Skip to main content

Currently Skimming:

1 Vector-Borne Disease Emergence and Resurgence
Pages 41-126

The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.


From page 41...
... , now drive the rapid, global dispersion of pathogens and their vectors. "If we hope to reverse the trend of emerging and reemerging infectious diseases," Gubler insists, "the movement of pathogens and arthropod vectors via modern transportation must be addressed." 41
From page 42...
... Plant systems, for example, "allow large experiments to be conducted, with multiple hosts, vector species and pathogen strains, which could be used to experimentally address ecological and evolutionary hypotheses on pathogen range and transmission efficiency," he explains. In describing the rise of Pierce's disease of grapevines in California following the recent introduction of a highly efficient insect vector for a local bacterial pathogen, Almeida explores a common pattern of vector-borne disease emergence from an agricultural perspective.
From page 43...
... .   Director, Asia-Pacific Institute for Tropical Medicine and Infectious Diseases; Professor and Chair, Department of Tropical Medicine, Medical Microbiology and Pharmacology, John A
From page 44...
... It was not until the Institute of Medicine (IOM) report on emerging infectious diseases that policy makers took notice (IOM, 1992)
From page 45...
... A final factor has been the trend in recent decades to build houses in woodlots where humans share the ecology with deer, mice, and ticks; thus most transmission to humans in the northeastern United States where the majority of cases of Lyme disease occur, is residential (Steere et al., 2004)
From page 46...
... This was the first global emerging infectious disease epidemic that impacted the global economy since infectious diseases were controlled in the 1950s. It is estimated that this small outbreak cost India US$3 billion (John, 1999)
From page 47...
... 1-2 cases of plague exported from India (Fritz et al., 1996) , but this epidemic was the "wake-up call" that modern transportation and globalization were major drivers of pandemic infectious diseases.
From page 48...
... All have a similar transmission cycle involving birds as the natural vertebrate hosts and Culex species mosquitoes as the enzootic/epizootic vectors, and all cause severe and fatal neurologic disease in humans and domestic animals, which are generally thought to be incidental hosts, as well as in birds. The clinical illness associated with WNV in humans ranges from asymptomatic infection to viral syndrome to neurologic disease (Hayes and Gubler, 2006)
From page 49...
... . The epidemic investigation, which focused only on neurologic disease, identified 62 cases with 7 (11 percent)
From page 50...
... . Migratory birds have likely played an important role in the spread of WNV in the western hemisphere (Owen et al., 2006; Rappole et al., 2000)
From page 51...
... This virus most likely had better fitness and caused higher viremias in susceptible hosts, allowing it to take advantage of modern transportation and globalization to spread, first in the Mediterranean region and Europe, and then to the western hemisphere. This speculation is supported by sequence data documenting that the viruses isolated from these recent epidemics/epizootics are closely related genetically, most likely having a common origin; all belonged to the same clade (Lanciotti et al., 1999, 2002)
From page 52...
... . The broad vertebrate host and vector range of WNV was another important factor in the successful spread of epidemic/epizootic WNV transmission.
From page 53...
... . Dengue/Dengue Hemorrhagic Fever 1-6 The dengue viruses (DENVs)
From page 54...
... The economic development, population growth and uncontrolled urbanization in the post-war years created ideal conditions for increased transmission and spread of urban mosquito-borne diseases, initiating a global pandemic of dengue. With increased epidemic transmission, and the movement of people within and between countries, hyperendemicity (the co-circulation
From page 55...
... By the 1990s, Aedes aegypti had regained the geographic distribution it had before eradication was initiated (Figure 1-8)
From page 56...
... SOURCE: Courtesy, Division of Vector-Borne Infectious Diseases, CDC, Fort Collins, CO; adapted from Gubler (1998)
From page 57...
... . Urban epidemic transmission was effectively controlled in the Americas in the 1950s, 1960s, and 1970s by the Aedes aegypti eradication program (see earlier discussion)
From page 58...
... . In the Americas, the reinfestion of most Central and South American countries by Aedes aegypti has put the urban centers of the American tropics at the highest risk for epidemic urban YF in more than 60 years (Gubler, 1989, in press)
From page 59...
... As noted for Asia, the high seroprevalance rates for the DENVs and other flaviviruses in most Central and South American countries could down-regulate viremia and illness, thus decreasing the risk of secondary transmission and clinical diagnosis. Additionally, the enzootic YFV may require adaptation to Aedes aegypti and humans, before becoming highly transmissible in the urban environment.
From page 60...
...  The dramatic global reemergence of epidemic vector-borne diseases in the past 25 years is closely tied to global demographic, economic, and societal trends that have been evolving over the past 50 years. Complacency and deemphasis of infectious diseases as public health problems in the 1970s and 1980s resulted in a redirection of resources and ultimately to a decay of the public health infrastructure required to control these diseases.
