Variation in haplotypes in single cysts of assemblages C and D, but not of assemblage E of Giardia duodenalis

Background

Giardia duodenalis, a single-celled intestinal parasite, is divided into eight assemblages (A-H), with differences in host specificity. Giardia duodenalis reproduces asexually and cycles between the binucleated trophozoite (4 N) and the infectious cyst with four nuclei (16 N). Interaction between the nuclei is limited. Therefore, genetic drift causes differences in genetic make-up between the non-daughter nuclei; the allelic sequence heterozygosity (ASH). The ASH is low (0.01%—0.0023%) for the related assemblages A and E, higher (0.43–0.53) for assemblage B and much higher (0.74% -0.89%) for the assemblage C and D at the root of the phylogenetic tree. The heterozygosity in assemblage F, in the same clade as assemblage A and E, was unknown. The heterozygosity in the sequences of the gdh and dis3 genes was used as proxy for the ASH and whole genome amplification of single cysts followed by cloning and Sanger sequencing of dis3 fragment could reveal the genetic variation within the cyst. The aim of the study was to determine the level of heterozygosity within pooled and single cysts of different assemblages.

Results

The heterozygosity in gdh and dis3 was determined in pooled cysts of the assemblages A to F. Heterozygosity in the isolates of the assemblages C (n = 2) and D (n = 1) ranged from 0.41% to 0.82% for gdh and dis3 and no heterozygosity was found in the isolates of the assemblages A (n = 4), E (n = 3) and F (n = 3). The heterozygosity in assemblage B (n = 7) was intermediate (0% to 0.62%). Next, the number of haplotypes of dis3 was determined for single cysts of assemblages C, D and E. In the assemblages C and D, two to four haplotypes were found per cyst, while in assemblage E only one haplotype was identified.

Conclusions

Having high heterozygosity is characteristic for the assemblages C and D, while having a low heterozygosity is characteristic for the clade with the assemblages A, E and F.

Presence of more than 1 haplotype per cyst in assemblage C and D suggests differences between the non-daughter nuclei, in contrast to the one haplotype in assemblage E.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-022-02581-3.

Imported Hyalomma ticks in the Netherlands 2018-2020

BACKGROUND

Ticks of the genus Hyalomma, which are vectors for several tick-borne diseases, are occasionally found in areas outside their endemic range including northern parts of Europe. The objective of this study was to analyse adult Hyalomma ticks that were recently found in the Netherlands.

METHODS

Hyalomma ticks were morphologically identified. Cluster analysis, based upon sequence data (cox1 barcoding) for molecular identification, and pathogen detection were performed. Additionally, a cross-sectional survey of horses was conducted to actively search for Hyalomma ticks in summer 2019. Analysis of temperature was done to assess the possibility of (i) introduced engorged nymphs moulting to adults and (ii) establishment of populations in the Netherlands.

RESULTS

Seventeen adult Hyalomma ticks (one in 2018, eleven in 2019, five in 2020) were found by citizens and reported. Fifteen ticks were detected on horses and two on humans. Twelve were identified as H. marginatum, one as H. rufipes and four, of which only photographic images were available, as Hyalomma sp. No Crimean-Congo haemorrhagic fever virus or Babesia/Theileria parasites were detected. One adult tick tested positive for Rickettsia aeschlimannii. In the cross-sectional horse survey, no Hyalomma ticks were found. Analysis of temperatures showed that engorged nymphs arriving on migratory birds in spring were able to moult to adults in 2019 and 2020, and that cumulative daily temperatures in the Netherlands were lower than in areas with established H. marginatum populations.

CONCLUSIONS

Our results show that Hyalomma ticks are regularly introduced in the Netherlands as nymphs. Under the Dutch weather conditions, these nymphs are able to develop to the adult stage, which can be sighted by vigilant citizens. Only one human pathogen, Rickettsia aeschlimannii, was found in one of the ticks. The risk of introduction of tick-borne diseases via Hyalomma ticks on migratory birds is considered to be low. Establishment of permanent Hyalomma populations is considered unlikely under the current Dutch climatic conditions.

