**15. Myiasis-producing Diptera**

Myiasis is the invasion of tissue by fly larvae, which at least for a certain period, feed on the host's dead or living tissue, liquid body-substance or ingested food and such invasions can be benign in effect, but others may result in a variety of conditions, including death. When the invasion occurs in the intestinal tract, it is called intestinal myiasis, in stomach known as gastric myiasis, or there may be nasal myiasis and cutaneous myiasis, etc. Some species of flies that are not significant as adults are important as myiasis-producing larvae. Cutaneous myiasis is a skin invasion by larvae (maggots) of certain flies, and depending on the species of fly involved, there are three main types of skin infestation by fly larvae such as furuncular (pimple-like or boil-like) myiasis, wound myiasis and migratory myiasis [91].

*Typical Flies: Natural History, Lifestyle and Diversity of Diptera DOI: http://dx.doi.org/10.5772/intechopen.91391*

Many of the flies that cause furuncular myiasis are commonly known as bot flies including *Dermatobia hominis*, *Cordylobia anthropophaga* (Blanchard & Berenger-Feraud), *Wohlfahrtia vigil* (Walker) and *Cuterebra* species. Many of the flies do not lay eggs on humans. Instead, the flies lay their eggs on other insects (such as mosquitoes) or on objects (such as drying laundry) that may come into contact with people's skin. Characteristic signs of furuncular myiasis comprise irritation, an impression of movement and on occasion a sharp piercing aching. In the beginning, people have a minor red bump, which can look like a common insect bite or creation of a furuncle (pimple). Later on, bump expands, and a slight opening may be evident in the center, opening may drain a clear yellowish fluid and on occasion a small portion of larva end is evident. Open wounds (traumatic), typically in homeless people, alcoholics and others in poor social circumstances, may become infested with fly larvae. The tissues that line the mouth, nose or eyes (mucosa) may also become infested [92]. The most common flies are screwworm flies such as *Cochliomyia hominivorax* and *Chrysomya bezziana* and *Wohlfahrtia magnifica* (Schiner) (**Figure 23**).

The most common sources of migratory (creeping) myiasis are flies that typically infest horses and cattle (Gasterophilus and Hypoderma flies). People can become infested if they have contact with infected animals. Less often, the flies lay eggs directly on people. Larvae do not stay in one spot and they burrow under the skin, causing itchy lesions. Diagnosis of fly larvae can be made on the size of larvae, location and host from which it is recovered, and characteristics of the spiracle openings located on the posterior of the larvae [93].

Warble flies of cattle are perhaps one of the most significant myiasis-producing problems of the cattle industry. There are two important species of the cattle grub, *Hypoderma lineatum* De Villiers Southern cattle grub and *Hypoderma bovis* (Linnaeus) Northern cattle grub. In broad-spectrum, life sequence of species contains adult flies that deposit eggs on body of host by sticking to furs, within some days eggs hatch and larvae enter into skin. Afterward, larvae transfer through host tissue and gather at esophagus wall. These from here, move to dermal tissue of host back, persist on cattle back for quite a few months and after that time these drop out to land for pupation. There are a number of indirect and direct reasons of hurt and fiscal loss which may be ascribed to invasions by these larvae. Mortalities may take place for the period of larval movement and at what time these are assembled in an area of esophagus. Indirect injuries are described as condensed milk making, weight loss otherwise low weight increases and less price of hide or carcass owing to presence of larvae. Common warble of rodents and rabbits *Cuterebra* sp., although common in wild rodents, infestations with this larvae are also occasionally seen on

**Figure 23.** Wohlfahrtia magnifica*.*

other mammals, and spread the livestock diseases blue tongue and African

It is a fly from the family Hippoboscidae, brown and hairy in color and resembles a tick. This wingless fly is about 4–6 mm long and has a small head. They are blood-feeding parasites of sheep. The sheep ked feeds on the blood of host by inserting its sharp mouthparts into capillaries beneath the skin. The adult

hippoboscids are well adapted to an existence on wool, hair and feathers for blood feeding. The life span of this fly is about 4 months with adult females retaining larvae internally until pupation and may produce 10–20 larvae by producing a single larva at a time. Pupae are attached directly to the wool, pupal stage lasts for 19–23 days and adult lives for 7–10 days. The entire life cycle of this fly takes place while it is on the infested animal. Other hippoboscid flies are important vectors for some avian diseases such as *Haemoproteus* sp. The sheep ked *Melophagus ovinus* (**Figure 22**), once remained a serious pest in the sheep industry. Several similar genera are present on wildlife including deer and elk. Adults ked can be killed using treatment dips and sprays most commonly containing ivermectin or pyrethrin. Use of injectable antihelminthics is also effective against some arthropods that have

Myiasis is the invasion of tissue by fly larvae, which at least for a certain period, feed on the host's dead or living tissue, liquid body-substance or ingested food and such invasions can be benign in effect, but others may result in a variety of conditions, including death. When the invasion occurs in the intestinal tract, it is called intestinal myiasis, in stomach known as gastric myiasis, or there may be nasal myiasis and cutaneous myiasis, etc. Some species of flies that are not significant as adults are important as myiasis-producing larvae. Cutaneous myiasis is a skin invasion by larvae (maggots) of certain flies, and depending on the species of fly involved, there are three main types of skin infestation by fly larvae such as furuncular (pimple-like or

boil-like) myiasis, wound myiasis and migratory myiasis [91].

