Pulex irritans Or the Human Flea
Pulex irritans Or the Human Flea
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A Parasitic Relationship
Physical Characteristics
Physical Characteristics
Pulex irritans (Human Flea) begin their life as an oval white egg, hatching into 2mm long larvae5 within a week. These larvae are able to feed on blood and the feces of other fleas growing to 4-5mm long5. Larvae Then spin a cocoon to pupate, protecting them from the environment while it develops into an adult flea6. Adult Fleas exhibit a reddish brown color, and sexual dimorphism, with females being approximately 3 mm in length and males being 2.25 mm7. Adults also have an exoskeleton of hard plates that makes them incredibly resistant to being crushed.
Range, Habitat and Diet
Truly replicating the spread of its preferred host species, humans, Pulex irritans have a globe spanning geographical range, with the only exception in the arctic7. Once human fleas reach adulthood, their diet consists of blood, and have a parasitic relationship with mammals. Eggs typically fall off the host and live in its clothing and bedding.
This video provides great visuals on the different life stages of fleas, and touches on how different flea species have their own preferred host. Not surprisingly, the human fleas preferred host is Homo sapiens8.
A Historical Relationship
Fleas as a whole have a contentious relationship with humans throughout our history given their parasitic relationship with us. Historically, the Oriental Rat Flea (Xenopsylla cheopis) has been the vector for human infections of black death, as a result of rats being the reservoir species for Yersinia pestis, the bacteria responsible for the death of 30-50% of Europe's population9.
Modern Plague infections
Pulex irritans typically has a lower chance to be carrying plague10, given that their preferred host humans, and not rats. This means that they serve as a vector for human to human transmission in most cases. That being said though, fleas are opportunistic feeders, and will consume rat blood if it is the only food source available, infecting them with plague, and then making them much more likely to infect humans when they finally do reach their preferred food source.
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