Abstract
Introduction
The black widow spider, Latrodectus mactans, stands out as one of the most medically significant arachnids due to its extensive geographic distribution in the United States and its ability to produce a potent neurotoxin, α-latrotoxin. This study aimed to describe the epidemiology of black widow spider exposures by month of exposure, geographic distribution, demographics, symptoms, treatment, and health system resource utilization between 2012 and 2022.
Methods
This was a retrospective observational study using the US National Poison Data System, the data warehouse of the 55 US poison centers. A descriptive analysis of patient demographic data, month of exposure, clinical effects, level of healthcare received, and medical outcome was performed.
Results
During the studied period, a total of 15,299 cases of Latrodectus spp exposures were reported to US poison centers. Exposures occurred with higher frequency in warm-weather states and during summer months. Almost half the cases were managed outside a healthcare facility (48.6%). Hospital admission was required for 10.0% of exposures. The most common therapies received were wound care (43.7%) and benzodiazepines (18.6%). Antivenom was administered in 3.4% (n=521) of exposures.
Conclusions
Poison center data indicate that most black widow spider exposures result in minor consequences. Supportive care is the primary approach for black widow spider bites. Although antivenom use is infrequent, providers may seek administration guidance from toxicologists through local poison centers. This study underscores the pivotal role of poison centers in mitigating unnecessary healthcare visits and subsequent hospitalizations.
Introduction
The black widow spider (BWS), Latrodectus mactans, stands out as one of the most medically significant arachnids due to its extensive geographic distribution and ability to produce a potent neurotoxin. 1 Latrodectus spp inhabit every state in the United States, with the exception of Alaska. 2 The production of clinically significant envenomation is exclusive to female BWSs owing to their larger size. These females are distinguished by a distinctive red-orange hourglass marking present on their ventral abdomen.1,3,4 Although these spiders can be dangerous, they are typically not aggressive and tend to bite only when they or their web are disturbed. 1 BWS venom contains a combination of toxic components including active proteins. 3 Of these, the most toxic to humans is a neurotoxin, α-latrotoxin, that binds presynaptic receptors to induce neurotransmitter release. 5 The release of norepinephrine and acetylcholine stimulates motor end plates, triggering the major symptoms of BWS envenomation: muscle pain and rigidity. Later, depleted synaptic vesicles likely lead to a blockage of neurotransmission, which may account for the waxing and waning of symptoms often seen in patients with BWS envenomation. Other released neurotransmitters include dopamine, glutamate, and enkephalin.3,5
Most patients report an initial pricklike sensation with the bite, which later becomes an erythematous, raised halo. Severe envenomation with α-latrotoxin may result in systemic toxicity known as latrodectism. Neuromuscular spasms, rigidity, autonomic disturbances, and marked tachycardia can occur. Symptoms most commonly affect the shoulders, back, chest, and abdomen.1,3 Diaphoresis, nausea, vomiting, headache, and numbness can occur. Although bites to the extremities are the most common locations, no studies show association between bite location and severity of envenomation. Rare but serious complications have been reported, including myocarditis, myocardial infarction, agitation, compartment syndrome, severe hypertension, respiratory distress, and priapism.1,3,4,6 Preexisting hypertension greatly increases risk of stroke, myocardial infarction, or heart failure after BWS evenomation. 3 No reported deaths have occurred due to BWS envenomation in the United States., but in other parts of the world, 3 deaths have been reported, related to bites from L geometricus and L tredecimguttatus spiders. 5 Severity of envenomation can vary and likely is rooted in differences in the spider or in the patient. The size, age, and associated health problems of the victim may impact their clinical presentation. The very young and elderly are at higher risk of more severe symptoms. 3
There currently exist no tests specific for BWS venom, but leukocytosis, albuminuria, and elevated creatine phosphokinase concentrations are common. 7 Identification of the spider can aid in diagnosis. 6 Management of BWS envenomation is largely supportive with emphasis on treatment of pain and muscle spasms, which may be severe and difficult to control. Symptoms may exhibit a waxing and waning course. Pain management for minor symptoms includes the application of local ice to the site of envenomation and the use of systemic nonsteroidal anti-inflammatory drugs. For moderate to major envenomation, intravenous opioids and/or benzodiazepines are commonly administered to control pain and spasms. In severe envenomation, patients may be admitted for in-patient management until the pain resolves.1–3,8
Antivenom for α-latrotoxin terminates pain within hours but is often unavailable. 9 Antivenom is composed of equine whole immunoglobulin against α-latrotoxin.4,10 The benefits of antivenom include faster pain relief and fewer hospital courses. 8 Adverse effects are rare (0.54% of patients receiving antivenin) but have included anaphylaxis, complement-mediated anaphylactoid reaction, and serum sickness. Death has occurred secondary to antivenom-induced bronchospasm.11,12
Calcium gluconate (10%) therapy was at one point considered an effective treatment for BWS envenomation after it demonstrated in vitro stabilization of nerve membrane permeability. This treatment has largely been abandoned due to proven lack of effectiveness in vivo.1,2,5,8
There have been no recent studies reviewing data on US BWS human exposure epidemiologic trends, subsequent therapies given to mitigate symptoms, or the type of health system resources used following exposure. This study aimed to describe the recent epidemiology of BWS exposures in the United States by month of exposure, geographic distribution, demographics, symptoms, treatment, and health system resources utilization between 2012 and 2022.
