Transmission of toxocariasis

Toxocara tanuki larval distribution in mice and the infectivity of tissue larvae

Toxocara tanuki is a common large roundworm in raccoon dogs. Experimental infection studies of T. tanuki in mice were conducted to clarify the distribution and infectivity of larvae in tissue. Groups of BALB/c and C57BL/6 mice (n = 5 mice/group) were each inoculated with 1000 embryonated T. tanuki eggs and necropsied at 7, 31, 91, and 182 days post inoculation (dpi). The number of larvae in the central nervous system, heart, lungs, kidneys, spleen, gastrointestinal tract, liver, and carcass was examined. Larvae obtained from the aforementioned mice on different days of the necropsy were orally inoculated into four groups of ICR mice (n = 6 mice/group) that were then necropsied at 21 dpi. Larvae were recovered from all mice. In the BALB/c and C57BL/6 mice, most of the larvae (> 88.7%) were recovered from the liver and the remainder from other tissues. The total number of larvae recovered from C57BL/6 mice was significantly higher than that from BALB/c mice, but no difference in the relative larval distribution within the viscera between the two mouse strains was observed. The mean recovery percentage of larvae from ICR mice infected with 182-day-old tissue larvae was 3.3%. Our findings showed that T. tanuki larvae migrated predominantly to the liver of mice and that the larvae maintained their infectivity for at least half a year.

Is it canine DUSN?: Another view of retinopathies, some acquired, and others possibly "inherited": Another view of retinopathies, some acquired, and others possibly "inherited"

The term retinopathy has been used to group several heterogeneous retinal abnormalities that are clearly acquired or are suspected/proposed to be inherited. Some share characteristic focal/multifocal hyperreflective tapetal lesions with a dark center, and areas of non-tapetal depigmentation suggestive of patchy or diffuse outer retinal atrophy. Progression is variable, and some develop unilateral or bilateral fundus changes resembling the clearly inherited form of retinal degeneration referred to as PRA. In this Commentary and Review, we discuss the role of ocular larva migrans resulting in the entity we refer to as canine DUSN and suggest that it may be responsible for some of the retinal findings grouped under the retinopathy rubric that share this characteristic fundus lesion.

Therapy and Prevention for Human Toxocariasis

For the last four decades, knowledge about human toxocariasis with regard to its epidemiology, pathophysiology, clinical spectrum, and imaging or laboratory diagnosis has substantially progressed. Knowledge about specific therapy with anthelmintics has lagged behind. To date, only four drugs are registered for human use, and their efficacy has rarely been assessed in prospective controlled trials. It is likely that the repurposing of potent anthelmintics from veterinary medicine will improve this situation. Due to its wide availability and a lack of major side effects during short regimens, albendazole has become the drug of choice. However, its efficacy should be more precisely assessed. The role of anthelmintics in the treatment of neurological or ocular toxocariasis remains to be clarified. Prophylactic measures in humans or companion animals are efficient and represent first-line treatments for the control of this zoonosis. Unfortunately, their implementation in areas or countries where toxocariasis epidemiology is driven by poverty is quite difficult or unrealistic.

The Role of Nile Tilapia (Oreochromis niloticus) in the Life Cycle of Toxocara spp

The present study aimed to experimentally assess Nile tilapia as potential paratenic host of Toxocara spp. A total of 15 Nile tilapia (Oreochromis niloticus) were fed with 300 embryonated Toxocara canis eggs by oral gavage, while five others of the control group received distilled water. The fish were individually analyzed at 16, 24, 48, 72, and 240 h after inoculation. Water contamination was assessed, and tissue migration by liver, gastrointestinal tract (GIT), eyes, and central nervous system. A murine model was used as the paratenic host for egg infectivity assessment. Eggs and larvae were found in plastic tank water and fish GIT, ranging from 23 to 86% per fish. Eggs and larvae were recovered from the tank water (76.3%) and fish GIT (23.7%). The counting of eggs and larvae observed was negatively correlated with number of eggs and larvae in the water tank (rho = -0.698, p = 0.003). Shedding of embryonated eggs was first detected at 16 and up to 240 h, with significant egg and larvae yield decrease on water-shedding (p = 0.001) and in the GIT (p = 0.007). Although no T. canis larva was recovered in fish tissues, egg infectivity after fish GIT transit was experimentally confirmed by mice assessment. In conclusion, despite shedding viable embryonated eggs through the gastrointestinal tract, tilapias may not play a role as a suitable paratenic hosts for Toxocara spp., posing low risk of zoonotic transmission by fish meat consumption.

A two-step morphology-PCR strategy for the identification of nematode larvae recovered from muscles after artificial digestion at meat inspection

To ensure that meat from livestock and game is safe for human consumption, European legislation lays down rules for mandatory testing. Helminth larvae are a category of zoonotic foodborne pathogens that can contaminate meat. Among helminths, the only zoonotic nematode regulated in Europe regarding meat inspection is Trichinella spp.. It is precisely during Trichinella testing that other potentially zoonotic larvae can be found. Due to current lack of tools, their identification is often very complicated. Nematode larvae other than Trichinella, recovered from artificial digestions of pig and wild boar muscles from France and Germany, were subjected to a newly developed two-step identification scheme, which includes both morphological examination and molecular assays. The first step is a general orientation towards a broad taxonomic group; the second step consists of targeted identification based on the results of first step. Different parasites were identified, some of which were not zoonotic such as Metastrongylus spp. and Angiostrongylus vasorum, but others are known to be zoonotic such as Toxocara cati, Ascaris suum, and Uncinaria stenocephala. The strategy is efficient for the identification of nematode larvae recovered from muscles but could also be applied for larvae from other sources.

