Isolation of influenza type A viruses from imported pet birds

Evolution and ecology of influenza A viruses

In this review we examine the hypothesis that aquatic birds are the primordial source of all influenza viruses in other species and study the ecological features that permit the perpetuation of influenza viruses in aquatic avian species. Phylogenetic analysis of the nucleotide sequence of influenza A virus RNA segments coding for the spike proteins (HA, NA, and M2) and the internal proteins (PB2, PB1, PA, NP, M, and NS) from a wide range of hosts, geographical regions, and influenza A virus subtypes support the following conclusions. (i) Two partly overlapping reservoirs of influenza A viruses exist in migrating waterfowl and shorebirds throughout the world. These species harbor influenza viruses of all the known HA and NA subtypes. (ii) Influenza viruses have evolved into a number of host-specific lineages that are exemplified by the NP gene and include equine Prague/56, recent equine strains, classical swine and human strains, H13 gull strains, and all other avian strains. Other genes show similar patterns, but with extensive evidence of genetic reassortment. Geographical as well as host-specific lineages are evident. (iii) All of the influenza A viruses of mammalian sources originated from the avian gene pool, and it is possible that influenza B viruses also arose from the same source. (iv) The different virus lineages are predominantly host specific, but there are periodic exchanges of influenza virus genes or whole viruses between species, giving rise to pandemics of disease in humans, lower animals, and birds. (v) The influenza viruses currently circulating in humans and pigs in North America originated by transmission of all genes from the avian reservoir prior to the 1918 Spanish influenza pandemic; some of the genes have subsequently been replaced by others from the influenza gene pool in birds. (vi) The influenza virus gene pool in aquatic birds of the world is probably perpetuated by low-level transmission within that species throughout the year. (vii) There is evidence that most new human pandemic strains and variants have originated in southern China. (viii) There is speculation that pigs may serve as the intermediate host in genetic exchange between influenza viruses in avian and humans, but experimental evidence is lacking. (ix) Once the ecological properties of influenza viruses are understood, it may be possible to interdict the introduction of new influenza viruses into humans.

Isolation of orthoreoviruses from psittacine birds

Orthoreoviridae were regularly isolated from imported psittacine birds in the absence of other pathogens or in combination with salmonella. These viruses grew in embryonated eggs, in chicken embryo fibroblasts and in hepatic cell cultures. The viral isolates were classified as orthoreoviridae on the basis of their morphological and physico-chemical properties.

The structural polypeptides of avian paramyxoviruses

The structural polypeptides of twenty-three avian paramyxoviruses from five serotypes were examined by polyacrylamide gel electrophoresis in the presence of sodium dodecylsulphate under reducing and non-reducing conditions. All virus polypeptide profiles consisted of 7--10 polypeptides of which two were glycosylated. Some variation was seen in the profiles of viruses from the same serotype, but groups formed on the basis of their serological relationships in haemagglutination inhibition tests were identical to those formed on the basis of similarities in their polypeptide profiles.

Characteristics of Murayama virus in various cell cultures and laboratory animals

Some biological properties of Murayama virus, a new paramyxovirus, were studied. The virus grew well in primary monkey kidney cells as well as embryonated eggs, while the virus yields in primary chick embryo and BHK-21 cells were much lower. The infected BHK-21 cells formed large syncytia and showed typical hemadsorption, but did not produce any detectable amount of hemagglutinin in the culture fluid. The virus yields were very low in Vero. LLC-MK2 and MDCK cells at first passages. The addition of trypsin to the medium enhanced virus growth in Vero and LLC-MK2 but not in MDCK cells. Cell fusion activity of the virus was observed in Molt-4 cells. Hemolytic activity was enhanced by freeze-thawing. Several species of mammals and birds were susceptible to experimental infections with the virus as evidenced by seroconversion and positive virus isolation without showing any clinical signs.

Isolation of orthomyxoviruses from migrating and domestic ducks in northern Japan in 1976--1977

Ortho- and parmyxoviruses were isolated at high frequencies from cloacal and tracheal samples of 334 domestic and 161 migrating ducks in Miyagi and Akita Prefectures, Japan, in the winter of 1976--77. Forty-four hemagglutinating agents were isolated from these ducks. The frequency of virus isolation was much higher from the cloacal samples (6.3%) than the tracheal samples (2.6%). However, no significant difference was found in the isolation ratio between the domestic (7.8%) and migrating (6.8%) ducks. Nine strains of the hemagglutinating agents were identified as influenza A viruses and confirmed to be in pure form by complement-fixation (CF) tests and from their polypeptide profiles. The antigenic characterization of the influenza A viruses revealed the presence of several subtypes; Hav5Nav-2-3, Hav6Neq2, Hav6N2, Hav7Neq2 and Hav7N2.