What happens next with bird flu? An expert explains why monitoring matters

What happens next with bird flu? An expert explains why monitoring matters Swati Mestri Scientific Editor Andrew Zinin Chief Editor The lethal H5N1 strain of avian influenza is rapidly spreading along the coast of southern Australia, where it has killed thousands of wild birds and infected at least two long-nosed fur seals. So where will it travel next, and what damage might it inflict? Much is uncertain, especially because many of Australia's animals and ecosystems are so unlike those in other parts of the world. But monitoring is vital if we are to understand the magnitude of this H5N1 outbreak and protect our most vulnerable species, including the threatened Australian sea lion. What may be coming It's difficult to know how Australia's current H5N1 crisis will unfold. But we can make four predictions based on existing knowledge. Waterfowl will carry the virus inland Infected waterfowl from coastal southern Australia—such as ducks, herons and swans—will soon carry H5N1 to inland wetland systems. The timing is terrible. In coming months, the hot and dry conditions created by the El Niño climate pattern will cause those wetlands to shrink. This means vast numbers of waterfowl, already debilitated by scarce resources, will congregate at the few remaining water sources. Weak flow and high densities of dead and dying birds will turn this water into a virus-contaminated soup, leading to further losses. Macquarie Island's wildlife will suffer major losses To date, the significant colonies of seabirds, seals and king penguins on Macquarie Island have escaped the virus. However, H5N1 has devastated similar colonies on many other subantarctic islands, such as Kerguelen and Crozet islands. Macquarie's luck will soon run out, leaving its densely packed colonies of penguins, seals and petrels extremely exposed. In response to this threat, the Australian government has evacuated researchers from the island to protect their physical and psychological health. Shearwaters will be widely infected Within a few weeks, vast flocks of shearwaters will return from their global migration to nest on islands off southern Australia, such as those in Bass Strait. Bird flu, likely carried by other seabirds, will await them there. Losses may be substantial. Scavengers will carry the virus beyond the coast and wetlands Foxes, roaming cats, mynas and other scavenging animals will bring H5N1 to our cities. This will have far-reaching impacts on urban wildlife, such as magpies and possums, consistent with declines of urban species overseas. There is hope However, it's not all doom and gloom. Bird flu has not yet caused extinction of any species elsewhere in the world. And after the initial outbreak, some affected species have started to recover—in some cases because survivors have stronger immunological responses. This should happen in Australia too. What is critical now is assessing the conservation impacts of H5N1 on our wildlife. Counts of dead birds tell us something about the flu's spread and virulence. But while every death is saddening, corpse tallies alone don't reflect conservation impact. For example, thousands of greater crested terns have been killed by H5N1, but these deaths represent a fraction of the global population, estimated to number between 150,000 and 1.1 million. In contrast, there are only about 3,000 Christmas Island frigatebirds in existence, so any losses would be disastrous for that population. What's more, counts of deaths can be unreliable because many corpses may never be discovered. Instead, governments should focus on the proportion of a species' total population that is killed by bird flu. This will allow us to assess the conservation consequences and, over time, the extent of recovery. Assessing impact is not always straightforward However, population-level impacts may be challenging to assess. We have good estimates of population sizes for only a few Australian animal species. Fortunately, this includes some species that are most vulnerable to H5N1, including colonial-breeding seabirds and seals. Without these data, monitoring can be used to estimate population density at a series of sampled sites or the incidence of certain bird species. Some current monitoring programs, such as the long-running aerial survey of waterfowl across eastern Australia, could provide critical data about the impacts of bird flu. Interpreting monitoring data can also be complex. In inland Australia, the numbers of many species bounce around, particularly when the weather fluctuates between wet and dry conditions. With this statistical "noise," identifying any population declines caused by bird flu is difficult. There are biases and gaps in monitoring data. Most native mammals are not monitored, so we may have no idea how many die from H5N1. Losses in birds found in remote areas, such as the Heard Island black-faced sheathbill, are also likely to be missed due to a lack of regular monitoring. Where to from here To understand the nuanced impacts of H5N1 bird flu, monitoring should assess the effectiveness of management actions, changes in breeding success and levels of immunity, mutations and the virulence of the virus itself. It should also investigate survival rates of infected individuals, the broader environmental risks of losing large numbers of key species and the extent of recovery. Recovery may be harder and take longer for species that have low breeding output and take many years to mature, such as albatrosses. Without effective monitoring, we will not grasp the true magnitude or significance of the current H5N1 outbreak. It's what we need both to target emergency responses to the most affected species and measure the extent to which our actions are actually helping. Provided by The Conversation This article is republished from The Conversation under a Creative Commons license. Read the original article.