Visceral larva migrans. A review and reassessment indicating two forms of clinical expression: visceral and ocular

Seroepidemiology of human toxocariasis in North Africa

Seroprevalence studies on human toxocariasis help to assess the burden and the morbidity associated with this zoonosis. This review searched the seroprevalence studies and case reports in six North African countries: Algeria, Egypt, Libya, Morocco, Sudan and Tunisia, since 1990. The search also included studies on the environmental factors related to the risk of transmission. Most of the published epidemiological studies were done in Egypt. Cross-sectional and case-control studies in Egypt demonstrated that toxocariasis is a significant zoonosis that could be associated with conditions like bronchial asthma allergies and certain neuropsychiatric disorders. The population at risk of this infection includes all ages, both genders, in contact with dogs, resident in rural areas with poor housing conditions. The publications from Tunisia, Morocco and Algeria are limited to case reports and retrospective analyses of cases, but the disease is probably under-diagnosed in these three countries. There are no published reports on human toxocariasis in Libya and Sudan during the period covered by the review. Animal studies confirm high infection rates of dogs with Toxocara canis in North Africa. There is also evidence of wide-spread contamination of soil and water with Toxocara spp. eggs. Moreover, the use of untreated wastewater for irrigation in parts of North Africa could be a source of contamination of agricultural products with eggs of Toxocara spp. Population-based studies on human toxocariasis are recommended, using standardized diagnostic tests. These surveys should also assess risk factors to guide preventive measures.

Larva migrans in India: veterinary and public health perspectives

Despite an important public health problem in developing world like India, larva migrans remains a neglected zoonosis. Cutaneous larva migrans, Visceral larva migrans, and Ocular larva migrans are the important clinical manifestations seen in humans in India. Although many nematode parasites have the ability to cause the infection, the disease primarily occurs due to Ancylostoma caninum and Toxocara canis. Presence of the infection in dogs is an indirect indication of its incidence in humans in endemic regions. In India, sporadic cases of this neglected but important parasitic zoonosis are the main implications of lack of diagnostic methods and under-reporting of human cases. Tropical climate in addition to overcrowding, poor hygiene and sanitation problems, stray dogs, open defecation by dogs and improper faecal disposal are the important factors for persistence of this disease in the country. Sanitary and hygienic measures, improved diagnostic techniques and surveillance programme in dogs as well as humans should be adopted for its effective control. Comprehensive collaborative efforts by physicians and veterinarians are required to tackle this problem in order to attain optimal health for humans, animals and the environment. Moreover, recognition of larva migrans as an important public health problem is the most important step to combat this neglected disease in developing countries like India.

Protective and risk factors for toxocariasis in children from two different social classes of Brazil

The aim of this study was to analyze the prevalence of Toxocara spp. antibodies in children from two different socioeconomic classes in the Presidente Prudente municipality, São Paulo State, Brazil, and the protective and risk factors associated with toxocariasis. One hundred and twenty-six middle-class (MC) and 126 disadvantaged children (DC) were included in this study. Anti-Toxocara ELISA test was performed in order to evaluate seroprevalence. A survey was applied to the children's guardians/parents in order to analyze the protective and risk factors. The overall prevalence was 11.1%, and of 9.5% (12/126) and 12.7% (16/126) for MC and DC subgroups, respectively. Toxocara seropositivity was inversely proportional to the family income. A high household income was considered a protective factor for toxocariasis in the total population and in both MC and DC subgroups. Being a girl was considered a protective factor for the total population and for both subgroups. Whilst being an owner of cat was a risk factor for children belonging to the total and for both MC and DC subgroups, having dog was considered as a risk factor for only the MC. Epidemiologic protective/factor risks can be distinct depending on the strata of the same population. Thus, it is relevant to evaluate these factors independently for different socioeconomic classes in order to design future investigations and programs for preventing the infection of human beings by Toxocara spp. and other geohelminths.

Nematode infection of the liver mimicking metastasis of malignant melanoma

BACKGROUND

The differential diagnoses of a circumscribed mass of the liver are varied. Especially if a malignant tumor, capable of setting metastases to the liver, is known in a patient's medical history, there might be difficulties in differentiating the tumor's entity. CASUISTRY: We report a case of a 40-year-old male with a history of malignant melanoma in whom follow-up investigations revealed a mass in the liver.

RESULTS

The histopathological and microbiological results, however, showed an infestation of liver tissue with nematodes. Malignant tumor cells could not be detected.

CONCLUSIONS

Roundworm-infections of the liver can present as lesions suspicious of being malignant. Therefore, along with e.g. microhamartoma, microabscesses and hepatocellular carcinoma, infestation with nematodes should be taken into consideration.

