Figure Of Bay Of Bengal Food Chain

Land management practices J^

Urban areas

Urban areas

Climate Interconnectedness
FIGURE SA-8 Interconnectedness of terrestrial, aquatic, and marine food webs. SOURCE: Figure courtesy of Mary Ruckelshaus, NOAA Fisheries.

greater investments in collaborative efforts to monitor, model, and research these connections.

Water-borne human disease The incidence and distribution of food- and waterborne diseases are shaped by numerous factors, including climate variation, water temperature, precipitation patterns, and/or water salinity. Extreme weather events, including heavy rainfall and flooding, are associated with outbreaks of several important water-borne diseases (NRC, 2001). These include cholera, an acute diarrheal illness caused by the bacterium Vibrio cholerae (CDC, 2005); crypto-sporidiosis, one of the most common water-borne diseases in the United States, caused by microscopic parasites of the genus Cryptosporidium (CDC, 2007a); and giardiasis, another diarrheal illness common in the United States, which is caused by the single-celled parasite Giardia intestinalis (CDC, 2004). Soil washed into coastal waters by floods contains animal wastes (and, therefore, fecal bacteria) as well as other organic matter and nutrients that promote rapid growth, or "blooms," of certain toxic algae species. These harmful algal blooms (also known as "red tides") produce neurotoxins that can be transferred through the marine web—killing some marine animals along the way—to seafood-consuming humans (Woods Hole Oceanographic Institution, 2008).

26 GLOBAL CLIMATE CHANGE AND EXTREME WEATHER EVENTS

BOX SA-2 Emerging Infectious Diseases in the Aquatic-Marine Continuum

The following infectious diseases, described by workshop speaker Leslie Dierauf of the U.S. Geological Survey's National Wildlife Health Center, are of considerable concern in freshwater, intertidal, and marine wildlife, due to recent increases in incidence and/or geographic range, as well their potential to disrupt aquatic and marine ecosystems.

Freshwater Zone

• Ranavirus, within the family Iridoviridae, is a skin-destroying viral pathogen that infects North American amphibians (see Figure SA-9);

Infected

Normal

FIGURE SA-9 Ranavirus-associated disease in frogs. SOURCE: USGS; Dierauf (2007).

• Viral hemorrhagic septicemia (Rhabdoviridae novirhabdovirus) is a newly discovered viral disease associated with large-scale mortality of many common fish species. The virus is able to survive in warm and cold waters and in estuarine and marine waters, as well as in freshwater systems (see Figure SA-10);

FIGURE SA-10 Viral hemorrhagic septicemia (VHS) Rhabdoviridae novirhabdovirus. SOURCE: USGS; Dierauf (2007).

SUMMARY AND ASSESSMENT 27

• Chytridiomycosis (Batrachochytrium dendrobatidis) is a fungal infection of not only North American frogs, but is now being detected worldwide (see Figure SA-11); and

• A Perkinsus-like protozoal organism has been identified as causing fatalities in tadpoles of several North American frog species (see Figure SA-12). Discovered in 1999, this pathogen decimates frog populations and is thought to be adapted to warmer temperature waters.

FIGURE SA-11 Chytridiomycosis (Batrachochytrium dendrobatidis) in Chiricahua leopard frog (New Mexico). SOURCE: USGS; Dierauf (2007).

FIGURE SA-12 Perkinsus—wood frog (Rana sylvatica) tadpole with massively enlarged yellow liver. SOURCE: USGS; Dierauf (2007).

Intertidal Zone

• Another Perkinsus-like protozoan species that infects frogs.

• Various species of Vibrio bacteria the food chain to birds and mammals,

Marine Zone

FIGURE SA-12 Perkinsus—wood frog (Rana sylvatica) tadpole with massively enlarged yellow liver. SOURCE: USGS; Dierauf (2007).

affecting oysters—may be related to the that infect shellfish and are transmitted up including humans.

• The acceleration of coral bleaching by opportunistic infections during periods of elevated temperature (Harvell et al., 2002). Coral bleaching occurs when, under extreme environmental stress, corals expel their symbiotic algae. In 1997-1998, a dramatic global increase in the severity of coral bleaching coincided with El Niño (Harvell et al., 1999).

28 GLOBAL CLIMATE CHANGE AND EXTREME WEATHER EVENTS

A complex web of ecological relationships is involved in the incidence and prevalence of cholera, which Colwell estimated affects 100,000 people per year and kills 10,000 (see Colwell in Chapter 2). Over the course of three decades of study, she and coworkers have determined that this water-borne disease, although caused by a bacterium (V. cholerae), is actually transmitted by the plankton species with which it associates (Colwell, 2004). Vibrio cholerae is a natural inhabitant of aquatic environments of appropriate salinity, but remains quiescent except when temperatures rise above 15°C, and an influx of nutrients causes the plankton to bloom, increasing V. cholerae concentrations to levels capable of causing disease when water is consumed. This relationship is sufficiently robust to permit the use of remote sensing data—incorporating sea surface temperature, sea surface height, and chlorophyll levels (an indicator of phytoplankton bloom) observed in the Bay of Bengal—to predict the onset of cholera epidemics in the Ganges delta region of Bangladesh, known as the "home of cholera" due to its long history of epidemic disease.

