Diagnosis and management of Baylisascaris procyonis infection in an infant with nonfatal meningoencephalitis

Safety, pharmacokinetics, and potential neurological interactions of ivermectin, tafenoquine, and chloroquine in Rhesus macaques

Ivermectin (IVM) could be used for malaria control as treated individuals are lethal to blood-feeding Anopheles, resulting in reduced transmission. Tafenoquine (TQ) is used to clear the liver reservoir of Plasmodium vivax and as a prophylactic treatment in high-risk populations. It has been suggested to use ivermectin and tafenoquine in combination, but the safety of these drugs in combination has not been evaluated. Early derivatives of 8-aminoquinolones (8-AQ) were neurotoxic, and ivermectin is an inhibitor of the P-glycoprotein (P-gp) blood brain barrier (BBB) transporter. Thus, there is concern that co-administration of these drugs could be neurotoxic. This study aimed to evaluate the safety and pharmacokinetic interaction of tafenoquine, ivermectin, and chloroquine (CQ) in Rhesus macaques. No clinical, biochemistry, or hematological outcomes of concern were observed. The Cambridge Neuropsychological Test Automated Battery (CANTAB) was employed to assess potential neurological deficits following drug administration. Some impairment was observed with tafenoquine alone and in the same monkeys with subsequent co-administrations. Co-administration of chloroquine and tafenoquine resulted in increased plasma exposure to tafenoquine. Urine concentrations of the 5,6 orthoquinone TQ metabolite were increased with co-administration of tafenoquine and ivermectin. There was an increase in ivermectin plasma exposure when co-administered with chloroquine. No interaction of tafenoquine on ivermectin was observed in vitro. Chloroquine and trace levels of ivermectin, but not tafenoquine, were observed in the cerebrospinal fluid. The 3''-O-demethyl ivermectin metabolite was observed in macaque plasma but not in urine or cerebrospinal fluid. Overall, the combination of ivermectin, tafenoquine, and chloroquine did not have clinical, neurological, or pharmacological interactions of concern in macaques; therefore, this combination could be considered for evaluation in human trials.

Clinical Reasoning: A 12-Month-Old Male Child With Staring Episodes, Ataxia, and Right-sided Weakness

Baylisascaris procyonis, or raccoon roundworm, is a rare cause of eosinophilic meningoencephalitis with historically poor clinical outcomes. Symptoms of neural larval migrans begin approximately 2-4 weeks after ingestion with fatigue, nausea, fever, and lethargy and then rapidly progress to weakness, incoordination, ataxia, seizures, altered mental status, and finally coma. Only 31 other cases of CNS Baylisascaris neural larval migrans have been reported, with more than 25% being lethal. Of the remaining cases, all but 3 were neurologically devastated largely because of delays in diagnosis and treatment. We present a case of an infant with Baylisascaris neural larval migrans manifested as right hemiparesis, ataxia, and cortical blindness. Eosinophilia was missed at an outside hospital due to misidentification of eosinophils as monocytes on automated cell differential. Repeated testing of serum and CSF revealed marked eosinophilia consistent with eosinophilic meningoencephalitis, and serum antibody testing through the Centers of Disease Control confirmed Baylisascaris infection. Notably, this child had a remarkably positive outcome with near complete recovery of neurologic function after treatment with albendazole and steroids. Although eosinophilic meningoencephalitis is rare, accounting for less than 3% of all lumbar punctures with pleocytosis, this case illustrates (1) the importance of early disease recognition and treatment to improve patient outcomes and (2) the fact that automated cell differentials may misidentify eosinophils as monocytes.

A Worm’s Tale or Why to Avoid the Raccoon Latrine: A Case of Baylisascaris procyonis Meningoencephalitis

The raccoon roundworm Baylisascaris procyonis (B. procyonis) may infect humans to cause severe or fatal meningoencephalitis, as well as ocular and visceral larva migrans. Young children are at greater risk for cerebral larva migrans with severe meningoencephalitis, and early empiric therapy may improve outcomes. Familiarity with characteristic brain imaging findings may prompt earlier diagnosis, particularly in the setting of CSF eosinophilia. We report a case of a 19-month-old boy who presented with truncal ataxia and was found to have peripheral and CSF eosinophilia. MRI demonstrated symmetric, confluent T2 hyperintense signal in the cerebral and cerebellar deep white mater, which helped differentiate B. procyonis meningoencephalitis from other infectious and non-infectious causes of eosinophilic meningoencephalitis. Early recognition and treatment of B. procyonis meningoencephalitis are important for improved outcomes, and careful review of neuroimaging can play a critical role in suggesting the diagnosis.

