Visceral larva migrans.

AK Sarda, R Kannan, DK Sharma, V Mahajan, A Goel, K Uma 
 Dept of Surgery, Maulana Azad Medical College, New Delhi.

Correspondence Address:
A K Sarda
Dept of Surgery, Maulana Azad Medical College, New Delhi.

Full Text

::   Introduction

Since the original description by Beaver et al[1] in 1952, the syndrome of visceral larva migrans has been reported from all over the world. However, although 80% of the dogs in India are affected by Toxocara canis, to our knowledge there are no reports of visceral larva migrans in humans from India. The reasons for this are not clear. Difficulties in defining the parasites in the tissues and the non-availability and/or under-utilization of the available diagnostic methods, combined with a low index of suspicion, are probably important underlying factors, especially since the ova, larva an the adult forms of the parasite are not passed in the stools. Besides, symptomatology of visceral larva migrans is similar to the more common and more easily definable tropical parasitic and nonparasitic diseases so that the milder symptoms of visceral larva migrans are probably ignored by the physicians and the patients alike.

We present a case in whom quite by serendipity, we made a histologic diagnosis of visceral larva migrans. To our knowledge this is the first case of this disorder reported from India.

::   Case report

A 45-year-old woman, who was a vegetarian and who had never travelled outside Delhi, presented with repeated attacks of colicky pain in the right hypochondrium, which on ultrasonography was diagnosed to be due to chronic cholecystitis with cholelithiasis. The patient did not give history of any significant illness in the past. A laparotomy was performed for cholecystectomy. However, on exploration the liver was found to be studded with multiple hard greyish white nodules. The gall bladder was contracted and fibrotic. The rest of the viscera and peritoneal cavity were essentially normal. A cholecystecthmy was performed easily and a biopsy of one of the nodules from the liver was performed. The provisional diagnosis at the time of surgery was liver secondaries possibly from a carcinoma of the gall bladder since this is not an uncommon disease in this part of the country. The patient made an uneventful post-operative recovery. Histopathological examination of the gall bladder revealed chronic cholecystitis while the liver nodule was reported as granulomas and microabscesses with parasitic remnants suggestive of visceral larva migrans [Figure:1] and [Figure:2]. CAT scanning of the abdomen revealed midtiple areas suggestive of small abscesses. Since serological tests for Toxocara were not available, none were carried out.

::   Discussion

We report this case to emphasize the fact that in areas where visceral larva migrans is not reported and nodules in the liver are most frequently due to secondaries, the surgeon should always resort to a biopsy of the nodule to rule out uncommon presentations of benign disorders. It is most likely that in the present case from an area where visceral larva migrans has not been reported, without a biopsy, the patient would surely have been condemned as a terminal malignancy.

Visceral larva migrans occurs when larvae of certain parasites enter the portal circulation by burrowing through the gut wall and get trapped in the liver where they incite a granulomatous reaction and microabscess formation. Sometimes they escape the hepatic filter and lodge in the brain, kidney, lungs viscera, and even skin. The commonest parasite implicated is Toxocara canis or the dog roundworm.

Dogs, wolves, foxes and other canines play host to Toxocara canis. Puppies and lactating bitches may shed more than two lakhs ova per day; in contrast, adult dogs excrete few eggs. Following ingestion of fertilised eggs by humans, the larvae hatch and migrate via lymphatics and portal circulation to the various tissues - liver, lungs and, occasionally, the heart, the central nervous system, the eye or any other tissue[2],[3]. The larvae elicit an eosinophilic reaction to form microabscesses and granulomas and never complete their natural life cycle so that adult worms or ova are never shed in the feces.

The clinical and pathological manifestations are due to the mechanical damage caused by migrating larvae and the inflammatory response of multiple eosinophilic abscesses and allergic eosinophilic granulomas stimulated by the larvae[2]. At one end of the spectrum the patients may be asymptomatic being accidentally diagnosed on biopsy or autopsy for entirely different reasons. Other patients may be placed under a variety of diagnostic labels ranging from food or drug allergies and familial eosinophilia to postinfection eosinophilia and eosinophilic leukaemia[4]. At the other extreme the infestation may be a fulminant and, sometimes a fatal disorder secondary to pulmonary or central nervous system involvement[4].

The majority of diagnosed cases are young children with pica. There may be marked hypereosinophilia with pulmonary signs, cardiac dysfunction, nephrosis or neurological lesions. Depending on the degree of involvement the patients may exhibit fever, cough, wheezing, behaviour problems, convulsions, paresis, transverse myelitis and ocular abnormalitiess. Though a history of pica may be difficult to elicit, presence of foreign objects like plaster in the gastrointerstinal tract may be an evidence of pica.

The commonest haematological abnormality is mild to marked eosinophilia with significant hyperglobulinaemia ranging from 4-7 gm/dl with most of the circulating globulin being IgG though in some patients IgM or IgE may be raised several times the normal levels[6]. Non-specific antibodies like the Forssman antibody may be present[7]. There may be a marked increase in the titre of anti - A and anti-B isohaemagglutinins[6]-[8]. A specific antigen obtained from the secretory products of the second stage Toxocara canis larvae, which is both sensitive and specific, has been used in an enzyme - linked - immunosorbant assay (ELISA) and is the screening procedure of choice. A radioallergenosorbant test (RAS-0 has been used to detect larva-specific IgE[9]. However, the skin tests developed earlier have now been abandoned.

However, since the ova of Toxocara canis are never present in the stools, a definitive diagnosis can only be made by identifying larvae in the affected tissues. It is often difficult to define an intact larva in the eosinophilic granulomas especially if the larva is degenerated.

Although a variety of drugs have recently been introduced for the treatment of visceral larva migrans, only diethylcarbamazine: 3 mg/kg body weight orally three times a day for 21 days[10], and thiabendazole: 50 mg/kg body weight daily for 1-4 weeks[11],[12] are currently in clinical usage. However, the therapeutic efficacy of these compounds in destroying the parasites is not conclusively established. Corlicosteroids have a well-established role in the treatment of pulmonary disease, being extremely effective in alleviating the respiratory symptoms within a short time of starting therapy.

Corticosteroids may also be used concurrently with thiabendazole therapy to decrease the risk of accentuation of the inflammatory response resultant upon the death of the parasites.

However, the major emphasis in the management of visceral larva migrans should be on the prevention of infection by curbing geographia and, possibly, by limiting the contact between children and animals, especially nursing bitches and newborn puppies, and, of course, regular deworming of all cats and dogs.

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