Successful management of ivermectin-induced blindness in an African lion (Panthera leo) by intravenous administration of a lipid emulsion

Potential of Streptomyces avermitilis: A Review on Avermectin Production and Its Biocidal Effect

Secondary metabolites produced by the fermentation of Streptomyces avermitilis bacterium are powerful antiparasitic agents used in animal health, agriculture and human infection treatments. Avermectin is a macrocyclic lactone with four structural components (A1, A2, B1, B2), each of them containing a major and a minor subcomponent, out of which avermectin B1a is the most effective parasitic control compound. Avermectin B1a produces two homologue avermectins (B1 and B2) that have been used in agriculture as pesticides and antiparasitic agents, since 1985. It has a great affinity with the Cl-channels of the glutamate receptor, allowing the constant flow of Cl- ions into the nerve cells, causing a phenomenon of hyperpolarization causing death by flaccid paralysis. The purpose of this work was to gather information on the production of avermectins and their biocidal effects, with special emphasis on their role in the control of pests and phytopathogenic diseases. The literature showed that S. avermitilis is an important producer of macrocyclic lactones with biocidal properties. In addition, avermectin contributes to the control of ectoparasites and endoparasites in human health care, veterinary medicine and agriculture. Importantly, avermectin is a compound that is harmless to the host (no side effects), non-target organisms and the environment.

The effect of intravenous lipid emulsion (ILE) on the pharmacokinetic/toxicokinetic dispositions of ivermectin and carprofen in rabbits

Intravenous lipid emulsion (ILE) has been widely used as an effective antidote in both veterinary and human medicine for the treatment of acute intoxications caused by drugs and pesticides with high lipid solubility. This study was conducted to investigate the effect of ILE co-administration on the kinetic dispositions of ivermectin (IVM) and carprofen (CRP) following intravenous bolus administration at subtoxic doses in rabbits.Twenty-four male New Zealand rabbits weighing 2.78 ± 0.2 kg were used in this study. Rabbits were divided into four groups (Group 1: IVM and Group 2: IVM + ILE or Group 3: CRP and Group 4: CRP + ILE), each group consisting of 6 animals. In the IVM study, Group 1 received IVM (0.6 mg/kg) alone while Group 2 received IVM (0.6 mg/kg) and ILE (2.5 ml/kg). In the CRP study, Group 3 received CRP (12 mg/kg) alone while Group 4 received CRP (12 mg/kg) and ILE (2.5 ml/kg). In both drug groups, ILE was administered 3 times as an i.v. bolus at the 10th min and repeated 4th and 8th h after the drug administration. Blood samples were collected from the auricular vein at various times after drug administration. The drug concentrations in plasma samples were determined by high-pressure liquid chromatography. Kinetic parameters were calculated using a non-compartmental model for both CRP and IVM.The C0 and area under the concentration-time curve from zero up to ∞ (AUC0-∞) values were significantly greater with ILE co-administration (2136 ng/ml and 360.84 ng.d/ml) compared to the IVM alone (1340.63 ng/ml and 206 ng.d/ml), respectively. Moreover, the volume of distribution (Vdss) and clearance (Cl) of IVM were reduced by approximately 42% and 46% with ILE co-administration compared to IVM alone resulting in a reduction of the distribution and slower elimination, respectively. Similar differences in C0, and Vdss values were also observed in CRP with ILE co-administration compared to CRP alone. ILE co-administration changed significantly the kinetic profile of both IVM and CRP in rabbits, supporting the lipid sink theory in which highly lipid-soluble compounds are absorbed into the lipid phase of plasma from peripheral organs such as the heart and brain affected by the acute toxicity of the compounds.

First report of Thelazia callipaeda Railliet & Henry, 1910 in a zoo lion (Panthera leo) (Linnaeus, 1758) from Romania

Thelazia callipaeda, the zoonotic "oriental eye worm", is an emerging nematode known to infect a wide range of hosts, particularly carnivores (wild and domestic canids and felids, mustelids, and ursids), but also other mammal groups (suids, lagomorphs, monkeys, and humans), across a wide geographical area. New host-parasite associations and human cases have mostly been reported in endemic areas. A less studied group of hosts is represented by zoo animals that may harbor T. callipaeda.A 23-year old male lion (Panthera leo) that was born in a public zoo in Reșița (Caraș-Severin County, Romania) was submitted to the University of Agricultural Sciences and Veterinary Medicine of Cluj-Napoca for investigations after death from unknown reasons in November 2022. Four nematodes were collected from the right eye during the necropsy and submitted to morphological and molecular characterization.Collected nematodes were morphologically identified as three females and one male T. callipaeda. The BLAST analysis revealed 100% nucleotide identity to numerous isolates of T. callipaeda haplotype 1.The present paper presents a new host-parasite association between T. callipaeda and P. leo from a zoo in Romania.

