Demonstration of reduced efficacy against cyathostomins without change in species composition after pyrantel embonate treatment in Swedish equine establishments.

Consisting of approximately 50 different species, the cyathostomin parasites are ubiquitous in grazing horses. Co-infection with several species is common, and large burdens can cause the fatal disease of larval cyathostominosis. Due to intense anthelmintic drug use, cyathostomin resistance has developed to all available anthelmintic drug groups. Resistance to the anthelmintic drug pyrantel (PYR) has been documented in over 90% of studies published over the past two decades. In Sweden, a study performed in the early 2000s only confirmed resistance in 4.5% of farms. Further, prescription-only administration of equine anthelmintic drugs was enforced in Sweden in 2007. However, it is unknown if this conservative drug use has maintained PYR efficacy in cyathostomins. The aim of the present study was to investigate the effect of PYR on cyathostomin infection in Sweden using fecal egg count reduction tests (FECRTs). Further, the effect of PYR treatment on cyathostomin species composition was studied using metabarcoding. Sixteen farms with at least six horses excreting a minimum of 100 eggs per gram feces were included. Using the current World Association for the Advancement of Veterinary Parasitology (WAAVP) guidelines, PYR resistance was demonstrated in nine of farms, with seven farms showing full susceptibility. Farms with low biosecurity measures had significantly lower efficacy of PYR treatment. The most common cyathostomin species were Cylicocyclus nassatus, Cyathostomum catinatum, Cylicostephanus longibursatus, Cys. calicatus, Cys. goldi, Cys. minutus, Coronocyclus coronatus and Cya. pateratum, accounting for 97% of all sequence reads prior to treatment. Of these, Cyc. nassatus and Cya. catinatum had the highest occurrence, accounting for 68% of all sequence reads prior to PYR treatment. Treatment did not significantly affect the species composition. The results highlight the importance of drug efficacy testing when using PYR to treat cyathostomin infection, even when selective anthelmintic treatment and thus low treatment intensity, is used on the farm.

Selective Anthelmintic Treatment in Horses in Sweden Based on Coprological Analyses: Ten-Year Results.

In Sweden, routine deworming has been used for several decades; however, to slow down the development of anthelmintic resistance, selective treatment is currently recommended. As part of a monitoring programme, equestrian premises submitted faecal samples to the National Veterinary Institute (SVA) twice per year between 2008 and 2017. Analyses for strongyles (small and large), tapeworms and ascarids, followed by premise-specific advice regarding deworming and parasite control strategies, were provided. In total, 43,330 faecal samples, collected from 26,625 horses on 935 premises in springtime (March to June), were analysed by quantitative or semi-quantitative flotation. Moreover, Strongylus vulgaris was detected by larval culture or PCR. Between 4 and 11% of individual horses tested positive for S. vulgaris and 3-10% were shedding tapeworm eggs. There were recurrent high and low egg shedders; 75% of horses with S. vulgaris appeared to have been recently introduced into the herd; the proportion of S. vulgaris-positive premises increased when individual samples rather than pooled samples were used. Based on the results of S. vulgaris diagnostics and strongyle egg-shedding level, 59% of the horses did not need to be dewormed.

Retained efficacy of ivermectin against cyathostomins in Swedish horse establishments practicing selective anthelmintic treatment.

Cyathostominae are ubiquitous to grazing horses and regarded the most prevalent internal parasite in the horse. Unfortunately, decades of indiscriminate use of anthelmintic drugs have resulted in the development of resistance in cyathostomins to all currently available drug groups, the most recent being a documented lack of efficacy to the macrocyclic lactones (ML). In vivo determination of anthelmintic resistance in horses most often utilises the faecal egg count reduction test (FECRT). Further, a shortened egg reappearance period (ERP) can indicate a change in response to the applied treatment and suggest an upcoming reduction of efficacy. Although both true resistance as demonstrated by the FECRT and shorter ERPs after ML treatment have now been shown in cyathostomins worldwide, the efficacy of ML as regards to cyathostomins in Sweden is currently unknown. The aim of the present study was therefore to determine FECRTs and ERPs after ivermectin (IVM) treatment in Swedish horses. Sixteen equestrian establishments with a minimum of six horses excreting at least 150 eggs per gram faeces (EPG) at screening were selected. For each establishment, FECRTs and ERPs were determined by collecting faecal samples prior to and 14 days after IVM treatment (200 µg/kg), and thereafter at weekly intervals for a total of eight weeks. All participants responded to a questionnaire detailing pasture management methods and anthelmintic routines.Questionnaire results showed that the majority of establishments (69%) only treated horses with anthelmintic drugs if indicated by faecal diagnostics and all of the establishments had a mean FECRT exceeding 99.0% and ERPs ranging from six to over eight weeks. The ERP was shown to increase with age as young individuals were shown to excrete cyathostomin eggs earlier after treatment compared with older horses (R = 0.21, p = 0.015). Riding schools, stud farms and those declaring not to use separate summer and winter paddocks had significantly shorter ERPs (p <0.01).In conclusion, retained ERPs and no confirmed resistance to IVM were found in Swedish equine establishments practising selective anthelmintic treatment, and supports the use of selective deworming regimens as a means of reducing the risk of anthelmintic resistance development.

