''Melophagus ovinus'', or the sheep ked, is a brown, hairy
fly that resembles a
tick
Ticks (order Ixodida) are parasitic arachnids that are part of the mite superorder Parasitiformes. Adult ticks are approximately 3 to 5 mm in length depending on age, sex, species, and "fullness". Ticks are external parasites, living by ...
. This wingless fly is about 4 to 6 mm long and has a small head; it is a
fly from the
family
Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...
Hippoboscidae
__NOTOC__
Hippoboscidae, the louse flies or keds, are obligate parasites of mammals and birds. In this family, the winged species can fly at least reasonably well, though others with vestigial or no wings are flightless and highly apomorphic. As ...
. They are blood-feeding
parasite
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 ...
s of
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 ...
.
The sheep ked feeds on the blood of its host by inserting its sharp mouthparts into capillaries beneath the skin.
The legs of the sheep ked are very strong and tipped with claws. Sheep keds live their whole lives in the wool of sheep. They are most commonly found on the neck, shoulders, and underbelly of the host animal.
Although they are often referred to as the “sheep tick”, sheep keds spend their entire lifecycle on their hosts, which is distinguishable from the characteristics of a true tick. Additionally, sheep keds have six legs, whereas true ticks have eight legs.
Distribution
Native to most of
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 subcontinent of Eurasia and it is located entirel ...
including
Iceland
Iceland ( is, Ísland; ) is a Nordic island country in the North Atlantic Ocean and in the Arctic Ocean. Iceland is the most sparsely populated country in Europe. Iceland's capital and largest city is Reykjavík, which (along with its s ...
, and the
Faroe Islands
The Faroe Islands ( ), or simply the Faroes ( fo, Føroyar ; da, Færøerne ), are a North Atlantic island group and an autonomous territory of the Kingdom of Denmark.
They are located north-northwest of Scotland, and about halfway bet ...
, as well as North West
Africa
Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...
,
Mongolia
Mongolia; Mongolian script: , , ; lit. "Mongol Nation" or "State of Mongolia" () is a landlocked country in East Asia, bordered by Russia to the north and China to the south. It covers an area of , with a population of just 3.3 million, ...
, and North
India
India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...
, it was introduced and established in
Kenya
)
, national_anthem = " Ee Mungu Nguvu Yetu"()
, image_map =
, map_caption =
, image_map2 =
, capital = Nairobi
, coordinates =
, largest_city = Nairobi
...
,
South Africa
South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. It is bounded to the south by of coastline that stretch along the Atlantic Ocean, South Atlantic and Indian Oceans; to the ...
,
Japan,
Australia,
New Zealand
New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...
, most of
North America, and many parts of
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 sout ...
, including
Tristan da Cunha
Tristan da Cunha (), colloquially Tristan, is a remote group of volcanic islands in the South Atlantic Ocean. It is the most remote inhabited archipelago in the world, lying approximately from Cape Town in South Africa, from Saint Helena a ...
and the
Falkland Islands
The Falkland Islands (; es, Islas Malvinas, link=no ) is an archipelago in the South Atlantic Ocean on the Patagonian Shelf. The principal islands are about east of South America's southern Patagonian coast and about from Cape Dubouze ...
.
Hosts
The primary host of ''M. ovinus'' is the domestic
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 ...
. Also, records on
argali
The argali (''Ovis ammon''), also known as the mountain sheep, is a wild sheep that roams the highlands of western East Asia, the Himalayas, Tibet, and the Altai Mountains.
Description
The name 'argali' is the Mongolian word for wild sheep. It ...
''(Ovis ammon)'',
bighorn sheep
The bighorn sheep (''Ovis canadensis'') is a species of sheep native to North America. It is named for its large horns. A pair of horns might weigh up to ; the sheep typically weigh up to . Recent genetic testing indicates three distinct subspec ...
''(Ovis canadensis)'', and
Dall sheep ''(Ovis dalli)'' are doubted.
Lifecycle
Sheep keds live for typically four to six months, and may produce from 10 to 20
larva
A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle.
...
e. The female fly produces a single
larva
A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle.
