Larva migrans syndrome caused by Emphasis Type="I

Authors: A Yoshida A Hombu Z Wang H Maruyama

Publish Date: 2016/06/06

Volume: 35, Issue: 9, Pages: 1521-1529

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Abstract

Larva migrans syndrome LMS caused by Toxocara and Ascaris roundworms is generally believed to be more common in children while a report from Japan suggests that it is more common in adults We conducted a largescale retrospective study to confirm these findings and to clarify what caused the difference between Japan and other countries to reveal overlooked aspects of this disease The clinical information of 911 cases which we diagnosed as Toxocara or Ascaris LMS during 2001 and 2015 was analysed Information used included age sex address city or county chief complaint present history dietary history overseas travelling history medical imaging findings and laboratory data white blood cell count peripheral blood eosinophil number and total IgE The sex ratio of the disease was 237 male/female = 641/270 The number of patients not younger than 20 years old were 978 and 951  among males and females respectively Major disease types were visceral ocular neural and asymptomatic The visceral type was more prevalent in older patients while younger patients were more vulnerable to ocular symptoms More than twothirds of the patients whose dietary habits were recorded had a history of ingesting raw or undercooked animal meat LMS caused by Toxocara or Ascaris is primarily a disease of adult males in Japan who probably acquired infections by eating raw or undercooked animal meat/liver Healthcare specialists should draw public attention to the risk of raw or undercooked animal meat in Europe as wellLarva migrans syndrome LMS is a typical zoonosis caused by parasitic worms which cannot mature in humans Although various kinds of parasites could cause LMS 1 2 3 4 5 the most popular and cosmopolitan species are Toxocara canis and T cati 6 7 which are native to dogs and cats respectively In addition to Toxocara spp LMS caused by Ascaris suum has also been reported 8 9 10 Toxocara canis T cati and A suum are all large intestinal roundworms belonging to the family Ascarididae so LMS caused by these parasites could be referred to as ascarid LMSHumans acquire infection with these ascarid nematodes by ingesting embryonated eggs contaminating the soil or vegetables or eating raw/undercooked paratenic host meat such as chicken and beef in which infective larvae reside After the ingestion of eggs or infected meat thirdstage larvae invade intestinal mucosa and migrate to various tissues and organs through blood or lymph vessels eliciting potent immune responses with eosinophilic inflammation Typical and classical target organs are the liver and lungs causing symptoms classically described as visceral larva migrans VLM Eyes ocular larva migrans OLM brain and spinal cord neural larva migrans NLM could also be affected 6 7 11A large body of literature on human toxocariasis infection with T canis or T cati is available from European and North American countries in which toxocariasis is considered to be more common in children 12 13 14 15 16 Because children often visit eggcontaminated areas and ingest dirt as a result of their play habits and hygiene they have a greater chance of contracting infections Geophagia and owning a dog or cat are believed to be other factors that increase the risk of infection 13 17 18 However a report from Japan dealing with a relatively small number of patients suggests that toxocariasis in Japan is more common in adults 19During 2001 and 2015 samples of 5532 patients which mainly consisted of sera were tested and 955 patients were diagnosed as having Toxocara or Ascaris infections During the study period we experienced only a single patient in which a parasite larva was directly demonstrated In this case a biopsy specimen was taken from the spinal cord of a 33yearold female patient who had suffered from paresthesia in the left shoulder Pathology revealed a T canis larva in histological sections All other cases were diagnosed based on the results of antibody tests without direct worm demonstrationHowever laboratory personnel who were responsible for the antibody test and diagnosis changed more than a couple of times during this period affecting assay procedures and decision protocol Therefore we reexamined the clinical history and serum antibodies of all 955 patients to select unambiguous cases for analysis As a result 911 patients were diagnosed as having Toxocara and/or Ascaris infection under the present criteria see below

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