(4) A stand prognosis model was developed which projects long-range stand development, with and without DFTM outbreaks. (5) A model was developed that projects socioeconomic impacts on timber, water, wildlife, and fire hazard. (6) Sampling methods have been developed for eggs, larvae, and adults. (7) The insect's geographic range has been defined more accurately by pheromone (sex attractant) trapping of adult males. (8) One chemical insecticide was registered for aerial suppression of DFTM, R&D was completed on two others. Several are now registered for ground application. (9) Two microbial insecticides were registered for DFTM: Bacillus thuringiensis and a nuclear polyhedrosis virus (NPV). The DFM NPV is the first virus to be registered against a forest insect in the United states. (10) Improvements in aerial application technology were made., eg., an instrument was designed that provides continuous information or air-speed temperature, humidity, spray pressure and flow rate; three models were developed to simulate spray behavior. (11) A preliminary pest management system has been modeled which describes the likely conequences of each of many decision alternatives for supression of tussock moth outbreaks.

(1)

Additional research is needed in the following areas: relationship of tree nost physiology and resistance to DFTM; (2) physiology of insect-host interactions; (3) genetic variability among DFTM populations; (4) relation between local stand and site conditions and outbreaks; (5) natural enemy complex and its affect on both sparse and dense DFTM populations; (6) long-range biological effects of outbreaks, for example, on big game habitat, birds, water flow and runoff; (7) refine sampling and population evaluation methods: (8) conduct additional field experiments with chemical insecticides to refine dosage levels and application strategies; (9) feasibility of using pheromone (sex attractant) for preventive treatment of suboutbreak DFTM populations; (10) test NPV against release phase or incipient phase of DFTM outbreaks and determine carryover effects in the year following application; (11) validate projections of all model components during preoutbreak and outbreak periods; (12) adapt models for use region by region; (13) validate all components of the pest management system.

A continuing research program is underway with emphasis on the following problems: (1) importance of natural enemies and diseases in causing increases and decreases in DFTM populations through silvicultural practices; (2) strategies for reducing DFTM populations through silvicultural practices; (3) long-term effects of defoliation by DFTM on tree and stand growth; (4) improve detection and evaluation survey techniques using pheromones, including a trapping system to predict critical population changes; (5) feasibility of controlling DFTM by the mating disruption technique using pheromones; (6) improved microbial spray formulations of Bacillus thuringiensis NPV; (7) evaluation of new candidate insecticides for suppression of DFTM.

The major animal diseases and pests of importance to the U.S. livestock producers can be divided into four broad areas. These are the foreign animal diseases which are a threat to U.S. livestock; zoonotic diseases which affect man and are of public health significance; production diseases such as mastitis, shipping fever, and enteric diseases which currently reduce livestock production efficiency; and insect pests which also reduce livestock production efficiency or transmit disease. These diseases and insect pests of livestock severely decrease or severely limit production of high quality animal proteins in the United States and throughout the world. Currently, it is estimated that 15 to 20 percent of food animals die before reaching market. Death losses, growth inefficiencies, vaccination costs, and disease treatment in livestock cost the U.S. consumer an estimated $12 billion annually. Internationally the effect of livestock diseases on the economics and the human nutritional levels are even more significant. In the future these losses and inefficiencies in livestock production will be of even greater importance as agricultural land and energy resources become limited and the world population continues to expand.

Foreign animal diseases

The foreign animal diseases indirectly impact on the United States economy by restricting the international movement of animals and animal products; however, their major significance is the potential devastation of our livestock industry in the event of accidental introduction. Foot-and-mouth disease, FMD, is still a major disease of the cloven-hoofed animals animals vital for the production of food and clothing in many parts of the world. Mortality due to foot-and-mouth disease is usually

low; however, diseased animals may lose up to 20 percent of their body weight and stop lactating, resulting in major economic losses in animal production. A recent study simulating a foot-and-mouth disease outbreak throughout the United States showed that if not controlled, a foot-and-mouth disease outbreak would result in direct and indirect costs of over $10 billion the first year. The SEA-AR research has concentrated on pathogenesis, improved diagnostic tests, improved disinfectants and vaccine development. Research is needed to characterize the immune response following infection and vaccination and to develop an effective subunit vaccine for use in endemic areas.

