Seroprevalence of ToxocaraCanis in Asthmatic Children and its Relation to the Severity of Diseases - a Case-Control Study

Background

Toxocariasis is a common parasitic infectionworldwide even in developed countries. Through this health problem, the immune system is triggered and the antibody is produced, leading to some hypersensitive situations like asthma. In the present study, we tried to show a correlation between Toxocara Canis (T. canis) seropositivityand asthma in Isfahan city.

Methods

This research is a cross-sectional study involving 40 asthmatics and 46 non-asthmatic cases aged 2-18 years. In all cases, T. canis IgG level was measured using enzyme-linked immunosorbent assay (ELISA) and compared between two groups.

Results

The seroprevalence of IgG anti-T. canis antibodies were 45%in the asthmatic patients and 21.7% in thecontrols (P= 0.022). The more severe asthmatic patients had significantly more risk for T. canis seropositivity (P= 0.019). In the asthmatic patients, there was a significant correlation between Toxocara seropositivity and goingto park or playground (P= 0.001).

Conclusion

In this study, we found a significantly positive serology of T. canis in asthmatic children especially in more severe disease. To verify the etiologic role of Toxocara in asthma, more advanced studies are needed.

[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.

The increase in seroprevalence to Toxocara canis in asthmatic children is related to cross-reaction with Ascaris suum antigens

BACKGROUND

It has been suggested that the presence of Toxocara canis larvae in lungs is an underlying factor in the onset of asthma. Although the association of asthma and seropositivity to Toxocara has been observed, there are no studies that indicate whether these antibodies are specific against T. canis antigens.

METHODS

Seroprevalence to T. canis excretion-secretion antigens (TcES Ag) were compared between asthmatic children (n=285) and non-asthmatic children (n=152), using IgG-ELISA and IgE-ELISA. The recognition patterns of TcES Ag were determined using Western blot (WB).

RESULTS

IgG-ELISA seroprevalence was 30.8% for asthmatic children and 19.7% for non-asthmatic children (p<0.05). IgE-ELISA seroprevalence was 7.7% for asthmatic children and 6.5% for non-asthmatic children, respectively (p>0.05). Sera of both groups positive to IgG-ELISA recognised 11 TcES Ag bands for IgG. No differences between the groups were observed regarding recognition patterns; the asthmatic group, however, presented significantly higher cross-reaction to Ascaris suum somatic antigens (AsS Ag) than the non-asthmatic group. Sixty-three sera from asthmatic children positive to IgG-ELISA were evaluated by WB for IgE and 58.7% revealed a recognition pattern for IgE. In the group of non-asthmatic children positive to IgG-ELISA, 80% presented IgE band recognition. No differences were observed between the groups regarding recognition patterns.

CONCLUSIONS

The results observed suggest that differences in seroprevalence determined by IgG-ELISA between groups of asthmatic and non-asthmatic children reported by other authors occur because of a higher frequency of cross-reaction in asthmatic children.

[Tropical causes of epilepsy]

INTRODUCTION

Eighty-five percent of all epileptics live in tropical regions. Prenatal risk factors, traumatic brain injuries and different parasitic infestations of the central nervous system (CNS) are the reasons behind the high prevalence of epilepsy. This work reviews the main parasitic infestations causing epilepsy in the tropics.

DEVELOPMENT

Neurocysticercosis is the main cause of focal epilepsy in early adulthood in endemic areas (30-50%). All the phases of cysticerci (viable, transitional and calcified) are associated with epileptic seizures. Anti-cysticercus treatment helps get rid of cysticerci faster and reduces the risk of recurrence of seizures in patients with viable cysts. Symptomatic epilepsy can be the first manifestation of neuroschistosomiasis in patients without any systemic symptoms. The pseudotumoral form can trigger seizures secondary to the presence of granulomas and oedemas in the cerebral cortex. The eggs of Schistosoma japonicum are smaller, reach the CNS more easily and trigger epileptic seizures more frequently. Toxocariasis and sparganosis are other parasitic infestations that can give rise to symptomatic seizures. The risk factors for suffering chronic epilepsy after cerebral malaria are a positive familial history of epilepsy and a history of episodes of fever and cerebral malaria that began with coma or which progressed with multiple, prolonged epileptic seizures. About 20% of patients with cerebral infarction secondary to Chagas disease present late vascular epilepsy as a complication.

