Prevalence of liver fluke infection in Irish horses and assessment of a serological test for diagnosis of equine fasciolosis

Equine helminths: prevalence and associated risk factors in Gamo Gofa Zone, Ethiopia

IMPORTANCE

Equines are indispensable in reducing the huge burden on children and women and income generation. On the other hand, minimal attention is given to improving their health and welfare.

OBJECTIVE

This study examined the prevalence and associated risk factors of helminth parasites of equine in the Gamo Gofa Zone.

METHODS

A cross-sectional study was employed from June 2019 to March 2020. The study districts and Kebeles were selected purposively based on agroecology whereas selection of study households and animals were performed based on simple random sampling techniques. Identification of nematode, trematode parasite ova and larvae of D. arnfieldi were done by floatation, sedimentation, and Baermann techniques respectively. Descriptive statistics and logistic regression was applied to estimate the prevalence and association of risk factors with helminth parasites.

RESULTS

The overall helminth parasite prevalence in the study area was 90.4%, 425/470 (95% [CI], 87.16-92.9). The prevalence of Strongyle, Fasciola, O. equi, P. equorum, D. arnfieldi, and mixed parasite infections were 65.1%, 21.7%, 17.4%, 34%, 34%, and 58.1%, respectively. Infections from Fasciola species and D. arnfieldi infection were four ([AOR], 4.4; 95% CI, 2-9.4) and two times (AOR, 2; 95% CI, 1.1-3.6) respectively more likely occur in donkeys than in mules. The occurrence of Strongyle species in midland agroecology was two times (AOR, 2.6; 95% CI, 1.4-4.7) more likely than lowland agroecology.

CONCLUSIONS AND RELEVANCE

The present study identified diverse species of equine helminth parasites that necessitate urgent disease control and prevention measures.

BEVA primary care clinical guidelines: Equine parasite control

BACKGROUND

There is a lack of consensus on how best to balance our need to minimise the risk of parasite-associated disease in the individual horse, with the need to limit the use of anthelmintics in the population to preserve their efficacy through delaying further development of resistance.

OBJECTIVES

To develop evidence-based guidelines utilising a modified GRADE framework.

METHODS

A panel of veterinary scientists with relevant expertise and experience was convened. Relevant research questions were identified and developed with associated search terms being defined. Evidence in the veterinary literature was evaluated using the GRADE evidence-to-decision framework. Literature searches were performed utilising CAB abstracts and PubMed. Where there was insufficient evidence to answer the research question the panel developed practical guidance based on their collective knowledge and experience.

RESULTS

Search results are presented, and recommendation or practical guidance were made in response to 37 clinically relevant questions relating to the use of anthelmintics in horses.

MAIN LIMITATIONS

There was insufficient evidence to answer many of the questions with any degree of certainty and practical guidance frequently had to be based upon extrapolation of relevant information and the panel members' collective experience and opinions.

CONCLUSIONS

Equine parasite control practices and current recommendations have a weak evidence base. These guidelines highlight changes in equine parasite control that should be considered to reduce the threat of parasite-associated disease and delay the development of further anthelmintic resistance.

Fasciola hepatica Infection in Horses in Three Governorates in Northern Egypt: Prevalence and Risk Factors

Fasciola hepatica is a trematode parasite that affects wide range of mammalian hosts including horses. There are no epidemiological data on fasciolosis in Egyptian horses. Hence, the present study aimed to evaluate the seroprevalence of F. hepatica in horses using ELISA as well as assess the associated risk factors for fasciolosis infection. A total of 400 sera samples of horses from three Egyptian governorates were examined. The overall seroprevalence rate in horses was 13% and the disease was more prevalent in Qalubia (14.17%) and Gharbia (16.67%) which are located at Nile Delta. The likelihood of having F. hepatica seropositivity was higher in mixed-breed animals and stallions (OR = 3.97, 95%CI: 1.10-14.28 and OR = 2.07, 95%CI: 1.09-3.93, respectively), and in older horses more than 10 years (OR = 5.69, 95% CI: 1.98-16.36). Horses were more likely to be seropositive with F. hepatica when kept in outdoor housing (OR= 1.53, 95%CI: 0.78-3), during autumn (OR = 3.80, 95%CI: 1.17-12.32) and in the presence of snails (OR = 2.72, 95%CI: 1.34-5.52). Therefore, the obtained data contributes to the understanding of the epidemiology of Fasciola species, assess in establishment of management programmes to reduce disease and public health risks.