African swine fever

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African swine fever has probably existed as a non-fatal infection of indigenous wild swine in Africa for centuries. The disease was always highly fatal to domestic swine, and control was accomplished by slaughter and disposal of all infected herds. However, in Angola free ranging of domestic swine was permitted and over a period of years the African swine fever virus became endemic in the domestic pig population. recognized that evolutionary modification of the virus had occurred, allowing a large percentage of surviving domestic pigs to serve carriers. In 1957, African swine fever spread to Portugal and later to other southern European countries. A new form of African swine fever thus emerged which was less lethal than classical African swine fever, and subacute and chronic cases are more commonly seen.

as virus

In mid-1971, African swine fever suddenly appeared in Havana, Cuba, where over 12,000 pigs died. To ensure eradication of this disease, Cuba killed over 400,000 pigs in the providence of Havana. The Western Hemisphere remained free of the disease until 1978 when it was diagnosed in Brazil, the Dominican Republic, and Haiti, and again in Cuba in 1980. Extensive eradication programs were done in Cuba and the Dominican Republic with the slaughter of 1.5 million pigs in the Dominican Republic alone. An eradication program, through the efforts of the U.S., Mexico, and Canada, is scheduled to begin this year in Haiti. The U.S. Congress has appropriated $14.5 million for this program. It is estimated that if the virus were accidentally introduced into a major swine producing state, successful eradication could cost over $100 million, and the economic impacts of endemic African swine fever would run into the billions of dollars. The disease produces severe economic losses in pigs. Those that do not die are chronically infected and grow poorly. Attempts at development of vaccines have been relatively unsuccessful. Immunized pigs become carriers of the virus further complicating the epidemiological picture of this virus. SEA-AR has conducted research on the pathogenesis of the disease, improved methods to diagnose the disease, and on the immune response in hope of producing effective vaccines. Further research is needed on insect vectors, transmission of the virus, the immune response, and vaccine development.

Rift Valley fever

Rift Valley fever is another viral disease which had been confined to Africa for years. The virus now appears to have mutated and recently spread into Egypt and the Sinai Peninsula. It is a serious threat to the U.S. livestock industry, as the virus will infect humans who can unknowingly transport it from one continent to the next. Rift Valley fever produces abortions and stillbirths in sheep and cattle and is highly fatal to young animals. The outbreak in Egypt in 1978 and 1979 resulted in a 25 percent reduction in livestock numbers and was responsible for the severe meat shortage in the area. SEA-AR has done research on developing diagnostic capabilities and a killed virus vaccine. Further research on insect vectors, transmission, and low cost vaccines are needed to adequately protect our livestock industry in the event of accidential introduction of the virus.

Viscerotropic velogenic Newcastle disease (VVND)

VVND is exotic to the United States. Domestic strains of Newcastle disease have been known to be endemic in the United States since the 1940's. Vaccines have been developed for these less virulent strains, and except under unusual circumstances, they do not create significant economic losses in well-managed operations. In the late 1960's and early 1970's a

more virulent exotic strain of Newcastle disease began to be detected around the world in the integrated poultry industry. The incidence of this exotic Newcastle Disease was apparently tied to the increased movement of psittacine birds throughout the world.

Several smaller introductions of exotic Newcastle disease occurred and were contained in pet shops and some commercial poultry operations, especially along the U.S.-Mexican border. However, Exotic Newcastle disease was introduced into southern California in November 1971 and spread to the commercial egg producing industry. APHIS spent $56 million in task force and indemnity costs before it was eradicated 2 years later. More recently, outbreaks, now contained, have occurred involving wholesalers,

dealers, aviculturists, retail shops, and holding facilities for caged pet birds. These outbreaks were attributed to smuggled cage pet birds from Mexico and Central and South America. The import surveillance, diagnostic capability, eradication, and control efforts for Exotic Newcastle disease have cost more than $70 million in the past 10 years. SEA-AR research has provided diagnostic procedures, sampling methods, recommend use of disinfectants, and knowledge of the pathogenesis and epidemiology of the disease. Further research needs include development of an effective vaccine, improved diagnostic tests for virus characterization (it presently requires 9 to 15 days), further elucidation of the pathogenesis and viral shedding patterns of psittacine species, and better surveillance procedures for detection of the infection before spread occurs to our avian industries in the United States.

