Retrospective survey of endoparasitism identified in feces of client-owned dogs in North America from 2007 through 2018

Altered larval activation response associated with multidrug resistance in the canine hookworm Ancylostoma caninum

Parasitic gastrointestinal nematodes pose significant health risks to humans, livestock, and companion animals, and their control relies heavily on the use of anthelmintic drugs. Overuse of these drugs has led to the emergence of resistant nematode populations. Herein, a naturally occurring isolate (referred to as BCR) of the dog hookworm, Ancylostoma caninum, that is resistant to 3 major classes of anthelmintics is characterized. Various drug assays were used to determine the resistance of BCR to thiabendazole, ivermectin, moxidectin and pyrantel pamoate. When compared to a drug-susceptible isolate of A. caninum, BCR was shown to be significantly resistant to all 4 of the drugs tested. Multiple single nucleotide polymorphisms have been shown to impart benzimidazole resistance, including the F167Y mutation in the β-tubulin isotype 1 gene, which was confirmed to be present in BCR through molecular analysis. The frequency of the resistant allele in BCR was 76.3% following its first passage in the lab, which represented an increase from approximately 50% in the founding hookworm population. A second, recently described mutation in codon 134 (Q134H) was also detected at lower frequency in the BCR population. Additionally, BCR exhibits an altered larval activation phenotype compared to the susceptible isolate, suggesting differences in the signalling pathways involved in the activation process which may be associated with resistance. Further characterization of this isolate will provide insights into the mechanisms of resistance to macrocyclic lactones and tetrahydropyrimidine anthelmintics.

Diagnosis of canine intestinal parasites: Improved detection of Dipylidium caninum infection through coproantigen testing

Intestinal parasites, including cestodes like Dipylidium caninum, are common in dogs in the United States of America (USA), but fecal flotation consistently, and, at times, dramatically, fails to identify many of these infections. To determine the extent to which including coproantigen testing for D. caninum would improve the identification of dogs infected with this cestode, we evaluated fecal samples from 877 dogs (589 pet and 288 from municipal shelters) from six USA states using zinc sulfate (specific gravity 1.24) fecal flotation with centrifugation along with coproantigen detection for Giardia sp., hookworms, ascarids, and Trichuris vulpis. For D. caninum, PCR of perianal swabs was included. Intestinal parasite infections were identified, using centrifugal fecal flotation or coproantigen, in 265 dogs (13.2 % pet, 64.9 % shelter). Dipylidium caninum infection was detected in 5.6 % of dogs with the combination of coproantigen and centrifugal fecal flotation, and 7.3 % of dogs when perianal swab results were included; prevalence varied by diagnostic method, population, and geographic region. In pet dogs, D. caninum infection was identified by fecal flotation (0), coproantigen (2.2 %), or perianal swabs (1.2 %). The same methods revealed infection in 0.3 %, 12.5 %, and 11.1 % of shelter dogs, respectively. Frequent use of praziquantel in shelter dogs (116/288; 40.3 %) may have reduced prevalence. Positive and negative agreement of D. caninum coproantigen with perianal swab PCR in pet dogs was 85.7 % and 98.8 %, respectively. Multiple logistic regression analysis accounting for region, population, and age found D. caninum infection to be more common in shelter dogs relative to pet (adjusted OR 4.91 [2.48, 10.24]) and in the Southcentral and Southeast regions relative to North (adjusted OR 9.59 [1.92, 174.13] and 17.69 [3.67, 318.09] respectively). Coproantigen testing also enhanced the detection of other intestinal parasites over fecal flotation alone, including Giardia sp. (14.7 % vs 3.3 %), hookworms (13.8 % vs 8.4 %), ascarids (2.9 % vs 2.2 %), and T. vulpis (2.9 % vs 1.4 %). Together, these data indicate that the coproantigen assay employed increases detection of D. caninum infections several fold, supporting the use of this test in clinical practice, and add to a growing body of research documenting enhanced diagnosis through implementation of multiple laboratory-based methods.

