VN June 2023

Vetnuus | June 2023 36 • Other o Poor feathering o Neurological signs - torticollis, tremors, convulsions o Polyuria is frequent due to the nephrotoxic effects of elementary bodies o Infertility Transmission This disease can be highly contagious, with transmission occurring through ingestion (faecal material, mutual feeding, and feeding chicks) or inhalation (respiratory secretions, aerosolised feathers or faecal dust). Egg transmissionmay occur. Theinfectioncanbelatentandactivatedduringstress.Someindications suggest shedding in pigeons is greater in hot weather, possibly as a stress response to heat. A carrier state may exist. Immunity to infection is short-lived, and birds are susceptible to re-infection shortly after treatment ends. Shedding of the organism can start 72 hours after infection, and birds may be shedding for up to days before they start to show clinical signs. The incubation period can be as short as four days, up to 1-2 years. Diagnosis Diagnosis can be difficult, as no single ‘best’ test exists. Testing relies on antigen or antibody detection; ancillary testing can support the presence of the disease rather than just the organism. • The Centre for Disease Control (CDC) classifies the level of diagnosis as o Confirmed case : - The presence of C. psittaci confirmed by isolation, FA of affected tissue, >4x increase in serological titre in paired samples collected two weeks apart & processed by the same lab, or demonstration of the organism in macrophages via Macchiavellos’ or Gimenez stain o Probable case :- clinical infection consistent with Chlamydia combined with one of the following: single high titre obtained after the onset of illness; Chlamydia antigen demonstrated by FA or ELISA in faeces, exudates or cloacal swab o Suspect case : - clinical signs consistent with Chlamydia in a bird epidemiologically linked to another case in a bird or human, but not laboratory confirmed; or an asymptomatic bird with a single high titre or antigen detected; or illness in a bird confirmed with a non- standardised test; or clinical illness that is responsive to appropriate treatment  Antigen detection. Respiratory epithelium (choanal/oropharynx) yields the most reliable samples for antigen detection o Isolation - Cell culture is the gold standard o Cytology - Chlamydia inclusions are most easily demonstrated in serosal membranes, the liver, spleen and affected air sacs. Stained with Giemsa or Macchiavellos stains to show intracytoplasmic inclusions. Negative staining does not rule out Chlamydia. o Immunofluorescence antibody testing (Commercial FA conjugate for detection of Chlamydia spp. may cross- react withM. aviumgiving false positive results) o ELISA tests are available; however, be aware of false positives from S. aureus in the sample. ELISA’s that detects Chlamydia LPS should be avoided because it is serologically related to the LPS of Enterobacteriaceae- falsepositives result fromthepresenceof cross-reactive antibodies in the serum; false negatives occur when Chlamydia is shed intermittently. o Latex agglutination tests (e.g. Clearview) have a high number of false positives due to cross-reaction with bacteria. o PCR tests. Be aware of false negatives: caused by the presence of inhibitors of PCR reaction such as blood, serum, urine, faeces, sputum, hair shafts, lab reagents and specifically haematin, DMSO, NaCl, phosphate- buffered saline, melanin, heparin, detergents and glove powder. DNA cannot distinguish between live organisms and dead organisms (which may be contaminants) • Antibody detection – detection of IgMor IgG or both: o Latex agglutination; IgM NB false positives from S. aureus, P. multocida and Sarcina sp) o Direct Complement Fixation -measures IgG. Only useful if paired serum samples are tested. CF is the most common serological test used in humans, but not used in birds because they producemainly non-CF antibodies with Chlamydia infection. o ELISA, e.g. Immunocomb o BELISA – inhibitory ELISA – a very sensitive test marketed in Germany. • Ancillary testing o Haematology – anaemia, leucocytosis, absolute or relative heterophilia, monocytosis o Chemistries – elevations in CPK, AST, LDH, TP and bile acids if the liver is involved. Uric acidmay be elevated if the kidneys are involved. o EPH – elevations in total globulins, beta and gamma globulins; decrease in albumin o Radiology – hepato-, splenomegaly; air saculitis, pneumonia o Biopsy of liver, spleen or air sac. Currently, in Australia, Chlamydiosis is diagnosed by: 1. PCR of a combined conjunctival, choanal and cloacal swab (blood can be used, but is less reliable) 2. The Immunocomb test is a serological test for IgG. It must be noted that IgG is only detected two weeks after infection and that this test can miss early infections 3. Ancillary testing, particularly a total white cell count and differential. Ideally, all three tests should be run in conjunction (parallel testing) to confirm the diagnosis. • Autopsy o Acute lesions; fibrinous peritoneal exudate, airsacculitis (more frequent in psittacines than splenomegaly), perihepatitis, pericarditis, myocarditis, bronchopneumonia, catarrhal enteritis, nephrosis, Orchitis, epididymitis, oophoritis. Technical I Article