Zoonotic diseases

The major zoonotic diseases which are of public health significance are brucellosis and tuberculosis. An accelerated brucellosis eradication program was initiated in 1954 because of the extensive losses to the cattle industry due to abortions, and because of the public health problems associated with the handling of infected animals and animal products. In 1981, it is estimated that $150 million will be spent for the eradication program of which the Federal Government's share is $81.1 million. The research program for brucellosis is extensive and has included the development of improved methods of diagnosis, increased understanding of its pathogenesis and improved vaccines. Additional research is still needed to determine the duration of immunity following use of Strain 19 vaccine, to develop an inactivated vaccine and to determine how chronic infections are established. It is also necessary to develop methods to control brucellosis in the Alaskan reindeer.

The tuberculosis eradication program was started in 1917 and is currently costing approximately $14 million annually of which $5.9 million is contributed by the Federal Government. Extensive testing programs at time of slaughter are used to identify infected herds. Further research is needed to develop simplified diagnostic tests for use at slaughter and to develop methods of positively identifying the origin of infected animals.

Production associated diseases

The third group of diseases is the production associated diseases. Despite the fact that most developed countries including the U.S. have been successful in controlling many serious epidemic infectious diseases, losses to productivity from other livestock diseases remain high. These diseases are complex epidemiologically and have infectious toxic, genetic, metabolic, and nutritional etiologies or combinations of these. The diseases generally result from several etiologic factors acting in concert with environmental and production factors. This group includes: (1) infectious diseases and disease complexes, such as pseudorabies, bluetongue, mastitis, neonatal disease, multiple gastrointestinal and other parasitisms; (2) reproductive disorders; (3) stress related syndromes such as the bovine respiratory disease complex, salmonellosis, and transport tetany; (4) metabolic imbalances such as ketosis and hypomagnesemic tetany; (5) digestive system disorders, such as bloat and lactic acidosis; (6) nutritional disorders and marginal malnutrition-infectious disease complexes provoked by deficiencies in minerals and other essential nutrients; (7) toxicoses caused by industrial and agricultural chemicals and wastes, poisonous plants and mycotoxins; (8) combinations of two or more of the above.

Some production diseases are capable of killing large numbers of animals, and others may produce high morbidity in affected herds. However, as a

class, they cause their greatest reduction in productivity of livestock enterprises often without producing clinical signs of disease.

Pseudorabies

Pseudorabies is a specific example of an infectious disease which causes severe production losses. It is a viral disease that can affect most farm animals, but its major impact is in swine. Pseudorabies in swine has been present in this country for many years. Within the past 5 years, there has been a marked increase in the incidence and severity of the disease. In a recent study, the pseudorabies virus was isolated from 10 percent of swine at slaughter. It appears that stress may be one factor causing outbreaks in swine herds. The incidence of pseudorabies is widespread throughout all of the major swine producing areas of the U.S. The implementation of programs to control the disease has created market barriers for purebred swine producers. The disease can occur in swine herds without warning producing abortions and heavy losses of baby pigs. As the result of a research program initiated in the past 5 years, an attenuated vaccine has been produced and has proven effective in reducing the mortality on farms that have had outbreaks. In addition, a killed vaccine has also been produced. Both types of vaccines are commercially available. Varying degrees of success are reported for both vaccines; however, continued research is needed to determine the incidence of the disease in the major swine producing areas and the latency of the virus in normal (carrier) swine. One of the most important research needs is to develop an effective killed vaccine. Also, research is needed to characterize the different types of viruses that are responsible for the outbreaks of pseudorabies. Characterization of specific herpesviruses would aid in diagnosis and help to determine how pseudorabies is spread and permit the development of vaccines that would arrest the onset of the disease in swine herds.

Bluetongue

Bluetongue was formerly thought to be primarily a disease of sheep. There are over 20 antigenically distinct strains of which four occur in the United States. In sheep, bluetongue will produce severe cyanotic mouth lesions, death, abortions, and stillbirths. It is now apparent that cattle can have a mild form of the disease; however, the virus is increasingly implicated in abortions, stillbirths, and weak calves. A similar viral agent, epizootic hemorrhagic disease of deer, appears to produce complications similar to bluetongue in cattle. The SEA-AR research has primarily been to develop methods of typing bluetongue virus, study pathogenesis of bluetongue disease, improve virus isolation and diagnostic tests, and develop attenuated live and killed bluetongue virus vaccines. Research to develop improved methods of determining whether an animal is infected or not is needed to certify livestock for export. This research is difficult as virus isolations are difficult and antibody is not always present in carrier animals. Research is also needed to determine how much of the reproduction failures of cattle are due to these viruses and to develop improved vaccines and insect control procedures.