Occupational Snake Bites: a Prospective Case Series of Patients Reported to the ToxIC North American Snakebite Registry

ORIGINAL ARTICLE

Occupational Snake Bites: a Prospective Case Series of Patients

Reported to the ToxIC North American Snakebite Registry

Meghan B. Spyres

& Anne-Michelle Ruha

& Steven Seifert

& Nancy Onisko

Angela Padilla-Jones

& Eric Anthony Smith

American College of Medical Toxicology 2016

Abstract

Introduction In the developing world, occupation has been

identified as a risk factor for snake bite. Such an association

has not been described in the USA. The objective of this study

was to describe the epidemiology and clinical manifestations

of occupational snake bite in patients reported to the ToxIC

North American Snakebite Registry (NASBR).

Methods This was a prospective case series of patients report-

ed to the ToxIC NASBR between January 1, 2014 and

November 5, 2015. Variables collected included snake spe-

cies, patient demographics, date and location of exposure,

occupation, bite location, clinical manifestations, and

management.

Results Of 180 adult snake bites reported, 25 (13.9 %; 95 %

CI 9.2–19.8 %) were occupational in nature. Rattlesnake

envenomations were common (80 %). Most snake bites

(96 %) occurred in men. Occupations most associated with

snake bite were landscaping (28 %) and working directly with

snakes (24 %). Fifty-six percent of bites occurred in an out-

door work environment. Seventy-six percent of

envenomations were to the upper extremities. Intentional in-

teraction occurred in 40 % of cases, all of which sustained

finger envenomations. No cases presented with apparent acute

ethanol intoxication.

Conclusions The majority of occupational snake bites oc-

curred in men working outdoors and were unintentional inju-

ries. Bites involving the upper extremity tended to result from

intentional interactions. Acute ethanol intoxication did not

appear to be involved with occupational envenomations.

Keywords Snake bite

Occupation

Envenomation

Risk

factor

Introduction

In the USA, nearly 10,000 snake bites are treated in the

Emergency Department (ED) each year resulting in significant

morbidity and rare mortality [1]. Both native and non-native

snakes are implicated in these bites. In the USA, the Viperidae

family (rattlesnakes, cottonmouths, and copperheads), and the

Elapidae family (coral snakes) are responsible for native snake

envenomations. Viper envenomations typically cause tissue

and hematologic toxicity, although neurologic symptoms can

occur with some species. Anaphylaxis and shock also rarely

occur [2]. Elapid envenomations, conversely, are characterized

by neurologic toxicity [3]. Serious envenomations also occur

after exposure to captive non-native snake species [4].

Characteristics of individuals sustaining snake envenomations

in the USA have been previously described [1, 5––8]. Men are

over-represented, frequently comprising approximately 70–80 %

of patients [1, 6, 8]. Extremity bites are common, and intentional

interaction with snakes is often associated with upper extremity

bites [6]. Rattlesnakes are responsible for the majority of venom-

ousbites[1]. Young adults are more frequently affected than

children and the elderly [7]. Ethanol intoxication has often been

associated with snake bites, particularly when interaction is

This research was presented in abstract form at NACCT 2015

* Meghan B. Spyres

mspyres@gmail.com

Department of Medical Toxicology, Banner-University Medical

Center Phoenix, 925 E. McDowell Road, 2nd Floor,

Phoenix, AZ 85006, USA

New Mexico Poison Center, University of New Mexico Health

Sciences Center, Albuquerque, NM, USA

North Texas Poison Center, Parkland Health and Hospital System,

Dallas, TX, USA

DOI 10.1007/s13181-016-0555-7

Received: 2 February 2016 /Revised: 5 May 2016 /Accepted: 9 May 2016

J. Med. T oxicol. (2016) 12:3 –

/Published online: 2 2016

7 May

65 69

intentional [6]. Envenomations are more common between

March and October , peaking in the summer and fall when human

outdoor and snake activities are highest [6].

