Maternal antibody-mediated elimination of a Puumala hantavirus outbreak in a bank vole colony

Bank voles (Myodes glareolus syn. Clethrionomys glareolus) are frequently used as an animal model in ecological and biomedical studies and are an important reservoir of viral and bacterial zoonotic pathogens, e.g., Puumala hantavirus (PUUV). Here we describe an accidental PUUV outbreak in a large bank vole laboratory colony caused by an accidental introduction of infected wild-trapped bank voles, and the successful eradication of the virus. The eradication plan was based on results of previous studies showing that maternal antibodies (MatAb) protect the young from infection for up to 40 days after weaning, four weeks longer than the estimated duration of PUUV infectivity in the environment. After ensuring that most animals were infected, 620 pairs were mated on the same day. Only females that showed PUUV-specific antibodies and produced offspring within 26 days after mating were retained. All individuals of the parental generation were euthanized before the last weaning. The weaned offspring were moved to individually ventilated cages (IVC) and repeatedly tested for the presence of PUUV-specific antibodies and RNA. A few infected or suspect animals were euthanized. The animals were then mated (in IVC) and, after producing grand-offspring generation, euthanized and tested for PUUV RNA in the lungs. No PUUV RNA was detected, and no animals showed PUUV-specific antibodies in subsequent generations. The successful clearance confirmed the protective efficiency of PUUV-specific MatAb. The procedure for PUUV clearance in the bank vole colony may represent a blueprint for similar approaches in valuable colonies of other rodents infected by similar pathogens.