Immunoassay for detection of Dipylidium caninum coproantigen in dogs and cats

Dipylidium caninum infections in dogs and cats are underestimated because of a lack of proglottid observations and poor recovery of parasite elements by centrifugal flotation. We developed an immunoassay that employs a pair of monoclonal antibodies to capture D. caninum-specific coproantigen in fecal extracts from dogs and cats. Real-time PCR for D. caninum DNA in perianal swabs and observation of proglottids were used as reference methods. In 6 experimentally infected dogs, parasite DNA, coproantigen, and proglottid segments were first detected at 22, 23, and 26 d post-infection, respectively. Praziquantel treatment of 3 experimentally infected dogs resulted in the elimination of both coproantigen and proglottid shedding within 1-5 d post-treatment; however, parasite DNA persisted for 14 d. Immunohistochemistry on immature and mature tapeworm segments using an antibody against the coproantigen supports the premise that the antigen is produced in mature segments. We assessed the performance of our coproantigen test in natural infections in 78 dogs from a flea-endemic area. Of the 12 antigen-positive samples, 11 were confirmed with a positive PCR test and/or proglottid observation. Finally, we evaluated a convenience sample set of 730 canine and 163 feline fecal samples obtained from a commercial diagnostic laboratory; D. caninum antigen was detected in 4.1% of the canine and 12.9% of the feline samples, whereas parasite elements were observed in only 0.028% of samples. Our coproantigen immunoassay provides a sensitive method for the detection of D. caninum infection in dogs and cats.

Spirometra infection in a captive Samar cobra (Naja samarensis) in the United States: An imported case?

We report a case of Spirometra infection in a Samar cobra (Naja samarensis) imported from the Philippines, belonging to a zoological collection in the southern United States. Under a poor post-surgical prognosis, the snake was euthanized, and at necropsy plerocercoids of a Diphyllobotriidea were found in its subcutaneous tissues and musculature. Molecular and phylogenetic analyses of the complete cytochrome oxidase c subunit I (cox1) gene of the mitochondrial DNA confirmed that the isolate belonged to the genus Spirometra and was closely related to Spirometra mansoni isolates from Asian countries (bootstrap support = 99.4%). Considering the origin and clinical history and handling of the animal, the snake probably arrived infected in America. We suggest the inclusion of diagnostic imaging in the investigation of sparganosis in research and disease surveillance protocols applied in the pre- and post-quarantine period to asymptomatic animals imported from endemic areas.

A repeated cross-sectional study of intestinal parasites in Texas shelter dogs using fecal flotation and saline sedimentation

Estimates of intestinal parasite prevalence in canine populations have largely been based on use of fecal flotation methods only. Dogs in animal shelters are likely at higher risk of intestinal parasite infection because of their previous exposure history. Our objectives were to estimate the prevalence of intestinal parasites among Texas shelter dogs using centrifugal fecal flotation and saline sedimentation techniques, to identify risk factors for infection, and to compare proportions of positive samples detected via fecal flotation vs. saline sedimentation for the most common parasites. Using a repeated cross-sectional study design, we collected fecal samples from dogs on three visits to each of seven Texas animal shelters between May 2013 and December 2014. Fecal flotation and/or saline sedimentation were used to identify parasites in samples. Fecal samples were collected from 529 dogs. The most frequently detected parasites were Ancylostoma caninum (26.4% via fecal flotation, 20.7% via saline sedimentation) and Trichuris vulpis (12.0% via fecal flotation, 14.1% via saline sedimentation). Risk factors for certain parasites were identified; for example, dogs with abnormal fecal consistency were more likely to be shedding T. vulpis eggs than dogs with normal fecal consistency (OR = 1.8, p = 0.005). The addition of fecal sedimentation not only added to the number of parasite species detected in this study, but it also increased the number of dogs diagnosed with the common intestinal parasites that are primarily detected using fecal flotation methods. Texas shelter dogs carry a high burden of intestinal parasites, including those of zoonotic importance.

