Review of the Three Bot Fly Species

The study of insects has diversified with technological improvements. For instance, microscope invention has helped differentiate and distinguish the minute variations in the insects’ physical characteristics.

With regards to the purpose of the study, this research was conducted to analyze the current literature on the bot flies species and seek to understand if these species have some relations in terms of host identification and parasitism. A close study of these organisms will consequently enable the health, agricultural, and infrastructural industries to control their responses effectively.

The study was exhaustively relying on the retrospective methods, where a focus on the earlier identified information was used for comparison and contrast purposes. For instance, the insects are studied, and their economic importance is mentioned, so that the health industry could identify any cases of diseases and take directed measures of control and treatment through the public health and epidemiological departments. In terms of findings, a closer comparison was found to exist among these three mentioned species of bot flies, and the dissemination of these results to the general public would help to control their menace. The bot flies are mainly found on the insects that belong to the superfamily Oestroidae, and they have different hosts as it can be seen from the discussion below.

Introduction

In the study of insects, there is a particular character, which is mostly referred to as parasitism, and economic effects. When referring to an insect’s economic importance, it is necessary to focus on its both positive and negative impacts in large part.

Insects undergo growth and development just like the other organisms (Eric Locker, 2009). Since they all fall in the phylum Arthropoda, the division has some similar key features that classify them together. While grouping organisms, scientists based it on the similarities and variations to form a group with the most common characteristics. Thus, the grouping classifies the organisms into seven identified taxonomic groups.

When identifying insects, the species and genus are always used. It is connected with a fact that in these classification taxa, the narrowing is always done to ensure that each insect is identified with its smallest group which is believed to be able to interbreed and give birth to a viable offspring. Viability, in this case, refers to a young insect or other organism that can survive just like an average being and has no genetic variations that might dissociate it from its parents. However, due to the several genetic mechanisms such as crossing over and mutations, some variations are always observed, which in most cases are believed to be positive.

If to speak about the bot flies, they are identified as parasites, known to survive within the host’s intestinal organ in the form of larva, which is a developmental stage. It should be mentioned that the family group of these insects, the Oestridae, has some other subfamilies, which include Oestridae, Cuterebridae, Gasterophilidae, and Hypodermatidae (Mullen & Durden, 1993). The bot flies have an economic importance, which is the ability to cause Myiasis. Other species of these insects are also believed to cause this disease, and they include related insect families such as blow and screwworm flies. Nevertheless, the bot flies are the ones whose highest population of species lives as obligate parasites within the mammalian bodies. They deposit their eggs on the hosts directly or use a vector, which in most cases includes the houseflies, mosquitoes, and specifically for Dermatofobia hominis specific tick species. The second way is mostly connected with a fact that the most hosts are capable of noticing the presence of the bot fly, and they can escape from it. Therefore, these insects use intermediate vectors to ensure that their eggs reach their definitive hosts. The female bot fly even has a mechanism to make sure that the eggs are attached to the intermediate vector’s wings. When the eggs reach the host organisms, the animal warmth triggers the hatching of the larvae that then attaches to the host’s external skin and burrows underneath it to find their way to the body inside. In some instances, the bot flies also occur within the digestive tract of the horses, which may ingest the parasites through licking (Pape, 2001).

The family of these insects (Oestridae) has three species, which include Dermatofobia hominis, Oestrus ovis, and Hypoderma tarandi. They cause Myiasis for the host organisms. Myiasis refers to the infestation of human and animal organs and tissues by fly larvae that for some period, feed upon the living or dead tissues or the ingested food of the host. Thus, the feeding process enables these larvae to grow and develop into the next stage of its life cycle.

Comparison of the species

Similarities

The bot fly species have several similarities. As it can be seen from the table, they are all arthropods, and therefore, they all possess the division’s general characteristics. For instance, they have a segmented body, which includes head, thorax, and abdomen, spiracles through which the adults breathe, exoskeleton where the body muscles are attached, and open circulatory system. This system has a fluid, flowing through the hemocoel. It bathes the tissues directly, and through diffusion the exchange of material happens. The species also have a pair of antennae, which are mainly used for response purposes (Mullen & Durden, 1993).

Moreover, the bot fly species are large stout, and hairy bodied flies that mostly resemble the bumblebees. Their eggs are often deposited by the mosquito which plays an intermediate vector role or sometimes by the other insects that were mentioned above. All the species have a complete metamorphosis which includes adult — egg — larvae — pupa.

