Detection of Virus Genome on Animal Surfaces and in Litter in the Course of Outbreaks with Low-Pathogenic Avian Influenza

Infection with low pathogenicity avian influenza (LPAI) viruses is widespread in the European Union (EU). Outbreaks of LPAI (H5 or H7) in poultry are often controlled by culling affected flocks to avoid a further spread of the disease. However, derogation from the depopulation principle is possible if a risk assessment comes to the conclusion that the risk of further spread is minimal. Little is known about the distribution of LPAI viruses within flocks, the extent of environmental contamination and the tenacity of the virus under field conditions. This gap in knowledge also leads to uncertainties in risk assessments. The aim of the study was to determine the extent of LPAIV contamination of litter and animal surfaces (feathers, feet) in the case of an LPAI outbreak. In total, 415 samples of litter, feathers and feet were collected immediately after culling of three LPAI (H7N7) infected turkey herds. In addition, 180 combined tracheal and cloacal swabs were taken from the turkeys. All samples were diagnosed by H7 specific RT-PCR. The highest proportions of positive samples were found in litter (up to 85.9%). The results for the combined swabs were similar, while the percentage of positive foot and feather samples was lower (up to 18.3% or 5.0 %, respectively). There is substantial contamination of litter and to a lesser extent also of the animal surface with LPAI virus genome. Slaughtering such animals and processing them for human consumption conventionally can therefore not be recommended. Further investigations are needed to determine the persistence of contaminating influenza virus and its infectivity.