Polyomavirus infection and psittacosis [Chlamydia psittaci infection] in psittacine birds, and pasteurellosis [Pasteurella multocida infection] in rabbits can be challenging diseases to accurately diagnose.

Antech Diagnostics is offering new, state-of-the-art diagnostic profiles for each of these infections. These profiles combine serology and polymerase chain reaction [PCR] technology to better define the disease state of the patient. Test results should be evaluated in conjunction with clinical signs, bloodwork abnormalities, and sometimes with biopsy results to ensure accurate interpretation.

A positive antibody titer indicates exposure to the organism in question, but does not specify whether the host is actively infected. A negative titer in the absence of very recent exposure or peracute disease indicates that there has been no exposure, therefore ruling out the possibility of disease. (A patient with a negative titer may have recent exposure and insufficient time to seroconvert or may be significantly immunocompromised and unable to mount a detectable antibody response.) Detection of IgM directed against a particular organism usually indicates recent infection. A rising titer in samples collected two or three weeks apart (and ideally tested simultaneously) also indicates active infection or exposure.

PCR is an exceptionally sensitive method of detecting organism-specific sequences of nucleic acid and is typically done on whole blood, or swabs taken from the cloaca, from secretions, or from tissues at necropsy. Although a positive PCR result indicates the presence of organism-specific nucleic acid sequences, the significance of this finding needs careful consideration. A positive test result could be from a patient with clinical disease, exposure of the patient without infection or disease, from a sub-clinically infected patient, or due to a contaminated sample.

The combination of serology and PCR testing enables more complete interpretation of the test results. Negative test results on both serology and PCR, even in an ill patient, reduce the likelihood that the specific agent is involved, whereas a positive PCR test in a patient with a negative antibody titer may indicate an immunocom-promised animal, insufficient time to convert, or an environmental contaminant (in which case environmental testing is warranted).