High relatedness of bioinformatic data and realistic experimental works on the potentials of Fasciola hepatica and F. gigantica cathepsin L1 as a diagnostic and vaccine antigen

Introduction

Fascioliasis is a parasitic foodborne disease caused by the liver flukes, Fasciola hepatica and F. gigantica. Such parasites cause serious illness in numerous domestic animals and also in humans. Following infection, the parasite secretes a variety of molecules that immediately interact with the host immunity to establish successful infection. These molecules include cathepsin L peptidase 1 (CatL1); the highly investigated diagnostic and vaccine antigens using various animal models. However, a few studies have analyzed the potentials of FhCatL1 as a diagnostic or vaccine antigen using bioinformatic tools and much less for FgCatL1. The present study provides inclusive and exclusive information on the physico-chemical, antigenic and immunogenic properties of F. hepatica cathepsin L1 (FhCatL1) protein using multiple bioinformatic analysis tools and several online web servers. Also, the validation of our employed available online servers was conducted against a huge collection of previously published studies focusing on the properties of FhCatL1as a diagnostic and vaccine antigen.

Methods

For this purpose, the secondary, tertiary, and quaternary structure of FhCatL1 protein were also predicted and analyzed using the SWISS-MODEL server. Validation of the modeled structures was performed by Ramachandran plots. The antigenic epitopes of the protein were predicted by IEDB server.

Results and discussion

Our findings revealed the low similarity of FhCatL1 with mammalian CatL1, lacking signal peptides or transmembrane domain, and the presence of 33 phosphorylation sites. Also, the containment of FhCatL1 for many topological, physico-chemical, immunological properties that favored its function of solubility and interaction with the immune components were reported. In addition, the earlier worldwide reports documented the high efficacy of FhCatL1 as a diagnostic and vaccine antigen in different animals. Altogether, FhCatL1 is considered an excellent candidate for using in commercialized diagnostic assays or vaccine products against fascioliasis in different animal species. Our assessment also included FgCatL1 and reported very similar findings and outputs to those of FhCatL1.

Timing of Transcriptomic Peripheral Blood Mononuclear Cell Responses of Sheep to Fasciola hepatica Infection Differs From Those of Cattle, Reflecting Different Disease Phenotypes

Infection with the zoonotic trematode Fasciola hepatica, common in many regions with a temperate climate, leads to delayed growth and loss of productivity in cattle, while infection in sheep can have more severe effects, potentially leading to death. Previous transcriptomic analyses revealed upregulation of TGFB1, cell death and Toll-like receptor signalling, T-cell activation, and inhibition of nitric oxide production in macrophages in response to infection. However, the differences between ovine and bovine responses have not yet been explored. The objective of this study was to further investigate the transcriptomic response of ovine peripheral blood mononuclear cells (PBMC) to F. hepatica infection, and to elucidate the differences between ovine and bovine PBMC responses. Sixteen male Merino sheep were randomly assigned to infected or control groups (n = 8 per group) and orally infected with 120 F. hepatica metacercariae. Transcriptomic data was generated from PBMC at 0, 2 and 16 weeks post-infection (wpi), and analysed for differentially expressed (DE) genes between infected and control animals at each time point (analysis 1), and for each group relative to time 0 (analysis 2). Analysis 2 was then compared to a similar study performed previously on bovine PBMC. A total of 453 DE genes were found at 2 wpi, and 2 DE genes at 16 wpi (FDR < 0.1, analysis 1). Significantly overrepresented biological pathways at 2 wpi included role of PKR in interferon induction and anti-viral response, death receptor signalling and RIG-I-like receptor signalling, which suggested that an activation of innate response to intracellular nucleic acids and inhibition of cellular apoptosis were taking place. Comparison of analysis 2 with the previous bovine transcriptomic study revealed that anti-inflammatory response pathways which were significantly overrepresented in the acute phase in cattle, including IL-10 signalling, Th2 pathway, and Th1 and Th2 activation were upregulated only in the chronic phase in sheep. We propose that the earlier activation of anti-inflammatory responses in cattle, as compared with sheep, may be related to the general absence of acute clinical signs in cattle. These findings offer scope for "smart vaccination" strategies for this important livestock parasite.

Molecular Characterization of Fasciola spp. from a Donkey (Equus asinus) Using Partial Sequencing of cox1 and nad1

Background

Fasciola hepatica as an important parasite affects health of humans and animals in some tropical and subtropical areas of the world, including Iran. Little is known about the molecular diversity of Fasciola in Equidae. Therefore, this study aimed to characterize the genetic polymorphisms among parasites.

