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Culicoides variipennis

By Nathan Lenneman

Geographic Range

Culicoides variipennis is found throughout North America, wherever large mammal hosts (especially ruminants) are available. (Tabachnick, 1996)

Habitat

Culicoides variipennis is found mainly in moist areas and low wetlands, so livestock and animals attempting to avoid this parasite are best able to do so by staying in higher and dryer areas. (Anderson, 2000; Tabachnick, 1996)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams
  • temporary pools

Physical Description

Adult Culicoides variipennis are less than 1 mm in length, allowing them to be very pesky and difficult to keep from livestock. The genus can also be identified by its spotted, narrow wings. These wings also have few veins and fold over the abdomen while the fly is at rest. Only females feed on blood, so they have somewhat different mouthparts from males. (Roberts and Janovy, 2000)

  • Sexual Dimorphism
  • sexes alike
  • Range length
    less than 1 (high) mm
    in

Reproduction

Females of this species lay their eggs in wet environments, including aquatic, subaquatic, or moist soil conditions, where they hatch and develop into larvae. These aquatic or subaquatic larvae feed on dying organisms or other organic material. Depending on the environmental conditions, the life cycle may last a half year up through three years. (Roberts and Janovy, 2000)

Behavior

Culicoides variipennis tends to be a swarming insect; it usually attacks its host in swarms. The slight size of the insect makes it difficult for the host to rid itself of the pest, so the fly can attack the host in great numbers. (Roberts and Janovy, 2000)

Food Habits

This dipteran feeds on a variety of domestic ruminants, most notably sheep and cattle, along with some wild ruminants. Culicoides variipennis lands on its host, where it bites through the skin. The species is a telmophage, which means it bites through the skin and laps up the blood that pools out. Culicoides variipennis bites the host with its mandibles and feeds on the blood with its proboscis. (Tabachnick, 1996)

  • Animal Foods
  • blood
  • body fluids

Ecosystem Roles

These insects are food for a variety of small predators, mostly other insects and spiders. Females of this species feeds on a variety of ruminant mammals, most notably sheep and cattle, along with some wild ruminants. They are also a vector for the virus that causes "bluetongue," a disease in domestic livestock.

This species is also host to a parasitic nematode, Heleidomermis magnapapula. (Tabachnick, 1996)

Commensal/Parasitic Species
  • a nematode, Heleidomermis magnapapula

Economic Importance for Humans: Negative

Culicoides variipennis has a negative impact on the agricultural economy. The flies themselves aren't very harmful to livestock, but they are a vector to a more prominent problem: the virus that causes "bluetongue." Infection by the bluetongue virus can cause a variety of symptoms in ruminants, such as swelling of the tongue and face and erosions in the mouth and throat. The symptoms are less severe in cattle, but infection in sheep often leads to death. Also, infection in pregnant ruminants can lead to adverse effects--central nervous system damage and death--to developing fetuses if the infections occur early enough in the pregnancy. In addition, it is estimated that in the late 1990's, about $125 million was lost annually in the agricultural economy because of export restrictions intended to prevent bluetongue-infected livestock from being shipped to bluetongue-free countries.

The virus is easily transferrable from fly to host and vice versa via C. variipennis feeding on host blood. The virus can replicate in the fly's thorax, and can eventually be secreted in the fly's saliva within 7-10 days, when it can be transferred to another ruminant. (Anderson, 2000; Bowne and Jones, 1966; Kimberling, 1988; Tabachnick, 1996)

Conservation Status

This species is quite common and has no special conservation status.

Other Comments

There is a natural parasite that is being manipulated to combat C. variipennis, the nematode Heleidomermis magnapapula. Studies are currently being conducted to test the effectiveness of this hyperparasite (an organism that parasitizes another parasite). (Paine and Mullens, 1994)

Contributors

Renee Sherman Mulcrone (editor).

Nathan Lenneman (author), University of Michigan-Ann Arbor, Barry OConnor (editor), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

agricultural

living in landscapes dominated by human agriculture.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

causes or carries domestic animal disease

either directly causes, or indirectly transmits, a disease to a domestic animal

detritivore

an animal that mainly eats decomposed plants and/or animals

detritus

particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

freshwater

mainly lives in water that is not salty.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

internal fertilization

fertilization takes place within the female's body

marsh

marshes are wetland areas often dominated by grasses and reeds.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

parasite

an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

sanguivore

an animal that mainly eats blood

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

References

Anderson, N. 2000. Plain talk on sheep health. Suffolk News, July/August 2000.

Bowne, J., R. Jones. 1966. Observations on bluetongue virus in the salivary glands of an insect vector, Culicoides variipennis. Virology, 30: 127-133.

Kimberling, C. 1988. Diseases of sheep, 3rd ed.. Philadelphia: Lea and Febiger.

Paine, E., B. Mullens. 1994. Distribution, seasonal occurrence, and patterns of parasitism of Heleidomermis magnapapula (Nematoda: Mermithidae), a parasite of Culicoides variipennis (Diptera: Ceratopogonidae) in California. Environmental Entomology, 23: 154-160.

Roberts, L., J. Janovy. 2000. Foundations of Parasitology, 6th ed.. Boston: The McGraw-Hill Companies, Inc..

Tabachnick, W. 1996. Culicoides variipennis and bluetongue virus epidemiology in the United States. Annual Review of Entomology, 41: 23-43.

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