Abnormal lymphocyte morphology should be pondered by the clinician. Lymphocytes can appear reactive. While these changes are not standardized, they include cytoplasmic blebbing and vacuolization, nuclear changes and deeply bluish cytoplasm. Marked reactive changes are usually associated with severe viral infections. Reactivity may also be associated with chlamydial infections and blood parasites.
Monocytes are generally scarce in peripheral blood.
The actual incidence of monocytes in avian blood remains unsettled and will require standardized cytochemical methods to resolve. It is sufficient to say that in many avian hemograms, monocytes are rare to non-existent. Relative or absolute monocytosis is a hallmark for chronic infection. In the avian patient this can indicate chlamydial, mycobacterial, fungal, and granulomatous or organ-reactive bacterial infections. In budgerigars, a relative monocytosis and basophilia may be the only abnormal hematologic finding, suggesting chlamydiosis.