Avian malaria caused by Plasmodium and the malaria-like parasites of the genus Haemoproteus has been regularly described in multiple regions worldwide. These parasites significantly affect many avian taxa, including domestic chickens and fighting cocks. There are limited epidemiological studies of these blood parasites in vertebrate hosts, especially in Thailand.

Plasmodium spp. in domestic and wild birds are microscopic, intracellular parasitic protozoa within the blood cells and tissues cause avian malaria. A 17-month-old Magellan penguin (Spheniscus magellanicus) with a clinical signs of anorexia, depression, and respiratory distress for 3 days was submitted to the Pathology Department of Veterinary Medicine, Cheju National University in October 2005. It was born and reared in the Jeju Island. Grossly, the liver was enlarged, pale and friable. The spleen was also enlarged with dark red coloration and friable. Histopathologically, the lesions in the liver were characterized by multifocal infiltration of macrophages and lymphocytes especially in perivascular regions. The schizonts of Plasmodium spp. contained up to 30 merozoites were found in numerous infiltrated mononuclear cells. Similarly, histiocytic cells were proliferated in red pulp of spleen and the schizonts were found in these cells. Numerous dark brown pigments were widely distributed in the liver and spleen. The result of the nested polymerase chain reaction clarified the causative agent of this case was Plasmodium spp.. This is the first report for the outbreak of avian malaria caused by Plasmodium spp. in a penguin that was born and reared in Jeju Island in Korea.

Avian haemoparasites are known to exert negative pressures on theirhosts causing considerable pathology and mortalities. The present study reports on the prevalence of haemoprotozoa and microfilaria in various species of wild birds and domestic poultry in Selangor, Malaysia, and contributes to the database on the occurrence of thesepathogens among avifauna in the country. Giemsa-stained thin blood smears were screened from 728 birds representing five avian orders, namely Galliformes, Anseriformes, Phoenicopteriformes, Pelecaniformes and Gruiformes. The most common haemoparasite was Plasmodium, with a prevalence of 8.0%. The aquatic/wetland species of birds (Anseriformes and Gruiformes) were the most common hosts for this pathogen with high infection rates (31.8% – 50.0%). The prevalence of Plasmodium in domestic poultry was moderate (2.7%). Leucocytozoon sabrazesi and L. caulleryi were confined to the Galliformes with relatively low average infection rates of 0.7% and 0.5%, respectively. Haemoproteus was detected for the first time in domestic poultry and Red Jungle fowls in the country, with anaverage prevalence of 0.8%. Trypanosomes and microfilaria were only present in the village chickens and Red Jungle fowls, with high microfilaraemia rates (19.0%) in the latter. The current compilation will contribute to our understanding on avianhaemoparasite transmission in the country.