Botfly Flies: Where In Australia Do They Thrive?

Botflies, also known as warble flies, heel flies, and gadflies, are flies of the family Oestridae. They are internal parasites of mammals, with some species growing in the host's flesh and others within the gut. The human botfly, Dermatobia hominis, is the only species of botfly whose larvae routinely parasitise humans. While botflies are commonly found in Africa and South America, there have been reports of travellers from Australia contracting botfly infections while visiting Bolivia. In addition, there is mention of the presence of botflies in South Australia in a 1909 newspaper article.

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Botfly in South Australia

Botflies, also known as warble flies, heel flies, and gadflies, are flies of the family Oestridae. Their larvae are internal parasites of mammals, with some species growing in the host's flesh and others within the gut. The human botfly, Dermatobia hominis, is the only species of botfly whose larvae routinely parasitise humans, although other species of flies can cause myiasis in humans.

In South Australia, the presence of botflies was noted in a 1909 issue of the Northern Times (Carnarvon, WA: 1905-1952). The article, titled "The Bot Fly in South Australia", highlights the issue of botflies in the region at the time.

Botflies deposit their eggs on a host, or sometimes use an intermediate vector such as mosquitoes or ticks. The female botfly captures the insect by holding onto its wings and attaches 15 to 30 eggs to its abdomen. The larvae from these eggs are stimulated by the warmth of a large mammal host and burrow underneath its skin. The eggs can also be deposited directly onto the skin of larger animals.

In horses, botflies lay their eggs on the insides of the front legs, below the knees, and sometimes on the throat or nose, depending on the species. These eggs must be carefully removed during the laying season to prevent infestation. When a horse rubs its nose on its legs, the eggs can be transferred to the mouth and eventually to the intestines, where the larvae attach themselves to the stomach lining or small intestine.

Botfly in Carnarvon, Western Australia

Botflies, also known as warble flies, heel flies, and gadflies, are flies of the family Oestridae. Their larvae are internal parasites of mammals, with some species growing in the host's flesh and others within the gut. The human botfly, Dermatobia hominis, is the only species of botfly whose larvae ordinarily parasitise humans, though other species of flies can also cause myiasis in humans.

In January 1909, an article titled "The Bot Fly in South Australia" was published in the Northern Times (Carnarvon, WA: 1905-1952). While the full article is not available, it indicates the presence of botflies in South Australia, including in the Carnarvon region of Western Australia.

Botflies deposit eggs on a host or use an intermediate vector such as mosquitoes or ticks. The female botfly captures the insect by holding onto its wings and attaches 15 to 30 eggs onto its abdomen. The larvae from these eggs are stimulated by the warmth of a large mammal host and burrow underneath the skin. The eggs can also be deposited directly onto the skin of larger animals.

Infection by botfly larvae, known as myiasis, can occur in humans who have travelled to regions where botflies are endemic, such as Central America. While myiasis does not occur in Australia, travellers returning to the country may unknowingly bring foreign fly species with them. As a result, it is essential for health professionals to be aware of potential myiasis infections to prevent the establishment of botflies and other foreign fly species in Australia.

Australian travellers infected with botfly in Bolivia

Botflies, also known as warble flies, heel flies, and gadflies, are flies of the family Oestridae. Their larvae are internal parasites of mammals, with some species growing in the host's flesh and others within the gut. While there are many species of botfly, only one, the human botfly (Dermatobia hominis), is known to routinely parasitize humans.

In 2013, an Australian couple in their late twenties from Sydney were infected with human botfly larvae during a trip to Bolivia. They initially believed the sores covering their bodies were infected mosquito bites, until they noticed the wounds were moving. They sought medical attention in Bolivia and learned they had human botfly larvae growing inside them. The human botfly is a parasite native to Central and South America, and its eggs are transported to hosts by mosquitoes, flies, and ticks.

Another case involved a 32-year-old Australian woman who, after travelling to Bolivia, developed a left lower leg ulcer with a sensation of movement within the lesion. She was seen by four primary care providers and was eventually referred to dermatology seven weeks after her return from Bolivia. At that time, she was found to have a 5 mm weeping ulcer with a live larva visible at the base. A punch biopsy was performed for botfly removal, after which the patient healed well.

