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By Dr. Tahseen Aziz, Rollins Animal Disease Diagnostic Laboratory, Raleigh, NC, USA and Dr. H. John Barnes, College of Veterinary Medicine, NC State University, Raleigh, NC, USA
Embryonic mortality and inferior poult quality are the primary manifestations of vertical infection of turkeys with Mycoplasma iowae. Embryos die during late incubation, typically between days 18 and 24. Decreased hatchability in affected turkey flocks averages 2 - 5%. Infected poults that hatch may be of second quality. Embryonic mortality and decreased hatchability due to M. iowae infection can vary widely from minimal to significant and of extended duration.The extent of hatchability loss depends on the virulence of the M. iowae strain, rate of egg transmission (i.e., number of hens transmitting mycoplasmas into eggs), and dose of the organism. Other factors related to egg-incubation conditions may also influence the rate of embryonic mortality in hatches of M. iowae-positive flocks. There is evidence that high temperatures during incubation can exacerbate mortality in M. iowae-infected embryos. It is important to realise that considerable variation exists among M. iowae strains in their pathogenicity for turkey embryos. Some isolates are more embryo lethal, causing death of the embryo with marked lesions, particularly stunting and edema, while others have little to no affect on embryo viability.
Lesions in natural and experimental M. iowae infected embryos include stunting, edema (particularly around the head area), hemorrhage, excess urates in ureters, poor feathering, abnormal feathers (clubbing of down), hepatomegaly, splenomegaly, and occasional hemorrhage of the chorioallantoic membrane. Although airsacculitis has been described in cull day-old poults naturally infected with M. iowae, the air sac lesions could not be attributed convincingly to M. iowae, as infection with other mycoplasmas, especially M. meleagridis, was not ruled out. However, turkey poults inoculated directly into their air sacs with M. iowae developed lesions of varying severity. Histologically, there was exudative and cellular airsacculitis characterised by fibrinous exudate and infiltrates of heterophils and mononuclear inflammatory cells.
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Source: World Poultry, volume 27, no. 1, 2011
