AVIAN MALARIA

Nature of the disease

Avian malaria is caused by parasites of the Plasmodium genus. The disease is transmitted by mosquitoes.

Classification

SPC List D

Susceptible species

Some 65 Plasmodiun sp. have been isolated from over 1,000 different species of birds. Few of the Plasmodium sp. which have been identified appear to be natural parasites of domestic poultry. A number of other species of Plasmodia, that occur primarily in passerine birds, can infect or have been experimentally transmitted to the domestic fowl

Distribution

Plasmodium spp. pathogenic for domestic poultry are found mainly in Africa, Asia and South America. It has been recently identified in American Samoa.

Clinical signs 

Avian malaria produces a wide range of effects in avian hosts, from no apparent clinical signs to severe anaemia and death. Pl. gallinaceum, Pl. juxtanucleare and Pl. durae appear to be the most dangerous for poultry, producing up to 90% mortality.

Post-mortem findings

Intense and severe anaemia is the main finding. The associated tissue hypoxia can produce tissue necrosis. Hypertrophy of the spleen and the liver.

Differential diagnosis 

Other causes of anaemia in poultry include:

• Iron deficiency 
• Egg drop syndrome 
• Leucocytozoonosis
• Spirochaetosis
• Blood sucking external parasites e.g. fleas, mites, ticks and bugs
• Chicken anaemia agent 
• Bbig liver and spleen disease
• Coccidiosis

Specimens required for diagnosis

 Blood smears and impression smears of liver and spleen should be collected and stained with Leishman’s, Giemsa’s, or Wright’s stains for direct microscopic observation.

Transmission 

Avian malaria is transmitted by mosquitoes. Avian plasmodia characteristically develop in culicine mosquitoes – Culex and Aedes.

Risk of introduction 

Avian malaria could be introduced through imports of infected birds, or via  migrating wild birds. Quarantine and import controls should be used to reduce the risk of importing infected birds.

Control / vaccines

in drinking water, Chloroquine is efficient as well as Sulfamides (although they are inefficient in Mammals).Control depends upon breaking the mosquito transmission cycle, by eradication or reduction of mosquitoes, or by isolating the poultry flock by mosquito-proof housing.

References

• BUSSIERAS J, CHERMETTE R, Protozoologie In Parasitologie Vétérinaire, Ecole Nationale Vétérinaire D'Alfort, 1992, p 157.
• JARVI SI et al. Detection of avian malaria (Plasmodium spp.) in native land birds of American Samoa, Conservation Genetics 4 (5): 629-637, 2003
• Plasmodium infection, In Merck Veterinary Manual, National Publishing Inc. Eight ed, 1998, Philadelphia, p 1883