Two new papers have become available:
Experimental Infection of Cattle with Highly Pathogenic Avian Influenza Virus (H5N1) [link] Donata Kalthoff, et al.
Four calves were experimentally inoculated with highly pathogenic avian influenza virus A/cat/Germany/R606/2006 (H5N1) isolated from a cat in 2006. All calves remained healthy, […] All calves seroconverted.
Since 1997, an epidemic of highly pathogenic avian influenza virus (HPAIV) subtype H5N1 has spread in Asia, causing fatal infections in poultry, wild birds, and mammals, including humans (1). Knowing the susceptibility to HPAIV (H5N1) of mammalian species living in close proximity to humans and poultry, such as members of the family Bovidae (e.g., cattle or water buffalo), would be helpful to those developing surveillance plans or determining risk areas.
Domestic Pigs Have Low Susceptibility to H5N1 Highly Pathogenic Avian Influenza Viruses Aleksandr S. Lipatov, et al. [link]
Genetic reassortment of H5N1 highly pathogenic avian influenza viruses (HPAI) with currently circulating human influenza A strains is one possibility that could lead to efficient human-to-human transmissibility. Domestic pigs which are susceptible to infection with both human and avian influenza A viruses are one of the natural hosts where such reassortment events could occur. Virological, histological and serological features of H5N1 virus infection in pigs were characterized in this study.
Those who are interested, and have not done so yet, can read the papers in their entirety at the links, both are public access.
I found the two papers coming out at roughly the same time to be helpful in pointing out the differences in experimental infection routes (cows – intranasal and pigs –infected food). Infection doesn't just happen by airborne transmission, H5N1 can, and does, seem to take advantage of any route into a host, whether that's through inhalation or ingestion, with hints that open cuts and abrasions may offer an entrance because H5N1 can and does survive in the blood, as well as via the eye.
It is also logical that not all routes of infection pose the same level of risk, nor pathological profile. For instance, digestive tracks have evolved to handle many pathogens from less than sanitary food. Obviously, it's not 100% effective, but generally it's a very inhospitable environment. Eyes, although exposed to the air are a more "isolated system", independent of most of the rest of the body. Though ocular epithelial cell infection is suspected in the one fatal case of H7N7 in the Netherlands in 2003. It seems the nasolacrimal duct drains into the nasal cavity, so in the case of influenza "more isolated" doesn't translate 100% to no infection risk.
It's possibly worth noting that many of the nurses infected during Canada's SARS outbreak were infected during intubation of SARS patients without wearing eye protection to guard against aerosolized virus. Eventually this practice was recognized as a huge gaping hole of risk, and the nurses wore goggles and their infection rates plummeted. Of course, that may be coincidental since stringent bio-security was implemented across all possible routes of infection. That said and acknowledged however, prior to the goggles, other PPE (personal protective equipment) such as gloves, masks/respirators, and hand washing were in place.
It was the recognition of the extra risk the aerosolized virus posed and utilization of eye protection that would support the goggles making a statistically significant difference in new infections.
So much to learn, so much we don't know, which is why funding and performing these experiments are vitally important.
I wonder if anyone has thought to perform an experiment of ocular infection with H5N1 of piglets. Hint – hint if not.