Cerebral Toxocariasis as a Cause of Epilepsy: A Pediatric Case.

Toxocarosis is the consequence of human infection by Toxocara spp. larvae and is one of the most common ascarioses, not only in developing countries, but also in the European region, where its prevalence reaches 14%. Due to their particular behavior, children are at higher risk of this parasitic infection, whose clinical features depend on the localization of the Toxocara larvae. Neurotoxocariasis is very uncommon in children and may take different forms depending on the underlying physiopathologic process: immune reaction against the parasite antigens, vasculitis, treatment complications, or, very rarely, brain localization of Toxocara spp. larvae. The association between neurotoxocariasis and the onset of childhood epilepsy has been postulated but is still debated. Moreover, a Toxocara spp. abscess causing epileptic seizures in children has been rarely described, especially in western countries. Hereby we present a 9-year-old patient with a new diagnosis of epilepsy definitely secondary to brain abscess due to the localization of Toxocara canis larvae. Diagnosis was confirmed by neuroimaging and serological test. The successful treatment with albendazole and steroids was documented with a close and long-term clinical and neuroradiological follow-up. Our experience confirms that every case of cryptogenetic epilepsy in children deserves a neuroimaging study and, in case of cystic images, Toxocara serology is mandatory to avoid further unnecessary invasive diagnostic investigations and to set the specific drug therapy.

Matrix metalloproteinases activation in Toxocara canis induced pulmonary pathogenesis.

BACKGROUND: Toxocara canis, a source of visceral larva migrans, causes toxocariasis and induces respiratory symptoms. The reasons by which the pulmonary pathological alteration in the lungs infected with T. canis remain unclear. METHODS: The involvement of the pulmonary pathological alteration by histology, enzyme activity, and Western blot analysis in the lungs of BALB/c mice after the infection of 2000 embryonated eggs. RESULTS: The pathological effects gradually increased after the infection culminated in severe leukocyte infiltration and hemorrhage from days 4-14 post-inoculation. Gelatin zymography using substrate showed that the relative activity of matrix metalloproteinase (MMP) -9 and MMP-2 significantly increased in T. canis-infected mice. Western blot analysis indicated that the MMPs protein level of fibronectin monomer significantly increased in T. canis-infected mice compared with that in uninfected control. T. canis larvae mainly initiated leukocyte infiltration and hemorrhage in the lungs. CONCLUSION: These phenomena subsequently induced the activities of MMPs in parallel with the pathological changes in early stage pulmonary inflammation. In conclusion, T. canis larval migration activated the MMPs and caused pulmonary pathogenesis.

Dispersion and infectivity of Toxocara canis eggs after passage through chicken intestine.

Toxocariasis is an important, but neglected, worldwide zoonosis. It is considered a primarily soil-transmitted disease, but food-borne transmission has been associated with the consumption either of raw or undercooked meat of paratenic hosts, including birds. Despite the number of experimental studies carried out to evaluate the behavior of Toxocara spp. larvae in birds, their role in the dispersion of eggs into the environment remains unclear. Thus, this study aimed to evaluate the potential of broiler chickens to release Toxocara canis eggs into the environment, and the infectivity of eggs after passage through the intestine. Forty commercial broiler chickens, aged 60 days, were randomly distributed into three groups. Groups 1 (n = 16) and 2 (n = 16) were orally infected with 5000 embryonated and 5000 unembryonated T. canis eggs, respectively. Group 3 (n = 8) served as a control. Following infection, fecal samples from each chicken were examined using a centrifuge-sedimentation technique. At 24-h, 72-h, and 7-day post-infection (PI), four chickens each from the G1 and G2 groups, and two from the G3 group were killed. After euthanasia, the intestinal content and liver were collected for recovery of T. canis larvae. Results revealed that broiler chickens have the potential to disperse both embryonated and unembryonated T. canis eggs, following 2- to 6-h PI. In addition, the eggs shed into the feces of the G2 birds, after incubation in laboratorial conditions, were infective when they were tested in a bioassay using mice. In conclusion, broiler chickens have the potential of dispersing Toxocara spp. eggs into the environment and the eggs passed through the intestine are infective after being incubated in experimental conditions.

