INTRAVENOUS LIPID EMULSION TREATMENT REDUCES SYMPTOMS OF BREVETOXICOSIS IN TURTLES (TRACHEMYS SCRIPTA)

Emerging Insights into Brevetoxicosis in Sea Turtles

This review summarizes the current understanding of how brevetoxins, produced by Karenia brevis during harmful algal blooms, impact sea turtle health. Sea turtles may be exposed to brevetoxins through ingestion, inhalation, maternal transfer, and potentially absorption through the skin. Brevetoxins bind to voltage-gated sodium channels in the central nervous system, disrupting cellular function and inducing neurological symptoms in affected sea turtles. Moreover, the current evidence suggests a broader and longer-term impact on sea turtle health beyond what is seen during stranding events. Diagnosis relies on the detection of brevetoxins in tissues and plasma from stranded turtles. The current treatment of choice, intravenous lipid emulsion therapy, may rapidly reduce symptoms and brevetoxin concentrations, improving survival rates. Monitoring, prevention, and control strategies for harmful algal blooms are discussed. However, as the frequency and severity of blooms are expected to increase due to climate change and increased environmental pollution, continued research is needed to better understand the sublethal effects of brevetoxins on sea turtles and the impact on hatchlings, as well as the pharmacokinetic mechanisms underlying brevetoxicosis. Moreover, research into the optimization of treatments may help to protect endangered sea turtle populations in the face of this growing threat.

Intralipid Emulsion Therapy for the Treatment of Suspected Toxicity in 2 Avian Species

Intravenous lipid emulsion (ILE) therapy has shown promise as a treatment option for a variety of lipophilic toxins. Two birds presented for suspected ingestion of a toxic substance. A blue-and-gold macaw (Ara ararauna) presented after chewing a block of bromethalin rodenticide without overt clinical signs at the time of presentation. Additionally, a free-ranging bald eagle (Haliaeetus leucocephalus) was found weak and depressed near a municipal landfill after presumptive ingestion of pentobarbital. Both birds were treated with ILE therapy for potential intoxication without any adverse events. The macaw was clinically normal after 3 days of hospitalization and at a 1-week reevaluation. The eagle was transferred to a rehabilitation center after markedly improved mentation and strength and was released 7 days later. Clinicians should consider ILE therapy for the treatment of lipophilic toxicities; however, monitoring is recommended for persistent lipemia and other adverse effects that have been reported in the veterinary literature.

Successful treatment of ivermectin overdose in a bearded dragon (Pogona vitticeps) using gastric lavage and intravenous lipid emulsion

OBJECTIVE

To describe the clinical signs and outcome following ivermectin overdose in a bearded dragon. This case also describes the novel use of intravenous lipid emulsion (ILE) as a rescue therapy in reptiles, as well as the use of aggressive gastrointestinal decontamination.

CASE SUMMARY

A 4-year-old female intact bearded dragon (Pogona vitticeps) (0.6 kg) was admitted to the ICU at a specialty hospital following accidental overdose of 40 mg (66.7 mg/kg) of ivermectin enterally. The patient was physically inverted to allow passive reflux of the medication, then sedated for gastric lavage. A 20% ILE was administered intravenously due to the high risk for fatality. Additional treatments included 2 doses of activated charcoal, as well as SC fluids, enteral nutrition, and sucralfate. The patient was profoundly sedate until day 4 when mild improvements in mentation were noted. The patient started ambulating on its own on day 6 and was discharged from the hospital on day 13. The patient was alive 720 days postdischarge.

NEW OR UNIQUE INFORMATION PROVIDED

This is the first case report describing the events following ivermectin overdose and the use of ILE therapy and activated charcoal in a bearded dragon. These therapies were tolerated with no adverse effects noted in this patient. This report provides evidence that complete recovery from ivermectin overdose is possible.

Use of intravenous lipid emulsion therapy as a novel treatment for brevetoxicosis in sea turtles

The southwest coast of Florida experiences annual red tides, a type of harmful algal bloom that results from high concentrations of Karenia brevis. These dinoflagellates release lipophilic neurotoxins, known as brevetoxins, that bind to sodium channels and inhibit their inactivation, resulting in a variety of symptoms that can lead to mass sea turtle strandings. Traditional therapies for brevetoxicosis include standard and supportive care (SSC) and/or dehydration therapy; however, these treatments are slow-acting and often ineffective. Because red tide events occur annually in Florida, our objective was to test intravenous lipid emulsion (ILE) as a rapid treatment for brevetoxicosis in sea turtles and examine potential impacts on toxin clearance rates, symptom reduction, rehabilitation time, and survival rates. Sea turtles exhibiting neurological symptoms related to brevetoxicosis were brought to rehabilitation from 2018-2019. Upon admission, blood samples were collected, followed by immediate administration of 25 mg ILE/kg body mass (Intralipid® 20%) at 1 mL/min using infusion pumps. Blood samples were collected at numerous intervals post-ILE delivery and analyzed for brevetoxins using enzyme-linked immunosorbent assays. In total, nine (four subadults, one adult female, four adult males) loggerheads (Caretta caretta), five (four juvenile, one adult female) Kemp's ridleys (Lepidochelys kempii), and four juvenile green turtles (Chelonia mydas) were included in this study. We found that plasma brevetoxins declined faster compared to turtles that received only SSC. Additionally, survival rate of these patients was 94% (17/18), which is significantly higher than previous studies that used SSC and/or dehydration therapy (47%; 46/99). Nearly all symptoms were eliminated within 24-48 h, whereas using SSC, symptom elimination could take up to seven days or more. The dosage given here (25 mg/kg) was sufficient for turtles in this study, but the use of a higher dosage (50-100 mg/kg) for those animals experiencing severe symptoms may be considered. These types of fast-acting treatment plans are necessary for rehabilitation facilities that are already resource-limited. Intravenous lipid emulsion therapy has the potential to reduce rehabilitation time, save resources, and increase survival of sea turtles and other marine animals experiencing brevetoxicosis.

