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Mycoplasmosis Of Pet Birds

Avian Mycoplasmosis, Mycoplasmosis Of Pet Birds

Albert Bernhard Frank (1889), a German Biologist, first coined the term Mycoplasma which is originated from the Greek word mykes (fungus) and plasma (formed). Earlier Mycoplasma was known as pleuropneumonia-like organisms (PPLO). Adler (1957) first reported isolation of PPLO from the air sac of a parakeet bird.
 Mycoplasma is the smallest pathogenic bacteria (0.3–0.8 μm) and is pleomorphic in shape due to absence of the rigid cell wall. In stained smears, they appear as ring, globules, filaments or elementary bodies. The cell membrane is constituted of trilaminar structure enriched with phosphoprotein, lipoprotein, glycolipid, phospholipid and sterol moieties. Mycoplasma belongs to the class Mollicutes, order Mycoplasmatales, and family Mycoplasmataceae. The family comprises of two genera i.e. Mycoplasma and Ureaplasma. Among different species under the genus Mycoplasma, M. gallisepticum, M. iowae, and M. sturni are associated with pet bird infection.

 An epidemic of Mycoplasmal conjunctivitis was noticed in house finches (Carpodacus mexicanus) in USA in 1994. Other birds such as budgerigars, cockatiel, canary, yellow-naped Amazon parrot, pigeons, pea-fowls (Pavo cristatus), fledgling cliff swallows, European starling (Sturnus vulgaris), chukar partridges (Alectoris chukar), ring-necked pheasants, purple finches (Carpodacus purpureus), evening grosbeaks (Coccothraustes vespertinus), pine grosbeaks (Pinicola enucleator) are also reported to be infected. Concomitant Mycoplasmal infection with other bacteria and protozoa (Cryptosporidium spp.) was detected in Amazon parrots and fledgling cliff swallows. Experimentally, American goldfinch (Carduelis tristis) carried M. gallisepticum for prolonged period without showing any clinical sign. House sparrows (Passer domesticus) are transiently infected experimentally with M. gallisepticum for a short period. In United States, tufted titmice (Baeolophus bicolor) bird was reported as non-clinical carriers of M. gallisepticum.

 Feeders or any focal point where the birds gather, act as a source of M. gallisepticum infection, because the infected birds excreate their droplets in the feeder. Statistical correlation (multivariate analysis) was established between presence of tube style feeders, non-breeding period and low environmental temperature and M. gallisepticum infection in house finches. Vertical way is a rare possibility of Mycoplasmal transmission in birds.

 Clinically the infected birds show variable symptoms ranging from serous nasal discharge, sinusitis, swollen eyes with discharge, conjunctivitis and blindness (Fig. 2.10). In fledgling cliff swallows and European starling (Sturnus vulgaris) infected with M. sturni, bilateral conjunctivitis, episcleritis, epiphora, hyperaemia of palpebrae and nictitans are observed. Gross lesions in birds include congestion of mucosa and accumulation of exudates in nasal sinus, trachea, bronchi, and air sacs. Air sac congestion was also detected in budgerigars experimentally challenged with M. gallisepticum. Histological investigation in birds reveals the presence of mucous gland hyperplasia and thickened mucous membrane of the respiratory tract with mononuclear cell infiltration. In European starling birds, ulceration of mucous membrane and absence of epithelial hyperplasia and lymphoplasmacytic infiltration was observed. In fledgling cliff swallows, lymphoplasmacytic conjunctivitis, rhinitis and infraorbital sinusitis with follicular lymphoid hyperplasia were detected.

 Conjuntival swabs and head, lung, and spleen in 10% buffered formalin after post-mortem, can be collected as clinical samples from the suspected birds. The smears prepared from clinical specimens are stained with Giemsa. M. gallisepticum appears as coccoid organisms having 0.25–0.5 lm in size. Contrast phase microscopy, dark phase illumination techniques can be used for their direct visualization. M. gallisepticum can be isolated in specialized medium supplemented with 10–15% heat-inactivated avian, swine or horse serum. Change in broth colour indicates positive growth after incubation at 37 °C for 3–5 days. Serum plate agglutination test is the rapid serological test for detection of M. gallisepticum antibodies in birds, although, sometimes it produces false positive result due to cross reaction. PCR targeting 16SrRNA gene and loop-mediated isothermal amplification (LAMP) assay based on a gene within the pyruvate dehydrogenase complex (pdhA) are developed for rapid detection of M. gallisepticum.

 In house finches, application of oral tylosin (1 mg/ml drinking water for 21 days) and ciprofloxacin eye drop (for 7 days) successfully treated conjunctivitis associated with M. gallisepticum. Doxycycline (40–50 mg/kg body weight, orally) is also recommended for Mycoplasmal infection in cockatiels and amazons.

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