Field study on swine influenza virus (SIV) infection in weaner pigs and sows

Abstract

SummaryObjective: The aim of this field study was to explore the occurrence of and factors associated with the detection of swine influenza virus (SIV) by RTqPCR in weaner pigs and sows from herds with a history of respiratory or reproductive disorders. Material and methods: The sample set was based on nasal swabs from 823 sows (123 submissions) and 562 weaner pigs (80 submissions). Nasal swab samples were taken and submitted by 51 veterinary practices from all over Germany. Corresponding to the pig density most of the submissions ori ginated from the north-western part of Germany. The nasal swabs were used to detect SIV RNA by real-time RT-PCR (RTqPCR). Subtyping of SIV RNA by conventional RT-PCR and sequencing was attempted directly from clinical samples or from isolates when available. The herd characteristics, management and housing conditions of the pig herd as well as the course of the disease were collected by a telephone questionnaire with the herd attending veterinarian. Results: SIV was detected by RTqPCR in 53.8% of the submissions from weaner pigs with a history of respiratory disease. Moreover SIV was detected in 10.6% of the submissions from sows. The predominant endemic subtype found in nasal swabs from sows and weaner pigs was H1N1 (60.5%) whereas subtypes H1N2 (14.0%) and H3N2 (14.0%) were detected less frequently. In addition, human pandemic H1N1 virus or reassortants thereof were found in 11.5%. Conclusion and clinical relevance: The results underline the significance of a SIV infection in young pigs. A significant lower detection of SIV in weaner pigs was associated with the vaccination of piglets against porcine circovirus type 2 (PCV2), possibly indicating an interaction of SIV and PCV2. Most of the positive samples from sows originated from gilts, whereas only two originated from sows. An association between reproductive disorders and the detection of SIV could not be confirmed.

Association between Influenza A Virus Infection and Pigs Subpopulations in Endemically Infected Breeding Herds

“…Therefore new gilts and piglets may represent the most epidemiologically significant reservoirs for IAVs in swine breeding herds. Sows were not included in our study because they have been found to have a low probability of influenza positivity in endemically affected herds [15, 19, 20]. Our results also indicate that there was a strong association between IAV infection and annual quarter and that this association was still statistically significant after controlling for the subpopulation effect.…”

“…At each visit, three pig subpopulations were sampled: a) replacement females, resident on-farm for less than 4 weeks (new gilts), b) replacement females, resident on-farm for more than 4 weeks (gilts), and c) neonatal pigs less than 21 days of age (piglets). Adult animals (sows) were not included since prior studies consistently reported a low probability of influenza detection in this subpopulation [15, 19, 20]. Due to schedules for delivery of replacement females, eligible populations of new gilts were only present at 21 of the 60 sampling events.…”

“…As a result, breeding populations have high rates of turnover, and associated fluctuations in herd’s susceptibility to IAV infections. Previous studies have shown that it is not easy to recover IAVs from sows [15, 19, 20]. However, the dynamics of IAV infection among other subpopulations (gilts and suckling piglets) may influence the maintenance of IAVs in the breeding herd or contribute to the emergence of novel strains.…”

Reproductive performance of pandemic influenza A virus infected sow herds before and after implementation of a vaccine against the influenza A (H1N1)pdm09 virus

“…Independent of the subtype, the disease can emerge both in a subclinical and in an acute way, with varying severity, showing febrile illness together with respiratory disease [4,8,11]. An involvement in reproductive disorders, such as return to oestrus, abortion or small litters, is assumed, although a causal link could not be shown in all studies [12,13]. Numerous case reports as well as a case-control study on a naive Norwegian pig subpopulation describe the emergence of reproductive disorders in context with the infection with influenza A virus [14][15][16][17].…”

Influenza-Ausbruch bei Aufzuchtferkeln unter Beteiligung von Mycoplasma hyorhinis und Haemophilus parasuis

“…Der in Schweinepopulationen häufig endemisch vorliegende Subtyp H1 av N1 wurde Ende der 1970er Jahre von wildlebenden Wasservögeln auf Schweine übertragen und infiziert seitdem viele Schweinebetriebe endemisch (35). In Deutschland untersuchten Meiners et al (22) annähernd 600 Nasentupfer von Absetzferkeln mit Atemwegserkrankungen aus dem gesamten Bundesgebiet und konnten bei insgesamt 54% der Tiere FLUAVsw nachweisen. Bei 60,5% der Isolate handelte es sich um H1 av N1, bei jeweils 14% um H1N2 und H3N2 sowie bei 11,5% um H1N1pdm.…”