Heterogeneity and bias in animal models of lipid emulsion therapy: a systematic review and meta-analysis

INTRODUCTION

Clinicians utilize lipid emulsion to treat local anesthetic toxicity and non-local anesthetic toxicities, a practice supported by animal experimentation and clinical experience. Prior meta-analysis confirmed a mortality benefit of lipid emulsion in animal models of local anesthetic toxicity but the benefit of lipid emulsion in models of non-local anesthetic toxicity remains unanswered. Further, swine suffer an anaphylactoid reaction from lipid emulsions calling into question their role as a model system to study lipid, so we examined swine and non-swine dependent outcomes in models of intravenous lipid emulsion.

METHODS

We conducted a systematic review and meta-analysis examining the use of lipid emulsion therapy in animal models of cardiac toxicity. We quantified mortality using a random-effects odds-ratio method. Secondary outcomes included survival in the following subgroups: local-anesthetic systemic toxicity, non-local anesthetic toxicity, swine-based models, and non-swine models (e.g., rat, rabbit and dog). We assessed for heterogeneity with Cochran's Q and I². We examined bias with Egger's test & funnel plot analysis.

RESULTS

Of 2784 references screened, 58 met criteria for inclusion. Treatment with lipid emulsion reduced chance of death in all models of toxicity with an odds ratio of death of 0.26 (95% CI 0.16-0.44, Z-5.21, p < 0.00001, Cohen's-d = 0.72, n = 60). Secondary outcomes confirmed a reduced chance of death in models of local anesthetic toxicity (OR 0.16 {95% CI 0.1-0.33}) and non-local anesthetic toxicity (OR 0.43 {95% CI 0.22-0.83}). Heterogeneity (Cochran's Q 132 {df = 59, p < 0.01}, I ² = 0.55) arose primarily from animal-model and disappeared (I ² < = 0.12) when we analyzed swine and non-swine subgroups independently. Swine only benefited in models of local anesthetic toxicity (OR 0.28 {95% CI 0.11-0.7}, p = 0.0033) whereas non-swine models experienced a homogeneous benefit across all toxins (OR 0.1 {95% CI 0.06-0.16}, p < 0.00001). Egger's test identified risk of bias with outliers on funnel plot analysis.

DISCUSSION

Lipid emulsion therapy reduces mortality in animal models of toxicity. Heterogeneity arises from the animal-model used. Swine only benefit in models of local anesthetic toxicity, potentially due to lipid dose, experimental design or swine's anaphylactoid reaction to lipid. Outlier analysis reinforced the need for appropriate dosing of lipid emulsion along with airway management and chest compressions in the setting of cardiac arrest.

Immune function in Trachemys scripta following exposure to a predominant brevetoxin congener, PbTx-3, as a model for potential health impacts for sea turtles naturally exposed to brevetoxins

Many species of marine life in southwestern Florida, including sea turtles, are impacted by blooms of the toxic dinoflagellate, Karenia brevis. Sublethal exposure to toxins produced by K. brevis has been shown to impact sea turtle health. Since all sea turtles in the Gulf of Mexico have protected status, a freshwater turtle, Trachemys scripta, was used as a model for immune system effects following experimental exposure to a predominant brevetoxin congener in K. brevis blooms, PbTx-3. Exposure to PbTx-3 was oral or intratracheal and health effects were assessed using a suite of immune function parameters: innate immune function (phagocytosis, plasma lysozyme activity), adaptive immune function (lymphocyte proliferation), and measures of oxidative stress (superoxide dismutase (SOD) and glutathione-S-transferase (GST) activity in plasma). Inflammation was also measured using plasma protein electrophoresis. In addition, differential expression of genes in peripheral blood leukocytes was determined using suppression subtractive hybridization followed by real-time PCR of specific genes. The primary immune effects of sublethal brevetoxin exposure in T. scripta following PbTx-3 administration, appear to be an increase in oxidative stress, a decrease in lysozyme activity, and modulation of immune function through lymphocyte proliferation responses. Plasma protein electrophoresis showed a decreased A:G ratio which may indicate potential inflammation. Genes coding for oxidative stress, such as thioredoxin and GST, were upregulated in exposed animals. That sublethal brevetoxin exposures impact immune function components suggests potential health implications for sea turtles naturally exposed to toxins. Knowledge of physiological stressors induced by brevetoxins may contribute to the ultimate goal of developing directed treatment strategies in exposed animals for reduced mortality resulting from red tide toxin exposure in sea turtles.