CONCLUSIONS

Very few studies have been conducted to examine the prognosis, risk of recurrence and modification of the natural course of seizures associated with tropical parasitic infestations, except for the case of neurocysticercosis.

Toxocariasis in Japan

Toxocariasis has long been considered a parasitic disease affecting pet owners and children who often play in sandboxes at public parks. Recent cases of this animal-borne infection, however, indicate that its clinical manifestations and etiologies are changing. In this article, we will describe the critical characteristic features of toxocariasis alongside the contributions of Japanese researchers to a better understanding of the disease.

MRI studies of spinal visceral larva migrans syndrome

We report serial MR findings in four patients with myelitis caused by visceral larva migrans syndrome due to Toxocara canis or Ascaris suum infection. MR imaging revealed spinal cord swelling with or without gadolinium enhancement in three patients. T2-weighted images showed high signal intensities preferentially located in both lateral and posterior columns. Antihelmintic and corticosteroid treatment yielded improvement in neurologic deficits and spinal lesions. However, one patient with T. canis infection relapsed associated with reappearance of MRI abnormalities.

Toxocara canis infections in a pig model: immunological, haematological and blood biochemistry responses

The immunological, haematological and enzymatic responses to the inoculation in pigs of 100,000 embryonated eggs of Toxocara canis were studied. Fifteen females were inoculated and three remained as controls. Haematological values were analysed from day 7 p.i. until day 126 p.i. In the inoculated group, white blood cells were raised on day 14 p.i. and eosinophil values on days 7, 14, 21, 35 and 49 p.i. showing significant differences compared with controls (P < 0.05). Absolute eosinophil counts (per ml) presented two rises, the first on days 7, 14 and 21 p.i. and the second on days 35 and 49 p.i. Blood biochemistry was maintained within normal values. Serological examination by ELISA to determine antibody levels against Toxocara canis L2/L3 excretory-secretory (ES) antigens showed values higher than the positive cut-off (1:32) from day 7 p.i. and until the end of the study on day 126 p.i., presenting two peaks: one on day 28 p.i. and the second covering days 49 to 56 p.i. Western blots of sera of inoculated animals presented, from day 7 p.i., two polypeptide bands of 55 and 70 kDa MW and, from day 56 p.i., an additional band of 120 kDa MW, all of which persisted until the end of the study. Immunological responses were sustained over time. No direct correlation was observed between the rise in eosinophils and antibody titres. To validate the conclusions, more studies are required on the polypeptide bands.

A murine model for cerebral toxocariasis: characterization of host susceptibility and behaviour

Toxocara canis, the parasitic roundworm of dogs, can infect a number of paratenic hosts, such as mice and humans, due to the widespread dissemination of its ova in the environment. In these paratenic hosts, larvae have been shown to exhibit a predilection for the central nervous system, resulting in an increasing number of parasites migrating to the brain as infection progresses. In an initial experiment, we investigated the differential brain involvement of T. canis in 7 strains of inbred mice, and chose 2 strains, susceptible (BALB/c) and resistant (NIH) to cerebral infection. In a second experiment, both strains were investigated in terms of course of migration, larval accumulation, and behavioural response to T. canis infection. Results revealed that infected BALB/c mice took significantly longer to drink from a water source (following a period of deprivation), compared with control mice, indicating some degree of memory impairment. Cerebral larval recoveries from both strains of mice demonstrated variation between the two experiments, suggesting that larval burdens may not be a reliable indicator of susceptibility or resistance to T. canis infection. The percentage of total recovered larvae in each organ may be a better representation of larval distribution. Our model system may provide insights into the impact of chronic geohelminth infection on cognitive development.

