Strongyloides stercoralis infection in dogs in Austria: two case reports

Abstract

Background Strongyloides stercoralis is endemic in tropical and subtropical regions, but reports of infections in central and northern Europe have been recently increasing. Infections occur mainly in humans and dogs. In dogs, both dog-adapted and zoonotic S. stercoralis genotypes seem to occur. Clinical manifestations mainly include gastrointestinal and respiratory signs. The severity of the disease can vary greatly and depends on the immune status of the host. The infection is potentially fatal in immunosuppressed individuals, either medically induced or due to an underlying disease, in which hyperinfections and disseminated infections with extraintestinal parasite dissemination may occur. Methods Diagnosis was based on coproscopy, including flotation and the Baermann funnel technique, histology of small intestinal biopsies and molecular analysis of mitochondrial cytochrome oxidase subunit I (COI) and hypervariable regions I and IV (HVR I and HVR IV) of the nuclear 18S rDNA loci. Results Two independent cases of severe canine S.stercoralis infection in Austria are presented. In both cases, S. stercoralis was detected in histological sections of the small intestine and with the Baermann funnel technique. Molecular analysis revealed strains with zoonotic potential. Case 1 was a 1-year-old female French bulldog with a long history of respiratory and gastrointestinal signs, severe emaciation and apathy before S.stercoralis infection was diagnosed. Treatment with moxidectin (2.5 mg/kg body weight [BW], oral route) did not eliminate the infection, but treatment with ivermectin (0.2 mg/kg BW, subcutaneously) was successful. Case 2 consisted of two 2-month-old Pomeranian puppies, one female and one male, from a litter of four, which died soon after presenting dyspnoea and haemorrhagic diarrhoea (female) or torticollis (male); S.stercoralis infection was first diagnosed post-mortem. Conclusion More attention should be paid to this nematode because although it appears to be rare in Austria, it is easily overlooked on standard coproscopy unless a Baermann funnel technique is used, and even then, it can be missed. Moxidectin is not always successful in eliminating the infection, and treatment with ivermectin should be considered in cases of infection. Graphical Abstract

Identification and treatment of Strongyloides stercoralis infection in a Boston Terrier dog from south‐eastern Australia

“…Infection with S. stercoralis in dogs may be asymptomatic or could manifest with a spectrum of gastrointestinal and respiratory signs 1 . The dog in the present case demonstrated severe gastrointestinal signs and systemic shock but did not exhibit severe respiratory compromise, highlighting the variation in clinical presentation 15–17 . Severe forms are typically encountered in immunosuppressed animals or in young dogs with no known factors of immunodeficiency 2 .…”

“…It is unlikely that 12 doses were necessary for eradication given previous reports of single subcutaneous injections at the same dose being efficacious. 15,17 Reports of ivermectin at an oral dosing regimen of 0.2 mg/kg for two consecutive days or 0.5 mg/kg for 7 days was found to be similarly efficacious for clearance of larvae in faeces. 8,16 In this case, clinical improvement did not occur immediately, likely owing to hyperinfection and the immunocompromised nature of the patient.…”

“…1 The dog in the present case demonstrated severe gastrointestinal signs and systemic shock but did not exhibit severe respiratory compromise, highlighting the variation in clinical presentation. [15][16][17] Severe forms are typically encountered in immunosuppressed animals or in young dogs with no known factors of immunodeficiency. 2 While glucocorticoids are known to suppress the immune system and lead to disseminated strongyloidiasis in dogs, 3,18 the presenting dog received only a single anti-inflammatory dose of glucocorticoid injection 1 week prior to diagnosis.…”

“…21 This is reflected in veterinary case reports which have shown that improvement of clinical signs and larval disappearance can vary following subcutaneous ivermectin administration. 3,8,[15][16][17]22 Therefore, repeated fortnightly administration aimed to continually eliminate adults in the gastrointestinal tract as they developed from auto-infective and/or environmentally sourced larvae, given the prepatent period of 6-10 days. The successful eradication of parasitism provides evidence of ivermectin's efficacy, although further evidence from controlled clinical trials is necessary.…”

“…Ivermectin at 200 μg/kg has proven 100% effective in removing adult S. stercoralis from the intestinal tract of experimentally infected dogs, but not effective in removing third‐stage larvae from parenteral sites 21 . This is reflected in veterinary case reports which have shown that improvement of clinical signs and larval disappearance can vary following subcutaneous ivermectin administration 3,8,15–17,22 . Therefore, repeated fortnightly administration aimed to continually eliminate adults in the gastrointestinal tract as they developed from auto‐infective and/or environmentally sourced larvae, given the prepatent period of 6–10 days.…”