Microfilariae are commonly found in the blood of wild birds but are rare to absent in poultry except in southeast Asia where infections in chickens and waterfowl occur. When psittaciformes were commonly imported, it was not unusual to observe microfilariae in their peripheral blood, especially in imported cockatoos.
At least 16 genera of filarids are found in avian species. All have an indirect life cycle with bloodsucking insects (eg, lice, mosquitoes, midges) serving as intermediate hosts. Adults are relatively short lived and mature in body cavities, including the eye and ventricles of the brain, respiratory system, cardiovascular system, or connective tissues; some produce characteristic subcutaneous nodules. In contrast, microfilariae are long lived and may be numerous in the skin as well as in the circulation. Microfilariae can be observed in blood smears. However, a buffy coat smear obtained from a microhematocrit tube is a more sensitive method of diagnosis. Increased numbers of microfilariae have been seen in stressed individuals, but they rarely cause clinical disease or mortality. A possible exception is infection of emus with Chandlerella, a common filarid of the brain of free-living grackles. Parasites apparently do not produce microfilariae in emus. Affected emus show signs of CNS disease. Treatment with ivermectin, fenbendazole, and levamisole, and surgical removal of adult parasites have been used.
Last full review/revision March 2012 by Arnaud J. Van Wettere, DVM, MS, DACVP