Disodium cromoglycate prevents ileum hyperreactivity to histamine in Toxocara canis-infected guinea pigs

The aim of this study was to investigate whether Toxocara canis infection in guinea pigs provokes changes in ileum responsiveness to histamine. Ileum segments from control and T. canis-infected groups were placed at isometric conditions and submitted to various doses of histamine. No changes were observed between controls and T. canis-infected groups at days 3, 6 and 12 after infection. However, at days 18 and 24 after infection, there was a significant increase in ileum responsiveness to histamine in T. canis-infected group. Pre-incubation of ileum segments with 1mgml(-1) disodium cromoglycate (DSCG) prevented the increased responsiveness to histamine in T. canis-infected guinea pigs and did not affect ileum contractility in non-infected animals. These results indicate that T. canis-infected guinea pigs develop increased intestinal responsiveness to histamine and that DSCG prevents alterations in smooth-muscle contractility.

Toxocariasis: clinical aspects, epidemiology, medical ecology, and molecular aspects

Toxocariasis is caused by a series of related nematode species (ascarids) that routinely infect dogs and cats throughout the world. The eggs from these ascarids are common environmental contaminants of human habitation, due largely to the fact that many kinds of dogs and cats serve as pets, while countless others run wild throughout the streets of most urban centers. The eggs, present in dog and cat feces, become infectious within weeks after they are deposited in the local environment (e.g., sandboxes, city parks, and public beaches, etc.). Humans, particularly children, frequently ingest these eggs by accident and become infected. Infection in humans, in contrast to their definitive hosts, remains occult, often resulting in disease caused by the migrating larval stages. Visceral larva migrans (VLM) and ocular larva migrans (OLM) are two clinical manifestations that result in definable syndromes and present as serious health problems wherever they occur. Diagnosis and treatment of VLM and OLM are difficult. These issues are summarized in this review, with emphasis on the ecology of transmission and control of spread to both humans and animals through public health initiatives employing treatment of pets and environmental intervention strategies that limit the areas that dogs and cats are allowed within the confines of urban centers.

Eosinophilic pleocytosis and myelitis related to Toxocara canis infection

Toxocara canis causes the visceral larva migrans syndrome in which central nervous involvement is rare. We report the case of a 40-year-old woman presenting with a subacute weakness of the right leg and dysaesthesiae in the right Th8-Th10 dermatomas. Spinal magnetic resonance imaging examination showed abnormal hyperintensity within the spinal cord. Cerebrospinal fluid analysis revealed eosinophilic pleocytosis. Antibody titres to Toxocara canis were higher in the cerebrospinal fluid than in the serum. Treatment using mebendazole led to a complete clinical recovery, normalization of cerebrospinal fluid parameters and improvement in spinal magnetic resonance imaging abnormalities.

Ocular larva migrans caused by Toxocara cati in Mongolian gerbils and a comparison of ophthalmologic findings with those produced by T. canis

To elucidate the pathogenic potential of Toxocara cari, we observed the ophthalmologic changes of the fundi in Mongolian gerbils, Meriones unguiculatus, after oral inoculation of 17 embryonated eggs/g body weight. Ophthalmic conditions in 8 T. cati-infected gerbils were monitored using an ophthalmoscope from day 0 to day 156 and were compared with those of 57 T. canis-infected gerbils. The results showed that T. cati larvae migrated into the eye of the gerbil and then elicited ophthalmic changes, including retinal (25%) and vitreous (50%) hemorrhaging, vasculitis (37.5%), and exudative lesions (25%). Lesions were less prevalent, however, in T. cati-infected than in T. canis-infected gerbils. Unlike in T. canis-infected gerbils, the hemorrhagic lesions did not reappear in T. cati-infected gerbils after they were absorbed. These findings suggested that T. cati larvae are a potentially hazardous pathogen for ocular toxocariasis and that Mongolian gerbils infected with T. cati may be a useful model for the study of human ocular toxocariasis caused by T. cati. This is the first study to report that T. cati larvae can induce ophthalmic lesions in the retina of gerbils.

