Toxocariasis is a tropical disease caused by the roundworm, toxocara. It is transmitted to humans with the accidental consumption of soil contaminated with the eggs of the parasite excreted in cat or dog feces [1]. The eggs release larvae which puncture the intestinal wall and migrate through the circulatory system to various organs of the human body (brain, eyes, heart, liver, lungs and muscle) where they cause inflammation leading to symptoms of toxocariasis.

The clinical presentation of toxocariasis depends upon the organ system involved and can be classified as:

• Visceral larva migrans (VLM) - involving all major organs
• Ocular larva migrans (OLM) - involving the eyes and the optic nerve
• A covert form which is difficult to diagnose.

VLM affects mainly children under the age of five [2] who present with fever, pain in abdomen, hepatosplenomegaly, eosinophilia, bronchospasm, seizures, neuropsychiatric or cognitive symptoms or encephalopathy depending on the organ system involved.

OLM, on the other hand, affects children in the five to ten year age group and is associated with unilateral visual impairment and, strabismus [3]. In severe cases of OLM, there may be retinal invasion with granuloma formation in the posterior pole, heteropia and macular detachment [4]. There may also be endophthalmitis, papillitis followed secondarily by glaucoma and blindness.

The covert form of toxocariasis can present insidiously with headache, coughing, abdominal pain and hepatosplenomegaly or symptoms resembling asthma e.g. dyspnea, wheezing and coughing [1] [5].

• Fever

  Symptoms were fever, inactivity, weakness, tiredness and loss of appetite. She was followed clinically and with blood samples throughout a period of three years and four months. [ncbi.nlm.nih.gov]

• Epilepsy

  Several studies have evidenced high seropositivity rates for T. canis among people with epilepsy suggesting that toxocariasis could play a role in the incidence of epilepsy in endemic areas. [ncbi.nlm.nih.gov]

  […] that toxocariasis may be an etiologic factor in epilepsy. 177 This hypothesis remains unsettled. [epilepsy.com]

  This increased for those with late-onset partial epilepsy to an OR of 18.22 (95% CI 2.10 to 158.10). [neurology.org]

• Vietnamese

  Comparison of 264 nucleotides of internal transcribed spacer 2 (ITS2) of ribosomal DNA was done between our Vietnamese Toxocara canis and other Toxocara geographical isolates, including Chinese T. canis, Japanese T. canis, Sri Lankan T. canis, and Iranian [ncbi.nlm.nih.gov]

  […] pheasant Lophura hatinensis Lophura hatinhensis Vietnam fireback Vietnamese pheasant Lorius garulus Lorius garrulus chattering lory Lucilia ampullacae Lucilia ampullacea Lucillia Lucilia Phaenicia Lucillia sp. [julesberman.info]

• Cough

  The covert form of toxocariasis can present insidiously with headache, coughing, abdominal pain and hepatosplenomegaly or symptoms resembling asthma e.g. dyspnea, wheezing and coughing. [symptoma.com]

  which may involve many organs, but pulmonary symptoms such as coughing and wheezing and allergic symptoms are seen in more than 80% of patients. [ncbi.nlm.nih.gov]

  Other possible symptoms include cough, poor sleep, headaches, and abdominal pain. Children may show signs of infected lymph nodes, a swollen liver, or wheezing. [news-medical.net]

  Signs and Symptoms Many kids won't have symptoms, but if they do, they can include fever, cough or wheezing, abdominal pain, enlarged liver or spleen, poor appetite, a rash that sometimes looks like hives, and enlarged lymph nodes ("swollen glands"). [brennerchildrens.org]

• Abdominal Pain

  We report a 13-year-old girl with recurrent abdominal pain who, despite positive toxocara serology, was extensively investigated for other abdominal pathology. [ncbi.nlm.nih.gov]

  Other possible symptoms include cough, poor sleep, headaches, and abdominal pain. Children may show signs of infected lymph nodes, a swollen liver, or wheezing. [news-medical.net]

• Lower Abdominal Pain

  A 23-year-old woman with fever, myalgias, stridor, pelvic cramping, lower abdominal pain, and profound eosinophilia was presumed to have toxocariasis. [ncbi.nlm.nih.gov]

• Morning Stiffness

  A 3-year-old girl was referred to our service with severe painful chronic polyarthritis for a period longer than 10 weeks and morning stiffness of 30min. Dog contact exposure history in the recreational areas of neighborhood was reported. [ncbi.nlm.nih.gov]

• Eczema

  Skin manifestations such as itch, eczema / dermatitis, and urticaria are sometimes present. Covert toxocariasis Non-specific symptoms such as cough, abdominal pain, headache, sleep disorder, vomiting, enlarged liver, and occasionally a rash. [dermnetnz.org]

