The Hymenoptera order contains several venomous species, including honey bees, wasps, hornets, and yellow jackets. In most cases these species are not aggressive and only sting when disturbed or attacked. The stinger is a modified ovipositor at the end of the abdomen in female drones. In honey bees this stinger is barbed, resulting in death to the bee after stinging, because the stinger and venom sac are ripped from the abdomen. The other species’ stingers are not barbed, allowing wasps, yellow jackets, and hornets to sting multiple times. The venom contains several compounds, including vasoactive amines, hydrolyzing proteins, hyaluronidase, phospholipase, the neurotoxin apamin, and mast cell degranulating peptides.
The venom causes localized pain and swelling, which can occur within minutes of the sting, progressing to erythema, edema, and anaphylaxis. Localized reactions resolve quickly, within minutes, unless severe reaction occurs. If possible, removal of the stinger is recommended, with additional treatment including pain management, application of a cool compress, and administration of antihistamines as needed, with supportive care. In cases of severe anaphylaxis, more aggressive treatment, such as administration of IV fluids, corticosteroids, epinephrine, and antihistamines, may be indicated.
Brought to the New World by European settlers, the common honey bee spread and established itself in North and South America. African colonies of bees were bred with the more domesticated European varieties in laboratories in Brazil and escaped in 1957. The hybrid species is much more aggressive and excitable when defending the hive, developing a swarming behavior. These Africanized or “killer bees” spread throughout South and Central America, making their way to the southern US.
Africanized bees are difficult to distinguish morphologically from their European counterparts, but one distinction is how they sting. Still a primarily defensive behavior, the concern with Africanized bees is their habit to sting en masse. When the colony is threatened, the bees will repeatedly sting, resulting in hundreds, if not thousands, of stings, depending on the size of the colony. These bees may pursue their target for up to a kilometer from the hive, and the hives are located out in the open, where accidental exposure to companion animals can occur. The risk of such large volumes of venom in a companion animal can make these exposures life threatening.
In these patients, clinical signs of facial paralysis, ataxia, seizures, and neurologic effects can occur, with hematuria and hematochezia. Disseminated intravascular coagulation and immune-mediated hemolytic anemia is also a concern, with potential for renal failure secondary to acute tubular necrosis. Aggressive supportive care and monitoring is needed for these patients, including administration of IV fluid, antihistamines, and anticonvulsants as needed as well as pain management and cardiovascular support.
Introduced to the US in the early 20th century, red fire ants (Solenopsis invicta) and black fire ants (S richteri) can be found in the southeastern US stretching as far west as Texas. Similar to other hymenopteran insects, the females use a modified ovipositor or stinger to inject the venom. The ants will latch on with their mandibles, sting with a nonbarbed stinger, and move in a circular pattern, continuing to sting until the venom gland is empty.
Severely affected animals are likely those which were unable to move away from the colony and received multiple stings. Clinical signs of exposure are a wheal and flare reaction to the sting, which typically resolves within an hour of the sting. In humans, a pustule may form and rupture at the site of the sting, but this does not seem to develop in dogs. Instead, an erythematous pruritic papule is more common, but these resolve within 24 hours in most cases. Anaphylaxis is not reported secondary to fire ant stings in companion animals. In most cases, envenomation resolves with no treatment, but in the case of multiple bites resulting in a more severe systemic reaction, patients may require supportive therapy similar to that for other hymenopteran stings.