Visceral larva migrans associated with earthworm ingestion: clinical evolution in an adolescent patient

Genetic and population diversity of Toxocara cati (Schrank, 1788) Brumpt, 1927, on the basis of the internal transcribed spacer (ITS) region

The present investigation was aimed to study the sequence, phylogenetic and haplotype analyses of Toxocara cati based on the ITS region, along with the genetic diversity, demographic history and population-genetic structure. The maximum likelihood tree based on Kimura 2-parameter model was constructed using the complete ITS region of all the nucleotide sequences (n = 57) of Toxocara spp. and other related ascarid worms available in the GenBank™. It placed all the sequences of T. cati into four major clades designated as T. cati genotypes 1-4 (TcG1-G4). A total of 66 signature nucleotides were identified in the ITS region between genotypes. The median-joining haplotype network displayed a total of 24 haplotypes, with China exhibiting the highest number of haplotypes (h = 20) followed by India (h = 4), and Japan and Russia (h = 1). It indicated a clear distinction between all the four genotypes. The pairwise F_ST values between all the genotypes indicated huge genetic differentiation (> 0.25) between different T. cati genotypes. Moreover, the gene flow (Nm) between T. cati genotypes was very low. Results of AMOVA revealed higher genetic variation between genotypes (92.82%) as compared to the variation within genotypes (7.18%). The neutrality indices and mismatch distributions for the G1-G4 genotypes, Indian isolates and the overall dataset of T. cati indicated either a constant population size or a slight population increase. The geographical distribution of all the genotypes of T. cati is also reported. This is the first report of genotyping of T. cati on the basis of the ITS region.

Prevalence of Toxocara Eggs in Public Parks in the City of Valencia (Eastern Spain)

Toxocara spp. is one of the most common zoonotic geohelminths in the world. Its infections are associated with the accidental ingestion of contaminated soil and affecting, especially children. In this study, feces, and soil samples from 14 public parks in the city of Valencia were analyzed. The Telemann method and a modified version of a sieving technique were used to process feces and soil, respectively. None of the fecal samples and 10.9% of soil samples from five parks (35.7%) tested positive for the presence of Toxocara eggs. The most contaminated areas were the canine sanitary parks (30.8% of the samples), followed by socialization areas for dogs (9.7%); no positive samples were found at children’s playgrounds. Our results suggest that most pets in Valencia are periodically dewormed, although additional preventive measures should be applied, since the risk of infection exists probably due to the presence of stray dogs and feral cats.

Brain food: rethinking food-borne toxocariasis

Human toxocariasis is a neglected tropical disease, which is actually global in distribution and has a significant impact on global public health. The infection can lead to several serious conditions in humans, including allergic, ophthalmic and neurological disorders such as epilepsy. It is caused by the common roundworm species Toxocara canis and Toxocara cati, with humans becoming accidentally infected via the ingestion of eggs or larvae. Toxocara eggs are deposited on the ground when infected dogs, cats and foxes defecate, with the eggs contaminating crops, grazing pastures, and subsequently food animals. However, transmission of Toxocara to humans via food consumption has received relatively little attention in the literature. To establish the risks that contaminated food poses to the public, a renewed research focus is required. This review discusses what is currently known about food-borne Toxocara transmission, highlighting the gaps in our understanding that require further attention, and outlining some potential preventative strategies which could be employed to safeguard consumer health.

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

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

Seroprevalence, risk factors, and clinical symptoms of Toxocara spp. infection among children 3-15 years old in northern Iran

The World Health Organization has categorized toxocarosis as a neglected tropical disease despite its significant impact on high-risk groups such as children. This study aimed to investigate the seroprevalence, risk factors, and clinical symptoms of Toxocara spp. infection among children 3-15 years old in northern Iran. A total of 386 children were enrolled in the study. All serum samples were tested for the presence of IgG antibodies against Toxocara spp. infection using an enzyme-linked immunosorbent assay. Moreover, relevant risk factors and clinical symptom data were obtained using questionnaires. Data analysis was performed using the SPSS software version 24. The overall seroprevalence of Toxocara spp. infection was found 2.85 % (11/386). However, Toxocara spp. infection was high for some risk factors, including eating soil (14.3 %), contacting cats (6.7 %), and consuming raw vegetables (3.7 %). However, there were no statistically significant differences regarding the risk factors and socio-demographic characteristics. Considering the clinical symptoms, Toxocara spp. infection was different in children with eosinophilia (20 %), ocular disorders (8.3 %), skin disorders (7.7 %), liver disorders (4.5 %), and stomach ache (4.2 %), although not statistically significant. The results revealed that the seroprevalence of Toxocara spp. infection was relatively low in children in northern Iran. It is suggested to conduct more studies in different parts of Iran to gain a deeper understanding of the toxocarosis seroprevalence and its status in high-risk groups such as children with asthma, hypereosinophilic syndrome, allergic skin disorders, and epilepsy.