The somatic proteins of Toxocara canis larvae and excretory-secretory products revealed by proteomics.

Toxocariasis is a widespread helminth infection of dogs and cats, caused by Toxocara canis and Toxocara cati larvae, respectively. Toxocara spp. can cause zoonotic infections in humans by invading tissues and organs causing pathology. Toxocara spp. larvae release excretory-secretory molecules (TES) into the body of their host that are fundamental to the host-parasite interaction and could be used as targets for novel diagnostics and vaccines. In the present study, we identified 646 T. canis proteins from TES and larval extract using 1D-SDS PAGE followed by mass spectrometry. A wide range of proteins was identified that may play a role both in the induction of the host immune response and host pathology, and in parasite metabolism and survival. Among these proteins there are potential candidates for novel diagnostics and vaccines for dogs and cats toxocariases.

Acometimento visceral e ocular simultâneo em infecção por toxocara canis acompanhado de farmacodermia / Concurrent visceral and ocular involvementin toxocara canis infection and pharmacodermia

A toxocaríase humana é uma infecção parasitária de distribuição mundial causada pelos nematelmintos das espécies Toxocara canis e Toxocara cati, presentes no intestino do cão e do gato, respectivamente. Clinicamente, na maioria das vezes, é assintomática, porém pode apresentar-se de duas formas: visceral ou ocular. Visceralmente, gera uma síndrome hipereosinofílica crônica, acompanhada por leucocitose e hepatomegalia, podendo ocorrer algum grau de infiltrado pulmonar e febre. Na toxocaríase ocular, ocorre uveite intermediária ou posterior, podendo haver formação de granuloma, geralmente unilateral. O acometimento misto é raro, o que motivou este relato. Trata-se de paciente de 19 anos, sexo masculino, que apresentou como sintoma inicial perda da acuidade visual em olho esquerdo. Recebeu tratamento, sem melhora, com sulfametoxazol + trimetoprima e corticoide, fazendo farmacodermia. Evoluiu com diarreia, febre, dor abdominal e hepatoesplenomegalia. Descartadas infecções agudas por toxoplasmose, sífilis, vírus da imunodeficiência humana (HIV), citomegalovirose e dengue; apresentou leucocitose com hipereosinofilia. Foi solicitada sorologia para toxocaríase, confirmando esta infecção. Após o tratamento, apresentou completa remissão dos sintomas. O objetivo aqui foi debater os fatores confundidores, diagnósticos diferenciais, necessidade de exames complementares específicos e conduta terapêutica, de acordo com o quadro clínico.(AU)

Human toxocariasis is a worldwide parasitic infection caused by ascarid nematodes species: Toxocara canis and Toxocara cati, that are present in the intestines of dogs and cats, respectively. Although clinically, most human infections are asymptomatic, two syndromes of human toxocariasis are recognized: visceral and ocular. The visceral form is a hypereosinophilic syndrome accompanied by leukocytosis, hepatomegaly, some degree of pulmonary infiltrate and fever. In ocular toxacariasis there is intermediate or posterior uveitis, and there may be granuloma formation, usually unilateral. The simultaneous involvement of the two forms is rare, which is what, motivated this report. It is a 19-year-old male patient who initially presented loss of visual acuity in the left eye. He received treatment, without improvement, with sulfamethoxazole-trimethoprim and corticoid, causing a pharmacodermia. He developed diarrhea, fever, abdominal pain and hepatosplenomegaly. It was discarded acute infections by toxoplasmosis, syphilis, human immunodeficiency virus (HIV), cytomegalovirus and dengue. The patient also manifested leukocytosis with hypereosinophilia. Serological testing for toxacariasis was requested, diagnosing the infection. After treatment, he progressed with full symptoms remission. The aim of this study was to discuss confounding factors, differential diagnoses, the need for specific complementary exams and therapeutic management, according to the clinical aspects.(AU)

Toxocara canis myelitis involving the lumbosacral region: a case report.

