Rickettsia diaporica: Recovery of Three Strains from Dermacentor andersoni Collected in Southeastern Wyoming: Their Identity with Montana Strain 1

Abstract

In the spring of 1938 three strains of a filter-passing infectious agent were recovered from D. andersoni collected from 2 areas in Albany County, SE Wyoming. One was recovered by injecting the tissues of 22 [male] and 37 [female] partly engorged ticks into a guinea-pig; one by similarly injecting 28 [male][male] and 23 [female][female] and the 3d by injecting 27 [male][male] and 29 [female][female]. Guinea-pigs receiving 1 cc. of a Berkefeld filtrate of blood serum from a 1st transfer guinea-pig showed definite febrile periods and enlarged spleens. Larvae from experimentally infected [female] D. andersoni when allowed to feed on normal guinea-pigs failed to produce the disease. However, in the nymphal and adult stages these ticks produced typical infections, thus showing the survival of the infectious agent from adult to adult and transmission by nymphs and adults. The clinical reactions in guinea-pigs, type lesions, staining reactions of the Rickettsia-like organisms in spleen impression slides and reciprocal cross-immunity tests indicate that these 3 strains are identical with each other and also identical with the Montana strain of R. diaporica reported recently by Davis and Cox.