Universidad de Buenos Aires Facultad de Ciencias...
Infection with Influenza A virus (IAV) is considered the major cause of respiratory disease in pigs. Moreover, is a zoonotic disease posing a risk to Public Health. In Argentina, although there were specific serological reports, the first isolation of IAV in pigs was a fully human H3N2 subtype in 20...
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| Formato: | Tesis doctoral acceptedVersion |
| Lenguaje: | Español |
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Universidad de Buenos Aires. Facultad de Ciencias Veterinarias
2016
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| Acceso en línea: | http://repositoriouba.sisbi.uba.ar/gsdl/cgi-bin/library.cgi?a=d&c=avaposgra&cl=CL1&d=HWA_2517 https://repositoriouba.sisbi.uba.ar/gsdl/collect/avaposgra/index/assoc/HWA_2517.dir/2517.PDF |
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| Sumario: | Infection with Influenza A virus (IAV) is considered the major cause of respiratory disease in pigs. Moreover, is a zoonotic disease posing a risk to Public Health. In Argentina, although there were specific serological reports, the first isolation of IAV in pigs was a fully human H3N2 subtype in 2008. Then, an H1N1pdm09 subtype, associated with a human pandemic, was isolated and multiple clinical cases in pigs were reported. For these reasons the general objective of this study was to characterize the strains of IAV circulating in pigs in Argentina and the forms of presentation of the infection. Clinical, pathological, serological and virological studies in nine intensive pig farms were performed. The results demonstrated a clinical-epidemiological enzootic presentation in 8 animal farms between 21 and 50 days. From the pathological point of view, the most frequent lung injury was suppurative bronchopneumonia with necrotizing bronchiolitis. Serological studies showed two patterns. In one of them a decrease in colostral antibodies between 21 and 49 days and a subsequent marked increase in the percentage of positive animals (20-80%) was observed. This pattern was associated with an active virus circulation. In contrast, the other pattern showed a low percentage of positive animals in breeding, less than 50%. In this case the highest percentage of positive pigs in the production line was 20%, which is suggestive of endemic infection with low circulation of IAV. The hemagglutination inhibition test detected H1pdm09, ?H1 and H3 antibodies on all farms. Moreover, the 75% of the animals had antibodies against more than one subtype. It was detected IAV by rRT-PCR in 7 farms, most between 21 and 50 days old, and 5 isolates were obtained. Four of the isolates were characterized as H1N1pmd09 subtype and one as H3N2 subtype.\nClinical and virological studies were also conducted in 12 intensive farms who reported the presence of clinical cases of IAV infection. Clinical inspection determined in 8 farms the clinical-epidemiological enzootic presentation and in 4 farms the epizootic form was observed. The age of presentation of clinical signs was variable being weaning animals the most affected ones (30-40 days). All farms were positive by rRT-PCR and virus detection age coincided with the age of presentation of clinical signs. A total of 13 isolates of IAV were obtained: H1N1pdm09 (7), H1N2 ?2 (3) and H3N2 cluster II (3). Influenza virus circulation was evaluated in small producers and family farmers. A total of 57 farms samples from different regions of the country were taken. Serological studies detected the presence of antibodies against H1pdm09 by more than 60% of farms and 40% of animals, whereas less than 17% of farms and 2% of the animals were positive for H3 subtype. The detection and characterization of IAV from samples sent to the Avian and Swine Laboratory, CICVyA, INTA was performed. Samples of 51 establishments were received from 10 provinces and 27 isolates were obtained. The 70% of the isolates were characterized as H1N1pdm09. In addition, isolates of ?2 H1N2; ?2 H1N1; ?1 H1N1 and H3N2 were obtained.\nPhylogenetic analysis of all the isolates (N = 45) showed a predominance in the circulation of H1N1pdm09 subtype. Only five isolates were characterized as H3N2 cluster II subtype, 8 as ?2 H1N2 subtype, one as ?2 H1N1 subtype and the remaining one as ?1 H1N2 subtype. All of them have pandemic M gene and external genes from human seasonal IAV. Nine IAV introductions from human to pigs were detected. Seven of them were related with the H1N1pdm09 and two with human seasonal H1 and H3 that were circulating more than a decade ago.\nAntigenic mapping studies showed that, despite the similarity at the genetic level in the virus detected in the country, the antigenic differences are marked.\nIAV infection is widespread in pigs of our country. In most farms evaluated the enzootic presentation (subclinical) was observed. These results warn about the possible generation of reassortants virus and the presence of a variable percentage of pigs without antibodies against IAV that would allow persistent infection.\nAll subtypes of IAV circulating in pigs in Argentina correspond to introductions of viruses of human origin, in some cases related to circulating strains over a decade ago. This highlights the importance of humans in epidemiology of IAV in pigs in our country and poses a risk to the human population because of the possibility of reintroductions.\nThe information generated in this study shows that circulating subtypes in the country do not correspond to those reported in North America and Eurasia. This fact, coupled with the high antigenic variation observed and the rapid evolution of IAV, warn the need to develop local immunogens and diagnostic tests that allow proper control of IAV in pig farms in our country. |
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