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Biomedical subjects

B C Easterday

Publications and source records attributed to B C Easterday.

At least 55 records · Page 3Linked to original sources
PubMed1972

Swine influenza: epizootiological and serological studies.

Studies of naturally occurring respiratory diseases in the midwestern parts of the USA showed that swine influenza is still prevalent and that mild forms as well as the classical forms of swine influenza occur. Outbreaks of respiratory disease of unknown etiology that are clinically similar to swine influenza were also found. On some farms, swine influenza occurred first in farrowing pens. It did not occur on some farms where the disease had occurred in previous years. This disappearance may have resulted from the elimination or hyperimmunization of breeder animals or from a change to the raising of swine obtained by caesarean section. Serological studies of swine with natural or experimental infections showed that antibody titres rose gradually for several months. This observation was corroborated in serological studies of sera obtained at the abattoir, which showed that older breeder swine had consistently higher titres than the younger market swine. These results cannot be explained by the lungworm hypothesis proposed by R. E. Shope for the survival and transmission of swine influenzavirus. It is suggested that breeder swine act as convalescent carriers and as the reservoirs of swine influenzavirus between epizootics.

Animals↗
PubMed1972

Hong Kong influenza infection in swine: experimental and field observations.

The recovery of influenzaviruses indistinguishable from A/Hong Kong/68 virus from pigs in Taiwan in 1970 provided the first direct evidence of the interspecies transfer of influenzaviruses. Pigs were infected experimentally with that virus and transmitted the virus to pen mates. There was no evidence of A/Hong Kong/68 antibodies in serum collected from pigs prior to 1968. Such antibodies were detected in serum collected from pigs that lived during the period when Hong Kong influenza was epidemic in the human population.

Animals↗
PubMed1972

A new subtype of avian influenzavirus: antigenic characteristics of envelope antigens.

The haemagglutination and neuraminidase antigens of three influenza A isolates from ducks in the Ukraine were compared with those of a collection of reference strains of influenza A virus. Duck/Ukraine/1/60 virus contained haemagglutinin related to that of duck/England/56 while its neuraminidase was related to that of turkey/Wisconsin/68 virus and the human A/Hong Kong/1/68 virus. Duck/Ukraine/2/60 and duck/Ukraine/1/63 were themselves closely related. They contained haemagglutinin antigens unrelated to the six haemagglutinin subtypes previously described for avian influenzaviruses and it is suggested that they should be classified as belonging to haemagglutinin subtype Hav7. The neuraminidase antigens of these isolates were antigenically related to those of a number of other avian influenza viruses isolated in England, Canada, and Italy and to that of A/equine/ Miami/63 virus.

Animals↗
PubMed1972

Influenza in Canada geese.

The role of wild avian species in the natural history of influenza is unknown. A serological study was carried out to ascertain the prevalence, distribution, and types of influenza antibody in several wild Canada goose populations. Geese were trapped and blood samples were obtained in each of 4 consecutive years, 1966-69. Antibody to influenzavirus was found in 66 (4.7%) of the 1 401 Canada geese tested by the haemagglutination inhibition (HI) test. Antiribonucleoprotein antibody was found in 8 of 1 359 sera tested by the agar gel precipitation (AGP) test. An increase in the percentage of reactors was seen each year. This increase was greater in two refuges with nonmigratory flocks. HI antibody was found against the turkey/Wisconsin/66, turkey/Wisconsin/68, turkey/Canada/63, and turkey/Alberta/6962/66, or closely related viruses. No antibody was found against duck/Ukraine/1/63 or human A/Hong Kong/68 virus at a time when the latter was prevalent in human populations, suggesting that Canada geese played no direct role in spreading the virus.Canada geese were experimentally exposed to turkey/Wisconsin/66 and turkey/Wisconsin/68 viruses; mallard ducks were exposed to turkey/Wisconsin/66 virus. HI antibody developed in 75% of the geese and 40% of the ducks but was generally short-lived. Anti-RNP antibody was detected in 15% of the exposed geese but in none of the ducks. Virus was recovered from 3 of 10 adult ducks but not from geese. None of the birds showed signs of disease.

Animals↗
PubMed1972

Host response differences among 5 avian species to an influenzavirus--A-turkey-Ontario-7732-66 (Hav5N?).

Experiments were carried out to determine how turkeys, ducks, quails, pheasants, and pigeons respond to the same avian influenzavirus (A/turkey/Ontario/7732/66). The factors considered were the antibody response, virus shedding, and overt signs of disease. While no signs of disease were observed among the pheasants and ducks, turkeys had severe disease that terminated fatally. There was a marked antibody response in the pheasants and quail and a poor response in ducks. The ease and regularity of virus recovery varied considerably. The marked differences between species in the response to infection with avian influenzaviruses should be taken into account in the design and interpretation of studies of the role of avian species in the natural history of influenza.

Animals↗
PubMed1972

Light and electron microscopic changes in the myocardium of influenza-infected turkeys.

Virus isolation and titration, electrocardiography, enzyme assays and light and electron microscopic studies were undertaken in male turkeys infected with influenza A/turkey/Ontario/7732/66 virus to determine its potential role in the genesis of heart disease. Virus was isolated from the heart initially before a demonstrable viremia and terminally in declining serum viral titer. Virus was isolated from the heart muscle as early as 1 day postinoculation. Highest viral titers were found in the heart at 6 days postinoculation and coincided with maximum elevations of serum glutamic-oxalacetic transaminase and lactic acid dehydrogenase, microscopic lesions in the heart and cardiac arrhythmias. Microscopic lesions in the heart were first detected at 4 days postinoculation and consisted of disseminated areas of necrosis, focal myocarditis, pericarditis and endocarditis. Alterations in myocardial ultrastructure which followed viral infection included fragmentation and dissolution of myofibrils, dilation of the sarcotubular system, increase in membrane vesicle formation in the region of the endoplasmic reticulum, discontinuity of the sarcolemma, proliferation of mitochondrial population, swelling of mitochondria with separation and disruption of the cristae, and the presence of intramitochondrial and perinuclear densities.

Animals↗
PubMed1969

Relationship of envelope antigens of animal influenza viruses to human A2 influenza strains isolated in the years 1957-68.

This study demonstrates relationships in envelope antigens of 4 human influenza A2 strains isolated during the period 1957-68 (including A2/Hong Kong/68), 2 strains of A/Equi-2/63 and 7 avian influenza viruses isolated in Europe, North America, and the Ukraine in the years 1960-67.Antigenic relationships among the strains were determined on the basis of haemagglutination-inhibition, virus-neutralization, strain-specific complement-fixation, and neuraminidase-inhibition tests.North American avian influenza strains, Turkey/California/64, Turkey/Massachusetts/65, Turkey/Wisconsin/66, Turkey/Ontario/6828/67, and the Italian strain Duck/Italy/574/66 are antigenically related to human A2 influenza viruses by haemagglutinin and/or neuraminidase. None of these viruses is antigenically related to the A/Equi-2/63 strains, Duck/Ukraine/2/60, Duck/Ukraine/1/63 or A2/Hong Kong/68. However, A2/Hong Kong/68 has neuraminidase similar to other A2 strains from previous years.A definite relationship was shown between the haemagglutinin of A/Equi-2/63, A2/Hong Kong/68, Duck/Ukraine/2/60 and Duck/Ukraine/1/63 strains by the use of hyperimmune sera in 3 different serological tests. Related neuraminidase was demonstrated only between A/Equi-2/63 and both duck strains from the Ukraine.The significance of these findings and their interpretation with respect to the ecology of influenza viruses are discussed.

Animals↗