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

Strongyloides stercoralis, the causative agent of strongyloidiasis, is a potentially zoonotic intestinal nematode endemic to northern Australia. Strongyloidiasis is typically observed in immunocompromised hosts and is characterised by gastrointestinal signs, respiratory symptoms and a failure to thrive. In immunocompromised hosts, hyperinfection syndrome and disseminated infections can prove life-threatening. A 24-month-old Boston Terrier dog was referred for investigation of chronic small and large intestinal watery hematochezic diarrhoea, emaciation and hematemesis. Small intestinal histology identified a nematode despite consecutive negative faecal flotations. A real-time polymerase chain reaction and Baermann test subsequently confirmed infection with S. stercoralis. The dog had received an oral parasiticide comprising milbemycin oxime and afoxolaner every month for the 11 months prior to this diagnosis. Despite fenbendazole being reported as successful in the treatment of canine strongyloidiasis, a course of fenbendazole failed to clear the infection. Eradication of S. stercoralis infection was confirmed after the administration of off-label ivermectin fortnightly for 12 doses. Attention should be paid to this nematode as the failure of routine copromicroscopic methods to diagnose S. stercoralis infections can result in misdiagnosis, mistreatment and progression of the disease. Off-label ivermectin may be an alternative to fenbendazole for the treatment of Strongyloides spp. infection in dogs.

First identification of Strongyloides stercoralis infection in a pet dog in Argentina, using integrated diagnostic approaches

BACKGROUND

Strongyloides stercoralis is a soil-transmitted intestinal nematode with a complex life cycle that primarily affects humans, non-human primates, dogs, and occasionally cats. This study presents, to the best of our knowledge, the first case of S. stercoralis infection and its genotyping in a domestic dog from Argentina.

METHODS

The patient was a female wired-haired Teckel dog exhibiting recurrent coughing. Coproparasitological analysis using the Baermann technique revealed the presence of rhabditiform larvae morphologically compatible with S. stercoralis. To confirm this finding, molecular diagnosis (18S ribosomal RNA) and analysis of the cox1 gene were performed.

RESULTS

We identified a haplotype (HP20) that has previously only been related to S. stercoralis infection in dogs, but was found in the present study to be highly related to the haplotype (HP16) of a zoonotic variant and divergent from those previously described from human patients in Argentina. Furthermore, unlike in human cases following treatment with ivermectin, the dog was negative after moxidectin treatment according to polymerase chain reaction of the sampled faeces.

CONCLUSIONS

This case report shows the importance of further investigation into potential transmission events and prevalences of S. stercoralis in dogs and humans in South America. The results reported here should also encourage future work that examines different scenarios of infection with S. stercoralis in dogs and humans with the aim of integrating clinical management, diagnosis, treatment and follow-up strategies in the quest for new approaches for the treatment of this disease in animals and humans. The findings support the adoption of a One Health approach, which recognizes the interconnectedness between animal and human health, in addressing parasitic infections such as strongyloidiasis.

The prevalence of potentially zoonotic intestinal parasites in dogs and cats in Moscow, Russia

This study was aimed to determine the prevalence of Toxocara canis/cati, Strongyloides stercoralis, Giardia spp., and Cryptosporidium spp., which occur and are potentially zoonotic to humans in domestic dogs and cats in Moscow (Russia). The fecal flotation method and larvae detection by microscopy of a direct feces smear were performed to detect Toxocara, Giardia spp., and Cryptosporidium spp. The total parasitic prevalence in dogs was as follows: Giardia spp.: 10.2 % (226/2208), Cryptosporidium spp.: 2.7 % (60/2208), T. canis: 2 % (45/2208), S. stercoralis larvae: 1.1 % (25/2208). The younger animals under were infected more than those over 12 months of age (p<0.001). The preva lence rates were along these lines: Giardia spp. (18.2 %), Cryptosporidium spp. (5.7 %), T.canis (3 %), S. stercoralis larvae (2.3 %). The overall prevalence in cats was as follows: Giardia spp. - 5.2 % (71/1350), Cryptosporidium spp. - 4.8 % (65/1350), T. cati - 4.1 % (56/1350). Similarly to dogs, the infection rates were higher in cats under 12 months of age Giardia spp. (8.2 %), Cryptosporidium spp. (8.6 %), T. cati (7.5 %. Analysis of combined infections in dogs revealed the following combinations: Giardia spp. and Cryptosporidium spp. (35.5 %) larvae of S. stercoralis sp. and Giardia spp. (32.3 %), T.canis and Giardia spp. (22.6 %), T.canis and Cryptosporidium spp. (6.6 %), T.canis and S.stercoralis and (3.2 %), respectively. In cats, only two coinfections by Giardia spp. and Cryptosporidium spp. (58.3 %), and T.cati with Giardia spp. (41.7 %) were noticed. Further research is needed to study the spread of parasitic diseases in pet animals. The data will improve countermeasures to prevent these diseases' spread among animals and humans.

