Toxocariasis--Visceral larva migrans, Ocular larva migrans
Source: U.S. Department of Health and Human Services, National Institutes of Health, National Library of
Medicine, MEDLINEplus Medical Encyclopedia
"An infection with the larval form of the dog or cat parasite which can affect the eyes, lungs, liver, brain and
heart...Young children with pica (who eat dirt and other inedible things) are at highest risk, but this
infection can also occur in adults. People can also become infected by eating raw liver..."

Source: U.S. Department of Health and Human Services, National Institutes of Health, National Library of
Medicine, MEDLINEplus Medical Encyclopedia
"Toxoplasmosisis found in humans worldwide and in many species of animals and birds. The cat is the
definitive host of the parasite. Human infection results from ingestion of contaminated soil, careless
handling of cat litter, ingestion of raw or undercooked meat (lamb, pork and beef), or transmission from a
mother to a fetus through the placenta..."

Toxicara ------------------------------------------- Visceral larva migrans --------------------------------------------------------

Toxocariasis is caused by Toxocara canis and, less frequently, Toxocara catis, which are intestinal
nematodes (roundworms) found in dogs and cats, respectively. In humans, toxocariasis is considered an
aberrant infection because humans are incidental hosts, and the parasites cannot completely mature in the
human body. Instead, the invasive larvae migrate for months through different organs until they are
overcome by the human inflammatory reaction and die. The larvae can survive in tissues for at least 9 years
and, possibly, for the life of the host.

Three clinical forms of toxocariasis are traditionally described; these include visceral larva migrans (VLM),
ocular larva migrans (OLM), and covert toxocariasis. A number of other disease manifestations have also
been attributed to these parasites.

Although sudden death due to T canis infestation has been reported, mortality is unusual. The major morbid
condition is decreased visual acuity caused by OLM. Evidence suggests that toxocariasis may be one of the
causative factors of allergic asthma.

Three syndromes of Toxocara infection are generally recognized. In children, covert toxocariasis is a mild,
subclinical, febrile illness. Symptoms can include cough, difficulty sleeping, abdominal pain, headaches,
and behavioral problems. On examination, hepatomegaly, lymphadenitis, and wheezing can be present.  

Visceral larva migrans is caused by the migration of larvae through the internal organs of humans and the
accompanying inflammatory reaction that results from this. A constellation of symptoms develops that
includes fatigue, fever, cough, bronchospasm, abdominal pain, headaches, and, occasionally, seizures. On
examination, hepatomegaly, lymphadenitis, and wheezing can be found. Occasionally, pleural effusions
develop. Chronic urticaria has been described. Severe cases can lead to myocarditis or respiratory failure.

Ocular larva migrans, which is caused by migration of larva into the posterior segment of the eye, tends to
occur in older children and young adults. Patients may present with decreased vision, red eye, or
leukokoria (white appearance of the pupil). Granulomas and chorioretinitis can be observed in the retina,
especially at the macula. Unilateral visual loss, retinal fibrosis, and retinal detachment occur. Serum
antibodies to Toxocara are often absent or present in low titers.

Although the main clinical manifestations are variable depending on the organs infected, the most common
characteristic is chronic eosinophilia. Other typical findings follow according to the involved organs. With
liver involvement, hepatomegaly, fever, and abdominal pain are common. With lung involvement,
pulmonary symptoms (eg, dyspnea, cough, chest tightness), bronchospasm, interstitial pneumonitis, and,
possibly, pleural effusion can be present. Ocular toxocariasis can induce decreased visual acuity, uveitis,
retinal granuloma, endophthalmitis, and other ocular lesions that often lead to sudden vision loss in the
affected eye. If the brain is involved, neurologic manifestations may occur, including seizures.

Toxocariasis is almost always a benign, asymptomatic, and self-limiting disease, although brain involvement
can cause severe morbidity. Brain involvement can evoke meningitis, encephalitis, or epilepsy. Ocular
involvement may cause loss of visual acuity or unilateral blindness. Pulmonary and hepatic forms can cause
protracted symptoms if the patient does not receive treatment.

Human Toxocara infection of the central nervous system and neurological disorders: a case-control study.
Infection with Toxocara canis is a common world-wide human helminthiasis, which rarely elicits central
nervous system (CNS) impairment. A case-control study to investigate this discrepancy was carried out, in
which the cases were 27 adult neurological inpatients for whom a definite aetiological diagnosis was
lacking, and for whom positive immunodiagnosis of toxocariasis had been obtained, both in cerebrospinal
fluid (CSF) and in serum. Two control groups were used. Controls were adult inpatients with other
neurological diseases who had no evidence of T. canis infection of the CNS. Multivariate logistic
regression analysis did not reveal any positive relation between case status and clinical signs. A significant
association was observed between case status and an elevated CSF cell count. Rural residence, ownership
of dogs, and dementia were shown to be risk factors for toxocaral infection of CNS. These results suggest
that migration of T. canis larvae in the human brain does not frequently induce a recognizable neurological
syndrome but is correlated with the association of several risk factors including exposure to dogs, a status
possibly responsible for repeated low-dose infections.

Toxocariasis--Cutaneous larvae migrans--Creeping eruption
Source: U.S. Department of Health and Human Services, National Institutes of Health, National Library of
Medicine, MEDLINEplus Medical Encyclopedia
"A skin rash caused by the migration of dog or cat hookworm larvae beneath the skin... The main risk factor
for this disease is contact with damp, sandy soil contaminated with cat and dog feces."