Time factor in the detection of circulating whole venom and crotoxin and efficacy of antivenom therapy in patients envenomed by Crotalus durissus

Early-Onset Respiratory Muscle Paralysis in Crotalic Envenomation: A Case Study

Crotalic envenomation is responsible for approximately 8%-13% of ophidism cases in Brazil, yet it is associated with the highest mortality among snakes. We describe the case of a patient bitten by a rattlesnake who developed ventilatory muscle paralysis within hours after envenomation. While diaphragmatic paralysis is a rare late neurotoxic event following crotalic envenomation, in this case, paralysis occurred early but was rapidly reversed after antivenom administration. This report discusses potential contributing factors based on a comprehensive literature review.

A phase IV, prospective, observational study of the clinical safety of snake antivenoms

Snake envenoming is a neglected tropical disease that affects more than 2.7 million people worldwide. The treatment is based on the administration of antivenom composed of heterologous immunoglobulins, species-specific therapy involving the possibility of adverse reactions due to activation of the immune system. Considering the scarcity of prospective studies evaluating the safety of snake antivenoms, this study aimed to describe and characterize adverse events after antivenom infusion in an observational, prospective, single-centre investigation conducted in a referral centre in Brazil. A total of 47 victims of snake envenoming were included in the study, who were mostly men (75%), with ages ranging from 2 to 83 years. Twenty-two participants (47%) presented manifestations compatible with infusion-related reactions (IRRs) during or up to two hours after F(ab')2 heterologous immunoglobulin infusion. The most common clinical manifestation related to the infusion was a diffuse cutaneous rash (82%), followed by respiratory manifestations (46%) and facial swelling (23%). In four cases (9%), IRR were considered serious adverse events (SAE), characterized by haemodynamic instability, airway obstruction or hypoxia. Only one patient developed symptoms compatible with serum sickness. Although almost half of the patients treated with antivenom sera experienced IRRs, the SAE rate was 9%; in all cases, the adverse reaction was reversible by using supportive treatment, and there were no deaths. The results have shown that there is much to improve in the antivenom production process to obtain a more purified and specific product. Even so, a timely antivenom serum administration managed by well-trained health teams is safe and prevents complications after snake-related accidents.

Engineered protein containing crotoxin epitopes induces neutralizing antibodies in immunized rabbits

Crotoxin (Ctx) is the main lethal component of Crotalus durissus terrificus venom. It is a neurotoxin, composed of two subunits associated by noncovalent interactions, the non-toxic acid subunit (CA), named Crotapotin, and the basic subunit (CB), with phospholipase A₂ (PLA₂) activity. Employing the SPOT synthesis technique, we determined two epitopes located in the C-terminal of each Ctx subunit. In addition, 3 other epitopes were mapped in different regions of Ctx using subcutaneous spot implants surgically inserted in mice. All epitopes mapped here were expressed together as recombinant multi-epitopic protein (rMEPCtx), which was used to immunize New Zealand rabbits. Anti-rMEPCtx rabbit serum cross-reacted with Ctx and crude venoms from C. d. terrificus, Crotalus durissus ruruima, Peruvian C. durissus and Bothrops jararaca (with lower intensity). Furthermore, anti-rMEPCtx serum was able to neutralize Ctx lethal activity. As the recombinant multiepitopic protein is not toxic, it can be administered in larger doses without causing adverse effects on the immunized animals health. Therefore, our work evidences the identification of neutralizing epitopes of Ctx and support the use of recombinant multiepitopic proteins as an innovation to immunotherapeutics production.

Crotalus durissus terrificus (viperidae; crotalinae) envenomation: Respiratory failure and treatment with antivipmyn TRI® antivenom

We report an envenomation to a professional herpetologist by a South American rattlesnake (Crotalus durissus terrificus) that resulted in respiratory failure, and therapeutic improvement following antivenom administration. A 56-year-old male was bitten on the left wrist by a Crotalus durissus terrificus (C. d. terrificus) while attempting to tube the snake for maintaining safe control while performing venom extraction. The patient was intubated due to rapidly ensuing respiratory failure and administration of Antivipmyn-TRI^® was initiated while being transported via ambulance. The patient was admitted to the hospital unconscious and unresponsive. Mechanical ventilation was required until 5 h after completion of antivenom administration. No significant adverse effects were observed with antivenom administration. The patient was discharged approximately 55 h following envenomation. This is the first reported case in the United States of a patient following a C. d. terrificus envenomation with consequent respiratory failure, and in which Antivipmyn-TRI^® was successfully administered.