Methods

Eight adult Fasciola spp. isolates were collected from a working donkey after necropsy in Shiraz, southwestern Iran, in 2018. Primarily, various parameters were measured morphologically. Subsequently, DNA was extracted from each fluke and molecular markers of cytochrome C oxidase (cox1) and NADH dehydrogenase 1(nad1) from individual Fasciola isolates were amplified using PCR assay and sequence data were employed for molecular and phylogenetic analysis. Genetic diversity between isolates was evaluated by comparing the sequences of these two mitochondrial regions.

Results

Based on the morphological and analyzed mitochondrial sequences, all of eight donkey isolates (100%) were identified as F. hepatica. Moreover, nine and five nucleotide polymorphisms were identified in the cox1and nad1 region sequences, respectively.

Conclusion

Accordingly, phylogenetic data revealed five and four haplotypes among donkey isolates based on the cox1and nad1 markers. Similarly, some of these haplotypes have been previously reported from different host species in Iran as well as all around the world.

The prevalence and risk factors of liver fluke infection in Mexican horses, donkeys and mules in tropical and temperate regions

The objective of the present study was to determine the seroprevalence of Fasciola hepatica infection in horses, donkeys and mules from different climate regions in two states of Mexico. A total of 594 serum samples were analysed for immunoglobulin G (IgG) antibodies using enzyme-linked immunosorbent assay (ELISA), with excretory-secretory (E/S) products as the antigen. The diagnostic sensitivity and specificity of serum IgG ELISA were 100% and 97.2%, respectively. We collected data using a questionnaire. The overall prevalence of the parasite in equids between May 2018 and April 2019 was 13.1% (78 out of 594). The highest prevalence was found in mules (17.9%), followed by that in donkeys (13.9%) and horses (10.4%). In addition, the highest percentage of positive equines was detected in samples from the tropical climate (17.5%). The identification of risk factors was assessed by bivariate logistic regression analysis. Mules had 8.608 times higher risk for F. hepatica infections as compared with horses (odds ratio (OR) 8.608; 95% confidence interval (CI): 2.809-26.377), while the OR for 6-10-year-old equines was 93.375 compared with that of young equines (≤ 5 years old) (OR 93.375; 95% CI: 11.075-787.239). Likewise, tropical climate equines had 83.7% increased odds for fasciolosis (OR 1.83).

Equines as reservoirs of human fascioliasis: transmission capacity, epidemiology and pathogenicity in Fasciola hepatica-infected mules

Fascioliasis is a zoonotic disease caused by liver flukes transmitted by freshwater lymnaeid snails. Donkey and horse reservoir roles have been highlighted in human endemic areas. Liver fluke infection in mules has received very limited research. Their role in disease transmission, epidemiological importance and Fasciola hepatica pathogenicity are studied for the first time. Prevalence was 39.5% in 81 mules from Aconcagua, and 24.4% in 127 from Uspallata, in high-altitude areas of Mendoza province, Argentina. A mean amount of 101,242 eggs/mule/day is estimated. Lymnaeids from Uspallata proved to belong to ribosomal DNA internal transcribed spacer (ITS) markers ITS-1 and ITS-2 combined haplotype 3C of Galba truncatula. These lymnaeids were experimentally susceptible to infection by egg miracidia from mules. Infectivity, number of cercariae/snail and shedding period fit the enhanced F. hepatica/G. truncatula transmission pattern at very high altitude. This indicates that the mule is able to maintain the F. hepatica cycle independently. Individual burdens of 20 and 97 flukes were found. Mule infection susceptibility is intermediate between donkey and horse, although closer to the latter. Anatomo-pathology and histopathology indicate that massive infection may cause mule death. Haematological value decreases of red blood cells, haemoglobin, leucocytes and lymphocytes indicate anaemia and strong immunosuppression. Strongly increased biochemical marker values indicate liver function alterations. The mule probably played a role in the past exchanges with Chile and Bolivia through Mendoza province. Evidence suggests that mules could contribute to the spread of both F. hepatica and G. truncatula to human fascioliasis-endemic areas in these countries.