Methods
Study Design and Case Selection
This was a retrospective observational study using the National Poison Data System (NPDS). NPDS is the database of the 55 US poison centers (PCs). PCs submit de-identified case data to NPDS after providing necessary poison exposure management and information services to callers from the general public and healthcare providers. NPDS generic code 0194000 was used to query all human Latrodectus spp exposures between January 1, 2012, and December 31, 2022. Cases classified as a confirmed nonexposure (reliable and objective evidence that exposure to Latrodectus never occurred) were excluded.
The medical outcome of a case is assigned by the PC staff based on the NPDS coding manual. Cases are coded as no effect (no symptoms occurred due to exposure), minor effect (symptoms were minimally bothersome), moderate effect (symptoms were more prolonged or systemic and usually required treatment), major effect (symptoms were life threatening or resulted in significant disability or disfigurement), and death. Further details regarding data collection in NPDS are detailed in the NPDS annual reports. 13
Statistical Analysis
We performed a descriptive analysis of patients’ demographic data, month of exposure, clinical effects, level of healthcare received, and medical outcome. Categorical variables including gender, reason for exposure, clinical effects, therapies, and medical outcome were presented as frequencies and percentages. Continuous variables such as age were presented as medians with interquartile ranges.
Results
During the study period, a total of 15,299 cases of Latrodectus spp exposures were reported to PCs. Demographic characteristics are summarized in Table 1. The most common age group was 30 to 39 y (n=2903; 19.0%), closely followed by 20 to 29 y (n=2717; 17.8%) and 40 to 49 years (n=2,231; 14.6%). Exposures occur with higher frequency in the states of California (n=4355; 28%), Arizona (n=1751; 11%), Texas (n=1287; 8%), New Mexico (n=836; 5%), and North Carolina (n=666; 4%) (Figure 1). Most exposures occurred in the summer and early fall months. Exposures start rising in spring months, continue to increase during summer months, and peak in September. Exposures start to decrease in October, with the lowest number of exposures reported during wintertime (December–February) (Figure 2).
Demographic characteristics of black widow spider exposures reported to US poison centers, 2012-2022.
HCF, healthcare facility; AMA, against medical advice
Most individuals (n=13,788; 90.1%) were exposed in their own residence. Almost half the cases were managed on site and were not transferred to a healthcare facility (n=7441; 48.6%). One third of individuals received care at a healthcare facility but did not undergo inpatient admission (n=4946; 32.3%). Only 10.0% (n=1548) of exposures resulted in hospital admission, and 2.1% (n=324) required admission to a critical care unit. A total of 10,692 exposures (69.9%) resulted in no more than a minor effect, and only 121 (0.8%) resulted in a major effect (Table 1).
The most frequently reported symptoms were puncture wounds (n=9158; 59.9%), dermal irritation (n=7009; 45.8%), and erythema/flushing (n=3139; 20.5%). Nondermal pain occurred in 18.5% of exposures (n=2; 830). Edema occurred in 14.3% of exposures (n=2192). No deaths were reported, but there was one case of cardiac arrest reported in relation to BWS exposure (Table 2).