Eosinophilia: secondary, clonal and idiopathic

Blood eosinophilia signifies either a cytokine-mediated reactive phenomenon (secondary) or an integral phenotype of an underlying haematological neoplasm (primary). Secondary eosinophilia is usually associated with parasitosis in Third World countries and allergic conditions in the West. Primary eosinophilia is operationally classified as being clonal or idiopathic, depending on the respective presence or absence of a molecular, cytogenetic or histological evidence for a myeloid malignancy. The current communication features a comprehensive clinical summary of both secondary and primary eosinophilic disorders with emphasis on recent developments in molecular pathogenesis and treatment.

Visceral larva migrans presenting as acute abdomen in a child

An unusual presentation of visceral larva migrans observed in a patient is reported. A 5-year-old boy suffering fever, abdominal pain, tenderness, and rigidity in the right lower and upper quadrant of the abdomen was operated on, with the false diagnosis of acute abdomen, and exploratory surgery was carried out. The pathological examination of the liver biopsy revealed eosinophil-rich necrotizing granulomatous inflammation with Toxocara spp larva. The diagnosis was also confirmed by serologic results. Clinicians should remember that toxocaral visceral larva migrans may rarely mimic an acute abdomen and cause unnecessary operations.

Blood eosinophilia: a new paradigm in disease classification, diagnosis, and treatment

Acquired blood eosinophilia is considered either a primary or a secondary phenomenon. Causes of secondary (ie, reactive) eosinophilia include tissue-invasive parasitosis, allergic or inflammatory conditions, and malignancies in which eosinophils are not considered part of the neoplastic process. Primary eosinophilia is classified operationally into 2 categories: clonal and idiopathic. Clonal eosinophilia stipulates the presence of either cytogenetic evidence or bone marrow histological evidence of an otherwise classified hematologic malignancy such as acute leukemia or a chronic myeloid disorder. Idiopathic eosinophilia is a diagnosis of exclusion (ie, not secondary or clonal). Hypereosinophilic syndrome is a subcategory of idiopathic eosinophilia; diagnosis requires documentation of both sustained eosinophilia (absolute eosinophil count > or = 1500 cells/microL for at least 6 months) and target organ damage (eg, involvement of the heart, lung, skin, or nerve tissue). Genetic mutations involving the platelet-derived growth factor receptor genes (PDGFR-alpha and PDGFR-beta) have been pathogenetically linked to clonal eosinophilia, and their presence predicts treatment response to imatinib. Accordingly, cytogenetic and/or molecular investigations for the presence of an imatinib-sensitive molecular target should accompany current evaluation for primary eosinophilia. In the absence of such a drug target, specific treatment is dictated by the underlying hematologic malignancy in cases of clonal eosinophilia; however, the initial treatment of choice for symptomatic patients with hypereosinophilic syndrome is prednisone and/or interferon alfa.

Retinoblastoma and Simulating Lesions: Role of Imaging

Although the diagnosis of retinoblastoma (Rb) is made primarily by means of clinical examination, CT and MR imaging are helpful to confirm the diagnosis, determine the extent of the intraocular tumor, and exclude extraocular or intracranial involvement. They are also valuable in differentiating Rb from lesions that simulate Rb.

Blood eosinophilia: a new paradigm in disease classification, diagnosis, and treatment

Acquired blood eosinophilia is considered either a primary or a secondary phenomenon. Causes of secondary (ie, reactive) eosinophilia include tissue-invasive parasitosis, allergic or inflammatory conditions, and malignancies in which eosinophils are not considered part of the neoplastic process. Primary eosinophilia is classified operationally into 2 categories: clonal and idiopathic. Clonal eosinophilia stipulates the presence of either cytogenetic evidence or bone marrow histological evidence of an otherwise classified hematologic malignancy such as acute leukemia or a chronic myeloid disorder. Idiopathic eosinophilia is a diagnosis of exclusion (ie, not secondary or clonal). Hypereosinophilic syndrome is a subcategory of idiopathic eosinophilia; diagnosis requires documentation of both sustained eosinophilia (absolute eosinophil count > or = 1500 cells/microL for at least 6 months) and target organ damage (eg, involvement of the heart, lung, skin, or nerve tissue). Genetic mutations involving the platelet-derived growth factor receptor genes (PDGFR-alpha and PDGFR-beta) have been pathogenetically linked to clonal eosinophilia, and their presence predicts treatment response to imatinib. Accordingly, cytogenetic and/or molecular investigations for the presence of an imatinib-sensitive molecular target should accompany current evaluation for primary eosinophilia. In the absence of such a drug target, specific treatment is dictated by the underlying hematologic malignancy in cases of clonal eosinophilia; however, the initial treatment of choice for symptomatic patients with hypereosinophilic syndrome is prednisone and/or interferon alfa.

