Three very severe episodes of Escherichia coli infection in hens from the same farm, at the beginning of laying, are reported. They were characterized by no clinical signs, but sudden mortality, from 5 to 10%, with severe lesions of septicaemia and fibrinous polyserositis. A Gram-negative bacterium was consistently isolated in pure culture from tissues. Isolates were typed biochemically as E. coli, but they were lactose negative and non-motile. The serotyping tests typed the isolates as somatic group O111. The isolates were sensitive to enrofloxacin, amoxycil and colimycin, and partially sensitive to flumequine, all of which were used for therapy. The disease was reproduced experimentally in both specific pathogen free chickens and commercial layers by intramuscular inoculation of the E. coli, but only in some layers when inoculated by the oro-nasal route. The stress of the onset of lay seemed to be the most probable precipitating cause of the disease.

The isolation of four new variants or serotypes of avian infectious bronchitis virus in Italy is reported. The antigenic characteristics of these strains were investigated by cross-neutralization tests with the new isolates, Fa 6881/97, AZ 27/98, AZ 20/97, and BS 216/01; two of the most common European serotypes, AZ 23/74 and CR 88121 (793B); and the classic Massachusetts M41 serotype in association with a panel of 17 specific antisera. On the basis of the results obtained, the new isolates show relevant serologic differences. In fact, the four isolates were not neutralized by antisera against the most common European and American serotypes; the AZ 20/97 isolate was partially neutralized by FA 6881/97 antiserum but not reciprocally. The closely related Fa 6881/97 and AZ 27/98 isolates can be considered rather diffused in our country because they have been isolated over 20 times in the last 3 yr in different parts of Italy. On the contrary, the AZ 20/97 and BS 216/01 isolates were reported only once so far. The reverse transcription-polymerase chain reaction showed that Fa 6881/97 isolate is related to 793B isolate, whereas AZ 27/98 and BS 216/01 isolates appeared not to be related to the most common European and Massachusetts serotypes.

Beginning at the end of March 1999, a syndrome characterized by severe depression, anorexia, fever, and respiratory and enteric symptoms appeared in flocks of turkeys and, to a lesser extent, of chickens in the densely populated poultry-rearing regions of northeast Italy. The disease was characterized by sinusitis, tracheitis, peritonitis, and pancreatitis. The mortality varied between 5% and 90%. The disease was diagnosed as low pathogenic avian influenza, H7N1 serotype. After a summer period of declining cases, the disease reappeared in autumn exclusively in turkeys. Since the middle of December 1999, many farms of chickens, turkeys, and guinea fowl were abruptly affected by a highly pathogenic H7N1 virus, with very severe depression and mortality up to 100% in a few days. By the end of March 2000, nearly 500 farms, representing over 15 million birds, were affected or depopulated. To date, control measures have focused on improved biosecurity measures. Vaccine was not allowed, but its use was debated.

The results of in vitro tests for induction of antibiotic resistance in some strains of Mycoplasma gallisepticum are reported. The number of passages required to induce resistance varied considerably between different antibiotics. In two groups of tests, with different strains of M. gallisepticum, resistance ( 1 mg/ml) to streptomycin appeared after two to three passages, to erythromycin and spiramycin after five to eight passages, to tylosin after nine to eleven and to enrofloxacin after eight to ten passages. With chlortetracycline the increase in resistance was very low (no more than ten times the starting minimal inhibitory concentration). Cross-sensitivity tests using strains with induced resistance to the different antibiotics demonstrated that those which were resistant to tylosin were also resistant to other macrolides ( > 1 mg/ml), whereas strains made resistant to erythromycin and spiramycin appeared only less sensitive (2 to 200 μg/ml) to tylosin in comparison with the original strains. Streptomycin, chlortetracycline and enrofloxacin induced very little or no cross-resistance.

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