Toxocara infection: seroprevalence and associated risk factors among primary school children in central China

Toxocariasis is a zoonotic disease that poses a threat to public health worldwide. In the present study, we investigated the seroprevalence of Toxocara infection among primary school children in Henan province, central China, which was previously unknown. Sera from 2451 primary school children were collected from September 2015 to October 2018, and evaluated for anti-Toxocara antibodies by enzyme-linked immunosorbent assay (ELISA). The overall seroprevalence of Toxocara infection was 5.14% (126/2451). The main risk factors related to Toxocara infection identified in this study were the age of children, residence area of children, contact with cats or dogs, and exposure to soil. Hand washing before eating was considered to be a protective factor. These findings demonstrate that Toxocara infection is relatively common among primary school children in Henan province.

History of Toxocara and the associated larva migrans

This review covers the systematics and nomenclature of the Ascaridoid genus toxocara, and more specifically the species Toxocara canis and Toxocara cati. Also discussed is the discovery of the persistence of these larvae in the tissues of paratenic hosts, and the role that other species of this genus might or could play in other such hosts; including those where the life cycle has been described, i.e., Toxocara vitulorum, Toxocara pteropodis, Toxocara mackerrasae, and Toxocara tanuki. Also examined is the work that led to the realization that the larval stage leaving the egg actually being a third rather than a second stage larva. Also discussed on the work showing that the larvae can persist in paratenic host with remarkable longevity without undergoing any morphological change for years and that these larvae can be transmitted from one paratenic host to another by ingestion. People are usually infected by the ingestion of eggs containing third-stage larvae, but infections also occur on occasions from the ingestion of uncooked paratenic hosts.

Visceral larval migrans of Toxocara canis and Toxocara cati in non-canid and non-felid hosts

Toxocara canis and Toxocara cati are considered the most ubiquitous gastrointestinal helminths in domesticated canids and felids. Ascarid eggs passed in the faeces of canids and felids in a suitable environment may remain infective for years and are capable of infecting not only canids and felids, but a large range of other vertebrate paratenic hosts, including man. Infection with Toxocara species also occurs following the ingestion of paratenic hosts containing infective larvae. As infective larvae are incapable of completing their lifecycle in these hosts, they instead travel to different parts of the body, sometimes inducing inflammatory responses, and in some cases remaining entrapped in the body for years. Migration routes depend on the host species; however, nearly all organs may be affected with varying quantities of larval burdens.

Ascarid infection in wild Amur tigers (Panthera tigris altaica) in China

BACKGROUND

Wild Amur tigers are a sparsely populated species, and the conservation of this species is of great concern worldwide, but as an important health risk factor, parasite infection in them is not fully understanding.

RESULTS

In this study, sixty-two faecal samples were collected to investigate the frequency and infection intensity of Toxocara cati and Toxascaris leonina in wild Amur tigers. The T. cati and T. leonina eggs were preliminary identified by microscopy, and confirmed by molecular techniques. Infection intensity was determined by the modified McMaster technique. Phylogenetic trees demonstrated that T. cati of wild Amur tiger had a closer relationship with which of other wild felines than that of domestic cats. T. leonina of Amur tiger and other felines clustered into one clade, showing a closer relationship than canines. The average frequency of T. cati was 77.42% (48/62), and the frequency in 2016 (100%) were higher than those in 2013 (P = 0.051, < 0.1; 66.6%) and 2014 (P = 0.079, < 0.1; 72.2%). The infection intensity of T. cati ranged from 316.6 n/g to 1084.1 n/g. For T. leonina, only three samples presented eggs when the saturated sodium chloride floating method was performed, indicating that the frequency is 4.83% (3/62). Unfortunately, the egg number in faecal smears is lower than the detective limitation, so the infection intensity of T. leonina is missed.

