IN ANIMALS continued
(widespread larval migration outside of the gastrointestinal tract and lungs, e.g. to liver, brain, heart, and urinary tract). 6 Hyperinfection can occur in any host, whilst disseminated disease predominantly occurs in immunocompromised populations, often leading to an accompanying fatal septicaemia. 7,8 PREVALENCE AND RISK FACTORS • Infestation is more frequent in warm and humid areas, although infestation can occur in temperate climates. Poor sanitation and damp areas such as heavily soiled cages are highly favourable for harbouring S. stercoralis larvae and the parasite may become a chronic problem in kennel environments. 9,10 • Young animals are more susceptible to S. stercoralis infestation, particularly puppies. 9 • In a 2020 Australian study, the prevalence of Strongyloides spp. in environmental canine faecal samples (collected from communities across the Northern Territory, central Australia, northern areas of Western Australia and the north-west of South Australia) was 21.9%. 11 CLINICAL DISEASE • In immunocompetent animals, the infestation is mostly asymptomatic. Immunity develops within the first 8-12 weeks of life resulting in a cessation of larval shedding. 12
• Strongyloides stercoralis lives in the mucosa of the small intestine in dogs. With high worm burdens, severe enteritis accompanied by abdominal pain, diarrhoea, anaemia and signs of wasting can occur. Migrating larvae may result in damage to the lungs and other tissues with respiratory signs such as pneumonia. 6,12 Percutaneous penetration of larvae may cause pododermatitis. 13
DIAGNOSIS • Prevalence is likely underestimated as standard faecal flotations have low sensitivity for the
detection of S. stercoralis . Generally, faecal examination for Strongyloides spp. can be difficult. 14 The Baermann method is recommended for the isolation and identification of Strongyloides larvae in fresh faeces. 13 • For refrigerated, frozen or ethanol-fixed faecal samples, PCR is the test of choice, where available. • In areas endemic for strongyloidiasis, it is advised that dogs be screened for S. stercoralis prior to commencement of corticosteroids or immunosuppressive drugs. • No products are registered in Australia for the treatment of Strongyloides spp. in dogs and cats. Ivermectin at 200 µg/kg once daily for 2 days has been reported to be effective in the treatment of S. stercoralis in dogs. 15
Life cycle of Strongyloides stercoralis
Life cycle of Strongyloides stercoralis
Parasitic generation
D.H. Dog, cat and human
The larvae pass into the bloodstream and migrate to the lungs, alveoli and trachea. Finally they are swallowed and only female adults develop in the small intestine
Infective filariform larva
Larvae infest puppies via milk
Infective filariform larva
The rhabditiform larva becomes an infective filariform larva
LACTOGENIC TRANSMISSION
INDIRECT CYCLE
Adult (female only)
INTERNAL AUTOINFECTION
Rhabditiform larva
The larvae go through the intestinal wall again or penetrate the perianal skin
New free-living generation: the larvae develop into adults
Female adults produce embryonated eggs
DIRECT CYCLE
Egg
Embryonated egg
Free-living generation
Faeces
Rhabditiform larva
Adults develop, mate and lay eggs
Rhabditiform larva
D.H. = definitive host
Extracted from the Textbook of Clinical Parasitology in dogs and cats, Beugnet F., Halos L., Guillot J., Ed Servet, 2018. Life cycles adapted from Pet Owner Educational Atlas. Parasites, Carithers D. and Miro G., Ed Servet, 2012. Life cycle from Beugnet, F., et al (2018) Textbook of Clinical Parasitology in Dogs and Cat. Grupo Asis Biomedica, S.L.; Adapted from Carithers, D., et al (2012) Pet Owner Educational Atlas.
CONTENTS
Companion Animal Zoonoses Guidelines 80
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