Popular Science Monthly/Volume 77/August 1910/Bacteriology and Parasitology in Relation to Avian Diseases
|BACTERIOLOGY AND PARASITOLOGY IN RELATION TO AVIAN DISEASES|
By GEO. EDWARD GAGE, Ph.D.
MARYLAND AGRICULTURAL EXPERIMENT STATION
DURING the last ten years the sciences of bacteriology and parasitology have been established beyond previous expectation. To-day these sciences are so far-reaching that they not only have to do with medicine but extend into the realm of hygiene, agricultural sciences and the industrial arts. The advances made in connection with the life histories of the various microscopic animal parasites and the studies which have led to a general understanding of the relation between parasite and host have done much toward unearthing mysteries of diseases which attack domestic fowls and menace the poultry industry. Bacteriologists have enabled the avian pathologist to study and control these fatal diseases.
Practical applications of bacteriology to the arts and industries are only instances of the ramification of this science. In agriculture and closely allied science, bacteriology and also parasitology have been immediately and intelligently employed to set forth new facts and expose new problems. During the last few years bacteriology has held close relations with medical science. By the application and extension into the field of protozoon pathology one of the latest and most helpful developments in the study of infectious diseases has evolved. This is not alone true of human pathology, but must include avian, insect (such as bee and silkworm), sheep, swine and cattle diseases and possibly the diseases of plants.
In the poultry yards epidemics of the so-called "white diarrhoea," "black-head" of turkeys, and tape-worms, have demanded scientific study for remedial help. The loss to the poultryman is at present almost incalculable. The etiology of many diseases is understood only by the discovery of some bacteria or parasite. The mode of entrance of the invading microorganisms to the avian body, the study of the original source of the infectious material and the possibilities of transmission and infection can be apprehended only through prosecution of detailed bacteriological and parasitological studies. Individual birds may suffer from malnutrition and be afflicted with ailments which may be the result of inability to utilize food properly, but when a whole flock becomes droopy, listless and unable to maintain normal life, we must resort to the field of parasitology or bacteriology for the cause.
In the warfare against the ravages of disease a most rational hygiene of the poultry yards must be observed, and in order to understand thoroughly those factors which have to do primarily with eliminating the trouble, it is to the use of disinfectants and antiseptics that we must resort. Here again the science of bacteriology lends a helping hand, for data concerning the efficiency of disinfectants can be ascertained only by bacteriological technique. It then becomes the duty of the scientist to direct his entire attention to those factors which in themselves are sufficient to allow a foothold for many an infectious disease. It is no less a fact among domestic birds than with human beings, that infection may take place by contaminated food, the particular parasite or organism being transmitted in such manner. All the modes of spread are recognized, and just as the spread of human diseases are held to be matters of public concern and preventive measures are instituted by expert bacteriologists, so also should the spread of diseases among domestic fowls be of the same great concern to the poultryman if he is desirous of maintaining his birds in a healthy condition.
Probably one of the most difficult problems in relation to avian diseases lies in the prompt recognition of the cause, so that measures may be employed immediately to allay the trouble. With the large poultry farms it may appear that careful observation of hygienic measures involve too much time, but under many circumstances and especially at this infant stage in our knowledge concerning avian diseases the application of searching and delicate parasitological and bacteriological tests are often necessary to determine the proper method of procedure.