CONCLUSIONS

This study demonstrated that ascarids are broadly prevalent, and T. cati is a dominant parasite species in the wild Amur tiger population.

Toxocara: Seroprevalence in Mexico

In Mexico, toxocariasis, like some other parasitosis in humans, is not a disease of conventional surveillance or immediate notification. Seroprevalence studies are scarce, six dealing with paediatric populations and eight dealing with adults; the reports were only from four states in Mexico. There were 1596 children, and the seroprevalence was 13.8%. In the case of adults, there were 1827 subjects, and seroprevalence was 4.7%. There is a significant positive association between seroprevalence and the paediatric population P<0.0001 (OR, 3.285; 95% CI, 2.541-4.279). It is advisable to perform competitive ELISAs and add another diagnostic test, such as Western blot or the detection of circulating antigens to reduce diagnostic uncertainty. This neglected parasitosis can be confused with retinoblastoma. Therefore, there is a risk of ocular enucleation. It is necessary to sensitise the authorities of the Ministry of Health and decision-makers, to provide economic support for epidemiological surveillance of this zoonotic parasite.

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

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

Human toxocariasis - A look at a neglected disease through an epidemiological 'prism'

Toxocariasis, a disease caused by infection with larvae of Toxocara canis, T. cati and/or congeners, represents clinical syndromes in humans including visceral and ocular larva migrans, neurotoxocariasis and covert/common toxocariasis. It is reported to be one of the most widespread public health and economically important zoonotic parasitic infections that humans share with dogs, wild canids, including foxes, and possibly other mammals. Humans become infected by accidental ingestion of embryonated Toxocara eggs, or larvae from tissues from domestic or wild paratenic hosts. Most infections are asymptomatic, and human disease may go unnoticed, as clinical investigation is often not pursued and/or diagnostic testing not conducted. Sometimes toxocariasis can be associated with complications, such as allergic and/or neurological disorders, possibly including cognitive or developmental delays in children. There is no anti-toxocariasis vaccine, and chemotherapy in humans varies, depending on symptoms and location of larvae, and may include the administration of albendazole or mebendazole, together with anti-inflammatory corticosteroids. Some recent studies indicate that toxocariasis is having an increased, adverse impact on human health in some, particularly underprivileged, tropical and subtropical communities around the world. Although tens of millions of people, especially children, are expected to be exposed to, or infected with Toxocara species, there is limited precise epidemiological data or information on the relationship between seropositivity and disease (toxocariasis) on a global scale. To gain an improved insight into this area, the present article reviews salient clinical aspects of human toxocariasis and the epidemiology of this disease, with particular reference to seroprevalence, and discusses future research and approaches/measures to understand and prevent/control this socioeconomically important, yet neglected zoonosis.

Molecular characterization of Toxocara spp. eggs isolated from public parks and playgrounds in Shiraz, Iran

Human toxocariasis, a worldwide parasitic disease, is caused by the larval stage of intestinal nematodes of dogs and cats, namely Toxocara canis and Toxocara cati. Human infection occurs by the accidental ingestion of embryonated eggs present in the soil, vegetables or on other contaminated surfaces, as well as via consumption of uncooked paratenic hosts, such as bird meat and giblets. The objective of this study was to evaluate the contamination of soil in public parks and playgrounds in Shiraz using microscopy and molecular methods. A total of 150 soil samples were collected from public parks and playgrounds in various areas of Shiraz, southern Iran. The samples were treated with saturated zinc sulphate solution, and Toxocara spp. eggs were detected by microscopic observation followed by nested polymerase chain reaction (PCR). To differentiate T. canis and T. cati eggs from each other, PCR restriction fragment length polymorphism (RFLP) of the internal transcribed spacer (ITS)-rDNA region by SalI endonuclease enzyme was used. PCR-sequencing was performed to confirm the results of the PCR-RFLP method. Based on the flotation results of the 150 soil samples, six (4%) were found to be positive for Toxocara spp. eggs, whereas nested-PCR showed 24 samples to be positive (16%). Based on the PCR-RFLP method and the sequence of the ITS-rDNA region, a total of 23 out of 24 isolates were confirmed as T. cati and one out of 24 as T. canis. The results showed a higher number of soil samples to be positive for Toxocara by the molecular method than microscopy, and higher T. cati infection in soil samples, which could have an important role in human infection with toxocariasis in this region.