CONTEXT: Toxocara canis is a parasite known to cause visceral larva migrans. The infection rarely affects the central nervous system but there have been several reports of myelitis caused by visceral larva migrans due to Toxocara canis. In previous reported cases, the lesions were located in the thoracic or cervical spinal cord. To the best of our knowledge, this is the first report of a lesion involving the lumbosacral region. FINDINGS: A 60-year-old man developed weakness and dysesthesia in the lower limbs. The symptoms resolved spontaneously, but recurred after five months. One month later, the patient developed pollakiuria and constipation. He was a dog owner and frequently ate raw chicken meat and beef liver. Sagittal T2-weighted image (T2WI) showed swelling and hyperintensity in the spinal cord from T10 to the lumbosacral region and focal nodular enhancement on the posterior segment of the lumbar spinal cord. Blood cell counts showed slight eosinophilia and elevated serum immunoglobulin E level. Cerebrospinal fluid examination showed slight pleocytosis with eosinophilia. Enzyme-linked immunosorbent assay showed high levels of anti-Toxocara antibodies in the serum and cerebrospinal fluid. In addition, confirmatory test by Western blot was positive. The patient was initially treated with intravenous methylprednisolone with slight improvement in muscle weakness. Albendazole was added with a second course of intravenous methylprednisolone. The muscle weakness in the lower limbs improved considerably, and swelling and hyperintensity on T2WI almost disappeared. CONCLUSION: Our results suggest that Toxocara canis myelitis cannot be discounted even if the myelitis involves the lumbosacral region.

Sero-Epidemiology of Toxocara Canis Infection in Children Attending Four Selected Health Facilities in the Central Region of Ghana.

OBJECTIVE: The study determined the seroprevalence of Toxocara canis infection among children attending four selected health facilities in the Central Region of Ghana. DESIGN: Cross-sectional study. METHOD: Sera from 566 children aged 1-15 years attending four selected health facilities in the Central Region of Ghana between July and September 2012 was used in a Toxocara excretory-secretory antigen-based ELISA to detect serum IgG. A short questionnaire was designed to obtain data on respondents as to age, gender, educational level, locality of residence, habits of washing of fruits, vegetable and hands before eating, keeping of pet (dogs or cats), and history of playing with soil and pets. Clinical information was also collected. Associations between sero-positivity and age group, gender, risk factors, educational level and other variables were determined by Chi square test. RESULTS: The overall sero-prevalence was 53.5% (n=566). Age, educational level and hospital visited were significantly associated with sero-positivity (p< 0.05). Children with history of playing with soil (χ(2)=9.03, p=0.003), pet-keeping (χ(2)=14.77, p=0.001) and not washing hands with soap before eating (χ(2)=5.82, p=0.016) were significantly associated with sero-positivity. CONCLUSION: The sero-prevalence of T. canis infection in children in the study was high. The children should be educated to desist from risk factors such as playing with soil and pets and be encouraged to ensure proper personal hygiene.

[SOME CLINICAL AND CYTOKINE FEATURES OF THE CLINICAL COURSE OF RECURRENT RESPIRATORY SYSTEM DISEASES IN CHILDREN WITH THE TOXOCARIASIS INVASION].

The aim of the present study was to analyze clinical and cytokine features of recurrent respiratory system diseases in children with toxocariasis. 50 children aged 1 to 17 years (mean age - 10±5 years) with recurrent current of respiratory system disorders were studied. During the survey such clinical manifestations of the respiratory system disorders as obstructive bronchitis (50%), bronchial asthma (30%), pneumonia (10%) and laryngotracheitis (10%) have been revealed. Statistical analysis of the results was performed using the software package STATISTICA 6.1 (SNANSOFT). We have shown that the disorders of respiratory system in case of toxocariasis invasion often occur with severe intoxication and bronchial obstruction syndromes, temperature reaction, respiratory insufficiency and hepatomegaly. A prolonged course of the disease has been noted. "Inflammatory" indicators of general blood analysis, such as leukocytosis and increased of ESR have been recorded in patients with respiratory system disorders in children with T.canis infection significantly more often, significant "allergic" laboratory changes were in the form of eosinophilia. High average levels of pro-inflammatory IL-6, as well as low levels of IL 5 have been determined in children suffering from the respiratory system disorders and with toxocariasis invasion in the anamnesis. The obtained findings require further study.