Global prevalence and epidemiology of Strongyloides stercoralis in dogs: a systematic review and meta-analysis

BACKGROUND

Strongyloides stercoralis, a soil-transmitted helminth, occurs in humans, non-human primates, dogs, cats and wild canids. The zoonotic potential between these hosts is not well understood with data available on prevalence primarily focused on humans. To increase knowledge on prevalence, this review and meta-analysis was performed to estimate the global status of S. stercoralis infections in dogs.

METHODS

Following the PRISMA guidelines, online literature published prior to November 2020 was obtained from multiple databases (Science Direct, Web of Science, PubMed, Scopus and Google Scholar). Prevalence was calculated on a global and country level, by country income and climate, and in stray/animal shelter dogs versus owned dogs. Statistical analyses were conducted using R-software (version 3.6.1).

RESULTS

From 9428 articles, 61 met the inclusion criteria. The estimated pooled global prevalence of S. stercoralis in dogs was 6% (95% CI 3-9%). Infection was found to be the most prevalent in low-income countries with pooled prevalence of 22% (95% CI 10-36%). The highest pooled prevalence of S. stercoralis in dogs was related to regions with average temperature of 10-20 °C (6%; 95% CI 3-11%), an annual rainfall of 1001-1500 mm (9%; 95% CI 4-15%) and humidity of 40-75% (8%; 95% CI 4-13%). Prevalence was higher in stray and shelter dogs (11%; 95% CI 1-26%) than in owned dogs (3%; 95% CI 1-7%).

CONCLUSIONS

As with S. stercoralis in humans, higher prevalence in dogs is found in subtropical and tropical regions and lower-income countries, locations which also can have high dog populations. While this study presents the first estimated global prevalence of S. stercoralis in dogs, it is potentially an underestimation with 15 of 61 studies relying on diagnostic methods of lower sensitivity and a paucity of data from most locations. Standardized protocols (e.g. quantity of feces and number of samples for a Baermann) in future studies could improve reliability of results. More prevalence studies and raising veterinary awareness of S. stercoralis are needed for a One Health approach to protect humans and dogs from the impact of the infection.

Prevalence of Intestinal Helminth Infections of Stray Dogs of Public Health Significance in Lagos Metropolis, Nigeria

Globally, stray dogs have been a major source of zoonoses such as cutaneous larval migrans, visceral larval migrans and hydatidosis. These dogs are recognized as being a major public health problem where their population is unchecked. This study was conducted to determine the prevalence of intestinal helminth parasites of stray dogs in Lagos metropolis. Stools of 96 stray dogs were examined microscopically for ova of these parasites using centrifugation flotation method. Four species of intestinal helminths were identified. The overall prevalence of helminths infection was 61.4%, with Ancylostoma caninum having a prevalence of 62.5%, Toxocara canis 20.8%, Dipylidium caninum 18.7% and Strongyloides stercoralis 2.0%. T. canis had the highest worm burden of 1,250 egg per gram (EPG) while S. stercoralis had the least (100 EPG). The areas with the most helminth infections were Yaba (n=12, X̄=1.58, SD=0.793), Agege (n=11, X̄=1.73, SD=0.786) and Ikotun (n=11, X̄=1.45, SD=0.820). S. stercoralis was only found in samples obtained from Mushin and Ikorodu. Most of the stool samples obtained from this study had mixed infections, 83.3% were infected with three helminth species, 8.3% were infected with four helminth species and none had double infection. Mushin had the most mixed infections (n=4, X̄=1.900, SD=1.101) while Obalende had the least (n=1, X̄=1.000, SD=0.000). Most of the intestinal helminth parasites identified in this study are zoonotic and thus pose a public health problem. Environmental factors seem to influence the health condition of these dogs, thus concerted efforts should be made to reduce the growing population of stray dogs on the street of Lagos.

