Lessons from eight cases of adult pulmonary toxocariasis: Abridged republication

Human toxocariasis is a zoonosis caused by infective larvae of Toxocara canis or T. cati, with infection resulting from the ingestion of embryonated eggs or live larvae. Excreted eggs from Toxocara species may contaminate soil or adhere to the hairs of pets, and the liver is one of the most intensely affected organs in infected ‘paratenic’ hosts. The term ‘paratenic hosts’ denotes host animals in which the infective-stage larvae are harboured without essential development, and include beef cattle, fowls and swine. We encountered eight adult cases of pulmonary toxocariasis, as shown in Table 1, including one case (Case 8) of pneumothorax with eosinophilic pleural effusion. In the other seven patients chest CT findings showed multiple small pulmonary lesions, most of which were either nodules with a halo or ground-glass opacities, located in subpleural areas. In some cases, disappearance of the original lesions followed by re-appearance of new lesions was observed. Of the present eight patients, five were asymptomatic. It is noteworthy that infection may not cause symptoms, despite the presence of abnormalities on chest imaging and a peripheral blood eosinophilia. Abnormal laboratory findings included eosinophilia (>0.5 ¥ 10/L) in six cases and an elevated IgE (>100 IU/mL) in all patients. Infection was associated with consumption of raw liver from paratenic hosts in five patients. In Japan, raw bovine or chicken livers are often available on the menu at yakitori (grilled chicken) and yakiniku (grilled meat) restaurants. Food-borne transmission should therefore be suspected in adult Japanese patients with toxocariasis. Dot-ELISA examinations using a non-purified antigen prepared from adult worms gave positive results for both Ascaris suum and T. canis in seven patients, while sera from all patients showed positive results for the larval excretory-secretory (LES) product of T. canis (TcES). In addition, agar gel immunodiffusion tests detected a precipitin band against TcES, but not LES of A. suum. Serodiagnosis for toxocariasis should be performed with TcES. The larvae do not survive indefinitely in humans. However, accidental migration to the eyes or central nervous system can cause serious complications. Therefore, patients with toxocariasis, including those who are asymptomatic, should be considered for anthelmintic treatment. We initiated a regimen of albendazole (ABZ), 10–15 mg/kg of bodyweight, in divided doses twice daily for 14 days, as suggested by Magnaval and Glickman, with additional successive or intermittent courses for a maximum of 28 consecutive days, until clear improvement was observed. This included disappearance of pulmonary lesions on CT and normalization of blood eosinophil counts. Three months after completion of the ABZ treatments, decreased titres of anti-TcES antibody were confirmed in five patients (Cases 1–5) and an associated precipitin band was barely detectable in Case 6. The total period of ABZ treatment given was 4 weeks or longer. Although there is no agreement about the optimum duration of administration, our experience suggests a treatment period with ABZ of 4 weeks minimum, together with careful observation because of the possibility of adverse reactions, including liver dysfunction.