| occurrence of velogenic viscerotropic newcastle disease in pet and exotic birds in 1991. | in 1991, velogenic viscerotropic newcastle disease (vvnd) was diagnosed in domestic psittacine birds in six states: illinois, indiana, michigan, texas, california, and nevada. in the first four states, the disease assumed outbreak proportions. the affected psittacine birds--yellow-headed amazon parrots (amazona ochrocephala oratrix), yellow-naped amazon parrots (amazona ochrocephala auropalliata), cockatiels (nymphicus hollandicus), and conures (unknown species)--exhibited respiratory and/or cen ... | 1993 | 8452504 |