Merck Manual

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Professional Version

Israel Turkey Meningoencephalitis

By

James S. Guy

, DVM, PhD, DACVM, DACPV (Deceased), Department of Population Health and Pathobiology, North Carolina State University

Reviewed/Revised Oct 2019 | Modified Jun 2023

Israel turkey meningoencephalitis has been reported only in turkeys. It causes progressive paresis and paralysis with decreased egg production and variable mortality. Diagnosis is by viral isolation and identification by ELISA, PCR, and serology. No specific treatment is available, so control is based on preventing exposure to insect vectors and vaccination.

Israel turkey meningoencephalitis has been reported only in turkeys. It generally occurs only in birds > 10 weeks old. Although the specific vector has not been identified, the seasonal incidence and sporadic occurrence in flocks on the same farms strongly suggest it is transmitted by insect vectors, most likely mosquitoes and Culicoides midges.

Clinical Findings

Turkeys with Israel turkey meningoencephalitis exhibit neurologic dysfunction characterized by progressive paresis and paralysis, with variable mortality. Morbidity and mortality rates average 15%–30% but may be as high as 80%. In turkey breeder hens, egg production drops severely.

Lesions

Gross lesions in turkeys with Israel turkey meningoencephalitis include splenomegaly or atrophy of the spleen, catarrhal enteritis, and myocarditis. The principal microscopic lesions are nonpurulent meningoencephalitis characterized by submeningeal and perivascular lymphocytic infiltration and focal myocardial necrosis.

Diagnosis

Prevention and Control

No specific treatment for Israel turkey meningoencephalitis is available. It is best prevented by measures designed to reduce vector populations and/or locating production facilities away from vector habitats. This disease also may be controlled by vaccination. A live attenuated vaccine has been prepared by serial passage of virus in Japanese quail kidney cells; this vaccine is highly efficacious and commercially available.

Zoonotic Risk

Israel turkey meningoencephalitis virus is not known to be pathogenic for people.

Key Points

  • Israel turkey meningoencephalitis is a disease of turkeys characterized by neurologic disease, with variable mortality and decreased egg production. No other species is known to be affected.

  • Diagnosis is by viral isolation and identification by ELISA, PCR, and serology.

  • Control of Israel turkey meningoencephalitis is based on reducing exposure of susceptible turkeys to vectors. An efficacious, commercially available, live vaccine can be used for immunization.

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