Why is parasitology such a diverse and dynamic field that offers such a wide variety of career opportunities? The answer is surprisingly simple and has a lot to do with the nature of parasites. Parasites are those organisms that use other species of plants and animals as hosts. These hosts provide the environment in which the parasite lives. In the history of life on earth, this parasitic lifestyle has been incredibly successful; the number of species of parasites exceeds the number of free-living species. And the adoption of a parasitic way of life has occurred independently in many diverse groups of organisms.

It is no wonder, then, that parasitology is a diverse field. Parasitologists study parasites wherever they occur, whether they are viruses, bacteria, protists, worms, insects, or a whether they belong to a myriad of other taxonomic groups. And parasitology is a dynamic field because the relationships between parasites and their hosts are dynamic, constantly changing. Parasitism comprises an ecological relationship between two individuals of different species where the parasite's environment is another living organism. Unlike the environment of free-living plants and animals, the environment of the parasite can fight back! Parasites and hosts are locked into a continuous struggle for survival, and understanding the mechanisms that each side in this battle uses to gain advantages challenges parasitologists to understand biological phenomena at the cutting edge of a wide variety of scientific disciplines.

A diversity of career options exist within the field of parasitology because parasites affect the world in so many different ways. Rewarding careers await parasitologists with interests in medicine and public health. Veterinary parasitologists play vital roles in controlling diseases of domestic animals. Agriculture and aquaculture are dependent upon parasitologists to assist in providing plant and animal food for an increasing human population. Parasitologists contribute significantly to our basic understanding of the manner in which our biological world functions. Ecologists, molecular biologists, immunologists, evolutionary biologists, systematists study parasites and provide a source of information regarding fundamental biological principles. This basic research forms the foundation upon which applications of benefit to man are derived. Parasitologist contribute greatly to the education of the scientific community. The intricate webs of relationships involving parasites and hosts aid students in understanding the interrelatedness of diverse scientific endeavors.

Medical Parasitology

Perhaps the best known aspect of the importance of parasites is the role that they play in causing human disease. For example, hundreds of millions of people suffer from malaria and each year over one million human deaths are caused by this parasitic disease. Diseases caused by many species of parasitic worms, blood flukes, tapeworms, hookworms, and others are still scourges of mankind. Insect parasites such as fleas and lice are, at best, annoyances to man, and as vectors of diseases like bubonic plague and typhus have been responsible for uncountable human mortality. Mosquitoes not only transmit malaria, but spread yellow fever, encephalitis, and other viral diseases, and are responsible for inoculating into humans several species of filarial worms that cause some of the most horrific diseases in the medical literature. Emerging diseases such as Lyme disease, transmitted by ticks are increasingly recognized as significant to human health.

Medical parasitologists utilize many approaches in combating parasites. Among the areas of research are epidemiology, chemotherapy, immunology, and pathology. Exciting advances that hold promise in reducing parasitic disease have come from basic research by parasitologists in the fields of molecular and cellular biology, genetics, and physiology. Promising breakthroughs in the development of vaccines against medically important parasites exist because of technological and conceptual advances in these fields as well as in allied disciplines like immunology, vector biology, and biochemistry.

The field of public health is closely allied with medical parasitology. The global distribution of parasites offers great challenges to workers in this field. Public health practitioners are employed by national, state, and local governments, or may work for international agencies like the World Health Organization. Private industry, philanthropic and charitable organizations, military organizations, and a variety of other institutions also utilize the services of workers in the area of public health.

Agriculture, Aquaculture, and Veterinary Parasitology

Human health is not only affected directly by parasites that can infect man, but is also affected indirectly by parasites that cause diseases in plants and animals that are food for humans. Of the millions of people who die each year from malnutrition, over half are children under the age of five. The inadequate supply of food on earth and its uneven distribution among developing and developed countries results in starvation and human misery. Predictions of continued increase in human reproductive rates will inevitably result in increasing overpopulation and an exacerbation of food shortages. If agriculture and aquaculture are to be depended upon to supply food for an ever-expanding human population, then the efficiency of food production must increase, in part by reducing loss of food due to parasitic diseases of crops, domesticated animals, and animals derived from the increasingly important aquaculture industry. The use of parasites as biological control agents against crop insects holds much promise for increasing agricultural production.

Veterinary parasitologist care for domesticated animals used for food and for work, as well as caring for our companion animals. Veterinarians play an indirect role in human health when they control parasites in non-human animals that are transmissible to man. Animals used by humans for sport and recreation also require the services of veterinary parasitologists. Pharmaceutical companies are important sources of employment of parasitologists and the development of chemotheraputic drugs to eliminate parasites of animals is of major economic significance. The discovery of antiparasitic drugs for domesticated animals has not only benefited the agricultural industry, but in some cases, has aided humans when these same chemotheraputic agents have been demonstrated to be effective in the treatment of medically important parasites.

