Reptile envenomation 20-year mortality as reported by US medical examiners.

Objectives: Accurate reptile envenomation mortality data for the United States is unavailable. Using data from the National Vital Statistics System (NVSS), deaths from 1979 through 1998 were analyzed.

Methods: Records of deaths from reptile envenomation were selected using matches to code E905.0 of the International Classification of Diseases, Ninth Revision. Data for the US population was taken from the 2000 US census estimates.

Results: The National Vital Statistics System identified 97 deaths from venomous reptile bites that occurred during the study period. Texas (n = 17), Florida (n = 14), and Georgia (n = 12) reported the most fatalities (44% of fatalities, 16% of 2000 US population). No deaths were reported from 24 states or the District of Columbia. Of the 97 decedents, 88 (91%) were white and 7 (7%) were black. One male and one female were categorized as "other" race. White males had the highest incidence of death by reptile envenomation, accounting for 76% of all fatalities, while comprising only 41% of the US population. Accounting for 19 of the 97 fatalities, males 25 to 34 years old had the most deaths (19.6% of deaths, but 7.1% of the 2000 US population).

Conclusions: From 1979 through 1998, less than 100 deaths by venomous reptile bite were reported nationwide. White male Southerners appear to be at greatest risk. This finding of a specific high-risk population may require further investigation and public health intervention.

Key Words: reptile envenomation, US mortality

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Each year in the United States, snake envenomations are responsible for a significant number of injuries. (1) Accurate data on reptile envenomation mortality in the United States is unavailable because reporting of envenomations is not mandatory for public health authorities. Each year the American Association of Poison Control Centers reports deaths that occur as a result of snake envenomations that were reported to US poison centers, but it is doubtful that poison control centers are consulted in every snake envenomation-related mortality. However, states do require completion of death certificates. Deaths during the period from 1979 through 1998 were analyzed using data from the National Vital Statistics System (NVSS), a cooperative agreement between the National Center for Health Statistics (NCHS) and all 50 states (and the District of Columbia) in which fatalities are reported in a standard format.

Materials and Methods

Data from the NVSS for the years from 1979 through 1998 were analyzed. During this specific 20-year period, records were coded exclusively using the International Classification of Diseases, Ninth Revision (ICD-9) external cause of injury codes (E-codes). For this study, records of deaths from reptile envenomation were selected using ICD-9 code E905.0. The NVSS data are based on information from death certificates filed in the 50 states and the District of Columbia. Data for the US population was taken from the 2000 US census estimates.

Results

During the reporting period, NVSS identified a total of 97 deaths from venomous reptiles. Texas (n = 17), Florida (n = 14), and Georgia (n = 12) reported the most fatalities (44% of fatalities, 16% of 2000 US population), and were the only three states to report more than 10 fatalities for the 20-year period. Twenty-four states and the District of Columbia reported no deaths (Table 1). Males accounted for 78% of the total deaths (Table 2).

Of the 97 decedents, 88 (91%) were white (74 males and 14 females), and 7 (7%) were black (1 male and 6 females). One male and one female were categorized as of "other" race. White males had the highest incidence of death by venomous reptiles (Figure), accounting for 76% of all fatalities while comprising only 41% of the US population. The age category comprising "men 25 to 34 years old" had the most deaths, 19 of the 97 fatalities (19.6% of deaths but 7.1% of the 2000 US population) (Table 3). Females older than 55 had more deaths (n = 13) than females less than 55 years old (n = 8).

Discussion

There were less than 100 deaths due to venomous snakes during the 1979 through 1998 period as reported by NVSS. This is less than one previous estimate of up to 15 deaths per year. (2) Three southern states were the only states to have more than 10 deaths in the two decade period, accounting for 43 (44%) of 97 total deaths.

One possible explanation for the higher number of deaths in Southern states is that there is a higher concentration of venomous snakes there. While snake envenomations are rare in the Midwest and Northeastern states, venomous snake density studies have not been performed. (3) Local customs in the South such as "rattlesnake roundups" and the use of venomous snakes by religious sects could increase the number of envenomations by encouraging human interaction with venomous snakes. The Humane Society of the United States (4) lists 27 annual rattlesnake roundups in the United States. Nine are held in Texas and two in Georgia.

The range of the Eastern diamondback rattlesnake (Crotalus adamanteus) is limited principally to Florida, southern Georgia, and surrounding areas. The Eastern diamondback produces the largest volume of venom when milked, and has one of the more lethal venoms according to median lethal dose rodent studies. (3) The presence of this snake in Florida and Georgia could be responsible for the relatively large number of deaths in these two states. However, the NVSS does not list the species of the venomous reptile causing the death, therefore this possible explanation needs further research.

While the administration of snake antivenin has never been proven to reduce mortality in a randomized study, most experts consider it to be almost essential in managing snake envenomation victims. (5) The cost of antivenin might preclude some hospitals from stocking sufficient supplies. The wholesale acquisition cost of antivenin in 2003 has ranged from $800 to $1,250 per vial. Since a victim could in some cases need up to 40 vials of antivenin, the cost of stocking an adequate supply to treat one potential victim is close to $50,000. Some hospitals stock only enough antivenin to begin therapy, perhaps because of this high stocking cost, and intend to obtain more once a victim presents for treatment. However, nationwide shortages of antivenin have occurred, which may have contributed to patients getting inadequate antivenin therapy. Furthermore, some practitioners do not believe in the effectiveness of antivenin, and treat victims with supportive care and surgical excision. (6) It is possible that this management strategy has contributed to the higher incidence of snake envenomation deaths in the Southern states.