Effects of monoclonal antibodies to adhesion molecules on eosinophilic myocarditis in Toxocara canis-infected CBA/J mice

Eosinophilic myocarditis followed by fibrosis of the cardiac muscle was observed in addition to peripheral blood eosinophilia in CBA/J mice infected with Toxocara canis. The infected mice were used as an experimental model of eosinophilic endomyocarditis associated with hypereosinophilic syndrome. Effects of in vivo treatment with MoAbs to adhesion molecules on eosinophilic myocarditis were examined using this experimental model. Expressions of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) on endothelial cells of capillaries in myocardium were increased 1 and 2 weeks after infection. Infiltration of very late antigen (VLA)-4+ and/or CD11a+ cells into the cardiac muscles was also observed 1 and 2 weeks after infection. Infiltration of eosinophils into the heart was significantly suppressed by anti-CD18 MoAb and anti-VLA-4 MoAb, and focal fibrosis of the cardiac muscle was also significantly suppressed by combined administration of anti-CD18 and anti-ICAM-1 MoAbs. These results indicate that adhesion molecules may play important roles in eosinophilic myocarditis, and that blockade of interaction between adhesion molecules and their ligands may help to control it.

Incidence of patent Toxocara canis infection in bitches during the oestrous cycle

The incidence of patent Toxocara canis infection as result of reactivation of somatic larvae with subsequent tracheal migration was investigated by faecal examination during 23 oestrous cycles of 15 bitches. Blood samples were collected for determination of total and differential leukocyte counts, prolactin concentration, and Toxocara titre. Five pregnant dogs were used as controls. In the cyclic dogs there were no alterations in white blood cell counts or prolactin concentration, in contrast with the pregnant dogs, in which both variables increased, starting 10 days after onset of the luteal phase. The difference was significant at day 40 and day 60 (both p < 0.005). No significant differences were observed in the number of eosinophils or in the Toxocara antibody titre. T. canis eggs were only found in the faeces of three 1-year-old, cyclic dogs at 1, 60, and 140 days, respectively, after the onset of the luteal phase. It is concluded that cyclic beagle bitches, in which prolactin levels increase in the second half of the luteal phase, are unlikely to be at higher risk for patent T. canis infection than in other phases.

Effect of ozone treatment on Toxocara canis eggs

The effect of ozone treatment on the development and viability of Toxocara canis eggs was studied. Despite treatment with ozone, unembryonated T. canis eggs could develop into viable second-stage larvae when assayed by larvae recovery after oral inoculation into mice. The viability of second stage larvae of T. canis was also not affected by ozone treatment. No significant difference was observed in the larvae recovery count and migratory pattern of the ozone-treated larvae and the untreated control because the majority of the larvae were recovered from the liver and lungs on day 2 postinoculation. However, scanning electron microscopy of the ozone treated T. canis eggs showed many blebs on the surface of the protein coat at the basement of the honeycomb-like structures. The honeycomb-like structures on the egg surface were also observed to be distorted after ozone treatment. Thus, in spite of inducing some surface morphological changes on the egg, ozone was observed to have no effect on the viability of the embryonated second stage larvae of T. canis.

Effect of some parasitic infection on neurotransmitters in the brain of experimentally infected mice before and after treatment

The effects of some parasitic infection (bilharziasis, toxocariasis and trichinosis) on the brain of experimentally infected mice were investigated. Eighty animals were classified into four groups, group I contained five non infected animals as a control group. The other groups each contained twenty-five mice infected with Schistosoma mansoni (group II), Toxocara canis (group III) and Trichinella spiralis (group IV). Each infected group was divided into two subgroups (a,b). Subgroup (a) left untreated and subgroups (b) treated by praziquantel (in group II) and mebendazole (in group III and IV). Histopathological and immunological examination using peroxidase antiperoxidase (PAP) technique and neurotransmitters estimation (nor-epinephrine, dopamine and serotonine) were carried. In the untreated animals, there were mild histopathological changes and mild antigenic deposition in subgroups (IIa and IIIa) and marked changes in subgroup (IVa). There were significant decrease in dopamine in subgroup (IIIa), not improved after treatment (subgroup IIIb) and significant decrease in nor-epinephrine and serotonine in subgroup (IVa) improved after treatment in subgroup (IVb). The neurotransmitters changes may explain the motor, behavioural and emotional changes that occurred with these parasites.

