Aegyptianellosis is a bloodborne intraerythrocytic infection of poultry and wild birds that is usually subclinical. Aegyptianella pullorum can be an important cause of disease in young chickens, originating from nonendemic areas, such as production facilities, where infection can have substantial economic impact.
Etiology of Aegyptianellosis in Poultry
The etiological agent of aegyptianellosis is Aegyptianella pullorum, a gram-negative rickettsial bacterium in the family Anaplasmataceae. Aegyptianella pullorum is the only recognized species in the genus; however, reclassification to the genus Anaplasma has been proposed.
Epidemiology of Aegyptianellosis in Poultry
Aegyptianellosis has been described in a variety of avian species, including chickens, turkeys, guinea fowl, quail, pigeons, crows, waterfowl, ratites, falcons, passerines, and psittacines.
Ticks, especially Argas spp, transmit the organism; infection can also be reproduced by blood inoculation.
Infections are most common in tropical and subtropical areas of Africa, Asia, and southern Europe. Infection of wild turkeys in Texas has been reported.
Clinical Findings of Aegyptianellosis in Poultry
In endemic areas, aegyptianellosis is typically a subclinical infection or causes mild clinical signs. In introduced, younger, or otherwise susceptible birds, clinical signs can include ruffled feathers, anorexia, droopiness, diarrhea, fever, anemia, and high mortality rates.
Death, when it occurs, is due to anemia, which can lead to right-sided heart failure and ascites.
Postmortem lesions of aegyptianellosis can include enlargement of the liver and spleen, enlarged discolored kidneys, and pinpoint serosal hemorrhages.
Infestation with larval argasid ticks and Borrelia infection (see Avian Spirochetosis) can accompany aegyptianellosis.
Diagnosis of Aegyptianellosis in Poultry
Blood smears
PCR assay
Diagnosis of aegyptianellosis is based on detection of the intraerythrocytic organisms on a blood smear or using PCR assay.
Organisms stain purple with Romanowsky stain and appear as single or multiple, round, signet ring (0.3–4 mcm) or irregular oval bodies in RBCs often lateral to the nucleus. Organisms must be morphologically differentiated from trophozoites of Plasmodium and gametocytes of Haemoproteus.
Treatment and Control of Aegyptianellosis in Poultry
Antimicrobial therapy
Tick control for prevention
Aegyptianellosis is treated with tetracyclines, especially doxycycline, which can eliminate the organism from chronically infected birds. Local guidelines must be followed for appropriate withdrawal times to avoid violative residues.
Tick control is an important adjunct to treatment.
Key Points
Aegyptianellosis is a tickborne bacterial disease.
Death is due to anemia that can lead to right-sided heart failure.
Diagnosis is based on identification of the organism in erythrocytes on a blood smear and by PCR assay.
Tetracyclines are used for treatment; tick control is important for prevention.
For More Information
Logue CM, Andreasen CB, Borst LB, et al. Other bacterial diseases. In: Swayne DE, ed. Boulianne M, Logue CM, McDougald LR, Nair V, Suarez DL, associate eds. Diseases of Poultry. 14th ed. Wiley Blackwell; 2020:995-1085.