Population pharmacokinetics of ivermectin for the treatment of scabies in Indigenous Australian children

Ivermectin is a broad-spectrum antiparasitic agent used for the treatment and control of neglected tropical diseases. In Australia, ivermectin is primarily used for scabies and is licensed in children aged ≥5 years weighing >15 kg. However, young children, aged <5 years, are particularly vulnerable to scabies and its secondary complications. Therefore, this study aimed to determine an appropriate ivermectin dose for children aged 2 to 4 years and weighing ≤15 kg. We conducted a prospective, pharmacokinetic study of ivermectin in Indigenous Australian children aged between 5 and 15 years and weighing >15 kg. Doses of 200 μg/kg rounded to the nearest whole or half 3 mg tablet were given to children with scabies and ivermectin concentrations determined at two time points after dosing. A population pharmacokinetic model was developed using non-linear mixed effects modelling. A separate covariate database of children aged 2 to 4 years and weighing <15 kg was used to generate 1000 virtual patients and simulate the dose required to achieve equivalent drug exposure in young children as those aged ≥5 years. Overall, 26 children who had 48 ivermectin concentrations determined were included, 11 (42%) were male, the median age was 10.9 years and median body weight 37.6 kg. The final model was a two-compartment model with first-order absorption and linear elimination. For simulated children aged 2 to 4 years, a dose of 3 mg in children weighing 10–15 kg produced similar drug exposures to those >5 years. The median simulated area under the concentration-time curve was 976 μg∙h/L. Using modelling, we have identified a dosing strategy for ivermectin in children aged 2 to 4 years and weighing less than 15 kg that can be prospectively evaluated for safety and efficacy.

Ivermectin is an important drug for the control and treatment of neglected tropical diseases. However, despite numerous studies showing that ivermectin is safe and well tolerated in young children, it is not currently recommended in young children <5 years and <15 kg. Therefore, there are no guidelines for the dose of ivermectin in young or small children. In this study, we firstly determined how much ivermectin is present in blood in children aged 5 years and older. We then used this information to model what happens to ivermectin in childrens’ bodies allowing us to calculate the dose required in children aged less than 5 years and weighing under 15 kg. This study provides a new dosing guideline that can now be tested in clinical studies of children <5 years and <15 kg.

Baylisascaris procyonis Roundworm Seroprevalence among Wildlife Rehabilitators, United States and Canada, 2012-2015

Baylisascaris procyonis roundworms can cause potentially fatal neural larva migrans in many species, including humans. However, the clinical spectrum of baylisascariasis is not completely understood. We tested 347 asymptomatic adult wildlife rehabilitators for B. procyonis antibodies; 24 were positive, suggesting that subclinical baylisascariasis is occurring among this population.

Baylisascaris procyonis-Associated Meningoencephalitis in a Previously Healthy Adult, California, USA

After severe neurocognitive decline developed in an otherwise healthy 63-year-old man, brain magnetic resonance imaging showed eosinophilic meningoencephalitis and enhancing lesions. The patient tested positive for antibodies to Baylisascaris spp. roundworms, was treated with albendazole and dexamethasone, and showed improvement after 3 months. Baylisascariasis should be considered for all patients with eosinophilic meningitis.

Prevalence of Baylisascaris in domestic dog coprological examinations in the United States, 2013-2016

Dogs are alternative definitive hosts for Baylisascaris procyonis, the raccoon roundworm, but broad-scale prevalence and distribution of canine cases is not known. Based on a large dataset from nationwide reference laboratories, Baylisascaris spp. eggs were detected in 504/9,487,672 (0.005%) canine fecal samples. While many of the positive dog samples originated in areas of known high B. procyonis prevalence in raccoons, positives were also detected in 9 new states. Young dogs, large breeds, and certain regions had higher prevalence. Although overall prevalence was low, and some infections may be spurious, these results demonstrate that dogs may shed Baylisascaris spp. into domestic environments. Routine parasitic testing, rigorous preventive use, and restrictions on coprophagy should be encouraged to reduce risk of human or animal exposure to infectious eggs.

Update on Baylisascariasis, a Highly Pathogenic Zoonotic Infection

Baylisascaris procyonis, the raccoon roundworm, infects a wide range of vertebrate animals, including humans, in which it causes a particularly severe type of larva migrans. It is an important cause of severe neurologic disease (neural larva migrans [NLM]) but also causes ocular disease (OLM; diffuse unilateral subacute neuroretinitis [DUSN]), visceral larva migrans (VLM), and covert/asymptomatic infections. B. procyonis is common and widespread in raccoons, and there is increasing recognition of human disease, making a clinical consideration of baylisascariasis important. This review provides an update for this disease, especially its clinical relevance and diagnosis, and summarizes the clinical cases of human NLM and VLM known to date. Most diagnosed patients have been young children less than 2 years of age, although the number of older patients diagnosed in recent years has been increasing. The recent development of recombinant antigen-based serodiagnostic assays has aided greatly in the early diagnosis of this infection. Patients recovering with fewer severe sequelae have been reported in recent years, reinforcing the current recommendation that early treatment with albendazole and corticosteroids should be initiated at the earliest suspicion of baylisascariasis. Considering the seriousness of this zoonotic infection, greater public and medical awareness is critical for the prevention and early treatment of human cases.

