Comparative Vector Competence of<i>Dermacentor variabilis</i>and<i>Ixodes scapularis</i>(Acari: Ixodidae) for the Agent of Human Granulocytic Ehrlichiosis

Vignes, Franka des; Levin, Michael; Fish, Durland

doi:10.1093/jmedent/36.2.182

Cited by 22 publications

(13 citation statements)

References 10 publications

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“…Granulocytic Ehrlichia and antibodies to E. phagocytophila have also been found in a variety of wild rodent species, including white-footed mice (7,11,33,35,43,45,47). Together with laboratory experiments (15,30,35,43), these findings show that the white-footed mouse is susceptible to E. phagocytophila and often exposed to infection in nature. However, its role in the natural cycle of E. phagocytophila remains unclear (30).…”

mentioning

confidence: 56%

Immunity Reduces Reservoir Host Competence ofPeromyscus leucopusforEhrlichia phagocytophila

Levin

Fish

2000

Infect Immun

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Infection with Ehrlichia phagocytophila in white-footed mice is transient and followed by a strong immune response. We investigated whether the presence of acquired immunity against E. phagocytophila precludes white-footed mice from further maintenance of this agent in nature. Mice were infected with E. phagocytophila via tick bite and challenged either 12 or 16 weeks later by Ixodes scapularis nymphs infected with the same agent. Xenodiagnostic larvae fed upon each mouse simultaneously with challenging nymphs and 1 week thereafter. Ticks were tested for the agent by PCR, and the prevalence of infection was compared to that in ticks that fed upon nonimmune control mice. Only 30% of immunized mice sustained cofeeding transmission of E. phagocytophila between simultaneously feeding infected and uninfected ticks, compared to 100% of control mice. An average of 6.3% of xenodiagnostic ticks acquired Ehrlichia from previously immunized mice when fed 1 week after the challenge, compared to 82.5% infection in the control group. Although an immune response to a single infection with E. phagocytophila in white-footed mice provided only partial protection against reinfection with the same agent, the majority of mice were rendered reservoir incompetent for at least 12 to 16 weeks. Immunity acquired by mice during I. scapularis nymphal activity in early summer may exclude a large proportion of the mouse population from maintaining E. phagocytophila during the period of larval activity later in the season.

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confidence: 56%

Immunity Reduces Reservoir Host Competence ofPeromyscus leucopusforEhrlichia phagocytophila

Levin

Fish

2000

Infect Immun

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“…PCR has been used to detect DNA of E. chaffeensis in other tick species, including the dog tick, Dermacentor variabilis (10,152,235), the Western blacklegged tick, Ixodes pacificus (152), Ixodes ricinus in Russia (4), and the ticks Amblyomma testudinarium and Haemaphysalis yeni collected from domesticated and wild animals in southern China (47). Detection of DNA of ehrlichiae within a particular tick species does not conclusively incriminate that tick as an efficient vector (83), and the role of these or other tick species as natural vectors of HME has not been established definitively. Similarly, the Gulf Coast tick (Amblyomma maculatum) has been implicated as a potential vector because of feeding proclivities and a range distribution similar to those of the lone star tick, although insufficient data exist to support or refute the role of this tick in the transmission of E. chaffeensis (149).…”

Section: Tick Vectorsmentioning

confidence: 98%

Ehrlichia chaffeensis:a Prototypical Emerging Pathogen

2003

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Ehrlichia chaffeensis is an obligately intracellular, tick-transmitted bacterium that is maintained in nature in a cycle involving at least one and perhaps several vertebrate reservoir hosts. The moderate to severe disease caused by E. chaffeensis in humans, first identified in 1986 and reported for more than 1,000 patients through 2000, represents a prototypical “emerging infection.” Knowledge of the biology and natural history of E. chaffeensis, and of the epidemiology, clinical features, and laboratory diagnosis of the zoonotic disease it causes (commonly referred to as human monocytic ehrlichiosis [HME]) has expanded considerably in the period since its discovery. In this review, we summarize briefly the current understanding of the microbiology, pathogenesis, and clinical manifestations associated with this pathogen but focus primarily on discussing various ecological factors responsible for the recent recognition of this important and potentially life-threatening tick-borne disease. Perhaps the most pivotal element in the emergence of HME has been the staggering increases in white-tailed deer populations in the eastern United States during the 20th century. This animal serves as a keystone host for all life stages of the principal tick vector (Amblyomma americanum) and is perhaps the most important vertebrate reservoir host for E. chaffeensis. The contributions of other components, including expansion of susceptible human populations, growth and broadening geographical distributions of other potential reservoir species and A. americanum, and improvements in confirmatory diagnostic methods, are also explored

