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Warble fly is a name given to the genus ''Hypoderma'': large
Common cattle grub
on the UF / IFAS featured creatures website {{Taxonbar, from=Q9295520 Oestridae Parasitic flies Parasites of equines Parasitic arthropods of mammals Veterinary entomology Insects in culture Flies and humans
flies
Flies are insects of the order Diptera, the name being derived from the Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwings having evolved into advanced ...
which are parasitic
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 has c ...
on cattle
Cattle (''Bos taurus'') are large, domesticated, cloven-hooved, herbivores. They are a prominent modern member of the subfamily Bovinae and the most widespread species of the genus ''Bos''. Adult females are referred to as cows and adult mal ...
and deer
Deer or true deer are hoofed ruminant mammals forming the family Cervidae. The two main groups of deer are the Cervinae, including the muntjac, the elk (wapiti), the red deer, and the fallow deer; and the Capreolinae, including the reindeer ...
. Other names include "heel flies", "bomb flies" and "gadflies", while their larvae are often called "cattle grubs" or "wolves." Common species of warble fly include ''Hypoderma bovis'' (the ox warble fly) and ''Hypoderma lineatum'' (the cattle
Cattle (''Bos taurus'') are large, domesticated, cloven-hooved, herbivores. They are a prominent modern member of the subfamily Bovinae and the most widespread species of the genus ''Bos''. Adult females are referred to as cows and adult mal ...
warble fly) and ''Hypoderma tarandi
''Hypoderma tarandi'', also known as the reindeer warble fly and reindeer botfly, is a species of warble fly that is parasitic on reindeer.
The larvae of this fly are a skin-penetrating ectoparasite that usually infest populations of reindeer an ...
'' (the reindeer
Reindeer (in North American English, known as caribou if wild and ''reindeer'' if domesticated) are deer in the genus ''Rangifer''. For the last few decades, reindeer were assigned to one species, ''Rangifer tarandus'', with about 10 subspe ...
warble fly). Larvae of ''Hypoderma'' species also have been reported in horse
The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 million y ...
s, sheep
Sheep or domestic sheep (''Ovis aries'') are domesticated, ruminant mammals typically kept as livestock. Although the term ''sheep'' can apply to other species in the genus ''Ovis'', in everyday usage it almost always refers to domesticated s ...
, goat
The goat or domestic goat (''Capra hircus'') is a domesticated species of goat-antelope typically kept as livestock. It was domesticated from the wild goat (''C. aegagrus'') of Southwest Asia and Eastern Europe. The goat is a member of the a ...
s and human
Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, ...
s. They have also been found on smaller mammal
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 or ...
s such as dog
The dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a domesticated descendant of the wolf. Also called the domestic dog, it is derived from the extinct Pleistocene wolf, and the modern wolf is the dog's nearest living relative. Do ...
s, cat
The cat (''Felis catus'') is a domestic species of small carnivorous mammal. It is the only domesticated species in the family Felidae and is commonly referred to as the domestic cat or house cat to distinguish it from the wild members of ...
s, squirrel
Squirrels are members of the family Sciuridae, a family that includes small or medium-size rodents. The squirrel family includes tree squirrels, ground squirrels (including chipmunks and prairie dogs, among others), and flying squirrels. Squ ...
s, vole
Voles are small rodents that are relatives of lemmings and hamsters, but with a stouter body; a longer, hairy tail; a slightly rounder head; smaller eyes and ears; and differently formed molars (high-crowned with angular cusps instead of low-c ...
s and rabbit
Rabbits, also known as bunnies or bunny rabbits, are small mammals in the family Leporidae (which also contains the hares) of the order Lagomorpha (which also contains the pikas). ''Oryctolagus cuniculus'' includes the European rabbit speci ...
s.
Adult warble flies are large, hairy and bumblebee
A bumblebee (or bumble bee, bumble-bee, or humble-bee) is any of over 250 species in the genus ''Bombus'', part of Apidae, one of the bee families. This genus is the only extant group in the tribe Bombini, though a few extinct related gener ...
-like and brown, orange or yellow in color. The adults have vestigial mouthparts, so they cannot feed during their short lifespans, which can be as little as five days. Piper, R. (2007), ''Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals''. Greenwood Press
Greenwood Publishing Group, Inc. (GPG), also known as ABC-Clio/Greenwood (stylized ABC-CLIO/Greenwood), is an educational and academic publisher (middle school through university level) which is today part of ABC-Clio. Established in 1967 as Gr ...
.
They are found on all continents of the Northern Hemisphere, mainly between 25° and 60° latitude.