Excretory/Secretory Metabolome of the Zoonotic Roundworm Parasite Toxocara canis

Toxocariasis is a zoonotic disease affecting humans that is predominantly caused by Toxocara canis and T. cati, primarily parasites of dogs and cats, respectively. Toxocara generally establishes long-term infections by co-opting its host's physiological processes, while at the same time exploiting the nutritional environment. Adult stage T. canis reside in the gut of the definitive canine host where they employ a suite of strategies to combat intestinal immune responses by actively producing and releasing excretory-secretory products (ESPs). The protein component of T. canis ESPs has been widely studied, but characterisation of the non-protein ESP complement remains neglected. To characterize the secreted metabolome of Toxocara ESPs and to shed light on the parasite's metabolic processes, we profiled the ESPs of T. canis using both gas chromatography (GC) and liquid chromatography (LC) mass spectrometry approaches. We successfully identified 61 small molecules, including 41 polar metabolites, 14 medium-long chain fatty acids (MLCFAs) and six short chain fatty acids (SCFAs). We identified talose, stearic acid and isovalerate as the major compounds belonging to the polar, MLCFA and SCFA chemical classes, respectively. Most of the 61 identified metabolites appear to have been produced by T. canis via three distinct metabolic pathways - fatty acid, amino acid and carbohydrate metabolism. The majority of the identified ESPs have known biological properties, especially as immunomodulators. However, there is limited/no information on the biological roles or applications of 31 ESP biomolecules, suggesting that these may have novel activities that merit further investigation.

Prevalence of toxocariasis and its related risk factors in humans, dogs and cats in northeastern Iran: a population-based study

BACKGROUND

Toxocariasis is one of the most common zoonotic infections in dogs and cats. The objectives of this study were to determine the prevalence of anti-Toxocara antibodies and identify the epidemiological and clinical features and related risk factors of toxocariasis in the general population along with the prevalence of this infection in dogs and cats in northeast Iran.

METHODS

In this cross-sectional study, anti-Toxocara antibodies from 1150 urban and rural participants were examined using a commercial enzyme-linked immunosorbent assay. In addition, the stool specimens of 538 dogs and 236 cats were tested using the formalin-ether concentration technique. Sociodemographic data and related risk factors were collected using a structured questionnaire and the data on clinical manifestations were obtained from personal health records.

RESULTS

Anti-Toxocara antibodies were detected in 7.2% (83/1150) of the study population. Risk factors for seropositivity based on multivariable analysis were younger age (p=0.019), living in rural areas (p=0.048), occupations with high exposure risk to toxocariasis (p=0.001), contact with dogs or cats (p=0.003), contact with soil (p=0.001), history of geophagy (p=0.001) and the consumption of raw or undercooked liver (p=0.001). The prevalence of symptoms such as asthma, shortness of breath, blurred vision, abdominal pain and epilepsy were significantly higher in seropositive individuals compared with seronegative ones. Toxocara eggs were found in 15.1% (81/538) of dogs and 34.7% (82/236) of cats. A significant relationship was found between infection in dogs and cats and age, type, place of residence and anthelmintic consumption.

CONCLUSIONS

Identification of anti-Toxocara antibodies in the general population and the presence of confirmed infections in dogs and cats indicates exposure to Toxocara infection as a public health problem in northeast Iran.

Toxocara infection in the differential diagnosis of multiple sclerosis in the Middle East

A critical step in the diagnosis of multiple sclerosis is to rule out a heterogeneous variety of multiple sclerosis mimickers, which is crucial in the era of powerful immune-modulator treatments. In this review, we discuss the background of toxocariasis in general, present central nervous system Toxocara infection as one of the multiple sclerosis mimickers in the Middle East, and share our experience about the diagnosis and management of this condition. This entity seems very relevant in a region such as the Middle East, where displacement of populations and conflict can result in non-hygienic food and water management bundles. The diagnosis should be entertained, especially when assessing patients with myelopathy. The presence of a single lesion in the spinal cord with inflammatory features should prompt serological testing for Toxocara IgG and IgM in serum and the cerebrospinal fluid. This infection is treatable, with the regimen of high-dose albendazole being one of the most accepted treatments. Although most cases exhibit a good prognosis, some have residual deficits localized to the affected spinal cord level.

Frequency of Toxocariasis among Patients Clinically Suspected to Have Visceral Toxocariasis: A Retrospective Descriptive Study in Sri Lanka

Introduction

Human toxocariasis is caused by several species of the nematode Toxocara. Two common clinical syndromes are ocular and visceral larva migrans.

Objectives

To determine the Toxocara antibody positivity in clinically suspected VLM patients and to describe demographic factors and clinical manifestations of seropositive patients.

Methods

522 clinically suspected patients were studied between 1993 and 2014. Relevant data was gathered from referral letters. Serum samples were subjected to Toxocara antigen ELISA.

Results

Overall, seropositivity was 50.2% (262), of which 109 (40.8%) were positive at high level of Toxocara antibody carriage and 153 (58.4%) were positive at low levels. The seropositives ranged from 3 months to 70 years (mean = 7.8). Younger age group had higher levels of seropositivity and it was statistically significant. Majority of children under 5 years were seropositive (47.7%, n = 125). Seropositivity was common in males (55.3%, n = 145). Clinical manifestations of seropositives include lymphadenopathy (24.1%) skin rash (22.5%), dyspnoea (21.7%), fever (21%), hepatosplenomegaly (9.2%), and abdominal pain (3.8%). 197 (75.2%) seropositive cases had eosinophilia. These symptoms were not statistically significant.

