To the Editor:
Envenomation by widow spiders, Latrodectus sp, may affect various organs and systems, especially the muscles and the nervous system, and may result in a variety of clincal presentations. 1 -3 Bites by theriid spiders other than Latrodectus sp may cause a clinical syndrome that resembles latrodectism.4,5 To date, only a few cases of gastrointestinal (abdominal pain simulating an ileus) and myocardial involvement associated with Latrodectus envenomation have been reported. 1 -3 Herein we present a case of presumed Latrodectus envenoming that featured ileus and myocardial involvement.
A previously healthy, 22-year-old man was referred to our hospital from another facility approximately 12 to 16 hours after a suspected Latrodectus bite. He reported that he was sleeping in a tent at night when he felt a sensation of a needle stick on the outer third of the medial aspect of his right thigh, and, on checking his bed, saw a black spider. After 1 to 2 hours he developed severe thigh, abdominal, and back pain. The spider was not captured for identification. On admission to our center, the patient appeared toxic, with diaphoresis, tachypnea, tachycardia, anxiety, pallor, nausea, and vomiting, as well as severe thigh, abdominal, and back pain.
His vital signs were blood pressure 155/88 mm Hg, pulse 110 beats per minute, temperature 36.5°C, and respiratory rate 35 per minute with some fluctuation. Examination revealed an erythematous area of 0.5 × 0.5 cm on the outer third of the medial aspect of his right thigh. His abdomen was tender and distended with hypoactive bowel sounds. The rest of his examination was normal. An electrocardiogram (ECG) revealed sinus tachycardia associated with minimal nonspecific ST-T wave changes. Initial laboratory findings revealed white blood cell count 21 860/μL (reference range [r.r.] 4300–10 000/μL), glucose 236 mg/dL (r.r. 70–110 mg/dL), creatine kinase 548 U/L (r.r. 30–390 U/L), creatine kinase-MB 122 U/L (r.r. 0–24 U/L), lactate dehydrogenase 943 U/L (r.r. 220–450 U/L), myoglobin 74 ng/mL (r.r. 5–107 ng/mL), and troponin I 0.235 ng/mL (r.r. 0–1 ng/mL). Other biochemical values were within normal limits. There were air-fluid levels consistent with ileus on the direct upright abdominal radiograph. Abdominal ultrasound and transthoracic echocardiography revealed no pathology. Urine toxicology analysis was negative.
Due to the elevation of cardiac markers and ECG changes, a cardiology consultation was requested. General surgery was also consulted for the abdominal pain and the air-fluid levels on the radiograph. No other conditions that could have explained these findings were found. The working diagnosis was myocarditis and ileus occurring as a result of a Latrodectus spider bite, and the patient was admitted to the intensive care unit. The cardiology and surgery consultants suggested supportive treatment and follow-up. Crystalloids and antiemetics were administered for nausea and vomiting. Latrodectus antivenom was unavailable in our center and could not be provided. Therefore, fentanyl (100 μg intravenous boluses on 4 occasions) and diazepam (3 mg/h intravenous infusion) were administered for 48 hours. After this time, the cardiac markers normalized and the pain and ileus resolved, and the patient was discharged from the hospital without any complications.
Abdominal pain due to widow spider envenomation may closely mimic an acute abdomen. On occasion, misdiagnosis of such bites has led to unnecessary laparotomies, inadequate therapy, and unnecessary prolongation of pain. 6 Kleiner-Baumgarten reported 9 adults bitten by black widow spiders (Latrodectus sp) and requiring hospitalization from 1985 to 1988. Envenomation in these patients was mainly characterized by restlessness, profuse perspiration, severe abdominal pain, and muscular rigidity. In addition, in 2 cases, there was gastrointestinal involvement, with ileus and gastric dilatation. All of the victims recovered with symptomatic treatment. 3 In another reported case, the envenomation mimicked biliary colic and acute cholecystitis, and the patient underwent an emergency cholecystectomy. 6 In our case, the history of an apparent bite by “a black spider,” the pain in several muscle groups, and absence of peritoneal findings (excluding a surgical abdomen) led us to suspect likely Latrodectus envenoming.
Cardiovascular complications following Latrodectus envenomation have been reported in the medical literature. ECG abnormalities, which can be observed after Latrodectus envenomation, are variable and may include slurring of the QRS with ST- and T-segment depression, prolonged QT interval, brady/tachycardia, and atrial fibrillation. 1 -2,7 Myocardial involvement related to Latrodectus envenomation has been previously reported in 4 cases in the literature, 2 of which were from Turkey. One of the cases seen in Turkey (in the Southeast Anatolia region) involved myocarditis in a 65-year-old subject who had increased cardiac marker levels and ST elevations on the ECG. 1 The other case from Turkey (in the Aegean region) was a 22-year-old patient who had widespread ECG changes with myocardial ischemia and increased cardiac markers. 2 Both cases were treated symptomatically.1,2 To the best of our knowledge, the present case featuring ST-T segment changes and elevated cardiac markers is the third such Latrodectus envenoming to be reported in Turkey.
The exact mechanism of ileus and myocarditis after Latrodectus envenomation is unknown. However, α-latrotoxin found in Latrodectus venom was thought to be the reason for most of these clinical findings. 6 -8 The most active component of the venom, α-latrotoxin acts through a calcium-mediated mechanism leading to the release of predominantly acetylcholine and norepinephrine from nerve terminals. 9 Myocardial involvement could be due to catecholamine surge, direct toxic effect of α-latrotoxin, or a hypersensitivity reaction, as discussed previously.1,2 The release of acetylcholine at the neuromuscular junction induces frequent end-plate potentials causing muscle spasm and pain.6,8 The interaction of α-latrotoxin and the calcium channels may presumably cause ileus and abdominal pain through similar mechanisms.
The treatment of Latrodectus envenomation includes local wound care, opioids, and benzodiazepines for muscle spasm and pain, and antivenom. The most effective therapy for patients manifesting severe regional or systemic toxicity is Latrodectus antivenom.9,10 Antivenom was not available in our center, and is not manufactured in Turkey. Therefore, we had to rely on fentanyl, benzodiazepine, tetanus prophylaxis, fluid resuscitation, and other supportive treatment for our patient.
In the setting of presumed spider bite, individuals should be encouraged to bring the offending spider in for identification. Latrodectus envenomation should be suspected in victims with possible spider bite who develop ileus or myocardial involvement, and, in severe cases, an ECG and cardiac markers should be obtained, and a direct upright abdominal radiograph taken to evaluate for ileus.