The NVSS data does not specify the number of nonnative snakes that caused mortality. Nonindigenous venomous reptiles are kept in zoos and in households as pets, even though the practice of keeping venomous reptiles as pets violates state regulations in many states. The limited availability of high-quality antivenin to treat for injuries from these exotic reptiles might also play a role in mortality rates.

White males were those with the highest incidence of death by venomous snakebites, contributing to 76% of all fatalities while comprising only 41% of the US population. Blacks represented only 7% of the victims while comprising 12.9% of the US population. Of the three leading snake envenomation states, blacks comprise 28.7% of Georgia's population, 14.6% of Florida's, and 11.5% of the Texas population. The social or biologic factors contributing to this finding are unknown, and cannot be ascertained from the information in this study.

Our study involves limitations resulting from dependence on national vital statistics data collected over the two decade period, and the lack of availability of medical records to eliminate contributing or confounding factors. The possibility of diagnostic drift exists, but snake envenomation has a distinct clinical picture, and an exclusive ICD-9 code was used. Misreporting the cause of death can under- or over-report deaths by envenomation. However, in most states animal-related deaths are investigated, and the cause of death confirmed by the medical examiner.

Conclusion

According to NVSS data from the period from 1979 through 1998, less than 100 deaths by venomous reptile bite were reported nationwide. White male Southerners appear to be at greatest risk for mortality as a result of reptile envenomation. This finding of a specific high risk population, if confirmed by further investigation, may support the need for public health intervention.

Table 1. State death counts

State                                Raw death count

Alabama                                    4
Arizona                                    7
Arkansas                                   1
California                                 6
Colorado                                   2
Florida                                   14
Georgia                                   12
Idaho                                      2
Kansas                                     1
Kentucky                                   4
Louisiana                                  1
Maryland                                   1
Mississippi                                2
New Mexico                                 2
New York                                   1
North Carolina                             2
Ohio                                       1
Oklahoma                                   2
South Carolina                             4
South Dakota                               1
Tennessee                                  2
Texas                                     17
Virginia                                   3
Washington                                 2
West Virginia                              2
Wyoming                                    1

Table 2. Sex as percentage of total deaths from reptile envenomation

                  Raw death               Percentage death
Sex                 count                    count (%)

Female               21                         22
Male                 76                         78
Total                97                        100

White/F                  14%
White/M                  77%
Black/F                   6%
Black/M                   1%
Other/F                   1%
Other/M                   1%

Percentage of death count, by race and gender, for reptile envenomations
in the United States for the period from 1979 through 1998.

Table 3. Age and sex as percentage of total deaths from reptile
envenomation

Age                                                 Percentage of total
(yr)                 Sex         Raw deaths           death count (%)

   0-14               M               6                      6
   0-14               F               4                      4
  15-24               M               7                      7
  15-24               F               0                      0
  25-34               M              19                     20
  25-34               F               1                      1
  35-44               M              12                     12
  35-44               F               2                      2
  45-54               M              13                     13
  45-54               F               1                      1
  55-64               M               8                      8
  55-64               F               5                      5
> 65                  M              11                     11
> 65                  F               8                      8

Accepted January 8, 2004.

Copyright [c] 2004 by The Southern Medical Association

0038-4348/04/9707-0642

References

1. Litovitz TL, Klein-Schwartz W, Rodgers GC Jr, et al. 2001 Annual report of the American Association of Poison Control Centers Toxic Exposure Surveillance System. Am J Emerg Med 2002;20:391-452.

2. Gold BS and Barish RA. Venomous snakebites: current concepts in diagnosis, treatment and management. Emerg Med Clin N Am 1992;10:249-267.

3. Russell FE. Venoms, in Russell FE (ed): Snake Venom Poisoning. Great Neck, New York: Scholium International Inc., 1983, p. 139-234.

4. The Human Society of the United States. Annual Rattlesnake Roundups in the United States. Available at http://www.hsus.org/ace/12011. Accessed October 28, 2003.

5. Gold BS, Dart RC, Barish RA. Bites of venomous snakes. NEJM 2002; 347(5):347-356.

6. Haung TT, Lynch JB, Larson DL et al. The use of excisional therapy in the management of snakebite. Ann Surg 1974;179:598-607.

RELATED ARTICLE: Key Points

* The National Vital Statistics System identified 97 deaths related to reptile envenomation from 1978 to 1997.

* Texas, Florida, and Georgia had the most deaths.

* White males between the ages of 25 and 34 appear to be at greatest risk.

Brent W. Morgan, MD, Catherine Lee, MPH, Luke Damiano, MD, Kenneth Whitlow, DO, and Robert Geller, MD

From the Departments of Emergency Medicine, Environmental and Occupational Health, and Pediatrics, Emory University School of Medicine; and the Georgia Poison Center, Grady Health System, Atlanta, GA.

Reprint requests to Brent W. Morgan, MD, Grady Health System, Georgia Poison Center, 80 Jesse Hill Jr. Drive, Atlanta, GA 30303. Email: [e-mail]