Conclusions

This study confirms toxocariasis as an important cause of childhood ill health identifying common clinical symptoms recommending preventive measures to limit transmission.

Helminth Infections and Cardiovascular Diseases: Toxocara Species is Contributing to the Disease

Toxocariasis is the clinical term used to describe human infection with either the dog ascarid Toxocara canis or the feline ascarid Toxocara cati. As with other helminths zoonoses, the infective larvae of these Toxocara species cannot mature into adults in the human host. Instead, the worms wander through organs and tissues, mainly the liver, lungs, myocardium, kidney and central nervous system, in a vain attempt to find that, which they need to mature into adults. The migration of these immature nematode larvae causes local and systemic inflammation, resulting in the “larva migrans” syndrome. The clinical manifestations of toxocariasis are divided into visceral larva migrans, ocular larva migrans and neurotoxocariasis. Subclinical infection is often referred to as covert toxocariasis. One of the primary causes of death all around the world is cardiovascular disease that accounted for up to 30 percent of all-cause mortality. Cardiovascular disease and more precisely atherosclerotic cardiovascular disease, is predicted to remain the single leading cause of death (23.3 million deaths by 2030). A-quarter of people presenting the disease does not show any of the known cardiovascular risk factors. Therefore, there is considerable interest in looking for novel components affecting cardiovascular health, especially for those that could improve global cardiovascular risk prediction. This review endeavours to summarize the clinical aspects, new diagnostic and therapeutic perspectives of toxocaral disease with cardiovascular manifestations.

In vitro production of Toxocara canis excretory-secretory (TES) antigen

Toxocara canis is a widespread gastrointestinal nematode parasite of dogs and cause Toxocara larva migrans, an important zoonotic disease in humans on ingestion of infective eggs. Toxocarosis is one of the few human parasitic diseases whose serodiagnosis uses a standardized antigen, T. canis excretory secretory antigen (TES). The present study describes collection of T. canis adult worm, collection and embryonation of T. canis eggs, hatching and separation of T. canis larvae, in vitro maintenance of T. canis second stage larvae for production of TES, concentration of culture fluid TES and yield of TES in correlation with various methods cited in literature.

The occurrence of Toxocara species in naturally infected broiler chickens revealed by molecular approaches

Consuming raw and undercooked meat is known to enhance the risk of human toxocariasis because Toxocara species have a wide range of paratenic hosts, including chickens. The aim of this study was to identify species of Toxocara in naturally infected broiler chickens using molecular approaches. A polymerase chain reaction (PCR) method was used for the differentiation of Toxocara canis and Toxocara cati larvae recovered from tissues and organs, and identified by microscopic observations. Thirty-three 35- to 47-day-old broiler chickens were used for examination of Toxocara larvae. The duodenum, liver, lungs, heart, kidneys, skeletal muscles and brain of each chicken were examined using the pepsin method, and DNA from each tissue was extracted as the template for PCR assay. The findings revealed that 5 of 33 (15.2%) broiler chickens were infected with Toxocara larvae. Larvae were recovered from the liver (n = 19), duodenum (n = 8), skeletal muscles (n = 8) and brain (n = 2) of broiler chickens naturally infected with Toxocara spp. The results showed that the frequencies of the species in the chickens were T. canis larvae (n = 5, 83.3%) and T. cati larvae (n = 1, 16.7%). Our data from the present study demonstrated the importance of broiler chickens as a paratenic host for the parasite's life cycle in the environment. The implementation of DNA amplification as a routine diagnostic technique is a specific and alternative method for identification of Toxocara larvae, and allowed the observation of specific species under field conditions within the locations where broiler chickens are typically raised and exposed to Toxocara spp. eggs or larvae.

Cerebral Toxocariasis: Silent Progression to Neurodegenerative Disorders?

Toxocara canis and T. cati are highly prevalent nematode infections of the intestines of dogs and cats. In paratenic hosts, larvae do not mature in the intestine but instead migrate through the somatic tissues and organs of the body. The presence of these migrating larvae can contribute to pathology. Toxocara larvae can invade the brains of humans, and while case descriptions of cerebral toxocariasis are historically rare, improved diagnosis and greater awareness have contributed to increased detection. Despite this, cerebral or neurological toxocariasis (NT) remains a poorly understood phenomenon. Furthermore, our understanding of cognitive deficits due to toxocariasis in human populations remains particularly deficient. Recent data describe an enhanced expression of biomarkers associated with brain injury, such as GFAP, AβPP, transforming growth factor β1 (TGF-β1), NF-L, S100B, tTG, and p-tau, in mice receiving even low doses of Toxocara ova. Finally, this review outlines a hypothesis to explore the relationship between the presence of T. canis larvae in the brain and the progression of Alzheimer's disease (AD) due to enhanced AD-associated neurodegenerative biomarker expression.