Dipylidium caninum in the twenty-first century: epidemiological studies and reported cases in companion animals and humans

Background

Dipilidiosis is a parasitic disease caused by the tapeworm Dipylidium caninum. Fleas and, less frequently, lice act as an intermediate host, and their ingestion is required for infection to occur. While the disease mainly affects domestic and wild carnivores, it is also considered a zoonotic disease, with most human cases reported in children. Dipylidium caninum is considered to be the most common tapeworm infesting companion animals, but dipilidosis in humans is rare. The aims of this review were to improve current understanding of the epidemiology of this parasitosis and its management by the medical and veterinary community.

Methods

A comprehensive review of the published literature during the last 21 years (2000–2021) on the epidemiology, clinical features, diagnosis, treatment and prevention measures of D. caninum infection and dipilidiosis in companion animals and humans was conducted.

Results

Using predefined eligibility criteria for a search of the published literature, we retrieved and screened 280 publications. Of these, 161 (141 epidemiological studies, 20 case reports [16 human cases]) were considered for inclusion in this review. This parasitosis is present worldwide; however, despite being the most frequent cestode infection in animals, it is often underdiagnosed using common coprological techniques. Its diagnosis in humans has also proved challenging, being frequently confused with pinworm infection, leading to inappropriate treatment and to the persistence of the disease over time. Prevention measures include control of ectoparasites in animals and the environment, as well as regular deworming of animals, most commonly with praziquantel.

Conclusions

The diagnosis of dipilidiosis remains challenging in both animals and humans, primarily due to the low sensitivity of the diagnostic methods currently available and a lack of knowledge of the morphological characteristics of the parasite. Although treatment with the appropriate anti-cestode compounds is well tolerated and results in resolution of the infection, indiscriminate use of these compounds may predispose to an increase in resistance. Given the worldwide distribution of this parasite, it is essential to act on several fronts, with a focus on health education for children and animal owners and the control of intermediate hosts, both in animals and in the surrounding environment.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05243-5.

Deworming Schemes’ Efficacy for Adult Dogs with Mixed Gastro-Intestinal Helminthoses

Mixed gastrointestinal helminthoses, which combines Toxocara canis, Trichuris (T.) vulpis, Toxascaris leoninа, Uncinaria stenocephala, Ancylostoma caninum, and Dipylidium caninum in various combinations, are very common pets’ problems worldwide. It is unlikely necessary to choose between 100 % efficiency and for the patient’s body to heal the infected animals safely. The present work aims to develop an affordable scheme for adult dogs’ deworming, which will create a minimum load on the body due to the low drugs’ toxicity. Mixed breed dogs, 1—5 years old, representing both sexes, spontaneously infected with T. vulpis (100 % prevalence) in combination with other gastrointestinal helminths (from 12.7 to 45.1 %) were selected for study. Regimens combining Caniquantel® Plus (fenbendazole + praziquantel) and fenbendazole with a 24-hour interval were tested. After a single treatment of experimental animals with Caniquantel® Plus, no helminth eggs were detected in their faeces after three days, except for T. vulpis. Seven days after the start of the experiment, the intensity of infection of this nematode decreased by only 22.0 % (P < 0.001). Bodies and fragments of dead helminths were found in faeces 1—4 days after de-worming, with T. vulpis isolated only in 2 days in small quantities (4.54 ± 0.21 specimens per 100 g of faeces). Two-stage deworming with Caniquantel® Plus and fenbendazole after 24 hours resulted in 100 % efficiency against eggs of all parasites after five days. Helminths’ bodies stopped excreting after four days, and T. vulpis was detected within three days in substantive quantities (from 10.03 ± 0.45 to 36.8 ± 1.2 specimens per 100 g of faeces).

