Localised myelitis caused by visceral larva migrans due to Ascaris suum masquerading as an isolated spinal cord tumour

Immunoblot for the detection of Ascaris suum-specific antibodies in patients with visceral larva migrans (VLM) syndrome

Visceral larva migrans (VLM) syndrome caused by Toxocara canis larvae was first described in the 1950s. The role of other nematode larvae, i.e. the pig roundworm Ascaris suum as a causative agent of visceral larva migrans-associated symptoms like general malaise, cough, liver dysfunction, hypereosinophilia with hepatomegaly and/or pneumonia, was discussed controversially during the last decades. Recent serological screening studies for specific A. suum antibodies carried out in the Netherlands and Sweden yielded remarkable high seroprevalences, while a number of case reports from Japan report pulmonal, hepatic and cerebral symptoms caused by A. suum larvae after ingestion of infected raw meat (liver) or contaminated vegetables. We present here a sensitive and specific larval excretory-secretory (E/S) antigen-based immunoblot (As-IB) for the serodiagnosis of A. suum-infected patients suffering from symptoms associated to the VLM syndrome. In total, 34 sera from patients with hypereosinophilia and other clinical symptoms associated to the VLM syndrome tested negative for Toxocara sp. antibodies but positive in our newly established As-IB, 30 sera from healthy volunteers, 53 sera from patients with clinically and serologically confirmed toxocarosis and other helminthoses as well as 3 sera from patients with intestinal ascariosis due to Ascaris lumbricoides were included in the study. When evaluated with 30 sera from healthy volunteers and 53 sera from patients suffering from different helminthoses, the calculated specificity of our new As-IB is 95%. Problems hampering the establishment of simple serological screening tests for specific A. suum antibodies, like extensive antigenic similarities between the nematodes Ascaris and Toxocara or the absence of suitable experimental animals, are discussed. We assume that specific serological testing for antibodies of A. suum is very important for the treatment of individual patients on one hand and seroepidemiological investigations will help to clarify routes of transmission on the other hand. Further studies will be necessary to learn more about the extent of A. suum as a causative agent of the VLM syndrome and the role of pigs and their manure as the main source of human Ascaris infections in Austria and other industrialized countries.

Helminthic invasion of the central nervous system: many roads lead to Rome

Invasion of the central nervous system (CNS) by parasitic worms often represents most severe complication of human helminthiasis. The pathways from the portal of entry to the CNS are manifold and differ from species to species. In this mini-review, we analysed the contemporary knowledge and current concepts of the routes pathogenic helminths take to gain access to brain, spinal cord and subarachnoid space.

Toxocariasis mimicking liver, lung, and spinal cord metastases from retinoblastoma

A boy with bilateral retinoblastoma underwent metastatic surveillance for increased risk of systemic and central nervous system metastasis because of the extensive choroid and optic nerve invasion in his enucleated eye. Two years after finishing chemotherapy, surveillance MRI showed multiple new liver, lung and spinal cord lesions. High Toxocara antibody titers, eosinophilia, and elevated IgE levels supported a diagnosis of toxocariasis, rather than retinoblastoma metastasis. This is the first report of early, asymptomatic spinal cord toxocariasis diagnosed incidentally through metastatic surveillance.

Migration behaviour and pathogenesis of five ascarid nematode species in the Mongolian gerbilMeriones unguiculatus

