Wasp, Bee, and Ant Stings to Animals

Wasps and Bees of Medical Interest

Yellow jackets (subfamily Dolichovespula), hornets, and wasps (subfamily Vespula and Provespula) (see wasps image) are found mainly in Eurasia, North America, and North Africa. Wasps from the subfamily Polistinae are distributed in Africa south of the Sahara Desert, India, the Malaysian peninsula, Indonesia, Papua New Guinea, Australia, the southern and western parts of the US, Central and South America, Europe, and Asia (1).

Wasps

Image

Wasps in their nest. Note the sleek, elongated body characterized by a distinctly narrow waist (“wasp waist”) and bold, high-contrast, bright yellow and black colors.

Courtesy of Dr. Andrei Daniel Mihalca, University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca.

Bees are members of the Apidae family. The medically important species are the social bumblebees (subfamily Bombinae) and honeybees (subfamily Apinae). Bumblebees are distributed throughout the temperate regions of Asia, Europe, and North America. Honeybees are native to Africa, Asia, and Europe. However, after domestication, the common honeybee (Apis mellifera) is present worldwide and considered a cosmopolitan species (1).

Africanized honeybees (Apis mellifera scutellata) are a subspecies of the common honeybee that resulted from the hybridization of African honeybees (Apis melifera adansonii) introduced in Brazil in 1956 and the common honeybee. The hybrid species is much more aggressive and excitable when defending the hive, developing a swarming behavior. These Africanized honeybees, or “killer bees,” have spread throughout South and Central America and made their way to the southern US (1).

Africanized bees are difficult to distinguish morphologically from their European counterparts. One distinction is how they sting. Still a primarily defensive behavior, when an Africanized honeybee 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 can 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. Such large volumes of venom in a companion animal can make these exposures life-threatening.

Wasp and Bee Venom

The stinger of a wasp or bee is a modified ovipositor at the end of the abdomen in female drones. In honeybees, this stinger is barbed, resulting in death to the bee after stinging, as 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.

Bee venom contains compounds including vasoactive amines, hydrolyzing proteins, hyaluronidase, phospholipase, the neurotoxin apamin, melittin, and mast cell degranulating peptides. Phospholipases and hyaluronidases are responsible for allergic reactions (3). Phospholipase A2, one of the most potent components of bee venom, is a membrane disruptor and causes pain. Melittin, a hemolytic toxin and the main component responsible for the pain induced by the sting, is the main constituent of Africanized honeybee venom (4).

Bee venom is a well‑recognized cause of anaphylaxis by both immunological and nonimmunological processes. The immune‑mediated response can occur through the typical IgE‑dependent pathway or through an alternative mechanism driven primarily by IgG and platelet‑activating factor (5).

Vespid venom contains peptides, phospholipase A, hyaluronidase, kinins, biogenic amines, mast cell degranulating peptides, and neurotoxins. Components of the vespid venom trigger allergic reactions, pain, and vasoactivity (3).

Clinical Signs of Wasp and Bee Stings

In small animals, stings are most common on the face and in the mouth (4). Honeybee stingers can occasionally remain embedded in the sting area, and an abscess can develop (3). The venom causes localized pain and swelling, which can occur within minutes after the sting, progressing to erythema, edema, and anaphylaxis. Localized reactions resolve quickly, within minutes, unless severe reaction occurs.

Incidents of multiple stings from wasps or bees can cause severe local and systemic reactions. Possible systemic effects include prostration, seizures or CNS depression, bloody diarrhea, bloody vomiting, hyperthermia, immune-mediated anemia and thrombocytopenia, and renal and hepatic failure (4). Hemoperitoneum associated with anaphylactic shock has also been described (5).

In patients with massive envenomation, as with Africanized honeybees, clinical signs of facial paralysis, ataxia, seizures, and neurological effects can occur, with hematuria and hematochezia. Disseminated intravascular coagulation and immune-mediated hemolytic anemia are also concerns, with potential for renal failure secondary to acute tubular necrosis.

Treatment of Wasp and Bee Stings

If possible, removal of the stinger is recommended to treat wasp and bee stings, with additional treatment including pain management, application of a cool compress, and administration of antihistamines as needed, followed by supportive care.

In cases of severe anaphylaxis, more aggressive treatment, such as administration of IV fluids, corticosteroids, epinephrine, and antihistamines, might be indicated.

In the case of massive envenomation from Africanized honeybee stings — where victims may be stung by dozens to hundreds of bees — aggressive supportive care and monitoring is needed, including administration of IV fluid, antihistamines, and anticonvulsants as needed as well as pain management and cardiovascular support.

Ant Venom

Ant venoms are complex mixtures of alkaloids with cytotoxic and hemolytic effects. The main components are the solenopsins (primarily Solenopsin A) and a piperidine alkaloid that causes dermal necrosis (3, 6).

Clinical Signs of Ant Stings

Severely affected animals were likely unable to move away from the ant colony and received multiple stings. Clinical signs of exposure are a wheal and flare reaction, which typically resolves within an hour after the sting. In humans, a pustule can form and rupture at the site of the sting. However, this rarely develops in dogs. Instead, an erythematous pruritic papule is more common, and these resolve within 24 hours in most cases. Nonfollicular, circumscribed, yellow pustules with an erythematous halo have also been observed.

Dead fire ants can be attached to the skin and coat (6). In these cases, histological evaluation has revealed an intraepidermal pustule and dermal interstitial neutrophilic dermatitis with extension into the subcutaneous panniculus (6).

Anaphylaxis secondary to fire ant stings is not reported in companion animals.

Treatment of Ant Stings

In most cases, ant envenomation resolves with no treatment. In the case of multiple bites resulting in a more severe systemic reaction, patients can require supportive therapy similar to that for other hymenopteran stings.