Investigations into the prevention of neonatal Toxocara canis infections in puppies by application of doramectin to the bitch

The aim of this investigation was to examine whether the treatment of bitches with doramectin is able to prevent pre-natal and galactogenic infections with Toxocara canis in their pups. Five experimentally infected beagle bitches were treated subcutaneously with 1 mg doramectin per kg body weight on each of days 40 and 55 of their pregnancy. Another infected bitch served as an untreated control. The efficacy of the medication was examined by counting the intestinal stages and somatic larvae in bitches and pups. The treatment did not completely prevent perinatal infections with T. canis. Intestinal stages and/or somatic larvae occurred in 16 of 20 pups. Seven pups developed patent infections. Compared to the control pups, the average worm burden (intestinal stages) of pups from treated bitches was less than 1%. No impairment of condition or physical development was noticed in the pups during the investigations. From the second week of life, the pups of the non-medicated bitch showed signs of a severe toxocarosis. No side effects were seen in the bitches after treatment with doramectin.

Relationship between parasitical inoculum and immunological parameters in experimental toxocariasis

Swiss female mice were inoculated with different infective doses of Toxocara canis eggs to evaluate the percentage of recuperated larvae in different organs and immunological parameters such as spleen index (SI), liver index (LI) and lung index (LuI) and blood eosinophilia during 3 weeks post infectionem (p.i.) with only one challenge. It was found that T. canis larvae arrived at the liver between 10 and 15 hours p.i. by the food-fishhook technique. When the inoculum was more than 200 eggs, there was a reinvasion of liver and lungs at 504 hours p.i. The larval arrival at the brain was delayed in an inverse relationship to the inoculum but the percentage of recovery was about 7 and 8%. The organic indexes were in a direct relationship with the inoculum size and the increase in eosinophilic levels in massive infections (2000 eggs) was in agreement with a strong immune response.

[Toxocariasis. A cosmopolitan parasitic zoonosis]

The infection by Toxocara canis transmitted by dogs (30% of them are infected in our countries) and less frequently by cats lead to larva migrans visceral syndrome with neurological manifestations, ophtalmological affection and various cutaneous manifestations observed in 24% of the extra-ocular infections: chronic urticaria often associated with asthmatic manifestations and chronic rhinitis, angio-oedema or local oedema reaching particularly the eyclid, chronic pruritus associated with lesions due to scratching or to nodular prurigo. An hypereosinophilia is an argument in favour of a progressive infection. High total IgE is an hallmark of visceral infections by parasites and total IgE level is well correlated with the presence of intra-tissular larva. The serological diagnosis is based on the determination of specific IgG by ELISA which appears also to be interesting for the patient's follow up. The western blot method seems to be more specific than the other methods and so is useful to confirm a diagnosis. The treatment given as early as possible is based on the use of diethylcarbamazine but also of thiabendazole, albendazole and mebendazole. Prophylaxis of toxocara infection includes the prohibition of dog access to children games areas but also a frequent turn over of the sand in public parks.

