Something’s living inside… my dog!!!
By Julaine Hunter, DVM
There are few more instantly gratifying problems in veterinary medicine to treat than a cuterebriasis case. Unlike abscesses that are fun to drain, a process which can be dramatic if not downright explosive, and which often make a big impression on both clients and experienced staff members, with cuterebra cases, there typically is no ongoing at home wound care required. No ecollar (Elizabethan collar, A.K.A., “cone of shame”) is typically warranted. The daily annoyance, at best, of administering oral antibiotic medications is most often unnecessary.
A cuterebra case is the instant gratification veterinarian’s dream. They are the ultimate crowd pleaser. Anyone who has had a parasitic infection or empathized with the victims portrayed in the Discovery Channel’s show: “Monsters Inside Me,” just wants them out. Most cases are uncomplicated, easy and relatively inexpensive to resolve, and typically do not require any additional and ongoing care. These little “blighters,” as a friend from across the pond is want to describe them, are the larval (or maggot, as some uncharitably describe them) stage of rodent or rabbit botflys. Generally speaking and due to their less fastidious nature when it comes to selecting a host, rabbit botfly larvae are the culprit when pets become “home” to developing botfly young. Even pets with limited exposure to the out-of-doors are susceptible if they have access to where the large, bee-like Cuterebra flies deposit their eggs, typically around the openings of animal nests, burrows or trails of their preferred hosts. Body heat emanating from animals passing through contaminated areas triggers hatching of the eggs and the newly released larvae can enter through any orifice, commonly the mouth, nostrils or an open wound when the pet is grooming itself. After skin penetration, these larvae may migrate to specific locations and develop and obtain air through a “breathing pore” in the victim’s skin. On average the offending larvae exit the skin, returning to the soil where they pupate.
Most of the cases I have personally treated have occurred either in the summer and fall, times of the year when most pets spend more time outside, depending upon the climate. Owners often first perceive a problem when matted hair with an associated and pus-draining wound is identified. On occasion, the area where this pest resides can swell a great deal, yielding a firm and fistulous mass. Often patients do not appear to feel any discomfort unless a secondary infection has occurred. Excessive grooming of the affected area often is seen, especially in affected cats.
In one of Dr. Bilhartz’s most recent cases, suspect lesions are explored through gentle manipulation of the larva’s breathing pore, A.K.A, fistula. (The lesion itself is NEVER squeezed to prevent chance rupture of the larva itself which could result in chronic local inflammatory reaction or, in exceedingly rare instances, the development of a severe, anaphylactic, life-threatening patient reaction. To avoid these risks, heavy sedation or light anesthesia is employed to prevent patient movement during extraction, the previously occupied “living space” is copiously flushed with sterile, physiologic saline, and the wound is permitted to heal from the inside out without suture closure to prevent sealing into the patient any bacteria or other contaminants present.