8 Management and Treatment Options for Human Toxocariasis
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8 Management and Treatment Options for Human Toxocariasis Jean-Franc¸ois Magnaval1 and Lawrence T. Glickman2 1Department of Parasitology, Rangueil University Hospital, Toulouse, France 2Department of Veterinary Pathobiology, School of Veterinary Medicine, Purdue University, West Lafayette, Indiana, USA Introduction maglobulinaemia. In industrialized countries, VLM is relatively uncommon, and a review of Human toxocariasis is a zoonosis caused by in- the literature from 1952 to 1979 found only 970 fective larvae of Toxocara canis (Beaver, 1956) or reports (Ehrard and Kernbaum, 1979). Toxocara cati (Nagakura et al., 1990). These ascarids Other forms of toxocaral disease were iden- are commonly found in the tissues (larvae) and tified in the 1980s by two case–control studies intestinal tract (adult worms) of dogs and cats, conducted in adults in France (Glickman et al., respectively. Infection results from ingestion of 1987) and in children in Ireland (Taylor et al., embryonated eggs in soil (Glickman and Schantz, 1988). In French adults, toxocariasis was charac- 1981) or on contaminated fomites (Vazquez Tsuji terized clinically by weakness, pruritus, rash, dif- et al., 1997). Live larvae can be ingested with raw ficulty in breathing and abdominal pain. or undercooked meat, giblets or offal (Nagakura Significant laboratory findings included mild per- et al., 1989; Stu¨rchler et al., 1990; Fan et al., 2004; ipheral eosinophilia and increased total serum Taira et al., 2004). IgE. This syndrome was termed ‘common toxo- Toxocara infection results in a wide variety of cariasis’ in adults (Magnaval et al., 1994a). In syndromes in humans, although most infections Ireland, the most frequent clinical findings in chil- are probably subclinical. Visceral larva migrans dren infected with Toxocara larvae included fever, (VLM) was first described in 1952, in children anorexia, headache, abdominal pain, nausea, with an enlarged liver and hypereosinophilia vomiting, lethargy, sleep and behaviour disorders, (Beaver et al., 1952). The typical VLM patient pharyngitis, pneumonia, coughing, wheezing, is a child between the ages of 2 and 7 years with limb pains, cervical adenitis and hepatomegaly. a history of geophagia and exposure to puppies Twenty-seven per cent of patients had high anti- in the home. The clinical signs of VLM are Toxocara antibody titres, but a normal eosinophil usually associated with hepatic and pulmonary count. This form of the disease in children was larval migration and include abdominal pain, de- coined ‘covert toxocariasis’ (Taylor et al., 1988). creased appetite, restlessness, fever, coughing, Toxocariasis has also been associated with wheezing, asthma and hepatomegaly (Ehrard allergy-related syndromes including angioedema and Kernbaum, 1979). Infection is usually char- (Magnaval and Baixench, 1993), chronic urticaria acterized by marked and chronic eosinophilia (Wolfrom et al., 1996), prurigo (Humbert et al., (>2.0 Â 109 cells/l), leukocytosis and hypergam- 2000) and reactive arthritis (Bethel, 1981). ßCAB International 2006. Toxocara: the Enigmatic Parasite (eds C.V. Holland and H.V. Smith) 113 114 J.-F. Magnaval and L.T. Glickman Ocular toxocariasis (see Chapter 9, this vol- 5 years (Rubinsky-Elefant, 2004). Seroprevalence ume) typically occurs unilaterally in children and surveys in Western countries found that 2–5% of young adults. The most common symptom is vis- apparently healthy adults from urban areas had a ual loss with onset over a period of days to weeks. positive anti-Toxocara antibody titre compared In some individuals these signs may wax and wane with 14.2–37% of adults in rural areas (Magnaval over a period of years, often related to migration et al., 1994a). In tropical countries, the seropreva- of larvae in the retina and granuloma formation. lence of toxocaral infection was much higher, Many ocular infections are subclinical and namely 63.2% in children and teenagers in Bali detected during a routine eye examination. Ocu- (Chomel et al., 1993), 86% in Saint Lucia, West lar toxocariasis apparently is an endemic disease Indies, among children (Thompson et al., 1986) in some areas of the USA (Maetz et al., 1987), and and 92.8% in adults in La Re´union Island (Mag- the prevalence was estimated at 6.6 cases per naval et al., 1994b). Since the presence of anti- 100,000 persons in Ireland (Good et al., 2004). Toxocara antibodies alone does not distinguish be- Toxocara larvae readily migrate to the brain of tween current and past infections, it should be experimentally infected laboratory animals (see accompanied by other laboratory tests for blood Chapter 5, this volume). However, a review of the eosinophil count and total serum IgE. literature