ESCCAP-wormbestrijding bij hond en kat

Geen abstract.

Giardia duodenalis multi-locus genotypes in dogs with different levels of synanthropism and clinical signs

BACKGROUND

In dogs, infections with Giardia duodenalis are mainly caused by assemblages C and D, but also by the potentially zoonotic assemblages A and B. The aims of this study were to assess differences in assemblages (i) between dogs living mainly in close proximity to humans (synanthropic dogs) versus dogs living mainly among other dogs, (ii) between samples of dogs with or without loose stool, and (iii) related to the amount of cysts shedding.

METHODS

One hundred eighty-nine qPCR Giardia positive fecal samples of dogs originating from four groups (household, sheltered, hunting, and dogs for which a veterinarian sent a fecal sample to a diagnostic laboratory) were used for genotyping. For this, multi-locus genotyping of beta-giardin, triose phosphate isomerase, and glutamate dehydrogenase and genotyping of SSU rDNA gene fragments were performed. Fecal consistency was scored (loose or non-loose stool), and cysts per gram of feces were determined with qPCR.

RESULTS

Assemblage D was the most prevalent in all groups, followed by the other canid assemblage C. Also, mixed C/D was common. In two (synanthropic) household dogs, the potentially zoonotic assemblage AI was present. Although occurrence of assemblage AI in household dogs was not significantly different from dogs living among other dogs (sheltered and hunting dogs), it was significantly higher compared to dogs for which a sample was sent to a diagnostic laboratory. Dogs with assemblage D shed significantly more cysts than dogs with other assemblages (except for mixed C/D results) or dogs in which no assemblage could be determined. None of the assemblages was significantly associated with loose stool.

CONCLUSION

Not only do dogs mainly shed the canid Giardia duodenalis assemblages D and/or C, the numbers of cysts per gram for the canid assemblage D were also higher than for the potential zoonotic assemblage AI. Based on the assemblages shed by dogs, the risk to public health posed by dogs is estimated to be low, even though the dogs that shed AI were synanthropic household dogs. Loose stool in infected dogs was not associated with any particular Giardia assemblage.

Coprological survey of endoparasite infections in owned dogs and owners' perceptions of endoparasite control in Belgium and the Netherlands

Infections with endoparasites are common in dogs. Some of these parasites are potentially zoonotic and therefore a public health concern. A survey was conducted in twenty-six small animal practices to evaluate the prevalence of endoparasites in Belgian and Dutch owned dogs older than 6 months as well as risk factors associated with infection. Out of 239 faecal samples screened (168 in Belgium and 71 in the Netherlands), 18 dogs were tested positive for at least one type of endoparasite with three dogs co-infected with two parasitic species. Toxocara sp. was the most frequently found endoparasite (4.6%). Three other dogs were positive for Angiostrongylus vasorum (1.4%) using the Baermann method and confirmed in one dog by the Angiodetect® test. Age and predation behaviour were identified as two risk factors associated with endoparasite infection. Although the majority (77%) of the owners in this study reported to administer at least one anthelmintic treatment per year, only a minority of them (24.3%) were aware of the risk to human health, indicating that owner awareness is sub-optimal. For dog owners, human toxocarosis and other potential zoonoses remain an underestimated health concern. The implementation of sustainable parasite control strategies should be promoted taking also into account the public health risk.

Sources of environmental contamination with Toxocara spp.: An omnipresent parasite

Embryonated Toxocara eggs in the environment are considered to be the most important source of human toxocariasis. These eggs, however, are also a source of infection for the definitive and paratenic hosts. Most available literature focuses on Toxocara canis in dogs, or other canids. There are, however, other Toxocara species with their accompanying definitive hosts. Results from studies that modelled patent infections in dogs, cats and foxes show that although dogs are a very important source for environmental contamination with Toxocara eggs, other sources cannot be ignored. For a good understanding of the relative contributions of different definitive hosts to environmental contamination with Toxocara eggs, computational models should be built and fed with data from different fields of expertise as is discussed in this paper.

