Discussion
North central Florida is a unique geographic area home to five
indigenous venomous pit vipers including water moccasins, and eastern
diamondback, timber and pygmy rattlesnakes. The amount of venom injected
varies according to the species, snake size, time lapse since the last
venom delivery, and degree of threat sensed prior to venom
delivery.10–12 Adult dogs might pose more of a threat
to the snake compared to the playful and naive nature of puppies which
would cause the snake to release more venom into the adult
victim.10 This might be a contributing reason to
explain why all five puppies in this series survived.
All five of the puppies were taken to the emergency hospital within a
two-hour period following their likely snake encounter. Four of these
were fortunate to maintain stable vital signs upon presentation. Case
two was on the threshold of decompensating, but readily stabilized with
emergency treatment. In envenomated children, their small size has
traditionally been thought to predispose them to a greater amount of
venom per square meter area, thus exposing more cells to the adverse
effects of the venom.13,14 In Parish’s study dating as
far back as 1965, the majority of children did well so long as they
received antivenom.13 In LoVecchio’s study of 66
envenomated children over a 10-year period, 38% of children developed a
hypersensitivity to whole IgG antivenom and there were five cases of
morbidity, but all survived.14 These reports of
increased rather than decreased survival is likely due to the
availability of antivenom and its use in children during the 1960’s and
after. The same guarded prognosis was assumed with this young canine
population, but all puppies in this report survived as well with timely
antivenom and medical management.
These five puppies are the first cluster of canine pediatric snake bite
victims, aged 11 to 20 weeks old, in the United States to be described.
The clinical signs in this particular group were similar to those seen
in many adult dogs in the same region.15,16 Two of the
four had prolonged activated clotting times, with bleeding restricted to
the bite site. The ACT was selected to monitor coagulopathy because of
the small amount of blood required for this test, its relative low cost,
proximity of the machine to the emergency room, and its proven clinical
benefits as a point-of-care test when managing snake bite victims with
coagulopathies.17
Three of the five puppies were bitten in the face while two were bitten
in the limbs which is similar to that seen in adult
dogs.15 The snake bite severity scores ranged from 1
to 10 with all values reverting to minor status by day two following
treatment.
The amount of antivenom administered to each puppy paralleled its SSS
whereby those with scores < 2 receiving 1-2 vials, and the
most severely affected puppy (case two) with a presenting score of 10
receiving proportionally more antivenom (nine total vials). None of the
puppies in this case series developed a hypersensitivity reaction to the
F(ab)2 antivenom§. In children,
hypersensitivity reactions to equine-derived IgG antivenom is common
(38%)14, while less common (2.8%)7when administered ovine-derived F(ab) antivenom. As this is a small case
series, it is likely that equine derived F(ab)2antivenom has the potential to cause hypersensitivity reactions in
puppies, similar to adult dogs.15
Fluid overload in children weighing less than 10 kg and those with
physiologic concerns for fluid overload, such as congestive heart
failure, chronic lung disease, and renal insufficiency is a concern in
human medicine when multiple doses of antivenom are administered as
their protocols typically dilute antivenom in 250 mL 0.9%
saline.7 Puppies in this study ranged from 4.3 to 15.2
kilograms, and the same risk for fluid overload should be considered
when treating pediatric dogs requiring multiple doses of antivenom. In
this series, antivenom was diluted in 50 to 100 mL 0.9% saline at the
clinician’s discretion, and no reported complications from fluid
overload occurred.
The small number of puppies included in this case series limits
statistical analysis to determine prognostic factors. In addition, due
to the retrospective nature of this case series and medical record
system at the author’s institution, cases were obtained by searching
invoice items for pit viper antivenom and age of six months or less in
dogs. As such, puppies presenting to the emergency room with a snake
bite, but did not receive antivenom, due to lack of clinical need or
owner financial restrictions, would have been overlooked in data
collection. Therefore, prospective studies to enroll all pediatric dogs
with a witnessed or suspected pit viper envenomation are warranted to
determine morbidity and mortality.