Human Toxocariasis is a helminthozoonosis due to the infestation of humans by ascarid larvae belonging to the genus Toxocara (Wilder, 1950). -The first description was made in the early 1950's, and has been regarded as an uncommon paediatric disease. Toxocariasis is the most prevalent helminthiasis in industrialized countries. Their definitive hosts are the domestic dogs and cats
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INTRODUCTION
-Human Toxocariasis is a helminthozoonosis due to the
infestation of humans by ascarid larvae belonging to
the genus Toxocara (Wilder, 1950).
-The first description was made in the early 1950's, and
has been regarded as an uncommon paediatric disease.
Toxocariasis is the most prevalent helminthiasis in
industrialized countries.
Their definitive hosts are the domestic dogs and cats.
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CONT’D
There are two main
syndromes:
- Visceral Larva Migrans
(VLM): With diseases
associated with the major
organs.
- Ocular Larva Migrans (OLM):
Effects on the host are
restricted to the eye and the
optic nerve.
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CONT’D
Presentations typically include posterior uveitis with symptoms and signs
such as reduced vision, photophobia, floaters, and leukocoria(Stewart et al.,
2005).
Management includes quieting inflammation, eliminating the offending
organism, and repairing vitreoretinal sequelae. Prognosis is often correlated
to presentation and the degree to which sequelae are present. Vision
typically ranges from 20/40 to 20/400.
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ETIOLOGY
Ocular Toxocariasis is caused by Toxocara canis and less frequently by
other roundworms such as Toxocara cati (Rubinsky et al., 2010).
Individuals become infected with Toxocara when they unintentionally
ingest embryonated eggs or larvae that have been shed in the feces of
infected animals or uncooked paratenic hosts (Despommier, 2003).
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EPIDEMIOLOGY
-Toxocariasis is found worldwide, although the majority of cases occur
where dogs and cats are kept in close proximity to humans.
-Seroprevalence is higher in developing countries, but can be
considerable in first world countries.
-In Bali, St. Lucia, Nepal and other countries, seroprevalence is over 50%.
Permanent vision loss occurs in 700 of these cases (Fan et al., 2013).
Previous to 2007, the U.S. seroprevalence was thought to be around 5%
in children (Fan et al., 2013). However, Won et al. discovered that U.S.
seroprevalence is actually 14% for the population at large.
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CONT’D
-In the United States, the seroprevalence of Toxocara was estimated at
13.9% based on data from 1988 to 1994 (Won et al., 2008). In a subsequent
study based on data from 2011 to 2014, the seroprevalence was estimated
to be 5% (Liu et al., 2011).
-This number is much higher in other parts of the world, such as Colombia,
where up to 81% of children have been infected (Hotez et al., 2009).
-Prevalence rates of 40% or more have been reported in Peru and Brazil.
-In 2010, the CDC reported an average age in the United States of 8.1 years
with a range from 1-60 years of age. Between 4.6% and 23% of U.S.
children have been infected with the dog roundworm egg
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CONT’D
-In children, the seroprevalence of Toxocara infection has been estimated
to be 4% – 31% in developed countries and may increase to 86% in tropical
regions, where environmental conditions favour the transmission of
geohelminths.
-There is relatively high seroprevalence of Toxocara in different parts of
Nigeria with 29.8% seroprevalence in Jos, Plateau state and 86.1% among
children in Southern Nigeria.
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WHAT CAN BE DONE?
MEDICAL CARE
-Albendazole
-Benzimidazole (thiabendazole (TBZ), mebendazole
(MBZ) and diethylcarbamazine(DEC) ).
-Corticosteroids
SURGICAL CARE
-Pars Plana Vitrectomy
-Perfluorocarbon Liquids Injection
-Endolaser
-Cryotherapy
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PREVENTION
-Control the spread of dog feces, and to lesser
extent cat feces, also helps limit exposure.
-Regular treatment of pets with antiparasitics
helps reduce worm burdens and limits the
number of eggs deposited in soil.
-Since public parks and playgrounds have
become zones of disease acquisition, it would
be wise to keep children in less overcrowded
places.
-Hand Hygiene.
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REFERENCES
-Beaver PC, Snyder CH, Carrera GM, Dent JH, Lafferty JW. Chronic eosinophilia due to visceral larva
migrans; report of three cases. Pediatrics. 1952;9:7–19.
-Despommier D. Toxocariasis: clinical aspects, epidemiology, medical ecology, and molecular aspects. Clin
Microbiol Rev. 2003;16:265–272.
-Fan CK, Hung CC, Du WY, Liao CW, Su KE. Seroepidemiology of Toxocara canis infection among mountain
aboriginal schoolchildren living in contaminated districts in eastern Taiwan. Trop Med Int Health.
2004;9:1312–1318.
-Rubinsky-Elefant G, Hirata CE, Yamamoto JH, Ferreira MU. Human toxocariasis: diagnosis, worldwide
seroprevalences and clinical expression of the systemic and ocular forms. Ann Trop Med Parasitol.
2010;104:3–23.
-Stensvold CR, Skov J, Moller LN, Jensen PM, Kapel CM, Petersen E, Nielsen HV. Seroprevalence of human
toxocariasis in Denmark. Clin Vaccine Immunol. 2009;16:1372–1373.
-Stewart JM, Cubillan LD, Cunningham ET., Jr Prevalence, clinical features, and causes of vision loss among
patients with ocular toxocariasis. Retina. 2005;25:1005–1013.
-Wilder, H. C. (1950). Nematode endopthalmitis. Transactions of the Americam Academy of Opthalmology
and Otorlarynology 55, 99–109.
-Most cases are reported from the South-eastern United States, Mexico, Hawaii, East and Western Europe, the Philippines, and South Africa (Fan et al., 2013).
-In many countries, toxocariasis is considered very rare. Approximately 10,000 clinical cases are seen a year in the U.S., with 10% being OLM. Permanent vision loss occurs in 700 of these cases