The great losses to poultrymen from the disease known as "black head" or "coccidiosis of turkeys" has called scientific men to make thorough investigation and a specific parasite known as a coccidium has been claimed to be the cause. Dr. Geo. B. Morse, of the Bureau of Animal Industry, United States Department of Agriculture, states that this coccidium may infect turkeys, ducks and pigeons. It has a definite life cycle. He describes it as a certain circular, sometimes slightly oval, cyst, 12 to 25 microns in diameter, containing granular matter which may fill the cyst or occupy only a portion of it. These are permanent cysts and may be voided in the feces of the bird. These only require warmth and moisture for their development into sporozoites by which the disease is transmitted to other birds. By the destruction of the malarial parasite within the body of man y we may break the life cycle and thus interrupt the continuity of the transfer between man and mosquito in the transmission of this disease. In like manner, the scientist can plan to break the cycle of these avian parasites within the body of the bird aud consequently eliminate infection. Contributions from the Division of Biology of the Rhode Island Experiment Station have furnished us interesting facts concerning parasitism of Cytodites nudus, a mite and Hæmaphysalis chordeilis, a tick and these are but a beginning to the study of such parasites affecting birds. It demonstrates the field for research in parasitology and what contributions from this realm of science would mean in determining the cause of so many diseases, the etiology of which at the present time is unknown.
Fowl typhoid, cholera, tuberculosis and hosts of other afflictions were discovered through the aid of scientific bacteriologists. In a very recent publication Professor Rettger, of Yale University, has demonstrated the value of bacteriology, by his valuable contribution to the study of white diarrhœa. He has been able to demonstrate the rôle of bacteria in the etiology of this disease. We need no better example of the usefulness of such a science in planning investigations of this nature. By thorough bacteriological methods he has been able to give us the results of his work and has shown how infection may occur, what it means to the poultry industry, and methods of prevention. This also demonstrates how bacteriological methods have been used to study epidemiology. It has given a procedure based on bacteriological facts and with such methods at hand we are supplied with the means of suggesting treatments which undoubtedly will do much toward solving the problems which have heretofore been unsolved. These studies have shown that the function of pure water and food and sanitary conditions are essential to the daily life of domestic birds. If diseases of the poultry yards are to be suppressed, hygienic measures must be observed here as with human beings. It was not until after the introduction of hygienic measures such as a proper sewage disposal, and water filtration that the death rate of typhoid fever was perceptibly diminished in this country and Europe.
Conspicuous as the achievements have been in bacteriology, it can not be said that the field is exhausted. There is hardly an infectious disease of the poultry yards which does not have to do with some bacterium or parasite, and the variations and adaptations of these pathogenic forms is to-day one of the difficult problems with which the avian pathologist has to deal. It is for the scientist to determine whether certain bacteria and parasites owe their pathogenic action to the organisms themselves or to their toxic or poisonous by-products. The field of immunity as related to avian pathology is unexplored. This would be among the most complicated that the scientist could undertake, yet the fields of bacteriology and parasitology with its many perfected methods of attack would indicate that it is not impossible. Not only human medicine, but also veterinary science owe much of their advancement to these two fields of knowledge. The scientific contributions of Neuman on parasites show that such organisms are the cause of many a dreadful disease, not only with man and animal, but with all avian life. The careful study of their life histories should appeal to our protozoologists and inspire them to contribute to our knowledge of those parasites which are causing an enormous mortality of our most valuable birds.
After the removal of a sick fowl from the flock a diagnosis is usually made. Very often the specific organism causing the infection is readily discovered, while, on the other hand, the most diligent scientific efforts may fail to reveal the character of the disease. Many failures are accountable because there is a lack of sufficient knowledge or a lack of thoroughness in making the investigation.
The fundamental difficulty in ascertaining more definite knowledge about our poultry diseases is the lack of enough scientific men to take hold of the situation. To-day we have no rational system of medical treatment for birds, nor can one be looked for until scientists, who are busy on anatomy and physiology of avian life, offer to the layman a definite plan of procedure, when these parasites and bacteria have made their way into the body and brought about pathological lesions.
The relation of bacteriology and parasitology to the infectious avian diseases as mentioned before, is fundamental. If bacteriologists and protozoologists will enter upon this field of avian diseases as a basis for their research in their respective fields, the results of their investigations will lead to an improvement in the conditions of our poultry yards, and give facts which are necessary before any treatment can be found. With men of this character at work upon avian pathology, success is inevitable.
- Circular 128 (1908), Bureau of Animal Industry, Dept. of Agriculture.
- Bulletin 60, Conn. Agr. Exp. Station.