34 reports of snakebite envenoming by the Western Hognose snake (Heterodon nasicus): a retrospective online survey

The Western Hognose snake, Heterodon nasicus, is earth’s most commonly kept venomous pet snake. Generally assumed to be harmless, recent reports suggested a more potent venom than originally thought, but literature is scarce. Here, we analyze the severity of bites among keepers of this species via a retrospective online survey. In 34 reports, symptoms were mentioned. They range from local pain for short time frames to extensive edema that resolve after several days or weeks. Severity was correlated with exposure time to the bite. While symptom resolution time can be long in intense cases, no sequelae or fatalities occur and envenoming can be prevented by simple security measures, such as using gloves. Therefore, we evaluate the venom of H. nasicus to be indeed more damaging than hitherto assumed, yet the species appears to pose no severe danger to humans and we do not see the necessity to impose legal constraints on its role within the pet trade and husbandry.

Snakes are globally important components of the international pet trade and enthusiastically kept in many households. One of the most commonly encountered snake species is the Western Hognose snake, Heterodon nasicus. This small-bodied colubrid naturally occurs in Canada, the United States, and Mexico, where it inhabits several dry habitats and exhibits a semi-fossorial lifestyle (Averill-Murray, 2009). Because of its attractive phenotype and easy husbandry requirements, this species has manifested as a staple in the herpetocultural community and is frequently bred (Stallins and Kelley, 2013). In countries such as Germany, the United Kingdom, or the United States, it is under the top 10 pet snake species, only surpassed by various boas and pythons as well as the corn snake (Pantherophis guttatus) (Krautwald-Junghanns, 2018; Animal Welfare Committee, 2023; Personal communication with international breeders and keepers, 2025).

Interestingly, H. nasicus also carries a functional venom system, commonly unknown or neglected (Weinstein et al., 2022; Kroll, 1976). This makes H. nasicus by definition earth’s most commonly kept venomous pet snake, even so neither highly dangerous nor deadly. As a non-front fanged snake (NFFS), it harbors enlarged, ungrooved fangs connected to a venom-producing gland in the anterior part of its upper jaw, referred to as the Duvernoy’s gland (Taub, 1967). As for most snake venoms, its function is assumed to be for prey subjugation and appears to be relatively simple (Brandehoff et al., 2019; Hill and Mackessy, 2000). A detailed venomics analysis of its composition remains missing thus far. First impressions on molecular weights suggest venom components such as CRISP (cysteine-rich secretory protein), svMP (snake venom metalloproteinase), and phosphodiesterase, comparable to other NFFS venom compositions (Brandehoff et al., 2019; Modahl and Mackessy, 2019).

Traditionally, H. nasicus has been considered non-venomous and fully harmless to humans. However, this outdated view still persists in the community. One reason might be the low amount of available literature, which are not always freely available. For example, PubMed as an important, openly accessible database lists only 18 references, of which less than half are about bites or venom of H. nasicus. Less than 15 sporadic reports across the last century (Bragg, 1960; Morris, 1985; Weinstein et al., 2022; Zieliński, 2021) as well as two reported cases of more severe envenomation have been published (Brandehoff et al., 2019; Weinstein and Keyler, 2009) raising the question as to whether the initial assessment of this snake’s potential to cause harm needs to be reevaluated. This topic remains largely unexplored despite its relevance given the frequency with which this snake is kept privately around the globe and the low number of case or experience reports.

Therefore, we leverage the global community of herpetoculturalists keeping this species and implement them as a target group for a specifically designed online questionnaire. Through this, we strategically identify the prevalence and symptomatic spectrum of H. nasicus bites alongside key data on the respective victim, the snake, and the bite context. We report the details and image documentations of four cases in which photos were provided. Thereby, our first assessment serves as an important addition to the otherwise sparse literature on the bites of H. nasicus and extend it by 34 symptomatically positive reports.

