Chorioptes bovis

Mites are small crawling animals related to ticks and spiders. Most mites are free-living and harmless. Other mites are parasitic, and those that infest livestock animals cause many diseases that are widespread, reduce production and profit for farmers, and are expensive to control.Psoroptes cuniculi surface feeding mite.Chorioptes bovis surface-feeding mite.Otodectes surface feeding mite causing ear canker.Ornithonyssus bird mite.Megninia feather mite of birds (oval object = egg).Cheyletiella parasitivorax house dust mite.Myobia musculi rodent fur mite.Glycyphagus grain mite, cause of allergy. Mites are small crawling animals related to ticks and spiders. Most mites are free-living and harmless. Other mites are parasitic, and those that infest livestock animals cause many diseases that are widespread, reduce production and profit for farmers, and are expensive to control. The invertebrate mites are arthropods with a chitinous exoskeleton and jointed limbs. Within the Arthropoda, they belong in the subclass Acari (or Acarina) and species belonging to the Acari are informally known as acarines. Although both acarines and insects (class Insecta) are studied in the fields of veterinary and medical parasitology, acarines are separated from insects by structure, feeding, lifecycles, and disease relations. Both livestock and companion animals are susceptible to mite infestation. Humans also may become infested by contagion from these domestic animals (a zoonosis). The term livestock is used in this article for all those domesticated mammals and birds that people rear for production of food, hides, wool, and draught power. Infestation by mites usually causes skin diseases known as mange, scabies, scab, demodecosis, or in general as acariasis. The causation, economic impact, and control of these diseases in livestock are described in this article. Mites that cause disease in honey bees are described in Varroa destructor. Over 48,000 species of mites are described, and an estimated half million more are yet to be discovered. Acarines parasitic on livestock animals are classified to family level in the list below. The taxonomy of the Acari is complex, several versions exist, and their phylogeny is considered to be paraphyletic (originating from several ancestral lines). This preceding modern textbook considers the Acari to be a subclass of the class Arachnida. Within the Acari are two superorders: the Acariformes and the Parasitiformes. The list below (Outline classification) is simplified for this veterinary article by omitting the superorders, orders, and suborders; this emphasizes the pragmatic taxonomic level of families, together with vernacular names. Within this list, the Parasitiformes include the blood-sucking mites of birds, the hard ticks, and the soft ticks, whilst the Acariformes include the psoroptic and sarcoptic mites, the trombiculids, and the demodectic mites. The identification of many types of mites is work for a specialist. However, the mites parasitic on vertebrate animals can readily be identified to at least the level of genus by nonspecialists if the clinical context of host species and site of infestation on skin or other organs is used. Also, the two main families of ticks are added to the list of acarine families because these common parasites are closely related to mites, and as larvae may confused with them at infestations. The third tick family, the Nuttalliellidae, consists of one rare species. Ticks require separate accounts because they have distinctly different feeding mechanisms and relations to disease. Distinguishing acarines from insects (subphylum Hexapoda) is similarly important because the term 'insect' is often used in popular text and speech for various small crawling animals. The generalized anatomy of an acarine as shown in the diagram below can be compared with that of an insect as in typical parasitic flies of domestic animals. Mites have a lifecycle in which larvae hatch from the eggs, then feed and molt into nymphs. Several stages of nymphs may follow (another term for stages in this context is instar). The final molt produces an adult female or male. The early form of the female is described as pubescent (ready for mating) and may be equipped with protuberances that couple with matching sockets on the male during fertilization. Such coupled mites are a natural occurrence in skin-scrape samples of mites for diagnosis. Once mated, the female continues to develop and lay eggs; in the typical case of Psoroptes, females produce one large egg at a time. In most parasitic mites, the entire lifecycle takes place on the host, with all stages present simultaneously (an exception is the trombiculid mites where the nymphs and adults are free-living). This type of lifecycle, with all active stages resembling each other in structure and feeding mechanism, is called incomplete metamorphosis (or hemimetabolism). A metamorphosis is a distinct change of body shape. When the larval