Primarily confined to the Indian subcontinent, cholera was spread by the shipping trade from India to Europe and the Americas in the early nineteenth century (Colwell, 2004). Subsequent improvements in sanitation drastically reduced cholera incidence in the West, but the disease reemerged in Peru in 1991, after being absent from that country for nearly a century. Although initially attributed to contaminated ballast water from a foreign ship, cholera's return to Peru was eventually linked to elevated sea surface temperature, coincident with El Niño (Lipp et al., 2003).

The Arctic

The physical effects of climate change are dramatically apparent in the Arctic, where temperatures have increased at nearly twice the global average over the past century, causing widespread melting of land and sea ice (see Figure SA-13; Borgerson, 2008; IPCC, 2007b). This trend is expected to continue and intensify, resulting in warmer winters, increased annual precipitation, more frequent extreme weather events, and—as the ice continues to melt—greater river discharge and increased sea height, according to workshop speaker Alan Parkinson, of the CDC's Arctic Investigations Program in Anchorage, Alaska.

These rapidly changing environmental conditions are ripe for infectious disease emergence on several fronts, Parkinson observed (see Chapter 2). Higher temperatures at these latitudes permit the survival and replication of cold-sensitive pathogens such as Vibrio parahaemolyticus, as previously noted (McLaughlin et al., 2005), or increase the prevalence of existing pathogens such as Clostridium botulinum (a particular concern for indigenous peoples, who traditionally preserve food by fermentation). Preliminary studies suggest that warmer ambient temperatures, which would be predicted to occur with climate change, may result in higher rates of food-borne botulism associated with the consumption

FIGURE SA-13 The Arctic ice cap, September 2001 (Top) and September 2007 (Bottom).

SOURCE: NASA, as printed in Borgerson (2008).

FIGURE SA-13 The Arctic ice cap, September 2001 (Top) and September 2007 (Bottom).

SOURCE: NASA, as printed in Borgerson (2008).

of fermented seal meat (Leclair et al., 2004). In addition to fermentation, many Arctic residents store fish and meat by air-drying or by burying it on or near the permafrost; changes in climate may therefore result in higher rates of spoilage of food preserved by either method (see Parkinson in Chapter 2).

As temperatures increase, reservoir species for zoonotic diseases may survive winters in larger numbers, increase in population, or expand their geographic ranges. Beavers, common hosts for the water-borne protozoan Giardia

30 GLOBAL CLIMATE CHANGE AND EXTREME WEATHER EVENTS

intestinalis, are migrating northward in Alaska, into areas that have become more habitable due to changes in vegetation and habitat (Parkinson and Butler, 2005). Similarly, climate conditions that favor range expansion by foxes or rodents that carry alveolar echinococcosis—a lethal zoonotic infection caused by the larval stage of the tapeworm Echinococcus multilocularis—may increase the human incidence of this disease (Holt et al., 2005; Parkinson and Butler, 2005; Schweiger et al., 2007).

Climate change may enable mosquito-borne diseases such as the West Nile virus (WNV) to move into the Arctic by increasing vector survival and disease transmission rates, as well as by altering migration patterns of birds and other reservoir species. WNV has already reached Canadian provinces adjacent to Alaska at a latitude of 57°N, and its mosquito vector, Aedes albopictus, is present in the state, Parkinson reported. Climate change is also projected to shift the range of the tick vector of Lyme disease northward (Ogden et al., 2005), but as with WNV, the consequences of such movements for human disease depend on a range of factors, including land use, human population density, and temperatures warm enough for pathogens to reach an infective dose in the vector.

Public health challenges Together with a catalog of health impacts attributable to climate change in the Arctic, Parkinson noted two indirect effects that appear especially favorable to infectious disease transmission: (1) damage to the sanitation infrastructure resulting from the melting of permafrost (upon which many Arctic communities are built) and from flooding, and (2) the opening of the Northwest Passage.

Inadequate housing and sanitation are already important determinants of infectious disease transmission in many Arctic regions, Parkinson observed. In a recent study conducted in western Alaska, Parkinson and coworkers found significantly higher rates of hospitalization for young children with pneumonia, influenza, and respiratory syncytial virus (RSV) and for people of all ages with outpatient Staphylococcus aureus infections and hospitalization for skin infections, in communities without in-house piped water service, compared to communities with in-house piped water service (Hennessey et al., 2008). This suggests that the loss of existing basic sanitation services, through climate change-related infrastructural damage, may raise infectious disease rates in Arctic populations. Furthermore, Parkinson noted, sewage leaking from pipes ruptured by melting permafrost contains water-borne pathogens such as Giardia, Cryptosporidium, and the hepatitis A virus.

A second potential route for infectious disease emergence in the Arctic is being cleared along with the sea ice. With the opening of the Northwest Passage—and perhaps, eventually, the Northeast Passage—more ships will take this shorter route as a sea lane alternative to the Panama Canal when crossing between the Atlantic and Pacific Oceans (see Figure SA-14). Increased maritime shipping in the Arctic is expected to bring many economic benefits to these north-

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