South Asian Journal of Parasitology

Leucocytozoonosis is a haemoprotozoan disease of domestic and wild birds caused by species of the genus Leucocytozoon and transmitted by blood-sucking vectors. Indigenous desi chickens reared under extensive or semi-intensive backyard systems may experience substantial vector exposure and can present with non-specific signs of disease. This article describes a clinical case in a two-year-old male Aseel chicken presented with a pale comb, depression, anorexia, ruffled feathers, and open-mouth breathing. Examination of a Giemsa-stained peripheral blood smear demonstrated Leucocytozoon spp. gametocytes, while haematological findings showed reduced haemoglobin (8 g/dL) and packed cell volume (25%). The bird showed clinical improvement following treatment with primaquine in combination with sulfamethoxazole and trimethoprim, together with supportive therapy. The review component outlines the pathogenesis, diagnosis, treatment, and prevention of leucocytozoonosis and considers the broader differential aetiology of anaemia in desi birds. Major mechanisms discussed include haemorrhagic and haemolytic anaemia associated with trauma, gastrointestinal parasites, ectoparasites, and haemoparasites, as well as non-regenerative anaemia related to nutritional deficiency, chronic disease, toxins, and disorders affecting haematopoiesis. The case and review together emphasise differentiation between regenerative and non-regenerative mechanisms when evaluating anaemia in backyard poultry. An integrated diagnostic approach combining history, clinical examination, haematology, blood-smear assessment, parasitological investigation, and targeted infectious-disease testing is emphasised for case interpretation and flock-level management.