Plague is an infectious disease caused by the bacterium Yersinia pestis. Symptoms include fever, weakness and headache. Usually this begins one to seven days after exposure. There are three forms of plague, each affecting a different part of the body and causing associated symptoms. Pneumonic plague infects the lungs, causing shortness of breath, coughing and chest pain; bubonic plague affects the lymph nodes, making them swell; and septicemic plague infects the blood and can cause tissues to turn black and die.
Yersinia pestis is a gram-negative, non-motile, coccobacillus bacterium without spores that is related to both Yersinia enterocolitica and Yersinia pseudotuberculosis, the pathogen from which Y. pestis evolved and responsible for the Far East scarlet-like fever. It is a facultative anaerobic organism that can infect humans via the Oriental rat flea. It causes the disease plague, which caused the Plague of Justinian and the Black Death, the deadliest pandemic in recorded history. Plague takes three main forms: pneumonic, septicemic, and bubonic. Yersinia pestis is a parasite of its host, the rat flea, which is also a parasite of rats, hence Y. pestis is a hyperparasite.
Flea, the common name for the order Siphonaptera, includes 2,500 species of small flightless insects that live as external parasites of mammals and birds. Fleas live by ingesting the blood of their hosts. Adult fleas grow to about 3 millimetres long, are usually brown, and have bodies that are "flattened" sideways or narrow, enabling them to move through their hosts' fur or feathers. They lack wings; their hind legs are extremely well adapted for jumping. Their claws keep them from being dislodged, and their mouthparts are adapted for piercing skin and sucking blood. They can leap 50 times their body length, a feat second only to jumps made by another group of insects, the superfamily of froghoppers. Flea larvae are worm-like, with no limbs; they have chewing mouthparts and feed on organic debris left on their hosts' skin.
Septicemic plague is one of the three forms of plague, and is caused by Yersinia pestis, a gram-negative species of bacterium. Septicemic plague is a systemic disease involving infection of the blood and is most commonly spread by bites from infected fleas. Septicemic plague can cause disseminated intravascular coagulation and is always fatal when untreated. The other varieties of the plague are bubonic plague and pneumonic plague.
Hymenolepiasis is infestation by one of two species of tapeworm: Hymenolepis nana or H. diminuta. Alternative names are dwarf tapeworm infection and rat tapeworm infection. The disease is a type of helminthiasis which is classified as a neglected tropical disease.
Hymenolepis diminuta, also known as rat tapeworm, is a species of Hymenolepis tapeworm that causes hymenolepiasis. It has slightly bigger eggs and proglottids than H. nana and infects mammals using insects as intermediate hosts. The adult structure is 20 to 60 cm long and the mature proglottid is similar to that of H. nana, except it is larger.
Tunga penetrans is a species of flea also known as the jigger, jigger flea, chigoe, chigo, chigoe flea, chigo flea, nigua, niknik, sand flea, or burrowing flea. It is a parasitic insect found in most tropical and sub-tropical climates. In its parasitic phase it has significant impact on its hosts, which include humans and certain other mammalian species. A parasitical infestation of T. penetrans is called tungiasis. Jiggers are often confused with chiggers, a type of mite. Jiggers are native to Central and South America, and have been introduced to sub-Saharan Africa.
Murine typhus, also known as endemic typhus or flea-borne typhus, is a form of typhus transmitted by fleas, usually on rats, in contrast to epidemic typhus which is usually transmitted by lice. Murine typhus is an under-recognized entity, as it is often confused with viral illnesses. Most people who are infected do not realize that they have been bitten by fleas. Historically the term "hunger-typhus" was used in accounts by British POWs in Germany at the end of World War I when they described conditions in Germany.
The cat flea is an extremely common parasitic insect whose principal host is the domestic cat, although a high proportion of the fleas found on dogs also belong to this species. This is despite the widespread existence of a separate and well-established "dog" flea, Ctenocephalides canis. Cat fleas originated in Africa but can now be found globally. As humans began domesticating cats, the prevalence of the cat flea increased and it spread throughout the world.
