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Mycoplasma
meleagridis
Infection |  |
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M
meleagridis
infection is a widespread, egg-transmitted disease of turkeys found worldwide. The primary lesion in the progeny is airsacculitis.
M
meleagridis
is thought to be a specific pathogen for turkeys, and the organism is commonly found in the respiratory and reproductive tracts. It has been eradicated in most basic breeder and many commercial flocks. |
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M
meleagridis
was recognized as a pathogen of turkeys after widespread elimination of the bacteria from breeding stock. |
| Transmission and Pathogenesis: |
| Infection is established primarily through egg transmission, which can be as high as 30-50% or higher early in the production cycle. However, transmission of
M
meleagridis
is also related to genital contact. Early infections usually become quiescent at sexual maturity. In the tom, the phallus and adjacent tissues are infected and contaminate semen, thus infecting the vagina of the hen. Hens may retain infection in the bursa of Fabricius, which serves as a source of infection of the reproductive tract after rupture of the cloacal-vaginal occluding membrane at puberty. Infection ascends the reproductive system and may reach the surface of
the ovary. The high rate of egg transmission of
M
meleagridis
is from infection of the reproductive tract being incorporated into the egg after ovulation. Infection of the respiratory tract leads to transmission among birds in young flocks and may be a factor in the spread to flocks previously free of infection. Hatchery transmission is also possible. |
| The marked difference in the pathogenicity of various strains of
M
meleagridis
results in variable clinical manifestations. The high incidence of air sac infection in poults suggests a symbiotic host-parasite relationship.
M
meleagridis
may be involved in crooked necks and leg deformities, but the pathogenesis of this syndrome is not clear. The vaginas of naturally infected hens are free of infection 1-3 mo after the source of infection is removed. Immunity is not permanent, and hens can be reinfected with contaminated semen. |
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| Clinical Findings: |
| Embryo infection appears to reduce hatchability, poult quality, and growth rate. Superimposed stress may cause considerable mortality in poults during the first few weeks. Infection during early rapid growth of hock joints, periarticular tissues, cervical vertebrae, and adjacent bone may produce major bone deformities such as crooked necks and hocks. Rales may develop in poults 3-8 wk old and persist for several weeks without significant mortality or serious interference with
growth. |
Lesions:
| Day-old poults have thoracic airsacculitis with thickening, turbidity, and marked caseous exudate. In 1-3 wk, the lesions may extend to the abdominal air sacs. These lesions recede with age. The air sac lesions of roaster and mature birds are probably related to other factors. Tracheitis may be present, but sinusitis does not occur. |
| Microscopic lesions in hens consist of lymphocytic foci in the fimbria, uterus, and vagina. In young poults, inflammatory lesions are seen in the air sacs and lungs. |
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| Diagnosis: |
| A high incidence of air sac lesions in day-old poults suggests
M
meleagridis
infection. The serum plate agglutination or ELISA test may be used. Confirmation is generally by hemagglutination-inhibition, isolation and identification of the organism, or both.
M
gallisepticum
, chlamydiae, bacteria, and respiratory viruses such as influenza must be eliminated as causes of air sac infection. |
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| Treatment and Control: |
| The commercial use of flocks free of
M
meleagridis
should be monitored by serology and/or by examining pipped embryos or cull poults for airsacculitis. Semen used for insemination must be free of
M
meleagridis
. Dipping eggs in tylosin or another suitable antibiotic reduces the incidence of transmission in infected flocks and may improve weight gains and feed conversion ratios. Inoculation SC of a suitable antibiotic at 1 day of age or water medication for the first 5-10 days appears to reduce airsacculitis caused by
M
meleagridis
and may improve weight gain. |
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