Toxocara canis: Analysis of the kinetics of antigen release and antibody production in an in vivo model for the detection of past or present infection

Worldwide, Toxocara canis is an important zoonotic nematode of public health concern. This soil-transmitted helminth causes visceral larva and ocular larva migrans in paratenic hosts. The detection of T. canis larva migrans is complicated because current immunological tests detect only IgG antibodies, which can cross-react with antigens from other parasites and cannot distinguish between the past and present infection. Analysis of antigen release and antibody production could help improve the detection of larva migrans. Here, we report the kinetics of antigen release, IgM and IgG production in an in vivo model for the detection of past or present infection. We used four groups of seven mice: two groups infected orally with 50 or 100 embryonated eggs, and the other two infected intraperitoneally with 50 or 100 live larvae. We obtained blood samples at 0, 3, 7, and 14days and, then, every two weeks until day 140. Sandwich ELISA and indirect ELISA were performed for antigen capture and the detection of immunoglobulins, respectively. Mice inoculated with larvae developed an immune response faster than those inoculated with eggs. In all groups, antigen capture was positive starting at 3days until 140days post-inoculation (dpi). Detection of immunoglobulins was at 14 or 28dpi in mice inoculated with larvae or eggs, respectively. Negative IgM values were detected at days 98 and 112. The samples remained positive for IgG until the last day of the experiment. Data suggest that in mice inoculated with T canis eggs, some larvae did not hatch, others died or never reached the bloodstream. Based on our model, we propose that there is early infection when only antigens are present, and active larva migrans when antigen and immunoglobulins are detected, implying an immune response of the host against the antigen. Our study offers a view into the parasite-host relationship and enables us to infer if there are live larvae. Additionally, these findings provide a foundation for the diagnosis and differentiation of recent infection and active larva migrans.

Neurotoxocariasis: a systematic literature review

PURPOSE

Toxocariasis is a widespread zoonosis, which may result in central nervous system injury.

METHODS

We conducted a systematic literature review in MEDLINE, SciELO, ScienceDirect and Google Scholar up to April 2015 using a combination of the following search terms: "neurotoxocariasis" or "neurotoxocarosis", "toxocariasis" or "toxocarosis" and "cerebral" or "neurologic".

RESULTS

One hundred cases of neurotoxocariasis were identified in literature. The majority of patients were male (58 %), with a median age of 42 years. The predominant clinical pictures were myelitis (60 %), encephalitis (47 %) and/or meningitis (29 %). Fever was inconstant (23 %). The suspected mode of transmission, mentioned in only 49 % of cases, was mainly contact with dogs and/or cats (67 %) and ingestion of contaminated food (31 %). Diagnostic imaging examinations found hypodense lesions in cerebral scanner sequences and hyperintense lesions in cerebral MRI T2-weighted sequences in 65 and 57 % of encephalitis cases respectively, and in 92 % of myelitis cases in medullary MRI T2-weighted sequences. The detection of antibodies against Toxocara spp. was almost constant in blood and cerebrospinal fluid (CSF), 99 and 93 %, respectively. The two most commonly used drugs were corticosteroids (72 %) and/or albendazole (68 %) for a period of at least 3 weeks, which often needed to be repeated. Despite a low mortality rate (6 %), complete remission was observed in only 40 % of cases.

CONCLUSIONS

Neurotoxocariasis, a completely preventable zoonosis, could lead to severe sequelae failing prompt diagnosis. A compatible clinical picture, presence of risk factors, blood eosinophilia and high titers of antibodies against Toxocara spp. in CSF should alert physicians.

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.

