OverviewChlamydophila felis is a Gram-negative bacterium and its primary target is the conjunctiva. The bacterium does not survive outside the host. Infection Transmission requires close contact between cats; ocular secretions are probably the most important body fluid for infection. Most cases occur in cats under 1 year of age. Chlamydophila felis is the infectious organism most frequently associated with conjunctivitis. Disease signs Unilateral ocular disease generally progresses to become bilateral. There can be intense conjunctivitis with extreme hyperaemia of the nictitating membrane, blepharospasm and ocular discomfort. Transient fever, inappetence and weight loss may occur shortly after infection, although most cats remain well and continue to eat. Diagnosis PCR techniques are now preferred for diagnosing C felis infection. Ocular swabs are generally used. In unvaccinated cats, antibody detection can be used to indicate infection. Disease management Tetracyclines are generally regarded as the antibiotics of choice. Doxycycline has the advantage of requiring only single daily administration and is given at a dose of 10 mg/kg orally. Vaccination should be considered if there is a history of confirmed chlamydial disease in a shelter. Single housing and routine hygiene measures should suffice to avoid cross-infection. Cats maintained together for longer terms should be vaccinated regularly. In breeding catteries where C felis infection is endemic, the first step should be to treat all cats with doxycycline for at least 4 weeks. Once clinical signs have been controlled, the cats should be vaccinated.

Giardia is a protozoan parasite that infects the small intestine of cats and can cause diarrhoea. The biotypes that affect cats do not appear to infect humans. Infection is most common in young cats, particularly from multicat backgrounds. Infected cats that develop clinical signs show small intestinal diarrhoea and there may be associated weight loss. Diagnosis of infection is usually based on an in-practice ELISA for faecal antigen or zinc sulphate flotation of several pooled faecal samples. Polymerase chain reaction (PCR) tests are available but not used so widely. Infection can be detected in clinically healthy cats so interpretation of a positive result in cats with diarrhoea requires care. Fenbendazole or metronidazole are regarded as the treatments of choice. Secondary gut changes may be slow to resolve and so diarrhoea may continue for some time after infection has been eliminated.

Overview: Tritrichomonas foetus is a protozoan organism that is specific to cats and can cause large bowel diarrhoea. It is distinct from other Tritrichomonas species and not considered to be zoonotic. Infection is most common in young cats from multicat households, particularly pedigree breeding catteries. Disease signs: Affected cats show frequent fetid diarrhoea, often with mucus, fresh blood and straining, but generally remain bright and do not lose weight. Diagnosis: Diagnosis of infection is usually based on direct microscopic examination of freshly voided faeces. Polymerase chain reaction (PCR) testing is more sensitive but may detect infections unrelated to diarrhoea and, therefore, requires care in interpretation. Treatment: The treatment of choice is ronidazole, which should be used with care as it is an unlicensed drug for cats with a narrow safety margin. Clinical signs are generally self-limiting in untreated cases, but may take months to resolve.