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“…It also has been shown to be susceptible to infection with E. phagocytophila (5,16,21,32). Therefore, we used white-footed mice as hosts in our experiments.…”

Section: Methodsmentioning

confidence: 99%

Acquisition of Coinfection and Simultaneous Transmission of Borrelia burgdorferi and Ehrlichia phagocytophila by Ixodes scapularis Ticks

2000

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The agents of Lyme disease (Borrelia burgdorferi) and human granulocytic ehrlichiosis (Ehrlichia phagocytophila) are both transmitted by the tick Ixodes scapularis. In nature, ticks are often infected with both agents simultaneously. We studied whether previous infection with either Borrelia or Ehrlichia in ticks would affect acquisition and transmission of a second pathogen. Ehrlichia-infected I. scapularis nymphs were fed upon Borrelia-infected mice, and Borrelia-infected I. scapularis nymphs were fed upon Ehrlichia-infected mice. The efficiency with which previously infected nymphal ticks acquired a second pathogen from infected hosts was compared to that of uninfected ticks. An average of 51% ؎ 15% of ticks acquired Ehrlichia from infected mice regardless of their prior infection status with Borrelia. An average of 85% ؎ 10% of ticks acquired Borrelia from infected mice regardless of their prior infection status with Ehrlichia. Also, we assessed the efficiency with which individual nymphs could transmit either agent alone, or both agents simultaneously, to individual susceptible hosts. An average of 76% ؎ 9% of Borrelia-infected ticks and 84% ؎ 10% of Ehrlichia-infected ticks transmitted these agents to mice regardless of the presence of the other pathogen. There was no evidence of interaction between the agents of Lyme disease and human granulocytic ehrlichiosis in I. scapularis ticks. The presence of either agent in the ticks did not affect acquisition of the other agent from an infected host. Transmission of the agents of Lyme disease and human granulocytic ehrlichiosis by individual ticks was equally efficient and independent. Dually infected ticks transmitted each pathogen to susceptible hosts as efficiently as ticks infected with only one pathogen.The black-legged tick Ixodes scapularis is a vector of Borrelia burgdorferi, the etiologic agent of Lyme disease, as well as Ehrlichia phagocytophila, the etiologic agent of human granulocytic ehrlichiosis (HGE) (2, 4, 31, 32). In nature, nymphal and adult ticks are often infected with both agents simultaneously (3,16,29,33). Nymphal or adult ticks can acquire both pathogens simultaneously from a single coinfected host during either larval or nymphal feeding (M. Levin, unpublished data). Alternatively, adult ticks may have acquired pathogens consecutively-one during larval feeding and a second during nymphal feeding. In nature, the prevalence of either pathogen in ticks increases significantly from the nymphal to the adult stage, and consequently, the prevalence of coinfection in questing adult ticks can be 7 to 10 times higher than in nymphs (16). This observation suggests that consecutive acquisition of different pathogens by individual ticks may happen more frequently than simultaneous acquisition.Simultaneous infection with these two agents has also been documented in humans and rodents (16,(18)(19)(20). Infection with both agents may result from the bite of a single coinfected tick. However, there is no experimental evidence for simultaneous transmission...

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Comparative Vector Competence ofDermacentor variabilisandIxodes scapularis(Acari: Ixodidae) for the Agent of Human Granulocytic Ehrlichiosis

Cited by 22 publications

References 10 publications

Immunity Reduces Reservoir Host Competence ofPeromyscus leucopusforEhrlichia phagocytophila

Immunity Reduces Reservoir Host Competence ofPeromyscus leucopusforEhrlichia phagocytophila

Ehrlichia chaffeensis:a Prototypical Emerging Pathogen

Acquisition of Coinfection and Simultaneous Transmission of Borrelia burgdorferi and Ehrlichia phagocytophila by Ixodes scapularis Ticks

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