Canine Distemper Virus in Tigers (Panthera tigris) and Leopards (P. pardus) in Nepal

From wild dogs (Lycaon pictus) in the Serengeti to tigers (Panthera tigris altaica) in the Russian Far East, canine distemper virus (CDV) has been repeatedly identified as a threat to wild carnivores. Between 2020 and 2022, six Indian leopards (P. pardus fusca) presented to Nepali authorities with fatal neurological disease, consistent with CDV. Here, we report the findings of a serosurvey of wild felids from Nepal. A total of 48 serum samples were tested, comprising 28 Bengal tigers (P. t. tigris) and 20 Indian leopards. Neutralizing antibodies were identified in three tigers and six leopards, equating to seroprevalences of 11% (CI: 2.8-29.3%, n = 28) and 30% (CI: 12.8-54.3%, n = 20), respectively. More than one-third of seropositive animals were symptomatic, and three died within a week of being sampled. The predation of domestic dogs (Canis lupus familiaris) has been posited as a potential route of infection. A comparison of existing diet studies revealed that while leopards in Nepal frequently predate on dogs, tigers do not, potentially supporting this hypothesis. However, further work, including molecular analyses, would be needed to confirm this.

The use of intralipid emulsion therapy to treat status epilepticus in a guinea pig (Cavia porcellus) secondary to severe ivermectin toxicity

OBJECTIVE

To describe the successful management of ivermectin-induced status epilepticus in a guinea pig (Cavia porcellus) with intravenous lipid emulsion (ILE) therapy.

CASE SUMMARY

A 5-week-old, female intact guinea pig was presented to an emergency hospital for status epilepticus 24 hours after oral administration of ivermectin. Approximately 48 hours after exposure, ILE therapy was administered. Within 12-16 hours after ILE therapy, seizures had stopped and the patient's mentation returned to normal. The definitive diagnosis was based on owner history, clinical presentation, and American Society for the Prevention of Cruelty to Animals poison control guidelines.

NEW OR UNIQUE INFORMATION PROVIDED

The use of intralipid therapy has been widely documented as a treatment option for numerous toxicities. Its efficacy in treatment for toxicities in both veterinary and human medicines has been well described in various case reports and studies. However, its use and success in small mammals have yet to be documented. In this case report, intralipid therapy is used to successfully treat a seizuring guinea pig that was administered a severely toxic dose of ivermectin. To the authors' knowledge, this is the first report on the successful use of intralipids in a guinea pig from ivermectin toxicosis.

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.

Successful management of a kitten with chlorpyrifos and cypermethrin toxicosis with pralidoxime and atropine

CASE SUMMARY

Organophosphates and pyrethroids have been widely used as agricultural and domestic insecticides. This case report describes a 3-month-old free-roaming female kitten, weighing 930 g, that developed hypersalivation, hypothermia, dyspnoea due to increased bronchial secretion, bradycardia, miosis and neurological signs, including restlessness, ataxia, disorientation, apparent hallucination, muscle twitching and seizures within 6 h of accidental ingestion of an insecticide containing chlorpyrifos (500 g/l) and cypermethrin (50 g/l). The kitten was treated empirically with intramuscular atropine and dexamethasone, and rectal diazepam. The history of insecticide exposure was obtained after 6 h of treatment and intramuscular 2-pyridine aldoxime methochloride (pralidoxime [2-PAM]) and atropine therapy was started 2 h later. Recovery was complicated by suspected aspiration, but there were no sequelae from the insecticide exposure and by 7 days post-ingestion the kitten was normal and playful.

