In a belated report USDA confirmed that a sample of house mice (Mus musculis) “tested positive” for avian influenza H5N1. USDA was aware of the isolation on May 8th and delayed disclosure including release of genetic sequence data. Epidemiologists and virologists including Dr. Rick Bright have justifiably criticized USDA for their opacity.
House mice add to the list of mammals susceptible to H5N1. The significance of this species lies in their close association with human habitation. Mice are capable of disseminating viral pathogens over wide distances and as with Salmonella Enteritidis in production complexes may result in persistence of virus depending on duration of shedding. Rodents are associated with numerous infections including pasteurellosis, salmonellosis, tularemia, yersiniosis, leptospirosis, Lassa fever, Hantavirus infection and other exotic viruses.
Epidemiologists have called for extensive and comprehensive surveillance to determine the extent of infection among mice populations on chicken, dairy and other livestock farms.
Informed commentators have expressed concern over the spread of H5N1 to mammals.
Experimental infection of laboratory mice wit Dairy herd isolate of H5N1 |
Professor Vincent Savolainen at the Imperial College, London noted, “Health authorities are playing catch-up every time the virus jumps to a new species, but we need to start becoming proactive.” Dame Sarah Gilbert, Professor of Vaccinology at the Pandemic Sciences Institute, Oxford University, noted, “the information coming out the U.S. on H5N1 is concerning” and she urged the vigilance.
A ProMED moderator (PMB) noted that H5N1 has become endemic in many regions of the world affecting livestock, poultry, and free-living animals. Extensive mortality among seals and sea lions along the Pacific coast of South America and breeding colonies in Antarctica in addition to a case of farmed mink in Spain suggest mammal-to-mammal transmission. This raises the possibility of cow-to-cow contagion that is currently under investigation in Germany and presumably later in the U.S. If in fact mouse-to-moue transmission of H5N1 is a reality, this could represent the potential for a new reservoir creating problems in controlling the infection and increasing the risk of human exposure.