[Ocular toxocariasis in Austria]

Toxocariasis and the clinical spectrum

Toxocara canis and T. cati are among the most widely distributed helminthic species in the world with a high zoonotic impact. Millions of people are infected^a and hundreds of thousands are suffering from toxocarosis, a disease encompassing four different entities: larva migrans visceralis (VLM) syndrome, ocular larva migrans (OLM) syndrome, covert toxocarosis (covT), common toxocarosis (comT) and neurotoxocarosis (NT). Toxocara infections in humans may remain clinically inapparent but may also induce severe diseases. This contribution gives a synoptic overview of the most important historical, clinical, diagnostic and therapeutical aspects of toxocarosis in humans.

Ocular toxocariasis: epidemiologic, anatomic, and therapeutic variations based on a survey of ophthalmic subspecialists

PURPOSE

To assess the current burden of ocular toxocariasis (OT) and to gain knowledge regarding the diagnostic and treatment practices used in the ophthalmologic community in the United States.

DESIGN

Web-based, cross-sectional survey.

PARTICIPANTS

Subspecialty ophthalmologists who are currently practicing in the United States.

METHODS

An electronic survey was sent to 3020 ophthalmologic subspecialists belonging to the American Uveitis Society (AUS), the American Society of Retina Specialists (ASRS), or the American Association for Pediatric Ophthalmology and Strabismus (AAPOS) to capture demographic, clinical, diagnostic, and treatment data on patients with OT seen in their practices between September 2009 and September 2010.

MAIN OUTCOME MEASURES

The demographic, epidemiologic, and clinical characteristics of each reported patient with OT.

RESULTS

A total of 159 patients with OT were reported by 559 respondents (19%). The median patient age was 11.5 years (range, 1-66 years). Seventy-two patients (45%) with OT lived in the Southern region of the United States. Thirty-one (69%) of 45 patients with OT owned a dog or cat. Vision loss was reported in 46 (85%) of 54 patients with OT; 32 (71%) of 45 patients had permanent vision loss, 13 patients (29%) had temporary vision loss, and duration of vision loss was unreported for 1 patient. Of the 32 patients with OT with permanent vision loss, 30 (94%) had a subretinal granulomatous mass/scar, peripheral granuloma with traction bands, or posterior pole granuloma noted on ophthalmologic examination. Subretinal granulomatous mass/scar, vitritis, and scotoma were the most common ophthalmologic signs found on examination of patients with OT.

CONCLUSIONS

Ocular toxocariasis continues to occur in the United States, where it affects mainly children and causes permanent vision loss in many patients. Healthcare professionals should counsel patients and their family members about prevention strategies in an effort to decrease infection rates and morbidity due to Toxocara. Further improvement of diagnostic and treatment tools is needed to assist ophthalmologists in treating patients with OT.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Toxocara-infestations in Austria: a study on the risk of infection of farmers, slaughterhouse staff, hunters and veterinarians

A total of 585 persons from several occupational groups (farmers, slaughterhouse staff, hunters, veterinarians) exposed to Toxocara infestations and 50 persons of a control group were tested for the presence of specific antibodies to the Toxocara canis antigen using an enzyme-linked immunosorbent assay and a western blot. Farmers showed the highest seroprevalence (44%), followed by veterinarians (27%), slaughterhouse staff (25%) and hunters (17%), whereas only 2% of the individuals of the control group were seropositive. Thus, the risk to Toxocara infestation is 39, 18, 16 and 9 times higher for farmers, veterinarians, slaughterhouse staff (some workers were part-time farmers) and for hunters, respectively, when compared to the control group. The main source of infection in rural areas seems to be (roaming) farm cats and dogs that have not been dewormed. The results are discussed with a view to potential risk factors and preventive measures, in terms of veterinary and human medicine.

Association of autoantibodies against small nuclear ribonucleoproteins (snRNPs) with symptomatic Toxocara canis infestation

Several studies have demonstrated the occurrence of autoantibodies in the course of infestations with helminth parasites and a number of target proteins have been identified. Sera from patients suffering from toxocarosis, a disease caused by the parasitic roundworm Toxocara canis, and from healthy individuals were tested for autoantibodies by immunofluorescence and immunoblot assays using HEp-2 cells as antigen. A considerable proportion of the sera from patients with toxocarosis-associated symptoms were autoantibody-positive, with a speckled staining pattern in the immunofluorescence test (62%) and with anti-snRNP reactivity in the immunoblot assay (98%). In contrast, significantly fewer sera from asymptomatic individuals scored positive in these assays (18% in the immunofluorescence test, P < 0.005; 24% in the immunoblot, P < 0.005). Although the causative link between Toxocara infestation and the occurrence of autoantibodies is still unclear, our results show that increased amounts of autoantibodies are associated with clinical symptoms of inflammation. Thus a serum test for autoantibodies in toxocarosis patients might be a valuable gatekeeper assay for the decision for or against anti-inflammatory treatment.

Treatment of ocular toxocariasis with albendazole

The purpose of this study was to evaluate the efficacy of combined albendazole and steroid treatment for uveitis caused by Toxocara canis in immunocompetent patients. Five patients (7 eyes) with ocular larva migrans syndrome (OLM) were used in this study. Toxocariasis was suspected based on clinical manifestations and confirmed by anti-toxocara IgG and Western blot analysis. Systemic albendazole (adults: 800 mg b.i.d.; children: 400 mg b.i.d.) was given in conjunction with steroids. Visual acuity before and after therapy, inflammatory response, side effects and toxicity were evaluated. Treatment resulted in an improved visual acuity in all patients. Mean initial Snellen visual acuity was 20/40, and mean final acuity was 20/20. There were no recurrences of uveitis throughout the observation period (average: 13.8 months; range: 3 days to 24 months). These findings suggest that albendazole, in combination with systemic steroids, is a useful regimen to treat ocular larva migrans syndrome.

Highlights of human toxocariasis

Human toxocariasis is a helminthozoonosis due to the migration of Toxocara species larvae through human organism. Humans become infected by ingesting either embryonated eggs from soil (geophagia, pica), dirty hands or raw vegetables, or larvae from undercooked giblets. The diagnosis relies upon sensitive immunological methods (ELISA or western-blot) which use Toxocara excretory-secretory antigens. Seroprevalence is high in developed countries, especially in rural areas, and also in some tropical islands. The clinical spectrum of the disease comprises four syndromes, namely visceral larva migrans, ocular larva migrans, and the more recently recognized "common" (in adults) and "covert" (in children) pictures. Therapy of ocular toxocariasis is primarily based upon corticosteroids use, when visceral larva migrans and few cases of common or covert toxocariasis can be treated by anthelmintics whose the most efficient appeared to be diethylcarbamazine. When diagnosed, all of these syndromes require thorough prevention of recontamination (especially by deworming pets) and sanitary education.