Evaluation of Strategies to Reduce Equine Strongyle Infective Larvae on Pasture and Study of Larval Migration and Overwintering in a Nordic Climate.

Horses, as grazing animals, are inadvertently exposed to intestinal parasites that, if not controlled, may cause disease. However, the indiscriminate use of anthelmintic drugs has led to drug resistance, highlighting the need for pasture-management practices to reduce the level of parasitic exposure and lessen reliance on drugs. The efficacy of such methods depends both on the epidemiology of the parasites and the prevailing weather conditions. The aim of the study was to investigate the effect of faecal removal and harrowing on reducing the number of parasite larvae in herbage. Moreover, the migratory and survival ability of strongyle larvae in a Nordic climate was studied. Faeces from horses naturally infected with strongyle nematodes were used to contaminate pastures and grass samples were collected to harvest larvae. Twice-weekly faecal removal significantly reduced larval yields, whereas harrowing on a single occasion under dry weather conditions in the summer did not. Strongyle larvae were able to migrate 150 cm from the faecal pats, but most larvae were found within 50 cm. Both Cyathostominae and S. vulgaris survived the winter months with larvae harvested up to 17-18 months after faecal placement. Resting of pastures for one year greatly reduced the parasite level, but two years of rest were required for parasite-free pasture.

Occurrence of Endoparasites in Adult Swedish Dogs: A Coprological Investigation.

The occurrence of endoparasites in Swedish adult dogs (n = 303) was investigated between January and October 2014. Included dogs had to be clinically healthy, older than 1 year and untreated with anthelmintics or endectocides for at least 3 months prior to sampling. They were grouped according to age, category of dog and time since last antiparasitic treatment. Samples were analyzed by flotation to detect parasitic eggs and cysts/oocysts. Among these, 129 (43%) dogs were also analyzed with the Baermann-technique to detect cardiopulmonary larval stages. Parasite dispersal stages were found in 24 (7.9%, CI 95% 4.9-10.1) of the dogs at flotation, while no dog shed cardiopulmonary larval stages. Giardia sp. cysts were observed in 2.6% (n = 8) of dogs examined, cysts of Sarcocystis spp. were observed in 0.6% (n = 2), oocysts of Cystosisopora ohioensis were found in one dog (0.3%). Eggs of Toxocara canis (2.3%, n = 7), Uncinaria stenocephala (1.3%, n = 4) and Trichuris vulpis (0.3%, one dog) were found. None of the dogs were diagnosed with more than one species. Although the occurrence of endoparasites was above the average in dogs ≤ 2 years of age (11.5%), nematodes were more common in older dogs ≥4 years (77.0%). Although the occurrence was lower in working/exhibition dogs (5.9%) than in companion dogs (8.4%) and hunting-dogs (8.6%), these differences were not significant. However, dogs exposed to prey according to the owner had a statistically significant higher prevalence than other dogs (20.5 vs. 5.7%). The Odds Ratio (OR) was 4.0 (CI 95%, 1.58-10.11) for dogs having access to prey, 2.4 (CI 95%, 0.37-8.06) for dogs staying at day-care, and 2 (CI 95%, 0.96-5.96) for bitches. Furthermore, a significant association was observed between infection with nematodes and exposures to prey (p = 0.006). As a reference, data on the endoparasites in canine fecal samples submitted to the National Veterinary Institute (SVA, Uppsala) during 2014 are presented. Overall, this study shows a low occurrence of endoparasites among dogs in Sweden. Any risk-assessment on zoonotic parasites as well as deworming recommendations will take advantage from these updated figures.