Toxocara-induced eosinophilic inflammation. Airway function and effect of anti-IL-5

The immunoinflammatory response to parasitic nematode infections and allergic diseases have some similarities, the most profound being the increases in eosinophils and serum total IgE concentration. Whether parasitic infections stimulate or inhibit allergic asthma is a matter of debate. We investigated the effect of Toxocara canis (T. canis) infection on airway function in BALB/c mice at various days post-infection. Within 24 h after infection, the trachea responded hyperreactive to carbachol stimulation. Eosinophils, and to a lesser degree lymphocytes, infiltrated the airways causing interstitial and alveolar inflammation (7 d post-infection). Concurrently with cell infiltration, the trachea became hyporesponsive to carbachol whereas the pulmonary resistance was increased and the dynamic compliance decreased. The hyporeactive response could be simulated in vitro by incubating normal tracheae with eosinophil-enriched bronchoalveolar lavage cells obtained from infected mice. The response depended on the number of cells added to the medium, a lower number causing a hyper- and a higher number a hyporeactive response. Anti-interleukin-5 (anti-IL-5) producing hybridoma cells given simultaneously with T. canis infection inhibited eosinophil infiltration in the airways but not that of lymphocytes. Anti-IL-5 treatment prevented tracheal hyporeactivity but not perivascular and peribronchial edema, increased pulmonary resistance, or decreased dynamic compliance. Treatment with isotype control antibody did not affect eosinophil number nor the observed changes in airway functions. It was concluded that T. canis-induced airway inflammation coincided with increased pulmonary resistance, decreased dynamic compliance, and perivascular/peribronchial edema. These phenomena were independent on the presence of eosinophils, whereas tracheal hyporeactivity was clearly associated with airway eosinophilia.

Larval distribution of Toxocara canis in BALB/c mice at nine weeks and one year post-inoculation

The migratory route of Toxocara canis in the mouse includes two phases: a hepato-pulmonary phase and a myotropic-neurotropic phase. A study was made of the migratory behaviour of larvae one year post-inoculation (p.i.) comparing the results to those obtained at the end of an initial experiment (day 63 p.i). The larval distribution per organ was already definitive at 9 weeks p.i. The total parasitic load showed a reduction when the experiment was prolonged for one year.

The behavior and pathogenicity of Toxacara canis larvae in mice of different strains

In the present study the behavior and pathogenicity of second-stage larvae of Toxocara canis were examined in different mouse strains with special emphasis on the major histocompatibility complex (MHC). Mice of the inbred strains BALB, C3H, C57BL, and DBA and the outbred strain NMRI were infected orally with 1000 second-stage larvae of T. canis. The clinical behavior of the animals; the numbers of larvae detected in the liver, lungs, brain, and musculature; the hematological and serological parameters; and histological sections were examined. In mice of the BALB strain, no death occurred during the entire period of the investigation and the pattern of body-weight development of infected and uninfected animals was almost identical. The highest larval counts in the brain of all strains were found in BALB mice. The percentage of eosinophils in the blood of BALB mice increased after the 8th week postinfection, whereas it decreased in the other strains. Histological and pathophysiological changes developed to a lesser extent in this strain than in the other strains. In mice of the strains C3H, C57BL, DBA, and NMRI, deaths occurred from the 4th week postinfection onward. The infected animals lost weight in comparison with the uninfected controls; the number of larvae found in the brains of infected mice of the above-mentioned strains were lower than those detected in the BALB strain. There is no evidence that mechanical damage caused by migrating larvae in the brain tissue is mainly responsible for symptoms of central nervous toxocariasis. Likewise, the assumption that the MHC is involved in the allergic-inflammatory response in the brain could not be proven: infected mice of the BALB and DBA strains reacted completely differently, although both are equipped with the same MHC haplotype.

Development and characterization of a model of eosinophil-mediated cardiomyopathy in rats infected with Toxocara canis

This study begins testing the hypothesis that a causal relationship exists between hypereosinophilia and cardiac dysfunction. Rats infected with the nematode Toxocara canis develop marked hypereosinophilia, with peak blood eosinophil levels of approximately 3,500 eosinophils/mm3 whole blood observed approximately 14 days postinfection. Corresponding to the increase in blood eosinophils of infected animals was a decrease in cardiac performance. By 14 days postinfection, cardiac work had declined approximately 25% while negative first derivative of pressure (-dP/dt) fell approximately 10%. As the extent of hypereosinophilia declined from a peak of approximately 3,500 eosinophils/mm3 whole blood to a new steady state of approximately 1,000 eosinophils/mm3, the degree of cardiac dysfunction also was reduced. Cardiac work was 10-15% less in rats 28-42 days postinfection while -dP/dt was 5% depressed in these animals. Myocardial dysfunction was also observed following exposure of perfused hearts obtained from uninfected rats to buffer containing activated eosinophils. The hearts exposed to activated eosinophils exhibited marked histological alterations, characterized by distention of the intermyocyte space, increased pericapillary space, and focal losses of striated staining pattern. These changes were associated with the accumulation of eosinophils within the myocardium, as evidenced by the cytochemical demonstration of eosinophil peroxidase activity within the heart. The data support the hypothesis that hypereosinophilia can lead to cardiac dysfunction.

