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                    Echinocytosis Associated with Rattlesnake Envenomation in Dogs
                              D. E. Brown, D. J. Meyer, W. E. Wingfield and R. M. Walton
                                                Vet Pathol 1994 31: 654
                                         DOI: 10.1177/030098589403100604

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Vet Pathol 31:654-657 (1994)




                         Echinocytosis Associated with Rattlesnake
                                  Envenomation in Dogs
                    D. E. BROWN, J. MEYER, E. WINGFIELD, R. M. WALTON
                               D.        W.           AND

        Departments of Pathology (DEB, DJM, RMW) and Clinical Sciences (WEW), Colorado State University,
                      College of Veterinary Medicine and Biomedical Sciences, Fort Collins, CO

         Abstract. A retrospective study of 28 cases of rattlesnake bites in dogs indicated an association of enven-
      omation with echinocytosis; 25/28 dogs (89%) had echinocytosis within 24 hours of a rattlesnake bite being
      reported. Eighteen of the 28 dogs had marked type I11 echinocytosis (95-1 00% of mature erythrocytes affected),
      and seven dogs had moderate echinocytosis (15-30°/o of mature erythrocytes affected). The echinocytosis was
      transient, resolving within 48 hours of envenomation in those for which subsequent blood films were available
      (13/25). Hypokalemia was noted in 14 of 18 dogs for which biochemical data were available. The hypokalemia
      was not consistently associated with echinocytosis. The observation of echinocytosis in dogs supports a clinical
      diagnosis of rattlesnake envenomation.

        Key words: Dogs; echinocyte; erythrocyte; snakebite.

   Echinocytes are erythrocytes that have uniformly the nature of spiculation, as previously described.16 Eryth-
sized, regularly spaced projections from their mem- rocytes were counted in five oil-immersion fields at 1,000x
branes. The exact mechanism for echinocytic shape magnification to quantitatively assess percentage of echino-
change is unknown.12 Echinocyte formation can be an cytes present.
artifactual result of pH change from slow drying of                The packed cell volume (PCV), mean cell volume, and
                                                                 platelet count were reviewed from the 28 cases. Follow-up
                            may
blood films (~renation),'~ result from depletion of
                                                                 complete blood counts (CBCs) were evaluated when available
erythrocytic adenosine 5'-triphosphate (ATP) or in- (15/28 cases). Hemograms were performed with a multi-
creased cytosolic calcium and exposure to anionic am- channel blood cell counting system (Coulter Counter S-Plus
phipathic drugs,I2J6 and may be secondary to total body IV with histogram capability or Coulter T660, Coulter Co.,
cation depletion.'^^^ Echinocytosis has been associated Hialeah, FL).
with specific diseases, including glomerulonephritis and           Serum biochemical analyses were available for 18/28 dogs.
lymphosarcoma in the dog16 and pyruvate kinase de- Because many of these dogs were admitted on an emergency
ficiency in Basenjis.2 A burring phenomenon of eryth- basis to the critical care unit, complete serum biochemical
rocytes has been reported with snakebite in human profiles were not always done. The most common serum
 being^,^^^ a finding supportive of e n v e n ~ m a t i o n . ~ .analytes measured in this study were blood urea nitrogen
                                                                  ~
Erythrocyte burring has also been reported with coral (BUN), creatinine, sodium. and potassium. Serum analyses
                                                                 were performed on discrete automated analyzers (Hitachi
snake envenomation in dogs.8 This burring phenom-
                                                                 704, Boehringer-Mannheim, tndianapolis, IN, or Dupont
enon is morphologically compatible with echinocytes. ACAIII, Dupont, Wilmington, DE).
   A transient echinocytosis often develops rapidly in
dogs envenomated by rattlesnakes. The purpose of this In vitro studies
study was to retrospectively examine the association                Echinocyte formation can be an artifactual result of pH
of echinocytosis with rattlesnake envenomation in dogs. change from slow drying of blood films (~renation).'~            To
                                                                            evaluate this possibility, one drop of EDTA-preserved blood
                 Materials and Methods
                                                                            from each of five dogs with rattlesnake envenomation was
Retrospective studies                                                       mixed on a glass microscope slide with one drop of isotonic
  Wright-Giemsa-stained blood films were reviewed from                      saline. A coverslip was applied, and the slide was examined
28 dogs bitten by rattlesnakes from 1988 to 1993. The dogs                  by light microscopy with partial closure of the diaphragm.
were historically healthy; males and females of various breeds              As controls, saline wet preparations of blood were prepared
were represented. Initial blood films were collected within                 simultaneously from nonenvenomated healthy dogs.
24 hours of a reported bite, and subsequent blood films were                                               Results
available for 15/28 dogs. Blood films were made from eth-
ylenediaminetetraacetic acid (EDTA)-preserved blood.                          In eighteen of 28 dogs (64%), 95-100% of mature
Echinocytes were characterized as types 1-111, dependent on                 erythrocytes were type I11 echinocytes (Fig. l), which
                                                                       654