Toxocaríase experimental em hamster / Experimental toxocariasis in hamsters

INTRODUÇÃO: Toxocaríase é uma infecção parasitária de distribuição global, causada pela fase larval de Toxocara spp. Os hospedeiros naturais são cães e gatos, nos quais o parasita completa o ciclo chegando a fase adulta. Outros hospedeiros podem ser infectados pela fase larval do parasita, após ingestão de ovos embrionados do solo, mãos contaminadas, fomites, ou ingestão de carne ou vísceras de animais infectados. Em hospedeiros paratênicos o parasita não completa o ciclo, invadindo em estágio larval vísceras ou outros tecidos, onde podem sobreviver e induzir a patologia. O presente estudo teve como objetivo caracterizar o hamster (Mesocricetus auratus), como modelo experimental de toxocaríase, inicialmente através do estudo das lesões histopatológicas em fígado, pulmão e rim. A caracterização da resposta imunológica do modelo, foi feita através do estudo de citocinas envolvidas nas respostas Th1 e Th2, e foi sugerida uma correlação entre alterações glomerulares e depósitos de complexos antígenos-anticorpo pré-formados na circulação. MÉTODOS: Hamsters foram inoculados com ovos embrionados de Toxocara canis, e mantidos no biotério do Instituto de Medicina Tropical de São Paulo. O estudo histopatológico foi desenvolvido utilizando-se cortes parafinados corados por hematoxilina e eosina. Para detecção de antígenos nos tecidos foram realizadas reações imunohistoquímicas, utilizando-se anticorpo monoclonal e policlonal anti- Toxocara canis. Utilizando-se o soro dos animais infectados e animais controle, foi realizada pesquisa de antígeno e anticorpo por ELISA. Para pesquisa de imunoglobulinas IgG e IgM e complemento, foram utilizados cortes congelados de rins para realização de reação de Imunofluorescência. Fragmentos de rins foram incluídos para utilização em microscopia eletrônica, para detecção de antígenos de toxocara e de imune complexos. Para caracterização de resposta imunológica foram estudadas citocinas envolvidas na resposta Th1 e Th2 por técnica de...

INTRODUCTION: Toxocariasis is a parasitic infection of global distribution, caused by the larval stage of Toxocara spp. The natural hosts are dogs and cats, in which the parasite completes the cycle reaching adulthood. Other hosts can be infected with the larval stage of the parasite, after ingestion of embryonated eggs from the soil, contaminated hands, fomites, or ingestion of meat or viscera of infected animals. In paratenics hosts the parasite not complete the cycle, encroaching on larval stage in viscera or other tissues where they can survive and induce pathology. The present study aimed to characterize the hamster, Mesocricetus auratus, as experimental model of toxocariasis, initially through the study of histopathological lesions in the liver, lung and kidney. The characterization of immune response model, was made through the study of cytokines Th1 and Th2 responses involved, and a correlation was suggested between glomerular changes and antibody-antigen complexes deposits preformed in the circulation. METHODS: Hamsters were inoculated with embryonated eggs of Toxocara canis, and kept in the bioterium of the Institute of Tropical Medicine of the São Paulo. The histopathologic study was developed using paraffin slides stained by hematoxylin and eosin. For detection of antigens in tissues immunohistochemistry reactions were performed using monoclonal and polyclonal anti-Toxocara canis sera. Using the serum of infected and control animals, search has been carried out of antigen and antibody by ELISA. For the search of immunoglobulins IgG, IgM and complement, were used slides prepared from frozen fragments of kidneys and a immunofluorescence reaction. Fragments of kidneys were included for electron microscopy to detect antigens of Toxocara and immune complexes. For characterization of Th1 and Th2 response cytokines involved were detected by RT-PCR technique. RESULTS: Histopathological findings demonstrated since the beginning of the...

