Taxonomy of trypanosomes (Protozoa: Trypanosomatidae) ofSpermophilusspp. (Rodentia: Sciuridae)

Abstract

(1)Spermophilus columbianus, S. franklinii, S. lateralis tescorum, S. richardsonii, S. tridecemlineatusands. undulatus plesius(ground squirrels) were collected from Alberta and Yukon Territory (S. u. plesiusonly), Canada. Trypanosome infections were detected in all butS. l. tescorum. (2) All six species of squirrels were experimentally inoculated with trypanosomes from naturally infectedS. columbianus, S. franklinii, S. richardsoniiandS. tridecemlineatus. The strains fromS. columbianus, S. richardsoniiandS. tridecemlineatusproduced infections in some or all of the other host species, whereas the strain fromS. frankliniidid not. (3) Natural transmission of trypanosomes has not been demonstrated, but it seems likely that fleas act as vectors. (4) Intensities and durations of experimental infections were variable and depended upon the trypanosome strain, host species and individual. Infections were non-pathogenic. (5) Previously infected ground squirrels could not be reinfected with the same or a different trypanosome strain and immunity appeared to be lifelong. (6) Size comparisons among and within trypanosome strains from naturally and experimentally infected ground squirrels revealed that the strains fromS. frankliniiandS. tridecemlineatuswere similar to one another, but different from the other three trypanosome strains (those fromS. columbianus, S. richardsoniiandS. undulatus). (7) It is suggested that there is only one species of trypanosome,Trypanosoma otospermophili, in the genusSpermophilusin North America and that differences in size and types of infection are due to host-induced variations (i.e. they are plastoxenodemes).T. spermophili(present in EurasianSpermophilusspp.) might be synonymous withT. otospermophili.