[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.

Neuromuscular diseases and disorders of the alimentary system

This review outlines the relationship and interaction between neuromuscular diseases and disorders of the alimentary system. Neuromuscular manifestations of gastrointestinal and hepatobiliary diseases are first considered. Such diseases may cause neuromuscular disorders by leading to nutritional deficiency or by more direct mechanisms. The pathogenesis, clinical features, and treatment of these various neuromuscular manifestations are discussed. The impact of disorders of nerve, neuromuscular transmission, and muscle on the alimentary system is then reviewed. The main sequelae are impaired deglutition and gastrointestinal dysmotility. The management of these complications is considered.

Eosinophilic granuloma of the liver: a characteristic lesion with relationship to visceral larva migrans

Children with the clinical syndrome of visceral larva migrans as a result of Toxocara species have typical lesions in the liver and other viscera, consisting of palisading granulomas that contain numerous eosinophils and often Charcot-Leyden crystals; recognizable parasites are uncommon. Similar eosinophilic granulomas that are found incidentally in adults often cause diagnostic problems. To define better the clinical, laboratory, and pathologic features of these lesions, we reviewed 43 cases of hepatic eosinophilic granuloma (excluding cases of Langerhans' cell histiocytosis) collected in the files of the AFIP over a period of 31 years. The eosinophilic granulomas were found in patients of all ages (range 12 months to 77 years); 30% were younger than 20 years. There were 26 male and 17 female patients. Most patients (26 of 43; 60%) were asymptomatic, and the lesions were discovered incidentally. Others had fever (20%) or abdominal pain (20%). The granulomas were typically multiple (61%), with central necrosis surrounded by a mixed inflammatory infiltrate with numerous eosinophils and variable numbers of neutrophils. lymphocytes, and a palisade of epithelioid histiocytes and/or giant cells. Charcot-Leyden crystals were present in 19 cases (44%). Remnants of parasites (eight Toxocara sp., two Capillaria sp.) were identified in the tissue in 10 patients. There was a positive serologic test for Toxocara sp. in five additional cases. Immunohistochemical staining using polyclonal antiserum against Toxocara canis larvae demonstrated positivity in macrophages in eight of 13 cases tested. We conclude that identification of an eosinophilic granuloma in the liver should suggest the diagnosis of visceral larva migrans and prompt a search for the causative organism with serial sectioning of the block and serologic tests for Toxocara and other causative parasites.

Fungal and parasitic infections of the eye

The unique structure of the human eye as well as exposure of the eye directly to the environment renders it vulnerable to a number of uncommon infectious diseases caused by fungi and parasites. Host defenses directed against these microorganisms, once anatomical barriers are breached, are often insufficient to prevent loss of vision. Therefore, the timely identification and treatment of the involved microorganisms are paramount. The anatomy of the eye and its surrounding structures is presented with an emphasis upon the association of the anatomy with specific infection of fungi and parasites. For example, filamentous fungal infections of the eye are usually due to penetrating trauma by objects contaminated by vegetable matter of the cornea or globe or, by extension, of infection from adjacent paranasal sinuses. Fungal endophthalmitis and chorioretinitis, on the other hand, are usually the result of antecedent fungemia seeding the ocular tissue. Candida spp. are the most common cause of endogenous endophthalmitis, although initial infection with the dimorphic fungi may lead to infection and scarring of the chorioretina. Contact lens wear is associated with keratitis caused by yeasts, filamentous fungi, and Acanthamoebae spp. Most parasitic infections of the eye, however, arise following bloodborne carriage of the microorganism to the eye or adjacent structures.

Fungal and parasitic infections of the eye

The unique structure of the human eye as well as exposure of the eye directly to the environment renders it vulnerable to a number of uncommon infectious diseases caused by fungi and parasites. Host defenses directed against these microorganisms, once anatomical barriers are breached, are often insufficient to prevent loss of vision. Therefore, the timely identification and treatment of the involved microorganisms are paramount. The anatomy of the eye and its surrounding structures is presented with an emphasis upon the association of the anatomy with specific infection of fungi and parasites. For example, filamentous fungal infections of the eye are usually due to penetrating trauma by objects contaminated by vegetable matter of the cornea or globe or, by extension, of infection from adjacent paranasal sinuses. Fungal endophthalmitis and chorioretinitis, on the other hand, are usually the result of antecedent fungemia seeding the ocular tissue. Candida spp. are the most common cause of endogenous endophthalmitis, although initial infection with the dimorphic fungi may lead to infection and scarring of the chorioretina. Contact lens wear is associated with keratitis caused by yeasts, filamentous fungi, and Acanthamoebae spp. Most parasitic infections of the eye, however, arise following bloodborne carriage of the microorganism to the eye or adjacent structures.