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Vet Pathol 31:6, 1994                  Canine Echinocytosis and Rattlesnake Bite                                           655




  Fig. 1. Blood; Labrador Retriever. Dog was envenom-        Fig. 2. Saline preparation, EDTA-preserved blood; Lab-
ated by a rattlesnake approximately 4 hours prior to sam-  rador Retriever. Dog was envenomated by a rattlesnake ap-
pling. Echinocytic erythrocytes are numerous. Polychromat- proximately 4 hours prior to sampling. Echinocytic eryth-
ophilic erythrocytes retain their discoid shape (arrows). rocytes are present. No stain. Bar = 10 pm.
Wright-Giemsa stain. Bar = 10 pm.
                                                                        first 24 hours following envenomation. The echino-
are described as "ovoid or spherical cells with 10 to                   cytosis decreased from 100% to < 30% of cells affected
30 sharp, regularly spaced projections."I6 In seven dogs,               without normalization of serum potassium in five dogs.
within the first 24 hours 15-309'0 of mature erythro-                   Three dogs had echinocytosis with the serum potas-
cytes were echinocytes (type I1 and type III), and three                sium concentration within the reference range.
dogs had no echinocytes (one of these had spherocy-                        Complete blood counts showed a mild decrease
tosis). All polychromatophilic erythrocytes observed                    (mean decrease of 7.1%) in PCV in 10 of 28 dogs. In
had normal morphology (Fig. 1). Subsequent CBCs                         four of these dogs, PCV returned to reference range by
were available for 13/25 dogs with echinocytosis.                       day 2-6 following envenomation. In the remaining six
Echinocytes accounted for 5 30% of mature erythro-                      dogs, no follow-up CBC was performed. One anemic
cytes in 12 of these dogs by 48 hours; in one dog, 100%                 dog had spherocytosis and erythrocyte agglutination
of mature erythrocytes were echinocytes at 48 hours.                    with no echinocytes. Mean cell volumes were within
There did not appear to be a correlation in the reduc-                  reference range for all 28 dogs. There was thrombo-
tion of echinocytes and whether or not antivenin treat-                 cytopenia (platelet counts < 150,OOO/pl) in 18 of 28
ment was given.                                                         dogs; eight dogs normalized by day 2-6 following en-
   Hypokalemia was the only consistent biochemical                      venomation. The other 10 dogs had no follow-up. The
abnormality in 14 of 18 dogs (78%). Mean serum po-                      mean platelet count for envenomated dogs with throm-
tassium was 3.6 mEq/liter (range, 2.9-4.0 mEq/liter;                    bocytopenia was 70,000 plateletdpl (range, 11,000-
reference range, 4.1-5.5 mEq/liter). All 18 dogs had                    131,000 plateletslpl).
normal BUN and serum creatinine concentration. Only                        The majority of erythrocytes from envenomated dogs
one dog was hyponatremic. Nine of 14 dogs with hy-                      were echinocytic on saline wet preparations, supporting
pokalemia also had marked echinocytosis within the                      an in vivo phenomenon (Fig. 2). Saline wet prepara-