Means of locating hosts among the three species of botflies

A human parasite Dermatofobia hominis is very noticeable and easily evaded by the hosts before the insects are able to attach their eggs. Therefore, this parasite has developed a mechanism through which the female flies trap the other blood feeding parasites such as mosquitoes. In their turn, these organisms easily reach humans to act as the intermediate deliverer of the eggs, which after attachment hatch to larvae and infect the human subcutaneous layer.

On the contrary to this species, Oestrus ovis directly locates and deposits the larvae into nostrils of the sheep or the other livestock for the parasitic stage and completion of the lifecycle. Similarly, the Hypoderma tarandi and Oestrus ovis female flies locates the hosts, which for H.tarandi is the reindeer. A difference between them is that in H. tarandi species the eggs are usually attached to the forelegs of the host. After hatching, larva of both these species finds its way to the subcutenous tissues through burrowing and later moves to the other host’s organs.

Dermatofobia hominis

Dermatofobia hominis is a human bot fly that is referred to differently in different states of the world. For example, it is known as torsalo in Central America and berne in Brasil. This fly, which is also identified as the tropical warble fly, is found in both the tropical and semi-tropical areas of the New World. Its localities are often coffee growing areas, which are mainly highlands since the bot fly species is always attracted to hilly, moist, and cool territories. D. hominis can also live in the agricultural and scrub forest areas together with the rainforests. The insect’s native origin is believed to be from the Central and South America.

Dermatofobia hominis is a vector known insect, whose larvae is a menace to the humans since they infest the mammal skin and lodge within its subcutaneous layer. The larvae cause a terrible pain for the host due to the pustules, which appear at the infection area, and secrete fluids. The spread of this condition is connected with the places shifting or rather travel of the infected humans from the infestation area to the new cities and nations. In such a way, the parasite becomes transmitted to the other territories, thus attacking new populations and causing rise in its incidences.

Morphology

Dermatofobia hominis

Adults. The adult bot fly (Dermatofobia hominis) measures about 12-18 mm long, and it is an insect with a wide array of colors. It has a yellow face with a metallic blue abdomen and orange legs. The insect’s body is all covered with hairs, and this characteristic gives Dermatofobia hominis a bumblebee appearance. The representatives of this family have three ocelli and a pair of large compound eyes (Masoodi & Hosseini, 2004). They are sexually dimorphic as in males the eyes are located closer than in females. In their turn, the female flies are usually larger in size, compared to their male counterparts, and they bear a pseud ovipositor at their posterior ends. The antennae of this fly bear an Arista tenuous, plumose projection on the second of its three segments. In addition, Dermatofobia hominis have functionally reduced knob-like halters that are a common characteristic, shared by all the dipterans. Due to the evolution and natural selection in the biological makeup, the ancestral mouthparts of this insect have been lost. Dermatofobia hominis are also heterothermic and bilaterally symmetrical.

Larvae. Their larvae are distinguished from the other species by the pyriform shape, transverse rows of spines on their tegument sclerotized mouthparts, and a pair of projecting spiracles at the posterior end. The larvae may have longer lengths of about 25 mm long and 7 mm wide. The white maggots undergo three instar stages with different physical orientations. The first one is always worm-like, and it has a bulbous end. The second instar has a bottle neck shape, and lastly the third instar has a cylindrical shape. Each instar has a backward projecting spine, which surrounds the thorax.

Eggs. The eggs are creamy colored and oval in shape. They are usually attached to different species of blood-feeding parasites. To attach the eggs, the female bot flies are obliged to capture the right vector. The eggs are usually attached to the ventral side of the intermediate vector’s body. When the vector gets to blood feeding from a warm mammal, the warmth triggers the hatching of the eggs into larvae, which then lodges in the subcutaneous layer of human skin.

Pupa. The pupal stage is thought to display the prominent anterior spiracles of the third instar larval stage.

Oestrus ovis

Oestrus ovis is thought to be a bee insect about 10-12 millimeters long, slightly hairy with a branded, dark gray body, and flat yellow head and legs. It is a widely distributed species, found across the world, where there are the populations of sheep, deer, and goats. Its origin is directed back to the North America, Central America, and the areas around the Mediterranean Sea, Middle East, and Brazil. On the African continent, there is an elevated occurrence of these insects in the southern region (Masoodi & Hosseini, 2004).

