Although human toxocariasis ranks among the most common zoonotic infections worldwide, it remains relatively unknown to the public. The causal agents are the nematode parasites Toxocara canis and T. cati, whose definitive hosts are dogs and cats, respectively. When embryonated eggs are accidentally ingested by humans, larvae hatch in the small intestine, penetrate the intestinal wall and migrate, via the bloodstream, to the liver, lungs, muscles, eye and central nervous system. Although most human infections are asymptomatic, two well-defined clinical syndromes are classically recognised: visceral larva migrans (a systemic disease caused by larval migration through major organs) and ocular larva migrans (a disease limited to the eyes and optic nerves). Two less-severe syndromes have recently been described, one mainly in children (covert toxocariasis) and the other mainly in adults (common toxocariasis). Here, the current laboratory diagnosis, epidemiology and main clinical features of both the systemic and ocular forms of human toxocariasis are reviewed. New developments in serological diagnosis are described, the available seroprevalence data are analysed, and the results of relevant clinical studies that have been published over the last decade are explored, to provide an updated overview of this neglected but highly prevalent human infection.

Human toxocariasis: diagnosis, worldwide seroprevalences and clinical expression of the systemic and ocular forms

Background: Strongyloides stercoralis, an intestinal parasitic nematode, infects more than 100 million people worldwide. Strongyloides are unique in their ability to exist as a free-living and autoinfective cycle. Strongyloidiasis can occur without any symptoms or as a potentially fatal hyperinfection or disseminated infection. The most common risk factors for these complications are immunosuppression caused by corticosteroids and infection with human T-lymphotropic virus or human immunodeficiency virus. Even though the diagnosis of strongyloidiasis is improved by advanced instrumentation techniques in isolated and complicated cases of hyperinfection or dissemination, efficient guidelines for screening the population in epidemiological surveys are lacking. Methodology and Results: In this review, we have discussed various conventional methods for the diagnosis and management of this disease, with an emphasis on recently developed molecular and serological methods that could be implemented to establish guidelines for precise diagnosis of infection in patients and screening in epidemiological surveys. A comprehensive analysis of various cases reported worldwide from different endemic and nonendemic foci of the disease for the last 40 years was evaluated in an effort to delineate the global prevalence of this disease. We also updated the current knowledge of the various clinical spectrum of this parasitic disease, with an emphasis on newer molecular diagnostic methods, treatment, and management of cases in immunosuppressed patients. Conclusion: Strongyloidiasis is considered a neglected tropical disease and is probably an underdiagnosed parasitic disease due to its low parasitic load and uncertain clinical symptoms. Increased infectivity rates in many developed countries and nonendemic regions nearing those in the most prevalent endemic regions of this parasite and the increasing transmission potential to immigrants, travelers, and immunosuppressed populations are indications for initiating an integrated approach towards prompt diagnosis and control of this parasitic disease.

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Strongyloidiasis—An Insight into Its Global Prevalence and Management

Background
Strongyloidiasis is a gut infection with Strongyloides stercoralis which is common world wide. Chronic infection usually causes a skin rash, vomiting, diarrhoea or constipation, and respiratory problems, and it can be fatal in people with immune deficiency. It may be treated with ivermectin or albendazole or thiabendazole.

Objectives
To assess the effects of ivermectin versus benzimidazoles (albendazole and thiabendazole) for treating chronic strongyloides infection.

Search methods
We searched the Cochrane Infectious Diseases Group Specialized Register (24 August 2015); the Cochrane Central Register of Controlled Trials (CENTRAL), published in the Cochrane Library; MEDLINE (January 1966 to August 2015); EMBASE (January 1980 to August 2015); LILACS (August 2015); and reference lists of articles. We also searched the metaRegister of Controlled Trials (mRCT) using 'strongyloid*' as a search term, reference lists, and conference abstracts.

Selection criteria
Randomized controlled trials of ivermectin versus albendazole or thiabendazole for treating chronic strongyloides infection.

Data collection and analysis
Two review authors independently extracted data and assessed risk of bias in the included trials. We used risk ratios (RRs) with 95% confidence intervals (CIs) and fixed- or random-effects models. We pooled adverse event data if the trials were sufficiently similar in their adverse event definitions.