Toxocara spp. infections in paratenic hosts.

The zoonotic roundworms Toxocara canis and T. cati are not only present worldwide in their definitive hosts; they also frequently occur in other animal species, including humans. In those so-called paratenic hosts, the larvae do not develop into the adult stage, but rather migrate throughout the somatic tissue and persist as infectious L3 stage for extensive periods. Those arrested larvae may lead to severe inflammatory reactions and consequently to a wide range of pathological and clinical manifestations. However, the infected paratenic hosts also constitute a potential source of infection for the definitive hosts or humans who may also function as paratenic hosts. In the present review, current knowledge of larval migration in a variety of possible paratenic hosts is summarized including variations of migration routes and susceptibilities. Furthermore, information about the clinical and pathological changes for the presented species and possible consequences of the somatic migration of larvae, i.e. the resulting tissue damage as well as adverse host reactions to arrested larvae are reviewed. There are still many questions unanswered regarding larval behaviour in hosts other than their definitive host. Therefore, it is of great importance to continue further elaboration on the biology of Toxocara spp. to prevent further spreading of larvae in both the paratenic and the definitive host.

Analysis of serum cytokine levels in children with chronic cough associated with Toxocara canis infection.

Toxocara infection is associated with an increased prevalence of airway symptoms and may be a possible aetiologic agent of chronic cough. The occurrence of toxocariasis in Hungary is mild and/or sporadic. The purpose of this study was to investigate the levels of serum cytokines (IL-1, IL-2, IL-4, IL-5, IL-6, IL-10, IL-13, IFN-gamma and TNF-alpha) and total IgE, the blood eosinophil count, the results of skin prick and non-specific bronchus provocation tests in Toxocara-seropositive children with chronic cough relative to those in healthy controls. The patients exhibited moderate eosinophilia, significantly elevated levels of serum total IgE, IL-6, IL-10, IL-13 and IFN-gamma, and higher skin reactivity to common allergens, whereas the bronchial hyperreactivity was similar in the two groups. The protective proinflammatory cytokines (IL-6, IFN-gamma and IL-13) in association with the anti-inflammatory cytokine (IL-10) were simultaneously increased in Toxocara-infected children with chronic cough. During infections, the activation and suppression of immune processes occur simultaneously and cytokines of Th1/Th2 and regulatory T cells contribute to the regulation of the immune response evoked by helminth infections (depending on the parasite load, the timing and duration of the infection and the status of the host immune system).

Comparative ultrastructural studies of the alterations to mouse lung parenchyma during Trichinella spiralis or Toxocara canis infection.

Trichinella spiralis and Toxocara canis larvae migrated through the lung and induced many alterations in the lung parenchyma. Using electron microscopy, we identified and described the histopathological changes. These changes resulted from mechanical damage or from local inflammatory reactions provoked by larvae. The pattern of changes was described between 6 and 12 days post-infection (DPI) with T. spiralis larvae, and between 21 and 28 DPI with T. canis. The ultrastructural studies demonstrated that T. spiralis larvae migrating through the lungs evoked mainly destruction of type I epithelial cells, destruction of lamellar bodies of epithelial cells or extracellular alveolar lining layer. The severity of these changes was dependent on the number of infective larvae (400 or 800 T. spiralis larvae) and possibly the result of mechanical damage in the lung parenchyma. In contrast, infection with T. canis larvae initiated mainly eosinophilic perivasculitis and vasculitis as well as macrophage accumulation in the lung, which were additionally impacted by numerous crystalloid inclusions in macrophages. Trichinella spiralis larvae and T. canis larvae induced different pathological changes in the lungs of infected mice.