These cases highlight the importance of recognizing the signs and symptoms of botfly infestation, particularly in travellers returning from endemic areas such as Central and South America and Africa. Diagnosis can be made through clinical presentation, history of travel, dermoscopy, and ultrasound, with treatment options including mechanical or surgical removal to reduce patient anxiety and the risk of secondary infection.

Botfly larvae in horses in Australia

Botflies, also known as warble flies, heel flies, and gadflies, are flies of the family Oestridae. Their larvae are internal parasites of mammals, with some species growing in the host's flesh and others within the gut. The human botfly, Dermatobia hominis, is the only species of botfly whose larvae ordinarily parasitise humans.

In Australia, botflies are a common issue for horse owners. The female adult bot fly will lay between 150 and 1000 eggs on a horse, predominantly on the hair of their legs, shoulders, and flanks. The positioning of these eggs means that they can be licked into the horse's mouth, where the larvae will bury themselves into the tongue, gums, or cheeks. From there, the larvae of two species, Gasterophilus intestinalis and Gasterophilus nasalis, migrate and attach themselves to the mucous lining of the horse's stomach and remain there during the winter. After about 10 months, they detach from the lining and are passed out of the body through the faeces.

The migration of the bot larvae under the skin and mucous membranes can cause lesions, which may provide openings for infection. Infestation with bot larvae can also cause ulcers in the stomach lining and, if severe, can block the opening from the stomach to the intestines, leading to irritation, ulcers, and even colic. Horses may show signs of infestation, including an inflamed mouth area and stomach irritation, but some horses can be severely infested without displaying any outward signs of illness.

To prevent botfly larvae from infesting horses, it is important to regularly remove eggs from the horse's coat. This can be done using a sharp knife, rough sandpaper, or a specialised equine safety razor. In addition, using a wormer that is effective against botfly larvae in autumn, when botflies begin their cycle, can help to control the population.

In summary, botfly larvae can cause significant health issues for horses in Australia, and it is important for horse owners to take preventative measures and be vigilant in removing eggs and treating infestations to protect their animals.

Botfly larvae in cattle in Australia

Botflies, also known as warble flies, heel flies, and gadflies, are flies of the family Oestridae. Their larvae are internal parasites of mammals, with some species growing in the host's flesh and others within the gut. The human botfly, Dermatobia hominis, is the only species of botfly whose larvae ordinarily parasitise humans. In the case of livestock, the female botfly captures another insect, such as a mosquito, and attaches her eggs to its abdomen. The larvae from these eggs are stimulated by the warmth of a large mammal host, such as cattle, and drop onto its skin, burrowing underneath.

In Australia, the presence of botflies has been noted in South Australia, with a newspaper article from 1909 discussing the issue. In terms of cattle, the cattle bot fly, Hypoderma bovis, is commonly called the heel fly in cattle farming. This species of bot fly attaches its eggs to the heel hair on the cattle's feet, causing the cow to jump and run wildly to escape the pest. Once the eggs are laid, the bot fly larvae chew through the skin of the heel area and travel up the legs to the throat and then the back, under the skin. The larvae chew holes for air as they prepare to leave the host, exiting the cow's back and dropping to the ground to complete their life cycle.

The presence of botfly larvae in cattle can cause economic losses for farmers and make the livestock suffer. In addition, the lesions caused by these flies can become infected by Mannheimia granulomatis, a bacterium that causes lechiguana, characterised by rapid-growing, hard lumps beneath the skin of the animal. To control botfly infestations, several types of dewormers can be used, including dichlorvos, ivermectin, and trichlorfon. Insecticides, such as permethrin or sulphate chemical control, can also be employed, but the risks and hazards of their use should be carefully considered.

The major importance of bot flies in cattle lies in the economic losses they cause in livestock operations. The presence of botfly larvae can affect the health and productivity of cattle, impacting the farming industry. Overall, while botfly infestations in cattle in Australia have not been extensively documented, the presence of botflies in South Australia and the economic implications of botfly larvae in livestock suggest that this may be an issue for cattle farmers in the region.

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