Disease: Turkey malaria.
Hosts: Turkey. Purchase (1942) produced a transient infection in baby chicks. Simpson (1944) infected ducks of various ages. This is probably a natural parasite of some as yet unknown wild African bird.
Location: Erythrocytes. The exo-erythrocytic stages are in endothelial cells.
Geographic Distribution: Africa (Kenya).
Prevalence: Herman (1941) found P. durae in 1 of 75 domestic turkeys in Kenya.
Morphology: This species was described by Herman (1941). The gametocytes are elongate, at the end or side of the host cell, and often displace the host cell nucleus when oriented obliquely to it. This tendency to take an oblique position differentiates P. durae from other avian species of Plasmodium. The pigment granules are usually large, round and black. The host cell is not enlarged. The trophozoites are more or less amoeboid. Presegmenters are often at the end of the host cell. The mature schizonts rarely displace the host cell nucleus. The pigment granules are round, black, up to 8 in number, and tend to become clumped together in the mature schizonts. Six to 14 (usually 8) merozoites are formed. The host cell is not distorted.
Life Cycle: Purchase (1942) and Simpson (1944) found exoerythrocytic stages of P. durae in the endothelial cells of the spleen, liver, lungs and brain of turkeys. The prepatent period is 3 days to 2.5 weeks after intravenous injection and 12 days to 40 days after intramuscular injection (Herman, 1941). Schizogony in the erythrocytes apparently takes 24 hours. The vectors are unknown (Huff, 1954).
Pathogenesis: P. durae causes an acute, often fatal disease in turkeys less than a year old. Twelve out of 14 young poults infected by Purchase (1942) died. They showed some malaise and ruffled feathers, but usually died without any acute signs. Two naturally affected adult birds showed signs of cerebral involvement, emaciation, edema of the legs and high blood pressure.
At necropsy of acute cases (Purchase, 1942) the liver, spleen and kidneys are dark and congested, the lungs slightly edematous, and the pericardial cavity contains an excess of clear fluid. The lumen of the duodenal loop is light chocolate in color and its villi are heavily laden with pigment. There is injection of the superficial vessels of the brain and meninges.
In chronic, naturally infected birds, the spleen is reduced in size, hard and fibrous, the liver is firm, with chronic congestion and much fibrosis. The villi of the duodenal loop are packed with large pigment granules.