Contaminação, por ovos de Toxocara spp, de parques e praças públicas de Botucatu, São Paulo, Brasil

A freqüência de contaminação de parques e praças públicas de Botucatu, São Paulo, Brasil, por ovos de Toxocara spp foi estudada durante 12 meses, com colheitas mensais de amostras de solo de dez praças, que foram processadas pela técnica de concentração em solução decinormal de hidróxido de sódio. Das 120 amostras analisadas, 21 estavam contaminadas, correspondendo a 17,5%, em um total de seis praças. A maioria desses ovos porém apresentaram características de inviabilidade infectiva. Embora a chance de aquisição dessa zoonose nas praças estudadas seja pequena, existe o risco de infecção da população.

Retinoblastoma and simulating lesions. Role of CT, MR imaging and use of Gd-DTPA contrast enhancement

The diagnosis of Rb can usually be made by clinical examination; however, patients should also be studied by CT and MR imaging to help determine the extent of the intraocular tumor, document intralesional calcification, confirm the diagnosis, and delineate orbital or intracranial involvement. These imaging techniques should aid the clinician in differentiating Rb from lesions that simulate Rb.

Toxocariasis simulating hepatic recurrence in a patient with Wilms' tumor

We report the case of a 3-year-old girl with stage I Wilms' tumor of favorable histology. During the course of chemotherapy 5 months post-diagnosis, an abdominal ultrasonogram revealed hypoechoic areas consistent with hepatic tumor recurrence. A liver biopsy performed to rule out recurrence of the malignancy was suggestive of toxocariasis and the diagnosis was confirmed by serologic testing. Although the patient had few classic signs of visceral larva migrans, her eosinophilia and family social history should have suggested this possibility. This case demonstrates that hepatic toxocariasis should be considered in evaluating hepatic hypoechoic lesions in a child, even when features typical of the disease are absent.

The spectrum of ocular toxocariasis

Ocular toxocariasis is rare and therefore the spectrum of clinical disease is difficult to establish. We present a review of the clinical features and laboratory findings in a group of patients with positive Toxocara serology and ocular toxocariasis. The clinical spectrum was diverse and milder disease was commoner than might be supposed from reviews of the literature. Eosinophilia was unusual, but featured in two cases of unilateral pars planitis.

Feline zoonotic diseases

Many of the feline zoonoses occur more frequently in veterinary personnel owing to their direct contact with cats and the potential for exposure to infected body tissue or fluids. Infection of humans with Afipia felis, Yersinia pestis, Francisella tularensis, and other aerobic/anaerobic bacteria may cause great discomfort and in some situations terminal illness. Although many systemic fungal agents infect humans and cats, only Sporothrix schenckii has been shown to infect humans following direct exposure to infected cats. Various parasites, enteric protozoans and bacteria, and Toxoplasma gondii infections also may cause significant human illness. Therefore, routine handling of cats may expose human personnel in a veterinary facility to an array of important or emerging feline-associated human illnesses that occur in the United States.

"Covert toxocariasis" in a child treated with low-dose diethylcarbamazine

A girl aged 2.5 years with "covert toxocariasis" was treated with low-dose diethylcarbamazine because of supposed noticeable disseminated Toxocara canis infection without ocular or visceral manifestations. There was marked blood and bone marrow eosinophilia, significant increased Toxocara canis antibody (ELISA) and immunoglobulins E, G and M, leucocytosis and an increased sedimentation rate. She had no geophagia, but often sucked small stones, probably contaminated with faeces from puppies. Symptoms were fever, inactivity, weakness, tiredness and loss of appetite. She was followed clinically and with blood samples throughout a period of three years and four months.

The extraparasitic life cycle of Toxocara vitulorum in the village environment of Sri Lanka

The extraparasitic life cycle of Toxocara vitulorum of buffalo in the villages of Sri Lanka is related to observations on buffalo behaviour, experimental studies on the development and persistence of the eggs in soil and in wallows and the presence of eggs in village locations. Calf faeces on soil were rapidly incorporated by insect activity and the eggs developed only slightly slower than in the laboratory. Some infective eggs persisted 3-4 cm deep for 17 months, finally dying during a prolonged hot, dry period. Eggs in a wallow developed intermittently over 16 months as it was flushed with rain water, and eventually died when the wallow dried out. When infected faeces were placed in water, decomposition caused some material to rise to the surface and eggs developed. In villages, eggs are ubiquitous where young calves are kept but survive best where there is moisture and shade around animal pens and wallows. Cows and calves acquire infection from infective eggs in wallow water, soil and pasture, while calves may also be infected from contamination on the udder and teats of the cow. The larvae resulting from this infection do not mature until the infection is passed to the calf through the milk of the cow. At least 72% of village calves have patent infections and current treatment procedures do not reduce the prevalence. The possibility that T. vitulorum is a cause of human visceral larva migrans is discussed.

