Certain arthropods (insects, ticks, mites) are serious threats to our agricultural economy and to human health. Billions of dollars are lost annually to diminished productivity, damaged structures and animal products, restrictions on exports, and costly control and treatment.
Mosquitoes, ticks and flies transmit viruses, bacteria and parasites that cause a wide variety of diseases, including many transmissible to both animals and humans, such as West Nile virus and Lyme disease. Insects can also directly diminish the value of agricultural products and human enterprise. For example, screwworm destroys the value of hides and stunts the growth of cattle, fire ants make land unsuitable for pasture, and the Formosan subterranean termite causes more than a billion dollars of damage annually to wooden structures.
For more than 100 years the USDA has led world research on arthropods affecting livestock and people. It was Theobald Smith, an USDA scientist, who in 1890 discovered that ticks transmit cattle fever, a blood parasite that threatened to destroy the young beef cattle industry. This was the first proof of any arthropod borne disease and led to the program to dip cattle, eventually eradicating cattle fever from the US. Cattle fever established the model for ARS research: identification of an important problem, basic science, invention and implementation of a solution. Based on a deep understanding of screwworm genetics and biology, Edward F. Knipling and Raymond C. Bushland devised the remarkable method of rearing and releasing billions of sterile male flies to competitively mate with female flies. Today all of North and Central America are screwworm free and the sterile insect technique (SIT) has been used to safely control many other insect pests.
It is through Program 104 that USDA most closely supports the American military. Since the Second World War, ARS scientists have closely cooperated in developing measures to protect US military personnel deployed to regions where vector borne diseases, like malaria and dengue, are endemic. In the 1940s ARS scientists demonstrated that the new insecticide DDT could stop epidemics of louse-borne typhus. This was followed by the discovery of DEET, still the world’s most effective mosquito repellent, the development of ultra-low volume fogging for mosquito control, and the invention of insecticide treated cloth for uniforms and bed netting. ARS and the Department of Defense are now testing the first repellent significantly better than DEET.
American livestock is threatened not only from indigenous arthropods and diseases but from potentially invasive ones. Screwworm and cattle fever have been eradicated from the US but eternal vigilance is needed to prevent their reinvading. The fire ant and Formosan subterranean termite both invaded the US on imported commodities in the 20th century. The introduction of West Nile Virus in 1999 and its subsequent rapid spread across the US typifies the threat from introduced pathogens. In general, vector borne diseases are more difficult to predict and to control than are directly communicable diseases, such as brucellosis. Preparing for the next, unknown threat is one of the biggest challenges facing NP 104 scientists today. Most research in ARS on arthropods of veterinary, medical or urban importance can be classified into one of four components.
Ability to predict outbreaks of native and exotic arthropod borne diseases and screwworm using improved tools for detection and surveillance, including DNA based assays capable of detecting invasive and recombinant pathogens, species specific traps, and GIS models for monitoring vector dynamics.
Effective, area-wide control of fire ants and subterranean termites using integrated pest management, including GIS modeling, selective traps, baits and a variety of biological controls.
Identification of the genes of the tick Boophilus responsible for insecticide resistance, blood digestion and susceptibility to protozoan blood parasites of cattle, horses and sheep.
An area-wide strategy, confirmed in the field, for the control of suburban Lyme disease using innovative tools that reduce the density of vector ticks feeding white-tail deer, the amplifying host.
Innovative repellents, attractants and control agents based on an understanding of the molecular basis of vector sensory physiology.
Reduction of pesticide and drug residues in livestock through development of innovative biological agents, such as neuropeptide mimics and baculovirus.
New pesticide formulations and delivery systems suited to the special needs of protecting American military from vector borne diseases while deployed abroad.