Worldwide, occupational exposure has been identified as a

significant risk factor for snake bite. Although the epidemiol-

ogy and clinical manifestations of such exposures has been

described in other parts of the world [4], data for this popula-

tion in the USA is lacking. Despite the paucity of data, occu-

pational snake envenomation in the USA does appear to play a

significant role. In a recent review, 30 % of venomous snake

bites occurred in the workplace [1]. Another review of non-

native snake bites reported 11 % occurring in the workplace

setting [4]. This study aims to describe the epidemiology and

clinical manifestations of occupational snake bites in the USA

using data reported to the Toxicology Investigators

Consortium (ToxIC) North American Snakebite Registry

(NASBR).

Methods

This was a prospective case series. Data reported to the ToxIC

NASBR between January 1, 2014 and November 5, 2015

were reviewed.

The ToxIC Registry was established in 2010 by the

American College of Medical Toxicology (ACMT) as a novel,

prospective toxico-surveillance and research tool. It records

all cases cared for at the bedside by medical toxicologists at

each of more than fifty sites across the USA that actively

contribute cases to the Registry. The Registry allows for

pooling of detailed, de-identified clinical information from

across all Registry centers.

The Registry is Health Insurance Portability and

Accountability Act (HIPAA) compliant and no patient identi-

fiers are available on the database. Participation in the Registry

is done in accordance with local institutional and Western

Internal Review Board (IRB) policies and procedures.

ACMT’s ToxIC NASBR Sub-Registry is a database that

gathers de-identified, detailed prospective information regard-

ing snake bite, clinical manifestations of envenomation, and

response to treatment for patients who receive bedside care

from medical toxicologists across the USA. Occupational na-

ture of snake bite was determined by the treating clinician for

each case and was a mandatory field in the Sub-Registry.

Inclusion criteria were: age ≥ 18 years and occupational

exposure leading to snake bite. Data collected included

patient demographics, date and location of exposure, oc-

cupation, bite location, snake species, clinical manifesta-

tions, outcomes, and management. Method of identifica-

tion of snake was not specified. Data for late bleeding

events were obtained from direct patient contact or tele-

phone interview.

Statistical Analysis

Descriptive statistics were used to report results. The Clopper

Pearson method [9] was used to determine 95 % confidence

intervals (CI).

Results

Cases

Between January 1, 2014 and November 5, 2015, 180 snake

bites in adult patients were reported to the ToxIC Registry.

Nine US states were represented. Twenty-five (13.9 %;

95 % CI 9.2–19.8 %) cases occurred during an occupational

exposure to the snake and all occupational exposures identi-

fied were included in analysis. All occupational

envenomations took place in seven US states (Table 1). The

majority (52 %) of occupational snake bites occurred in

Arizona. The greatest number of cases were reported between

May and September, a pattern similar to that of the larger

NASBR population. See Fig. 1.

Types of Snakes

There were 20 native rattlesnake, three copperhead, and two

non-native pit viper (Crotalus durissus terrificus and

Trimeresurus albolabris) snake bites reported. Rattlesnakes

were not consistently identified by species. Four (16 %) oc-

cupational snake bites occurred after exposure to captive

snakes, and the remainder (84 %) were secondary to wild

native snakes. Captive snakes included the two non-native

snakes, the South American rattlesnake (Crotalus durissus

terrificus) and the green pit viper (Trimeresurus albolabris),

as well as two native snakes, the Arizona black rattlesnake

(Crotalus cerberus) and the western diamondback rattlesnake

(Crotalus atrox).

Table 1 Occupational and total snake bites by state

US state Total cases Occupational

cases (% total)

Arizona 79 13 (17)

Texas 37 4 (11)

California 21 3 (14)

North Carolina 15 1 [7]

Missouri 9 1 (11)

Colorado 7 0

New Mexico 6 2 (33)

Utah 4 1 (25)

Pennsylvania 2 0

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366

Demographics and Occupation

Twenty-four (96 %) patients were men and one was a woman.

The average age was 40.3 years (range 18–66 years). One

patient was aged over 65. Two (8 %) patients had sustained

previous snake bites. This was the fourth envenomation for

one patient, employed as a venomous animal educator.

Six (24 %) patients were employed working directly with

snakes and se ven (2 8 %) were employed in landscaping.

Fourteen patients (56 %) worked outdoors. See Table 2 for a

full list of occupations. Acute ethanol intoxication was not

present in any case.