Advances in the Molecular and Cellular Biology of Strongyloides spp

Purpose of Review

This paper constitutes an update of recent studies on the general biology, molecular genetics, and cellular biology of Strongyloides spp. and related parasitic nematodes.

Recent Findings

Increasingly, human strongyloidiasis is considered the most neglected of neglected tropical diseases. Despite this, the last 5 years has seen remarkable advances in the molecular biology of Strongyloides spp. Genome sequences for S. stercoralis, S. ratti, S. venezuelensis, S. papillosus, and the related parasite Parastrongyloides trichosuri were created, annotated, and analyzed. These genomic resources, along with a practical transgenesis platform for Strongyloides spp., aided a major achievement, the advent of targeted mutagenesis via CRISPR/Cas9 in S. stercoralis and S. ratti. The genome sequences have also enabled significant molecular epidemiologic and phylogenetic findings on human strongyloidiasis, including the first genetic evidence of zoonotic transmission of S. stercoralis between dogs and humans. Studies of molecular signaling pathways identified the nuclear receptor Ss-DAF-12 as one that can be manipulated in the parasite by exogenous application of its steroid ligands. The chemotherapeutic implications of this were unscored by a study in which a Ss-DAF-12 ligand suppressed autoinfection by S. stercoralis in a new murine model of human strongyloidiasis.

Summary

Seminal advances in genomics of Strongyloides spp. have transformed research into strongyloidiasis, facilitating fundamental phylogenetic and epidemiologic studies and aiding the deployment of CRISPR/Cas9 gene disruption and editing as functional genomic tools in Strongyloides spp. Studies of Ss-DAF-12 signaling in S. stercoralis demonstrated the potential of this pathway as a novel chemotherapeutic target in parasitic nematodes.

Intestinal Parasites of Pets and Other House-kept Animals in Moscow

A study screening pet animals (dogs, cats, chinchillas, ferrets, guinea pigs, rabbits, primates, reptiles, and hedgehogs) within Moscow city limits for intestinal parasitic diseases has been conducted over a period of 6 years. According to the study, parasitic infections caused by intestinal protozoa are found in pet animals more frequently than by intestinal helminths. Although dogs and cats exhibit the highest level of diversity of intestinal parasite species, in the group of exotic animals, helminth infection are found much less frequently and parasitic fauna is represented mostly by intestinal protozoa with a high percentage of mixed infection. The most widespread helminth infeсtion of dogs and cats is toxocarosis (respectively 2.5 and 5.7 %) and the most widespread protozoan infection is Giardia sp. (9.8 and 4.6 %). Giardia sp. was found in 47.4 % of chinchillas, Cryptosporidium sp. was more frequently found in ferrets (6.55 %), protozoa from the family Trichomonadida was found in guinea pigs (9 %), Eimeria sp. in rabbits (13.9 %), Acanthocephala in primates (15.7 %), and eggs from the generaOxyurida (59 %), along with protozoa from the family Trichomonadida, in reptiles. Capillaria sp. was most prevalent in hedgehogs (33.4 %). Acanthocephala eggs, as well as protozoa from the Giardia and Entamoeba genera, were more frequently found in primates. Parasites common to animals and humans, which may become a source of infection for the latter under certain conditions, have been identified in pet animals.