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656                                      Brown, Meyer, Wingfield, and Walton                                        Vet Pathol 3 1 5 , 1994


tions of blood prepared simultaneously from nonen-                     find hypokalemia in 14/18 dogs (78%). The cause of
venomated healthy dogs had normal discoid erythro-                     the hypokalemia was not apparent, and its association
cytes.                                                                 with echinocyte formation is unknown, although elec-
                                                                       trolyte alterations may be invo1ved.'J5 Hypokalemia
                      Discussion                                       in these cases was not consistently associated with
   Our study demonstrated a strong association be-                     echinoc ytosis.
tween echinocyte formation and envenomation.                              Sixty-four percent of the dogs had thrombocytope-
Echinocytes were present within 24 hours of a snake-                   nia, and 44% of those had returned to reference range
bite (89% of cases), and the shape change largely re-                  by day 2-6; no follow-up was available for the re-
solved by 48 hours. Although the majority (64%) of                     mainder of the dogs. The effects of rattlesnake enven-
dogs bitten had marked type I11 echinocytosis, there                   omation on platelets and coagulation have been pre-
was variation in percent echinocytosis among individ-                                                Platelet
                                                                       viously r e p ~ r t e d . ~ . ~ J ~ J ~ aggregation induced
uals. These differences may represent delayed time to                  directly by venom components and/or endothelial
presentation following bite, lower dose of venom re-                   damage with exposure of underlying collagen and
ceived, or no envenomation (no echinocytes). The ob-                   platelet aggregation at the site of vascular wall injury
servation that polychromatophilic erythrocytes ap-                     may contribute to the thrombocytopenia observed in
peared resistant to echinocyte transformation is not                   dogs in this study.'JOApproximately 20% of poisonous
explained. These cells are more resistant to crenation                 snakebites do not result in envenomation.ll Early di-
than are mature erythrocyte^.^ Polychromatophilic                      agnosis of envenomation is critical to appropriate ther-
erythrocytes, in contrast to mature erythrocytes, still                apeutic intervention. The observation of echinocyto-
have mitochondria and the ability to aerobically gen-                  sis, in dogs supports a clinical diagnosis of rattlesnake
erate ATP, therefore, they may be more resistant than                  envenomation. Use of a saline wet preparation is a
mature erythrocytes to potential ATPase effects of snake               quick, simple procedure that can be used to identify
venom.                                                                 echinoc ytosis.
   Mild anemia occurred in 10 of 28 dogs with return
of PCV to reference range by day 2-6 following en-                                                     References
venomation in four dogs. The remaining six dogs did
                                                                         1 Geor RJ, Lund EM, Weiss DJ: Echinocytosis in horses:
not have follow-up CBCs. Anemia may be due to cell
                                                                           54cases(1990). J AmVetMedAssoc202:976-980, 1993
destruction following envenomation, a phenomenon                         2 Giger U, Noble NA: Determination of erythrocyte py-
that is reportedly dose related in human beings3 One                       ruvate kinase deficiency in Basenjis with chronic he-
anemic dog had spherocytosis and erythrocyte agglu-                        molytic anemia. J Am Vet Med Assoc 198: 1755-1 76 1,
tination. Spherocytosis and intravascular hemolysis                         1991
have been described secondary to envenomation in                         3 Huang TT, Lewis SR, Lucas BS: Venomous snakes. In:
human beings9 This dog did not have echinocytosis.                         Dangerous Plants, Snakes, Arthropods and Marine Life
Echinocytosis was a reversible change based on the                         Toxicity and Treatment, ed. Ellis MD, pp. 132-1 33. Drug
fact that the echinocytes had nearly disappeared by 48                     Intelligence, Hamilton, IL, 1978
hours following envenomation without a correspond-                       4 Huang TT, Lynch JB, Larson DL, Lewis SR: The Use of
                                                                           Excisional Therapy in the Management of Snakebite.
ing decrease in PCV.
                                                                           Ann Surg 179:598-607, 1974
   Rattlesnake venom is a complex mixture of approx-                     5 Jain NC: Schalm's Veterinary Hematology, 4th ed., pp.
imately 30 enzymatic and nonenzymatic proteins, the                        500-501. Lea and Febiger, Philadelphia, PA 1986
composition of which can vary greatly even among                         6 Kitchens CS: Hemostatic aspects of envenomation by
snakes of the same species.13Phospholipases and pro-                       North American snakes. Hematol Oncol Clin North Am
teases are two of 10-15 enzymes found in all snake                         6:1 189-1 195, 1992
venoms, including ratt1e~nakes.l~     Possible mecha-                    7 Mansfield PD: The management of snake venom poi-
nisms for echinocytic change in erythrocytes of snake-                     soning in dogs. Compend Cont Ed Pract Vet 6:988-992,
bite victims include ATP depletion of membrane cat-                         1984
ion pumps by ATPases and alteration of erythrocytic                      8 Marks SL, Mannella C, Schaer M: Coral snake enven-
membrane composition by phospholipases. Both                               omation in the dog: report of four cases and review of
                                                                           the literature. J Am Anim Hosp Assoc 26:629-634,1990
ATPases and phospholipases are present in rattlesnake
                                                                         9 Roberts JR: The diagnosis and treatment of snakebite.
venom, and induction of echinocytes can be secondary                       In: Principles and Practice of Emergency Medicine, ed.
to ATP depletion and phospholipase activation.I2 De-                       Schwartz GR, Cayten CG, Mangelsen MA, Mayer TA,
hydration of erythrocytes might occur as a result of                       and Hanke BK, 3rd ed., pp. 2769-2770. Lea and Febiger,
systemic electrolyte depletion.'.15                                        Philadelphia, PA, 1992
   Although it was not the objective of our study to                    10 Ruiz CE, Schaeffer RC, Weil MG, Carlson RW: He-
examine possible pathogenetic mechanisms, we did                           mostatic changes following rattlesnake (Crofalus viridis




