Toxocarosis in humans: how much of a problem is it in the UK?

Abstract

Toxocara canis(from dogs) is recognised as a potential cause of human toxocarosis, butToxocara cati(from cats) and other species (eg,Toxascaris leoninafound in foxes) are also possible causes. Most colonisation withToxocaraspecies does not lead to symptomatic infection in well-cared for adult animals; young and debilitated animals are at greater risk. Humans can acquire infection from infected animals, for example, via soil contaminated with faeces; however, most human infections are asymptomatic, with symptomatic infection being very rare in the UK. The risk of human infection is reduced by measures such as hand washing and responsible disposal of dog faeces. Some organisations recommend regular prophylactic treatment of pet dogs and cats. However, there are concerns that some parasiticides are contaminating the environment. As an example of a One-Health problem there is a potential conflict between the needs of animal health, human health and the health of the wider ecosystem. Also, considering that only about 5% of non-juvenile household dogs shedToxocaraeggs at a given time, it has been questioned whether it is worthwhile to invest in frequent blind treatments. British veterinary organisations have suggested less frequent treatment may be more appropriate and should be based on individual risk assessment and faecal examinations for worms rather than blanket regular prophylactic treatment, which could reduce the impact of parasiticides on the environment without greatly increasing the risks to animal or human health.

Zoonotic Parasites in Playgrounds in Southern Spain: A One Health Approach

“…eggs to survive for years in the environment facilitates their transmission [ 20 , 22 ]. Humans become accidental hosts when they ingest dirt contaminated with faeces from animals carrying Toxocara infective eggs, such as in playgrounds [ 26 ]. However, transmission to humans can also occur through direct contact with pets due to the presence of Toxocara infective eggs in pet hair [ 26 ].…”

“…Humans become accidental hosts when they ingest dirt contaminated with faeces from animals carrying Toxocara infective eggs, such as in playgrounds [ 26 ]. However, transmission to humans can also occur through direct contact with pets due to the presence of Toxocara infective eggs in pet hair [ 26 ]. Although the number of infective eggs in pet hair is very low, it is lowest in well-cared-for, owned adult dogs and highest in puppies and strays [ 26 ].…”

“…However, transmission to humans can also occur through direct contact with pets due to the presence of Toxocara infective eggs in pet hair [ 26 ]. Although the number of infective eggs in pet hair is very low, it is lowest in well-cared-for, owned adult dogs and highest in puppies and strays [ 26 ]. It is important to note that only embryonated eggs are infective, so the environment is an important source of infection [ 26 ].…”

“…Although the number of infective eggs in pet hair is very low, it is lowest in well-cared-for, owned adult dogs and highest in puppies and strays [ 26 ]. It is important to note that only embryonated eggs are infective, so the environment is an important source of infection [ 26 ]. The first human infection was reported in 1950, and it is currently considered that 19.0% of the population have antibodies [ 27 , 28 ].…”

Toxocara and environmental damage

“…The NHS website defines toxocariasis as ‘rare, but can sometimes cause serious problems’; 2 the condition is probably under diagnosed, but in the UK only 106 cases of serious disease were recorded in the 45 years to 2017 3 …”