Healthy Animals 39
bacterium. A bacterium in birds has been causing trouble and ducking
dots. New findings about fescue toxicosis and chemical compounds.
Fire ants outcompete other specieseven in the ants' native habitat.
Scientists combine two strategies to combat fire ants' spread.
flies. Two catnip compounds can discourage stable flies' bites.
palate. Poisonous plants research leads to a breakthrough on cleft palate
Higher pathogen loads found in bee colonies with colony collapse disorder.
Power to the
phages. Enzymes from certain viruses could benefit animal health.
Rangeland plants may harbor viruses transmitted by grasshoppers to cattle.
Stymied shots. A
parasite infection can compromise the effectiveness of a common swine vaccine.
Predicting Changes for Parasite- and Vector-Induced
Climate change could have a major influence on animal health, both directly
and indirectly, by affecting the parasites and vectors that spread diseases,
according to Eric Hoberg, an Agricultural Research Service (ARS) zoologist at
the agencys Henry A. Wallace Beltsville Agricultural Research Center in
Beltsville, Md. Hoberg is chief curator of the U.S. National Parasite
Climate change can alter an animals relationship with parasites and
vectors. These changes can influence where parasites and vectors thrive, making
certain geographical regions more or less amenable to them. Climate change can
also alter when and for how long parasites and vectors pose a threat to
agricultural animals. Climate can determine how pathogens are distributed,
transmitted and evolve, and can influence the factors associated with emerging
disease and how animals respond to those diseases. Significant environmental
changes have been well documented in recent decades, and some of these changes
are causing trouble for livestock.
Hoberg is one of many ARS scientists investigating the probable impact of
climate changes on agricultural parasites and virus vectors. Their research is
generating information that could help producers prepare for and respond to
heightened disease threats.
In one study, Hoberg collaborated with several Canadian scientists to
investigate the influence of climate change on parasitic lungworms known as
Protostrongylus stilesi in Arctic mammals. Although the lungworms had
never before been observed in muskoxen, the scientists observed them in
muskoxen that share habitat with Dall's sheep. Environmental changes that bring
the two animals into contact more frequently could result in larger parasite
"Climate change alters the boundaries between different species and
between natural and managed lands," Hoberg says. "When these
boundaries break down, it becomes possible for pathogens to switch between
Muskoxen are not a major agricultural animal in the United States, but their
interaction with lungworms and Dall's sheep could be used to establish
predictive models that could help U.S. animal producers better understand how
pathogens switch between hosts.
Climate change may also influence insects that spread diseases. At the ARS
Arthropod-Borne Animal Diseases Research Laboratory (ABADRL) in Laramie,
Wyoming, scientists are investigating several vectored diseases, including
bluetongue and Rift Valley fever (RVF).
"In recent years we've seen an incursion of bluetongue virus in Europe,
but whether that's affected by climate change or not hasn't yet been
determined," says ABADRL microbiologist Bill Wilson.
Several factors influenced by climate change could explain the spread of
bluetongue virus, says ABADRL entomologist Kristine Bennett. Higher
temperatures could enable Culicoides imicola, the disease's primary
vector in Europe, to inhabit a much larger geographic area. Higher temperatures
could enhance viral replication, potentially enabling indigenous
Culicoides populations to vector the disease. And warmer winter
temperatures could enable more Culicoides to survive the winter,
extending their influence.
Other factors are at play in the case of RVF, a viral disease that occurs in
Africa and recently has spread beyond the continent's borders into the Arabian
"RVF outbreaks are closely connected to cycling global climate
variability caused by El Niño Southern Oscillation
phenomenaparticularly rainfall and flooding, which introduce the virus
into livestock populations by facilitating the hatching of virus-infected
mosquito eggs resting in the soil," says Ken Linthicum, director of the
ARS Center for Medical, Agricultural and Veterinary Entomology in Gainesville,
"Our research hasn't focused on climate trends, but we do know that
elevated sea surface temperatures, such as those associated with El Niño
cycles, are related to heavy rainfall and flooding, which are related to RVF
outbreaks," Linthicum says.
Linthicum led a team of scientists in developing a model that in 2006
successfully predicted an RVF outbreak in Africa several months before the
outbreak occurred. This early warning enabled international aid organizations
to increase disease surveillance and to conduct public information, animal
vaccine and insect control programs. Since then, the model has predicted
outbreaks in southern Africa, Sudan and the Horn of Africa. Tools like this
could be essential for early detection and control of RVF, should it ever enter
the United States.
Since the 1950s, ocean buoys and satellite instrument monitors have clearly
documented increasing surface temperatures in the Indian Ocean. Linthicum and
his colleagues believe these rising temperatures and related rainfall result in
more frequent, smaller outbreaks of RVF.
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"When large outbreaks do occur, they tend to be bigger and more
widespread than those we observed in the past," he says. This information
could help policymakers mobilize outbreak response efforts.
"The potential effects of climate change are not yet fully
understood," says ARS national program leader Cyril Gay. "But
evidence suggests that animal health could be affected by rising ambient and
ocean temperatures. To protect U.S. livestock from parasite and vector-borne
diseases, scientists must be engaged in research on many fronts."
Regular surveillance will provide up-to-date information about changes in
pathogen populations. Laboratory and field research will help illuminate how
climate changes influence pathogen characteristics, and models will help
researchers and producers predict and plan for pathogen threats. With a
nationwide network of research facilities and a history of groundbreaking
pathogen research, ARS is well positioned to provide research, expertise and
tools to address any parasite or vector-borne disease threats that arise in
response to a changing global climate.
For more information about ARS research on parasites and disease vectors,
Strickman, leaders of ARS National Programs #103: Animal Health, and #104:
Veterinary, Medical and Urban Entomology.