THE ICHTHYOPHTHIRIUS DISEASE OF FISHES AND METHODS 



OF CONTROL/ 



Ry Herbert F. Prytherch, Scientific Assistant, U. S. Bureau of Fisheries.' 



CONTENTS. 



Page. 



Introduction 1 



Occurrence of the disease 1 



Symptoms of tlie disease 2 



Description of tlie parasite 2 



Life liistory of tlie parasite 2 



Treatment and control of tlie disease 4 



Economic importance 6 



INTRODUCTION. 



The unusual occurrence of the parasitic ciliate, Ichthyophthirius 

 multifiliis (Fouquet), on fish in the Washington aquarium during 

 the cold winter months led to a series of experiments to determine 

 more efficient methods of combating the disease. Catfish, bass, bream, 

 and sunfish that were brought in from Maryland waters and the 

 Potomac River in the late fall were found, after a week's confine- 

 ment in the aquaria, to be heavily infected with the parasite. The 

 steadily lowering temperature did not halt the disease, but only 

 served to render its treatment more difficult. 



OCCURRENCE OF THE DISEASE. 



The parasitic protozoan Ichthyophythirius is found on fish in 

 their natural environment as well as on fish in aquaria and artificial 

 ponds. In nature fish seldom are killed by the disease, as the pos- 

 sibility of heavy infection by the young parasites is greatly reduced 

 by the large expanse of water and the movements of the fish. 



Serious epidemics have occurred from time to time in France, 

 Holland, and Germany, and in various sections of the United. 

 States. The disease was first recorded in 1869 in the Zoological 

 Garden in Hamburg. Germany, and in France in 1876, where care- 

 ful observations were made and the name I chthyophthirius muTti- 

 fUis proposed by Fouquet. In America the parasite is prevalent in 

 small ponds, resei-voirs. and aquaria, where it spreads rapidly, caus- 

 ing a heavy mortality of most of our common fresh-water fishes. 



^Appendix IX to the Roport of "the U. S. f'onnnissioner of Fisherios for 1923. B. F. 

 Doc. No. 0.59. 



* The author is particularly indebted to Dr. H. S. Davis, fish pathologist of the Bureau 

 of Fisheries, for critici>;m in reviewing the manuscript and for suggestions during the 

 course of the work. 



81178°— 24 1 