Natural infection of free-range chickens with the ascarid nematode Toxocara sp

Human toxocariasis may be acquired by eating raw chicken liver. However, there are no reports on the prevalence of natural infection of chickens with Toxocara. The aim of this study was to evaluate the presence of anti-Toxocara antibodies as indicators of natural infection with Toxocara, in free-range chickens from Espírito Santo State, Brazil. An ELISA test with secretory and excretory Toxocara canis antigens was used. Negative controls were 20 industrial chickens reared in a high hygiene standard environment. Positive control serum was from a chicken infected with embryonated eggs of T. canis. Sera were adsorbed with Ascaridia galli extract to reduce cross-reactivity. Cut-off was the mean plus four times the standard deviation of optical density (OD) in negative group. One hundred and fifty-seven sera from free-range chicken were investigated. Results showed 58.5% of the chickens were positive with ELISA test; 12.7% had OD over the positive control and may be considered as true infected chickens. The results between the cut-off and the positive control may include infections with low titers of antibodies or may represent serum scar of past infection or may be the result of cross-reaction with other nematodes rather than A. galli which is used for the adsorption of sera. In conclusion, high prevalence of Toxocara sp. antibodies demonstrates natural infection of free-range chickens from Espírito Santo State which may represent a risk of infection with this nematode in people who have the habit of eating raw or undercooked chicken meat or viscera. The results also suggest that chickens may be useful as sentinels to detect soil contaminated with Toxocara eggs.

Microarray gene expression analysis reveals major differences between Toxocara canis and Toxocara cati neurotoxocarosis and involvement of T. canis in lipid biosynthetic processes

Toxocara canis and Toxocara cati are globally occurring intestinal nematodes of dogs and cats with a high zoonotic potential. Migrating larvae in the CNS of paratenic hosts, including humans, may cause neurotoxocarosis resulting in a variety of neurological symptoms. Toxocara canis exhibits a stronger affinity to the CNS than T. cati, causing more severe neurological symptoms in the mouse model. Pathomechanisms of neurotoxocarosis as well as host responses towards the respective parasite are mostly unknown. Therefore, the aim of this study was to characterise the pathogenesis at a transcriptional level using whole genome microarray expression analysis and identify differences and similarities between T. canis- and T. cati-infected brains. Microarray analysis was conducted in cerebra and cerebella of infected C57Bl/6J mice 42daysp.i. revealing more differentially transcribed genes for T. canis- than T. cati-infected brains. In cerebra and cerebella of T. canis-infected mice, a total of 2304 and 1954 differentially transcribed genes, respectively, were identified whereas 113 and 760 differentially transcribed genes were determined in cerebra and cerebella of T. cati-infected mice. Functional annotation analysis revealed major differences in host responses in terms of significantly enriched biological modules. Up-regulated genes were mainly associated with the terms "immune and defence response", "sensory perception" as well as "behaviour/taxis" retrieved from the Gene Ontology database. These observations indicate a strong immune response in both infection groups with T. cati-infected brains revealing less severe reactions. Down-regulated genes in T. canis-infected cerebra and cerebella revealed a significant enrichment for the Gene Ontology term "lipid/cholesterol biosynthetic process". Cholesterol is a highly abundant and important component in the brain, representing several functions. Disturbances of synthesis as well as concentration changes may lead to dysfunction in signal transduction and neurodegenerative disease. Overall, only a minor overlap of differentially transcribed genes was observed between the two infection groups in both brain parts. Most genes are regulated individually in each infection group, supporting the evident differences of both roundworm species observed in the paratenic host in previous studies. In summary the present study underlines the differences in pathogenicity of T. canis and T. cati. It furthermore provides a comprehensive basis for future analyses over the course of infection as well as functional tests to identify gene regulatory circuits that are crucial for pathogenesis of neurotoxocarosis. The results of this study provide a promising foundation for further specific research to evaluate the particular pathogenetic mechanisms and to identify possible therapeutic targets.

Laboratory diagnosis of human toxocariasis

Toxocariasis is a helminth zoonosis caused by infection with the larvae of Toxocara spp. ascarid worms. Only two species, Toxocara canis and Toxocara cati, are recognised as causative agents of human disease. The best choice for serodiagnosis of the generalised forms of toxocariasis, visceral larva migrans (VLM) or covert toxocariasis, relies upon the initial use of TES-ELISA, after which any positive result should subsequently be tested by Western blotting (WB). Covert toxocariasis is mostly a benign infection, so a large majority of infected subjects are asymptomatic or have very few symptoms and therefore go undiagnosed. In this form, this helminthosis is often self-limiting, leaving residual specific antibodies. A positive serodiagnosis caused by residual antibodies that do not have any diagnostic significance can be associated with any infectious or non-infectious disease. If separated from the ongoing clinical and laboratory context, such a positive result has no diagnostic value and should be only taken into account after the possible etiologies of any observed syndromes have been ruled out. Unlike the methods used for the immunodiagnosis of bacterial, viral or protozoal (toxoplasmosis) infections, it is not possible with toxocariasis to assess the age of the presence of specific IgG using the levels of specific IgM because IgM antibodies can be found throughout the course of helminthiasis. The detection of other classes of immunoglobulins, namely IgE and IgA, the subclasses, namely IgG4 or circulating Ag was proven to be unable to discriminate between active and self-cured generalised toxocaral infections. Currently, the diagnosis of an active covert toxocariasis relies upon indirect arguments, e.g., the presence of otherwise unexplained symptoms along with blood eosinophilia and/or elevated levels of eosinophil cationic protein (ECP). This situation is far from ideal and more research should be carried out to solve this difficult problem.