Factors associated with Echinococcus multilocularis infection in coyotes in southern Ontario.

Echinococcus multilocularis was recently reported in wild canids across southern Ontario, a newly recognized endemic area in Canada. In such areas, a comprehensive understanding of factors associated with infection in definitive hosts (wild canids) is critical for mitigating risk of transmission to humans. However, little is known about the transmission dynamics of the parasite in definitive hosts for this region. A study was therefore carried out to investigate the association of host-level (sex, body condition), environmental (southern Ontario region, land cover), temporal (season, hunting season, calendar year) and extraneous factors (submitter type) with E. multilocularis infection in coyotes in southern Ontario. Between November 2015 and March 2017, 416 coyotes were collected from across the region as part of a study that investigated the prevalence and distribution of the parasite in wild canids; approximately 24% of coyotes were positive for E. multilocularis. Associations between infection and factors of interest were assessed via a mixed-effects logistic regression model with a random intercept for submitter to account for clustering. Coyotes with poor body condition were at greater odds of E. multilocularis infection than those in good condition (odds ratio [OR] 2.14; 95% CI: 1.08-4.26; p = .030). A negative association was observed between infection in coyotes and the proportion of natural land in a coyote's estimated home range (OR: 0.67; 95% CI: 0.52-0.85; p = .001). Coyotes from the western region of southern Ontario had lower odds of infection compared to coyotes from the central region (OR: 0.26; 95% CI: 0.12-0.55; p < .001). These results can be used to help guide future public health prevention strategies for human alveolar echinococcosis.

Parasite Occurrence and Parasite Management in Swedish Horses Presenting with Gastrointestinal Disease-A Case-Control Study.

All grazing horses are exposed to intestinal parasites, which have the potential to cause gastrointestinal disease. In Sweden, there is a concern about an increase in parasite-related equine gastrointestinal disease, in particular Strongylus vulgaris, since the implementation of prescription-only anthelmintics approximately 10 years ago. In a prospective case-control study, parasitological status, using fecal analyses for strongyle egg counts, the presence of Anoplocephala perfoliata eggs and S. vulgaris Polymerase chain reaction (PCR) as well as serology for S. vulgaris, were compared between horses presenting with or without gastrointestinal disease at a University hospital during a one-year period. Information regarding anthelmintic routines and pasture management was gathered with an owner-filled questionnaire. Although the prevalence of S. vulgaris PCR was 5.5%, 62% of horses were positive in the enzyme-linked immunosorbent assay (ELISA) test and horses with peritonitis showed higher antibody levels for S. vulgaris, as compared to other diagnoses or controls. Overall, 36% of the horse owners used only fecal egg counts (FEC), 32% used FEC combined with specific diagnostics for S. vulgaris or A. perfoliata, and 29% dewormed routinely without prior parasite diagnostics. Effective management methods to reduce the parasitic burden on pastures were rare and considering exposure to S. vulgaris appears high; the study indicates a need for education in specific fecal diagnostics and pasture management.

Echinococcus multilocularis Infection, Southern Ontario, Canada.

Alveolar echinococcosis, the disease caused by infection with the intermediate stage of the Echinococcus multilocularis tapeworm, is typically fatal in humans and dogs when left untreated. Since 2012, alveolar echinococcosis has been diagnosed in 5 dogs, 3 lemurs, and 1 chipmunk in southern Ontario, Canada, a region previously considered free of these tapeworms. Because of human and animal health concerns, we estimated prevalence of infection in wild canids across southern Ontario. During 2015-2017, we collected fecal samples from 460 wild canids (416 coyotes, 44 foxes) during postmortem examination and analyzed them by using a semiautomated magnetic capture probe DNA extraction and real-time PCR method for E. multilocularis DNA. Surprisingly, 23% (95% CI 20%-27%) of samples tested positive. By using a spatial scan test, we identified an infection cluster (relative risk 2.26; p = 0.002) in the western-central region of the province. The cluster encompasses areas of dense human population, suggesting zoonotic transmission.

Prevalence of Strongylus vulgaris in horses after ten years of prescription usage of anthelmintics in Sweden.

