Biting midges are a group of very small flies (Diptera) belonging to the family Ceratopogonidae. They are related to mosquitoes and many species feed blood of mammals and other vertebrates. The most important genus for livestock is Culicoides, with several dozens blood-sucking species. They are also called punkies and noseeums.
Culicoides midges are found worldwide, but each species has its own more or less restricted geographical distribution. They affect livestock, horses, humans and occasionally dogs as well. Several species can occur simultaneously in a particular region, each one with its own behavior, seasonal population development, preferred breeding substrate, etc.
Many Culicoides species are vectors of bluetongue virus, a disease particularly harmful for livestock.
Are animals infected with biting midges contagious for humans?
- No, but... Culicoides midges will bite many mammals, including humans, but they do not remain on their host for a long time and won't fly usually from an animal to a human person directly. See the life cycle below for more details.
You can find additional information in this site on the general biology of insects.
Adult Culicoides are rather small flying insects, not longer than 1-3 mm long, with two wings that are usually mottled. They have a brownish to grayish color. Both males and females feed on plant juices, but females of parasitic species need blood for egg production and have mouthparts adapted for piercing the skin and sucking blood. They have a blood meal every 3 to 5 days.
Culicoides midges undergo a complete metamorphosis (i.e. they are holometabolic). Females of most species lay 100 to 200 eggs (~0.5 mm long) in semi-humid environments close to water places or directly in the water. In contrast with black flies, they prefer stagnant waters (marshes, swamps) including small ponds, puddles, etc. Larvae hatch a few days after oviposition and live mostly under water or in the soil or mud in close to water, also in dung piles. After several molts larvae develop to pupae that congregate in the mud or soil close to the border of the water ponds. Development takes 2 weeks to more than 5 months depending on weather conditions. Adult midges live about 3 to 13 weeks, depending on climate and food availability.
Adult females are active mainly in the evening and at night, particularly by warm and windless conditions. They build swarms, however not as numerous as those of black flies. They find their preys by odor or shape. In contrast with black flies, biting midges are poor flyers and won't fly long distances. But several species will fly into stables, barns, etc., in search of a suitable host.
Biting midges are mainly a summer pest in regions with a cold winter. In tropical and subtropical regions they are found year-round, but are more abundant during the moist season. Unusual flooding after heavy rains combined with mild or warm temperatures can cause mass outbreaks in affected regions.
Harm to livestock, horses, dogs and cats, and economic loss due to biting midges
Culicoides bites are quite painful. Each blood meal lasts 4 to 8 minutes but each midge will bite repeatedly. Preferential biting sites are species-specific, but cattle are often bitten on belly, back and legs, horses on belly, mane, and tail. The saliva of midges contains toxins that make the bite particularly painful. The bite can also cause strong allergic reactions, particularly in horses. The animals scratch and bite themselves vigorously, which result in skin injuries, hair loss, skin thickening, etc. This condition is called sweet itch, Queensland itch (in Australia), Kasen (in Japan), and also summer dermatitis because it happens mostly in summer.
Culicoides midges are not as directly harmful to livestock as black flies, but annoyed animals will not grazed or feed properly which results in production losses. The mayor threat is disease transmission. Culicoides midges are vectors of several viruses and helminths. Two viruses are particularly harmful: the bluetongue virus that can cause high mortality in sheep, and the Akabane (or Schmallenberg) virus that causes malformations of the fetus, especially in calves.
Prevention and control of biting midges
Best prevention is eliminating as much as possible the breeding grounds of the midges, i.e. puddles, ponds, etc. However, this is not always possible around larger swamps or marshes. Chemicals to kill the larvae (larvicides) in the water are seldom acceptable because they will also kill numerous beneficial invertebrates, but may be appropriated for treating temporary puddles or ponds.
Housed livestock can be protected from biting midges to some extent using appropriate screens and/or nets in windows and doors. Biting midges do not like wind and are poor flyers: electric fans in the stables can reduce their activity indoors. Spraying the resting surfaces of the midges inside the stables using insecticides can also be indicated in endemic regions.
There are currently not many insecticides approved for on-animal use that effectively protect livestock or pets against biting midges. Ready-to-use pour-ons (mainly with synthetic pyrethroids) may help protecting cattle against midges for several days, insecticide-impregnated ear-tags for several weeks. But many products are not approved for use against biting midges. This means that the manufacturer has not sufficiently investigated their efficacy for whatever reason (often because the market is too small, or because the required dose of the active ingredient would be too high, etc). The same applies to spot-ons (=pipettes) and insecticide-impregnated collars for dogs or cats.
There are no really effective repellents to keep biting midges away from livestock or pets more than a few hours, if ever.
There are no vaccines for protecting livestock, dogs, cats or humans against biting midges.
Click here if you are interested in medicinal plants for controlling flies and other external parasites of livestock and pets.
Resistance of biting midges to insecticides
There are no reports on confirmed resistance of biting midges to insecticides.
This means that if an insecticide fails to achieve the expected efficacy against biting midges it is most likely that either the product was unsuited for the control of these insects, or it was used incorrectly.
Ask your veterinary doctor! If available, follow more specific national or regional recommendations for Culicoides control