Copro-prevalence of Fasciola hepatica in Chilean breed horses in the province of Concepción, Chile

The aim of this research was to assess the copro-prevalence of Fasciola hepatica in owned Chilean breed horses (Equus caballus) residing in the province of Concepción, Chile. The study was carried out throughout October 2017. Samples were taken from all (100%) Chilean breed horse (124 specimens; 45 females and 79 males, aged between 7 months and 24 years old) from the Concepción province. A rectal stool sample was obtained from each animal. This was analyzed using the Army Medical School method (AMS III) technique to detect F. hepatica eggs. Information about the horse's age, sex, previous fasciolicide application, and an assessment of body condition was also obtained. Fisher tests were carried out to analyze the results. Ten horses (8.06%) were positive for the presence of F. hepatica eggs. No significant difference of copro-prevalence was found between age (young 8.47%, old 7.69%), sex (female 11.1%, male 6.33%), the previous application of fasciolicide (dewormed 10%, not dewormed 7.89%), or body condition (low condition 11.1%, high condition 0.7%) categories (Fisher tests: P>0.05 in all cases). The results of this study suggest that Chilean breed horses constitute part of the reservoir of F. hepatica for both ruminant populations and humans in the Concepción province.

Horses are susceptible to natural, but resistant to experimental, infection with the liver fluke, Fasciola hepatica

Fasciola hepatica is a common parasite of livestock in Ireland, causing significant economic losses and affecting animal welfare. A previous abattoir study of 200 horses led to an estimated 9.5 % prevalence of infection in horses slaughtered in Ireland. However, the epidemiology and pathogenic significance of this infection in this species is not well-described. The objectives of this study were to determine the susceptibility of horses to oral challenge infection with F. hepatica metacercariae, and to document the course of the infection along with serological and biochemical response. We attempted an experimental infection of horses (n = 10; 9 geldings and 1 mare) with F. hepatica. Four were given 1000 metacercariae, four 500 metacercariae and two were sham-infected. Blood and faecal samples were taken at intervals up to 18 weeks post-infection (wpi). ELISA assays were used to assess sero-conversion in the experimental horses and also in a panel of sera from horses of known fluke status. No flukes were recovered from any of the livers, and neither were any lesions that could be attributed to F. hepatica infection observed. Coproantigen ELISA was negative throughout for all horses. Three antibody detection ELISAs, useful in diagnosing fasciolosis in other species, had limitations as diagnostic aids as determined using a panel of sera from horses of known F. hepatica infection status. This study is limited by the relatively small number of animals included, and the relatively short duration of the study period. Failure to establish infection after oral challenge raises fundamental questions on the pathophysiology and epidemiology of equine fasciolosis.

Liver fluke in Irish sheep: prevalence and associations with management practices and co-infection with rumen fluke

BACKGROUND

The present study aimed to identify the national prevalence of Fasciola hepatica in Irish sheep and to conduct a risk analysis assessment based on management and treatment practices in participating flocks. Also, co-infection with rumen fluke was quantified and its association with liver fluke and management practices was assessed.

METHODS

A total of 305 sheep flocks were selected ensuring even national representation of the sheep population. Participating farms were asked to complete a survey questionnaire on farm management practices and submit faecal samples during the winter of 2014-2015. Pooled faecal samples were analysed for the presence of F. hepatica and co-infection with rumen fluke. Apparent and true prevalence were calculated, additionally, the rate of co-infection with rumen fluke was also obtained. Correlation and regression analyses were used for assessing associations between management practices, liver fluke infection and co-infection with rumen fluke.

RESULTS

The national true prevalence of F. hepatica was 50.4% (n = 305). Regional prevalence varied from 41% in the east to 52% in the south. Co-infection with rumen fluke was observed in 40% of the studied population and correlated with increased F. hepatica egg counts (OR = 2.9; P ≤ 0.001). Predominant breeds were Suffolk, Texel and Horned Mountain breeds. Beef cattle were the most frequent type of other livestock present on farms and mixed species grazing was frequently reported (73%). More than half of the flocks reported a mid-to-late lambing period (March-April). Use of mountain land for grazing was of 32%. Flukicides were most commonly used twice over the autumn-winter period. Regression analyses highlighted significant association of F. hepatica status, with the presence of other livestock on farm, frequency of flukicides used during the winter and clinical presentation of liver fluke. A significant increase in eggs per gram of faeces was observed in Charollais sheep in comparison with all other breeds. Co-infection with F. hepatica and Calicophoron daubneyi was also significantly associated with the presence of other livestock on the farm, type of flukicide used and clinical fasciolosis.