Wildlife and Fisheries Parasitology

Career opportunities exist for parasitologists who can assist wildlife managers in the development of programs designed to protect animals in their natural environment. Parasitologists working for government agencies, industry, and universities survey wild animals for parasites and disease and develop strategies to reduce the negative impact of parasites on wildlife populations. Conservation biologists are especially interested in parasitic diseases of threatened and endangered species and use this information to formulate management plans for their protection. Monitoring parasites in wild animals that are capable of being transmitted to man is another important function of parasitologists. Fisheries biologists not only need information on the role of parasites in causing fish disease and fish parasites that humans can acquire from eating fish, but may use parasite data to understand aspects of the .. of natural populations of fishes. For example, parasites have been employed as "biological tags" and a knowledge of a fish's parasites may provide useful information regarding the geographic origin of a stock of fish or insight into the migratory patterns of fish in aquatic ecosystems. Knowledge of parasite life cycles may provide wildlife biologists with data on trophic interactions and food webs. Information on parasites is important to managers who wish to relocate game species to new geographic regions. Alterations of natural environments such as damming of rivers, channelization of streams, cutting of timber may affect important game species by altering parasite abundance, and the advice of parasitologists is often sought before making such decisions.

Ecological and Systematic Parasitology

These exciting areas of parasitology are rooted in the study of the evolution of parasites and their interactions with the environment provided by their hosts. These basic areas of inquiry often lead to breakthoughs in applied areas of parasitology with direct or indirect benefits to man.

With our increasing awareness that human activities cause significant environmental destruction and extinction of species, biodiversity studies have recently assumed a new importance. Major efforts are underway globally to conduct floristic and faunistic surveys and document the distribution of species. Because the number of species of parasites exceeds the number of species of free-living plants and animals, it is clear that biodiversity research will require the talents and efforts of parasitologists. The field of parasite taxonomy and systematics currently shows a resurgence of activity because of new methods that have recently been incorporated into the discipline. Techniques developed by molecular biologists have been applied to questions regarding relationships among taxonomic groups of parasites and are providing powerful new insights. The study of ecological aspects of host/parasite relationships has benefited greatly from the use of computer technology to vastly increase the ability of parasitologists to quantify and analyze the dynamics of parasite populations. The tools of molecular biology are also being assimilated into the field of ecological parasitology and the promise of new discoveries regarding parasite life cycles, detection and identification of parasites, patterns of parasite transmission, and colonization are extremely exciting.

Applications of basic research in parasite systematics and .. are likely to be forthcoming and will provide career opportunities for parasitologists. Geographic information systems will assist ecologists in understanding large scale patterns of parasite distribution. A vital future consideration will be the assessment of the potential that global warming will have on the redistribution of parasites on our planet. One ominous implication of global warming is the possibility that medically important parasites that today are considered to cause "tropical diseases" will spread into temperate regions as the climate warms. Ecological parasitologists will have an opportunity to apply basic principles of parasite distribution and colonization to assist medical parasitologists in assessing the potential role of global warming in the field of public health.

Biochemistry and Molecular Biology of Parasites

Powerful technological advances have revolutionized the study of biology at the sub-cellular level. The promise of advances in parasitology from the application of these tools is great, and will lead to many new career opportunities. Genetics of parasites can be elucidated at levels never before possible using techniques such as polymerase chain reaction. Many applications can be foreseen from enhanced knowledge of parasite genetics, including development of diagnostic tools for the detection and specific diagnosis of parasites. Elucidation of metabolic pathways will not only add basic insights about the ways in which parasites differ from free-living organisms, but these differences can be exploited by developing chemotheraputic strategies against parasites that target metabolic differences of parasites and their hosts.

Immunoparasitology

Job opportunities for immunologist who desire to work with parasites are likely to increase because of new technical developments in the field and because of new practical applications of this technology. One important thrust in parasite research today is the development of vaccines against parasites of man and domestic animals. The benefits of incurring life-long immunity among individuals and the goal of imparting complete protection to entire populations is an important driving force in the effort to discover vaccines against parasites. The existence of efficacious vaccines against viruses and bacteria provides incentive to immunoparasitologists to develop analogous protection strategies against protists and helminths. However, the realization that these eukaryotic organisms are much more immunologically complex has lead to an appreciation that much more basic research in parasite immunology is required in order to guarantee success in the widespread use of vaccines to control protozoan and metazoan parasites. Yet, with the benefits to mankind that will be forthcoming from the development of useful vaccines, it is apparent that many parasitologists will be employed in this important endeavor. In recent years, the development of specific diagnostic tests for parasites has been one of the major successful applications derived from basic research in immunoparasitology. Clearly, further advances in basic research are on the horizon and application of this new knowledge will benefit both medical and veterinary parasitology.

