Mosquitoes are a group of dipteran insects (have one pair of wings) that belong to the family called Culicidae. There are over 3000 species all around the world, differently distributed according to each species.
Many mosquito species are blood-sucking parasites of wild and domestic mammals including cattle, sheep, goats, pigs, poultry, horses, dogs, cats, and humans.
Important genera are:
- Culex, vector of numerous virus and filariasis (parasitic worms)
- Aedes, vectors of Dengue and yellow fever
- Anopheles, vectors of malaria and filariasis
Biology and life cycle of mosquitoes
Adult females are blood-sucking parasites, not so the males that feed only on nectar and other plant juices and do not bite. Females feed on plant juices too, but need blood to be able to produce eggs. The lay eggs ob the water: individually, in array or in rafts. Often in calm waters close to the shore.
Several species lay eggs on very small water surfaces such as those that form on old tires, cans, buckets, drains, etc. after raining.
Most mosquito species are active at dawn and dusk or during the night and usually rest in the shadow during the daily heat, although a few species (e.g. the Asian tiger mosquito, Aedes albopictus) are active during the day.
Mosquitoes find their pray mostly through odor: they can detect various chemicals (e.f. carbon dioxide, octenol, etc.) produced by their victims.
Mosquito larvae are acuatic and feed on invertebrate plankton. Pupae concentrate on the water surface. The life cycle takes 2 to 5 weeks to complete, depending on temperature. The number of generations during a year depen on the length of the warm season.
In many tropical and subtropical regions mosquitoes are active the whole year through, whereas in cold regions they remain inactive during the colder months. Several species (e.g. Culex quinquefasciatus and Culex pipiens) develop very well in septic ponds such as those frequently found in livestock operations to evacuate manure.
Click here to learn more about the general biology of insects.
Damage, harm and economic impact of mosquitoes
Damage of mosquitoes to livestock, horses, and pets is usually not comparable to their medical importance for humans. They are not as damaging to livestock as other parasites such as ticks or biting flies. However they should not be underestimated. It has been reported that ruminants exposed to large swarms of mosquitoes can lose up to 300 ml blood in one day. Under such conditions anemia and even deaths can follow.
Mosquitoes transmit a number of livestock diseases (e.g. avian smallpox, classical swine fever = CSF = hog cholera, etc.) as well as heartworm (Dirofilaria immitis) of dogs and cats in regions with moderate to tropical climate.
Septic or drinking ponds in livestock operations allow the development of mosquitoes by the thousands, with the consequent nuisance for the operation and neighborhood.
Altogether, it is not usual that mosquitoes become an economic problem for livestock operations.
Prevention and control of mosquitoes on animals
Large area control of mosquitoes is always a complex task usually taken over by public authorities (governments, municipalities, etc.) and is not a topic in this site.
Farmers and producers can contribute to solve at least part of the problem with a few simple measures that reduce the suitability of water ponds in their properties for mosquito breeding: reducing the surrounding vegetation, building ponds with steep borders that reduce the areas with shallow waters, eliminating floating vegetable material, etc. Some larvicides are approved for treating such ponds in certain countries.
A number of species can complete development in small water amounts remaining in old tires, drains, garbage bins, cans, etc. Eliminating such bredding places will also reduce the mosquito population.
For confined poultry or pig operations it is highly recommended to install metal or plastic screens on doors, windows and other openings: they can substantially reduce the exposure of the animals to mosquitoes. Such screens can also be impregnated with classical insecticides (e.g. pyrethroids or organophosphates). Such insecticides can uselly be used for fumigation in case of massive outbreaks of mosquitoes as well.
On-animal chemical treatment of livestock or horses for mosquito control is usually not a good idea: protection will last only a few days and will have almost no effect on the mosquito population. If absolutely needed, pour-ons should be more effective than spraying or dipping. Insecticide-impregnated ear-tags do not usually protect against mosquitoes, or only marginally. Macrocyclic lactones such as ivermectin provide no control of mosquitoes, neither as injectables, nor as drenches, slow-release boluses or pour-ons.
To protect dogs and cats against mosquitoes best results are obtained with certain collars impregnated with pyrethroids. Spot-ons, shampoos, soaps, sprays and the like are mostly useless against mosquitoes: if ever, protection may only last for a few hours.
Mosquitoes can also breed in urban environments wherever small amounts of water remain for a few days: flowerpots of any size, some plants that can retain water (e.g. at the base of the leaves), ponds, fountains, drains, gutters, old tires, cans and tins, plastic bags, watering troughs, swimming pools, holes in truncs, etc., etc., etc. Eliminating these sites or keeping them dry will diminish the number of mosquitoes in your surrounding area.
Most research on chemical or natural repellents has been carried out precisely to protect against mosquitoes. There are effective repellents for humans and pets (e.g. DEET), but protection won't last longer than 4 to 8 hours. Such repellents are completely inadequate for whatever livestock operation, among other reasons for their high cost.
Click here if you are interested in medicinal plants for controlling mosquitoes and other external parasites of livestock and pets.
There are no true vaccines that will protect livestock or pets against mosquitoes.
There are Learn more about biological control of flies and other insects.
|If available, follow more specific national or regional recommendations or regulations for mosquito control on livestock.|
Insecticide resistance of mosquitoes
Several mosquito species have developed strong resistance to insecticides such as organochlorines, organophosphates, carbamates and pyrethroids, especially where large area control is practiced, or in agricultural regions where the abundant use of insecticides for crop protection can indirectly favor the development of resistance in mosquitoes as well. This resistance can substantially reduce the efficacy against mosquitoes of livestock or pet insecticides containing active ingredients of such chemical classes.
A practical consequence of this is that if a particular product of the mentioned chemical classes does not achieve the expected control, it is reasonable to consider a resistance problem, especially if that product has been used for several consecutive years. However, experience shows, that many cases of product failure are due to the use of inadequate products or to incorrect administration, and not to resistance.