Baylisascaris larva migrans

Baylisascaris procyonis is a roundworm of the raccoon found primarily in North America but also known to occur in other parts of the world including South America, Europe, and Japan. Migration of the larvae of this parasite is recognized as a cause of clinical neural larva migrans (NLM) in humans, primarily children. It is manifested as meningoencephalitis associated with marked eosinophilia of the cerebrospinal fluid and peripheral blood. Diagnosis is made by recovering and identifying larvae in or from the tissues, epidemiological history, serology, and imaging of the central nervous system. Treatment is with albendazole and steroids, although the prognosis is generally poor. This parasite can also cause ocular larva migrans (OLM) which usually presents as diffuse unilateral subacute neuroretinitis (DUSN). The ocular diagnosis can be made by visualizing the larva in the eye and by serology. Intraocular larvae can be destroyed by photocoagulation although albendazole and steroids may also be used. However, once visual disturbance is established the prognosis for improved vision is poor. Related Baylisascaris species occur in skunks, badgers, and certain other carnivores, although most cases of NLM are caused by B. procyonis. Baylisascaris procyonis has also been found in kinkajous in the USA and South America and may also occur in related procyonids (coatis, olingos, etc.).

Parasites and the conservation of small populations: The case of Baylisascaris procyonis

Human demands on natural resources result in landscape changes that facilitate the emergence of disease. Most emerging diseases are zoonotic, and some of these pathogens play a role in the decline of vulnerable wildlife species. Baylisascaris procyonis, the common roundworm parasite of raccoons (Procyon lotor), is a well recognized zoonotic infection that has many of the properties associated with a pathogen capable of driving extinction. It is highly non-specific and frequently pathogenic with regard to paratenic hosts, which contact eggs of B. procyonis at raccoon latrines. Eggs accumulate at latrines and remain viable for many years. Transmission of B. procyonis is sensitive to changes in land-use, and fragmented habitats increase contact rates between raccoons, potential paratenic hosts, and the parasite. Raccoons, and subsequently B. procyonis, have been introduced to Europe and Japan, where naïve vertebrates may be exposed to the parasite. Finally, domestic animals and exotic pets can carry patent infections with B. procyonis, thus increasing environmental contamination beyond raccoon latrines, and expanding the area of risk to potential paratenic hosts. This parasite can potentially contribute to extinctions of vulnerable species, as exemplified by the case of the Allegheny woodrat (Neotoma magister), a species that has experienced local declines and extinctions that are linked to B. procyonis. Conservation strategies for vulnerable species should consider the transmission ecology of parasitic pathogens, like B. procyonis.

Central nervous system infections in travelers

International travelers commonly contract infections while abroad, many of which are primary neurological diseases or have potential neurological sequelae. The implications of these neuroinfectious diseases extend beyond the individual, since returning travelers may contribute to the spread of infection in novel areas. In this review, we discuss signs, symptoms, treatments, and prophylaxes for these infections, as well as emerging trends with regard to neuroinfectious diseases of the returning traveler.

Interlaboratory optimization and evaluation of a serological assay for diagnosis of human baylisascariasis

A Western blot assay using a recombinant protein, recombinant Baylisascaris procyonis RAG1 protein (rBpRAG1), was developed for the diagnosis of human baylisascariasis concurrently by the Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia, and the National Reference Centre for Parasitology (NRCP) in Montreal, Canada. Assay performance was assessed by testing 275 specimens at the CDC and 405 specimens at the NRCP. Twenty specimens from 16 cases of baylisascariasis were evaluated. Eighteen were positive, with the assay correctly identifying 14 of 16 patients. The rBpRAG1 Western blot assay showed no cross-reactivity with Toxocara-positive serum and had an overall sensitivity of 88% and a specificity of 98%.

Mechanisms of CNS invasion and damage by parasites

Invasion of the central nervous system (CNS) is a most devastating complication of a parasitic infection. Several physical and immunological barriers provide obstacles to such an invasion. In this broad overview focus is given to the physical barriers to neuroinvasion of parasites provided at the portal of entry of the parasites, i.e., the skin and epithelial cells of the gastrointestinal tract, and between the blood and the brain parenchyma, i.e., the blood-brain barrier (BBB). A description is given on how human pathogenic parasites can reach the CNS via the bloodstream either as free-living or extracellular parasites, by embolization of eggs, or within red or white blood cells when adapted to intracellular life. Molecular mechanisms are discussed by which parasites can interact with or pass across the BBB. The possible targeting of the circumventricular organs by parasites, as well as the parasites' direct entry to the brain from the nasal cavity through the olfactory nerve pathway, is also highlighted. Finally, examples are given which illustrate different mechanisms by which parasites can cause dysfunction or damage in the CNS related to toxic effects of parasite-derived molecules or to immune responses to the infection.