Risk factors and impact of COVID-19-related clinic closures on the detection of gastrointestinal parasites in dogs, a cross-sectional study

Infections with endoparasites, especially gastrointestinal helminths, are a common finding in client-owned dogs. The Community Practice section at the Ohio State University Veterinary Medical Center (OSU-VMC) follows Companion Animal Parasite Council, American Animal Hospital Association, and American Veterinary Medical Association guidelines for parasitology by recommending annual fecal analyses for dogs and prescribing year-round, broad-spectrum parasite preventatives. There is increasing interest in determining if parasite occurrence is changing in client-owned dogs. Therefore, a retrospective study was designed to examine risk factors associated with the detection of parasites in samples submitted to the OSU-VMC Clinical Veterinary Parasitology Diagnostic Laboratory. Of the 1198 canine fecal samples, 254 (21.2%) of these samples had a positive fecal analysis for gastrointestinal (GI) parasites. The age of the dog, time of year, reproductive status, purpose of fecal examination, GI signs, and type of parasite preventatives were assessed as potential risk factors for GI parasite infection in dogs. To determine if Coronavirus Disease 2019 (COVID-19)-associated hospital restrictions impacted the number of fecal examinations performed, data from January to December 2020, was compared to the same period in 2019. There was nearly a 50% reduction in canine fecal samples submitted to the OSU-VMC Clinical Veterinary Parasitology Diagnostic Laboratory in March 2020 compared to March 2019. At least one canine GI parasite was found in over 20% of all 1198 canine fecal samples (21.2%, 254/1198). The most commonly detected canine GI parasite in all the fecal samples was hookworm at 9.6% (115/1198), followed by Giardia sp. at 7.6% (91/1198). Age, use of parasite preventatives, breed, and reproductive status were found to be associated with parasite occurrence in the dog samples. Identifying such risk factors in dogs will guide veterinarians to advise annual fecal examinations more strongly to clients with high-risk dogs or when routine health visits are postponed for an extended period.

Retrospective study of canine endoparasites diagnosed by fecal flotation methods analyzed across veterinary parasitology diagnostic laboratories, United States, 2018

Background

Companion animal endoparasites play a substantial role in both veterinary medicine and public health. Updated epidemiological studies are necessary to identify trends in occurrence and distribution of these parasites, and their associated risk factors. This study aimed to assess the occurrence of canine endoparasites  retrospectively, using fecal flotation  test data available through participating academic veterinary parasitology diagnostic laboratories across the United States of America (USA).

Methods

Canine fecal flotation records from ten veterinary diagnostic laboratories located in nine states in the USA acquired from January 1, 2018, to December 31, 2018, were included.

Results

A total of 4692 fecal flotation test results were obtained, with a majority comprised of client-owned dogs (3262; 69.52%), followed by research dogs (375; 8.00%), and shelter dogs (122; 2.60%). Samples from 976 (20.80%) dogs were positive for at least one parasite, and co-infections of two or more parasites were found in 3.82% (179/4692) of the samples. The five most commonly detected parasites were: Giardia sp., (8.33%; 391/4692), Ancylostomatidae (5.63%; 264/4692), Cystoisospora spp. (4.35%; 204/4692), Toxocara canis (2.49%;117/4692), and Trichuris vulpis (2.43%; 114/4692). Various other internal parasites, including gastrointestinal and respiratory nematodes, cestodes, trematodes, and protozoans were detected in less than 1% of samples.

Conclusions

These data illustrate the importance of parasite prevention, routine fecal screening, and treatment of pet dogs. Additionally, pet owners should be educated about general parasite prevalence, prevention, and anthelmintic treatment regimens to reduce the risks of environmental contamination and zoonotic transmission.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-04960-7.

Global prevalence of Mesocestoides infections in animals - A systematic review and meta-analysis