Envenomation Details

Nineteen (76 %) snake bites occurred to the upper ex-

tremities, predominantly to the finger, and six (24 %)

occurred to the lower extremities, predominantly to the

lower leg. See Fig. 2. Fifteen (60 %) cases were

Blegitimate bites,^ meaning the interaction with the

snake was unintentional. Ten (40 %) cases involved

intentional interaction with the snake, and all of these

individuals sustained upper extremity finger bites (Fig.

3). All p atients worki ng directly with snakes also

sustained finger bites. None of the lower extremity bites

involved intentional interaction with t he snake. The s in-

gle woman was bitten on the finger after intentional

interaction with a snake that had incidentally entered

her animal care facility.

Outcomes and Management

Field therapy in the form of ice application was performed in

one case. Time to presentation to health care was 3 h or less in

all but one case in which there was a 48 h delay (average 3.4 h,

range 20 min to 48 h). Antivenom (Crofab™,BTG

International in 22 cases, Green Pit Viper Thai Red Cross

Antivenom in 1 case) was given in 23 (92 %) cases, with an

average total dose of 10 vials (range 2–24 vials) per case.

1111

Month

Occupational

Total Snake Bites

Fig. 1 Occupational and total

snake bites by month

Table 2 Occupation of

snake bite victims

Occupation Cases

Landscaper 7

Snake handler/caretaker 3

Construction worker 2

Oil field worker 2

Snake remover 1

Venomous animal educator 1

Camp counselor 1

Mechanic 1

Engineer 1

Truck driver 1

Medicine man 1

Animal care facility manager 1

Biologist 1

Corrections officer 1

Professional mountain biker 1

Number of Cases

Bite Location

Foot

Ankle

Lower le

Forerm

Hand

Finger

Fig. 2 Anatomic location of occupational snake bites

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Mean time to antivenom administration after snake bite was

5.6h(range1–48 h). Clinical manifestations and laboratory

results are described in Table 3 and Table 4, respectively. One

patient was administered prophylactic antibiotics , and one

underwent wound debridement. There were no fasciotomies.

No patient was treated for late bleeding and there were no

deaths.

Discussion

Occupation as a risk factor for snake bite has been de-

scribedinothercountries.InSouthEastAsia,farmingis

the occupation most associated with snake bite and farmers

represent approximately 80 % of snake bite victims in

India [10]. In such an environment, bites to the lower ex-

tremities predominate. This contrasts significantly from the

results seen in this study, in which there was not a single

reported case of occupational snake bite in a farmer. In this

study, the majority of bites were to landscapers, followed

by sna ke handlers and others whose emplo yment places

them in direct contact with snakes.

Also in contrast to data from South East Asia, the major-

ity of bites in this study were to upper extremit ies, frequent-

ly accompanied by intentional interaction with the snake.

This dat a is in agreement with other modern studies of

snake bit es in the U SA which also demonstrate an associa-

tion between intentional interaction w ith snakes and upper

extremity bites. The majority (60 %) of bites in this study

involved unintentional interaction with the snake. These

data, in contrast, differ from most modern snake bite studies

in the USA in which the majority of bites result from int en-

tional interaction with snakes [4, 6, 7]. Factors that may

have contributed to an increased proportion of unintentional

envenomations in this population are speculative but may

include absence of ethanol intoxication and occupations

exposin g victim s to snake habita ts .

Similar to other snake bite series, male victims predominat-

ed. Perhaps the preponderance of men, rather than women,

employed in landscaping contributed to the persistence of this

trend in this series. Additionally, bites were most likely to

occur in the summer and fall months in this group, months

when snakes are more active. Overall, individuals are more

frequently out of doors both recreationally and for employ-

ment purposes during these months, however this may not

hold true for more southern states such as Arizona.

Uniquely, ethanol intoxication was not present in any case

of occupational snake bite, a finding that differs significantly

from other studies of snake bite victims. This is somewhat

expected, as consuming ethanol or other intoxicants while

working is typically discouraged. Although it would be ex-

pected that clinicians at the bedside would be able to detect

ethanol intoxication in these patients, victims of occupational

envenomations may have ulterior motivations to deny ethanol

intoxication under such circumstances. Method of determina-

tion of ethanol intoxication (i.e., clinician judgment, patient

report or laboratory confirmation) was not reported.