Good outcome with early empiric treatment of neural larva migrans due to Baylisascaris procyonis

We report a remarkably good outcome in a 14-month-old boy with early clinical diagnosis and aggressive empirical treatment of neural larva migrans caused by the raccoon roundworm Baylisascaris procyonis. He presented with fever, meningismus, lethargy, irritability and asymmetric spastic extremity weakness. Early findings of marked blood and cerebrospinal fluid eosinophilia and of diffuse white matter signal abnormality in the brain and spinal cord on MRI suggested a parasitic encephalomyelitis. Rapid presumptive treatment with albendazole and high-dose steroids halted progression of clinical signs. The diagnosis was confirmed by 2 sequential enzyme-linked immunosorbent assay studies positive for B procyonis serum immunoglobulin G and by Western blot. Field examination with soil sampling yielded infective Baylisascaris eggs. Repeat MRI 3 months later showed atrophy and diffuse, chronic white matter abnormalities, discordant with the marked clinical improvement in this interval. At 10 months, residual neurologic deficits included subtle paraparesis and moderate language delay. This case is the first in which spinal involvement in human Baylisascaris infection was clinically suspected and confirmed by neuroimaging. Importantly, early diagnosis and aggressive treatment of Baylisascaris meningo-encephalitis and myelitis with albendazole and high-dose steroids likely contributed to the good outcome in this patient, in contrast with previous reports.

The mitochondrial genome of Baylisascaris procyonis

Background

Baylisascaris procyonis (Nematoda: Ascaridida), an intestinal nematode of raccoons, is emerging as an important helminthic zoonosis due to serious or fatal larval migrans in animals and humans. Despite its significant veterinary and public health impact, the epidemiology, molecular ecology and population genetics of this parasite remain largely unexplored. Mitochondrial (mt) genomes can provide a foundation for investigations in these areas and assist in the diagnosis and control of B. procyonis. In this study, the first complete mt genome sequence of B. procyonis was determined using a polymerase chain reaction (PCR)-based primer-walking strategy.

Methodology/Principal Findings

The circular mt genome (14781 bp) of B. procyonis contained 12 protein-coding, 22 transfer RNA and 2 ribosomal RNA genes congruent with other chromadorean nematodes. Interestingly, the B. procyonis mtDNA featured an extremely long AT-rich region (1375 bp) and a high number of intergenic spacers (17), making it unique compared with other secernentean nematodes characterized to date. Additionally, the entire genome displayed notable levels of AT skew and GC skew. Based on pairwise comparisons and sliding window analysis of mt genes among the available 11 Ascaridida mtDNAs, new primer pairs were designed to amplify specific short fragments of the genes cytb (548 bp fragment) and rrnL (200 bp fragment) in the B. procyonis mtDNA, and tested as possible alternatives to existing mt molecular beacons for Ascaridida. Finally, phylogenetic analysis of mtDNAs provided novel estimates of the interrelationships of Baylisasaris and Ascaridida.

Conclusions/Significance

The complete mt genome sequence of B. procyonis sequenced here should contribute to molecular diagnostic methods, epidemiological investigations and ecological studies of B. procyonis and other related ascaridoids. The information will be important in refining the phylogenetic relationships within the order Ascaridida and enriching the resource of markers for systematic, population genetic and evolutionary biological studies of parasitic nematodes of socio-economic importance.

Molecular cloning of an immunogenic protein of Baylisascaris procyonis and expression in Escherichia coli for use in developing improved serodiagnostic assays

Larva migrans caused by Baylisascaris procyonis is an important zoonotic disease. Current serological diagnostic assays for this disease depend on the use of the parasite's larval excretory-secretory (ES) antigens. In order to identify genes encoding ES antigens and to generate recombinant antigens for use in diagnostic assays, construction and immunoscreening of a B. procyonis third-stage larva cDNA expression library was performed and resulted in identification of a partial-length cDNA clone encoding an ES antigen, designated repeat antigen 1 (RAG1). The full-length rag1 cDNA contained a 753-bp open reading frame that encoded a protein of 250 amino acids with 12 tandem repeats of a 12-amino-acid long sequence. The rag1 genomic DNA revealed a single intron of 837 bp that separated the 753-bp coding sequence into two exons delimited by canonical splice sites. No nucleotide or amino acid sequences present in the GenBank databases had significant similarity with those of RAG1. We have cloned, expressed, and purified the recombinant RAG1 (rRAG1) and analyzed its diagnostic potential by enzyme-linked immunosorbent assay. Anti-Baylisascaris species-specific rabbit serum showed strong reactivity to rRAG1, while only minimal to no reactivity was observed with sera against the related ascarids Toxocara canis and Ascaris suum, strongly suggesting the specificity of rRAG1. On the basis of these results, the identified RAG1 appears to be a promising diagnostic antigen for the development of serological assays for specific detection of B. procyonis larva migrans.