Biology and pathophysiology of Toxocara vitulorum infections in a rabbit model

Ten female New Zealand rabbits were infected via stomach intubation with eggs of Toxocara vitulorum at a dosage of 10 embryonated eggs per gram of body weight on Days 0, 35 and 72. Ten or 4% of the administered parasites passed in the feces during the 3 days following the first or second infection, but 32% after the third infection. Many larvae were passed in the third infection, but not in the first or second. Tissue parasite yields were 4.1% on Day 5, 2% on Day 15, 0.8% on Day 30, 0.1% on Day 65 and 0.06% on Day 101. Five hundred and ninety-three larvae were recovered from liver, 243 from lungs and 0 from muscles on Day 5; 282 from liver, 138 from lungs and 21 from muscles on Day 15; 151 from liver, 21 from lungs and 50 from muscles on Day 30; 0 from liver, 26 from lungs and 15 from muscles on Day 65; 0 from liver, 0 from lungs and 9 from muscles on Day 101. No larvae were found in other tissues. The size of the muscle larvae at 30, 65 and 101 days indicated that the parasites did not develop beyond the infective stage and suggested that they were probably hypobiotic organisms. Erythrocytes, packed cell volume and monocytes decreased, but eosinophils and basophils increased, after each infection. Serum enzyme levels indicated that liver damage occurred only after the first infection, but muscle injury occurred after each infection and was increasingly more precocious after each infection.

Intestinal changes in puppies infected with Toxocara canis

Small intestinal histopathology and absorption were examined in Beagle puppies infected with either a moderate or a low burden of Toxocara canis. Infection with T. canis significantly reduced absorption of xylose, but only slightly delayed absorption of para-aminobenzoic acid. Fat assimilation was reduced and faecal proteolytic activity was increased. A significant reduction in villous height occurred and was inversely related to the extent of the infection. Villous goblet cell numbers, particularly those in the luminal third of the villus, were lowest and crypt goblet cell numbers were highest in the most heavily infected of the puppies. Villous goblet cell numbers increased rapidly after treatment of the puppies with piperazine or after the spontaneous elimination of the T. canis infection while crypt goblet cell numbers were less affected by elimination of the parasites. Intra-epithelial lymphocyte numbers were lowest in 33- to 37-day-old puppies infected with greater than 127 T. canis and highest in 44- to 46-day-old puppies losing their infection. Infection with T. canis had no apparent effect on mast cell numbers or pyroninophilic cell numbers in the lamina propria.

Toxocara canis-induced airway hyporeactivity in mice

Migrating larvae of the canine nematode Toxocara canis induce inflammatory responses in the lungs of infected mice. Histological examination of the lungs showed that mice, developed persistent multifocal inflammation in which eosinophils (eos), macrophages (M phi) and many lymphocytes were involved. Cuffing of blood vessels and bronchioles with mixed cell populations was also observed. Investigation into the response of isolated tracheae to cholinergic and beta-adrenergic receptor agonists demonstrated a significant decreased reactivity despite the pronounced involvement of eos and M phi. This hyporeactive state persisted for greater than or equal to 4 weeks p.i..

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.