From page 61...
... VECTOR-BORNE DISEASE EMERGENCE AND RESURGENCE 61 A DEN-1 DEN-2 DEN-1 DEN-2 DEN-1 DEN-3 DEN-2 DEN-4 B DEN-1 DEN-2 DEN-1 DEN-1 DEN-3 DEN-1 DEN-2 DEN-1 DEN-2 DEN-4 DEN-1 DEN-3 DEN-2 DEN-2 DEN-2 DEN-4 DEN-3 DEN-3 DEN-1 DEN-3 DEN-4 DEN-4 DEN-2 DEN-4 DEN-1 DEN-3 DEN-2 DEN-4 DEN-3 DEN-1 DEN-4 DEN-2 DEN-3 DEN-4 FIGURE 1-11  The global distribution of dengue virus serotypes, (A)
From page 62...
... Lessons Learned and Challenges to Reverse the Trend At the dawn of the 21st century, epidemic infectious diseases have come "full circle" in that many of the diseases that caused epidemics in the early 1900s, and which were effectively controlled in the middle part of the 20th century, have reemerged to become major public health problems. Complacency and competing priorities for limited resources have resulted in inadequate resources to continue   Reprinted in part with permission from Gubler (2008)
From page 63...
... Local public health infrastructure must be rebuilt and maintained in order to contain disease outbreaks as local public health events instead of letting them spread around the world via modern transportation. The public and the press require accurate and reliable information in order to prevent panic and overreaction.
From page 64...
... Changes in animal husbandry and agricultural practices, combined with regional human behavior and cultural practices, and increased trade, will all facilitate the emergence of exotic zoonotic pathogens in a region where people from rural areas continue to migrate to large urban centers, and from which the movement of people, animals, and commodities increase the risk of dispersal via modern transportation and globalization. Finally, if we hope to reverse the trend of emerging and reemerging infectious diseases, the movement of pathogens and arthropod vectors via modern transportation must be addressed.
From page 65...
... , and the absence of a specific study section within the National Institute of Allergy and Infectious Diseases (NIAID) to peer review extramural research proposals in ecology.
From page 66...
... . Throughout the most recent decade, research in vector biology has been dominated by the discipline of molecular biology with the ultimate goal of manipulating vector populations through the introduction of genes that will reduce vector competence for specific pathogens, thereby eliminating the need for population suppression (Aldhous, 1993; Alphey et al., 2002; Kramer, 2004; Speranca and Capurro, 2007; Nene et al., 2007)
From page 67...
... . Consequently, we know very little about the natural limits of population growth for vector populations and efforts to reduce population density of vectors are not based on knowledge of the regulatory processes already operative in nature.
From page 68...
... The recent epidemics of Lyme disease and West Nile virus in the United States have demonstrated our inability to effectively respond to vector-borne disease threats in our own backyard (literally)
From page 69...
... While other emerging disease threats, such as directly transmitted zoonotic pathogens and, to a lesser extent, directly transmitted human pathogens, also are dependent upon the environment, vector-borne diseases have the greatest potential for advancing the integration of ecology and environmental science into the mainstream of infectious disease epidemiology. Such integration is long overdue, and it will fill a significant void in the spectrum of biological disciplines currently contributing to human health.
From page 70...
... I will also discuss similarities among vector-borne diseases and present an example of how the introduction of an invasive vector species has dramatically modified the ecology of a bacterial pathogen of previous limited importance. One of my main goals is to emphasize that much could be gained in our understanding of the ecology of vector-borne human and animal diseases from work done with agricultural systems, and vice versa.
From page 71...
... Human Health, Environmental Change, and Plant Diseases One of the challenges for this century will be to sustainably produce enough food for an exponentially growing world population. In 2006, 6.5 billion people inhabited the planet; the World Health Organization estimates that number will increase to 9 billion by 2050 (UN, 2007)
From page 72...
... diseases such as Lyme disease, in relation to their ecology (Eldrige and Edman, 2000)
From page 73...
... The Plant Pathogenic Bacterium Xylella fastidiosa as a Case Study The xylem-limited bacterium X fastidiosa is present throughout the Americas and causes disease in many crops of economic importance, including Pierce's disease of grapevines (PD)
From page 74...
... In recent decades, however, the disease has been constantly present at low incidence in the wine grape growing coastal valleys of Napa and Sonoma. The third, and current, epidemic emerged after the introduction of a polyphagous invasive vector species, Homalodisca vitripennis (glassy-winged sharpshooter; Hemiptera: Cicadellidae)
From page 75...