To understand the characteristic features of the Mongolian gerbil,Meriones unguiculatus,as an animal model of ascarid infections, the migration behaviour and pathogenesis of larvae were investigated in experimentally infected gerbils. Embryonated eggs from each ofToxocara canis,Baylisascaris procyonis, B. transfuga, Ascaris suum, andA. lumbricoideswere orally inoculated into gerbils and larvae were recovered from various organs at designated periods. InT. canis-infected gerbils, larvae were present in the liver 3 days after infection and in the skeletal muscle and brain via the heart and lungs at a similar rate. InB. procyonis- andB. transfuga-infected gerbils, larvae were present in the lungs within 24 h after infection, with some having reached the brain by that time. After 24 h, larvae ofB. procyonistended to accumulate in the brain, while those ofB. transfugaaccumulated in skeletal muscles. InA. suum- andA. lumbricoides-infected gerbils, larvae remained in the liver on day 5 post-infection and elicited pulmonary haemorrhagic lesions, which disappeared 7 days after initial infection. Thereafter, no larvae of any type were recovered. Ocular manifestations were frequently observed inT. canis- andB. procyonisinfected gerbils, but were rare inB. transfuga-infected gerbils. In the cases ofA. suumandA. lumbricoides, migration to the central nervous system and eyes was extremely rare, and larvae had disappeared by 2 weeks post-infection. Fatal neurological disturbances were observed inB. procyonis-infected gerbils, whereas irreversible non-fatal neurological symptoms were observed in the case ofB. transfuga.

MRI studies of spinal visceral larva migrans syndrome

We report serial MR findings in four patients with myelitis caused by visceral larva migrans syndrome due to Toxocara canis or Ascaris suum infection. MR imaging revealed spinal cord swelling with or without gadolinium enhancement in three patients. T2-weighted images showed high signal intensities preferentially located in both lateral and posterior columns. Antihelmintic and corticosteroid treatment yielded improvement in neurologic deficits and spinal lesions. However, one patient with T. canis infection relapsed associated with reappearance of MRI abnormalities.

Cross-reactions with Ascaris suum antigens of sera from mice infected with A. suum, Toxocara canis, and Angiostrongylus cantonensis

Ascaris suum larval excretory-secretory (AsES) antigen and larval (AsLA) as well as adult somatic antigen (AsAA) which were thought to be possibly helpful in the diagnosis of visceral larva migrans (VLM) due to A. suum infection were investigated in the present study. Serum taken from mice orally inoculated with approximately 250 embryonated eggs of A. suum or Toxocara canis, or 40 third-stage larvae of Angiostrongylus cantonensis were assessed by enzyme-linked immunosorbent assay (ELISA) using the AsES antigen, AsLA or AsAA at 1, 2, 3, 4, 6 and 8 weeks post infection (WPI). The titer of serum IgG from mice infected with A. suum increased from 1 WPI and a peak at 4 WPI was observed when it reached approximately three times the level of uninfected control mice. Thereafter, it decreased gradually but remained high as found from 6 to 8 WPI. No cross-reactions of heterologous serum IgG against AsES antigen was observed, whereas heterologous serum IgM exhibited significant cross-reactions to AsES antigen. Cross-reactivities to AsLA and AsAA by heterologous serum IgG as well as IgM antibodies were also observed in the trial. Altogether, the AsES antigen apparently seemed to be superior to the other two somatic antigens when used in the diagnosis of A. suum-induced VLM with serum IgG as tested by ELISA. Moreover, it was the first report to test the possibly antigenic cross-reactivity between A. suum and A. cantonensis.

Toxocariasis of the central nervous system: with report of two cases

Clinical involvement of the nervous system in visceral larva migrans due to Toxocara is rare, although in experimental animals the larvae frequently migrate to the brain. A review of the literature from the early 50's to date found 29 cases of brain involvement in toxocariasis. In 20 cases, various clinical and laboratory manifestations of eosinophilic meningitis, encephalitis, myelitis or radiculopathy were reported. We report two children with neurological manifestations, in which there was cerebrospinal fluid pleocytosis with marked eosinophilia and a positive serology for Toxocara both in serum and CSF. Serology for Schistosoma mansoni, Cysticercus cellulosae, Toxoplasma and cytomegalovirus were negative in CSF, that was sterile in both cases. Improvement of signs and symptoms after specific treatment (albendazole or thiabendazole) was observed in the two cases. A summary of data described in the 25 cases previously reported is presented and we conclude that in cases of encephalitis and myelitis with cerebrospinal fluid pleocytosis and eosinophilia, parasitic infection of the central nervous system should be suspected and serology should be performed to establish the correct diagnosis and treatment.