Prevalence of patent Toxocara spp. infections in dogs and cats in Europe from 1994 to 2019

OBJECTIVES

To provide an overview of Toxocara prevalences in dogs and cats in Europe from the last 25 years.

METHOD

Systematic review of the literature.

RESULTS

Over the past 25 years, prevalence studies of Toxocara spp. have been published from 26 European countries. The average prevalences were 14.6% for T. canis in all dogs and 24.5% for T. cati in all cats. Specified for young dogs until 6 months old this was 41.2%, for young cats until 6 months old 25%, adult owned dogs 11.1%, adult owned cats 16.3%, stray dogs 17.6%, and stray cats 33.5%. A recent study in seven European countries showed a prevalence of 3.4% for adult dogs and 4.2% for adult cats. The prevalences seem not to decrease over the years.

CONCLUSION

The prevalence of patent Toxocara infections over the last 25 years did not show a distinct declining trend. Prevalence data provided by recent modern antigen tests showed much lower results than from older studies. Results from studies using less diverse methods and well-defined study-populations could provide more clarity.

Host factors associated with Giardia duodenalis infection in dogs across multiple diagnostic tests

Background

The aim of this study was to assess potential associations between Giardia duodenalis infection in dogs, as determined by three diagnostic tests, and dog’s group of origin, fecal consistency, age, sex, neuter status, and co-infections with other gastrointestinal parasites.

Methods

Fecal samples from 1291 dogs from four groups (household, shelter, hunting and clinical dogs) were tested with qPCR, rapid enzyme immunochromatographic assay (IDEXX SNAP^®Giardia), and direct immunofluorescence (DFA, Merifluor) for presence of G. duodenalis. Moreover, fecal samples were tested with centrifugation sedimentation flotation (CSF) coproscopical analysis for presence of gastrointestinal parasites. Associations were expressed as odds ratios (ORs).

Results

Several significant associations were found, of which a few were consistent for all three tests and Giardia positivity in general (positive with at least one of these tests). Dogs older than one year were significantly less likely to test positive for Giardia than younger dogs. Group-housed dogs, especially hunting dogs, were significantly more likely to test positive for Giardia compared to household and clinical dogs. A consistently significant association with Trichuris appeared to be driven by the high prevalence in hunting dogs. Although there was no significant association between loose stool and Giardia infection in the overall population, household dogs were significantly more likely to test Giardia-positive when having loose stool. Overall, Giardia-positive dogs with loose stool shed significantly more cysts, both determined semi-quantitatively with CSF and quantitatively by qPCR, than positive dogs with no loose stool. When other gastrointestinal parasites were present, significantly fewer cysts were detected with CSF, but this was not confirmed with qPCR.

Conclusion

Giardia is the most common gastrointestinal parasite in Dutch dogs, except for hunting dogs, in which Trichuris and strongyle-type eggs (hookworms) prevailed. Giardia infection was not significantly associated with loose stool, except for household dogs. Young dogs and group-housed dogs were significantly more often Giardia-positive. These associations were consistent across diagnostic tests. Young dogs, clinical dogs and dogs with loose stool shed Giardia cysts in the highest numbers. If another gastrointestinal parasite was present lower numbers of cysts were observed by microscope (CSF), but not with a molecular method (qPCR).

Comparing four diagnostic tests for Giardia duodenalis in dogs using latent class analysis

Background

To accurately diagnose giardiosis in dogs, knowledge of diagnostic test characteristics and expected prevalence are required. The aim of this work was to estimate test characteristics (sensitivity and specificity) of four commonly used diagnostic tests for detection of Giardia duodenalis in dogs.