Meningitis by Toxocara canis after ingestion of raw ostrich liver

Recently reports on toxocariasis are increasing by serodiagnosis in Korea. A previously healthy 17-yr-old boy complained of headache, fever, dyspnea, and anorexia. He showed symptoms and signs of eosinophilic meningitis with involvement of the lungs and liver. Specific IgG antibody to Toxocara canis larval antigen was positive in serum and cerebrospinal fluid by ELISA. He took raw ostrich liver with his parents 4 weeks before the symptom onset. His parents were seropositive for T. canis antigen but had no symptoms or signs suggesting toxocariasis. This is the first report of toxocariasis in a family due to ingestion of raw ostrich liver in Korea.

Pet roundworms and hookworms: a continuing need for global worming

Ascarids and ancylostomatids are the most important parasites affecting dogs and cats worldwide, in terms of diffusion and risk for animal and human health. Different misconceptions have led the general public and pet owners to minimize the importance of these intestinal worms. A low grade of interest is also registered among veterinary professions, although there is a significant merit in keeping our guard up against these parasites. This article reviews current knowledge of ascarids and ancylostomatids, with a special focus on pathogenicity, epidemiology and control methods in veterinary and human medicine.

Antagonistic activity of the fungusPochonia chlamydosporiaon mature and immatureToxocara caniseggs

In vitrotests were performed to evaluate the ability of 6 isolates of the nematophagous fungusPochonia chlamydosporiato infect immature and matureToxocara caniseggs on cellulose dialysis membrane. There was a direct relationship between the number of eggs colonized and the increase in the days of interaction, as well as between the number of eggs colonized and the increase in the concentration of chlamydospores (P<0·05). Immature eggs were more susceptible to infection than mature eggs. The isolate Pc-04 was the most efficient egg parasite until the 7th day, and showed no difference in capacity to infect mature and immature eggs in comparison to Pc-07 at 14 and 21 days of interaction, respectively. Isolate Pc-04 was the most infective on the two evolutionary phases of the eggs at most concentrations, but its ability to infect immature eggs did not differ from that presented by the isolates Pc-07 and Pc-10 at the inoculum level of 5000 chlamydospores. Colonization of infective larvae inside or outside the egg was observed in treatments with the isolates Pc-03, Pc-04, Pc-07 and Pc-10. The isolate Pc-04 ofP. chlamydosporiahas great biological capacity to destroy immature and matureT. caniseggs in laboratory conditions.

Transmission of Toxocara canis via ingestion of raw cow liver: a cross-sectional study in healthy adults

The aim of this study is to ascertain the relationship between ingestion of raw cow liver and Toxocara canis infection. A total of 150 apparently healthy adults were divided into 2 groups; 1 group consisted of 86 adults with positive results of Toxocara ELISA, and the other group of 64 adults with negative results. One researcher collected the history of ingestion of raw cow liver within 1 year and recent history of keeping dogs. Among 86 seropositive adults for T. canis, 68 (79.1%) had a recent history of ingestion of raw cow liver. Multivariate statistical analysis showed that a recent ingestion of raw cow liver and keeping dogs were related to an increased risk of toxocariasis (odds ratios, 4.4 and 3.7; and 95% confidence intervals, 1.9-10.2 and 1.2-11.6, respectively). A recent history of ingestion of raw cow liver and keeping dogs was significantly associated with toxocariasis.

Toxocara canis myelitis: clinical features, magnetic resonance imaging (MRI) findings, and treatment outcome in 17 patients

Toxocara myelitis is a rare disease. Few cases have been reported in the literature. Patients present with myelopathy, occasional eosinophilia in blood and cerebrospinal fluid (CSF), with abnormal signals on magnetic resonance imaging (MRI). In the current study we report 17 cases of isolated Toxocara myelitis from a single tertiary referral center in Lebanon, with description of the clinical presentation, laboratory data, MRI findings, and response to antihelminthic treatment. Clinical and laboratory data were collected for 17 patients who presented with evidence of spinal cord disease. The clinical presentation included sensory, motor, and autonomic dysfunction, predominantly in the lower extremities. Patients exhibited a subacute or chronic course; this was either slowly progressive or remitting-relapsing with mild to moderate disability. The patients underwent extensive blood and CSF workup as well as MRI of the spinal cord and brain. Only 2 patients had a high eosinophil count in the CSF, although blood eosinophilia was seen in 6 patients. All patients tested positive for Toxocara canis antibodies in the blood and CSF. MRI of the spinal cord revealed a single characteristic lesion in the spinal cord with fusiform enlargement that was isointense on T1-weighted images and hyperintense on T2-weighted images. Nodular enhancement was seen after gadolinium injection. Treatment with albendazole, with or without steroids, resulted in marked neurologic improvement and normalization of the MRI in all patients.The finding of a single inflammatory MRI lesion in the spinal cord with positive Toxocara canis serology in the blood and CSF in cases of subacute or chronic myelitis suggests the diagnosis of Toxocara myelitis, irrespective of the presence of eosinophilia. Antihelminthic treatment is associated with a good outcome.

Ocular toxocariasis in Korea

PURPOSE

To analyze the characteristics and clinical manifestations of clinically diagnosed and serologically confirmed ocular toxocariasis in patients.

METHODS

Thirty-three eyes of 33 patients diagnosed as having ocular toxocariasis at the Hallym University Medical Center between January 1999 and December 2008 were included in the study. The diagnosis of ocular toxocariasis was based on clinical features and confirmed serologically by enzyme-linked immunosorbent assay and immunoblotting. All patients were interviewed by using a structured questionnaire that included risk factors that might account for the introduction of Toxocara larvae. Demographics, social characteristics determined from the questionnaire, and clinical features were evaluated.