An epidemiological and serological study of toxocara infection in Sweden

The serological prevalence of toxocara infection was determined in 323 sera from statistically selected healthy individuals from different geographical areas of Sweden. The serological response in 175 sera from patients suspected of having contracted toxocariasis was compared with their clinical manifestation and age. The sera were analysed by ELISA using excretory/secretory antigens. The serological prevalence in young adults was estimated to 7%, indicating that subclinical toxocariasis occurs in healthy Swedes. The prevalence figure is not contrasting with reports from other countries. Antibodies were predominantly demonstrated in sera from men living in a rural community compared to sera from the other areas investigated (p less than 0.01). 91% of the sera from patients were obtained from patients greater than 5 years old. The clinical manifestations were ocular disorder (46%), eosinophilia (32%), lung, liver, neurological disorders (14%). The disorders were equally distributed between the age groups. A seropositive reaction was noted in 25% of the patients and the various clinical manifestations and age groups were equally represented among the seropositives. However, the percentage of seropositive patients with ocular disorders increased with growing age, whereas the opposite was observed in patients with eosinophilia. The results indicate that clinically apparent toxocariasis exists in Sweden.

Allergic necrotizing eosinophilic granulomatosis

Allergic necrotizing eosinophilic granulomatosis (ANEG) is a rare entity characterized by peripheral eosinophilia, hepatosplenomegaly, dyspnea, and lymphadenopathy. An unusual patient with ANEG is described in which the presenting feature was an extensive granulomatous lesion of the face. The patient's condition progressively deteriorated despite multiple therapies, and she finally succumbed to her disease.

A critical look at the importance, prevalence and control of toxocariasis and the possibilities of immunological control

The visceral infection of humans with Toxocara canis is particularly prevalent in children and may cause a variety of symptoms that commonly persist for 6-24 months. The ocular infection usually causes permanent loss of visual acuity. Human infection is acquired by ingestion of embryonated T. canis eggs with contaminated dirt. Review of recent reports indicates that patent T. canis infection is widely prevalent in the general population of dogs all over the world (3-81%) and results in a substantial contamination of the ground (0.3-87%). The results of sensitive and specific serological tests suggest that about 7% of the clinically healthy human population of the United States, about 5% of that of Canada, and about 4% of that in Great Britain is infected with the parasite. Control of transmission of the parasite to man is often attempted by eliminating the infection in dogs, reducing the population of dogs and the environmental contamination with their feces, and educating the public about the zoonotic potential of toxocariasis. The evidence reviewed indicates that these methods are only marginally effective. Because T. canis relies on congenital and lactogenic transmission to persist in nature, only a procedure that effects the sustained killing of the reservoir larvae in the tissues of the bitch, or of newly-acquired parasites, is expected to be successful. Research with mice, rabbits and dogs demonstrated that prior infections of the host induce the development of protective immunity to reinfections. This procedure, however, leaves remnant populations of larvae from the immunizing infections that are resistant to anthelmintics and to the effect of prior irradiation. Hyperimmunization with partially-purified extracts of T. canis larvae induced 37% resistance to a challenge in mice when the extract was administered alone, and 76% resistance when administered with lipopolysaccharide adjuvant. Production of complete resistance, however, will probably require the prior control of the immunosuppression induced by the parasite. T. canis infections inhibit the production of homologous protective immunity and antibody responses to heterologous antigens, probably by interfering with the activity of helper T-cells, competing with protective antigens, and suppressing antibody synthesis. The evidence indicates, however, that an anti-T. canis vaccine to eliminate the parasite in dogs is feasible.

