Botflies represent one of nature’s most unsettling parasites and belonging to the family Oestridae. They are known for their larvae, which develop inside the bodies of mammals, including humans. The larvae can grow in the host’s flesh or within the gut, making them obligate internal parasites. One of the most notable species that affects humans is Dermatobia hominis. Adult botflies are typically chunky and beelike, while their larvae are short, pudgy, and segmented grubs that live as parasites in the tissues of animals.
What Are Botflies? Understanding These Parasitic Insects
Botflies comprise over 150 species of parasitic flies. These insects complete their larval development inside living mammals, including humans, dogs, cats, horses, cattle, and wildlife. Unlike mosquitoes that simply bite and leave, botflies deposit their larvae beneath the skin, where they develop over several weeks.
The most common species affecting humans is Dermatobia hominis, known as the human botfly. Botflies species primarily inhabits Central and South America, though travellers can bring infestations back to other regions.
Why Botflies Matter to Pet Owners and Travellers
Veterinarians report thousands of botfly cases annually in domestic animals. Pet owners living in or travelling to endemic areas face real risks. Understand botfly behaviour helps you protect your family and pets from these parasites. Botflies infest the skin of both animals and humans, a condition called myiasis, by laying eggs on other insects which then transfer them to a host. The larvae hatch, burrow under the skin, and develop in a painful pustule, or “warble,” for several weeks before exiting to pupate.
🪰 Comprehensive Botfly Species Table
Complete guide to botfly species affecting humans and animals worldwide
| Botfly Species | Scientific Name | Primary Host | Lifecycle Duration | Signs & Symptoms | Disease/Condition | Treatment Protocol |
|---|---|---|---|---|---|---|
| Human Botfly | Dermatobia hominis | Humans, cattle, dogs, cats, mammals | 6-12 weeks (larval stage); 8-9 days (adult) | Small red bump with central breathing hole (punctum), intense itching, sensation of movement under skin, swelling, possible foul odor, sharp stinging pain when larva moves | Furuncular myiasis, secondary bacterial infections, rarely neurological complications if larvae migrate | Petroleum jelly suffocation method, surgical extraction under local anesthesia, oral ivermectin, bacon therapy. Clean wound with antibiotics post-removal |
| Common Horse Botfly | Gasterophilus intestinalis | Horses, donkeys, mules | 10-12 months (larval); eggs hatch 7-14 days | Yellow egg clusters on forelegs resembling paint drops, oral/gastric irritation, weight loss, colic, poor coat condition, reddish-orange cylindrical larvae visible in manure | Gastric myiasis, stomach erosions and ulcerations, intestinal blockage in severe cases, digestive impairment | Annual deworming with ivermectin, dichlorvos, or trichlorfon after first frost. Manual egg removal with bot knife or sandpaper during laying season (late summer/fall) |
| Throat Horse Botfly | Gasterophilus nasalis | Horses, donkeys | 10-12 months (larval development) | Eggs laid around lips and chin area, head shaking, difficulty swallowing, nasal discharge, larvae attach to soft palate and pharynx | Pharyngeal myiasis, throat irritation, breathing difficulties in heavy infestations | Same deworming protocol as G. intestinalis. Preventive measures include fly masks and repellents during egg-laying season |
| Nose Horse Botfly | Gasterophilus haemorrhoidalis | Horses | 8-10 months in digestive tract | Dark eggs on lips, facial irritation, gastrointestinal discomfort, larvae pass through and attach near anus causing irritation | Rectal myiasis, anal irritation, digestive disturbances | Ivermectin or moxidectin treatment. Regular monitoring and seasonal deworming programs |
| Common Cattle Grub (Warble Fly) | Hypoderma lineatum | Cattle, water buffalo, occasionally horses | 12 months total; larvae migrate through esophagus for several months before forming warbles | Eggs on lower body/legs, panic behavior (“gadding”) when flies approach, breathing holes on back, lumps along spine, reduced milk production, weight loss | Bovine hypodermosis, esophageal tissue damage during migration, hide damage with breathing holes, “butcher’s jelly” in muscle tunnels, bloat if larvae killed in esophagus | Ivermectin long-acting injection (prophylactic or therapeutic), eprinomectin, systemic macrocyclic lactones in fall before migration to vital organs. Topical tetrachlorvinphos dust on warbles |