Coagulopathy as the main systemic manifestation after envenoming by a juvenile South American rattlesnake (Crotalus durissus terrificus): case report

CONTEXT

Rattlesnake bites in Brazil are generally caused by adult individuals, with most of the envenomed patients showing systemic manifestations that include varying degrees of neurotoxicity (acute myasthenia), rhabdomyolysis and coagulopathy, with only mild or no local manifestations. We report a case of envenoming by a juvenile South American rattlesnake (Crotalus durissus terrificus) that involved coagulopathy as the main systemic manifestation.

CASE DETAILS

A 19-year-old male was admitted to our Emergency Department with coagulopathy (incoagulable PT, APTT and INR), no remarkable local manifestations and no signs/symptoms of myasthenia or rhabdomyolysis (serum CK, LDH, ALT and AST within reference levels) 5 days after being bitten by a small snake that was described as a rattlesnake but was not brought for identification at admission. The patient had already been treated in another Emergency Department with i.v. bothropic antivenom (AV) 1 h and 4 days post-bite. Based on the possibility of an unusual rattlesnake bite, crotalic AV was administered i.v., which improved the coagulation (9 h post-CroAV, INR = 2.11; 36 h post-CroAV, INR = 1.42). During hospitalization, relatives brought the snake that caused the bite, which was identified as a 38-cm long C. d. terrificus.

DISCUSSION

Little is known about the clinical manifestations after bites by juvenile C. d. terrificus. This case shows that systemic envenoming by juvenile C. d. terrificus may result in coagulopathy as the main systemic manifestation, without neuromyotoxic features normally associated with bites by adult specimens. Despite the delayed administration, crotalic AV was effective in improving the blood coagulation.

Acute renal failure after Crotalus durissus snakebite: a prospective survey on 100 patients

BACKGROUND

Acute renal failure (ARF) is the main cause of death after the South American crotalid snakebite. The aim of this study was to assess the prevalence, risk factors, and characteristics of Crotalus durissus venom-induced ARF.

METHODS

One hundred cases of Crotalus durissus bite were studied from hospitalization to discharge or death. Creatinine clearance (GFR) <60 mL/min/1.73 m(2) in the first 72 hours after snakebite was defined as ARF. Data are expressed as median (range of variation) or%, and were analyzed by univariate analysis and logistic regression.

RESULTS

Twenty-nine patients developed ARF. Of those, 24% required dialysis and 10% died. ARF patients had smaller body surface [1.55 (0.6-2.3) vs. 1.7 (0.6-2.1) m(2), P= 0.0097], received antivenom (AV) later [12 (2-48) vs. 2 (1-14) hours, P < 0.0001], received more AV [190 (90-536) vs. 158 (75-500) mg/m(2), P < 0.0001], presented lower diuresis at admission [62 (0-182) mL/hr vs. 100 (25-325) mL/hr, P= 0.0004], and showed a striking creatine kinase (CK) increase [50,250 (69-424,120) vs. 1108 (88-133,170) U/L, P < 0.0001]. Age <12 years (OR 5.6, P= 0.026), time for AV >2 hours (OR 11.1, P= 0.032), CK at admission >2000 U/L (OR 12.7, P= 0.0009) were identified as independent risk factors for ARF, whereas diuresis at admission >90 mL/hr (OR 0.20, P= 0.014) was an independent protector factor.

CONCLUSION

C. durissus venom-induced ARF had high prevalence (29%). Delay for AV treatment, CK at admission >2000 U/L, and age <12 years were independent risk factors for ARF development. Diuresis at admission >90 mL/hr was a protective factor.

Pharmacokinetic-pharmacodynamic relationships of immunoglobulin therapy for envenomation