Eosinophil response in mast cell-deficient W/WV mice

The combination of cyclophosphamide treatment and Toxocara canis infection is known as an effective way of causing a high level of eosinophilia in mice. When this treatment was applied to congenitally anemic, mast cell-deficient W/WV mice, eosinophil response was far less than that of their normal littermate +/+ mice. The degree of the defective eosinophil response in the peripheral blood of W/WV mice was severer than that in the bone marrow. The defective eosinophil response of W/WV mice was completely restored by bone marrow grafting 8 weeks prior to cyclophosphamide treatment and T. canis infection. The kinetics of the recovery of eosinophil response in the bone marrow of W/WV mice after bone marrow grafting was faster than that in the peripheral blood. Chemotactic reactivity of eosinophils obtained from bone marrow or peritoneal cavity of W/WV mice was essentially comparable to that of +/+ mice. These results suggest that, in addition to the production of eosinophils in the bone marrow, mast cell-derived factors play an important role in the mediation of peripheral blood eosinophilia.

Experimental toxocariasis and hyperactivity in mice

An observational study using videorecordings and computer-assisted data analysis was undertaken in order to investigate the behaviour of mice infected with larvae of Toxocara canis. The findings indicated that the infection had a marked effect on five readily and reliably differentiable categories of murine behaviour. A marked increase in the number of shorter bouts of each of the five behaviours was also associated with the infection. These results support previous findings and further suggest that T. canis infection affects the way in which mice respond to their environment. In particular the infection appears to be associated with hyperactivity in mice. Possible causes of such behavioural abnormalities as well as implications of these findings for clinical studies concerned with relationships between T. canis infection and hyperactivity in children are discussed.

Magnetic resonance imaging in the evaluation of leukocoria

Leukocoria is an important clinical sign in ophthalmology. Conditions producing this white pupillary reflex must be differentiated from retinoblastoma to insure appropriate and timely treatment. Auxiliary diagnostic testing has been helpful in securing a clinical diagnosis. A new diagnostic modality, magnetic resonance imaging, provides similar morphologic information with the additional potential for biochemical characterization. A series consisting of 14 patients presenting with leukocoria as a result of retinoblastoma and simulating conditions was examined. The magnetic resonance imaging findings are discussed.

Possible role of histamine in the genesis of pulmonary arterial disease in cats infected with Toxocara cati

Kittens between 12 and 20 weeks of age were orally dosed with 6000 infective ova of Toxocara cati. Animals were sacrificed at intervals between one and eight weeks after infection to study the development of pulmonary arterial lesions. After two weeks, marked leucocyte infiltration and mild thickening of the media of some of the smaller arteries was apparent histologically . Cellular inflammatory activity progressively increased up to four weeks after infection when intimal proliferation was evident in many of the arteries. After six weeks, the arterial walls were grossly thickened with pronounced intimal proliferation which after eight weeks had resulted in complete occlusion of some vessels. The progressive arterial occlusion was associated with a three- to four-fold increase in the parenchymal mast cell population and a corresponding increase in lung histamine content. The possible role of histamine in the genesis of the arteriopathy is discussed.

Experimental toxocariasis in mice and its effect on their behaviour

When compared to uninfected controls, mice infected with second-stage larvae of Toxocara canis exhibited: (1) impaired motor performance, (2) increased ambulatory activity, (3) a greater relative preference for more exposed areas and (4) a greater overall preference for novel environments. The infected mice also appeared to show less approach-avoidance conflict and seemed less cautious when presented with novel stimuli. These behavioural differences were independent of measures of general health. Possible explanations for the observed behavioural deficits are discussed. Such alterations in behaviour may be implicated in the continuation of the life-cycle of this parasite by making mouse paratenic hosts more liable to capture and subsequent ingestion by canids, the definitive hosts of T. canis.

Behavioral effects of lead and Toxocara canis in mice

Adult mice were administered the common parasite Toxocara canis or lead or both. The parasite clearly altered mouse performance on tests of exploration, activity, learning, and motor coordination; behavioral effects in mice receiving lead alone were less general. Consequence of Toxocara administration appeared attenuated in animals receiving both agents. Parasite larvae were found in the central nervous system in all infected mice.