Summary of symptoms and therapies reported to US poison centers following black widow spider exposures, 2012-2022.
Opioids for analgesia were first captured in 2019. Between 2019 and 2022, 833 of 4145 patients with exposures (20.0%) received opioids for pain management.
The most common therapy received was irrigation and washing of the wound (n=6692; 43.7%), followed by administration of benzodiazepines (n=2848; 18.6%). Data on therapy with opioids for analgesia were first captured in 2019. Between 2019 and 2022, 833 patients of 4145 exposures (20.0%) received opioids for pain management. Antivenom was administered in only 3.4% (n=521) of exposures. During the study period, only 98 (0.6%) patients were treated with calcium gluconate.
Discussion
Analysis of the NPDS data contributes to an understanding of the clinical manifestations and management approaches in BWS exposures. The data indicate that a majority of BWS exposures lead to minor consequences, often not warranting immediate medical intervention. Individuals exhibiting either no symptoms or mild manifestations may consider conservative management at home, employing measures such as ice compresses, acetaminophen, and ibuprofen. 14 Remarkably, >90% of cases stemmed from exposures occurring in residential settings, implying the potential role of prompt consultation with PCs in mitigating unnecessary medical visits to emergency departments for individuals experiencing minimal or negligible effects.
However, a subset of cases may exhibit more pronounced effects following BWS exposure. Such cases may result in presentation to a healthcare facility. Although there are no clinical tests that can confirm BWS envenomation, providers can provide supportive care to treat more severe symptoms, such as opioids or benzodiazepines.2,8 Envenomation typically follows a self-limited course, with symptoms resolving within 24 to 48 hours. 8 Although approximately one third of patients received medical attention at healthcare facilities, only 10% were admitted to hospital. These findings suggest the potential contribution of PCs in averting unnecessary hospital admissions.
Despite the existence of a BWS antivenom that is approved by the Food and Drug Administration, its accessibility across healthcare institutions is limited, compounded by its associated risks, including anaphylaxis. The use of antivenom in the NPDS data accounted for a mere 3.4% of all exposures over the 11-y study period. During this period, the manufacturer downscaled production, leading to shortages of supply. 9 The NPDS data do not provide clarity on whether reduced use stems from restricted access or practitioner reluctance. Antivenom may retain a targeted role in specific clinical scenarios. In consideration of its limited accessibility, PCs and toxicologists play a crucial role in offering guidance for the administration of antivenom. Despite the widespread acknowledgment of calcium gluconate's ineffectiveness, 2 it was still administered in 98 cases between 2012 and 2022.
This study observed a notable decline in reported BWS exposures from 2012 to 2022. However, NPDS is subject to reporting bias. Reporting to PCs is voluntary and therefore is not representative of all poisoning cases occurring in the United States. As various encounters become more prevalent in society, healthcare professionals become more adept at recognition and treatment and may not routinely seek expert advice or report these cases to PCs, explaining the decrease in the number of reported BWS exposures. We did not study case management and outcome by state, and the use of antivenom may not reflect the general practice on a national level. For example, almost 30% of the cases reported to NPDS are from the state of California, and the reported use of antivenom may be affected by practice patterns in the state of California alone.
As shown in Figure 1, exposures occur with higher frequency in warm-weather states, potentially reflecting a relationship with warmer temperatures. Seasonal trends (Figure 2) showed that BWS exposures were reported predominantly during warmer months, coinciding with increased outdoor activities and potential exposure scenarios. This temporal pattern also may correlate with varying venom potency in warmer climates, potentially influencing symptom severity and reporting frequency. Severe envenomations necessitating treatment may be reported more frequently than those not requiring medical intervention. 15
Geographical distribution of black widow spider exposures reported to US poison centers, 2012-2022.
Monthly trends of black widow spider exposures—US poison centers, 2012-2022.
Conclusions
The NPDS analysis indicates that the majority of BWS exposures result in minor consequences not requiring medical intervention. Severe cases may be managed in healthcare facilities. Although antivenom use is infrequent, providers may seek administration guidance from toxicologists through PCs. Supportive care is the primary approach for BWS envenomation. This study underscores a potentially pivotal role of PC services in mitigating unnecessary healthcare visits and subsequent hospitalizations.
Footnotes
Author Contribution(s)
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.