... vitripennis in California seem to be driven primarily by an invasive vector species that compensates for poor transmission efficiency by having large populations in and near citrus, and behavioral and ecological characteristics that promote pathogen spread within vineyards. Emergence of New X
From page 76...
... On the other hand, plant systems allow large experiments to be conducted, with multiple hosts, vector species, and pathogen strains, which could be used to experimentally address ecological and evolutionary hypotheses on pathogen range and transmission efficiency. Finally, ecological hypotheses based on either system may be useful in building models that can be tested for the development of disease control strategies.
From page 77...
... are maintained in endemic disease cycles in alternative habitats by different vector species (different dashed-line circle borders)
From page 78...
... Kennedy stated in the early 1960s in reference to the world community, "For in the final analysis, our most basic common link, is that we all inhabit this small planet, we all breathe the same air, we all cherish our children's futures, and we are all mortal." More than 40 years later it is evident that on this small planet we also share the same animal and human vector-borne infectious diseases, as evidenced by the global spread of emerging diseases such as West Nile virus (Hayes et al., 2005)
From page 79...
... described how climate variability has a direct impact on infectious diseases, and increased disease transmission has been linked to the El Niño/Southern Oscillation (ENSO) -driven global climate anomalies (Checkley et al., 2000; Pascual et al., 2000)
From page 80...
... These satellite-derived measurements are a proxy indicator of cloudiness and hence rainfall. When expressed as anomalies with respect to reference long-term means, negative OLR anomalies in the tropics represent regions of precipitating clouds, whereas positive OLR anomalies are associated with dry conditions.
From page 81...
... Increase and peaks in 1-13 dengue incidence is preceded by hot and dry periods indicated by positive OLR anomalies. Drought conditions in Southeast Asia are associated with the occurrence of warm ENSO episodes.
From page 82...
... for Lamu, Kenya, between 1998 and 2006. Negative NDVI and rainfall anomalies indicate unusually dry conditions.
From page 83...
... Subsequent RVF activity in this region has tended to cluster along the Senegal River, indicating that landscape modification can contribute to endemism of diseases. The association between RVF activity and alterations in the ecology of the region suggests that the development of new ecological habitats for potential Culex species mosquito vectors may have caused and/or enhanced the epidemic.
From page 84...
... . Additionally, negative OLR anomalies were observed over the equatorial Indian Ocean and East Africa indicating elevated convective activity and heavy rainfall.
From page 85...
... OLR anomalies in East Africa. The opposite patterns occur over Southeast Asia.
From page 86...
... Advance knowledge of an RVF, dengue, or chikungunya outbreak in their endemic areas might be used to prevent globalization of the disease by assessing favorable conditions in other parts of the world where suitable mosquito vectors, potential domestic animal hosts, and likely habitats for disease exist. Knowledge of vector-borne disease activity in endemic areas can be used to trigger monitoring of trade, and movement of people and mosquitoes on aircraft between sites of disease outbreaks and other places in the world where introduction might occur.
From page 87...
... . Early detection of RVF in human or mosquito hosts could provide early warning in the United States or other nonendemic regions or countries before ecological conditions become optimal for elevated mosquito populations, thus permitting targeted implementation of mosquito control, animal quarantine, and vaccine strategies in time to reduce or prevent animal and human diseases (Linthicum et al., 2007)
From page 88...
... The less developed countries are, ironically, those least responsible for causing global warming. Many health outcomes and diseases are sensitive to climate, including: heat-related mortality or morbidity; air pollutionrelated illnesses; infectious diseases, particularly those transmitted, indirectly, via water or by insect or rodent vectors; and refugee health issues linked to forced population migration.
From page 89...
... are expected to accompany the global warming.
From page 90...
... During heat waves, when stagnant atmospheric conditions may persist, air pollution often compounds the effects of the elevated air temperatures (Frumkin, 2002)
From page 91...
... VECTOR-BORNE DISEASE EMERGENCE AND RESURGENCE 91 26°C, and sea-surface warming by slightly more than 2°C intensifies hurricane wind speeds by 3-7 m/s (or 5 percent-12 percent) (Knutson et al., 1998)
From page 92...
... . Rising sea levels will result in the salination of coastal freshwater aquifers and the disruption of stormwater drainage and sewage disposal.
From page 93...
... . Infectious Diseases Water- and Food-Borne Diseases Water shortages, as mentioned above, contribute to diarrhoeal disease through poor hygiene, especially in poor countries.
From page 94...
... . A detailed understanding of the inter-annual cycles of cholera and other infectious diseases, however, requires the combined analyses of both environmental exposure and the host's intrinsic immunity to a disease.
From page 95...
