''Nosopsyllus fasciatus'', the northern rat flea, is a species of

flea 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 long, ...

found on

domestic rat The fancy rat (''Rattus norvegicus domestica'') is the domesticated form of ''Rattus norvegicus'', the brown rat, and the most common species of rat kept as a pet. The name ''fancy rat'' derives from the use of the noun ''fancy'' for a hobby, ...

s and

house mice The house mouse (''Mus musculus'') is a small mammal of the order Rodentia, characteristically having a pointed snout, large rounded ears, and a long and almost hairless tail. It is one of the most abundant species of the genus ''Mus''. Although ...

. Northern rat fleas are external

parasites Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson ha ...

, living by hematophagy off the

blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the cir ...

rodent Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are n ...

s. ''N. fasciatus'' can bite humans, but they are more common parasites of rodents.Zurita, A., Callejon, R., de Rojas, M. and Cutillas, C.. 2017. Morphological and molecular study of the genus ''Nosopsyllus'' (Siphonaptera: Ceratophyllidae). ''Nosopsyllus barbarus'' (Jordan & Rothschild 1912) as a junior synonym of ''Nosopsyllus fasciatus'' (Bosc d’Antic, 1800). Insect Systematics & Evolution. 49(1): pp.81-101. 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 Typhus, also known as typhus fever, is a group of infectious diseases that include epidemic typhus, scrub typhus, and murine typhus. Common symptoms include fever, headache, and a rash. Typically these begin one to two weeks after exposure. ...

. 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. It is the most widely spread of its genus, having originated in Europe, but has been transported to temperate regions worldwide. The genus, ''Nosopsyllus'', contains sixty-eight

taxa In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...

, which is then divided into four categories ''Nosopsyllus'', ''Gerbillophilus'', ''Nosinius'', and ''Penicus''.

Identification

''N. fasciatus'' characteristically look similar to other ''Nosopsyllus'' species. Like others of this genus, this species is laterally flattened, has well-developed eyes, and a rounded head. ''N. fasciatus'' has an elongated body, 3 to 4 mm in length. It has six posterior and six anterior head bristles containing three long and three short bristles. A distinguishing feature is that the dorsal bristle in the posterior row on the head is long but there is a characteristic short bristle immediately ventral to the dorsal bristle.

Distribution

''N. fasciatus'' is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...

to Europe but has a worldwide distribution because of their dependence on rodents and other

mammals Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur o ...

for survival.>Crooks, K.R., Garcelon, D.K., Scott, C.A., Depue, J.E., Wilcox, J.T., Kimsey, R.B. and Van Vuren, D.H.. 2004. Ectoparasites of a threatened insular endemic mammalian carnivore: the island spotted skunk. The American midland naturalist. 151(1): pp.35-41. The genus, ''Nosopsyllus'', is native to the

Palearctic Realm The Palearctic or Palaearctic is the largest of the eight biogeographic realms of the Earth. It stretches across all of Eurasia north of the foothills of the Himalayas, and North Africa. The realm consists of several bioregions: the Euro-Si ...

but has spread through human transportation to other regions of the world. The cause of this human-facilitated spread of ''N. fasciatus'' was most likely due to the globalization of trade. Other areas populated by ''N. fasciatus'' are the United States, including some islands that have been spread from the mainland.Schwan, T.G.. 1984. ''Nosopsyllus fasciatus'' parasitizing house mice on southeast Farallon Island. California (Siphonaptera: Ceratophyllidae). Pan-Pac. Entomol. 60: pp.345-349. The cause of the spread is due to rats escaping from the mainland to the island through boats. The islands such as the

San Miguel Island San Miguel Island (Chumash: ''Tuqan'') is the westernmost of California's Channel Islands, located across the Santa Barbara Channel in the Pacific Ocean, within Santa Barbara County, California. San Miguel is the sixth-largest of the eight Ch ...

and

Hawaii Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only stat ...

have been inhabited by rats that carry this species. ''N. fasciatus'' is successful in spreading to new areas because it is a generalist and can colonize a new area and adapt easily.

Anatomy

The rat flea has three

instar An instar (, from the Latin '' īnstar'', "form", "likeness") is a developmental stage of arthropods, such as insects, between each moult (''ecdysis''), until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or ...

stages in its development.>Elbel, R.E.. 1951. Comparative studies on the larvae of certain species of fleas (Siphonaptera). The Journal of Parasitology. 37(2): pp.119-128. The flea larva has two

pharynx The pharynx (plural: pharynges) is the part of the throat behind the mouth and nasal cavity, and above the oesophagus and trachea (the tubes going down to the stomach and the lungs). It is found in vertebrates and invertebrates, though its st ...

chambers, where the posterior one is important for suction.Sharif, M.. 1937. VII-On the internal anatomy of the larva of the Rat-flea, ''Nosopsyllus fasciatus'' (Bosc). Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences. 227(547): pp.465-538. After each

moulting In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is the manner in which an animal routinely casts off a part of its body (often, but not always, an outer ...

period, there is a cost of partial replacement of digestive cells for the new regenerative cells produced during this period. The larva has a two-chambered poorly-developed heart with a dorsal blood vessel.

