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Venomous arthropods (Proceedings)

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Apr 01, 2008

Many bites and stings inflicted by venomous arthropods (arachnids and hymenoptera) are poorly understood. Medical management of these envenomations can be difficult and information not readily available.

The primary Hymenoptera of medical concern are the bees, wasp and ants. In humans the majority of fatalities from animal interaction come from the members of this class. Often deaths are induced by anaphylactic reactions to the venom.

The primary arachnids we are concerned with in veterinary medicine are the spiders (Black Widows and Brown Recluse); in North America scorpion stings are not medically significant in dogs and cats.

Hymenoptera:

BEES: (Bumble bees – Bombus sonorous); (Honey bees – Apis mellifera)

Bees are social insects and live in colonies, bumble bee hives usually are comprised of 200 or so members and can be contrasted with honey bee nest with over 100,000 members. The members of the hive will aggressively defend the nest as a group. Aggression is usually triggered by CO2 and the bees attack dark colors. The initial attackers release an alarm pheromone when they sting which attracts the other members of the hive. The major difference between honey bees and so called African "killer" bees is not related to venom but rather aggressiveness, these bees will pursue for extended distances (often in the kilometer range) and are stimulated into an aggressive state quicker.

The venom of bees is delivered by a stinging apparatus which is detached from the body, killing the bee. The smooth muscle of the venom sac injects the venom rapidly with 90% of the venom released within 20 seconds and 100% in less than a minute. The alarm pheromone is released at the same time.


Primary Bee Venom Fractions And Actions
The major venom fractions consist of peptides, proteins and enzymes. The main peptides/proteins are peptide 401, apamin and melittin. The primary enzymes are phospholipase A2 and hyaluronidase.


Number Of Stings Per Kilo Body Weight - Dogs
Local clinical signs include a weal with a central red spot, edema, pruritis, pain and the stinger may still be embedded. Systemic clinical signs generally depend upon number of stings received. Allergic deaths require a single sting; however multiple stings have resulted in reports in man of acute renal failure, rhabdomyolysis, optic neuritis, atrial flutter/defibrillation, hepatic dysfunction, disseminated intravascular coagulation and marked respiratory distress.

Generally first aid recommendations are to immobilize the affected limb and if necessary use an epinephrine kit while in transit to veterinary facility. Most deaths occur within one hour highlighting the need to aggressively stabilize the patient and rapidly transport to a critical care facility. Once hospitalized primarily supportive care should be instituted. Medical response to allergic reactions may include epinephrine, glucagons, volume support, type 1 & 2 antihistamines, albuterol and possibly corticosteroids??

WASP: (Yellow jackets – Vespula sp., Dilichovespula sp., Vespa sp. ; Paper wasp – Polistes sp.)

These hymenoptera may be aggressive alone or in conjunction with the hive. Generally hive numbers are lower than bees. Venom delivery is accomplished by stinging, however these species do not have barbed stingers allowing multiple stings from a single wasp.


Primary Wasp Venom Fractions And Effects
The major venom fractions include enzymes such as phospholipase, hyaluronidase and cholinesterases; peptides such as mastoparans; and amines.