Efficacy of ivermectin to control Strongyloides stercoralis infection in sheltered dogs

In dogs, information on treatments against S. stercoralis infection is rare and anecdotal. The aim of the present work was to evaluate the treatment outcome of S. stercoralis natural infection in sheltered dogs. Furthermore, based on the potential risk of infection, people working in the infected shelter were also tested. Seventeen sheltered dogs positive to S. stercoralis using the Baermann test were treated with ivermectin 200 μg/kg/sid/os for two consecutive days. Only two dogs showed clinical signs suggestive of strongyloidiasis (diarrhea, weigh loss) at diagnosis. All dogs showed consistently negative results for S. stercoralis at weekly monitoring after treatment using both the direct microscopy and Baermann test. Real-time PCR confirmed negative results at the last follow up 2 months after treatment. Serology performed at the first diagnosis showed that 82% and 41% of dogs were positive for S. stercoralis using an IFAT (titres ranging from 1:40 to 1:320) and ELISA, respectively. Two months after treatment, IFAT titres were strongly reduced in all animals. The results of clinical pathological laboratory tests at diagnosis in the positive dogs were within normal ranges, except for the two symptomatic dogs. Serum collected from two out of 14 shelter workers tested positive with titres 1:20 and 1:40 for S. stercoralis using an IFAT. Results of the study confirm that ivermectin was an effective treatment option to control S. stercoralis infection in dogs. Shelter workers are at risk of infection with S. stercoralis, thus the application of correct deworming protocols to reduce the environmental infective larval burden is essential to protect dogs and probably also shelter workers from the risk of infection.

Strongyloides stercoralis infection in imported and local dogs in Switzerland: from clinics to molecular genetics

Strongyloides stercoralis is a worldwide-distributed intestinal nematode affecting mainly humans and dogs. Canine strongyloidosis is generally characterised by diarrhoea, malabsorption and bronchopneumonia, and may be fatal in cases of impaired immunity. In recent years, molecular and epidemiological studies suggested that host-adapted populations of S. stercoralis with different zoonotic potential may exist. Clinical and subclinical cases of S. stercoralis infection have been increasingly diagnosed in imported (France, Belgium, Bulgaria) and locally born dogs in Switzerland, showing that this parasite is currently circulating in Europe. Three of these clinical cases will be described here. All three dogs presented severe disease, characterised by harsh diarrhoea, dehydration, vomiting, respiratory and/or neurologic signs, and needed intensive care and hospitalisation. One of these dogs was related to a Swiss breeding kennel, in which the infection was subsequently diagnosed in several other dogs. Faeces were analysed by three coproscopical methods including (i) the Baermann technique, which consistently identified the typical S. stercoralis first-stage larvae in both clinical and subclinical infections, (ii) the sedimentation-zinc chloride flotation and (iii) sodium acetate-acetic acid-formalin concentration (SAFC) methods, which allowed the additional identification of parasitic females and/or eggs in two of the clinical cases. Interestingly, S. stercoralis isolated from all three independent clinical cases exhibited an identical genetic background on the nuclear 18S rDNA (fragment involving hypervariable regions I and IV) and the mitochondrial cytochrome oxidase subunit I (cox1) loci, similar to that of zoonotic isolates from other geographical regions, and not to that of dog-adapted variants. Due to the clinical relevance and zoonotic potential of this parasite, the awareness of both diagnosticians and clinicians is strongly required.

First Case of Strongyloides stercoralis Infection in a Dog in the Republic of Macedonia

A six-month-old Pomeranian male dog was referred due to a month long history of unformed, soft faeces and mild weight loss. Stool analyses by direct faecal smear, Zinc sulphate flotation and the Baermann concentration method revealed an infection with Strongyloides stercoralis. The dog was initially treated once with a combination drug of praziquantel, pyrantel and febantel (½ Drontal® Plus Tablets for puppies and small dogs; Bayer; i.e. 31.5 mg/kg bodyweight of febantel ). The treatment was repeated after 12 days with the same dosage for 3 consecutive days. The stool analyses performed 14 days and 3 months after the second treatment were negative for S. stercoralis larvae. The results suggest that a repeated treatment with Drontal® Plus Tablets is effective against S. stercoralis in dogs and has no adverse effects.