PROLONGED STORAGE OF HUMAN PATHOGENIC PROTOZOA WITH CONSERVATION OF VIRULENCE

Abstract

Many of the protozoa of importance in tropical medicine may be stored for long periods in the frozen state at[long dash]70[degree]C. After thawing, these protozoa retain their original characteristics. They are motile, infectious and pathogenic for animals and may be propagated in cultures. These results have been obtained with the. following, stored for periods of months to a few yrs.: Trypanosoma rhodesiense, T. gambiense, T. cruzi and T. lewisi; Leishmania tropica and L. donovani; Trichomonas hominis; and Plasmodium lophurae. Successful results were also obtained with Leptospira icterohemorrhagiae and L. biflexa, with the microfilariae of Wuchereria bancrofti, Dirofilaria immitis and Litomosoides carinii, and with the infective larvae of Ancylostoma caninum and Strongyloides stercoralis. The method is simple, inexpensive, and allows for the maintenance of innumerable strains of protozoa with very little attention. There is little or no risk from loss through contamination, missed transfers or epidemics which are the chief hazards of the usual methods of maintenance in animals or cultures. It should prove of value in institutions where protozoa must be kept available over long periods of time.