engleski

Virological and serological investigation of avian influenza in Black-headed Gulls captured on a rubbish dump in Croatia

A total of 142 Black-headed Gulls (BHGs), Chroicocephalus ridibundus, were captured during February and March 2009 at Zagreb city rubbish dump (45.45 N 16.01 E) in order to collect cloacal swabs and serum samples. Cloacal swabs were tested by virus isolation in embryonated chicken eggs which resulted in isolation of one avian influenza virus(AIV) that was not of H5 or H7 subtype. Collected sera were tested by blocking ELISA for avian influenza antibodies resulting in 28.2% positive samples which were retested by haemagglutination inhibition (HI)using H5 and H7 subtype antigens. Only one serum sample was positive for H5 and none for H7 antibodies. Statistically, no significant difference was found between ages of AIV seropositive birds (χ2= 2.08, df= 1, P=0.15). In contrast, seroprevalence in different months of capturing where higher proportion of positive gulls during March than during February was found (χ2= 4.53, df= 1, P=0.03), especially in younger birds (χ2= 7.67, df= 1, P=0.006). Such finding suggests that BHGs might contract AIV infection during their aggregations in large numbers at rubbish dumps or similar feeding sites during winters. Although only one of 142 tested birds was positive for H5 subtype antibodies, this finding cannot be neglected knowing that apparently healthy BHGs can carry highly pathogenic AIV of H5N1 subtype. Nevertheless, the results of our study have shown that BHGs are more often infected with other AIV subtypes and therefore are most likely not the primary carriers of H5 AIV.

Avian influenza; H5 subtype; gulls; Larus

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