Differentiation of larva migrans caused by Baylisascaris procyonis and Toxocara species by Western blotting

Baylisascaris procyonis and Toxocara species are two important causes of larva migrans in humans. Larva migrans caused by Toxocara spp. is well known and is diagnosed serologically by enzyme immunoassay. Over a dozen cases of larva migrans and associated eosinophilic encephalitis caused by B. procyonis have also been reported, and at least a dozen additional cases are known. An enzyme-linked immunosorbent assay (ELISA) using the excretory-secretory (ES) antigen of B. procyonis larvae is currently being used in our laboratory as an aid in the diagnosis of this infection in humans. Clinically affected individuals show very high reactivity (measured as the optical density) on this ELISA; however, a one-way cross-reactivity with Toxocara spp. has been observed. As an approach to differentiate these two infections based on serology, we performed Western blots, wherein the B. procyonis ES antigen was reacted with serum samples from individuals known to be positive for either Toxocara spp. or B. procyonis larva migrans. Western blot results showed that B. procyonis antigens of between 30 and 45 kDa were specifically identified only by the sera from individuals with Baylisascaris larva migrans, thus allowing for differentiation between the two infections. This included human patient serum samples submitted for serologic testing, as well as sera from rabbits experimentally infected with B. procyonis. When used in conjunction with the ELISA, Western blotting could be an efficient tool for diagnosis of this infection in humans.

Update on eosinophilic meningoencephalitis and its clinical relevance

Eosinophilic meningoencephalitis is caused by a variety of helminthic infections. These worm-specific infections are named after the causative worm genera, the most common being angiostrongyliasis, gnathostomiasis, toxocariasis, cysticercosis, schistosomiasis, baylisascariasis, and paragonimiasis. Worm parasites enter an organism through ingestion of contaminated water or an intermediate host and can eventually affect the central nervous system (CNS). These infections are potentially serious events leading to sequelae or death, and diagnosis depends on currently limited molecular methods. Identification of parasites in fluids and tissues is rarely possible, while images and clinical examinations do not lead to a definitive diagnosis. Treatment usually requires the concomitant administration of corticoids and anthelminthic drugs, yet new compounds and their extensive and detailed clinical evaluation are much needed. Eosinophilia in fluids may be detected in other infectious and noninfectious conditions, such as neoplastic disease, drug use, and prosthesis reactions. Thus, distinctive identification of eosinophils in fluids is a necessary component in the etiologic diagnosis of CNS infections.

Recurrent cerebral larva migrans: A case report and review of literature

Cerebral larva migrans (CLM) is an uncommon and rarely diagnosed entity. We report here a histopathologically proven case of CLM in a 13 year-old girl, who presented with bilateral focal seizures, right hemiparesis, and lapsed into altered sensorium prior to admission. Her CT scan was suggestive of a granulomatous lesion which eventually turned out to be CLM (toxocariasis). Interestingly, the lesion recurred after excision, with a confusing clinical picture. Following the second surgery, the pathology was reconfirmed and cure was provided for the disease. There has been no further intracranial recurrence during the past ten years although she developed cutaneous lesions.

Central nervous system and eye manifestations of infection with Baylisascaris procyonis

Baylisascaris procyonis, a parasitic infection of raccoons, causes severe neurologic and ocular disease in humans when infectious eggs from raccoon feces are ingested. In the absence of a serologic test, definitive diagnosis is challenging but can be made by isolation of larvae in brain biopsy, direct visualization of the worm in the eye, or exclusion of other potential causes of eosinophilic meningoencephalitis. Currently, no effective treatment has been identified, making preventive efforts critical.

Neuroparasitic infections: nematodes

Globalization has produced an increase in the number of people at risk for contracting parasitic infection. Central nervous system infection by nematodal parasites can be devastating. Early recognition and treatment of infection can significantly decrease morbidity of the parasitic infection, as well as the risk of secondary superinfection. The clinical presentation, diagnosis, and treatment for five of the more common nematodal infections of the nervous system--Angiostrongylus spp., Baylisacaris procyonis, Gnathostoma spinigerum, Strongyloides stercoralis, and Toxocara spp.--is reviewed.

Baylisascariasis

The raccoon roundworm, Baylisascaris procyonis, is the most common and widespread cause of clinical larva migrans in animals. In addition, it is increasingly recognized as a cause of devastating or fatal neural larva migrans in infants and young children and ocular larva migrans in adults. Humans become infected by accidentally ingesting infective B. procyonis eggs from raccoon latrines or articles contaminated with their feces. Two features distinguish B. procyonis from other helminthes that cause larva migrans: (i) its aggressive somatic migration and invasion of the central nervous system and (ii) the continued growth of larvae to a large size within the central nervous system. Typically, B. procyonis neural larva migrans presents as acute fulminant eosinophilic meningoencephalitis. Once invasion of the central nervous system has occurred, the prognosis is grave with or without treatment. To date, despite anthelmintic treatment of cases of B. procyonis neural larva migrans, there are no documented neurologically intact survivors. Epidemiologic study of human cases of neural larva migrans demonstrate that contact with raccoon feces or an environment contaminated by infective eggs and geophagia or pica are the most important risk factors for infection. In many regions of the United States, increasingly large populations of raccoons, with high rates of B. procyonis infection, live in close proximity to humans. Although documented cases of human baylisascariasis remain relatively uncommon, widespread contamination of the domestic environment by infected raccoons suggests that the risk of exposure and human infection is probably substantial. In the absence of early diagnosis or effective treatment, prevention of infection is the most important public health measure.