RESULTS

A total of 33 eyes of 33 patients were enrolled in this study: 24 (73%) patients were men, and mean patient age was 41.6 ± 11.0 years. Ten of 28 patients (36%) who responded to the questionnaire had a history of contact with pets, and 23 (82%) had a history of consuming raw food. The most common symptoms were blurred vision in 22 eyes (67%) and floaters in six eyes (18%). The toxocariasis was unilateral in all patients, and the inflammation was acute in two-thirds of the patients. In 17 eyes (52%), Toxocara granuloma was found in the peripheral retina. Nineteen eyes (58%) had visual acuity of 20/40 or better at presentation and improved significantly after treatment. Final visual acuity was 20/40 or better in 26 eyes (79%).

CONCLUSIONS

Ocular toxocariasis in Korea usually affects young adults to middle-aged men. The clinical manifestation is unilateral and presents as acute inflammation with a peripheral inflammatory mass. Visual prognosis with appropriate treatment is good.

Imaging of Toxocara canis larvae labelled by CFSE in BALB/c mice

Mice are used most often as a model for human toxocariasis caused by Toxocara canis larvae. Variety of symptoms developing during the infection reflects behaviour of the larvae, which are able to escape from the intestine and further invade and damage various host organs. In order to find an approach enabling observation on parasite behaviour in mouse in vivo, we used an epifluorescence method and a small animal imaging system (SAIS). Larvae of T. canis were labelled by carboxyfluorescein succinimidyl ester (CFSE) which incorporated on the parasite gastrointestinal tract. Following infection of BALB/c mice by CFSE-labelled larvae it has been observed that staining had no influence on viability and further migratory activity of the parasites through the host organs (the intestine, liver, lungs and brain) where they were detected by SAIS until day 17 p.i. In addition, the dye did not affect larval antigenic activity as well as the development of related immune response. Imaging of parasites labelled by CFSE, therefore, may represent a promising way to study behaviour of T. canis larvae in a paratenic host.

[A case of hepatic abscess caused by toxocara]

Toxocariasis is a helminozoonosis caused by the infection of a human host by the larva of Toxocara canis and Toxocara catis, which are common nematodes in dogs and cats, and occurs more frequently in school age children. Toxocariasis shows variable clinical manifestations including hepatomegaly, bronchial asthma, uveitis, central nervous system symptoms with peripheral eosinophilia and an increased total serum IgE level. However a hepatic abscess caused by toxocara infection in adults is rare. We experienced a case of heavy alcoholic patients with a hepatic eosinophilic abscess caused by toxocara infestation, which was confirmed by microscopic examination of liver biopsy, enzyme-linked immunosorbent assay test, abdominal CT and the ultrasonography findings.

Toxocariasis and ingestion of raw cow liver in patients with eosinophilia

Ingestion of raw animal liver has been suggested as a possible mode of infection of human toxocariasis. We evaluated the relationship between toxocariasis and the ingestion of raw meat in patients with eosinophilia of unknown etiology. The study population consisted of 120 patients presenting with peripheral blood eosinophilia (>500 cells/microliter or >10% of the white blood cell count). They were divided into 2 groups: 104 seropositive patients based on a Toxocara excretory-secretory IgG ELISA and 16 seronegative patients. While 25.0% of seronegative patients had a recent history of eating raw cow liver, 87.5% of seropositive patients had this history. Multivariate statistical analysis showed that a recent history of eating raw cow liver was related to an increased risk of toxocariasis. Collectively, it is proposed that raw cow liver is a significant infection source of toxocariasis in the patients with eosinophilia of unknown etiology.

Toxocariasis of the liver: visceral larva migrans

Toxocariasis is caused by dog ascarid, Toxocara canis, forming eosinophilic inflammation such as eosinophilic abscess or granuloma in the liver and lungs. The lesions move slowly and thus the disease is called as visceral larva migrans. On CT or MR imaging, hepatic lesions are seen as multiple, ill-defined, oval lesions that measure 1.0-1.5 cm in diameter. Sometimes, the lesion may be angular or trapezoid. The lesions are usually best seen on the portal venous phase in dynamic contrast-enhanced CT and MR imaging; the lesions are either not seen or only faintly seen on arterial and equilibrium phases. Either an enhancing rim or enhancing nodules are sometimes observed. On sonography, the lesions appear as multiple, small, oval hypoechoic lesions in the liver parenchyma. The lesions differ from metastatic nodules is as much as they have fuzzy margins, are uniform in size, non-spherical shape and are best seen on portal venous phase. On follow-up imaging, the lesions may improve, or sometimes a change positions, reflecting migration of larva in the liver, supporting the phenomenon of visceral larva migrans.

Histopathologic changes and larval recovery of Toxocara cati in experimentally infected chickens

This study was made to determine the distribution pattern of Toxocara cati larvae in chickens as a paratenic host and its potential zoonotic risk by consuming infected chickens. Two groups of chickens were fed with 1,000 and 3,000 embryonated eggs of T. cati. The chickens were necropsied 3, 7, 14, and 21 days postinfection. The liver, lungs, kidneys, spleen, small intestine, and half of all the striated muscles were digested for larval recovery. Squash method was used for brain. Larvae were recovered from the liver and brain of infected chickens with 1,000 embryonated eggs. Samples of these tissues were prepared for histopathologic studies. Experimental chickens exhibited hemorrhages in the liver, lungs, and kidneys on all days postinfections (dpi). White spots on the liver surfaces that showed necrotic foci, infiltration of eosinophils, and a few lymphocytes around necrotic areas were seen on 14 and 21 dpi. Remains of larvae were present in the liver on 14 dpi. Pathologic findings showed that larvae migrated in different organs of chickens. We suggest that chickens could be paratenic hosts, and human infection with T. cati might occur after consumption of raw or undercooked meat of infected chicken with T. cati.