Parasitology Educators

Academic careers are intellectually rewarding, and traditionally parasitologists have played an important role in the education of university students. One reason for the success of parasitologists in the academic community is the fact that parasitologists are among the most broadly trained of all biologists. Because examples of parasites can be found throughout the plant and animal kingdom, most parasitologists have a good working knowledge of biological diversity. Often, parasitologists serve as instructors of invertebrate zoology in many biology departments because most parasites and vectors belong to invertebrate taxa. Furthermore, because parasitologists study interactions of parasites and their vertebrate hosts, they are often well educated in vertebrate anatomy, physiology, and immunology. A knowledge of parasite life cycles requires parasitologists to be experienced in .. in order to understand how parasites are transmitted among hosts and how parasites are distributed within ecosystems. A university position offers an individual a challenging and rewarding career that combines both teaching and research. Research opportunities allow faculty to ask creative and imaginative questions, and design studies to answer these questions. Teaching has many rewards, including the satisfaction of seeing young people exposed to new knowledge and watching these students apply that knowledge to their own scientific curiosity.

A Diversity of Career Options

Because parasitology is such a broad and diverse field, a variety of career options are available. Most parasitologists were attracted to the field because of their scientific curiosity. Parasitology represents a great career for intelligent young people with inquisitive minds, and research opportunities are virtually unlimited. The variety of research areas in basic and in applied areas, in fields from the molecular level to the global level are unsurpassed in other field of biology. Many parasitologists are altruists and desire to use their scientific expertise to benefit mankind. Clearly, the myriad of problems that parasites cause humans provide many opportunities for parasitologists to contribute to the betterment of the human condition.

The Education of a Parasitologist

The university education of a parasitologist should whet the scientific curiosity and knowledge base that was begun in high school. Emphasis should be placed on attainment of a broad-based education in biology and chemistry. Overspecialization in one narrow field of the biological sciences will not lead to the range of knowledge required by most successful parasitologists. A good background in mathematics, computer science, and statistics will provide the computational skills that are required in virtually all areas of parasitology. The development of good writing and speaking skills is fundamental because every scientist must be able to communicate his ideas and results to others. Job opportunities in parasitology exist for people who attain a Bachelor of Science degree. Some possible positions include jobs in the food, agriculture, or pharmaceutical industries. Positions in clinical laboratories, environmental firms, or as research assistants in universities may involve work with parasites.

A Master of Science in Biology offers the opportunity for research as a graduate student with a parasitologist as a research advisor. Thesis research may involve laboratory or field study of parasites. It should be a goal of the Masters student to conduct a research project that can be published in a scientific journal. Although most parasitologists attaining an M.S. degree continue towards a doctoral degree, job opportunities that utilize the parasitology education and skills attained at the Masters level are available. Examples of vocations would include the fields of wildlife management, fisheries biology, aquaculture, animal husbandry, and human health care.

Most parasitology researchers hold either a Ph.D. or M.D. degree. Advantages of attaining a doctoral degree are numerous. Most tenure-track university faculty positions require a Ph.D. A doctoral degree greatly enhances opportunities to conduct research and to be successful at attaining funding to support research activities. Because the doctoral degree is the highest university degree that is awarded, the ability of a parasitologist to rise to the highest level in a chosen field whether in an academic institution, industry, or government is limited only by his or her talent and ability.

The Future of Parasitology

Parasites are here to stay. It is unfortunate that despite our best efforts, parasitologists will not likely in the foreseeable future completely rid the world of those species of parasites that cause human disease. But as the tools in our arsenal to control parasites become more powerful, parasitologists employed to fight these diseases will have the satisfaction of making important contributions to the improvement of human health. Human population growth will exert pressure on agriculture to increase our food supply, and parasitologists will be employed to contribute to this effort, as well as assisting in the emerging field of aquaculture. For those who enter the field of parasitology to answer basic questions in .., genetics, molecular biology, and other disciplines within the life sciences, parasitology research will continue to offer challenges. Armed with new research tools, parasitologists have unprecedented opportunities to work at the forefront of scientific endeavor, and have great potential for making exciting new discoveries. The American Society of Parasitologists extends an invitation to those young scholars contemplating careers in parasitology because of their desire to improve the human condition, as well as to those individuals who seek careers in parasitology because of an abiding scientific curiosity. Our Society offers its assistance to you in establishing a career in parasitology that will provide great rewards and satisfaction.

Written by William F. Font, Department of Biological Sciences, Southeastern Louisiana University, Hammond, LA 70402, USA.