Facts about disease vectors
![Human flea - Pulex irritans](/sites/default/files/styles/is_tile/public/images/human-flea-Pulex-irritans.png?itok=PMmYBIY9)
Fleas (Siphonaptera)
Fleas can transmit plague (caused by Yersinia pestis), murine typhus (caused by Rickettsia typhi), flea-borne spotted fever (Rickettsia felis), and cat scratch disease (Bartonella henselae).
![Developmental cycle of the human head louse](/sites/default/files/styles/is_tile/public/images/head-louse-developmental-cycle.jpg?itok=6-1rBK5o)
Lice (Phthiraptera)
Lice (Phthiraptera) are a very diverse group of insects, exclusively adapted to parasitism. Several thousand species have been described to date.