Parenteral administration of horse- and sheep-derived antivenoms constitutes the cornerstone in the therapy of envenomations induced by animal bites and stings. Depending on the type of neutralising molecule, antivenoms are made of: (i) whole IgG molecules (150 kDa), (ii) F(ab')(2) immunoglobulin fragments (100 kDa) or (iii) Fab immunoglobulin fragments (50 kDa). Because of their variable molecular mass, these three types of antivenoms have different pharmacokinetic profiles. Fab fragments have the largest volume of distribution and readily reach extravascular compartments. They are catabolised mainly by the kidney, having a more rapid clearance than F(ab')(2) fragments and IgG. On the other hand, IgG molecules have a lower volume of distribution and a longer elimination half-life, showing the highest cycling through the interstitial spaces in the body. IgG elimination occurs mainly by extrarenal mechanisms. F(ab')(2) fragments display a pharmacokinetic profile intermediate between those of Fab fragments and IgG molecules. Such diverse pharmacokinetic properties have implications for the pharmacodynamics of these immunobiologicals, since a pronounced mismatch has been described between the pharmacokinetics of venoms and antivenoms. Some venoms, such as those of scorpions and elapid snakes, are rich in low-molecular-mass neurotoxins of high diffusibility and large volume of distribution that reach their tissue targets rapidly after injection. In contrast, venoms rich in high-molecular-mass toxins, such as those of viperid snakes, have a pharmacokinetic profile characterised by a rapid initial absorption followed by a slow absorption process from the site of venom injection. Such delayed absorption has been linked with recurrence of envenomation when antibody levels in blood decrease. This heterogeneity in pharmacokinetics and mechanism of action of venom components requires a detailed analysis of each venom-antivenom system in order to determine the most appropriate type of neutralising molecule for each particular venom. Besides having a high affinity for toxicologically relevant venom components, an ideal antivenom should possess a volume of distribution as similar as possible to that of the toxins being neutralised. Moreover, high levels of neutralising antibodies should remain in blood for a relatively prolonged time to assure neutralisation of toxins reaching the bloodstream later in the course of envenomation, and to promote redistribution of toxins from extravascular compartments to blood. Additional studies are required on different venoms and antivenoms in order to further understand the pharmacokinetic-pharmacodynamic relationships of antibodies and their fragments and to optimise the immunotherapy of envenomations.

Envenoming by Bothrops jararaca in Brazil: association between venom antigenaemia and severity at admission to hospital

The association between the clinical severity of Bothrops jararaca envenoming at admission and serum venom and plasma fibrinogen concentrations before antivenom administration is reported in 137 patients admitted to Hospital Vital Brazil, Instituto Butantan, São Paulo, Brazil, between 1989 and 1990. Other variables such as age, gender, site of the bite, use of tourniquet and the time interval between the bite and start of antivenom therapy, spontaneous systemic bleeding, and the 20 minute whole blood clotting test (20WBCT) at admission showed no association with either severity or serum venom antigen concentration (SVAC). Mean SVAC in patients with mild envenoming was significantly lower than in the group with moderate envenoming (P = 0.0007). Patients with plasma fibrinogen concentrations > 1.5 g/L had a lower mean SVAC than patients with plasma fibrinogen concentrations < or = 1.5 g/L (P = 0.02). Those admitted with a tourniquet in place had significantly higher plasma fibrinogen concentrations than those without a tourniquet (P = 0.002). A multiple logistic regression model showed independent risk factors for severity: bites at sites other than legs or forearms, SVACs > or = 400 ng/mL, and the use of a tourniquet. Rapid quantification of SVAC before antivenom therapy might improve initial evaluation of severity in B. jararaca bites.

A new avidin-biotin optical immunoassay for the detection of beta-bungarotoxin and application in diagnosis of experimental snake envenomation

A highly sensitive avidin-biotin optical immunoassay (AB-OIA) has been developed for the detection of beta-bungarotoxin (beta-BuTx), a neurotoxin from the venom of Bungarus multicinctus, in whole blood, plasma, and urine. Affinity purified rabbit IgG anti-beta-BuTx antibody was immobilized on an optically active silicon surface (SILIAS wafer). The test sample was incubated and the antigen-antibody reaction was monitored by the addition of a biotinylated monoclonal antibody (mAb 15) specific to the toxin, avidin-horseradish peroxidase (HRP) and tetramethylbenzidine substrate. The silicon assay surface technology enables us to directly visualize a physical change in the optical thickness of the antibody thin film. The change in thickness is due to the specific capture of the toxin on the surface and when the substrate is added, the binding event is amplified, which then alters the reflected light path and a change in colour is visualized. The assay could detect beta-BuTx levels as low as 16 pg/ml in sample buffer and 100 pg/ml in whole blood or plasma. The AB-OIA is simple, requires only 40 microl of biological fluid and can be performed without specialized equipment. The efficacy of the test for detection of beta-BuTx in blood or plasma obtained from mice during experimental envenomation with B. multicinctus venom was demonstrated. The AB-OIA was also used to quantitate the postmortem level of beta-BuTx in various organs such as brain, liver, and kidney, as well as the tissue at the site of injection. Development of a simple, rapid snake toxin detection kit based on AB-OIA technique potentially applicable in the clinics as well as in the field is discussed.

