Mycoplasma iowae infection in turkeys has been most commonly associated with late embryo death, decreased hatchability, and occasionally a low prevalence of hindlimb abnormalities in young progeny.
M iowae requires enriched media with cholesterol, similar to those used for other avian mycoplasmas for culture and isolation, but is resistant to bile salts because it has a predilection to the intestinal tract.
Antigenicity and virulence vary considerably among M iowae strains.
Epidemiology and Transmission of Mycoplasma iowae Infection in Poultry
Mycoplasma iowae is vertically transmitted in turkeys, and horizontal transmission with slow spread within a flock may also occur.
Infection rates in turkey flocks in Europe and North America have been lowered by intensive eradication efforts in certain primary breeding stocks; however, M iowae is not currently included in the National Poultry Improvement Plan in the US. It is a relatively uncommon infection of chickens and has been reported in geese. However, from time to time, outbreaks occur and are generally limited to poults coming out of infected breeding flocks.
Chickens and turkeys experimentally inoculated have shown airsacculitis, stunting, poor feathering, and leg deformities. These effects are rarely recognized in the field, except for some outbreaks in young turkeys with skeletal lesions.
Clinical Findings and Lesions of Mycoplasma iowae Infection in Poultry
Turkey breeder flocks with M iowae infection show no clinical signs other than decreased (usually 2–5%) hatchability due to embryo death in the last 10 days of incubation. In many flocks, hatchability returns to normal 1–2 months after the onset of clinical signs.
Dead turkey embryos are edematous, congested, and stunted; they may have clubbed down syndrome (irregular feather growth). Young poult flocks from an infected breeder flock show an inability to stand, lameness, hock joint arthritis, stunting, and retarded growth. A variable percentage of these birds develops skeletal deformities (see images of turkeys with M iowae infection).
Courtesy of North Carolina State University Poultry Health Management.
Poults experimentally challenged in ovo or at 1 day old developed various skeletal deformities, such as rotated tibia, deviated toes, chondrodystrophy, and erosion of the articular cartilage of the hock joint. Chicks experimentally challenged at 1 day old developed tenosynovitis and ruptured tendons (1).
Natural infections in young commercial turkey flocks have been associated with skeletal lesions consistent with chondrodystrophy, characterized by leg and vertebral deformities. Microscopic skeletal lesions have been characterized by excess cartilage matrix and disorganization of chondrocytes, which are features of osteochondrosis.
Diagnosis of Mycoplasma iowae Infection in Poultry
Bacterial culture
Real-time PCR assay
In turkeys, M iowae infection should be considered in cases of late embryo death and decreased hatchability and in young turkeys with leg and vertebral chondrodystrophy.
M meleagridis infection, poor poult quality, and nutrient deficiencies are the top differential diagnoses for these conditions as well.
Turkeys develop only a weak antibody response against M iowae, and no reliable serological test is available.
Diagnosis relies on culture, isolation, and identification of the isolated colonies or on detection of M iowae DNA by real-time PCR assay. Clinical swabs taken from infected sites (yolk sacs from dead, in-shell embryos, air sacs, and joints of young poults), or isolates can be appropriate samples for molecular diagnostics.
Sequence typing by targeting and amplifying specific sequences allows for identification of M iowae isolates and outbreaks and can be particularly useful for epidemiological investigations and for identifying the source breeding flock.
Treatment, Control, and Prevention of Mycoplasma iowae Infection in Poultry
Maintaining breeder flocks free of M iowae
Establishing and maintaining turkey breeder flocks free of M iowae is the best method of controlling and preventing infection. Surveillance is challenging because serological testing is unreliable; however, flock monitoring by real-time PCR assay and strict biosecurity can be implemented.
Key Points
M iowae is vertically transmitted, causing embryo and young poult death in turkeys.
M iowae has not been eradicated from all breeders, and outbreaks happen occasionally.
Real-time PCR assay and sequence typing are useful to identify the source flock and assist monitoring and eradication efforts.
For More Information
El-Gazzar M, Bradbury JM. Mycoplasma synoviae. In: Swayne DE, ed. Boulianne M, Logue CM, McDougald LR, Nair V, Suarez DL, associate eds. Diseases of Poultry. 14th ed. Wiley Blackwell; 2020:929-933.
Kempf I. Avian mycoplasmosis. In: Brugère-Picoux J, Vaillancourt J-P, Shivaprasad HL, Venne D, Bouzouaia M, eds. Manual of Poultry Diseases. Association francaise pour l’avancement des science; 2015:278-285.
References
Bradbury JM, Ideris A, Oo TT. Mycoplasma iowae infection in young turkeys. Avian Pathol. 1988;17(1):149-171. doi:10.1080/03079458808436435