Hypoderma tarandi

Adults measure about 8-10 mm in length. They are large hairy and bee-like. They possess brown, yellow, and orange colors. The adults have vestigial mouthparts, and thus they do not feed during their short lifespans, which are estimated to be about five days. Larvae measures between 5 and 15 millimeters long, and they can be white, creamy, or light brown in color.

Lifecycles of the three species

Dermatofobia hominis

This species reaches its sexual maturity soon after the puparium emergence. They expose viable eggs which may be laid as early as the second day of adulthood. The eggs require at least 5-9 days in order to reach the vertebrate host after its attachment to the paratenic one (Eric Locker, 2009). Subsequently, the egg requires another 21-28 days during which it has to undergo all the three instar stages inside its definitive host. Upon completion of the instar development, the larvae, the third stage which occurs after the thirtieth day, crawl out of the pupa into the soil. At that time, they feed on tissue exudates from the animal host. Later, the population occurs on the ground, and the pupae do not feed. The adult bot flies will eventually appear after two or three weeks. They emerge from the pupal cases, and their extremely sensitive antennae make the males and females find each other quickly.

Oestrus ovis

This species is majorly connected with the sheep infestation. Its life cycle begins with the eggs within the females, which are fertilized, and hatch to larvae of about one millimeter. While on the wing, the female throw some larvae in the form of tiny mucous drop straight into a nostril of the host animal. The larvae then make their way up to the nasal passage and nasal sinus. During their stay in the sinus, the larvae grow and molt into a second larval stage or instar (Eric Locker, 2009). They continue to develop into an insect of about 20 millimeters in length with a dark stripe across each segment.

When the larvae are completely developed, they move with the nostrils drops down to the ground, bury themselves, and pupate. The larval development depends on the ambient temperatures. This translates to about 25-35 days in warm weather, but takes up to ten months in cold climates. The pupa takes about three to nine weeks to mature, which also depends on the temperatures. The adult larvae then burrow up to the surface and commence mating. The adult does not feed during two or four weeks of its adult life as it is believed to survive only by taking water.

Hypoderma tarandi

This fly lays eggs on the forelegs of large animals. The eggs hatch within a week and penetrate into the animal skin to access the connective tissues. They then migrate throughout the connective tissues of the host’s esophagus. The larvae, which develop there, later travel back to the skin surface. They cause swellings, which are usually referred to as “warbles” there. The larvae remain on the skin, and when they are destroyed by the pressure, they cause large purulent swellings or anaphylaxis (Legace-Wiens, 2008). Upon emergence of fully developed flies, they usually leave holes on the animal skin surface, thus rendering the hides valueless.

Comparison of symptoms and treatment and control

Dermatofobia hominis

The infection of Dermatofobia hominis causes hard and painful lesions in the skin. The patients can feel the larval movements while taking a shower and when the lesion or wound is covered. The body of the host responds to the reaction by elevating the number of white blood cells and macrophages, which are directed towards fighting the trauma. The condition can be treated through several identified methods. The most recent one is the surgical removal of the larvae under local anesthesia (Mullen & Durden, 1993). With regards to the management, the vectors can be controlled through various methods. The most appropriate and encouraged one is the application of the vector repellants and use of protecting clothing to ensure that the vectors do not reach the hosts (Eric Locker, 2009).

Oestrus ovis

Oestrus ovis is a common kind of a fly that is originated in the genus Oestrus. The parasite is an identified predator of the sheep, deer goats, and sometimes cattle. In the modern world, a new study has also identified the occurrence of this parasite in the horses and dogs. Also, human infestation has been discovered. Thus, Oestrus ovis have been identified as significant pests in the agricultural industry.

The most appropriate method, used in the control of these conditions, is the use of medications, which are most disseminated through the drenching methods. Quarantine approaches are also very important to ensure re-infections from one flock do not occur in another one. Also, in cases where there are large infection rates, the farmers can exercise mass slaughter and burn the cattle to ensure that the parasites are killed with the animals since they cannot withstand the high temperature, used to exhume the carcasses.

