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Updated: Nov 2, 2025
Vector Competence Analyses on Aedes aegypti Mosquitoes using Zika Virus
Published on: May 31, 2020
Poor vector competence of the human flea, Pulex irritans, to transmit Yersinia pestis
Adélaïde Miarinjara1, David M Bland1, James R Belthoff2
1Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, NIH, Hamilton, MT, USA.
Background:
The human flea, Pulex irritans, is widespread globally and has a long association with humans, one of its principal hosts. Its role in plague transmission is still under discussion, although its high prevalence in plague-endemic regions and the presence of infected fleas of this species during plague outbreaks has led to proposals that it has been a significant vector in human-to-human transmission in some historical and present-day epidemiologic situations. However, based on a limited number of studies, P. irritans is considered to be a poor vector and receives very little attention from public health policymakers. In this study we examined the vector competence of P. irritans collected from foxes and owls in the western United States, using a standard protocol and artificial infection system.
Methods:
Wild-caught fleas were maintained in the laboratory and infected by allowing them to feed on human or rat blood containing 2 × 108 to 1 × 109 Y. pestis/ml. The fleas were then monitored periodically for infection rate and bacterial load, mortality, feeding rate, bacterial biofilm formation in the foregut (proventricular blockage), and ability to transmit Y. pestis after their single infectious blood meal.
Results:
P. irritans were susceptible to infection, with more than 30% maintaining high bacterial loads for up to 20 days. Transmission during this time was infrequent and inefficient, however. Consistent with previous studies, a low level of early-phase transmission (3 days after the infectious blood meal) was detected in some trials. Transmission at later time points was also sporadic, and the incidence of proventricular blockage, required for this mode of transmission, was low in fleas infected using rat blood and never occurred in fleas infected using human blood. The highest level of blockage and transmission was seen in fleas infected using rat blood and allowed to feed intermittently rather than daily, indicating that host blood and feeding frequency influence vector competence.
Conclusions:
Our results affirm the reputation of P. irritans as a feeble vector compared to rodent flea species examined similarly, and its vector competence may be lower when infected by feeding on bacteremic human blood.
Insights
The human flea, Pulex irritans, is a poor vector for plague transmission. Studies show it transmits Yersinia pestis infrequently, especially when feeding on human blood.
Area of Science:
- Vector-borne disease research
- Epidemiology
- Medical entomology
Background:
- The human flea, Pulex irritans, is globally distributed and historically associated with humans.
- Its role as a plague vector is debated, despite its prevalence in endemic areas and presence during outbreaks.
- Previous studies suggest P. irritans is an inefficient vector, receiving limited public health attention.
Purpose of the Study:
- To evaluate the vector competence of Pulex irritans for Yersinia pestis.
- To investigate the influence of host blood source and feeding frequency on transmission efficiency.
Main Methods:
- Wild-caught P. irritans were infected with Yersinia pestis via artificial feeding systems using human or rat blood.
- Fleas were monitored for infection rates, bacterial load, mortality, feeding success, and proventricular blockage.
- Transmission efficiency was assessed after a single infectious blood meal.
Main Results:
- Over 30% of P. irritans maintained high Yersinia pestis loads for up to 20 days.
- Transmission was infrequent and inefficient, with low early-phase transmission (3 days post-infection).
- Proventricular blockage, crucial for transmission, was low with rat blood and absent with human blood; intermittent feeding on rat blood increased blockage and transmission.
Conclusions:
- Pulex irritans demonstrates feeble vector competence compared to other flea species.
- Vector competence is influenced by host blood type and feeding patterns.
- Transmission efficiency is particularly low when infected by feeding on bacteremic human blood.
