Human toxocariasis and direct contact with dogs

Toxocariasis in man is traditionally thought to be contracted through the ingestion of eggs from contaminated soil. The disease may manifest itself in different syndromes such as ocular larval migrans, visceral larval migrans and covert toxocariasis. This paper assesses the evidence for the soil contamination hypothesis and proposes that direct contact with dogs may provide a better explanation of the epidemiology of the disease. Hair was collected from 60 dogs from various places in Ireland and the UK and examined for the presence of Toxocara canis eggs. T. canis eggs were found in the hair of 25 per cent of the dogs; in total, 71 eggs were recovered, of which 4.2 per cent were embryonated and 23.9 per cent were embryonating. The maximum densities of the embryonating and embryonated eggs were 180 and 20 eggs per gram of hair, respectively, much higher than the densities reported for soil samples. It is suggested that dogs infected with T. canis may infect people by direct contact.