Mycoplasma meleagridis

Mycoplasma meleagridis
Phylum	Firmicutes
Class	Mollicutes
Order	Mycoplasmatales
Family	Mycoplasmataceae
Genus	Mycoplasma
Species	M. meleagridis

Disease Also Known As: Mycoplasma Air Sacculitis — Mycoplasma Infectious Stunting — Mycoplasmosis

Introduction

Mycoplasma meleagridis is a small bacterial pathogen that causes air sacculitis, musculoskeletal disease/deformities and reproductive problems in turkeys and occasionally wild birds.

It shares antigens with many other members of its Mycoplasma family but is serologically distinct.

Distribution

M. meleagridis is assumed to be present wherever turkeys are reared, which likely makes the disease of global distribution.

M. meleagridis is transmitted mainly vertically from infected hen’s oviducts to their progeny via the egg and also via semen. Ixodes ticks can also act as a vector. See Tick Disease Transmission for more details on ticks as vectors of disease.

Signalment

M. meleagridis usually affects young poults under 16 weeks of age.

It has also been isolated from healthy wild turkeys and birds of prey.

Clinical Signs

Often very few outward signs are caused, except for a reduced growth rate, which varies in severity.

Birds are often emaciated and unthrifty. Abnormal breathing sounds, tachypnoea, nasal discharge and sneezing are the usual signals of mycoplasmal air sacculitis but present similarly to many other respiratory pathogens.

Skeletal perosis (slipped tendons causing distal limb luxations and deformities) may affect up to 10% of a flock and can be uni or bi-lateral. This may cause lameness and limb swelling. Occasionally, crooked necks and abnormal feathers are also seen. Flock mortality may also increase. Neurological and ophthalmological disease has also been noted in some cases.

Reproductive signs include decreased egg production and reduced hatchability.

Diagnosis

M. meleagridis can be isolated from the upper respiratory tract, air sacs, phallus, semen, cloaca and sinuses. Swabs or exudates can be cultured on Mycoplasma agar and broth media. It is important that this is either done immediately, or that transport to a laboratory is rapid and in a cool, moist environment. Colonies may take up to 7 days to appear and often eventually form a typical fried egg appearance: small and flat with rough centres.

The bacterium can then be identified using PCR or serological tests including growth inhibition, metabolic inhibition and immunofluorescence, of which immunofluorescence is preferred due to its efficacy even in mixed cultures. PCR can sometimes also be performed directly on tracheal or cloacal swabs.

ELISAs are available and effective for antibody detection and can also be used on egg yolk. They have almost totally replaced the slide agglutination test which was insensitive.

On post-mortem, air sacculitis is the most common lesion found, featuring thickened air sac walls with a caseous exudate within the sacs. Lymphoid nodules have been found in the air sacs of some affected turkeys. Changes usually become less marked with age. Synovitis and ascites are also regularly noted.

Perosis of the tibiotarsal and tarso-metatarsal bones is also seen, although less frequently and is occasionally accompanied by cervical vertebral deviation.

Treatment

Tylosin is the most commonly used and effective antibiotic and can be given in water for the first ten days of life. Lincomycin, spectinomycin and gentamycin have also been used with success.

Eggs can also be treated by dipping in cold tylosin solution for 15-20 minutes or by heating to 46-47⁰ for 11-14h before incubation, although heating in particular can reduce fertility.

Control

Eradication is difficult due to vertical transmission from infected hens.

Testing of males or semen for artificially inseminated flocks is imperative. Swabs and samples should also be taken during the breeding season.

The disease is not seen as economically important enough to justify production of a vaccine.

Mycoplasma meleagridis Learning Resources
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References

This article was originally sourced from The Animal Health & Production Compendium (AHPC) published online by CABI during the OVAL Project. The datasheet was accessed on 1 July 2011.