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.
A human pathogen is a pathogen that causes disease in humans.
Yersinia pestis is a gram-negative, non-motile, coccobacillus bacterium without spores that is related to both Yersinia pseudotuberculosis and Yersinia enterocolitica. It is a facultative anaerobic organism that can infect humans via the Oriental rat flea. It causes the disease plague, which caused the first plague pandemic 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.
The echidna flea is the larger of two species of flea commonly found on the short-beaked echidna. It is monotypic, that is, the only species in the genus. This flea reaches 4 millimetres in length and has been claimed to be the world's largest flea. This statement is in error as the world's largest flea is known to be the mountain beaver flea which can be as large as 12 millimetres in length.
The Oriental rat flea, also known as the tropical rat flea or the rat flea, is a parasite of rodents, primarily of the genus Rattus, and is a primary vector for bubonic plague and murine typhus. This occurs when a flea that has fed on an infected rodent bites a human, although this flea can live on any warm blooded mammal.
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.
The northern grasshopper mouse is a North American carnivorous rodent of the family Cricetidae. It ranges over much of the western part of the continent, from southern Saskatchewan and central Washington to Tamaulipas in northeast Mexico.
Bubonic plague is one of three types of plague caused by the plague bacterium. 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.
Theories of the Black Death are a variety of explanations that have been advanced to explain the nature and transmission of the Black Death (1347–51). A number of epidemiologists from the 1980s to the 2000s challenged the traditional view that the Black Death was caused by plague based on the type and spread of the disease. The confirmation in 2010 and 2011 that Yersinia pestis DNA was associated with a large number of plague sites has led researchers to conclude that "Finally, plague is plague."
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.
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.
The dog flea is a species of flea that lives as an ectoparasite on a wide variety of mammals, particularly the domestic dog and cat. It closely resembles the cat flea, Ctenocephalides felis, which can live on a wider range of animals and is generally more prevalent worldwide.
Cat-scratch disease (CSD) or felinosis is an infectious disease that most often results from a scratch or bite of a cat. Symptoms typically include a non-painful bump or blister at the site of injury and painful and swollen lymph nodes. People may feel tired, have a headache, or a fever. Symptoms typically begin within 3–14 days following infection.
Ceratophyllus gallinae, known as the hen flea in Europe or the European chicken flea elsewhere, is an ectoparasite of birds. This flea was first described by the German botanist and entomologist Franz von Paula Schrank in 1803.
Hystrichopsylla schefferi, also known as the mountain beaver flea and giant mountain beaver flea, is a parasitic nearctic insect belonging to the order Siphonaptera, the fleas. With an adult body length of as much as 0.5 inches (13 mm), it is the largest living flea in the world, and is native to the American Northwest. Though most members of the genus Hystrichopsylla are not strongly associated with any particular host animal and will parasitize insectivores and rodents generally, H. schefferi is monoxenously associated with the mountain beaver with which its range is coterminous. The fleas of the family Hystrichopsyllidae, along with the family Pulicidae, are the oldest of fleas in evolutionary history. H. schefferi can be distinguished from the very similar and closely related species Hystrichopsylla gigas dippiei by the number of spines in the pronotal comb, as H. g. dippiei has 36 and H. schefferi has 46.
Madagascar has experienced several outbreaks of bubonic and pneumonic plague in the 21st century. In the outbreak beginning in 2014, 71 died; in 2017, 202 died. Smaller outbreaks occurred in January 2008, and December 2013.