**14.9 Sheep Ked or sheep tick** *Melophagus ovinus* **Linnaeus**

made this a less frequent problem [90].

**15. Myiasis-producing Diptera**

**36**

horse sickness [89].

*Life Cycle and Development of Diptera*

**Figure 22.** Melophagus ovinus*.* dogs and cats. One species (*Cuterebra emasculator*) Fitch parasitizes the external reproductive organs of rodents and may have an effect on population numbers [94]. **15.1 Cutaneous myiasis**

victims [98].

**Figure 26.**

**39**

Cochliomyia hominivorax*. (a) Adult, (b) Larva.*

Genus *Cochliomyia* in the family Calliphoridae includes blow fly *Cochliomyia hominivorax* (Coquerel) well-known as primary screwworm (**Figure 26**) for the reason that this larva creates myiasis and forages on live tissue producing pocket-like deep lesions in skin that might be enough harmful to host animals. But, *Cochliomyia macellaria* (Fabricius) is famous as secondary screwworm since its larva creates myiasis, however nourish on only necrotic tissue. Forensically, that species is significant since it is habitually linked o dead bodies and carcasses. All species in the family Calliphoridae have bristles on their merones, plumose arista and welldeveloped calypters. Both *C. macellaria* and *C. hominivorax* are metallic green to bluish green in major coloration and three black longitudinal stripes (vittae) on the notum of the thorax. The species *C. macellaria* has pale setulae on the fronto-orbital plate outside the row of frontal bristles, while *C. hominivorax* has dark setulae. The larvae of both *C. macellaria* and *C. hominivorax* have cylindrical bodies tapering anteriorly with 10 or more robust spines around the spiracular area and bands of small spines on each segment. The *C. hominivorax* larvae have distinctly pigmented tracheal trunks, while *C. macellaria* larvae do not have pigmented tracheal trunks,

The gravid female screw worm fly is captivated on living animals to oviposition sites. These sites are any discharges, bites, wounds, etc., which may take place. For egg deposition, the naval of newborn animals is a common site. The eggs are of cream color, hatch in 24 hours and larvae enter the wound and begin feeding. The larvae burrow into tissue, enlarging the wound that cause severe pain to the host. Animals smaller than rabbits, usually do not survive due to infestations. Larger animals may surrender to repeated infestation or if larvae penetrate blood vessels. Death is usually caused by toxemia and or septicemia from bacterial invasion of the wound. After 5–7 days, the larvae drop, burrow into the first layer of topsoil and begin their pupation. This stage can last from 7 days at a warm temperature to as long as 2 months if the weather is much colder. After emerging from the pupa adult flies live around 2–3 weeks. Once the infestation commences, a dark brown or reddish-brown discharge begins leaking from the wound, sometimes accompanied by an unpleasant smell as the flesh begins to decay both in livestock and human

These are various important species of parasites and necrotic tissue feeders since they are common and capable to parasitize abrasions and wounds on animals. Blow fly strike is multiparty, such as on sheep and some other animals. Altogether, these

but bear spines in a V shape on the anal protuberance [97].

*Typical Flies: Natural History, Lifestyle and Diversity of Diptera*

*DOI: http://dx.doi.org/10.5772/intechopen.91391*

Sheep bots or head grub *Oestrus ovis* L., (**Figure 24**) of family Oestridae, is a bot which commonly enters the sinuses nasal and passages of sheep. Adults of fly place live larvae over nasal passages; from here these make their approach to frontal sinuses and attach themselves with mucus membranes. These persist for some months in this location and are sneezed out or ultimately fall out and pupate in soil. The pupae period lasts for around 3–6 weeks. When host is infested; generally there is a pus-filled ejection from the nostrils, resulting shaking of head vigorously, less appetite and grating of teeth by animal. Maximum of cases do not produce distinct clinical symbols even though expiry of animal may take place within a week after intensified signs. The indirect damages and serious situations causing from invasion are possibly the best reasons for starting treatment [95].

Horse stomach bot *Gasterophilus* sp., in the family Oestridae are several species of this parasite each of which has slightly different locations of attachment, primarily affecting horses and donkeys. The more common horse bot fly *Gasterophilus intestinalis* (DeGeer) (**Figure 25**) is an internal parasite of gastrointestinal tract, while other are *Gasterophilus nasalis* (Linnaeus) nose bot fly and *Gasterophilus haemorrhoidalis* (Linnaeus) throat bot fly. In mid-summer, adult flies are frequent and females lay eggs on hairs habitually on the belly, forelegs, inside the knees and flanks. When the horse licks these body parts, rubbing and moisture cause eggs to hatch. Larvae transfer to mucus membrane of lips and tongue ultimately creating their way to stomach or other places. At this point, these continue to attach till subsequent spring, as soon as these separate, pass out through feces, fall to ground and pupate. Some indirect and direct pathological modifications are linked to invasion. Modest invasions by bots can contribute with no apparent symbols, but strong invasions may be shown through intestinal syndromes. Probable interfering with ingestion and immersion of nutrients, irritation of mucus membranes, and obstacle of pyloric sphincter are very common [96].

**Figure 24.** *Sheep bot fly. Immature and mature larvae.*

**Figure 25.** Gasterophilus intestinalis *larva.*
