We have just passed flea bite season. Hopefully, it was productive for you and you weren’t bitten. Speaking of bitten, have you wondered what happens when a flea bites its host? How does such a small insect have the ability to spread diseases?
The mouthparts of a flea are described as piercing/sucking, which describes how they work — sort of. There are three parts of the mouth that pierce the skin. They’re called stylets. A stylet is a slender, rigid appendage in the mouth used to pierce the skin of the host. The first two are found on either side of the mouth. They work in unison to saw — or more accurately punch like a hammer drill — into the skin. Once they’re through, the third stylet is inserted in the opening and joins the first two to form a feeding channel into which blood is drawn for the insect to feed.
In 1946, researcher Robert Snodgrass described this configuration of the mouthparts as unique in the flea. The action of the first two stylets will cause the host to bleed or they’ll pierce a blood vessel. When the third stylet is introduced, the flea will inject saliva into the wound. This saliva contains anticoagulants to keep the blood flowing and an enzyme to keep blood platelets from aggregating at the wound site. This saliva could also contain bacterial components that might be in the gut of the flea, which is where disease transmission starts.
The flea prefers to feed directly from a blood vessel but will feed from pooled blood under the skin. Because of this, saliva can be injected directly into the bloodstream of the host, so the disease transmission occurs faster. But a bite isn’t the only way the disease organisms can enter the host body. In the case of Yersinia pestis, the bacteria responsible for the plague. The bacterium also exists in the feces of the flea. So when the flea is on host and defecates, and the host scratches the bite wound, the bacterium can be introduced into the blood mechanically by wiping or grinding the feces into the wound. The bacteria can’t be digested by the flea, so when it feeds, it can regurgitate the bacteria from the gut into the wound.
Here’s where to find additional information about the flea and some of its more unique abilities and functions:
- General Summary of Siphonaptera: www.faculty.ucr.edu/~legneref/entomol/siphonaptera.htm
- The Evolution of Flea-borne Transmission in Y. pestis by B. Joseph Hinnebusch: www.ncbi.nlm.nih.gov/pubmed/16053250
You can reach Meek, international technical and training director for Orkin, at email@example.com