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Extreme weather events can unleash a 'perfect storm' of infectious diseases, research study says
June 25, 2008Climatic conditions can alter normal host-pathogen relationships
An international research team, including University of Minnesota researcher Craig Packer, has found the first clear example of how climate extremes, such as the increased frequency of droughts and floods expected with global warming, can create conditions in which diseases that are tolerated individually may converge and cause mass die-offs of livestock or wildlife.
The study, published June 25 by PloS (Public Library of Science) ONE, an online peer-reviewed research journal, suggests that extreme climatic conditions are capable of altering normal host-pathogen relationships and causing a "perfect storm" of multiple infectious outbreaks that could trigger epidemics with catastrophic mortality.
Led by scientists at the University of California, Davis, the University of Illinois and the University of Minnesota, the research team examined outbreaks of canine distemper virus (CDV) in 1994 and 2001 that resulted in unusually high mortality of lions in Tanzania's Serengeti National Park and Ngorongoro Crater. CDV periodically strikes these ecosystems, and most epidemics have caused little or no harm to the lions.
But the fatal virus outbreaks of 1994 and 2001 were both preceded by extreme drought conditions that led to debilitated populations of Cape buffalo, a major prey species of lions. The buffalo suffered heavy tick infestations and became even more common in the lions' diet, resulting in unusually high levels of tick-borne blood parasites in the lions. (These parasites are normally present in lions at harmlessly low levels.)
The canine distemper virus suppressed the lions' immunity, which allowed the elevated levels of blood parasites to reach fatally high levels, leading to mass die-offs of lions. In 1994 the number of lions in the Serengeti study area dropped by over 35 percent after the double infection. Similar losses occurred in the Crater die-off in 2001.
The lion populations recovered within 3-4 years after each event, but most climate change models predict increasing frequency of droughts in East Africa.
"The study illustrates how ecological factors can produce unprecedented mortality events and suggests that co-infections may lie at the heart of many of the most serious die-offs in nature," said Packer, Distinguished McKnight University Professor of Ecology, Evolution and Behavior at the University of Minnesota.
University of Minnesota
Led by scientists at the University of California, Davis, the University of Illinois and the University of Minnesota, the research team examined outbreaks of canine distemper virus (CDV) in 1994 and 2001 that resulted in unusually high mortality of lions in Tanzania's Serengeti National Park and Ngorongoro Crater. CDV periodically strikes these ecosystems, and most epidemics have caused little or no harm to the lions.
But the fatal virus outbreaks of 1994 and 2001 were both preceded by extreme drought conditions that led to debilitated populations of Cape buffalo, a major prey species of lions. The buffalo suffered heavy tick infestations and became even more common in the lions' diet, resulting in unusually high levels of tick-borne blood parasites in the lions. (These parasites are normally present in lions at harmlessly low levels.)
The canine distemper virus suppressed the lions' immunity, which allowed the elevated levels of blood parasites to reach fatally high levels, leading to mass die-offs of lions. In 1994 the number of lions in the Serengeti study area dropped by over 35 percent after the double infection. Similar losses occurred in the Crater die-off in 2001.
The lion populations recovered within 3-4 years after each event, but most climate change models predict increasing frequency of droughts in East Africa.
"The study illustrates how ecological factors can produce unprecedented mortality events and suggests that co-infections may lie at the heart of many of the most serious die-offs in nature," said Packer, Distinguished McKnight University Professor of Ecology, Evolution and Behavior at the University of Minnesota.
University of Minnesota
Infectious Diseases News and Current Infectious Diseases Events RSSChina sees spike in rabies cases
A new Chinese study has reported a dramatic spike in rabies infections. The research, published today in the open access journal BMC Infectious Diseases, shows that in some provinces of China the number of human rabies cases has jumped dramatically since the new millennium.
Bacterial pneumonia caused most deaths in 1918 influenza pandemic
The majority of deaths during the influenza pandemic of 1918-1919 were not caused by the influenza virus acting alone, report researchers from the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health.
Researchers uncover attack mechanism of illness-inducing bacterium found in shellfish
An infectious ocean-dwelling bacterium found in oysters and other shellfish kills its host's cells by causing them to burst, providing the invader with a nutrient-rich meal, researchers at UT Southwestern Medical Center have found.
Leishmaniasis parasites evade death by exploiting the immune response to sand fly bites
Cutaneous leishmaniasis, a disease characterized by painful skin ulcers, occurs when the parasite Leishmania major, or a related species, is transmitted to a mammalian host by the bite of an infected sand fly.
How flesh-eating bacteria attack the body's immune system
"Flesh-eating" or "Strep" bacteria are able to survive and spread in the body by degrading a key immune defense molecule, according to researchers at the University of California, San Diego, School of Medicine and Skaggs School of Pharmacy and Pharmaceutical Sciences.
NIH scientists find a novel mechanism that controls the development of autoimmunity
Scientists at the National Institutes of Health (NIH) have found a mechanism in the immune systems of mice that can lead to the development of autoimmune disease when turned off.
Extensively drug-resistant tuberculosis found in California
In the first statewide study of extensively drug-resistant tuberculosis (XDR TB) in the United States, California officials have identified 18 cases of the dangerous and difficult-to-treat disease between 1993 and 2006, and 77 cases that were one step away from XDR TB. The study appears in the August 15 issue of Clinical Infectious Diseases, now available online.
Adverse reactions to antibiotics send thousands of patients to the ER
Adverse events from antibiotics cause an estimated 142,000 emergency department visits per year in the United States, according to a study published in the September 15, 2008 issue of Clinical Infectious Diseases.
Pathogen that causes disease in cattle also associated with Crohn's disease
People with Crohn's disease (CD) are seven-fold more likely to have in their gut tissues the bacterium that causes a digestive-tract disease in cattle called Johne's disease.
Students with food allergies often not prepared
College students with food allergies aren't avoiding the foods they know they shouldn't eat. Students of all ages are not treated with potentially life-saving epinephrine as often as they should be. And instructors, roommates and friends often are not aware of what to do if a food-allergic student has a reaction.
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