Limitations

This review of data reported to the NASBR Sub-Registry

presents limitations inherent to voluntary reporting of data to

a registry. Although the NASBR undergoes quality assurance

Number of Cases

Interaction Type

Lower extremit

Upper Extremit

Fig. 3 Patterns of intentional and unintentional occupational snake bites

Table 3 Incidence of clinical manifestations in occupational snake bites

Rattlesnakes (% total) Copperheads (% total) Non-natives (% total)

Swelling 19 (100) 3 (100) 2 (100)

Ecchymosis 7 (37) 1 (33) 1 (50)

Erythema 7 (37) 2 (67) 0

Emesis 2 (11) 0 1 (50)

Neurotoxicity 2 (11) 0 1 (50)

Hypotension 0 0 0

Minor Bleeding 3 (16) 0 0

Necrosis 1 [5] 0 0

Angioedema 1 [5] 0 0

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368

review to identify and correct errors or omissions in data entry,

it is possible that all errors were not identified. Notably, the

majority of cases took place in Arizona. Data reported for

occupations and snake species are thus skewed towards those

typical of this geographical region. Limited availability of

follow up data in a large number of cases prevented accurate

reporting of such outcomes. Lastly, the small number of oc-

cupational envenomations resulted in a small sample size.

This limited conclusions that can be drawn from the data

and limited generalizability of findings.

Conclusions

Occupational exposure represented 13.9 % of snake bites in

adults reported to the ToxIC Registry. The majority of occu-

pational snake bites occurred in men working outdoors and

were unintentional injuries. Bites involving the upper extrem-

ity tended to result from intentional interactions. Acute etha-

nol intoxication did not appear to be involved with occupa-

tional envenomations. These findings need to be validated in a

population with a large sample size.

Acknowledgments The authors express gratitude to the staff at the

American College of Medical Toxicology (ACMT) for support of the

North American Snakebite Registry (NASBR) within the ToxIC

Registry project. We would also like to thank the members of the 2015

To xIC Snakebite Study (TICSS) group: Anna Arro yo-Plascencia,

Vikhyat S. Bebarta, Michael C. Beuhler, William Boroughf, Jeffrey

Brent, Daniel Brooks, E. Martin Caravati, James D. Cao, Nathan

Charlton, Steven Curry, Michael Darracq, William Dribben, Kimberlie

Graeme, Spencer Greene, Benjamin Hatten, Kennon Heard, C William

Heise, Janetta Iwanicki, Aaron Min Kang, William P Kerns II, Thomas

Kibby, Joshua King, Ronald Kirschner, Kurt Kleinschmidt, Ken Kulig,

Michael Levine, Rachel Levitan, Elizabeth Moore, Philip Moore,

Michael Mullins, Eleanor Oa kley, Ayrn O’Connor, Nancy Onisko,

Angie Padilla-Jones, Tammy Phan, Frank LoVecchio, Anne-Michelle

Ruha, Steven A. Seifert, Daniel J Sessions, Aaron Skolnik, Eric Smith,

Meghan Spyres, An Tran, S. Eliza Halcomb, Evan S. Schwarz, Shawn M.

Varney, Rais Vohra, Brandon J. Warrick, Sam G. Wang, Paul Wax, and

Brian J. Wolk.

Compliance with Ethical Standards

Conflicts of Interest Authors Meghan Spyres MD, Anne-Michelle

Ruha MD, Steven Seifert MD, Nancy Onisko DO, Angela Padilla-

Jones RN, and Eric Smith MSIS have no conflicts of interest to declare.

Funding There was no direct funding for this project.

BTG International sponsored an unrestricted grant to ACMT for the

NASBR registry.

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Table 4 Mean laboratory results in occupational snake bites

Rattlesnakes (range) Copperheads (range) Non-natives (range)

Platelet nadir (K/mm

) 216 (51–310) n = 20 168 (104–214) n = 3 177 (169–184) n =2

Fibrinogen nadir (mg/dL) 272 (153–415) n = 20 251 (227–274) n = 2 97 (<30–164)

n =2

Prothrombin Time peak (sec) 21 (11- > 120)

n =19 12(11–12) n = 3 20 (16–24) n =2

For fibrinogen < 30, a value of 30 was used to calculate the mean

For prothrombin time > 120, a value of 120 was used to calculate the mean

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