in English from 1950 to the present, Chronic eosinophilia is generally considered a found only 29 cases of neurological toxocariasis in reliable indicator of active helminthiasis. However, humans (Moreira-Silva et al., 2004). Toxocara infec- the differential diagnosis of this sign is consistent tion of the central nervous system (CNS) elicits non- with (in decreasing frequency): common allergies, specific neurological signs such as seizures and hypersensitivity to drugs and chemicals (especially headache, thus leading to an underdiagnosis of b-lactam antibiotics and cholesterol-lowering this condition (Magnaval et al., 1997). agents), helminthiases, non-allergic conditions including neoplasia (e.g. hepatic and pulmonary carcinomas, Hodgkin’s disease), dermatologic dis- eases (e.g. bullous pemphigoid), digestive diseases Diagnostic Methods for Toxocariasis (e.g. Crohn’s and Whipple’s disease), vasculitis (e.g. Churg–Strauss syndrome, polyarteritis nodosa) A definitive diagnosis of toxocariasis is often a and hypereosinophilic syndrome (HES). significant challenge for the clinician, since the Following a history and clinical examin- clinical picture of this helminthiasis is quite non- ation, biological investigations should include non- specific (see Chapter 7, this volume). For example, specific tests for erythrocyte sedimentation rate and the symptoms can mimic those found with haem- C-reactive protein, and measurement of serum atological malignancies, infections with other hel- immunoglobulins IgG and IgE. Since the first mintic parasites and non-infectious conditions, report in 1968 ( Johansson et al., 1968) of elevated including allergies and asthma. At this stage in total serum IgE in Ethiopian preschool children the diagnostic process, a careful history regarding with ascariasis, elevated total serum IgE concen- occupational and household chemical exposures, trations have also been found in patients with drug exposures, asthma, eczema or rhinitis, travel anisakiasis, cystic echinococcosis, filariasis, schis- to tropical areas and country of origin, contact tosomiasis, strongyloidiasis and toxocariasis. The with domestic animals particularly puppies, con- finding of a substantial ($fourfold the upper nor- sumption of raw or undercooked meats, and pica, mal value) increase of serum IgE is therefore a specifically geophagia, should be obtained. valuable indication of helminth infection, espe- Human toxocariasis is most often a benign, cially when associated with blood eosinophilia. asymptomatic and self-limiting disease, as long as Non-allergic causes of eosinophilia, such as car- re-infection does not occur. Residual anti-Toxocara cinomas and vasculitis, are usually not associated antibodies have no pathological significance but with an elevated level of total IgE, except in one can persist for years. Anti-Toxocara antibodies form of HES (Roufosse et al., 2004). measured by ELISA were found to persist for up Repeated stool examinations, including the to 2.8 years in infected adults in Switzerland Baermann method for detection of Strongyloides ( Jeanneret, 1991), while anti-Toxocara antibodies stercoralis larvae, should be performed to rule out detected by Western blot (WB) can persist for over other parasitic infections. Negative stool exams in Management and Treatment Options for Human Toxocariasis 115 the presence of eosinophilia and an elevated disease, eosinophilia is uncommon or mild even serum IgE are indications for specific immuno- in patients with severe ocular manifestations diagnostic tests for parasites including anisakiasis, (Glickman and Schantz, 1981; Altcheh et al., ascariasis, strongyloidiasis, trichinellosis and toxo- 2003). Furthermore, serum anti-Toxocara anti- cariasis. Serological tests for cystic or alveolar bodies may not be detected either by ELISA echinococcosis may be indicated in endemic (Glickman et al., 1986) or by the more sensitive areas for this parasite, as are tests for tropical WB (Magnaval et al., 2002). Anti-Toxocara anti- helminthic diseases including filariases and schis- bodies when found in the aqueous or vitreous tosomiases for immigrants from endemic areas fluid of patients with clinical signs of ocular toxo- and persons with a travel history (Magnaval, cariasis, however, should be considered diagnostic 1998b). In patients presenting with severe hepato- for ocular toxocariasis. The anti-Toxocara antibody megaly, lymphadenopathy and/or splenomegaly, titre in these fluids has been found to be higher than a bone marrow examination after aspiration or that found in serum obtained from patients with biopsy is indicated for the diagnosis of possible ocular toxocariasis (Brasseur et al., 1984; Bertel- haematological malignancy. mann et al., 2003). Imaging techniques are Non-atopic patients who exhibit allergic signs, especially