Laboratory identification of arthropod ectoparasites

The collection, handling, identification, and reporting of ectoparasitic arthropods in clinical and reference diagnostic laboratories are discussed in this review. Included are data on ticks, mites, lice, fleas, myiasis-causing flies, and bed bugs. The public health importance of these organisms is briefly discussed. The focus is on the morphological identification and proper handling and reporting of cases involving arthropod ectoparasites, particularly those encountered in the United States. Other arthropods and other organisms not of public health concern, but routinely submitted to laboratories for identification, are also briefly discussed.

Prevalence and risk factors associated with Toxocara canis infection in children

The objective of this study was to determine seroprevalence and identify risk factors associated with Toxocara canis infection. A clinical and epidemiological questionnaire and body mass index were used to assess the risk factors associated with human toxocariasis in 108 children with an age range of 2-16 years. Antibodies against Toxocara canis were detected using an ELISA test kit. Chi-square analysis and odds ratio (OR) were used to identify risk factors associated with Toxocara canis seropositivity. The prevalence of antibodies against Toxocara canis was greater (P = 0.02) in males than females (28.84% and 16.07%, resp.). Chi-square analysis and odds ratio revealed just one variable with P < 0.05, and OR > 1.0 was associated with seropositivity: the possession of dogs under one year old (OR = 1.78). Although not significant, the OR values suggest that other factors may be epidemiologically important for Toxocara presence such as not washing hands before meals, malnutrition, obesity, and use of public parks. Children in the age group >12 and <16 years old had higher seroprevalence to Toxocara canis (17.59%) than the >2 and <11 years old age group (4.62%). Toxocariosis infection needs to be prevented by pet deworming and hygienic measures after contact with dogs.

Visceral larva migrans associated with earthworm and gecko ingestion: a case report

Introduction

Visceral larva migrans is a syndrome caused by an infection with larval helminths, which may result in partial or general pathological changes in host tissues. Due to the difficulty in finding the causative parasites, the diagnosis of visceral larva migrans is generally based on compatible clinical signs, epidemic history, marked eosinophilia and pathological examination, especially positive serological test results and the disappearance of symptoms after specific treatment.

Case presentation

We report here the case of a 21-year-old Chinese man who, having ingested living earthworms and geckos at a witch’s suggestion, presented with fatigue and wordlessness lasting for one year along with elevated transaminase levels for one month. Clinical examination showed eosinophilia, elevated transaminase levels, nodular lesions in his liver and typical pathological characteristics of hepatic visceral larva migrans. After four courses of anthelmintic therapy, our patient presented with sustaining improvement of clinical manifestations and normalization of laboratory data.

Conclusions

Because of the difficulty in making a definite diagnosis, anthelmintic therapy should be performed in patients with a suspected diagnosis of visceral larva migrans based on their epidemic history and presence of typical manifestations, especially when the serological test results are negative. Furthermore, patients with severe parasite infection may require multiple anthelmintic therapies in order to eliminate the parasites.

Epidemiologic and zoonotic aspects of ascarid infections in dogs and cats

Toxocaracanis and Toxocara cati of dogs and cats, respectively, can cause significant disease in people. Human seroprevalence for Toxocara antibodies varies with factors such as geographic location, socio-economic status, and dietary habits. Risk factors for infection include geophagia and low-level education. Toxocara canis is better recognized as a cause of human toxocariasis, but Toxocara cati should not be overlooked. In addition, patent infections with Baylisascaris procyonis, the raccoon ascarid, have been increasingly recognized in dogs. Pet owners need to be properly educated about zoonotic risks, and veterinarians should institute regular parasite screening and treatment for all pets. Establishment of national surveillance programs to determine the incidence and specific etiological agent in human larva migrans patients would aid in the development of targeted intervention strategies.

Pulmonary toxocariasis masquerading as metastatic tumor nodules in a child with osteosarcoma

A 14-year-old male, who completed chemotherapy following limb salvage surgery for osteosarcoma approximately 2 years ago, was seen for routine follow-up. A CT scan revealed new scattered multifocal nodular lesions. An ultrasonography-guided percutaneous needle biopsy was done to confirm pulmonary metastasis of the underlying osteosarcoma. The lung biopsy showed findings of eosinophilic pneumonia with no evidence of malignancy. Peripheral eosinophilia was also noted. When a more thorough history revealed frequent intake of raw cow liver, we diagnosed pulmonary toxocariasis by ELISA for specific serum IgG antibody.