What Are Bot Flies? What You Should Know for Your Safety

Bot flies are a unique type of fly species known for their parasitic behavior.

These insects have a bee-like appearance, with their larvae being short, pudgy grubs that live as parasites within their animal hosts’ tissues.

The danger posed by bot flies depends on the interaction between the fly and its host.

Human botfly infections, which are caused by Dermatobia hominis, can be painful and may require medical attention.

Conversely, bot flies that parasitize animals, such as Gasterophilus intestinalis, Gasterophilus nasalis, and Gasterophilus haemorrhoidalis, may cause temporary discomfort to their hosts but do not typically pose a life-threatening danger.

Infestations by bot flies are known as myiasis, which is an infection caused by their larval stage.

Certain bot flies target humans, while others may cause myiasis in livestock or wildlife. In some cases, proper precautions and treatments can be taken to minimize potential risks.

What Are Bot Flies?

Bot flies are a type of insect belonging to the family Oestridae, with the most common species being Cuterebra fontinella.

Adult bot flies have several distinct features:

• Size: They are 15 to 17mm long (roughly 5/8 inch)
• Color: Black with pale yellow markings
• Wings: Smoky colored
• Eyes: Large and prominent

Bot flies are known for their parasitic larvae, which live in the tissues of animals.

Despite their menacing appearance, adult bot flies are generally harmless to humans and animals, as they don’t feed or take in nutrients.

However, their larvae can be a cause for concern.

Larvae of bot flies exhibit different behaviors and development stages compared to other obligatory myiasis-causing flies. These include:

• Highly host-specific
• Parasitic nature
• Limited host range

In terms of comparing different botfly species, some key characteristics include:

• Size of the adult fly
• Coloration and markings
• Geographical distribution
• Host specificity
• Larval development stages
• Level of parasitic behavior

Bot flies may appear to be dangerous due to their size and appearance. However, it is their larval stage that can cause problems for animals and humans.

Life Cycle and Hosts of Bot Flies

Larval Stage

Bot flies begin their life cycle as eggs, which are laid by adult females on a host animal’s fur or nearby vegetation.

For example, the horse bot fly, Gasterophilus intestinalis, can lay between 150 and 1000 eggs on a horse’s body.

Once the eggs hatch, the larvae penetrate the host’s skin, causing myiasis, which is a parasitic infestation.

Some botfly species, like Cuterebra fontinella, primarily target rabbits, while others, like Dermatobia hominis, can affect humans as well.

During this stage, the larvae feed on the host’s tissue and grow larger.

Some species, such as Cuterebra emasculator, are known to specialize in specific host animals, like rabbits or rodents.

Pupal Stage

The larval stage ends when the fully grown larvae leave their host to pupate.

This process involves the larvae burrowing into soil or other suitable material to form a protective casing called a puparium.

Inside the puparium, the bot fly larva undergoes metamorphosis, transitioning from a larval to an adult form.

The pupal stage can last for several weeks or even months, depending on the botfly species and environmental factors.

Adult Stage

Once metamorphosis is complete, botfly adults emerge from their puparium.

These bee-like flies have rudimentary or non-functioning mouthparts, as they do not feed or take in nutrients. Their main goal in the adult stage is to reproduce.

Adult bot flies, such as Cuterebra fontinella, are large, robust flies with a body length of 15 to 17mm. They are typically black with pale yellow markings and smoky wings.

Breeding is the primary focus for adult bot flies, as they do not have a long lifespan. Once they successfully mate and lay eggs on a new host, the life cycle starts anew.

Key Characteristics of Bot Flies:

• Parasitic
• Affects various host mammals
• Causes myiasis in host animals
• Distinct life cycle stages: egg, larva, pupa, and adult
• Species-specific host preferences

Pros and Cons of Bot Flies (from Carnivore Perspective):

Pros:

• Effective as a biological control agent against pest mammals in some environments

Cons:

• Detrimental to native wildlife populations if not controlled
• Can affect humans, causing discomfort and risk of secondary infections
• Difficult to eradicate due to their life cycle and host range

Bot Fly Infestation in Humans and Animals

Infestation in Humans

Bot flies are insects known to cause myiasis, an infection where their larvae (maggots) infest human tissue¹. Dermatobia hominis, also known as the human bot fly, is a common culprit of these infestations².

When a person becomes infected, the botfly larva burrows into their skin, leading to symptoms like swelling, inflammation, and irritation³.