Survey execution

A retrospective online survey of 23 questions was designed and distributed in three languages (English, German, and Spanish) via LimeSurvey (https://www.limesurvey.org/). Additional language selection based on the large herpetocultural community in Germany and the natural distribution of H. nasicus also in Mexico was carried out to increase the potential response rate. Thematic topics were (i) introductory question and personal information, (ii) questions about the snake and the bitten person, and (iii) questions about the details and nuances of the bite incident. It has been shared via personal contacts and social media, such as X/Twitter, Bluesky, Facebook, and Heterodon -related groups. It was available for 5 weeks, from 31 March 2025 until 2 May 2025. The question catalog and all survey info textboxes are in Supplementary Table S1. Answers were anonymously collected and evaluated. As participants were directly asked for the biological sex and not their gender identity, the evaluation will refer to the sex. Declaration of consent to participate in the study was mandatory to start the survey.

Survey evaluation

Once the survey ended (3 May 2025), answers were manually sorted, cleaned, and evaluated. Exclusion criteria were as follows: (1) not finished, (2) not meant seriously, (3) not Heterodon -related, and (4) multiple submitted/identical answers.

General evaluation

We conducted a retrospective online survey on snakebites caused by the Western Hognose snake, H. nasicus. Of the 91 submitted replies to the questionnaire, 63 have been rated as evaluable. The surveyed bites occurred across a 31-year period (1994 until 2025; median: 2023, mode: 2024), and 62/63 answers were self-reports. In 34 reports, at least one symptom was mentioned post-bite. Atypically for snakebite, women were overrepresented in our analysis with 25 male versus 34 female participants, with 4 not specifying their sex (Figure 1A). The victim’s age ranged from 11 to 65 years with a median of 29 years and a mean of 31.2 years (Figure 1B). All 63 incidents occurred with captive pet snakes of both sex (25 males, 29 females, and 7 unknown) and different ages from hatchlings to a 10-year-old individuum (Figures 1C, D).

Prevalence of symptoms, bite circumstances, and relevance of allergies

The incidents happened either during handling (39 reports) or during feeding (24 reports) the snakes. Three different bite types were reported in our questionnaire: (i) bite-and-release (snake bites quickly and goes off immediately; 38 reports), (ii) extended bites (snake bites and holds on to bite site for several seconds; 10 reports), and (iii) chewing (snake bites, holds on to the bite site and starts to chew; 15 reports) (Figure 1E). A positive correlation of bite intensity with likelihood of symptom onset was observed. Bite-and-release scenarios remain in 37% (14/38) without effects and resolved within 2 days. Extended bites and chewing led to higher occurrences of symptoms (both 80%) and resolved, on average, after 3 and 6 days, respectively (Figure 1F).

Most bites occurred when interacting with a hungry snake or while catching and transferring the animal into a feeding container. In 10 reports, direct skin contact with prey items [mouse (6×), quail egg (1×), toad (unspecified prey sp., 1×)] or other animals [chameleon (unspecified sp., 1×) and sand boa (Eryx sp., 1×)] before handling the snakes was reported. In six of these reports (chameleon, 3× mice, quail eggs, and the toad), the bites were with symptoms.

The medical history of the victims regarding previous snakebites (41 reports) was equal regarding developing no (21/41) or any symptoms (20/41) after an H. nasicus bite (Supplementary Table S2). Similarly, the presence of allergies (13 reports) showed no difference for the likelihood of developing symptoms (6/13).

The symptomatic spectrum of Western Hognose snake bites

A spectrum of 12 different symptoms was reported from the 34 symptomatic cases (Table 1). Directly after the snakebite, local bleeding (18%) and pain or a burning/itching sensation (59%) was reported. The pain was mostly localized and perceived as weak, comparable to a bee sting. However, irritating sensations (35%) were commonly perceived for several hours and often disseminated. Local edema was the most prevalent symptom after H. nasicus bites (79%) often in combination with impaired joint movement (21%). Edema developed either immediately (3×), quickly (within 2 h, 4×), or emerged within 3 h (5×).

General bite-related symptoms had an average resolution time of 3 to 4 days, ranging from a few hours (30%) up to 1 week (18%). Long-term sequelae were described in two reports. In report HN06, severe blistering across the whole arm for 3 weeks with following scabbing of the region (over several months) was reported, and in HN04, weakness in the bitten hand for over 1 year was reported.