... (Bulinus and activity, 25±2 as others) optimum Dengue fever Dengue virus 11.9 NYD Aedes 6-10 for mosquitoes biological activity Lyme disease Borrelia NYD NYD Ixodes ticks 5-8 for borgdorferi biological activity aThe thresholds shown assume optimum humidity (vector survival tends to decrease rapidly as dryness increases)
From page 96...
... , mosquito abundance tends to decrease with increasing altitude. Global warming is likely to result in an increase in the altitudes at which no malaria transmission occurs.
From page 97...
... FIGURE 1-22  As this graph produced by MacDonald (1957) illustrates, air temperature has a marked effect on the extrinsic incubation periods (EIPs -- the times taken by the parasites to produce sporozoites in their mosquito vectors)
From page 98...
... . These areas, which are at altitudes of .1000 m, have ratios of precipitation to potential evapo-transpiration that exceed 0.5 during the five wettest consecutive months of the year, and have minimum temperatures in excess of 15°C, are considered to be on the threshold of malaria transmission.
From page 99...
... across a large area are species and site-specific, and therefore cannot be generalised. Arboviruses Although Aedes aegypti is known to be strongly affected by ecological and human ‘drivers' in urban settings, this species is also influenced by climate, including variability in temperature, moisture and solar radiation.
From page 100...
... . Climate variability may also have an effect on West Nile virus (WNV)
From page 101...
... of Cases Mosquito Index 15,000 60 50 10,000 40 30 5,000 20 10 0 0 1985 1987 1989 1991 1993 1995 Year 180,000 100 160,000 Thailand 90 140,000 80 No. of Cases 120,000 Mosquito Index 100,000 70 80,000 60 60,000 50 40,000 40 20,000 0 30 1985 1987 1989 1991 1993 1995 Year FIGURE 1-25  Correlation between simulated, climate-driven variations in Aedes aegypti mosquito density (o)
From page 102...
... Many of the regions most vulnerable to climate change are also those least responsible for causing the problem. Africa, for example, is thought to harbour about 70 percent of all malaria cases but has the lowest per-capita emissions of the ‘greenhouse' gases that cause global warming.
From page 103...
... . The Intergovernmental Panel on Climate Change's ‘business-as-usual' scenario for1-26 greenhouse-gas (GHG)
From page 104...
... Positive effects may include fewer winterrelated deaths in some regions. Changes in temperature, humidity, rainfall, and sea level rise could all affect the incidence of infectious diseases.
From page 105...
... earlier in this chapter. Next, we provide an update on the two most prevalent vector-borne diseases in North America: Lyme disease and West Nile virus.
From page 106...
... Examples of Effects of Changes in Precipitation on Selected Vector-Borne Pathogens Vector Increased rain may increase larval habitat and vector population size by creating a new habitat.
From page 107...
... Increased sea level Alter estuary flow and change existing salt marshes and associated mosquito species, decreasing or eliminating selected mosquito breeding sites (e.g., reduced habitat for Culiseta melanura)
From page 108...
... . Human activities such as degraded housing infrastructure, which spawned abnormal vector population levels, also influence WNV transmission dynamics (Han et al., 1999)
From page 109...
... . Land use and land cover metrics contain interrelated information on biophysical conditions and vector and host community assemblages that influence WNV transmission.
From page 110...
... . Conclusions Climate change may affect the distribution and transmission intensity of a number of infectious diseases.
From page 111...
... 2004. Emerging infectious diseases of plants: pathogen pollution, climate change and agrotechnology drivers.
From page 112...
... Emerging Infectious Diseases 6(3)
From page 113...
... 2000. Emerging infectious diseases of wildlife -- threats to biodiversity and human health.
From page 114...
... Emerging Infectious Diseases 2(1)
From page 115...
... Emerging Infectious Diseases 7(4)
From page 116...
... Yellow fever. In Textbook of pediatric infectious diseases, 5th ed., edited by R
From page 117...
... Emerging Infectious Diseases 11(8) :1167-1173, http://www.cdc.gov/ncidod/EID/vol11no08/05-0289a.htm (accessed September 6, 2007)
From page 118...
... 1999. Origin of the West Nile virus responsible for an outbreak of encephalitis in the northeastern United States.
From page 119...
... Clinical Infectious Diseases 33(10)
From page 120...
... Emerging Infectious Diseases 12(10)
From page 121...
... 2006. Migrating birds as dispersal vehicles for West Nile virus.
From page 122...
... 1999. New challenges, new tools: the impact of climate change on infectious diseases.
From page 123...
... Emerging Infectious Diseases 8(1)
From page 124...
... 2007. Perspectives in the control of infectious diseases by transgenic mosquitoes in the post-genomic era -- a review.
From page 125...
... Journal of Infectious Diseases 178(5)
From page 126...
... Emerging Infectious Diseases 11(12)


This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More information on Chapter Skim is available.