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Tissue distribution of the Ehrlichia muris-like agent in a tick vector.

Lynn GE, Oliver JD, Nelson CM, Felsheim RF, Kurtti TJ, Munderloh UG - PLoS ONE (2015)

Bottom Line: While the latter has been investigated to a greater extent, examination of the biological interactions between microbes and the ticks that carry them presents an equally important opportunity for disruption of the disease cycle.In this study, we used in situ hybridization to demonstrate infection by the Ehrlichia muris-like organism, a newly recognized human pathogen, of Ixodes scapularis ticks, a primary vector for several important human disease agents.This allowed us to assess whole sectioned ticks for the patterns of tissue invasion, and demonstrate generalized dissemination of ehrlichiae in a variety of cell types and organs within ticks infected naturally via blood feeding.

View Article: PubMed Central - PubMed

Affiliation: Department of Entomology, University of Minnesota, 219 Hodson Hall, 1980 Folwell Ave., St. Paul, MN 55108, United States of America.

ABSTRACT
Human pathogens transmitted by ticks undergo complex life cycles alternating between the arthropod vector and a mammalian host. While the latter has been investigated to a greater extent, examination of the biological interactions between microbes and the ticks that carry them presents an equally important opportunity for disruption of the disease cycle. In this study, we used in situ hybridization to demonstrate infection by the Ehrlichia muris-like organism, a newly recognized human pathogen, of Ixodes scapularis ticks, a primary vector for several important human disease agents. This allowed us to assess whole sectioned ticks for the patterns of tissue invasion, and demonstrate generalized dissemination of ehrlichiae in a variety of cell types and organs within ticks infected naturally via blood feeding. Electron microscopy was used to confirm these results. Here we describe a strong ehrlichial affinity for epithelial cells, neuronal cells of the synganglion, salivary glands, and male accessory glands.

No MeSH data available.


Related in: MedlinePlus

Whole tick sections subjected to ISH assay.(A) Acini and salivary ducts of infected adult female SB = 1μm. (B) Spermatozoa of adult male with infected lining sheath. SB = 1μm. (C) Infected adult male accessory gland (single lobe). SB = 2μm. (D) Infected adult male accessory gland (multiple lobes). SB = 10μm.
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pone.0122007.g002: Whole tick sections subjected to ISH assay.(A) Acini and salivary ducts of infected adult female SB = 1μm. (B) Spermatozoa of adult male with infected lining sheath. SB = 1μm. (C) Infected adult male accessory gland (single lobe). SB = 2μm. (D) Infected adult male accessory gland (multiple lobes). SB = 10μm.

Mentions: Microscopic examination of sectioned I. scapularis that had undergone ISH demonstrated great variability in bacterial load between individual ticks. While many ticks showed broadly disseminated infections that were easily visible by bright field microscopy facilitated by the chromogenic label, in others, infection load was light enough to require the use of fluorescent microscopy to detect probe signal (Fig. 1A, bright-field). Light infection loads were those in which few small morulae were scattered throughout tissues or restricted to one or two organs, and no obvious pathogenic changes were observed. Heavy infection loads (Fig. 1B) were defined as those that affected the entire tick, including leg muscle, synganglion, salivary glands and male accessory glands, and induced significant and wide-spread tissue damage. Because of the predilection of E. muris for the male accessory glands, males were always considered heavily infected. Females and nymphs observed in this study displayed similar infection patterns, with several individuals of each group showing widespread infection throughout their anatomy. While ehrlichiae were found in tissues throughout the tick, they appeared to preferentially invade epithelial cells. Salivary glands (Fig. 2A & Fig. 3), outer cortex regions of the synganglion (central nervous system) (Fig. 1C) and epithelial cells surrounding the tracheal complex (Fig. 4A & 4B) were the most frequent sites of infection among the ticks sampled. Interestingly, some salivary gland acini harbored large numbers of ehrlichiae, while neighboring clusters were lightly or uninfected, suggesting a possible tropism for specific types of acini that was further supported by TEM findings in this study [15,43]. Similarly, we consistently observed ehrlichiae in cells forming the peripheral cortical region of the synganglion while the internal neuropile was largely free of morulae or contained a few scattered groups of bacteria (Fig. 1C). Ovarian tissues showed no evidence of active infection, an unsurprising observation given that transovarial transmission has not been observed within the genus Ehrlichia [44].