Toxocara canis infection of children: epidemiologic and neuropsychologic findings

Sera from 4,652 children whose blood was submitted to the New York City Department of Health for lead analysis were tested for antibodies to Toxocara canis using an enzyme-linked immunosorbent assay (ELISA). Standardized to the age distribution of the study population, T. canis seropositivity (inverse titers greater than or equal to 16) was 5.7 per cent in males and 5.1 per cent in females. T. canis antibody titers and lead exposures as measured by Centers for Disease Control lead classes were positively correlated. Children who were seropositive to T. canis (cases) were compared to seronegatives (controls) matched on age (+/- 6 months), sex, time-of-screening (+/- 3 months) and CDC lead class. Logistic regression analysis of 155 case-control pairs demonstrated elevated relative risks (RRs) for geophagia (RR = 3.14; 95% CI = 1.75, 5.64) and having had a litter of puppies in the home (RR = 5.22; 95% CI = 1.63, 16.71). Compared to controls, cases had increased eosinophil counts, serum immunoglobulin E concentrations, and anti-hemagglutinin-A titers. Small deficits in cases compared to controls were found in performance on several neuropsychological tests after adjustment for potential confounders including case-control differences in race, socioeconomic status, and current blood lead concentrations. The study thus confirmed that T. canis infection is common in urban children and suggested that infection may be associated with adverse neuropsychological effects.

The impact of single versus repeated exposure of mice to Toxocara canis

Infection with T. canis can alter dramatically the brain and behavior of the host. Previous results suggest that if the mammalian host is exposed either simultaneously to lead, or has a history of prior exposure to that toxic substance, the magnitude of the behavioral reaction to T. canis may be modified or even reduced. The present data suggest that the magnitude of both the behavioral and tissue/immune reactions may be less if the organism has multiple, instead of a single exposure, to T. canis. Lead, and perhaps other environmental toxicants may alter neurotropic products of the parasite, the behavior of the parasite, and/or reactivity of the host in the presence of the parasite. Such considerations may help explain, in part, the relative rarity of reported toxocariasis in humans, despite the fact that serological indices suggest that exposure to T. canis may be as high as 7% of the world population.

Computed tomography of Toxocara canis endophthalmitis

Many lesions, termed pseudogliomas, may mimic the appearance of retinoblastoma, both clinically and on computed tomography. The appearance of Toxocara canis endophthalmitis on computed tomography is presented. The role of computed tomography in the evaluation of patients presenting with leukokoria is discussed.

Toxocara canis infestation. Clinical and epidemiological associations with seropositivity in kindergarten children

We studied a cohort of 333 children in kindergarten to determine the prevalence of seropositivity to Toxocara canis, and to detect and measure chronic health effects that might be attributable to past infection. We found that 23.1% of the children had serologic evidence of infection (antibody titer greater than or equal to 1:32), assayed by means of an enzyme-linked immunosorbent assay. Black children were more frequently infested than white children, as were children of parents who did not graduate from high school. In a subsample of seropositive and seronegative children, we found associations between seropositivity and both pica and puppy ownership; we did not find differences in the symptoms and signs that occur in toxocaral visceral larva migrans nor differences in measures of growth and nutrition. No child had ocular toxocariasis although 31.8% (106) of the children had antibody titers greater than or equal to 1:16. In a population in which approximately 20 to 30% of the children show serologic evidence of Toxocara infestation, care must be taken in differentiating toxocariasis-like ophthalmic lesions, due to the potential for the coincidental occurrence of retinoblastoma in a child who is seropositive for the Toxocara parasite.

Toxocara canis: interaction of human blood eosinophils with the infective larvae

This study was carried out to investigate the nature of the immunological responses which took place in a child who had recently recovered from toxocariasis. She had developed a marked eosinophilia and had high titers of toxocara antibodies. Experiments were performed to examine whether Toxocara canis infective larvae could be killed in the presence of her serum and human eosinophils. Eosinophils with human complement, or this patient's serum, adhered to the surface of the larvae within 10 min. By 40 min, using both light and electron microscopy, it was shown that the cells had flattened against the cuticle and degranulated. However, by 3 hr, eosinophils had begun to detach, and the larvae remained alive for at least 1 week afterward. Further addition of serum or of eosinophils, which were shown to be able to immobilize T. spiralis infective larvae, failed to kill the T. canis larvae. It was concluded that, in this patient, the development of an inflammatory response to a T. canis infection was not associated with the appearance of antibodies capable of inducing eosinophil dependent toxicity to the larvae in vitro. Eosinophil dependent killing mechanisms may be less important than other components of the immune response, in immunity to this parasite in humans.

The prevalence of Toxocara species ova in backyards and gardens of Baltimore, Maryland

Toxocara species ova were found in 16 of 146 (11 per cent) soil samples collected from backyards and gardens of private residences within Baltimore City. The recovery rate of parasite ova was similar for households regardless of their grouping by pet ownership characteristics or the presence of visible animal feces. The findings demonstrate the common occurrence of these eggs in locations likely to be important in the transmission of visceral larva migrans.