CONCLUSIONS

The present study provides up-to-date information on the prevalence of F. hepatica in Irish sheep and adds insight to the epidemiology of the disease. These findings will be useful for designing new holistic control measures for F. hepatica infection.

Fasciola hepatica in UK horses

Background

Fasciola hepatica (liver fluke) affects grazing animals including horses but the extent to which it affects UK horses is unknown.

Objectives

To define how liver fluke affects the UK horse population.

Study design

Descriptive, cross‐sectional, observational study.

Methods

An F. hepatica excretory‐secretory antibody detection ELISA with a diagnostic sensitivity of 71% and specificity of 97% was validated and used to analyse serum samples. An abattoir study was performed to determine prevalence. A case‐control study of 269 horses compared fluke exposure between horses with liver disease and controls. Data on clinical signs and blood test results were collected for sero‐positive horses. Genotyping of adult fluke was used to produce a multilocus genotype for each parasite.

Results

Four (2.2%) of 183 horses registered in the UK, sampled in the abattoir, had adult flukes in the liver, and the sero‐prevalence of F. hepatica was estimated as 8.7%. In the case‐control study, horses showing signs consistent with liver disease had significantly higher odds of testing positive for F. hepatica on ELISA than control horses. In 23 sero‐positive horses, a range of non‐specific clinical signs and blood test abnormalities was reported, with a third of the horses showing no signs. Genotypic analysis of liver flukes from horses provided evidence that these came from the same population as flukes from sheep and cattle.

Main limitations

Bias could have arisen in the prevalence and case‐control studies due to convenience sampling methods, in particular the geographic origin of the horses. Only a small number of horses tested positive so the data on clinical signs are limited.

Conclusions

Exposure to liver fluke occurs frequently in horses and may be an under‐recognised cause of liver disease. Flukes isolated from horses are from the same population as those found in ruminants. When designing and implementing parasite control plans, fluke should be considered, and horses should be tested if appropriate.

Prevalence of fasciolosis in livestock and humans: A systematic review and meta-analysis in Iran

Fasciolosis is a re-emerging disease of livestock and rarely human, being endemic in Iran. Herein, we aimed to quantitatively assess the human seropositivity and prevalence of animal fasciolosis in our country. English and Persian databases were searched for online literature. In total, 10 human seroprevalence studies and 49 animal investigations were obtained from January 1999 to March 2019. Only animal studies were included in meta-analysis. The highest human seroprevalence was detected in Guilan province (326/452; 50%). The pooled prevalence of the animal infections was calculated as 6.2% (95% CI = 5.8%-6.5%). In detail, the prevalence ranges in three hosts included as 4.2% (95% CI = 3.8%-4.5%) in sheep, 9% (95% CI = 8.0%-9.9%) in cattle and 3.1% (95% CI = 2.4%-3.7%) in goat. The highest prevalence rate was observed in the north, 11.8% (95% CI = 8.4%-15.1%), while the lowest prevalence was detected in the central Iran with 1.8% (95% CI = 1.3%-2.3%). Egger's regression test revealed no significant publication bias (P = 0.307). Also, there was no remarkable correlation between weighted prevalence and sample size (P = 0.249) as well as year of study (P = 0.172). These findings would be necessary for better preventive strategies in case of human and animal Fasciola infections as well as snail intermediate hosts.

Questionnaire survey on helminth control practices in horse farms in Ireland

Knowledge regarding helminth control strategies and nematode infection of horses in Ireland is limited and only one study has been published recently. This present study was designed to investigate the current helminth control strategies followed by horse owners in Ireland. A questionnaire was formulated to collect data on general grazing, pasture management and deworming strategies including the use of fecal egg counts. Questionnaires were emailed to 700 members of the Irish Thoroughbred Breeders Association and Horse Sport Ireland. Only 78 questionnaires were returned. Respondents indicated that horses are grazed for 16-24 h day-1 during the summer and autumn (89% and 65%, respectively). Removing feces from the pasture was implemented by 37.6% of respondents. Few (22.2%) owners kept horses off pasture after worming. Overall, ivermectin and moxidectin were the most commonly administered anthelmintics in 2014 by 75% and 62% of respondents, respectively. Benzimidazole and pyrantel drugs were used by 53% and 35% of respondents, respectively. The majority of farms (81.4%) treated horses 4-5 times per year and 74.2% only estimated the weight of the horses visually. The findings of this study illustrates that many stud managers/owners do not follow best practice with regard to helminth control and more education is needed.