Hypoderma tarandi

Hypoderma tarandi is a parasite just as the other two studied insects. It can also be referred to as a reindeer warble fly. The origin of its name is explained by its definitive host, which are the reindeer and caribou of the Arctic areas.

The infestation of these parasites causes several precarious effects on the hides, meat, and milk of the host animals. The parasitic stage of this organism is the larva, which penetrates into the skin as an ectoparasite in domestic flocks and herds. Since the larvae keep migrating through the animal skin and tissues, they are believed to cause damage to the meat as they leave tunnels within the muscles behind themselves. Moreover, the parasitic infestation also hinders animals from gaining weight, growing and developing. Thus, for instance, milk yield in the herds faces a great challenge as the cattle usually drop due to the parasitic infections (Legace-Wiens, 2008).

The physical orientation of the warble flies is similar to the other bot flies, and therefore, a major variation comes in the genetics and the host organisms. It has similar life circle stages through which a complete metamorphosis is employed to reach the final stage of development.

Economic importance

D.hominis

The spread of this parasitic infection has taken over a wide area all over the globe. Its eradication has been a target for many nations, and they have not failed to clear out the infections of this fly starting from Denmark and western Germany, which were heavily infested by it. The most appropriate method to kill the present larva is the use of ivermectin through the subcutaneous application (Legace-Wiens, 2008).

Oestrus ovis

The principal hosts of these parasites, the sheep, face a much more negative impact. The affected animals are notably known to identify and sense the parasites presence, and it prompts them to run away. Moreover, sheep are always putting their noses down to avoid access to the parasites. Thus, sometimes they tend to move in circles closer together with their heads down (Gregory, 2004). Furthermore, the hosts are always alerted to the deposition of the parasitic larvae or eggs, and as a result, the sheep and the other host animals respond by tapping their muzzles on the ground as a way of trying to remove the eggs.

Nevertheless, the larvae’s effort is always to ensure that they have established themselves within the host’s nostril sinuses, and after it, they cause an annoying irritation for the animal. The minimum infestation population is about fifteen but in most cases, a population of about eighty is also identified in the nostril. The irritation caused by the parasite is directly proportional to the number of present pests. Apart from the annoyance and irritation, the parasitic infestation has also been associated with such symptoms as mucous discharge, possible impairment of breathing and majorly disturbance of the sheep which discourages feeding and leads to the weight loss. As a result, the animals develop malnutrition conditions which may result in their death. It should be mentioned that parasitic infestation in the host’s mucous membranes is also known as Myiasis.

H.tarandi

The presence of its larvae is a pathological condition, causing skin damage and consequently reducing the hosts’ market. The pathological condition is referred to as Myiasis. It causes reduced milk production in cattle because of its gadding and grub movements in the host’s body.

Human infestation

D.hominis

D.hominis is a human based parasite. It identifies well the human skin location, mainly the subcutenous layer. The human infestation happens due to the ability of these insects to spot and use the respective intermediate parasites to ensure the accomplishment of the developmental stage.

Oestrus ovis.

Despite being a major threat to the livestock, this parasite has also been linked with the human beings. The most infected individuals are the shepherds. In most cases, they are more vulnerable to the attacks since these people have a closer contact with the definitive hosts, who are the sheep and the other livestock. Thus, they are responsible for the parasitic spread to the other areas and individuals as they carry the parasites, making it difficult to handle the insects (Gregory, 2004).

H.tarandi

The warble fly just as the other bot flies does not leave humans behind. It is associated with the diseases, called the intracerebral myiasis. Though the penetration of its larva into the brain is not explained, the most important effects are the reported symptoms of convulsions and intracerebral hematoma, which are fatal.

Conclusion

In summary, the species mentioned above are insects similar in identification, location, and parasitism. They utilize much the same methods for infecting and parasitizing their hosts to reach maturity. It leaves us to fail to reject null hypothesis since it is well proved that all three species lodges themselves within the hosts’ skin or outer surface, which might be subcutaneous or mucous membranes to cause Myiasis. Several similarities such as the life cycles of the parasites have also risen. On the contrary, variation in the morphological outlook of the parasites has been recognized throughout the study. Treatment and control mechanisms of each insect were very specific and different too. The study of these three species was just an eye-opener for the researchers, proving that the encouragement should be prompted to propel scientists to conduct more studies in this area so that the eradication of these parasites is completely achieved in both the animals and human beings.