Some potential complications of human infestations include:

• Infections: Bacteria introduced during infestation can cause infections⁴.
• Skin lesions: The burrowing larvae can cause painful ulcers or lesions⁵.
• Severe health problems: In some cases, the infestation can result in fever, chills, nausea, vomiting, and headaches⁶.

To treat a botfly infestation in humans, medical attention is crucial.

A physician will typically diagnose the issue and recommend surgical removal of the larvae, followed by antibiotics to reduce infection risks⁷.

Infestation in Animals

Apart from humans, bot flies such as Cuterebra fontinella also infest animals, particularly mammals like dogs and other pets⁸.

The infestation process is similar to that in humans, with botfly larvae burrowing into the animal’s skin, causing irritation and swelling⁹. Sometimes, these infestations can lead to noticeable warbles or lumps¹⁰.

In animals, bot fly infestations are typically addressed by veterinarians using methods like:

• Surgical removal: The botfly larvae are removed from the animal’s skin¹¹.
• Antibiotic ointment: To reduce infection risks, vets apply appropriate medication¹².

Possible complications and risks for animals include:

• Infections: Similar to humans, animals can develop bacterial infections from infestations¹³.
• Odor: Infestations can cause an unpleasant smell as the larvae pupate¹⁴.
• Inflammation: The burrowing larvae might lead to inflammation and irritation on the animal’s skin¹⁵.

Recognition and treatment for bot fly infestations in animals are essential to prevent complications or further health issues.

Geographic Distribution of Bot Flies

Bot flies are primarily found in the Neotropical regions, ranging from Southern Canada to Northeastern Mexico and throughout South America¹.

They frequently inhabit tropical areas, making their presence notable in countries like Mexico². In the United States, their distribution extends across the continental US, excluding Alaska².

One common species, Cuterebra fontinella, can be found in most of the continental US, Southern Canada, and Northeastern Mexico².

Adult bot flies, like Dermatobia hominis, are known to capture female mosquitoes and lay their eggs on them¹.

Features of Bot Flies:

• Large, robust flies with rounded heads³
• Chunky, beelike appearance³
• Adult bot flies are not commonly seen³

Characteristics of Bot Fly Larvae:

• Short, pudgy, and segmented³
• Live as parasites in the tissues of animals³
• May form a bulge (warble) under the skin of the host³

While bot flies can cause discomfort to their hosts, they are not typically considered dangerous to humans⁴. However, it’s still essential to remain cautious in areas where they are commonly found.

Prevention and Treatment of Bot Fly Infestations

To prevent bot fly infestations, consider the following measures:

• Avoid high-risk areas: Bot flies are common in the continental US, southern Canada, and northeastern Mexico. So, remain cautious when you travel through these regions. Depending on their type, bot flies can infect mammals, pets, or livestock.
• Use insect repellent: Apply repellent to skin and clothing to ward off mosquitoes, ticks, and fleas that can transmit bot fly larvae.
• Cover up: Wear long sleeves, pants, and closed shoes to minimize skin exposure in areas where bot flies are prevalent.
• Inspect pets: Check your pets for any suspicious lumps or bumps that could indicate the presence of bot fly larvae.

Treatment Methods

The following methods can help treat bot fly infestations:

• Seek professional help: Consult a physician or veterinarian for proper diagnosis and treatment.
• Surgical removal: In some cases, surgical removal of the larvae might be necessary. A doctor or veterinarian can take appropriate measures to remove the parasite safely.

Pros

• Effective in removing the parasite
• Prevents secondary infections

Cons

• Requires medical attention
• Can be painful, depending on the location of the larvae

Home removal: In some instances, home remedies can help remove bot fly larvae. For example, placing a piece of tape over the breathing hole can prompt the larva to come out.

However, this method should be used with caution and only after consulting a healthcare professional.

Pros

• Cost-effective
• Can be done without medical assistance

Cons

• May not be successful in all cases
• Can cause discomfort or harm if not executed correctly

Antibiotic ointment: After the larva is removed, applying antibiotic ointment can prevent infections and promote wound healing.

Therefore, adopting preventative measures and seeking timely treatment can help minimize the chances of a botfly infestation becoming a serious problem.

Conclusion

Bot flies can be considered dangerous to certain animals due to their parasitic nature and potential to cause myiasis.

While they typically do not pose a direct threat to humans, human botfly infections can be painful and require medical attention.

Understanding the life cycle and behaviors of bot flies can help debunk myths and reveal the facts about their potential risks and appropriate prevention and treatment measures.