Serologic and intradermal tests for parasitic infections

For years, the diagnosis of most parasitic diseases has depended upon the direct demonstration of the parasite or its cysts, eggs, or larvae in specimens. In some infections, direct demonstration of the causative agent or its stages is almost impossible. In such cases, indirect techniques, such as serologic methods, have been found to be more practical and sensitive than are direct methods. Most serologic methods have been devised to detect antibodies. Tests for the detection of antigen are just beginning to be utilized; however, the practicality and under what situations antigen detection tests can be used await further testing. The majority of the serum antibody tests employ a heterogeneous mixture of antigens. Antigens derived from whole adult or larval stages usually result in tests with poor specificity and/or sensitivity. The necessity for better purified and standardized antigens cannot be over emphasized. Although there have been many major advances in the serodiagnosis of parasitic infections, a major drawback to routine use of parasitic serologies is the lack of commercially available reliable test kits. For the diagnosis of most parasitic diseases, one must rely upon specialty laboratories or public health laboratories. Before any laboratory begins to offer parasitic test serologies, they should contact their local or state public health laboratory or the Parasitic Serologic Section of the Centers for Disease Control to determine the pros and cons of these tests. Information of this type should be used to inform the physician of the limitations of the test in the differential diagnosis.

The progression of behavioral and pathological effects of the parasite Toxocara canis in the mouse

Toxocara canis, the parasitic roundworm of the dog may infect aberrant hosts including mice and humans. The present study examined the behavioral and pathological changes at each of three postintubation periods (Period 1: 8-10 days, 2: 49-51 days, and 3: 84-86 days postintubation, respectively) in independent groups of mice intubated with 1000 eggs of T. canis. Eight-ten days after intubation Toxocara infected animals typically showed depressed levels of activity relative to saline-intubated controls. The scope and severity of behavioral changes were attenuated when different mice were tested 49-51 days after infection, and then became more severe when the third set of animals was tested 84-86 days after intubation. While brain pathology increased over the three periods, visceral organs showed marked pathology 8-10 days after intubation followed by a decrease in severity. These data suggest that Toxocara associated pathological changes in visceral organs and in the brain have behavioral consequences in mice. Given the similarity in migratory pathways of this parasite in rodents and humans, and the findings of T. canis larvae in human brain tissue, the results of this animal study may have implications concerning the possible etiology of behavioral disorders for children who have a known history of pica for dirt.

Immune responses of CBA/J mice to graded infections with Toxocara canis

The immunological responsiveness of CBA/J mice infected with various numbers of the canine ascarid, Toxocara canis, was characterized after a single infection to ascertain the smallest infection capable of perturbing the immune system of the host. Mice receiving the lowest inoculations (5 eggs per mouse or 0.25 larvae per g of body weight) had detectable alterations in the number of circulating peripheral blood eosinophils and spleen weight-to-body weight ratios. Mice infected with 25 eggs each (1.25 larvae per g of body weight) showed augmented concanavalin A-elicited splenic lymphocyte transformation and a positive lymphocyte transformation in response to a toxocaral antigen preparation in addition to even higher eosinophil counts and heavier spleens. Spleen cells from mice receiving the two largest inocula (125 eggs and 250 eggs per mouse or 6.25 and 12.5 larvae per g of body weight, respectively) had in addition to the above responses a sixfold increase in spontaneous DNA synthesis. An enzyme-linked immunosorbent assay for mouse antibody responses to T. canis indicated that the time of onset as well as the magnitude of the antitoxocaral humoral response is directly proportional to the size of the inoculation used to initiate the infection. Finally, we showed that allowing the infection to become protracted results in some responses increasing somewhat in magnitude, but regardless of length of infection, the magnitude of any of the responses examined is proportional to the size of the infection. The results indicate that different host responses have different thresholds of sensitization and suggest that larvacidal reactions which require intricate interactions among several components of the immune system may not occur in very small infections.

Behavioral effects of early lead exposure and subsequent toxocariasis in mice

Mice were maintained under standard conditions, or treated with lead from birth, until they were approximately 40 d of age. At that time the lead solution was replaced with tap water and all animals were gastrointestinally intubated with either the parasite Toxocara canis or normal saline. At 2-5 wk following intubation the behavioral effects of T. canis in combination with the prior history of lead ingestion were compared to those produced by administration of either T. canis or lead alone or a single saline intubation. Differential group activity scores (cage crosses and standups) in response to changes in the home-cage environment during testing sessions were observed. While the addition of a second tier to the home cage during testing resulted in increased activity scores for all groups, changing the home-cage bedding produced increased activity only in the T. canis alone or prior lead ingestion alone groups. However, there were no differences in the number of parasite larvae found in fresh brain tissue preparations in either the T. canis alone or T. canis plus lead-history combination groups.

