STRONGYLOIDIASIS (Strongyloides stercoralis) • The genus Strongyloides contains over fifty species of gastrointestinal parasites capable of infesting a range of animal hosts including dogs and cats, with two species known to infect humans. 1-3 • Strongyloides stercoralis, the major causative agent of strongyloidiasis, is an intestinal threadlike nematode that is endemic to the northern two-thirds of Australia. 3 Globally it is estimated more than 600 million people are infected with S. stercoralis . 4 • Although S. stercoralis is primarily a parasite of humans, dogs may be infested and be a source of zoonotic infection.
ACAZAP RECOMMENDATIONS
• In S. stercoralis endemic regions it is essential to minimise exposure by:
impervious surfaces with disinfection is likely to decrease the parasitic burden in shelters. Animals with diarrhoea should be isolated. • In at-risk human and canine patient groups, it is recommended individuals are screened for Strongyloides infection prior to starting immunosuppressive medication (such as corticosteroids or chemotherapy) or in those with haematological malignancy. • Owners of dogs diagnosed with S. stercoralis , particularly pet owners on immunosuppressive medication, should be screened for Strongyloides infection and seek advice from a human healthcare professional.
- Wearing gloves if handling potentially contaminated soil. - Wearing shoes in areas known or likely to be contaminated. - Practicing good hand hygiene. • Prompt removal of faeces is important to avoid contamination of the soil. • Infection in animal shelters represents a zoonotic risk for staff and visitors. Thorough cleaning involving regular removal of faeces and mechanical cleaning of cages, floors and
IN ANIMALS
AETIOLOGY AND EPIDEMIOLOGY • Strongyloides stercoralis is primarily considered a parasite of humans, however natural patent infestations may occur in non-human primates and canids (domestic and wild). 1 Cats may be infested experimentally with S. stercoralis but it is not known to be a normal feline parasite. 1,2 • Dogs carry genetically distinct haplotypic clades of S. stercoralis , one shared with humans, the other exclusively found in dogs, suggesting that dogs are a possible reservoir for zoonotic Strongyloides infection. 5 • Strongyloides spp. have complex and unique developmental phases with two distinct life cycles; a free-living (heterogenic) cycle and a parasitic cycle completed within the host. Only the female worms are parasitic, reproducing asexually in the small intestine. • Larvae passed in faeces undergo rapid development to moult
to either filariform larvae or free-living adults. After mating, non-parasitic females reproduce in the environment to generate second-generation infective filariform (L3) larvae. Second generation filariform larvae more commonly penetrate the skin of a new host, however they may also infest the host via ingestion. 6 Transmammary transmission can also occur. The prepatent period following percutaneous penetration of S. stercoralis is 5-21 days. 1 • Strongyloides stercoralis can complete its life cycle without leaving the host, leading to chronic, life-long infections if left untreated. Larvae undergo hepato-pulmonary and tracheal migration to develop into adults in the intestines and produce larvae that re-infect the host percutaneously via the skin or colonic mucosa (a process known as autoinfection). This can occur in neonatal and immunocompromised dogs, and lead to hyperinfection (excessive parasitic burden in the gastrointestinal tract and lungs) and more seriously, disseminated infection
CONTENTS
79 Companion Animal Zoonoses Guidelines
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