Detailed envenomation reports

Of the 63 reported H. nasicus bites, seven patients (11%) went for professional medical help in response to the quickly developing and extensive edema, with four medication cases [antihistamine administration (2×), steroid administration (1×), and tetanus prophylaxis (1×)]. In 11 reports, self-medication was performed with antihistamines (9×), analgesics (4×), and furosemide (1×). In report HN15, the patient was under Claritin treatment prior to the bite but nevertheless developed extensive edema for 48 h. Four of the victims documented the case with pictures and provided detailed reports of the incidents.

Report HN02

On 2 June 2020, a 26-year-old woman (Cambridge, UK) was bitten by a captive H. nasicus (1 year old, female), while the patient was removing the snake from its enclosure. The snake snapped at the right thumb (Figures 2A–F) and started chewing. After a few minutes, the patient managed to get the snake to release the thumb, which showed immediate swelling and pain. Within 1 h, the swelling had spread across the hand and the patient attended the emergency room of a nearby hospital, where an intravenous injection of antihistamines was administered. The swelling resolved within 3 days and no long-term effects were reported. The patient had not been bitten by a snake previously.

Report HN03

On 23 May 2023, a 32-year-old woman (Gainesville, FL, USA) was bitten by a captive H. nasicus (1 year old, female) into the right index finger (Figures 2G, H). The patient had previously been bitten by several snakes (not specified) while working as a herpetologist. Previous bites led to no symptoms. The incident happened during feeding, when the snake grabbed the finger and started to chew. Directly after the bite, the finger showed signs of swelling and hyperthermia. The patient self-administered antihistamines and ibuprofen. As the swelling expanded to the hand after 3 h, the patient decided to seek medical care. Blood tests were run (no results submitted) and the swelling, heart rate, and blood pressure were monitored every 20 min for 6.5 h, but the patient did not receive further treatment. The swelling resolved after one and a half day and no long-term effects were reported.

Report HN15

On 30 September 2022, a 24-year-old woman (Miami, FL, USA) was bitten by a captive H. nasicus (25 cm, 2+ years old, male) into the left thumb (Figures 2I–N). The patient was previously bitten by numerous pet snakes (H. nasicus, Boidae, Pythonidae, and other Colubridae, like Boiga irregularis and Chrysopelea sp.) during private and professional handling with no resulting symptoms. The incident happened when the snake was removed from its enclosure for cleaning. The H. nasicus bit and chewed on the thumb for “between 30 seconds and a minute”. Directly after the bite, the patient “[ … ] felt a burning and itching sensation travel up my thumb all the way to my shoulder”. The pain increased up to “similar to a bee sting”. Within a few hours, the whole hand was swollen, turned red, felt “like how your arm or leg would feel if it fell asleep”, and the thumb was stiff. Five hours post bite, the burning and itching in the arm subsided, but the thumb and the back of the hand “felt tight, hot, and painful”. After 36 to 48 h, the swelling started to subside, but a feeling of “tightness” and pain persisted for 1 week. During the time of the incident, the patient was taking the following medication: antihistamines (for allergies), modafinil, omeprazole, sertraline, and a hormonal intrauterine device. No professional medical help was sought. No long-term effects were reported.

Report HN17

In March 2023, a 25-year-old man (Houston, TX, USA) was bitten by a captive H. nasicus (20–30 cm, unknown age, male) into the left hand (Figures 2O, P). The patient had previously been bitten by pet snakes (Nerodia rhombifer and Pantherophis sp.) with no resulting symptoms. The incident happened during a routine handling. The snake rubbed its snout against the hand, as if it were trying to burrow, then it bit between the index and middle finger and started to chew. Directly after the bite, the patient reported “stinging pain, followed by a very warm prickly sensation as swelling began”. Within the next 2 h, the swelling extended to the hand, and the patient felt that the hand was “hot, sore and achy, with particular discomfort in the joints”. After several hours, antihistamines were self-administered but had no effect. With cooling, the symptoms began to reside after approximately 36 h, but continued for approximately 4 days. No professional medical help was sought and no long-term effects were reported.