RELEVANCE AND NOVEL INFORMATION

To the best of our knowledge, this is the first report of successful management of chlorpyrifos and cypermethrin toxicosis in a cat in Bangladesh. This case report suggests that 2-PAM followed by atropine and other supportive therapy may be an effective strategy to manage a cat poisoned by chlorpyrifos and cypermethrin; however, expanded clinical trials are needed.

Prevalence and type of ocular disease in a population of aged captive nondomestic felids

OBJECTIVES

Report of prevalence and type of ocular disease in a captive population of nondomestic felids.

METHODS

Medical records of 202 cats from 1993 to 2018 were reviewed. Species, age at diagnosis, sex, ocular examination abnormalities, systemic/physical examination abnormalities, type of examination (visual, sedated, or anesthetized), ocular structures affected, other diagnostics, therapy, and resolution of ocular disease were recorded.

RESULTS

A total of 202 nondomestic felids including 18 different species (bobcat, caracal, cougar, Fishing cat, Geoffroy's cat, jaguar, jungle cat, leopard, leopard cat, liger, lion, lynx, ocelot, Sand cat, Savannah cat, serval, snow leopard, and tiger) from a rescue facility were evaluated. Forty-six ocular lesions were diagnosed in 33 (16.3%) cats from 8 different species (bobcat, caracal, cougar, leopard, lion, ocelot, serval, and tiger) with a mean age of 16 ± 5.9 years at time of diagnosis. Ocular lesions included corneal disease (37%) (ulcerations, perforations, keratitis, corneal scars), cataracts (23.9%), hyphema (8.7%), lens luxation (6.5%), retinal detachment (6.5%), uveitis (4.3%), conjunctival disease (4.3%), retinal degeneration (2.1%), glaucoma (2.1%), and optic neuritis (2.1%). Therapies included medical (topical antibiotics, anti-inflammatories, serum, etc.) and/or surgical management (enucleation, intracapsular lens extraction, corneoconjunctival transposition, and corneal burr debridement).

CONCLUSIONS

To the authors' knowledge, this is the first report of the prevalence of ocular disease in a population of captive nondomestic felids. It is difficult to diagnose and treat ocular disease in nondomestic cats due to challenges related to handling, diagnostics, and therapeutics in nondomestic species. Ocular disease seen in this population is similar to that found in domestic cat populations.

African Lions and Zoonotic Diseases: Implications for Commercial Lion Farms in South Africa

Simple Summary

In South Africa, thousands of African lions are bred on farms for commercial purposes, such as tourism, trophy hunting, and traditional medicine. Lions on farms often have direct contact with people, such as farm workers and tourists. Such close contact between wild animals and humans creates opportunities for the spread of zoonotic diseases (diseases that can be passed between animals and people). To help understand the health risks associated with lion farms, our study compiled a list of pathogens (bacteria, viruses, parasites, and fungi) known to affect African lions. We reviewed 148 scientific papers and identified a total of 63 pathogens recorded in both wild and captive lions, most of which were parasites (35, 56%), followed by viruses (17, 27%) and bacteria (11, 17%). This included pathogens that can be passed from lions to other animals and to humans. We also found a total of 83 diseases and clinical symptoms associated with these pathogens. Given that pathogens and their associated infectious diseases can cause harm to both animals and public health, we recommend that the lion farming industry in South Africa takes action to prevent and manage potential disease outbreaks.

Abstract

African lions (Panthera leo) are bred in captivity on commercial farms across South Africa and often have close contact with farm staff, tourists, and other industry workers. As transmission of zoonotic diseases occurs through close proximity between wildlife and humans, these commercial captive breeding operations pose a potential risk to thousands of captive lions and to public health. An understanding of pathogens known to affect lions is needed to effectively assess the risk of disease emergence and transmission within the industry. Here, we conduct a systematic search of the academic literature, identifying 148 peer-reviewed studies, to summarize the range of pathogens and parasites known to affect African lions. A total of 63 pathogenic organisms were recorded, belonging to 35 genera across 30 taxonomic families. Over half were parasites (35, 56%), followed by viruses (17, 27%) and bacteria (11, 17%). A number of novel pathogens representing unidentified and undescribed species were also reported. Among the pathogenic inventory are species that can be transmitted from lions to other species, including humans. In addition, 83 clinical symptoms and diseases associated with these pathogens were identified. Given the risks posed by infectious diseases, this research highlights the potential public health risks associated with the captive breeding industry. We recommend that relevant authorities take imminent action to help prevent and manage the risks posed by zoonotic pathogens on lion farms.

