Co-Feeding Transmission of the Ehrlichia muris-Like Agent to Mice (Mus musculus)

Abstract

The Ehrlichia muris-like agent (EMLA) is a newly recognized human pathogen found in Wisconsin and Minnesota. Ecological investigations have implicated both the blacklegged tick, Ixodes scapularis, and the white-footed mouse, Peromyscus leucopus, as playing roles in the maintenance of EMLA in nature. The work presented here shows that I. scapularis is an efficient vector of EMLA in a laboratory mouse model, but that Dermacentor variabilis, another frequent human biting tick found in EMLA endemic areas, is not. Additionally, I. scapularis larvae are able to acquire EMLA through co-feeding with infected nymphs. As EMLA only persists in mouse blood for a relatively short period of time, co-feeding transmission may play an important role in the maintenance of EMLA in ticks, and subsequently may play a role in limiting the geographic distribution of this pathogen in areas where co-feeding of larvae and nymphs is less common.

Keywords: Co-feeding; Ehrlichia muris–like agent (EMLA); Ixodes scapularis; Peromyscus leucopus; Transmission.

FIG. 1

Detection of Ehrlichia muris–like agent (EMLA) in mouse blood following intraperitoneal (i.p.) infection with infected mouse lung. Shown is the average number of genomic copies (GC) of EMLA DNA detected in mouse blood following i.p. inoculation with 10³ and 10² genomic copies. The numbers in boxes pointing to the 10² data points indicate the number of animals tested at that time point. The numbers above the 10³ data points indicate the number of animals tested at that time point.

FIG. 2

Mouse mortality after intraperitoneal (i.p.) inoculation with Ehrlichia muris–like agent (EMLA) in infected mouse lung. Mouse mortality following i.p. inoculation with two different doses (10³ and 10² genomic copies [GC]) of EMLA.