Severe and fatal central nervous system disease in humans caused by Baylisascaris procyonis, the common roundworm of raccoons: a review of current literature

Baylisascaris procyonis, a parasitic infection of raccoons, causes severe neurologic disease in humans when infective eggs from raccoon feces are ingested. Definitive diagnosis is challenging, but can be made by isolation of larvae in brain biopsy or exclusion of other potential causes of eosinophilic meningoencephalitis. Prevention efforts are critical due to the lack of effective treatment.

Raccoon roundworm encephalitis

The raccoon roundworm, Baylisascaris procyonis, is increasingly recognized as a cause of zoonotic visceral, ocular, and neural larva migrans and, in particular, of devastating encephalitis in young children. Exposure occurs mainly at raccoon latrines, where large numbers of infective eggs may be accidentally ingested. Risk factors for infection include contact with raccoon latrines, pica/geophagia, age of <4 years, and male sex. The severity of central nervous system (CNS) disease depends on the number of eggs ingested, the extent and location of larval migration, and the severity of ensuing inflammation and necrosis. Diagnosis of Baylisascaris encephalitis is based on clinical CNS disease, peripheral and cerebrospinal fluid eosinophilia, deep white matter lesions visible by magnetic resonance imaging, and positive results of serologic tests. Treatment efficacy in clinical cases is poor, but albendazole prevents disease if given promptly after infection. Considering the seriousness of this disease and limitations of diagnosis and treatment, prevention of infection with eggs is of utmost importance.

Larva migrans by Baylisascaris transfuga: fatal neurological diseases in Mongolian jirds, but not in mice

Raccoon roundworms (Baylisascaris procyonis) and other Baylisascaris species cause patent or latent larva migrans (LM) in a variety of mammals and birds, including humans. It is not clear whether LM by Baylisascaris transfuga, roundworms of bears, is associated with clinical neurological disorders. To clarify this issue, ICR and BALB/c mice as well as Mongolian jirds (Meriones unguiculatus) were orally inoculated with 2,000-5,000 embryonated eggs of B. transfuga. In mice, the ascarid caused symptomatic LM of limited extent and duration, whereas the infection was fatal in jirds; i.e., they exhibited general signs such as severe depression and emaciation on days 8-11 postinfection (PI) and died, or they developed progressive and fatal neurological disorders after day 14 PI. Histological examination showed B. transfuga larvae in the brain of all mice and jirds examined, and the larvae collected from them developed to a size comparable with that of B. procyonis. There existed, however, critical differences in host reactions against larvae localized in the brain of mice and jirds; B. transfuga larvae found in mice were surrounded by granulomatous reactions and immobilized, whereas larvae found in jirds were free from any host reaction and mobile, causing extensive malacia.

Emerging parasitic infections

Parasitic infections are felt by most individuals to have little impact on the health and well being of most inhabitants of Canada, Western Europe, and the United States. As the authors show in this article, parasites are always "emerging" somewhere and have a significant impact on those areas of the world. Moreover, as we are becoming an ever-smaller global village, catastrophes and instability in the Third World affect control of parasitic diseases endemic to those areas, ensuring greater chances of transmission to visitors there. The foundation of successful limitation of parasitic diseases in both developing and developed regions is still accurate and rapid diagnosis.

Raccoon roundworm eggs near homes and risk for larva migrans disease, California communities

The raccoon roundworm, Baylisascaris procyonis, is increasingly recognized as a cause of serious or fatal larva migrans disease in humans and animals. We assessed the potential for infection in three northern California communities by determining the density and distribution of raccoon latrines, where transmission primarily occurs, and the prevalence of eggs at private residences. We collected fecal samples from 215 latrines and found that 44%-53% of the latrines contained B. procyonis eggs and that 16%-32% contained infective eggs. Among the properties surveyed, 28%-49% harbored at least one latrine that was positive for B. procyonis eggs. The latrine densities in these communities were higher than any previously reported. The presence of B. procyonis eggs in raccoon latrines was common, widespread, and closely associated with human habitation. Where raccoon densities are high, education of the public and removal of raccoons may be necessary.