Methods

Fecal samples from 573 dogs originating from four populations (household dogs, shelter dogs, hunting dogs and clinical dogs) were examined with centrifugation sedimentation flotation (CSF) coproscopical analysis, direct immunofluorescence assay (DFA, Merifluor Cryptosporidium/Giardia®), a rapid enzyme immunochromatographic assay (IDEXX SNAP Giardia®) and qPCR (SSU rDNA) for presence of G. duodenalis. Bayesian latent class analysis was used to determine test performance characteristics and to estimate G. duodenalis prevalence of each of the four dog populations.

Results

All tests were highly specific. IDEXX SNAP Giardia® showed the highest specificity (99.6%) and qPCR the lowest (85.6%). The sensitivities were much more variable, with qPCR showing the highest (97.0%) and CSF the lowest (48.2%) sensitivity. DFA was more sensitive than IDEXX SNAP Giardia®, but slightly less specific. Prevalences of G. duodenalis differed substantially between populations, with the hunting dogs showing the highest G. duodenalis prevalence (64.9%) and the household dogs the lowest (7.9%).

Conclusions

This study identifies qPCR as a valuable screening tool because of its high sensitivity, whereas methods using microscopy for cyst identification or cyst wall detection should be used in situations where high specificity is required. G. duodenalis is a prevalent gastro-intestinal parasite in Dutch dogs, especially in dogs living in groups (hunting and shelter dogs) and clinical dogs.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-3014-2) contains supplementary material, which is available to authorized users.

Recurrent patent infections with Toxocara canis in household dogs older than six months: a prospective study

BACKGROUND

To reduce environmental contamination with Toxocara canis eggs, the current general advice is to deworm all dogs older than six months on average four times a year. However, only a small proportion of non-juvenile household dogs actually shed T. canis eggs, and some dogs shed eggs more frequently than others. The identification of these frequent shedders and the associated risk factors is an important cornerstone for constructing evidence-based deworming regimens. The purpose of this study is to identify risk factors associated with recurrence of periods of shedding Toxocara eggs in a cohort of household dogs older than six months.

METHODS

We performed a prospective study (July 2011 to October 2014) on shedding Toxocara eggs in a cohort of 938 household dogs older than six months from all over the Netherlands. The median follow-up time was 14 months. Monthly, owners sent faecal samples of their dogs for Toxocara testing and completed a questionnaire. Dogs were dewormed only after diagnosis of a patent infection (PI). Survival analysis was used to assess factors influencing the time to first diagnosed PIs (FPI) and the time to recurrent PIs (RPI).

RESULTS

The overall prevalence of PIs was 4.5 %, resulting in an estimated average incidence of 0.54 PIs/dog/year. No PI was diagnosed in 67.9 % of the dogs, 17.5 % of the dogs went through only one PI and 14.6 % had > 1 PI. Prevalence of PIs always peaked during wintertime. Increased hazards for first diagnosed PIs were associated with coprophagy, geophagy, walking off-leash for ≥ 80 % of walking time, reported worms in the faeces, feeding a commercial diet and suffering from urologic or respiratory conditions. Median time to reinfection was nine months. Factors associated with increased hazards for recurrent PIs were taking corticosteroids, changing dog's main purpose, and proxies for veterinary care-seeking behaviours.

CONCLUSIONS

We concluded that targeted anthelmintic treatments in household dogs may be feasible as PIs tend to (re)occur in specific periods and in groups of dogs at high risk. Moreover, recurrent PIs appear to be influenced more by factors related to impaired immunity than environmental exposure to Toxocara eggs.