We carried out the first symptom-focused analysis of bite cases of H. nasicus via a retrospective community-based online questionnaire distributed among keepers and herpetologists. It should be noted that the retrospective, self-reporting nature of the study limits its scope, particularly since no professional medical reports or data were provided. This also assumes that bites with symptoms are more likely to be reported than “unimportant” incidents without consequences. Therefore, the actual dry bite (bites without venom administration) rate of H. nasicus is much higher than the 46% (29/63 without symptoms) observed here. For other venomous snakes, such as vipers and elapids, it is reported that 20%–50% of bites are “dry” (Pucca et al., 2020). However, the knowledge and expertise of the herpetocultural community should not be underestimated. Given that the snakes were kept as pets and that there are no other commonly kept species with which the iconic hognose could be confused, the identification can be considered accurate. The symptoms’ breadth, the abundance in which more intense cases are reported, and recovery times of several days exceed by far what is commonly expected from an H. nasicus bite. Rate and intensity of bite reaction was higher than expected. The observed symptoms are consistent with the suggested venom composition of H. nasicus. While svMP can lead to edema and pain, and can even cause blistering in rare cases, CRISPs are also known to promote inflammatory responses, leading finally to swelling, redness, and itching (Tadokoro et al., 2020; Mackessy, 2021).

While hypersensitivity/allergic reactions due to earlier snakebites are often raised concerns when NFFS bites are discussed, our data show that for H. nasicus, neither prior snakebites nor antihistaminic treatments affected the development of symptoms. Hence, the symptoms are based on a real envenomation by the Western Hognose (H. nasicus) toxins and not allergic reactions; antihistamines are not expected to be effective to treat snake envenomation in humans or other animals. The bite intensity is a major driver of symptom intensity. If an H. nasicus stayed attached to the bite site (extended bite) or even proceeds to chew, the percentage of patients with symptoms was 80% compared to 37% after strike only. This underlines the pivotal role of a holding/chewing movement for the effective transmission of venom, here directly shown for H. nasicus bites in humans. Regarding the age, younger H. nasicus (<2 years) caused, in 60% of the reports, more symptoms than older individuals (40%). This could be linked to differences in venom amount or composition, but could also be explained by the tendency of younger snakes to be more defensive/insecure during handling. Either way, ontogenetic venom variation is known to be an important element of snake venom plasticity, but understudied in NFFS (Senji et al., 2024; Lakušić et al., 2024; Mackessy and Saviola, 2016).

Handling or presenting food items with bare hands is a generally known reason for snakebites in pet care. A previous survey showed that 31% of H. nasicus keepers serve food with their bare hands (Zieliński, 2021), and also in the current survey, 16% of all bites followed skin contact with food items or other animals. In 50% of the cases, offering mice as well quail eggs and toads in some reports, bites caused edema and/or impaired joint movement, while the time to symptom resolution was not different in comparison to other bites. Even so, those numbers are too small for meaningful statistical analyses; they give a first indication that food item contact does not affect the general course of an H. nasicus bite. Considering that most bites are delivered to the hand and that symptom intensity is correlated to bite time exposure, it appears that virtually all H. nasicus envenoming can be prevented by proper handling equipment (e.g., leather gloves or snake hooks), quick removal of the snake after a bite, and by handling the snake particularly carefully during feeding (Zieliński, 2022; Foster et al., 2012; Wisconsin Herpetological Association, 2024). Therefore, H. nasicus is rated as between 2 and 3 on the hazard index with “usually mild-to-mildly moderate local effects and often related to protracted bites” with uncommon systemic envenoming, including no legal state regulations in any kind as a dangerous pet, but seen as a normal pet such as in the United States and Germany (Weinstein et al., 2022; Personal communication with international breeders and keepers, 2025). The development of a costly antivenom is therefore also far beyond what is necessary.

Although the H. nasicus is often acknowledged to be fully harmless, our retrospective survey indicates that the abundance and intensity of symptoms potentially caused by this snake exceeds what is commonly expected. While local pain and extensive edema are dominant, most cases progress into symptoms of several days’ resolution time. However, no sequelae are reported and no systemic envenomation has occurred. Therefore, albeit H. nasicus appears to be much more venomous to humans than previously reported, this species still should be considered relatively harmless as it is unable to cause permanent damage or fatalities. Most bite reports are linked to feeding context, and envenoming can be effectively prevented by careful handling with minor security equipment. In case of a bite, immediately removing the snake from the bite site reduces the chances of developing symptoms. From this perspective, there is no reason to initiate any legal regulations on this species due to its mild venom.