  No statistical excess of risk was observed for patients with atopic dermatitis, pruritus or non-atopic eczema. Conclusion: The authors conclude that patients suffering from urticaria or prurigo should be tested for Toxocara infection. [karger.com]

  Other cutaneous manifestations include chronic pruritus, chronic prurigo, transient rash, different forms of eczema, hypodermic nodules and vasculitis [ 44 ]. [link.springer.com]

  Dermatological changes, such as rash, pruritus, eczema, panniculitis, urticaria and vasculitis, have also been detected in some VLM cases [ 63 ]. [idpjournal.biomedcentral.com]

• Insect Bite

  Various triggering factors, such as myeloproliferative disorders, lymphoma, infections/infestations, insect bites and drugs have been reported. [ncbi.nlm.nih.gov]

• Memory Impairment

  Preliminary data have also suggested a possible link between significant memory impairment and cytokine production associated with T. canis infection. [ncbi.nlm.nih.gov]

  Furthermore, these levels were particularly raised at 35 and 42 days postinfection, times that coincide with observed behavioral alterations, most notably memory impairment. [cmr.asm.org]

• Radiculopathy

  In 20 cases, various clinical and laboratory manifestations of eosinophilic meningitis, encephalitis, myelitis or radiculopathy were reported. [ncbi.nlm.nih.gov]

The diagnosis of the disease is based mainly on the history and symptoms of multi-organ or ocular involvement. Serological testing and biopsy or autopsy specimens showing larvae help to confirm the diagnosis.

Toxocariasis should be suspected in a child with a history of pica, contact with dogs or cats, clinical signs of unexplained febrile illness with hepatosplenomegaly, eosinophilia or ocular symptoms. A complete blood count will reveal eosinophilia, although it may be absent in some cases of OLM and covert toxocariasis.

Confirmation of the diagnosis relies on the laboratory demonstration of specific anti-toxocara antibodies in either the serum or aqueous or vitreous fluid of the infected individual. The enzyme-linked immunosorbent assay (ELISA) test which uses antigens from the second stage larva is the best indirect test for the diagnosis of toxocariasis. Although histopathology of tissue samples with the identification of larvae or the detection of larval DNA in tissues is definitive, it is difficult to obtain such infected tissue samples [6] [7].

The diagnosis of OLM is based on clinical criteria and ophthalmic examination as immunodiagnostic tests are not as reliable as for VLM [8]. Neuroimaging, especially magnetic resonance imaging (MRI) is recommended to detect granulomas in the cortical or subcortical layers of the brain in patients with neuropsychiatric symptoms. MRI findings combined with cerebrospinal detection of eosinophil is indicative of toxocara infection.

• Wuchereria Bancrofti

  Filarial-specific IgG4 response correlates with active Wuchereria bancrofti infection. J. Immunol. 145 : 4298 -4305. Lynch, N. R., L. K. Wilkes, A. N. Hodgen, and K. J. Turner. 1988. Specificity of Toxocara ELISA in tropical population. [doi.org]

• Brugia Malayi

  A recombinant antigen-based IgG4-ELISA for the specific and sensitive detection of Brugia malayi infection. Trans. R. Soc. Trop. Med. Hyg. 95 : 280 -284. Schantz, P. M. 1989. Toxocara larva migrans now. Am. J. Trop. Med. Hyg. 41 : 21 -34. Shetty, A. [doi.org]

1. Global Health - Division of Parasitic Diseases and Malaria (2013) Parasites - Toxocariasis (also known as Roundworm Infection). Atlanta, GA: Centers for Disease Control and Prevention.
2. Worley G, Green IA, Frothingham TE. Toxocara canis infection: clinical and epidemiological associations with seropositivity in kindergarten children. J. Infect. Dis. 1984;149:591-597.
3. Dinning WJ, Gillespie SH, Cooling RI, Maizels RM. Toxocariasis: a practical approach to management of ocular disease. Eye. 1988; 2:580-582.
4. Small KW, McCuen BW, De Juan E, Machemer R. Surgical management of retinal retraction caused by toxocariasis. Am. J. Ophthalmol.1989; 108:10-14.
5. Barry MA, Weatherhead JE, Hotez PJ, Woc-Colburn L. Childhood parasitic infections endemic to the United States. Pediatric clinics of North America. 2013; 60: 471–485.
6. Magnaval JF, Glickman LT, Dorchies P, Morassin B. Highlights of human toxocariasis. Korean J. Parasit.2001; 39:1-11.
7. Smith HV. Antibody reactivity in toxocariasis. In: LEWIS, J.W. & MAIZELS, R.M., ed.Toxocara and toxocariasis: clinical, epidemiological and molecular perspectives. London, Institute of Biology.1993; p. 91-109.
8. Schantz PM. Toxocara larva migrans now. Am J Trop Med Hyg. 1989;41(Suppl.):21-34.