SUSPECTED MOXIDECTIN TOXICOSIS IN A ROAN ANTELOPE (HIPPOTRAGUS EQUINUS), A SABLE ANTELOPE (HIPPOTRAGUS NIGER), AND AN ARABIAN ORYX (ORYX LEUCORYX) AT A SEMI-FREE RANGE ZOOLOGICAL PARK

Moxidectin is a commonly used lipophilic anthelmintic with activity against a wide range of nematodes. It is labeled for use in cattle by oral, topical, and subcutaneous routes. In semi-free ranging conditions, many anthelmintics are remotely administered intramuscularly due to an inability to administer by other routes without restraint. During 2015-2016, three animals including a roan (Hippotragus equinus), sable (Hippotragus niger), and Arabian oryx (Oryx leucoryx) treated with moxidectin developed clinical signs consistent with toxicosis. The primary sign was severe neurologic depression within 12 to 24 hr. Based on recommendations in domestic cases, animals were treated with intravenous lipid therapy and supportive care while diagnostic testing was performed. All three initially improved prior to succumbing to secondary problems associated with prolonged recumbency. Moxidectin has been administered remotely on 97 occasions in eight different exotic ruminant species at Fossil Rim, with only the above three cases showing clinical signs of toxicosis. Two potential causes in these cases include poor body condition leading to a smaller volume of distribution, thus allowing higher concentrations to overwhelm the blood-brain barrier, or a genetic defect similar to some herding dog breeds. Given that cases were seen in three different species at an overall low incidence within a given species, a genetic defect is considered unlikely. The animals affected did have significantly lower body condition score than conspecifics, and it is considered likely that this predisposed these animals to toxicosis. Therefore, caution should be used when administering moxidectin intramuscularly in animals in poor body condition.

Intravenous Lipid Emulsions in Veterinary Clinical Toxicology

Use of intravenous lipid emulsion (ILE) as an antidote for severe cardiotoxicity and neurotoxicity has expanded in the veterinary world in the past decade. Despite advances in understanding of potential mechanisms of action of antidotal ILE, knowledge gaps remain in efficacy, appropriate dosing rates for various toxicants, and potential adverse reactions. Use of ILE in management of toxicoses of veterinary patients should be considered investigational, and should not be first-line treatment of most toxicoses, especially where established treatment protocols have good likelihood of positive outcomes. Use of ILE in veterinary toxicology cases requires judicious assessment of individual cases and proper informed consent of clients.

Lipid Therapy for Intoxications

This review discusses the use of intravenous lipid emulsion (ILE) in the treatment of intoxications with lipophilic agents in veterinary medicine. Despite growing scientific evidence that ILE has merit in the treatment of certain poisonings, there is still uncertainty on the optimal composition of the lipid emulsion, the dosing, the mechanism of action, and the efficacy. Therefore, a critical view of the clinician on the applicability of this modality in intoxications is still warranted. The use of ILE therapy is advocated as an antidote in cases of intoxications with some lipophilic substances.

Electroretinographic changes after intravenous lipid emulsion therapy in a dog and a foal with ivermectin toxicosis

This case report describes ivermectin-induced blindness in a dog and a foal with normal ophthalmic fundic examinations and attenuated electroretinography (ERG). Subsequent recovery in ERG was noted following intravenous lipid emulsion (ILE) therapy. A dog and a foal were evaluated for ivermectin-induced blindness. Clinical signs included dull mentation, absent pupillary light reflexes (PLRs), and absent menace on presentation. The animals had normal fundoscopic examinations; however, in both cases ERG was consistent with neurosensory retinal dysfunction. Following ILE therapy for ivermectin toxicosis, return of menace, PLRs, and normal mentation were noted, as was improvement in ERG and serum ivermectin levels. These are the first documented cases of ivermectin-induced blindness in a dog and a foal with normal fundic examinations and attenuated ERG. ERG improved in both animals after ILE therapy. ERG may assist in the diagnosis of ivermectin toxicosis in dogs and horses. ILE therapy may hasten recovery in treatment of ivermectin-induced blindness.