Clinical signs: In most of the cases in initial stages like bacterial infections there is leucocytosis with neutrophilia, which at later stages of the disease may convert to leucocytosis with lymphocytosis. There is slight change in albumin – globulin ratio and also in total protein Other manifestations like abortions/ still births/ premature births, fever, pneumonia/eneritis etc. may also be noticed.
Cytological studies: Recognition of elementary bodies and/or cytoplasmic inclusions in impression smears, scraping or exudates or fluids stained by modified Giemsa or Giemenz methods.
Isolation of specific agents is done from discharges, blood, faeces or postmortem tissues of dead animals in 6-7 day-old chick embryos through yolk sac route or in mice or in guinea pigs through intra peritoneal route or footpad inoculations.Serology plays an important role in the diagnosis of latent or chronic infections as well as in the confirmation of on-going diseases. The most efficient serological method of the diagnosis is the complement fixation test (CFT), agar gel diffusion test (AGDT), agglutination test, serum neutralization (SN) and haemagglutination inhibition (HI) test. Enzyme linked immunosorbant assay (ELISA) is being used routinely for diagnosis of infection. The immunofluorescent test (IFT) is however the most sensitive than any other diagnostic tests and is utilized for confirmation. In addition, immuno-peroxidase and immuno-histochemical tests are also used for the diagnosis. Electron microscoples (E/M), polymerase chain reaction (PCR), nucleic acid hybridisation (NAH) are the recent biotechnological tools being used in the diagnosis of Chlamydial infection.