Tissue distribution of the Ehrlichia muris-like agent in a tick vector.

Lynn GE, Oliver JD, Nelson CM, Felsheim RF, Kurtti TJ, Munderloh UG - PLoS ONE (2015)

Whole tick sections subjected to ISH assay.(A) Acini and salivary ducts of infected adult female SB = 1μm. (B) Spermatozoa of adult male with infected lining sheath. SB = 1μm. (C) Infected adult male accessory gland (single lobe). SB = 2μm. (D) Infected adult male accessory gland (multiple lobes). SB = 10μm.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4363788&req=5

pone.0122007.g002: Whole tick sections subjected to ISH assay.(A) Acini and salivary ducts of infected adult female SB = 1μm. (B) Spermatozoa of adult male with infected lining sheath. SB = 1μm. (C) Infected adult male accessory gland (single lobe). SB = 2μm. (D) Infected adult male accessory gland (multiple lobes). SB = 10μm.
Mentions: Microscopic examination of sectioned I. scapularis that had undergone ISH demonstrated great variability in bacterial load between individual ticks. While many ticks showed broadly disseminated infections that were easily visible by bright field microscopy facilitated by the chromogenic label, in others, infection load was light enough to require the use of fluorescent microscopy to detect probe signal (Fig. 1A, bright-field). Light infection loads were those in which few small morulae were scattered throughout tissues or restricted to one or two organs, and no obvious pathogenic changes were observed. Heavy infection loads (Fig. 1B) were defined as those that affected the entire tick, including leg muscle, synganglion, salivary glands and male accessory glands, and induced significant and wide-spread tissue damage. Because of the predilection of E. muris for the male accessory glands, males were always considered heavily infected. Females and nymphs observed in this study displayed similar infection patterns, with several individuals of each group showing widespread infection throughout their anatomy. While ehrlichiae were found in tissues throughout the tick, they appeared to preferentially invade epithelial cells. Salivary glands (Fig. 2A & Fig. 3), outer cortex regions of the synganglion (central nervous system) (Fig. 1C) and epithelial cells surrounding the tracheal complex (Fig. 4A & 4B) were the most frequent sites of infection among the ticks sampled. Interestingly, some salivary gland acini harbored large numbers of ehrlichiae, while neighboring clusters were lightly or uninfected, suggesting a possible tropism for specific types of acini that was further supported by TEM findings in this study [15,43]. Similarly, we consistently observed ehrlichiae in cells forming the peripheral cortical region of the synganglion while the internal neuropile was largely free of morulae or contained a few scattered groups of bacteria (Fig. 1C). Ovarian tissues showed no evidence of active infection, an unsurprising observation given that transovarial transmission has not been observed within the genus Ehrlichia [44].

Bottom Line: While the latter has been investigated to a greater extent, examination of the biological interactions between microbes and the ticks that carry them presents an equally important opportunity for disruption of the disease cycle.In this study, we used in situ hybridization to demonstrate infection by the Ehrlichia muris-like organism, a newly recognized human pathogen, of Ixodes scapularis ticks, a primary vector for several important human disease agents.This allowed us to assess whole sectioned ticks for the patterns of tissue invasion, and demonstrate generalized dissemination of ehrlichiae in a variety of cell types and organs within ticks infected naturally via blood feeding.

View Article: PubMed Central - PubMed

Affiliation: Department of Entomology, University of Minnesota, 219 Hodson Hall, 1980 Folwell Ave., St. Paul, MN 55108, United States of America.

ABSTRACT
Human pathogens transmitted by ticks undergo complex life cycles alternating between the arthropod vector and a mammalian host. While the latter has been investigated to a greater extent, examination of the biological interactions between microbes and the ticks that carry them presents an equally important opportunity for disruption of the disease cycle. In this study, we used in situ hybridization to demonstrate infection by the Ehrlichia muris-like organism, a newly recognized human pathogen, of Ixodes scapularis ticks, a primary vector for several important human disease agents. This allowed us to assess whole sectioned ticks for the patterns of tissue invasion, and demonstrate generalized dissemination of ehrlichiae in a variety of cell types and organs within ticks infected naturally via blood feeding. Electron microscopy was used to confirm these results. Here we describe a strong ehrlichial affinity for epithelial cells, neuronal cells of the synganglion, salivary glands, and male accessory glands.

No MeSH data available.


Related in: MedlinePlus