Main results
We included seven trials, enrolling 1147 participants, conducted between 1994 and 2011 in different locations (Africa, Southeast Asia, America and Europe).

In trials comparing ivermectin with albendazole, parasitological cure was higher with ivermectin (RR 1.79, 95% CI 1.55 to 2.08; 478 participants, four trials, moderate quality evidence). There were no statistically significant differences in adverse events (RR 0.80, 95% CI 0.59 to 1.09; 518 participants, four trials, low quality evidence).

In trials comparing ivermectin with thiabendazole, there was little or no difference in parasitological cure (RR 1.07, 95% CI 0.96 to 1.20; 467 participants, three trials, low quality evidence). However, adverse events were less common with ivermectin (RR 0.31, 95% CI 0.20 to 0.50; 507 participants; three trials, moderate quality evidence).

In trials comparing different dosages of ivermectin, taking a second dose of 200 μg/kg of ivermectin was not associated with higher cure in a small subgroup of participants (RR 1.02, 95% CI 0.94 to 1.11; 94 participants, two trials).

Dizziness, nausea, and disorientation were commonly reported in all drug groups. There were no reports of serious adverse events or death.

Authors' conclusions
Ivermectin results in more people cured than albendazole, and is at least as well tolerated. In trials of ivermectin with thiabendazole, parasitological cure is similar but there are more adverse events with thiabendazole.

Ivermectin versus albendazole or thiabendazole for Strongyloides stercoralis infection.

Treatment of strongyloidiasis has been traditionally based on thiabendazole, despite its frequent gastrointestinal side effects and failure to achieve eradication of the parasite from faeces in ∼ 30% of cases. Ivermectin has been shown to be more effective for treating chronic uncomplicated strongyloidiasis. The efficacy and tolerability of these drugs in a series of patients treated from 1999 to 2002 at the Oliva Health Centre, Valencia, Spain, are reported. A total of 88 patients diagnosed of strongyloidiasis were treated using the following regimens: thiabendazole 25 mg/kg/12 h for 3 consecutive days in 31 patients; ivermectin 200 μg/kg as a single dose in 22 patients; and ivermectin 200 μg/kg for 2 consecutive days in 35 patients. The efficacy and side effects were recorded. A total of 65 patients were male, and 23 female. The mean age was 64 ± 12 years. Of the patients, 44 had worked barefoot in rice fields. Among the 31 patients treated with thiabendazole, 25 (78%) met the criteria for cure (the abs...

Efficacy and safety of ivermectin and thiabendazole in the treatment of strongyloidiasis

Epidemiology of Cyclospora cayetanensis: A review focusing in endemic areas.

The aim of this study was to estimate the frequency of human toxocariasis in Cauday district, Cajamarca, Peru, using a dot-ELISA test. From June to October 2005, a total of 256 adult subjects were studied. Blood samples were collected for serology by a dot-ELISA test and for hematological examination. Parasitological examination was also carried out in stool samples to check cross-reactions in the dot-ELISA. The frequency observed was 44.92%, with a significant higher proportion of positivity in male subjects. From subjects with positive serology, 45.6% had respiratory symptoms, 40.44% abdominal pain, 32.35% hepatic symptoms, 14.7% cutaneous signs, 13.23% ocular manifestations, 43.38% eosinophilia, and all of these were statistically associated to serology. Among the population evaluated, 90.23% (231/256) were parasitized. From subjects with positive serology, 92.17% had at least one intestinal parasite and the most frequent were: Blastocystis hominis (68.38%), Giardia lamblia (28.68%), Hymenolepis nana (20.0%), Ascaris lumbricoides (15.65%), Entamoeba histolytica/E. dispar (13.24%), Cyclospora cayetanensis (4.41%), Cryptosporidium sp. (1.47%), Enterobius vermicularis (0.87%), Strongyloides stercoralis (0.87%), Taenia sp. (0.87%), and Trichuris trichiura (0.87%). The rate of false positives in the dot-ELISA test was improved by serum absorption each with A. suum antigens, with a decrease of cross-reactions. In conclusion, human toxocariasis is highly frequent in this population and some risk factors like dog/cat ownership, presence of pets within house, and previous history of geophagia were observed in the present study.