Infestations
The fly lays eggs on the forelegs of large animals. The eggs hatch within a week and penetrate the skin, where they migrate throughout the connective tissues (''H. bovis'') or to the esophagus (''H. lineatum''). After a few months, the larvae travel back to the skin surface and cause swellings called "warbles". They remain under the skin, and when destroyed by pressure, the larvae can cause largepurulent
Pus is an exudate, typically white-yellow, yellow, or yellow-brown, formed at the site of inflammation during bacterial or fungal infection. An accumulation of pus in an enclosed tissue space is known as an abscess, whereas a visible collecti ...
swellings, or anaphylaxis. Upon emergence, the fly leaves holes in the skin. Large numbers of such punctures can render cattle hides valueless.
The migrating larvae can cause damage to meat, as the tunnels they make in the muscle fill with a substance known as "butcher's jelly". Infestations also hinder weight gain and growth in the animals. Milk yields may also decline. Most infections in adult cows are minor, due to immunity developed over time.
Humans
In humans, the disease intracerebralmyiasis
Myiasis is the parasitic infestation of the body of a live animal by fly larvae (maggots) which grow inside the host while feeding on its tissue. Although flies are most commonly attracted to open wounds and urine- or feces-soaked fur, some spec ...
is a rare infestation of the brain by the larva of ''H. bovis''. It penetrates the brain by an unknown mode and causes symptoms such as convulsions and intracerebral hematoma
Intracerebral hemorrhage (ICH), also known as cerebral bleed, intraparenchymal bleed, and hemorrhagic stroke, or haemorrhagic stroke, is a sudden bleeding into the tissues of the brain, into its ventricles, or into both. It is one kind of bleed ...
. The first case of human warble fly infection in Britain (to a four-year-old boy on a farm near South Brent, Devon) was reported in the ''British Medical Journal'' in June 1924 by Dr Frederick William Style Other cases appear in medical literature. Myiasis of the human eye
Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and conv ...
can be caused by ''H. tarandi'', a parasite of reindeer
Reindeer (in North American English, known as caribou if wild and ''reindeer'' if domesticated) are deer in the genus ''Rangifer''. For the last few decades, reindeer were assigned to one species, ''Rangifer tarandus'', with about 10 subspe ...
. It is known to cause uveitis
Uveitis () is inflammation of the uvea, the pigmented layer of the eye between the inner retina and the outer fibrous layer composed of the sclera and cornea. The uvea consists of the middle layer of pigmented vascular structures of the eye and ...
, glaucoma
Glaucoma is a group of eye diseases that result in damage to the optic nerve (or retina) and cause vision loss. The most common type is open-angle (wide angle, chronic simple) glaucoma, in which the drainage angle for fluid within the eye rem ...
and retinal detachment
Retinal detachment is a disorder of the eye in which the retina peels away from its underlying layer of support tissue. Initial detachment may be localized, but without rapid treatment the entire retina may detach, leading to vision loss and blin ...
. ''H. lineatum'' and ''H. sinense'' may also infest humans.
Treatment and prevention
Warble flies have been eradicated in many countries, beginning withDenmark
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and Western Germany
The old states of Germany (german: die alten Länder) is a jargon referring to the ten of the sixteen states of the Federal Republic of Germany (FRG) that were part of West Germany and that unified with the eastern German Democratic Republic' ...
, in the 1960s. It was eradicated in the United Kingdom in 1990. It is a notifiable disease. It may have been eradicated from Belgium
Belgium, ; french: Belgique ; german: Belgien officially the Kingdom of Belgium, is a country in Northwestern Europe. The country is bordered by the Netherlands to the north, Germany to the east, Luxembourg to the southeast, France to th ...
.
From the 1980s, the preventive treatment is easier, by subcutaneous use of ivermectin
Ivermectin (, '' EYE-vər-MEK-tin'') is an antiparasitic drug. After its discovery in 1975, its first uses were in veterinary medicine to prevent and treat heartworm and acariasis. Approved for human use in 1987, today it is used to treat inf ...
, but the warble fly remains present in North Africa
North Africa, or Northern Africa is a region encompassing the northern portion of the African continent. There is no singularly accepted scope for the region, and it is sometimes defined as stretching from the Atlantic shores of Mauritania in ...
.
See also
*Botfly
Botflies, also known as warble flies, heel flies, and gadflies, are a family of flies known as the Oestridae. Their larvae are internal parasites of mammals, some species growing in the host's flesh and others within the gut. ''Dermatobia homin ...
* Horse-fly
Horse-flies or horseflies are true Fly, flies in the family Tabanidae in the insect Order (biology), order Diptera. They are often large and agile in flight, and only the female horseflies bite animals, including humans, to hematophagy, obtai ...
* Hypodermyasis
Hypodermyasis is a parasitic infection by the larvae of warble flies, most notably ''Hypoderma lineatum'' and ''Hypoderma bovis''. These flies mostly infect cattle in the warmer areas of the northern hemisphere. Humans become hosts when they inadv ...
References
External links
Common cattle grub
on the UF / IFAS featured creatures website {{Taxonbar, from=Q9295520 Oestridae Parasitic flies Parasites of equines Parasitic arthropods of mammals Veterinary entomology Insects in culture Flies and humans