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Vet Pathol 31:6, 1994                     Canine Echinocytosis and Rattlesnake Bite                                                   657

     helleri) venom in the dog. J Pharmacol Exp Ther 213:                     the Dog and Cat, ed. Ettinger SJ, 3rd ed., pp. 2 15 1-2 153.
     414-417, 1980                                                            WB Saunders, Philadelphia, PA, 1989
11   Russell FE: Snake venom poisoning in the United States.               15 Weiss DF, Geor R, Smith CM, McClay CB: Furose-
     Annu Rev Med 31:247-259, 1980                                            mide-induced electrolyte depletion associated with
12   Smith JE: Review erythrocyte membrane: structure,                        echinocytosis in horses. Am J Vet Res 53: 1769-1 772,
     function, and pathophysiology. Vet Pathol 2447 1-476,                    1992
     1987                                                                  16 Weiss DJ, Kristensen A, Papenfuss N, McClay CB:
13   Van Mierop LHS: Poisonous snakebite: a review. 1.                        Quantitative evaluation of echinocytes in the dog. Vet
     Snakes and their venom. J Ha Med Assoc 63: 19 1-200,                     Clin Pathol 19:114-118, 1990
     1976                                                                  17 White RR, Weber RA: Poisonous snakebite in central
14   Weiser MG: Erythrocytes and associated disorders. In:                    Texas. Ann Surg 213:466-472, 199 1
     Textbook of Veterinary Internal Medicine, Diseases of




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