Mesocestoides spp. are zoonotic cestodes found as adults in carnivorous domestic and wild definitive hosts and as metacestodes in several taxa of intermediate hosts. Although several regional studies record its occurrence in different host populations, the global prevalence and patterns of occurrence of Mesocestoides spp. are not fully understood. The objective of this study was to conduct a systematic review and meta-analysis of published literature to estimate the global prevalence of Mesocestoides spp. in major definitive and intermediate host taxa. Records published in English were collected from NCBI PubMed, Science Direct, Web of Science and Google Scholar databases, with 364 papers being included in the meta-analysis. The overall pooled prevalence estimates show that 21.72 % (95 % CI: 18.49-25.14) of terrestrial carnivore definitive hosts and 7.09 % (95 % CI: 5.79-8.51) of intermediate hosts are infected. Among definitive hosts, opossums and foxes were most commonly infected with pooled global prevalence of 48.16 % (95 % CI: 14.62 - 82.69) and 35.97 % (295 % CI: 9.54 - 42.66) respectively. Pooled global prevalence in domestic dogs and cats were 7.97 % (95 % CI: 5.67 - 10.63) and 8.32 % (95 % CI: 3.78 - 14.41) respectively. Among intermediate hosts, birds and snakes were most commonly infected with pooled global prevalence of 16.19 % (95 %CI: 5.9 - 30.31) and 15.74 % (95 % CI: 10.59 - 21.69) respectively. Our analysis demonstrates that prevalence of Mesocestoides spp. is variable across the world. The sylvatic cycle in wild hosts is likely to be more important than the domestic cycle for the maintenance of Mesocestoides spp. globally. Currently available genetic data at the mitochondrial COI locus was also phylogenetically analyzed. The genetic data supports the taxonomic distinctiveness of only a few of the numerous morphologically described Mesocestoides spp.

The Role of Nile Tilapia (Oreochromis niloticus) in the Life Cycle of Toxocara spp

The present study aimed to experimentally assess Nile tilapia as potential paratenic host of Toxocara spp. A total of 15 Nile tilapia (Oreochromis niloticus) were fed with 300 embryonated Toxocara canis eggs by oral gavage, while five others of the control group received distilled water. The fish were individually analyzed at 16, 24, 48, 72, and 240 h after inoculation. Water contamination was assessed, and tissue migration by liver, gastrointestinal tract (GIT), eyes, and central nervous system. A murine model was used as the paratenic host for egg infectivity assessment. Eggs and larvae were found in plastic tank water and fish GIT, ranging from 23 to 86% per fish. Eggs and larvae were recovered from the tank water (76.3%) and fish GIT (23.7%). The counting of eggs and larvae observed was negatively correlated with number of eggs and larvae in the water tank (rho = -0.698, p = 0.003). Shedding of embryonated eggs was first detected at 16 and up to 240 h, with significant egg and larvae yield decrease on water-shedding (p = 0.001) and in the GIT (p = 0.007). Although no T. canis larva was recovered in fish tissues, egg infectivity after fish GIT transit was experimentally confirmed by mice assessment. In conclusion, despite shedding viable embryonated eggs through the gastrointestinal tract, tilapias may not play a role as a suitable paratenic hosts for Toxocara spp., posing low risk of zoonotic transmission by fish meat consumption.

Efficacy of a low-dose praziquantel and fenbendazole protocol in the treatment of asymptomatic schistosomiasis in dogs

Background

Established treatment protocols for schistosomiasis (Heterobilharzia americana) in dogs are expensive. Anecdotal reports suggest that lower doses of praziquantel, combined with fenbendazole, may eliminate asymptomatic infections.

Objectives

Evaluate the efficacy of a low‐dose praziquantel and fenbendazole protocol to manage asymptomatic schistosomiasis in dogs and compare fecal saline sedimentation (FSS) and fecal PCR (FPCR) for therapeutic monitoring.

Animals

Twelve asymptomatic dogs with positive FPCR and FSS results for schistosomiasis.

Methods

Prospective observational study. On day 0, dogs received praziquantel at a median dose of 5 mg/kg PO q8h for 2 days, with fenbendazole at 24 mg/kg PO q24h for 7 days. Fecal PCR and FSS were repeated in all dogs on days 30, 60, and 90.

Results

By day 30, 10 of 12 dogs were negative by FSS, but only 3 of 12 were negative by FPCR. By day 60, all 12 dogs were negative by FSS, and 8 of 12 had become negative by FPCR. By day 90, all 12 dogs remained negative by FSS, but 5 of 12 were positive by FPCR (including 2 that were negative by FPCR on day 60). Three dogs that were positive by FPCR on day 60 were re‐treated and subsequently became both FPCR and FSS negative. One FPCR‐positive dog developed a mild increase in serum ALP activity, another developed mild hypercalcemia, and a third developed diarrhea.