...
at a time, retaining the larva internally until it is ready to
pupa
A pupa ( la, pupa, "doll"; plural: ''pupae'') is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in thei ...
te. The larva feeds on the secretions of a "milk" gland in the
uterus
The uterus (from Latin ''uterus'', plural ''uteri'') or womb () is the organ in the reproductive system of most female mammals, including humans that accommodates the embryonic and fetal development of one or more embryos until birth. The ...
of the female. After three larval
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 ...
s, the white prepupa immediately forms a hard, dark
puparium. This is deposited on the wool of the sheep and is attached with a glue-like material. The larva immediately hardens and becomes a darker color. This pupal stage lasts for 19 to 23 days in the summer and 20 to 36 days in the winter. Pupal stages are not susceptible to insecticides. If removed from the host, the adult lives for 7–10 days.
Symbiotic enterobacterium ''Candidatus''
Sodalis melophagi was described to live in evolutionary early/intermediate state of symbiosis with sheep keds.
Immune response and effects
In lambs, the sheep ked may cause anemia and reduce weight gain.
It feeds on the blood of its host, so causes irritation to the sheep, leading it to rub, producing both loss and damage of the wool. It also makes firm, hard nodules that develops on the skin called a cockle, this will reduce the value of the hide. The ked feces also stains the sheep's wool reducing its value.
They also transmit ''
Trypanosoma melophagium
''Trypanosoma'' is a genus of kinetoplastids (class Trypanosomatidae), a monophyletic group of unicellular parasitic flagellate protozoa. Trypanosoma is part of the phylum Sarcomastigophora. The name is derived from the Greek ''trypano-'' (bore ...
'' nonpathogenic
protozoan parasite of sheep.
A sheep’s immune response to keds reduces capillary flow to the skin. Although this response is trying to combat the ked infestation, it also results in a less abundant and lower quality fleece.
Treatment
Adult keds can be killed using treatment dips and sprays most commonly containing ivermectin or pyrethrin. However, the pupal stage is resistant to treatment, so treatment must be repeated at 24- to 28-day intervals. Using insecticides with a 3- to 4-week residual activity would also eliminate emerging adult keds. Additionally, because both adult keds and pupae stages live in the wool of the sheep, shearing can dramatically reduce the ked population. It would be most beneficial to shear before insecticide treatment. Most modern treatments used to control sheep lice will also control sheep ked infestations.
Disease vector
The sheep ked is capable of transmitting
bluetongue virus
Bluetongue disease is a noncontagious, insect-borne, viral disease of ruminants, mainly sheep and less frequently cattle, yaks, goats, buffalo, deer, dromedaries, and antelope. It is caused by ''Bluetongue virus'' (''BTV''). The virus is ...
in sheep, though little evidence suggests they are bluetongue disease vectors in nature.
Sheep resistance to keds
Some sheep have been shown to be resistant to the harmful effects of sheep keds. Resistant sheep’s skin was histologically examined and showed arteriolar vasoconstriction in addition to fibrinoid degeneration of the tunica media in the lower dermis. This subepidermal region showed an increased infiltration of eosinophils and lymphocytes. The upper dermis of resistant sheep showed an increase of empty capillaries, whereas the upper dermis of susceptible sheep showed capillaries filled with red cells. The resistance of some sheep to keds was due to prolonged cutaneous arteriolar vasoconstriction. In resistant sheep, keds were unable to obtain enough blood and eventually died from starvation.
Subspecies
The
subspecies ''Melophagus ovinus himalayae'' Maa, 1969 is from
Nepal
Nepal (; ne, :ne:नेपाल, नेपाल ), formerly the Federal Democratic Republic of Nepal ( ne,
सङ्घीय लोकतान्त्रिक गणतन्त्र नेपाल ), is a landlocked country in S ...
and
Tibet
Tibet (; ''Böd''; ) is a region in East Asia, covering much of the Tibetan Plateau and spanning about . It is the traditional homeland of the Tibetan people. Also resident on the plateau are some other ethnic groups such as Monpa, Taman ...
. Its host is the
yak (''Bos grunniens''), and domestic
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 ma ...
.
See also
*
Ked itch
References
{{Taxonbar, from=Q2352863
Hippoboscidae
Parasitic flies
Parasitic arthropods of mammals
Flies described in 1758
Wingless Diptera
Diptera of North America
Diptera of Europe
Diptera of Asia
Taxa named by Carl Linnaeus