral presentations.