Seroprevalence of Toxocara canis in sheep in Wales

Antibody levels to Toxocara canis L2 excretory/secretory antigens were examined by ELISA in 400 serum samples from sheep in Powys and Gwent, Wales. A positive OD value was set at the mean +/-3S.D. of 45 control samples. Seroprevalence increased with age. Seven percent and 13% of 6-month-old sheep showed positive OD values as did 16% of 10-month-old, 27% and 31% of 15-month-old and 47% of cull ewes. Analysis of variance showed a significant increase in ELISA OD values among the seropositive sheep with increasing age of sheep.

Toxocara-infestations in Austria: a study on the risk of infection of farmers, slaughterhouse staff, hunters and veterinarians

A total of 585 persons from several occupational groups (farmers, slaughterhouse staff, hunters, veterinarians) exposed to Toxocara infestations and 50 persons of a control group were tested for the presence of specific antibodies to the Toxocara canis antigen using an enzyme-linked immunosorbent assay and a western blot. Farmers showed the highest seroprevalence (44%), followed by veterinarians (27%), slaughterhouse staff (25%) and hunters (17%), whereas only 2% of the individuals of the control group were seropositive. Thus, the risk to Toxocara infestation is 39, 18, 16 and 9 times higher for farmers, veterinarians, slaughterhouse staff (some workers were part-time farmers) and for hunters, respectively, when compared to the control group. The main source of infection in rural areas seems to be (roaming) farm cats and dogs that have not been dewormed. The results are discussed with a view to potential risk factors and preventive measures, in terms of veterinary and human medicine.

Zoonotic risk of Toxocara canis infection through consumption of pig or poultry viscera

The potential zoonotic risk of Toxocara canis infections from consumption of swine or poultry viscera containing larvae was assessed using a pig model. Two groups of six pigs were fed either fresh swine viscera (group FS) or poultry viscera (FP) containing around 3500 Toxocara larvae. Another two groups of six pigs were fed swine viscera (PS) or poultry viscera (PP) preserved at 4 degrees C for 1 week. All pigs were necropsied 14 days after the exposure. Liver white spots were counted and T. canis specific IgG antibodies were measured by ELISA. Larval burdens were assessed in the mesenteric lymph nodes, liver, lungs, brain, tongue, and eyes. All recipient pigs exhibited several white spots on the liver surface and detectable antibody levels. Larvae were recovered predominantly from the lungs, but also from the mesenteric lymph nodes and the liver, a few larvae were found in the brain and tongue of the pigs. Two larvae were found in the eyes of two pigs in group FS. Mean percentages of total larval recoveries in groups FS, FP, PS, and PP were 75.3, 63.6, 42.6, and 18.8%, respectively. Significantly higher numbers of larvae were recovered from pigs given swine viscera than pigs given poultry viscera. The preservation at 4 degrees C for 1 week caused a significant reduction in the larval infectivity overall, nevertheless, the recoveries remained substantial. The fact that larvae migrating in swine or poultry organs and tissues have high infectivity in pigs even after preservation at 4 degrees C for 1 week, suggests that human infection with T. canis might easily occur following consumption of raw or undercooked dishes, either fresh or refrigerated, prepared from swine or poultry organs and tissues harbouring T. canis larvae.

[Toxocariasis: clinical and laboratory features in 54 patients]

OBJECTIVE

To describe the clinical and laboratory findings in children with toxocariasis.

METHODS

Fifty-four children with reactive serology to Toxocara determined by ELISA were prospectively identified between January 1998 and September 2000. The patients were divided into three groups: asymptomatic children (n 24), those with visceral larva migrans (n 16) and those with ocular larva migrans (n 14). Age, serology titers, and eosinophil count at diagnosis were compared among the groups. The patients received treatment with albendazole 10-15 mg/kg/day for 15 days or thiabendazole 25 mg/kg/day in two series of 7 days.

RESULTS

The clinical features were as follows: 24 children (44.4 %) were asymptomatic, pneumonitis was found in 9 (16.7 %), hepatomegaly in 6 (11.1 %), acute posterior uveitis in 5 (9.3 %), strabismus in 5 (9.3 %), leukocoria in 4 (7.4 %), fever in 3 (5.6 %). There was 1 case of keratitis, 1 of cataracts, 1 of myocarditis and 1 case of pneumonia with pleural effusion. Some patients showed more than one clinical feature. Four children experienced loss of vision in the affected eye. No differences in age or serology titers were found among the groups. Eosinophil count was lower in the group with ocular larva migrans than in the other groups (p < 0.001). Children with active disease showed clinical improvement and a 70.4 % decrease in eosinophilic count one year after treatment. Serological titers showed an unpredictable pattern during the follow-up.

CONCLUSIONS

Most of the infected children were asymptomatic. In the post-treatment follow-up, clinical improvement and a decrease in eosinophilic count were observed. Further studies are needed to evaluate the efficacy of treatment, especially in asymptomatic children.

