Migrating animal species: Carriers, hosts, and vectors

Increased emergence of disease may be attributable to altered transmission rates (through altered frequency of interaction of or increased density of possible hosts) and altered host susceptibility due to lowered bodily resilience.⁹⁷ Translocation of animal species, either as vectors or hosts, and increased susceptibility of non-carrier animals (that is, animals which have disease) either directly or indirectly have a role in increasing the spread of disease. Warmer weather animals are being given expanded ranges, moving further North in the case of the Arctic, in particular, into areas previously dominated by endemic fauna such as polar bears.⁹⁸

Migration to higher latitudes of the North and South is particularly evident in the shifting faunal boundary and the movement of fish species.⁹⁹ An inability of Antarctic or Arctic fish to move as they have evolved to exist at certain temperature ranges such as the absence of a heat-shock response in Antarctic notothenioids due to genetic depletion in response to living in a psychrophilic environment.¹⁰⁰ Fish migrate North as the water warms, temperature increases more profitable to those species from more temperate waters as well as faster growing species such as saffron cod over arctic cod.¹⁰¹ The increasing translocation of fish species further North has been documented as boreal fish move into unexploited Northern waters¹⁰² and there is increasing interaction at the Atlantic-Pacific fish interchange.¹⁰³ Subboreal species like boreal beaked redfish and the Arctic-boreal Bering flounder, will likely move North¹⁰⁴ and boreal Atlantic cod already inhabits the Barents Sea.¹⁰⁵ Among other species are increased frequency of movements of marine birds and mammals due to retreating sea ice between Atlantic and Pacific Oceans; there have been sightings of species in each basin not previously known to be there.¹⁰⁶ Northern Gannet and Manx Shearwater, usually restricted to the North Atlantic were seen in Alaska in 2011 for the former and the North Pacific for the latter.¹⁰⁷

As temperatures warm, “[n]ew habitats will be colonized and distinct populations and species will mix as the reduced sea ice allows increased exchange across the Arctic”.¹⁰⁸ Range expansion of temperate species into higher latitudes of the Arctic have been evidenced, for example, with Mytilus spp. mussels, with a demonstration of cleargenetic difference between populations in Greenland and Eastern Atlantic of the same species of mussels, Mytilus edulis.^w> Other species have been found distinctly elsewhere such as Mytilus trossulus in high Arctic NW Greenland and Mytilus galloprovincialis in SW Greenland, Svalbard, and the Pechora Sea.¹¹⁰ Evidence has also been found of hybridisation amongst mussel species in the High Arctic which may suggest adaptations over time to foster resilience.¹¹¹

Range expansion is also true of pathogens, which translocate either along with their hosts, or in surrounding water and air. This will influence reciprocal exchange of parasites among different populations of hosts.¹¹² Toxoplasma gondii have been increasingly found in Arctic marine mammals and Phocine Distemper Virus, which historically affected Arctic dwelling seals, infect more temperate populations.¹¹³ According to McKeon et al., the current era in the higher North is the “largest faunal exchange event to occur during the historical era”.¹¹⁴ Range expansions of, for example, Aspergillus fumigatus, a fungus isolate discovered in birds’ nests in Antarctica, raised a question about the possible dispersal of this microbe (which is pathogenic to humans) by migratory bird species.¹¹⁵

Migrating vectors may take the form of a migrating animal or insects which are normally constrained geographically based on air and/or terrestrial thermoclines. Burek et al. ascribe the emergence of infectious disease to four factors, one of which is carrier host and vector range expansion.¹¹⁶ Indeed, pathogens increase in range as “the insects and other vectors that carry them enter new ecological zones”.¹¹⁷

Ballast water from ships

Polar shipping routes (“Polar Shipping routes”) are on the increase.¹¹⁸ Further sea-ice reduction coincides with and encourages increased transport by ships across the Arctic¹¹⁹ with Antarctica set for the same trajectory. Shipping routes overlap with wildlife corridors.¹²" The role of shipping companies, in particular, and the carriage of pathogens in ballast water, as anti-fouling and in shipping containers among crops, grain, and other goods that harbour pathogens will be carried into higher latitudes as ships push the boundaries of high latitudes both North¹²¹ and South.

Fomite transfer and increased human activity

Increased human movement into the Arctic also increases the rate of spread, both by humans themselves and through industry, environment/

Emerging pathogeneses at the poles 23 land use alterations, noise pollution through seismic activity,¹²² and through engagement with animals previously naive either to human habitations in toto or non-indigenous human habitations. For example, ungulate parasites have changed due to human-led introductions due to changing demographics: “human-mediated translocation, introduction and establishment of hosts and parasites over the past century have altered the distributions for helminths and other pathogens in some carnivores and ungulates”.¹²³ These changing patterns of human movements and migration also have historical links and have affected infection pressures for pathogens where humans and animals come into contact.¹²⁴ In turn, this affects food security and safety, with increasing prevalence and altered transmission routes in traditional food sources such as muskoxen and caribou.¹²⁵

Land use change

With a warming climate comes land use change, not just through extended shipping enterprises but also through the opening of mining, tourism and new food-production and agricultural initiatives:

“the quest for petroleum and other hydrocarbons comprises two successive phases: search and extract. The latter phase is associated with biological consequences of leakages into the environment, hardly known for Arctic waters, and polar cod has become a sentinel species in studies of Arctic marine pollutants and their toxicity”.¹²⁶

In the Arctic petroleum exploration activities and fisheries, there are crucial new resilience-testers¹²⁷ and it has been found that adult female polar bears (Ursus maritimus) had various levels of contamination with organochlorine pesticides (OCPs) across the Arctic from regions of Svalbard, Franz Josef Land, Kara Sea, East Siberian Sea, and Chuckchi Sea.¹²⁸ The additional use of new technologies to monitor and aid reindeer migration as they are moved between pastures also is an additional burden.¹²⁹ This may be either due to overcrowding of reindeer herds and the associated increase in disease transmission rates¹³⁰ or possibly through increased human activity and fomite transfer.

Failure of harmonisation of food safety standards

Harmonisation of food safety standards is the aim of the Sanitary and Phytosanitary Measures (SPS)Agreement Article 3. This is discussedin Chapter 3 and refers broadly to the adoption by Members of standards based on the same standards, as approved by international bodies. The failure to have similar standards may result in the adoption of lower standards and resultant increasing pathogenic risk.