Human toxocariasis, a silent helminthic disease revealed in Savannakhet, Lao PDR

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Abstract

Toxocariasis is a zoonotic helminthiasis caused by the migrating larvae of Toxocara canis and T. cati, common roundworms of dogs and cats. Our previous study in Savannakhet Province of Lao PDR showed an infection rate of 44.1% of Toxocara spp. in dogs. Thus, we investigate if this previous high prevalence in the definitive hosts influenced the occurrence of human toxocariasis. For that we used a 38 kDa recombinant protein derived from T. canis larvae excretion secretion products in ELISA. Human serum samples were collected in the Lahanam area of Savannakhet province. The population attending the study in Lahanam village were aged from 7 to 59 years old (y/o) 65.9% (54/82) were male and 34.1% (28/82) were female. The total percentage of seropositivity to Toxocara sp. was 30.4% (25/82). Males were more likely to test positive for toxocariasis with a risk ratio of 2.70 (CI95 0.87–4.93). No significant differences between ages were seen. However, it was possible to observe an increase of optical density (OD) values in ELISA according to age. The awareness of the health system on the high prevalence of seropositivity to Toxocara sp. in Savannakhet can prevent irreversible consequences as permanent vision loss and seizures caused by this silent chronic disease revealed in the Lahanam area.

Highlights

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The first survey for human toxocariasis was carried out in Savannakhet, Lao-PDR.
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Seropositivity was higher in males than females.
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Despite no reported clinical cases of toxocariasis 30.4% of seropositivity was found.
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People are at risk of exposure to Toxocara sp. larvae in Savannakhet, Lao-PDR.

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Most cited references 30

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

D. Despommier (2003)

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.

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Demography of domestic dogs in rural and urban areas of the Coquimbo region of Chile and implications for disease transmission.

G Acosta-Jamett, S. Cleaveland, A.A. Cunningham … (2010)

A cross-sectional household questionnaire survey was conducted along two transects (80 and 45km long) from Coquimbo and Ovalle cities to the Fray Jorge National Park (FJNP) in the Coquimbo region of Chile in 2005-2007 to investigate the demography of dogs in the context of a study of canine infectious diseases. Data were collected on the number of dogs per household, fecundity, mortality, and sex and age distribution. The results from 1021 households indicated that dog ownership was common, with a higher proportion of households owning dogs in rural areas (89%), than in towns (63%) or cities (49%). Dog density ranged from 1380+/-183 to 1509+/-972 dogs km(-2) in cities, from 119+/-18 to 1544+/-172 dogs km(-2) in towns, and from 1.0+/-0.4 to 15.9+/-0.4 dogs km(-2) in rural sites. The dog population was estimated to be growing at 20% in cities, 19% in towns and 9% in rural areas. The human:dog ratio ranged from 5.2 to 6.2 in cities, from 2.3 to 5.3 in towns, and from 1.1 to 2.1 in rural areas. A high percentage of owned dogs was always allowed to roam freely in the different areas (27%, 50% and 67% in cities, towns and rural areas, respectively). Observations of free-roaming dogs of unknown owner were reported from a greater proportion of respondents in cities (74%), followed by towns (51%) and finally by rural areas (21%). Overall only 3% of dogs had been castrated. In addition, only 29% of dogs were reported to have been vaccinated against canine distemper virus (CDV) and 30% against canine parvovirus (CPV). The higher population size and density, higher growth rate and a higher turnover of domestic dogs in urban than in rural areas and the poorly supervised and inadequately vaccinated dog populations in urban areas suggest that urban areas are more likely to provide suitable conditions for dogs to acts as reservoirs of pathogenic infections. Copyright 2010 Elsevier B.V. All rights reserved.

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Immunodiagnosis of toxocarosis in humans: evaluation of a new enzyme-linked immunosorbent assay kit.

P Jacquier, Y Stingelin, B. Gottstein … (1991)

Excretory/secretory (E/S) antigen derived from second-stage larvae of Toxocara canis maintained in defined medium in vitro has been well established worldwide for the immunodiagnosis of human toxocarosis by enzyme-linked immunosorbent assay. Such an enzyme-linked immunosorbent assay, based on the detection of human anti-T. canis (E/S antigen) serum immunoglobulin G, has recently been commercialized by Biokema-Affinity Products (Crissier-Lausanne, Switzerland). This commercial test kit was evaluated with regard to its application in a routine diagnostic laboratory and the reliability of the results. Of 78 patients with suspected clinical toxocarosis, 71 had anti-T. canis antibodies (positive serological result) corresponding to a diagnostic sensitivity of 91%; 14% of serum samples (n = 199) from patients with protozoan or with helminthic infections also showed positive reactions mainly related to infections with Trichinella, Strongyloides, and Fasciola species. An epidemiological study with 1,000 serum samples from randomly selected healthy blood donors and children in Switzerland demonstrated a seroprevalence of 2.7%. The test kit under evaluation had an overall diagnostic sensitivity of 91% and a relative specificity of 86%, the latter being related to some protozoan and helminthic infections. Because of the scarcity of such infections, potential cross-reactivity does not play a major role under the conditions found in the middle part of Europe. In conclusion, the application of the test kit provided for use in this study can be recommended for routine diagnostic use.

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Author and article information

Contributors

Megumi Sato

Marcello Otake Sato

Journal

Journal ID (nlm-ta): One Health

Journal ID (iso-abbrev): One Health

Title: One Health

Publisher: Elsevier

ISSN (Electronic): 2352-7714

Publication date PMC-release: 27 October 2020

Publication date Collection: 20 December 2020

Publication date (Electronic): 27 October 2020

Volume: 11

Electronic Location Identifier: 100191

Affiliations

[a ]Graduate School of Health Sciences, Niigata University, Niigata, Niigata, Japan

[b ]Department of Tropical Medicine and Parasitology, Dokkyo Medical University, Mibu, Japan

[c ]Department of Helminthology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand

[d ]Station of Malariology, Parasitology, and Entomology of Savannakhet Province, Savannakhet, Lao PDR

[e ]National Institute of Public Health, Ministry of Health, Vientiane, Lao PDR

[f ]National Institute of Infectious Diseases, Tokyo, Japan

[g ]Graduate School of International Health Development, Nagasaki University, Japan

Author notes

[* ]Corresponding authors. satomeg@ 123456clg.niigata-u.ac.jp marcello@ 123456dokkyomed.ac.jp

[1]

Contributed equally for this work.

Article

Publisher Item ID: S2352-7714(20)30292-5 Publisher ID: 100191

DOI: 10.1016/j.onehlt.2020.100191

PMC ID: 7772625

SO-VID: 603cf09a-7dc9-4b15-9a86-96375b027457

License:

This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

History

Date received : 18 August 2020

Date revision received : 23 October 2020

Date accepted : 23 October 2020

Human toxocariasis, a silent helminthic disease revealed in Savannakhet, Lao PDR

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Chinese Journal of Schistosomiasis Control

Most cited references 30

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

Demography of domestic dogs in rural and urban areas of the Coquimbo region of Chile and implications for disease transmission.

Immunodiagnosis of toxocarosis in humans: evaluation of a new enzyme-linked immunosorbent assay kit.

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