Neuropathological observation of rabbits (Oryctolagus cuniculus) affected with raccoon roundworm (Baylisascaris procyonis) larva migrans in Japan

Larvae of the raccoon roundworm, Baylisascaris procyonis (B. procyonis) are a known cause of cerebrospinal larva migrans in animals and humans. The present paper described details of the central nervous lesion in the rabbits (Oryctolagus cuniculus) affected with B. procyonis larva migrans in Japan. Clinically affected animals showed neurological signs including circling, torticollis, tremor of head, or ataxic gait. The most characteristic pathological alterations were large malacic lesions associated with an activated astroglial proliferation which was seen at the corpus medullare in the cerebellum including the cerebellar peduncle. Moreover, focal malacic lesions with perivascular cuffing and infiltration by lymphocytes and heterophiles were scattered everywhere throughout the brain. In these lesions or normal-appearing areas away from obvious lesions, ascarid larvae, about a maximum 65-75 micro m in diameter, were recognized. Other prominent features were minute lesions (we call them migration tract-like lesions) composed of lymphocytes, hemosiderin-laden macrophages and reactive astrocytes scattering throughout the cerebrum. In this study, we demonstrated ascarid larvae in only eight out of 23 animals diagnosed as B. procyonis larva migrans. Since it is not always possible to detect the larvae, the possibility of B. procyonis larva migrans must be given serious consideration to the characteristic lesions described above.

Eye findings of diffuse unilateral subacute neuroretinitis and multiple choroidal infiltrates associated with neural larva migrans due to Bbaylisascaris procyonis

PURPOSE

To report childhood infection with Baylisascaris procyonis (raccoon round worm) manifesting as diffuse unilateral subacute neuroretinitis (DUSN) and choroidal infiltrates in association with neurologic disease (neural larva migrans).

METHOD

Observational case series, one with eye manifestations of DUSN, the other with choroidal infiltrates, both with severe neurologic degeneration.

RESULTS

Indirect immunofluorescence assays on serum and cerebrospinal fluid were positive for B. procyonis in one and serially positive and increasing in the other. Both children had a history of pica and raccoon exposure.

CONCLUSIONS

Baylisascaris procyonis infection is associated with two cases of severe neurologic degeneration with ocular lesions: DUSN and choroidal infiltrates. Although B. procyonis is known to cause DUSN, these cases indicate that concomitant ocular migration may accompany neural larva migrans. These are the third and forth cases in the US literature of neural larva migrans due to B. procyonis with eye findings.

Epidemiological aspects of the first outbreak of Baylisascaris procyonis larva migrans in rabbits in Japan

Larva migrans caused by the common raccoon ascarid, Baylisascaris procyonis, is a zoonotic disease of critical importance in North America. Recently we encountered the first proven outbreak of this disease in Japan in domestic rabbits (Oryctolagus cuniculus) in a small wildlife park. In this park, raccoons (Procyon lotor) had been kept for 9 years, and one raccoon was donated to the park by a pet owner 8 weeks prior to the occurrence of an outbreak in rabbits. Of 12 total raccoons, three raccoons including the donated one shed B. procyonis eggs in the feces, and two of these positive raccoons were kept in metal mesh cages on wooden pedestals, 2 m distant from the rabbit enclosure. Circumstantial evidence indicates that the donated raccoon is the likely source of this outbreak. Treatment of the raccoons with an ascaricide and decontamination by extensive flaming of the cages and the contaminated dirt floor of the park achieved a transient disappearance of ascarids from all 12 enclosed raccoons. Three months after the control measures began, recurrent ascarid infection was detected in three young raccoons of less than 1.5 years of age. The potential risk of serious zoonosis by B. procyonis as well as the difficulty in a clearance of contaminated areas should be considered by pet owners and public health workers in Japan.

Eosinophilic meningitis

Eosinophilic meningitis is a rare clinical entity that can be useful in narrowing the differential diagnosis of central nervous system disease. It is defined by the presence of 10 or more eosinophils/microL in the cerebrospinal fluid (CSF) or a CSF eosinophilia of at least 10%. The most common cause is invasion of the central nervous system by helminthic parasites, particularly Angiostrongylus cantonensis, but other infections as well as noninfectious conditions may also be associated. This review describes the etiologies of eosinophilic meningitis, focusing primarily on the helminths that cause CSF eosinophilia.

Neural larva migrans caused by the raccoon roundworm Baylisascaris procyonis

Baylisascaris procyonis, the common raccoon roundworm, is a rare cause of devastating or fatal neural larva migrans in infants and young children. We describe the clinical features of two children from suburban Chicago who developed severe, nonfatal B. procyonis neural larva migrans. Despite treatment with albendazole and high dose corticosteroids, both patients are neurologically devastated. In many regions of North America, large populations of raccoons with high rates of endemic B. procyonis infection live in proximity to humans, which suggests that the risk of human infection is probably substantial. In the absence of effective treatment, prevention of infection remains the most important public health strategy.

Baylisascaris procyonis: an emerging helminthic zoonosis

Baylisascaris procyonis, a roundworm infection of raccoons, is emerging as an important helminthic zoonosis, principally affecting young children. Raccoons have increasingly become peridomestic animals living in close proximity to human residences. When B. procyonis eggs are ingested by a host other than a raccoon, migration of larvae through tissue, termed larval migrans, ensues. This larval infection can invade the brain and eye, causing severe disease and death. The prevalence of B. procyonis infection in raccoons is often high, and infected animals can shed enormous numbers of eggs in their feces. These eggs can survive in the environment for extended periods of time, and the infectious dose of B. procyonis is relatively low. Therefore, the risk for human exposure and infection may be greater than is currently recognized.