The discipline of medical entomology, or public health entomology, and also veterinary entomology is focused upon insects and arthropods that impact human health. Veterinary entomology is included in this category, because many animal diseases can "jump species" and become a human health threat, for example, bovine encephalitis. Medical entomology also includes scientific research on the behavior, ecology, and epidemiology of arthropod disease vectors, and involves a tremendous outreach to the public, including local and state officials and other stake holders in the interest of public safety.
Bubonic plague is one of three types of plague caused by the bacterium Yersinia pestis. One to seven days after exposure to the bacteria, flu-like symptoms develop. These symptoms include fever, headaches, and vomiting, as well as swollen and painful lymph nodes occurring in the area closest to where the bacteria entered the skin. Acral necrosis, the dark discoloration of skin, is another symptom. Occasionally, swollen lymph nodes, known as "buboes", may break open.
The human flea – once also called the house flea – is a cosmopolitan flea species that has, in spite of the common name, a wide host spectrum. It is one of six species in the genus Pulex; the other five are all confined to the Nearctic and Neotropical realms. The species is thought to have originated in South America, where its original host may have been the guinea pig or peccary.
Rickettsia typhi is a small, aerobic, obligate intracellular, rod shaped gram negative bacterium. It belongs to the typhus group of the Rickettsia genus, along with R. prowazekii. R. typhi has an uncertain history, as it may have long gone shadowed by epidemic typhus. This bacterium is recognized as a biocontainment level 2/3 organism. R. typhi is a flea-borne disease that is best known to be the causative agent for the disease murine typhus, which is an endemic typhus in humans that is distributed worldwide. As with all rickettsial organisms, R. typhi is a zoonotic agent that causes the disease murine typhus, displaying non-specific mild symptoms of fevers, headaches, pains and rashes. There are two cycles of R. typhi transmission from animal reservoirs containing R. typhi to humans: a classic rat-flea-rat cycle that is most well studied and common, and a secondary periodomestic cycle that could involve cats, dogs, opossums, sheep, and their fleas.
Operation Big Itch was a U.S. entomological warfare field test using uninfected fleas to determine their coverage and survivability as a vector for biological agents. The tests were conducted at Dugway Proving Ground in 1954.
The E14 munition was a cardboard sub-munition developed by the United States biological weapons program as an anti-crop weapon. In a series of field tests in 1955, the E14 was loaded with fleas and air-dropped.
The E23 munition was a cardboard sub-munition developed by the United States biological weapons program for use as an anti-crop weapon. The E23 underwent a conversion for use as a vector weapon and was briefly used in large-scale entomological warfare trial but technical issues forced it from the tests.
Echidnophaga gallinacea, also known as the hen flea or sticktight flea, is part of the 2,500 known flea types in the Siphonaptera order. Echidnophaga gallinacea appear dark brown in colour and is a small flea measuring approximately 2 millimetres in length, which is half the size of the common cat flea. Echidnophaga gallinacea also differ in anatomy compared to the cat flea due to lacking genal and pronotal combs known as ctenidia. Echidnophaga gallinacea like all fleas, have powerful hind legs which allow the flea to jump great distances compared to its size.
Nosopsyllus fasciatus, the northern rat flea, is a species of flea found on domestic rats and house mice. Northern rat fleas are external parasites, living by hematophagy off the blood of rodents. N. fasciatus can bite humans, but they are more common parasites of rodents. Since they are associated with humans, they are common disease vectors that can spread from animals to humans. Diseases that can be spread through fleas include the plague and typhus. The rat flea is widespread due to their relationship to rodents and other vertebrates. They can be found co-infecting their host with other parasites.
A rat flea is a parasite of rats.
The Pulicidae are a flea family in the order Siphonaptera. Currently, this family has 181 species in 27 genera. Of these, 16 are known from North America.
A whole slide image of the plague flea
Close-up of a female slide-mounted plague flea
Close-up of a male slide-mounted plague flea