Computed tomography with histopathologic correlation in children with leukokoria

Computed tomography (CT) constitutes a major advance in noninvasive diagnostic investigation of children with leukokoria , especially where media opacities preclude adequate visualization of the posterior segment, and, performed in conjunction with other studies such as diagnostic ultrasonography, has significantly improved diagnostic accuracy. Although retinoblastoma, the commonest life-threatening cause of leukokoria , usually presents with characteristic CT findings of intraocular calcification, during extraocular extension, the orbital portions of the tumor are non-calcific and contrast dramatically with the intraocular portion. Currently CT is also the best available technique for diagnosis of trilateral retinoblastoma. Computed tomographic features of several types of pseudogliomas (a collective term for lesions commonly mistaken for retinoblastomas) are also discussed with histopathologic correlation. In persistent hyperplastic primary vitreous, a conical density in CT corresponded to detached and dysplastic retina. A high density layered opacity corresponded to subretinal blood. In Coats' disease and sclerosing endophthalmitis homogenous intraocular CT density corresponds to vitreous and subretinal exudates radiologically indistinguishable from non-calcific retinoblastoma. Long-standing retinal detachments in children occasionally presenting with leukokoria showed subtle homogenous intraocular densities on CT.

Sclerosing endophthalmitis in children: computed tomography with histopathologic correlation

Three children with histopathologically diagnosed sclerosing endophthalmitis presumably secondary to Toxocara canis were studied by orbital computed tomography. The diffuse increased intraocular density present in the CT scans was indistinguishable from that observed in Coats's disease and non-calcifying retinoblastoma. Although retinoblastoma constitutes the major life-threatening cause of leukocoria in children, a number of other simulating conditions (pseudoglioma) can cause diagnostic confusion. In some cases of leukocoria it is exceedingly difficult to exclude the possibility of retinoblastoma without having to resort to enucleation. The availability of new non-invasive tests may make the distinction between retinoblastoma and pseudogliomas more easily attainable. Computed tomography (CT) has been shown to be of particular value in this regard by demonstrating intraocular calcification within retinoblastoma and rarely in lesions that stimulate it. CT may also be used to more appropriately plan therapy for children with retinoblastoma by assessing the status of the optic nerve and orbit. The exact role of CT in the evaluation of children with leukocoria, however, has not been completely established, since the computed tomographic features of several lesions that simulate retinoblastoma have not been described. The three most common causes of pseudoglioma are persistent hyperplastic primary vitreous, Coats's disease and sclerosing endophthalmitis. The latter entity when associated with a characteristic granulomatous inflammation is considered to represent the sequela of Toxocara canis infection of the eye. This report describes the computed tomographic findings in three cases of histologically diagnosed sclerosing endophthalmitis, presumably due to Toxocara canis.

Risk factors for toxocaral ocular larva migrans: a case-control study

Twenty-four patients with serologically confirmed toxocaral ocular larva migrans (OLM) and 24 age- and sex-matched controls were the subjects of an epidemiologic study. Information on the exposure to dogs and other factors possibly associated with transmission of toxocariasis was obtained by contacting the parents of the subjects. The odds of having had a dog present in the household within the year previous to onset of illness were 3 to 1 for cases vs controls. An association of pups (< 3 months) in the households of OLM patients within one year of onset was statistically significant (P < .05). Twenty-three of 24 OLM patients had had dogs in their homes some time before their illness, and the twenty-fourth patient had a history of geophagia, a behavioral pattern previously identified as a risk factor for toxocariasis. Exposure to cats and other animals in or outside the home did not differ for patients and controls. Infected dogs, especially pups, in the patients' homes were the most probably sources of infection for this group of OLM patients.

Visceral larva migrans caused by Trichuris vulpis

Two brothers with visceral larva migrans caused by Trichuris vulpis were diagnosed after they had been investigated for an eosinophilia. Both patients were almost asymptomatic. The diagnosis of visceral larva migrans was based on the results of immunoelectrophoretic studies and no liver biopsy was performed. After administration of thiabendazole, the number of eosinophils and serum total IgE levels gradually decreased, and the patients have remained well.

ELISA for diagnosis of ocular toxocariasis

The enzyme-linked immunosorbed assay test was positive in 37 of 41 patients (90%) suspected of having clinical Toxocara infections. The antigen used in this test is prepared from the Toxocara egg and is felt to be extremely specific in making the diagnosis. The prevalence of Toxocara infection is much greater than previously believed. It is hoped that this test will help the surgeon fell more secure in not enucleating eyes containing masses suggestive of Toxocara infection.