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Background <p><i>Amblyomma variegatum</i> threatens the Caribbean cattle industry owing to its role as a vector for <i>Ehrlichia ruminantium</i>, the obligate intracellular bacterium that causes heartwater disease, an economically important and potentially fatal ruminant disease. <i>Amblyomma variegatum</i> is also a public health concern as a vector for <i>Rickettsia africae</i>, the causative agent of African tick-bite fever. Efforts to eradicate <i>A. variegatum</i> on Caribbean islands are ongoing to protect cattle from disease and prevent the spread of the vector and diseases to the American mainland. However, reinfestations often occur, possibly owing to the maintenance of ticks by non-cattle hosts that escape treatment. St. Croix in the US Virgin Islands has experienced such eradication challenges.</p> Methods <p>To determine whether persistence of <i>A. variegatum</i> populations on non-cattle hosts contributes to cattle reinfestation on St. Croix, we analyzed 1 non-attached <i>A. variegatum</i> adult female collected from a human and 14 questing adult females collected via cloth dragging along vegetation transects in Lower Love, St. Croix, during 2023. We conducted host bloodmeal analysis by obtaining vertebrate cytochrome c oxidase subunit I (<i>COI</i>) sequences from <i>A. variegatum</i> DNA extracts using <i>COI</i>-targeted DNA capture and enrichment to identify the most recent host bloodmeal. We also screened tick DNA extracts for <i>E. ruminantium</i> and <i>Rickettsia</i> DNA using <i>pCS20</i> Sol1 and PanR8 qPCR, respectively. <i>Rickettsia</i> species identification was determined using <i>ompA</i> polymerase chain reaction (PCR) and Sanger sequencing, followed by phylogenetic analysis.</p> Results <p>We identified vertebrate <i>COI</i> sequences for the genera <i>Capra</i> and <i>Canis</i> in two <i>A. variegatum</i> ticks. Although <i>E. ruminantium</i> was not detected, DNA from <i>R. africae</i> was present in all 15 ticks.</p> Conclusions <p>These results suggest that goats, and possibly canines, may serve as alternative hosts for <i>A. variegatum</i> on St. Croix, US Virgin Islands, which complicates eradication efforts focused entirely on the treatment of cattle. Fortunately, <i>E. ruminantium</i> was not identified in any ticks. However, <i>R. africae</i> was ubiquitous, which may be of concern for public health.</p> Graphical Abstract <p></p>

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Bloodmeal analysis via COI-targeted DNA capture and enrichment identifies non-cattle hosts of Amblyomma variegatum on St. Croix, US Virgin Islands

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年3月26日

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  • Rebecca Ballard,
  • Charles H. D. Williamson,
  • Hayden Kleinschmidt,
  • Greta Buckmeier,
  • Jason W. Sahl,
  • Pia U. Olafson,
  • Jeffery T. Alfred,
  • Joseph D. Busch,
  • David M. Wagner,
  • Denise Bonilla,
  • Nathan E. Stone

摘要

Background

Amblyomma variegatum threatens the Caribbean cattle industry owing to its role as a vector for Ehrlichia ruminantium, the obligate intracellular bacterium that causes heartwater disease, an economically important and potentially fatal ruminant disease. Amblyomma variegatum is also a public health concern as a vector for Rickettsia africae, the causative agent of African tick-bite fever. Efforts to eradicate A. variegatum on Caribbean islands are ongoing to protect cattle from disease and prevent the spread of the vector and diseases to the American mainland. However, reinfestations often occur, possibly owing to the maintenance of ticks by non-cattle hosts that escape treatment. St. Croix in the US Virgin Islands has experienced such eradication challenges.

Methods

To determine whether persistence of A. variegatum populations on non-cattle hosts contributes to cattle reinfestation on St. Croix, we analyzed 1 non-attached A. variegatum adult female collected from a human and 14 questing adult females collected via cloth dragging along vegetation transects in Lower Love, St. Croix, during 2023. We conducted host bloodmeal analysis by obtaining vertebrate cytochrome c oxidase subunit I (COI) sequences from A. variegatum DNA extracts using COI-targeted DNA capture and enrichment to identify the most recent host bloodmeal. We also screened tick DNA extracts for E. ruminantium and Rickettsia DNA using pCS20 Sol1 and PanR8 qPCR, respectively. Rickettsia species identification was determined using ompA polymerase chain reaction (PCR) and Sanger sequencing, followed by phylogenetic analysis.

Results

We identified vertebrate COI sequences for the genera Capra and Canis in two A. variegatum ticks. Although E. ruminantium was not detected, DNA from R. africae was present in all 15 ticks.

Conclusions

These results suggest that goats, and possibly canines, may serve as alternative hosts for A. variegatum on St. Croix, US Virgin Islands, which complicates eradication efforts focused entirely on the treatment of cattle. Fortunately, E. ruminantium was not identified in any ticks. However, R. africae was ubiquitous, which may be of concern for public health.

Graphical Abstract