Epidemiological situation of toxocariasis in Iran: meta-analysis and systematic review.

Toxocariasis is the clinical terms applied to infection of human with ascarid nematodes in the order Ascaridida, named toxocara canis and toxocara cati. It is transmitted from dog and cat to humans. Accidental ingestion of parasite eggs causes ocular and visceral larva migrans in human. The aim of this study is to study epidemiology of toxocariasis in Iran using meta-analysis and systematic review. Using main key words of toxocariasis including epidemiology, Toxocara spp. Iran, dog and cat in databases such as SID, Google scholar, Pubmed, Magiran and Iranmedex, a number of 50 articles was extracted. A number of 27 articles of them were eligible for meta-analysis. Data extracted from articles and archived in excel software for analysis. Variance of each study obtained using binomial distribution. Heterogeny of studies surveyed using Cochrans Q test. Data analyzed using Random Effect Model test. Overall prevalence of toxocariasis obtained 21.6% in Iran. In total of 27 articles, 6911 samples including 1543 carnivores, (13 articles), 4569 human sera (10 articles) and 799 soil samples (4 articles) has been investigated. Seropositivity for human toxocariasis 15.8% (95%CI, 9.2-22.5), soil contamination for Txocara spp. eggs 21.6% (95%CI,-1.6-44.8) and dogs and cats infections with adult worm 26.8% (95%CI, 18.7-36.8) was obtained. Results of this study show that prevalence of toxocariasis has a growing trend in Iran. It could be decreased using education, culture making and giving information to people.

Evaluation of the immunosuppressive effect of cyclophosphamide and dexamethasone in mice with visceral toxocariasis.

Visceral toxocariasis is a serious public health problem with a cosmopolitan distribution. Children are susceptible due to their immature immune system and high risks of infection. Nevertheless, the few completed studies about immunosuppression have had controversial results. To evaluate the effect of two immunosuppressive drugs on the larval burden of Toxocara canis, four groups of ten Swiss strain mice each were inoculated on day 0 with 1,200 embryonated T. canis eggs. Fifteen days before the experimental infection, group 1 (control) was treated via intraperitoneal injection (IP) with sterile distilled water and groups 2 and 3 were treated with dexamethasone (DEX) at 1 and 5 mg/kg/day, respectively. Additionally, group 4 was treated IP with cyclophosphamide (CY) at 50 mg/kg at two times per week for 2 weeks. Sixty days following infection, the mice were euthanised to recover the larvae by means of the tissue digestion technique. The levels of antibodies detected by indirect ELISA were not associated with the larval burden. Administration of CY (50 mg/kg) and DEX (5 mg/kg) resulted in an increase of the larval burden of 162.1% and 50.8%, respectively, in relation to the control group. These two treatments, especially CY (50 mg/kg), promoted immunosuppression and the establishment of a significant larval burden, supporting its further utilisation in studies related to immunosuppression in visceral toxocariasis.

Efficacy of emodepside plus toltrazuril (Procox(®) oral suspension for dogs) against Toxocara canis, Uncinaria stenocephala and Ancylostoma caninum in dogs.

The efficacy of emodepside plus toltrazuril (Procox® oral suspension for dogs) against different species of gastrointestinal nematodes (Toxocara canis, Ancylostoma caninum, Uncinaria stenocephala) was evaluated in nine randomised,blinded and placebo-controlled laboratory studies in naturally or experimentally infected dogs. The product was used at the proposed minimum dose of 0.45 mg emodepside and 9 mg toltrazuril per kg body weight. Efficacy was calculated based on worm counts after necropsy. Worm burdens in the control dogs ranged between 0 and 409 worms of the respective stage for T. canis and between 4 and 655 worms for hookworms. The studies demonstrated 100 % efficacy of emodepside/toltrazuril suspension against mature adult, ≥ 94.7 %efficacy against immature adult and 99.3 % efficacy against the L4 larval stage of T. canis. The efficacy against mature adult A. caninum was ≥ 99.5 % and the efficacy against mature adult U. stenocephala was 100 %. All differences between treatment and control groups were statistically significant and no gender effect was found. It can be concluded that the emodepside/toltrazuril suspension represents a safe and highly effective product in dogs with nematode (T. canis, hookworms) infection.