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Frequency of human toxocariasis in a rural population from Cajamarca, Peru determined by DOT-ELISA test

Objetivo: Estandarizar la tecnica ELISA para el diagnostico de infeccion humana por Toxocara canis con antigeno excretado-secretado preparado en nuestro medio. Material y metodos: Se colecto huevos de T. canis y se les incubo con formol (2%) a 28oC hasta obtener larvas de tercer estadio, las que luego de ser liberadas fueron incubadas en RPMI a 37°C por 7 dias; se reemplazo el medio por otro similar y almaceno a -20°C. Se concentro el antigeno y se doso proteinas. Para la tecnica de ELISA se utilizo sueros de pacientes con toxocariasis y de ninos recien nacidos, como controles positivos y negativos, respectivamente, diluidos desde ¼ hasta 1/1024. Se sensibilizo placas de poliestireno con varias concentraciones de antigeno, utilizandose conjugado de peroxidasa e IgG de carnero anti IgG humana y sustrato OPD. Se realizo lectura de absorbancia a 492 nm con espectrofotometro (Multiskan plus labsystems), siendo el punto de corte el promedio aritmetico de la absorbancia de los sueros negativos mas 3 desviaciones estandar. Resultados: La concentracion optima del antigeno fue 50 ug/mL, la dilucion del suero 1/128, la dilucion del conjugado 1/1000 con densidad optica mayor a 0,241. Conclusiones: La tecnica de ELISA para diagnostico serologico de infeccion humana por Toxocara canis podria ser utilizada en estudios epidemiologicos en nuestro pais. Queda pendiente la evaluacion de su eficacia en futuros estudios.

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Estandarización de la técnica de ELISA para el diagnóstico de Toxocariasis humana

Objetivo: Estimar la seroprevalencia de toxocariosis humana en poblacion de la ciudad de Lima. Diseno: estudio transversal, la seleccion fue no aleatoria. Material y metodos: En pobladores de la ciudad de Lima que pertenecian a comunidades urbano marginales, se realizo entrevista y examen clinico, y se obtuvo una muestra de suero para procesar la tecnica de ELISA para detectar anticuerpos contra Toxocara. Tambien, se solicito muestras de heces para buscar parasitos intestinales que pudieran originar reacciones cruzadas en la serologia. Resultados: Se examino 553 personas, siendo 23,3% de ellos reactivos. No hubo diferencias en cuanto a sexo ni entre el resultado de ELISA y la presencia de anemia, leucocitosis, eosinofilia y parasitos intestinales. Los mayores de 15 anos tuvieron doble probabilidad de resultar reactivos que los menores de 15 anos. Disminucion de la agudeza visual fue el sintoma mas frecuente en los sujetos reactivos. Los parasitos intestinales mas frecuentes fueron Blastocystis hominis, Entamoeba coli, Giardia lamblia. Conclusiones: La toxocariosis humana es frecuente en la poblacion de Lima. No se observa asociacion estadistica entre el hallazgo de anemia y alteraciones de la formula leucocitaria con el resultado de ELISA. Es necesario desarrollar programas de difusion para detectar precozmente la infeccion y asi prevenirla.

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Toxocariosis humana: seroprevalencia en población de Lima mediante la técnica de ELISA

Resumen es: Objetivo: Determinar la actividad anti-Trypanosoma cruzi in vivo del aceite esencial de Cymbopogon citratus en ratones Balb/c. Diseno: Estudio experiment...

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Efecto anti-Trypanosoma cruzi del aceite esencial de Cymbopogon citratus (DC) Stapf (hierba luisa) en ratones Balb/c

Resumen es: OBJETIVO: Estimar la prevalencia de toxocariosis humana en sujetos con sintomatologia ocular sospechosa. MATERIAL Y METODOS: Se estudio personas atendid...

/pdf/toxocariosis-humana-en-pacientes-con-lesion-ocular-11iu9gl7ia.pdf

Carlos Sevilla

Papers

Frequency of human toxocariasis in a rural population from Cajamarca, Peru determined by DOT-ELISA test

Estandarización de la técnica de ELISA para el diagnóstico de Toxocariasis humana

Toxocariosis humana: seroprevalencia en población de Lima mediante la técnica de ELISA

Efecto anti-Trypanosoma cruzi del aceite esencial de Cymbopogon citratus (DC) Stapf (hierba luisa) en ratones Balb/c

Toxocariosis humana en pacientes con lesión ocular