Prevalence and risk factors for patent Toxocara infections in cats and cat owners' attitude towards deworming

The prevalence of and risk factors for shedding Toxocara eggs in cats older than 6 months were determined by examining 670 faecal samples collected in 4 cross-sectional studies in the Netherlands. Additionally, cat owners provided information on their attitude towards routine deworming. Samples were examined using the centrifugal sedimentation flotation method. Overall Toxocara prevalence was 7.2 %. Multivariable logistic regression analysis revealed that young age and living in rural areas were significant risk factors for shedding Toxocara eggs. Moreover, the more time a cat was allowed to roam outdoors, the higher was its risk to shed Toxocara as compared to cats with no outdoor access at all. For 199 cats (81.6 % of cats subjected to a deworming regimen) owners provided the reason for treatment. The main reason for routine deworming (80.4 %) concerned the cat’s health and only 10.6 % of the cats were treated for public health reasons. Moreover, the generally advocated four-times-a-year deworming advice was applied on only 24.5 % of cats. We concluded that free roaming is a key factor in the acquisition of patent Toxocara infections leading to the environmental contamination with Toxocara eggs. Additionally, the knowledge of cat owners is still insufficient to expect them to make sound decisions on routine deworming.

Environmental contamination with Toxocara eggs: a quantitative approach to estimate the relative contributions of dogs, cats and foxes, and to assess the efficacy of advised interventions in dogs

Background

Environmental contamination with Toxocara eggs is considered the main source of human toxocariasis. The contribution of different groups of hosts to this contamination is largely unknown. Current deworming advices focus mainly on dogs. However, controversy exists about blind deworming regimens for >6-month-old dogs, as most of them do not actually shed Toxocara eggs. We aim to estimate the contribution of different non-juvenile hosts to the environmental Toxocara egg contamination and to assess the effects of different Toxocara-reducing interventions for dogs.

Methods

A stochastic model was developed to quantify the relative contribution to the environmental contamination with Toxocara eggs of household dogs, household cats, stray cats, and foxes, all older than 6 months in areas with varying urbanization degrees. The model was built upon an existing model developed by Morgan et al. (2013). We used both original and published data on host density, prevalence and intensity of infection, coprophagic behaviour, faeces disposal by owners, and cats’ outdoor access. Scenario analyses were performed to assess the expected reduction in dogs’ egg output according to different deworming regimens and faeces clean-up compliances. Estimates referred to the Netherlands, a country free of stray dogs.

Results

Household dogs accounted for 39 % of the overall egg output of >6-month-old hosts in the Netherlands, followed by stray cats (27 %), household cats (19 %), and foxes (15 %). In urban areas, egg output was dominated by stray cats (81 %). Intervention scenarios revealed that only with a high compliance (90 %) to the four times a year deworming advice, dogs’ contribution would drop from 39 to 28 %. Alternatively, when 50 % of owners would always remove their dogs’ faeces, dogs’ contribution would drop to 20 %.

Conclusion

Among final hosts of Toxocara older than 6 months, dogs are the main contributors to the environmental egg contamination, though cats in total (i.e. both owned and stray) transcend this contribution. A higher than expected compliance to deworming advice is necessary to reduce dogs’ egg output meaningfully. Actions focusing solely on household dogs and cats are unlikely to sufficiently reduce environmental contamination with eggs, as stray cats and foxes are also important contributors.

Increase in number of helminth species from Dutch red foxes over a 35-year period

Background

The red fox (Vulpes vulpes) is host to a community of zoonotic and other helminth species. Tracking their community structure and dynamics over decades is one way to monitor the long term risk of parasitic infectious diseases relevant to public and veterinary health.

Methods

We identified 17 helminth species from 136 foxes by mucosal scraping, centrifugal sedimentation/flotation and the washing and sieving technique. We applied rarefaction analysis to our samples and compared the resulting curve to the helminth community reported in literature 35 years ago.

Results

Fox helminth species significantly increased in number in the last 35 years (p-value <0.025). Toxascaris leonina, Mesocestoides litteratus, Trichuris vulpis and Angiostrongylus vasorum are four new veterinary-relevant species. The zoonotic fox tapeworm (E. multilocularis) was found outside the previously described endemic regions in the Netherlands.

Conclusions

Helminth fauna in Dutch red foxes increased in biodiversity over the last three decades.