Larval Feeding Behaviour

Larval ''N. fasciatus'' feed on adult fleas through attachment or on injured individuals.Molyneux, D.H.. 1967. Feeding Behaviour of the Larval Rat Flea ''Nosopsyllus fasciatus'' Bosc. Nature. 215(5102): pp.779-779. In the nest, larval fleas are observed to remain near adults in the debris. Larvae will attach to the posterior end of adults with their mandibles (insect mouthpart). The larva receives nutrients when the adult defecates, which contains blood within the fecal matter. The blood meal is ingested by a sucking action performed by the larvae. If the cuticle of the adult has been injured, the larvae can attack and eat the body of the injured adult. This behaviour categorizes ''N. fasciatus'' larvae as semi-predatory and displays opportunist cannibalism behaviour.

Pathology

Though the northern rat flea primarily parasitizes the Norway rat, ''Rattus norvegicus'', it has occasionally been observed feeding on humans and wild rodents. It is a vector for

plague Plague or The Plague may refer to: Agriculture, fauna, and medicine *Plague (disease), a disease caused by ''Yersinia pestis'' * An epidemic of infectious disease (medical or agricultural) * A pandemic caused by such a disease * A swarm of pes ...

and is known to be a host of the

rat tapeworm ''Hymenolepis diminuta'', also known as rat tapeworm, is a species of ''Hymenolepis (tapeworm), Hymenolepis'' tapeworm that causes hymenolepiasis. It has slightly bigger eggs and proglottids than ''Hymenolepis nana, H. nana'' and infects ma ...

''Hymenolepis diminuta'' in

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sou ...

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

, and

Australia Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...

. Rodents acts as the primary host for flea species and parasitized rodents account for 25% of all mammals.

Effect on Flea

Plague transmission causes a blockage in the stomach of ''N. fasciatus''.Eskey, C.R., Prince, F.M. and Fuller, F.B.. 1951. Double infection of the rat fleas ''X. cheopis'' and ''N. fasciatus'' with Pasteurella and Salmonella. Public Health Reports. (1896-1970): pp.1318-1326. This blockage is caused by a mass formation in the proventriculus. However, a study revealed that a simultaneous ''

Salmonella ''Salmonella'' is a genus of rod-shaped (bacillus) Gram-negative bacteria of the family Enterobacteriaceae. The two species of ''Salmonella'' are '' Salmonella enterica'' and '' Salmonella bongori''. ''S. enterica'' is the type species and is ...

'' infection inhibits the formation of this blockage. However, fleas simultaneously infected by the plague and ''Salmonella'' died within 2-3 days due to bloody diarrhea.Eskey, C.R., Prince, F.M. and Fuller, F.B.. 1949. Transmission of ''Salmonella enteritidis'' by the rat fleas ''Xenopsylla cheopis'' and ''Nosopsyllus fasciatus''. Public Health Reports. 64(30): pp.933-941.

Effect on Host

Parasites are known to reduce the fitness of their host.Devevey, G. and Christe, P.. 2009. Flea infestation reduces the life span of the common vole. Parasitology. 136(11): pp.1351-1355. Therefore, parasitism by fleas can affect the population of the hosts. Studies in gerbil hosts have found that flea infestation reduced ''Gerbillus dasyurus'' body mass and immune defences. In common vole hosts, it has also been found that flea infestation reduces body mass and immune defences and also induces an iron deficiency. These effects on the host negatively impact survivability and population density.

Disease Vectors

Like other fleas, this species plays a role in spreading zoonotic diseases.Herrero-Cófreces, S., Flechoso, M.F., Rodríguez-Pastor, R., Luque-Larena, J.J. and Mougeot, F.. 2021. Patterns of flea infestation in rodents and insectivores from intensified agro-ecosystems, Northwest Spain. Parasites & Vectors. 14(1): pp.1-13. Rise in rodent outbreaks of zoonotic diseases can spread to humans, like the plague,

rickettsioses A rickettsiosis is a disease caused by intracellular bacteria. Cause Rickettsioses can be divided into a spotted fever group (SPG) and typhus group (TG). In the past, rickettsioses were considered to be caused by species of Rickettsia. However, ...

, and bartonelloses. They can also transmit pathogens that cause

tularemia Tularemia, also known as rabbit fever, is an infectious disease caused by the bacterium ''Francisella tularensis''. Symptoms may include fever, skin ulcers, and enlarged lymph nodes. Occasionally, a form that results in pneumonia or a throat infe ...

Q fever Q fever or query fever is a disease caused by infection with ''Coxiella burnetii'', a bacterium that affects humans and other animals. This organism is uncommon, but may be found in cattle, sheep, goats, and other domestic mammals, including ...

, trypanosomiasis, and

myxomatosis Myxomatosis is a disease caused by ''Myxoma virus'', a poxvirus in the genus '' Leporipoxvirus''. The natural hosts are tapeti (''Sylvilagus brasiliensis'') in South and Central America, and brush rabbits (''Sylvilagus bachmani'') in North ...

. The rat flea contributes to the reemergence and cycles of some diseases, as previously mentioned. Infestation is more prevalent during the summer months and drops through the winter months. The highest infestation rate occurs during the summer because of increased activity in the mammal hosts that help spread the fleas and their disease vectors.

Gallery

File:Nosopsyllus fasciatus.jpg, A female and male rat flea ''N. fasciatus'' File:NHMUK010177300 A rat flea - Nosopsyllus Nosopsyllus fasciatus (Bosc, 1800).jpg, Close-up of a female slide-mounted ''N. fasciatus''

References

{{Taxonbar, from=Q7059249 Ceratophyllidae Parasites of rodents Insects of Europe