Neutralizing capacity of antisera raised in horses and rabbits against Crotalus durissus terrificus (South American rattlesnake) venom and its main toxin, crotoxin

Crotalus durissus terrificus (South American rattlesnake) venom possesses myotoxic and neurotoxic activities, both of which are also expressed by crotoxin, the principal toxin of this venom. We have investigated the ability of commercial equine antivenom and antivenoms raised in rabbits against C. d. terrificus venom and crotoxin to neutralize the physiological and morphological changes induced by this venom and crotoxin in electrically-stimulated phrenic nerve-diaphragm (PND) and extensor digitorum longus (EDL) preparations of mice. The time required to produce 50% neuromuscular blockade in the PND and EDL preparations was, respectively, 103+/-9 and 59+/-6 min for C. d. terrificus venom (10 microg/ml) and 75+/-9 and 110+/-7 min for crotoxin (10 microg/ml). The antivenoms dose-dependently inhibited this neuromuscular activity of the venom and crotoxin. At a venom:antivenom ratio of 1:3, the rabbit antivenoms were as effective as the commercial equine antivenom. The creatine kinase (CK) concentrations in the organ bath containing EDL muscle were 290 and 1020 U/l following a 120 min exposure to C. d. terrificus venom and crotoxin, respectively. All of the antivenoms neutralized the release of CK by crotoxin, but were ineffective against C. d. terrificus venom. Histological analysis of the two preparations showed that rabbit anticrotoxin antivenom protected against the myotoxic action of C. d. terrificus venom and crotoxin better than the other antivenoms. We conclude that antisera raised in rabbits are better than equine antiserum in neutralizing the neurotoxic and myotoxic activities of C. d. terrificus venom and crotoxin.

Tests for detection of snake venoms, toxins and venom antibodies: review on recent trends (1987-1997)

Various methods developed for the detection of snake venoms, toxins and venom antibodies, during the last decade is reviewed. Radioimmunoassay, agglutination assay, enzyme-linked immunosorbent assay (ELISA), fluorescence immunoassay etc. have been used for detection of venoms and toxins. Important contributions have been made to improve the specificity, sensitivity, rapidity and simplicity of the ELISA method. Monoclonal antibodies and affinity-purified venom-specific antibodies were used to achieve species specificity of ELISA and the latter seems to be the ideal for venom detection. Incorporation of avidin-biotin system as well as the fluorogenic substrate in the enzyme immunoassay sufficiently increased the sensitivity of the assay to detect venom concentrations to picogram levels. The ability to use undiluted blood and other whole biological fluids reduce the assay time considerably. Although there have been several reports were on venom detection, so far only a few field kits have been developed. This implies that the experiments and design were only at the laboratory levels and still more work has to be carried out before it could be used in the field. Concerning the venom antibody detection, ELISA has been used extensively and the humoral response of patients envenomed by snake has been investigated in detail. Non-specific reactivity along with cross-reactivity still limits the use of ELISA for species identification in epidemiological studies. Overall, ELISA remains the suitable method for the detection of snake venoms, toxins and venom antibodies in body fluids. The possible use of a biosensor approach to solve some of the problems associated with the ELISA method are also discussed.

South American rattlesnake bite (Crotalus durissus SP) without envenoming: insights on diagnosis and treatment

A South American rattlesnake bite without clinical manifestations of envenoming (termed 'dry-bite') has not been recognized to occur by the Brazilian Ministry of Health, which recommends the administration of antivenom to all bitten patients. During 36 months of an observational study on South American rattlesnake bites in Minas Gerais, Brazil, 12% of 41 patients with fang marks at the bite-site did not present clinical or laboratory features of envenoming and had no plasma venom detected before specific serotherapy, fulfilling the criteria for the diagnosis of true 'dry-bite'. Data from these preliminary observations suggest that these patients should be correctly diagnosed since they should not be treated with unnecessary and sometimes hazardous and expensive serotherapy.

Treating the snakebitten child in North America: a study of pit viper bites

BACKGROUND/PURPOSE

Snakebite envenomation is a potentially life-threatening form of trauma, the dangers of which are amplified in children because their smaller size increases the relative dose of venom received. The authors reviewed a large series of snakebitten children to address the medical and fiscal issues of treating these patients.

METHODS

The records of 37 snakebitten children (1987 through 1997) were analyzed for demographic data, signs of envenomation, use of specific therapies (antivenin, blood products, or surgery), length of hospitalization, complications, and cost of care.

RESULTS

Fifty-four percent of the children had a major envenomation demonstrated by systemic symptomatology, laboratory analysis, or need for surgery. All children made full recoveries with most receiving only supportive care (92%). The average time to emergency department presentation was 8 hours, where all children with major envenomations and those requiring specific therapies (surgery, clotting factors) were identified. Cost analysis showed an average of $2,450 dollars per child with the majority of expenses attributable to length of hospitalization.

CONCLUSIONS

Most snakebitten children completely recover with minimal supportive care, and they can be cared for safely and cost effectively as outpatients if no signs of major envenomation are noted within 8 hours of the bite.