| Northern Cattle Grub | Hypoderma bovis | Cattle, water buffalo | 12 months; larvae migrate through spinal canal region | Similar to H. lineatum but eggs laid singly on legs, severe panic reactions during egg-laying, warbles on back in late winter/spring, neurological signs if larvae near spinal cord | Bovine hypodermosis, spinal canal irritation, potential paralysis if larvae killed during migration, hide perforation, carcass damage, rarely intracerebral myiasis in humans | Same as H. lineatum – timing critical to avoid killing larvae near spinal canal. Treatment must occur in early fall during larval migration phase |
| Reindeer Warble Fly | Hypoderma tarandi | Reindeer, caribou, deer | 8-10 months development (similar to cattle warbles) | Warbles along back, reduced body condition, weakness in heavily infested yearlings, respiratory issues in severe cases | Cutaneous myiasis, hide damage, weight loss, rarely human ocular myiasis causing uveitis, glaucoma, retinal detachment | Ivermectin treatment in reindeer herds. Indigenous populations traditionally consume larvae during butchery as food source |
| Deer Nose Botfly | Cephenemyia stimulator | Deer (roe deer, white-tailed deer) | Larvae deposited directly into nostrils; mature in several months | Nasal discharge, head shaking, sneezing, visible larvae in nasal passages during field dressing, respiratory distress in heavy infestations | Nasal myiasis, sinus inflammation, rarely causes death by suffocation | Generally not treated in wild populations. Not harmful to humans; venison remains safe to consume. Antiparasitic drugs if treatment needed |
| Deer Bot Fly (North America) | Cephenemyia spp. (5 species) | White-tailed deer, mule deer, elk | 9-10 months; larvae overwinter in nasal passages | Larvae found in nasal cavities and throat during hunting season, nasal irritation, snorting, head shaking | Nasopharyngeal myiasis. Usually not harmful; rarely causes suffocation | No treatment necessary for wild deer. Not a public health concern for hunters or consumers |
| Rodent Botfly | Cuterebra fontinella | Mice, squirrels, rabbits, chipmunks; occasionally cats, dogs, ferrets | 3-4 weeks (larval development in host) | Large visible warble with breathing hole, usually on neck or shoulders, painful swelling (fist-sized in small animals), lethargy, fever if infected | Cutaneous myiasis, abscesses, risk of larvae migrating to brain/spinal cord/eyes in aberrant hosts (cats/dogs) causing seizures, paralysis, blindness | Surgical removal by veterinarian under sedation. Critical not to rupture larva. Antibiotics and anti-inflammatory drugs. Emergency care if neurological signs appear |
| Rabbit Botfly | Cuterebra spp. (multiple species) | Wild rabbits, hares, occasionally domestic rabbits | 4-6 weeks larval stage | Firm swelling with breathing hole typically on neck, back, or flanks, lethargy, decreased appetite, single or multiple warbles | Warbles (cutaneous myiasis), secondary infections, abscess formation | Careful surgical extraction avoiding larva rupture. Wound cleaning and antibiotics. Prevention difficult in outdoor rabbits |
| Sheep Nose Botfly | Oestrus ovis | Sheep, goats, occasionally humans | Larvae deposited directly; 8-10 months development | Nasal discharge, sneezing, head shaking, rubbing head on objects, “false staggers,” breathing difficulties, visible larvae in nostrils | Nasal myiasis (oestrosis), sinusitis, meningeal irritation in severe cases, human ocular myiasis if larvae sprayed into eyes | Ivermectin or closantel treatment in late summer/autumn before pupation. Systemic antiparasitic drugs. For humans: mechanical removal of larvae from eyes, symptomatic treatment |
Botflies (family Oestridae) are parasitic flies found worldwide that infest a wide range of warm‑blooded hosts, including humans, livestock, horses, cattle, deer, rodents, and companion animals. The most notorious species is Dermatobia hominis (human botfly), prevalent in Central and South America, which uses other insects to deposit eggs under the skin, leading to painful swellings and tissue damage. Other species, such as horse botflies (Gasterophilus spp.), cattle grubs (Hypoderma spp.), and rodent botflies (Cuterebra spp.), each have unique life cycles adapted to their hosts, causing conditions ranging from skin lesions to gastrointestinal distress. Globally, botflies pose significant veterinary and public health challenges due to their ability to compromise animal welfare, reduce livestock productivity, and occasionally infect humans. Effective management relies on early detection, parasite control, and preventive strategies tailored to regional species and host susceptibility.