Toxocara canis larvae reinfecting BALB/c mice exhibit accelerated speed of migration to the host CNS.

Using a small animal imaging system, migratory activity of Toxocara canis larvae stained by carboxyfluorescein succinimidyl ester (CFSE) was observed post primary infection (PPI) and post reinfection (PR) of BALB/c mice. Each infection was performed with 1,000 larvae per mouse. Primary infections were performed with labeled larvae, while for challenge infections the reinfecting larvae were stained by CFSE. The worm burden in mouse organs was determined during a period from 6 h to 21 days and 4 months PPI and PR. In comparison with primary infections that led to the first larvae appearance in the brain after 60 h, greatly accelerated migration of the parasites administered 3 weeks PPI to the CNS and eyes of challenged mice was noted-in both organs the larvae appeared 6 h PR. In all challenged mice, reinfecting larvae prevailed in the resident parasite population. Preliminary experiments with Toxocara cati larvae also revealed early brain involvement in primarily infected mice. Staining of T. canis larvae by CFSE had no effect on the development of a humoral antibody response against T. canis excretory-secretory antigens. In ELISA, elevated levels of specific IgG and IgG1 were noted on day 14 PPI and the levels of antibodies increased till the end of experiment. Reinfection induced an increase in the levels of both antibodies. In terms of optical density, IgG1 antibodies gave higher values in all sera examined. In ELISA for IgG antibodies, an increase in the avidity index of around 50% was detected 1 month PPI; higher-avidity antibodies were also detected in sera of reinfected animals.

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.

Larval development of Toxocara canis in dogs.

The parasitic roundworm Toxocara canis is present in dog populations all over the world. Due to its zoonotic potential, this roundworm is of special interest not only for veterinarians, but also for medical practitioners. In the present review, current knowledge of infection routes and the subsequent development of larvae within the canine host is summarised. Furthermore, information about the clinical, pathological, enzymatic, haematological and histopathological changes was collected, giving a broad overview of current knowledge of the infection. Although the data collected over the years give an idea of what happens during the larval development of T. canis, many questions remain open. Nevertheless, it is important that we continue our efforts to further understand the biology of this versatile and compelling parasite and try to improve and optimise strategies to prevent the infection in dogs and thereby to protect humans from this infection.

Biochemical and immunopathological changes in experimental neurotoxocariasis.

Toxocariasis is a widespread soil-transmitted parasitic disease. Toxocara canis larvae migrate through the tissues with a special predilection for the central nervous system. Recently, neurotoxocariasis is being diagnosed in humans with increasing frequency due to improved diagnostic tools. The present study aimed at exploring the biochemical and immunopathological alterations in the brain in experimental T. canis infection. For this purpose, 75 Toxocara-infected mice were sacrificed at 2, 5, and 16 weeks post-infection. The brains were removed and assayed for total larval count, pro-inflammatory cytokines (TNF-alpha, IL-6), and central neurotransmitters (gamma-aminobutyric acid, glutamate, dopamine, norepinephrine, and serotonin). Brain sections were also stained for histopathological study, and for assessment of the expression of inducible nitric oxide synthase (iNOS), and glial fibrillary acidic protein (GFAP) by immunohistochemical methods. We found that larval recovery showed progressive increase over the course of infection. Furthermore, the infected mice displayed increased expression of pro-inflammatory cytokines and iNOS, as well as significant disturbances in neurotransmitter profile. Astrocytic activation, evidenced by enhanced expression of GFAP, was also manifest in infected animals. These changes were maximal in the chronic stage of infection or intensified over time. In conclusion, experimental neurotoxocariasis is associated with significant biochemical, immunological, and pathological changes.