Eosinophil-associated inflammation and elaboration of eosinophil-derived proteins in 2 children with raccoon roundworm (Baylisascaris procyonis) encephalitis

OBJECTIVE

Eosinophil-associated proteins, especially eosinophil-derived neurotoxin, may be important contributors to the neurologic pathology and symptoms caused by Baylisascaris procyonis infection.

METHODS

Two cases of severe B procyonis encephalitis with evidence of marked eosinophil degranulation in the central nervous system are presented. Serial cerebrospinal fluid (CSF) specimens were collected from each patient during the course of their illness. Antibodies against B procyonis were measured in the patients' serum and CSF. Levels of the eosinophilopoietin interleukin-5 (IL-5) and 2 important eosinophil proteins, eosinophil-derived neurotoxin and major basic protein, were assayed in the CSF.

RESULTS

Both patients had rapidly progressive central nervous system disease with evidence of eosinophilic meningoencephalitis. Both tested positive for antibodies to B procyonis in serum and CSF and had progressively worsening deep white matter changes on magnetic resonance images of the brain. CSF levels of IL-5, eosinophil-derived neurotoxin, and major basic protein were markedly elevated over controls.

CONCLUSIONS

This is the first report of the measurement of IL-5, eosinophil-derived neurotoxin, and major basic protein in human CSF. In addition to traumatic damage and necrosis caused by migrating larvae, eosinophil-derived neurotoxin from associated eosinophilic inflammation may be an important contributory factor in the pathogenesis of B procyonis encephalitis. parasite, eosinophil-derived-neurotoxin, major basic protein, eosinophilia, hypereosinophilia, interleukin-5, encephalitis, child.

Raccoon roundworm (Baylisascaris procyonis) encephalitis: case report and field investigation

Baylisascaris procyonis is a common and widespread parasite of raccoons in the United States and Canada. With large raccoon populations occurring in many areas, the potential risk of human infection with B procyonis is high. We report a case of severe raccoon roundworm (B procyonis) encephalitis in a young child to illustrate the unique clinical, diagnostic, and treatment aspects, as well as public health concerns of B procyonis infection. Acute and convalescent serum and cerebrospinal fluid samples from the patient were tested for antibodies against B procyonis to assist in documenting infection. An extensive field survey of the patient's residence and the surrounding community was performed to investigate raccoon abundance and to determine the extent of raccoon fecal contamination and B procyonis eggs in the environment. The patient evidenced serologic conversion, and the field investigation demonstrated a raccoon population far in excess of anything previously reported. There was abundant evidence of B procyonis eggs associated with numerous sites of raccoon defecation around the patient's residence and elsewhere in the community. Because B procyonis can produce such severe central nervous system disease in young children, it is important that pediatricians are familiar with this infection. The public should be made aware of the hazards associated with raccoons and B procyonis to hopefully prevent future cases of B procyonis infection.

Current views on geographic distribution and modes of infection of neurohelminthic diseases

Neurohelminthiases are more prevalent in geographic areas where environmental factors and poor sanitary conditions favor the parasitism between man and animals. In recent years, population shifts and rapid transport have facilitated the spread of certain helminthic diseases from endemic to non-endemic areas. Although many helminthic parasites are known to cause various human diseases afflicting many millions of people in the world, neurohelminthiases are often not diagnosed because they have been unrecognized by clinicians or confirmatory diagnostic tests are not easily available. Paragonimiasis and schistosomiasis (fluke diseases) are endemic in Asia, Africa and Central America; lesions in the central nervous system (CNS) due to ectopic parasitism of the preadult and adult flukes produce various clinical features that often mimic other diseases. In most cestodiasis (tapeworm disease), the adult worm that lodges in the alimentary tract does not involve the CNS; however, the larvae often enter the nervous system by migration or by metastasis via the systemic circulation, where they cause cystic lesions. Cysticercosis is the most common CNS helminthic infection especially in endemic areas where the parasitism between man and pigs is maintained. In other cestodiases, infections to man are often caused by ingestion of food or water contaminated with feces of the definitive hosts (mammals or man). Nematodes (roundworms) generally enter the CNS by ectopic migration of the infective larvae (larva migrans); the routes of infection to man vary with species of the nematodes, and the animal hosts they infest. Angiostrongylus cantonensis is a neurotropic nematode that requires the CNS of mammalian hosts for its growth; the third-stage larvae frequently invade skeletal muscles and the nervous system. Strongyloides, a gastrointestinal nematode, is known to cause CNS involvement in immunosuppressed patients. Recently, some nematodes heretofore unknown to cause human parasitism have been recognized as the causative agents of CNS infections.