Both of Mycoplasma gallisepticum (MG) and Mycoplasma synoviae (MS) infections are the most common Mycoplasma infection in domestic poultry. The disease is associated with economic losses in poultry. MG and MS are commonly spread within chickens (Gallus gallus domesticus) and turkeys (Meleagris gallopavo domesticus) flocks; however, they are frequently isolated from quails (Coturnix coturnix) and several avian species. Diagnosis of MG or MS infections is confirmed by isolating the organism in a cell-free medium or directly detecting its DNA in infected tissues or swab samples. Serological tests are also widely used for diagnosis. However, advances in molecular biology represented a rapid and sensitive alternative to the traditional culture methods requiring specialized techniques and sophisticated reagents. Several Mycoplasma molecular diagnostic tests are implemented: including polymerase chain reaction (PCR), Random Amplified Polymorphic DNA (RAPD), arbitrary primed polymerase chain reactions (AP‐PCR), and Multiplex real-time polymerase chain reaction (Multiplex MGMS). Current control practices against Mycoplasma infection include intense biosecurity, biosurveillance, medication, and vaccination. However, the egg-borne nature of avian Mycoplasma infection complicates controlling the infection. This review focuses on the advances in diagnosis and control of avian Mycoplasma infection, especially MG and MS infections.
Description of the disease: Avian mycoplasmosis is caused by several pathogenic mycoplasmas among which Mycoplasma gallisepticum (MG) and M. synoviae (MS) are considered the most important. MG causes chronic respiratory disease of domestic poultry, especially when flocks are stressed and/or other respiratory pathogens are present. The disease is characterised by coryza, conjunctivitis, sneezing, and sinusitis, particularly in turkeys and game birds. It can result in significant production losses and downgrading of meat-type birds, and loss of egg production. MS may cause respiratory disease, synovitis, eggshell alteration, loss of egg production and carcass downgrading or it may result in a silent infection. MG and MS strains vary in infectivity and virulence, and infections may sometimes be inapparent.Detection of the agent: MG and MS can be identified by immunological methods after isolation in mycoplasma media or by detection of their DNA in field samples or cultures. Samples for isolation can be swabs of organs or tissues, exudates, diluted tissue homogenates, aspirates from the infraorbital sinuses or joint cavities, material from egg yolk or embryos. Clinical signs and lesions will influence the sample selection. Broth and agar combined with basic biochemical tests are used for isolation and first recognition of theMycoplasma, but identification of the genus and species is made through immunological tests (e.g. fluorescent antibody or immunoperoxidase tests) and/or biomolecular tests. DNA detection methods based on the polymerase chain reaction are commonly used in several specialised laboratories. Serological tests: Several serological tests are used to detect MG or MS antibodies, but due to variations in test specificity and sensitivity, they are recommended only for flock screening rather than for testing individuals.The most commonly used are the rapid serum agglutination (RSA) test, the enzyme-linked immunosorbent assay (ELISA) and the haemagglutination inhibition (HI) test. In the RSA test, sera are mixed with commercially produced stained antigen and sera that react within 2 minutes are heated at 56°C for 30 minutes and retested. Sera that still react, especially when diluted, are considered positive and are tested by either ELISA or HI for confirmation. Several commercial MG and MS antibody ELISA kits are available. Requirements for vaccines: Although the preferred method of control is maintenance of MG-and MS-free flocks, both live and inactivated vaccines are used in chickens. Vaccination should be considered only in specific cases on the basis of the epidemiological situation in the area or in farmswhere infection is inevitable. The normal use is to prevent egg-production losses in commercial layers, although vaccines may also be used to reduce egg transmission in breeding stock or to aid MG eradication on multi-age sites. It is important to vaccinate before field challenge occurs.Available live vaccines for MG for chickens are produced from the F strain and strains ts-11 and 6/85, which are apat...
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