Agriculture Reference
In-Depth Information
Toxocara
larvae in eosinophilic granulomas in the liver of young children with extreme
eosinophilia, hepatomegaly, respiratory symptoms, anemia and geophagia, and introduced
the term VLM to describe this clinical syndrome (Beaver et al., 1952). Wilder found
nematode larvae in eosinophilic granulomas of enucleated eyes of children with suspected
retinoblastoma, providing the first description of the condition currently known as OLM
(Wilder, 1950).
Classical VLM occurs typically in children aged 2-7 years, but infections in adults, at least
some of which are acquired by ingesting raw organs of paratenic hosts, are relatively
frequent in East Asia (Akao & Ohta, 2007). The full-blown VLM syndrome usually includes
fever, lower respiratory symptoms such as cough, dyspnea and bronchospasm associated
with larval migration, hepatomegaly, abdominal pain and decreased appetite. Laboratory
findings include hypergammaglobulinemia, increased isohemagglutinin titres to A and B
blood group antigens, anaemia and leukocytosis with marked eosinophilia (Jacob et al.,
1994). As a rule, seropositive subjects in population-based surveys are asymptomatic or
have rather nonspecific and mild symptoms. A case-control study in Ireland led to the
description of a new clinical entity in seropositive children, called “covert toxocariasis”,
comprising mainly fever, headache, behavioural and sleep disturbances, cough, anorexia,
abdominal pain, hepatomegaly, nausea and vomiting (Taylor et al., 1987). Another case-
control study, in French adults, led to the definition of “common toxocariasis”, a syndrome
comprising chronic dyspnea and weakness, cutaneous rash and pruritus, as well as
abdominal pain (Glickman et al., 1987).
The liver is the most commonly affected visceral organ. Typical hepatic granulomas have
multinucleated giant cells and epithelioid cells surrounding necrotic debris or amorphous
eosinophilic material. Eosinophils and mononuclear cells are often seen in the outer layers of
the granulomas (Musso et al., 2007). On computed tomography, hepatic lesions are typically
ill-defined, low-attenuating nodules (Cameron et al., 1997) that have sometimes been
confounded with metastatic cancer (Ota et al., 2009).
The cutaneous manifestations of human toxocariasis have been recently reviewed (Gavignet
et al., 2008) and include chronic prurigo, pruritus and urticaria, eczema, exanthema
(Bernardeschi et al., 2011), and vasculitis.
Central nervous system involvement in toxocariasis comprises eosinophilic meningitis and
encephalitis (Moreira-Silva et al., 2004), myelitis (Lee et al., 2009), cerebral vasculitis (Helbok
et al., 2007) and optic neuritis, while manifestations of peripheral nervous system
involvement include radiculitis (Moreira-Silva et al., 2004) and cranial nerve palsy (Finsterer
& Auer, 2007). Central nervous system involvement in VLM has been associated with
epilepsy (Woodruff et al., 1966), behavioral changes and cognitive deficits.
Toxocara
may
represent a co-factor in idiopathic seizures (Critchley et al., 1982), and especially in partial
epilepsy (Nicoletti et al., 2007). The presence of granulomas in the brain has been suggested
to elicit focal seizures (Critchley et al., 1982). Research to verify increased risk of cognitive
deficits in infected children has remained inconclusive (Jarosz et al., 2010).
There are very few controlled trials on anthelmintic drugs for VLM in the literature. Since
parasitological cure in patients cannot be assessed, the end-point of published trials is a
decrease in the severity of clinical signs and symptoms. A dose of 500 mg of albendazole
twice a day for 5 days is currently recommended. Albendazole seems to be superior to
thiabendazole (50 mg/kg of body weight daily for 3-7 days) (Stürchler et al., 1989).
Diethylcarbamazine (3-4 mg/kg of body weight daily for 21 days, starting at 25 mg/day
and increasing the dose progressively) is also effective (Magnaval, 1995). Most human