Strongylus vulgaris is considered the most pathogenic nematode parasite of the horse. Frequent deworming programs since the 1970s have reduced the prevalence of S. vulgaris to low levels, but to the price of widespread benzimidazole resistance in the small strongyles (cyathostominae) and ivermectin resistance especially in the equine roundworm Parascaris spp. To slow down the progression of anthelmintic resistance in Sweden, horse anthelmintics were made prescription only medicine in 2007 and selective therapy principles were introduced. This means that only individuals with high egg excretion or clinical signs of helminth infection were treated instead of blanket treatment of all horses on a farm. The aims of this study were to investigate the prevalence and risk factors associated with S. vulgaris infection in Sweden ten years after the introduction of a selective therapy regime. A total of 529 faecal samples from 106 farms were collected during March to June in 2016 and 2017. A web-based questionnaire was used to collect information about deworming routines. Strongyle faecal egg counts (FEC) were performed by McMaster and presence of S. vulgaris was demonstrated with a specific PCR on individual larval cultures. Results were analysed by mixed logistic (S. vulgaris prevalence) or linear (FEC) regression models, where farm was included as random factor. The overall prevalence of S. vulgaris at individual and farm levels was 28% and 61%, respectively. We observed a 2.9 increased odds risk of S. vulgaris infection on farms that based their treatment on strongyle FEC only as compared to farms that complemented strongyle FECs with larval cultures or dewormed regularly, 1-4 times per year, without prior diagnosis. We found no association between the prevalence of S. vulgaris and strongyle FEC level, horse age, geographical region or signs of colic. The prevalence of S. vulgaris was 25% in horses shedding ≤150 eggs per gram. Thus horses with low strongyle FECs that are left untreated could be an important source of S. vulgaris infection. This may be an important reason for the approximately three-fold increase in S. vulgaris prevalence since 1999 in Sweden. However, our combined results indicate that selective therapy based on a combination of strongyle FECs and larval cultivation was not associated with an increased risk of S. vulgaris infection. Still, S. vulgaris needs to be monitored continuously and should be taken into careful consideration when the treatment frequency is reduced.

Prevalence of Strongylus vulgaris in horses after ten years of prescription usage of anthelmintics in Sweden.

Strongylus vulgaris is considered the most pathogenic nematode parasite of the horse. Frequent deworming programs since the 1970s have reduced the prevalence of S. vulgaris to low levels, but to the price of widespread benzimidazole resistance in the small strongyles (cyathostominae) and ivermectin resistance especially in the equine roundworm Parascaris spp. To slow down the progression of anthelmintic resistance in Sweden, horse anthelmintics were made prescription only medicine in 2007 and selective therapy principles were introduced. This means that only individuals with high egg excretion or clinical signs of helminth infection were treated instead of blanket treatment of all horses on a farm. The aims of this study were to investigate the prevalence and risk factors associated with S. vulgaris infection in Sweden ten years after the introduction of a selective therapy regime. A total of 529 faecal samples from 106 farms were collected during March to June in 2016 and 2017. A web-based questionnaire was used to collect information about deworming routines. Strongyle faecal egg counts (FEC) were performed by McMaster and presence of S. vulgaris was demonstrated with a specific PCR on individual larval cultures. Results were analysed by mixed logistic (S. vulgaris prevalence) or linear (FEC) regression models, where farm was included as random factor. The overall prevalence of S. vulgaris at individual and farm levels was 28% and 61%, respectively. We observed a 2.9 increased odds risk of S. vulgaris infection on farms that based their treatment on strongyle FEC only as compared to farms that complemented strongyle FECs with larval cultures or dewormed regularly, 1-4 times per year, without prior diagnosis. We found no association between the prevalence of S. vulgaris and strongyle FEC level, horse age, geographical region or signs of colic. The prevalence of S. vulgaris was 25% in horses shedding ≤150 eggs per gram. Thus horses with low strongyle FECs that are left untreated could be an important source of S. vulgaris infection. This may be an important reason for the approximately three-fold increase in S. vulgaris prevalence since 1999 in Sweden. However, our combined results indicate that selective therapy based on a combination of strongyle FECs and larval cultivation was not associated with an increased risk of S. vulgaris infection. Still, S. vulgaris needs to be monitored continuously and should be taken into careful consideration when the treatment frequency is reduced.

