M iowae was originally thought to be of low pathogenicity in producing air sac lesions in chickens and turkeys, but it is a potentially important cause of embryo mortality and reduced hatchability in turkeys. Antigenicity and pathogenicity vary considerably among M iowae strains. M iowae is resistant to 1% bile salts, and an enriched medium similar to those used for other avian mycoplasmas is suitable for culture and isolation.
Infection rates in turkey flocks in Europe and North America have been reduced by intensive eradication efforts in breeding stocks. It is a relatively uncommon infection of chickens and has been reported in geese. M iowae is egg transmitted in turkeys, and horizontal transmission with slow spread within a flock may occur.
Many strains of M iowae are lethal to turkey embryos. Chickens and turkeys experimentally inoculated have shown airsacculitis, stunting, poor feathering, and leg lesions. These effects have not been recognized in the field, probably because most infected birds die before hatching. Older birds appear to be quite resistant.
Clinical Findings, Lesions, and Diagnosis
Affected turkey breeder flocks show no clinical signs other than reduced hatchability (usually 2–5%) due to embryo mortality in the last 10 days of incubation. In many flocks, the hatchability returns to normal after 1–2 mo.
Dead turkey embryos are edematous, congested, and stunted; they may have clubbed down. Poults challenged in ovo or at 1 day of age may develop various skeletal deformities such as rotated tibia, deviated toes, chondrodystrophy, or erosion of the articular cartilage of the hock joint. Feathers may also be poorly developed. Chicks challenged at 1 day of age may develop tenosynovitis and ruptured tendons.
Turkeys apparently have a poor antibody response, and no reliable serologic test is available. Diagnosis relies on isolation and identification of the causative agent or detection of M iowae DNA by PCR.
Treatment and Control
The best method of control is to maintain flocks free of M iowae; however, because serology is unreliable, this may be difficult. Dipping hatching eggs in solutions of enrofloxacin reduced losses in hatchability. However, this antibiotic is no longer permitted for use in food animals in many countries.
Last full review/revision March 2012 by David H. Ley, DVM, PhD, DACVM, DACPV