Prevalence of antibodies to swine influenza viruses in humans with occupational exposure to pigs, Thuringia, Germany, 2008–2009

Abstract

The Eurasian lineages of swine influenza viruses are different genetically from classical swine H1N1 influenza viruses and comprise avian-like H1N1 and human-like H1N2 and H3N2 subtypes. Although sporadic isolation of such viruses from human specimens has been reported, the prevalence of human infections is not known. In the present study, the seroprevalence against Eurasian swine influenza viruses was investigated. Sera were collected in Thuringia, Germany, from December 2007 to April 2009. The study group comprised 118 professionals with occupational exposure to pigs (50 pig slaughterers/meat inspectors, 46 pig farmers, 22 veterinarians caring for pig herds). The control group included 118 age- and gender-matched blood donors from Thuringia. As a result, 18 sera of the study group were identified with raised hemagglutination-inhibition titers against a panel of nine swine influenza viruses (three strains/ subtype). For 17/18 sera this finding was confirmed in the neutralization assay. For 11/18 sera the raise of titers was significant, that is, a fourfold increase of hemagglutination-inhibition titers was observed. No gender-specific bias of the high titer sera was observed. Twelve sera of the control group showed increased hemagglutination-inhibition titers against swine influenza viruses. Hemagglutination-inhibition titers of 2/12 control sera were raised fourfold but did not exhibit a significant increase of neutralization titers. All increased hemagglutination-inhibition titers of the control group may be explained by cross-reactivity with seasonal influenza virus strains, as all these sera also reacted with human strains.

Prevalence of hepatitis E virus-specific antibodies in humans with occupational exposure to pigs

“…The control group consisted of 116 Thuringian blood donors without pig contact which were frequency matched by gender and age (39 years and below, 40-49 years, and 50 years and above). This is in accordance with our previous publication [18]. The study group comprised of 45 women (42.5%) and 61 men (57.5%).…”

“…However, for Germany, such data are currently not available. Therefore, we used a well-characterised set of sera which were initially collected to analyse the risk of zoonotic influenza A virus infection [18]. Some of these samples had to be excluded from the present setting since not enough material was available.…”

“…Sera were collected from December 2007 to April 2009 in Thuringia, Germany, as described previously [18]. One hundred and six sera were available from humans with occupational exposure to pigs (study group).…”

Serological response to influenza A H1N1 vaccine (Pandemrix®) and seasonal influenza vaccine 2009/2010 in renal transplant recipients and in hemodialysis patients

“…Cells were propagated in Eagle's minimum essential medium (EMEM) supplemented with 10% (v/v) fetal bovine serum, 100 U/ml penicillin, 100 g/ml streptomycin and 2 mM L-glutamine. The HI assay was conducted in large accordance to the WHO protocol and according to a study published previously [20]. BrieXy, serum samples were pretreated with (1) neuraminidase (Sigma N-3,001, Taufkirchen, Germany) 1:40 diluted with 0.9% (w/v) sodium chloride for 14-18 hours at 37°C.…”

Weighing serological evidence of human exposure to animal influenza viruses − a literature review

“…The reported seroprevalences differed greatly among studies. In populations occupationally exposed to swine, the prevalence of antibodies to H1N1v ranged from 0% to almost 80% [82,85], to H1N2v from 4% to 67% [72,82] and to H3N2v from 9% to almost 80% [49,72]. Looking only at the high quality studies (grades A or B), the reported prevalences were similar to those for C and D studies, with the exception of H3N2v, for which the highest reported seroprevalence was 28% [74] (Figure 4).…”