It is possible to identify infection by culture but PCR techniques are now the preferred option for diagnosing Chlamydophila infection. Such techniques are extremely sensitive and avoid problems with poor viability of the organisms. Ocular swabs are generally used for isolation but organisms may also be detected in vaginal swabs, abortuses and rectal swabs, although these are seldom used diagnostically. Since the organism is intracellular, it is necessary to obtain good quality ocular swabs that include conjunctival cells .
Other techniques for demonstrating the organism are less sensitive and less reliable than PCR. Chlamydial antigen tests based on detecting group specific antigen using ELISA or similar techniques are available. It is also possible to stain conjunctival smears with Giemsa stain to check for inclusions, but this technique is very unreliable for diagnosis since Chlamydial inclusions may be confused with other basophilic inclusions [Streeten 1985].
Antibody detection can confirm the diagnosis of infection in unvaccinated cats. immunofluorescent techniques are usually used for determining antibody titres but ELISA techniques can also be used to assess serological responses. Some cross reactivity with other bacteria occurs such that low IF titres of up to 1:32 are generally considered to be negative. Established active or recent infections are associated with high titres often of 1:512 or greater. Serology can be particularly useful to establish whether infection is endemic in a group. It can also be of value in investigating cases with chronic ocular signs. A high titre suggests that chlamydophila may be an aetiological factor whereas a low titre discounts likely chlamydophila involvement.