Conclusions and Clinical Importance

A low‐dose praziquantel/fenbendazole protocol may be effective for asymptomatic schistosomiasis in some dogs, but monitoring to ensure treatment success is recommended. Fecal saline sedimentation and FPCR may demonstrate discrepant results, with FPCR being positive more frequently.

Further evaluation and validation of the VETSCAN IMAGYST: in-clinic feline and canine fecal parasite detection system integrated with a deep learning algorithm

Background

Fecal examinations in pet cats and dogs are key components of routine veterinary practice; however, their accuracy is influenced by diagnostic methodologies and the experience level of personnel performing the tests. The VETSCAN IMAGYST system was developed to provide simpler and easier fecal examinations which are less influenced by examiners’ skills. This system consists of three components: a sample preparation device, an automated microscope scanner, and analysis software. The objectives of this study were to qualitatively evaluate the performance of the VETSCAN IMAGYST system on feline parasites (Ancylostoma and Toxocara cati) and protozoan parasites (Cystoisospora and Giardia) and to assess and compare the performance of the VETSCAN IMAGYST centrifugal flotation method to reference centrifugal and passive flotation methods.

Methods

To evaluate the diagnostic performance of the scanning and algorithmic components of the VETSCAN IMAGYST system, fecal slides were prepared by the VETSCAN IMAGYST centrifugal flotation technique with pre-screened fecal samples collected from dogs and cats and examined by both an algorithm and parasitologists. To assess the performance of the VETSCAN IMAGYST centrifugal flotation technique, diagnostic sensitivity and specificity were calculated and compared to those of conventional flotation techniques.

Results

The performance of the VETSCAN IMAGYST algorithm closely correlated with evaluations by parasitologists, with sensitivity of 75.8–100% and specificity of 93.1-100% across the targeted parasites. For samples with 50 eggs or less per slide, Lin’s concordance correlation coefficients ranged from 0.70 to 0.95 across the targeted parasites. The results of the VETSCAN IMAGYST centrifugal flotation method correlated well with those of the conventional centrifugal flotation method across the targeted parasites: sensitivity of 65.7–100% and specificity of 97.6–100%. Similar results were observed for the conventional passive flotation method compared to the conventional centrifugal flotation method: sensitivity of 56.4–91.7% and specificity of 99.4–100%.

Conclusions

The VETSCAN IMAGYST scanning and algorithmic systems with the VETSCAN IMAGYST fecal preparation technique demonstrated a similar qualitative performance to the parasitologists’ examinations with conventional fecal flotation techniques. Given the deep learning nature of the VETSCAN IMAGYST system, its performance is expected to improve over time, enabling it to be utilized in veterinary clinics to perform fecal examinations accurately and efficiently.

Sparganosis due to Spirometra sp. (cestoda; Diphyllobothriidae) in captive meerkats (Suricata suricatta)

We report three cases of sparganosis due to plerocercoids of the tapeworm Spirometra sp. in captive meerkats (Suricata suricatta) from a zoo exhibit in the southeastern United States. Two meerkats were euthanized, one due to an uncontrollable seizure and the other due to trauma, and at necropsy cysts containing cestode larvae were observed. A third meerkat had a subcutaneous nodule surgically removed, which contained similar larvae. The third animal died years later, and had numerous cestode larvae in the pleural and peritoneal cavities. The larvae were morphologically identified as plerocercoids of diphyllobothriidean cestodes. On necropsy, multiple nodules, ranging in size from 2.5 to 3.0 cm, were observed in the subcutaneous tissue and muscles. Multifocally, separating skeletal muscle fibers were longitudinal and transversal sections of cestode larva. Histologically, parasitic cysts contained large numbers of neutrophils and macrophages, admixed with proteinaceous material. Molecular and phylogenetic analyses confirmed that specimens from one of the meerkats belonged to the genus Spirometra and was closely related to Spirometra plerocercoids isolated from a snake from the United States and wild felids from South America. Meerkats likely became infected by ingesting infected second intermediate hosts, such as amphibians and reptiles that may have entered the exhibit. Management practices that minimize access of meerkats and other susceptible hosts to intermediate hosts should be implemented.