stages of an invertebrate animal are completely different from the adult stage, as with caterpillars changing into butterflies, a complete metamorphosis occurs (holometabolism). The parasitic mites are either just visible to the naked eye or one needs a microscope to see them clearly. The distinct body segmentation characteristic of most arthropods is greatly reduced in the Acari. At the left of the diagram is an anterior section bearing the mouthparts (gnathosoma or capitulum), and at right, a posterior section comprising the main body (idiosoma). Mouthparts are characterized by a central pair of chelicerae, a ventral hypostome, and a lateral pair of palps. Chelicerae are protrusible, cutting or piercing structures essential to feeding. Palps are of sensory function during feeding and do not penetrate the host's skin. Acarines have no antennae and, except for some genera of ticks, are without eyes. A tube for ingesting food and secreting saliva is formed by apposition of both the chelicerae and the hypostome. The main body bears three pairs of legs in the larvae and four pairs in the nymphs and adults. The legs are multiple-jointed and operate by contraction of their internal muscles. The distal segment of the legs, the tarsus, is equipped with a terminal claw or pair of claws and sometimes with an adhesive pad or sucker that enables the mite to crawl up smooth surfaces. The internal organs (or viscera) include a tubular gut with a posterior anus, paired excretory tubes (Malpighian tubules) that empty out into the anus, paired respiratory tubes (tracheae) that carry atmospheric air directly up against the viscera, paired salivary glands with ducts to the mouthparts, female or male reproductive organs (ovary or testes), and a central nervous ganglion that acts as a simple brain. The diagram Mite infestation sites on skin shows where typical infestations of different taxonomic groups mites on livestock animals occur on or in the host's skin. The position of these mites in relation to the skin or other organs is crucial for their feeding and also for their veterinary diagnosis and options for treatment. The mites either feed on the tissues of the skin using penetrating mouthparts or on the inflammatory exudate that results from the action of the mouthparts and saliva of the mites on the skin. Demodectic mites have mouthparts adapted to penetrate and suck out the contents of individual cells of hair follicles. It is usual for all active stages of the mite lifecycle to feed as parasites, but the trombiculid mites are an exception. Most of the parasitic mites do not feed directly on blood, but the dermanyssid mites and larval trombiculid mites directly suck up capillary blood as their exclusive food. The tube through which food is ingested and saliva excreted during feeding is formed in most mites by apposing the sheath that contains the chelicerae against the hypostome. However, the trombiculids are an exception. Some species of mites (Analgidae) have adapted to feeding on keratin and skin debris amongst the feathers of birds, and other species have adapted to feed directly on internal tissues such as air-sacs or lungs (Cytoditidae and Laminosioptidae). Psoroptic mites feed superficially at the stratum corneum; the photograph of a histological section of skin infested with Psoroptes ovis, and the photograph of the surface of a host's skin infested with P. ovis looking like white dots, show this type of feeding. Sarcoptic mites feed by burrowing within the living layers of the epidermis, mainly stratum spinosum. Demodectic mites feed in a position technically external to the skin, between the epidermis and the hair shaft in hair follicles. Dermanyssid and trombiculid mites feed whilst external to the skin by piercing the skin with, respectively, their chelicerae or a stylostome feeding tube. Mites at other sites feed by using their chelicerae to scrape either at the skin surface, or at base of feather, or to penetrate and scrape at internal tissue such as air-sac or lung. Psoroptes ovis is an example of a surface-feeding mite. It commonly infests sheep, and cattle are infrequently infested. Other common psoroptic mites are in the genus Chorioptes. Species of Psoroptes and Chorioptes are very similar in appearance and infest the same species of livestock hosts. A diagnostic aid to differentiate these mites is the shape of the leg suckers. In Psoroptes, these are a small, shallow cup on a long stalk, whilst in Chorioptes, they are deeply cup-shaped with a short stalk. Psoroptic mites as adults are just large enough to see with the naked eye and can crawl readily using long legs. Chorioptes infestations are found on cattle and horses. Psoroptes cuniculi infests rabbits, mainly on their outer ears. This family includes the species Psorergates bovis which infests cattle and Psorergates ovis which infests sheep. They are similar in appearance to species in the Psoroptidae and infest the skin in a similar way, feeding superficially.