Gastrointestinal helminths of gray wolves (Canis lupus lupus) from Sweden.

As the Scandinavian wolf population is limited in size, it is only rarely subject to systematic studies on its disease biology, especially gastrointestinal parasites. Therefore, this study aims to describe the prevalence of gastrointestinal helminths of gray wolves hunted on a limited license as a part of a wildlife management program. Helminths of 20 wolves were examined post mortem by macroscopy and coprology. Intestinal worms of five species were recovered from 18 wolves (90%): Uncinaria stenocephala (90%), Taenia spp. (45%), Alaria alata (25%), and Mesocestoides spp. (5%). Of the taeniid specimens typed by multiplex PCR and sequencing of the cox1 gene, 25% belonged to Taenia hydatigena and 25% to Taenia krabbei. The overall species diversity was low compared to findings from wolves of the northern hemisphere. Fecal eggs of Eucoleus boehmi were detected in 12 wolves (60%). Fecal metastrongylid larvae were found in seven individuals (39%), but PCR analyses specific for Angiostrongylus vasorum were negative. The wolves were in good body condition suggesting that the parasite infestation had no negative impact on the general health of the examined wolves. Although some of the recovered parasite species have zoonotic or veterinary impact, it is not likely that the spare wolf population pose substantial threat to human or veterinary health.

GASTROINTESTINAL PARASITIC INFECTIONS IN DEAD OR DEBILITATED MOOSE ( ALCES ALCES) IN SWEDEN.

: Our objectives were to determine prevalence and intensity of gastrointestinal parasites of dead or euthanized emaciated moose in central and southern Sweden ( n=50) and to assess parasite intensity as a major contributing factor in the poor condition of these moose. All animals were infected and most had gastrointestinal nematodes. Seven parasite species were found in the abomasa and 10 species were found in the small intestine. Coinfections were commonly found in the abomasum ( Ostertagia antipini and Mazamastrongylus dagestanica) and in the small intestine ( Nematodirella alcidis and Trichostrongylus capricola). Moose had many nematodes; the highest numbers were 224,400 and 11,760, in the abomasum and in the small intestine, respectively. Fourteen moose had more than 40,000 gastrointestinal nematodes (excluding large intestine nematodes represented by Trichuris spp. and Oesophagostomum venulosum). Additionally, a moderate prevalence (36%) of protostrongylid larvae (dorsal spine larvae) and a low prevalence (2-4%) of protozoal infections were identified at microscopic examination of feces. Adult moose had significantly more parasites than did subadults. The results did not show parasite load as a single or a major cause of the moose mortality, but they provided an update on the species composition of helminth parasites in moose in Sweden and illustrated the extreme infection intensities that free-ranging moose can have.

Theileria annae in a young Swedish dog.

A severe regenerative anemia was detected in a 12-week-old mixed breed puppy in Sweden. A small protozoan parasite was observed in erythrocytes on a blood smear. It was initially suspected to be Babesia gibsoni based on its size and because B. gibsoni was previously recorded in Sweden. Surprisingly, specific polymerase chain reaction analysis identified the protozoan as Theileria annae. T. annae is endemic in Northwest Spain, is very uncommonly reported elsewhere and has never been recorded in Scandinavia. T. annae has been identified in dogs used for dog fighting, and it is thought to be transmitted by dog bites. This puppy was a mixed pit bull terrier. Pit bull terriers are sometimes used for dog fighting. T. annae has been reported to be transmitted vertically, and in light of the puppy's age, this transmission was suspected in the present case.

Pearsonema (syn Capillaria) plica associated cystitis in a Fennoscandian arctic fox (Vulpes lagopus: a case report.

The bladderworm Pearsonema (syn Capillaria) plica affects domestic dogs and wild carnivores worldwide. A high prevalence in red foxes (Vulpes vulpes) has been reported in many European countries. P. plica inhabits the lower urinary tract and is considered to be of low pathogenic significance in dogs mostly causing asymptomatic infections. However, a higher level of pathogenicity has been reported in foxes. A severe cystitis associated with numerous bladderworms was found in a captive arctic fox (Vulpes lagopus) originating from the endangered Fennoscandian arctic fox population. To our knowledge this is the first description of P. plica infection in an arctic fox.