Human toxocariasis and direct contact with dogs

Toxocariasis in man is traditionally thought to be contracted through the ingestion of eggs from contaminated soil. The disease may manifest itself in different syndromes such as ocular larval migrans, visceral larval migrans and covert toxocariasis. This paper assesses the evidence for the soil contamination hypothesis and proposes that direct contact with dogs may provide a better explanation of the epidemiology of the disease. Hair was collected from 60 dogs from various places in Ireland and the UK and examined for the presence of Toxocara canis eggs. T. canis eggs were found in the hair of 25 per cent of the dogs; in total, 71 eggs were recovered, of which 4.2 per cent were embryonated and 23.9 per cent were embryonating. The maximum densities of the embryonating and embryonated eggs were 180 and 20 eggs per gram of hair, respectively, much higher than the densities reported for soil samples. It is suggested that dogs infected with T. canis may infect people by direct contact.

Treatment of ocular toxocariasis with albendazole

The purpose of this study was to evaluate the efficacy of combined albendazole and steroid treatment for uveitis caused by Toxocara canis in immunocompetent patients. Five patients (7 eyes) with ocular larva migrans syndrome (OLM) were used in this study. Toxocariasis was suspected based on clinical manifestations and confirmed by anti-toxocara IgG and Western blot analysis. Systemic albendazole (adults: 800 mg b.i.d.; children: 400 mg b.i.d.) was given in conjunction with steroids. Visual acuity before and after therapy, inflammatory response, side effects and toxicity were evaluated. Treatment resulted in an improved visual acuity in all patients. Mean initial Snellen visual acuity was 20/40, and mean final acuity was 20/20. There were no recurrences of uveitis throughout the observation period (average: 13.8 months; range: 3 days to 24 months). These findings suggest that albendazole, in combination with systemic steroids, is a useful regimen to treat ocular larva migrans syndrome.

Highlights of human toxocariasis

Human toxocariasis is a helminthozoonosis due to the migration of Toxocara species larvae through human organism. Humans become infected by ingesting either embryonated eggs from soil (geophagia, pica), dirty hands or raw vegetables, or larvae from undercooked giblets. The diagnosis relies upon sensitive immunological methods (ELISA or western-blot) which use Toxocara excretory-secretory antigens. Seroprevalence is high in developed countries, especially in rural areas, and also in some tropical islands. The clinical spectrum of the disease comprises four syndromes, namely visceral larva migrans, ocular larva migrans, and the more recently recognized "common" (in adults) and "covert" (in children) pictures. Therapy of ocular toxocariasis is primarily based upon corticosteroids use, when visceral larva migrans and few cases of common or covert toxocariasis can be treated by anthelmintics whose the most efficient appeared to be diethylcarbamazine. When diagnosed, all of these syndromes require thorough prevention of recontamination (especially by deworming pets) and sanitary education.

[The association between human toxocariasis and pyogenic abscesses]

The association between hepatic abscesses and schistosomiasis mansoni was confirmed by clinical and experimental studies. Other parasites may cause systemic immunologic changes and local structural alterations in the affected organs that can facilitate the seeding of these areas by bacteria. Tropical pyomyositis, pyogenic liver and renal abscesses are frequent diseases in tropical areas. The visceral larva migrans syndrome is caused by the presence, in the human body, of larvae of worms that have other animals as their definitive host, most commonly being caused by Toxocara canis. The larvae migrate to various body organs leading to many inflammatory reactions in the form of granuloma and tissue necrosis. In this review we discuss the possible host-parasite-bacteria interactions that would favour the formation of abscesses in the organs involved by the larva of T. canis and present preliminary results of a clinical and experimental study undertaken during the last four years to define the role of this parasite in the pathogenesis of the abscesses.

Visceral larva migrans and tropical pyomyositis: a case report

We report a case of tropical pyomyositis in a boy who presented with a severe febrile illness associated with diffuse erythema, and swelling in many areas of the body which revealed on operation extensive necrotic areas of various muscles that required repeated débridement. The patient gave a history of contact with dogs, and an ELISA test for Toxocara canis was positive. He also presented eosinophilia and high serum IgE levels. Staphylococcus aureus was the sole bacteria isolated from the muscles affected. We suggest that tropical pyomyositis may be caused by the presence of migrating larvae of this or other parasites in the muscles. The immunologic and structural alterations caused by the larvae, in the presence of concomitant bacteremia, would favour seeding of the bacteria and the development of pyomyositis.

Aspects of Toxocara epidemiology: human toxocarosis

Toxocarosis is the clinical disease in man caused by infection of zoonotic roundworms of dogs and cats, Toxocara canis and T. cati. In this review the mode of transmission to the human by oral ingestion of Toxocara eggs from the environment is discussed. T. cati seems to play a more important role than generally suggested. Direct contact with animals is not considered a potential risk because embryonation of excreted Toxocara ova requires a minimum of 2 weeks. For the same reason there is no relationship expected between infection and exposure to dogs and cats in the household. Children more frequently have clinical symptoms because of the closer contact with contaminated soil in yards and sandpits, the lack of hygiene, and because of eating dirt. Toxocara larval migration in the body can cause various clinical syndromes. Visceral larva migrans, ocular larva migrans, and covert toxocarosis are described. Serodiagnostic techniques are reliable tools to detect antibodies or antigens. Systemic treatment with anthelmintics is described but can result in hypersensitivity reactions caused by dying larvae. For ocular lesions, laser photocoagulation and corticosteroid therapy are described. Preventive measures consist of preventing contamination of the environment with Toxocara eggs and for education of pet owners and non-pet owners to increase awareness about potential zoonotic hazards. Veterinary practitioners, general practitioners, and public health agencies should therefore provide sufficient information and advice.