Faecal-oral parasite transmission and the veterinary nurse's role in education

Cats and dogs carry a wide range of parasites endemic in the UK with pathological and zoonotic potential. Many of these are intestinal dwelling and pass infective life stages in the faeces which may then directly infect other hosts. This mode of transmission is known as the faecal-oral route and preventing exposure is key to breaking the life cycle of these parasites and improving the health of both pets, owners and the wider public as a result. Veterinary nurses (VNs) have a vital role to play in educating pet owners in the part they must play in achieving this. Parasites transmitted by the faecal-oral route are numerous, but the ones presenting the greatest risk in the UK fall into three groups: Toxocara roundworms, intestinal protozoa and tapeworms.

Toxocara spp. are a group of intestinal nematodes with species infecting dogs (Toxocara canis) and cats (Toxocara cati), both of which have zoonotic potential. Adult worms lie in the small intestine and shed eggs into the environment via the faeces of the host. The eggs when first shed are un-embryonated and not infective. Progression to the infective embryonated L3 stage is required for infection, so fresh faeces do not present a zoonotic risk with embryonation taking place in 2 to 7 weeks under optimum conditions. Although dogs may be infected by ingesting embryonated eggs, the most important route of canine infection is trans-placental. Dogs and cats may also become infected by trans-mammary infection or consuming paratenic hosts such as rodents. The most common route of human infection however, is by the ingestion of embryonated eggs. Oral ingestion of embryonated eggs can lead to a variety of disease syndromes in people including visceral and ocular larval migrans. Seropositivity in humans to Toxocara spp. has been demonstrated to be a risk factor for chronic disease such as epilepsy and cognitive dysfunction. When first passed, Toxocara spp. ova are not infective to humans for several weeks and immediate infection by the faecal-oral route cannot occur. The uncontrolled passing of ova by cats and dogs, especially puppies and kittens, however, will lead to significant build-up of ova in the environment with the potential for zoonotic infection in the longer term. Methods used to control faecal-oral transmission are therefore relevant to human toxocarosis prevention. These measures include: