Sexual dimorphism of the Lyme disease bacterium in its tick vector – Abundance of Borrelia burgdorferi is higher in female than male Ixodes scapularis larvae
Bibliographic record
Abstract
BACKGROUND: In North America, the tick-borne spirochete Borrelia burgdorferi sensu stricto (ss) causes Lyme disease and is transmitted by the blacklegged tick, Ixodes scapularis. Acquisition and transmission of B. burgdorferi ss occur during blood feeding, which is done by three tick stages, larvae, nymphs, and adults. Sex-specific differences in tick body size and blood feeding behaviour may influence transmission of tick-borne pathogens. However, sex-specific molecular markers are needed for sex determination of immature ticks. The objective of this study was to determine whether tick sex influences the acquisition and abundance of B. burgdorferi ss in immature I. scapularis ticks. METHODS: Uninfected or B. burgdorferi-infected larvae and nymphs were fed on B. burgdorferi-infected or uninfected lab mice and allowed to moult into the next stage. The sex of immature and adult ticks was determined using sex-specific PCR. The presence and abundance of B. burgdorferi in ticks were determined using 23S rRNA qPCR, and the amount of tick tissue was determined using tick calreticulin qPCR. RESULTS: There was no difference in acquisition of B. burgdorferi between immature male and female I. scapularis. In engorged larvae, the spirochete load was 45.7 % higher in female larvae compared to male larvae, and this difference was significant. In 4-week-old unfed nymphs, the spirochete load was 7.4 % higher in female nymphs compared to male nymphs, but this difference was not significant. In engorged larvae, the tick calreticulin gene content was similar between the sexes, whereas in unfed nymphs, the calreticulin gene content was 12.6 % higher in females than males, suggesting that female nymphs are larger. In adult ticks, female ticks weighed more, had higher calreticulin gene content, and higher spirochete loads than adult male ticks. Future studies should investigate whether tick sex influences the vector competence of Ixodes ticks for other tick-borne pathogens.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".