parasite

Equine Cyathostominae can develop to infective third-stage larvae on straw bedding

Citation

Sandy Love, Faith A. Burden, Eoghan McGirr, Louise Gordon, Matthew Denwood. August 2016. Equine Cyathostominae can develop to infective third-stage larvae on straw bedding. Parasites and Vectors.

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Publication details
Publication date: 
31 August 2016
DOI number: 
10.1186/s13071-016-1757-1
Abstract

Background
Domesticated grazing animals including horses and donkeys are frequently housed using deep litter bedding systems, where it is commonly presumed that there is no risk of infection from the nematodes that are associated with grazing at pasture. We use two different approaches to test whether equids could become infected with cyathostomines from the ingestion of deep litter straw bedding.

Methods
Two herbage plot studies were performed in horticultural incubators set up to simulate three straw bedding scenarios and one grass turf positive control. Faeces were placed on 16 plots, and larval recoveries performed on samples of straw/grass substrate over 2- to 3-week periods. Within each incubator, a thermostat was set to maintain an environmental temperature of approximately 10 °C to 20 °C. To provide further validation, 24 samples of straw bedding were collected over an 8-week period from six barns in which a large number of donkeys were housed in a deep litter straw bedding system. These samples were collected from the superficial bedding at 16 sites along a “W” route through each barn.

Results
No infective larvae were recovered from any of the plots containing dry straw. However, infective cyathostomine larvae were first detected on day 8 from plots containing moist straw. In the straw bedding study, cyathostomine larvae were detected in 18 of the 24 samples. Additionally, in the two barns which were sampled serially, the level of larval infectivity generally increased from week to week, except when the straw bedding was removed and replaced.

Conclusions
We have demonstrated that equine cyathostomines can develop to infective larvae on moist straw bedding. It is therefore possible for a horse or donkey bedded in deep litter straw to become infected by ingesting the contaminated straw. This has implications for parasite control in stabled equids and potentially in housed ruminants, and further investigation is required in order to establish the relative infective pressure from pasture versus straw bedding.

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Papaya latex supernatant has a potent effect on the free-living stages of equid cyathostomins in vitro

Citation

Laura Peachey, Gina L. Pinchbeck, Jacqui. B. Matthews, Faith A. Burden, J.M. Behnke, Jane Hodgkinson. August 2016. Papaya latex supernatant has a potent effect on the free-living stages of equid cyathostomins in vitro. Veterinary Parasitology.

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Publication date: 
1 August 2016
DOI number: 
10.1016/j.vetpar.2016.07.036
Abstract

The control of equid gastrointestinal nematodes in developed countries, in particular the cyathostomins, is threatened by high levels of anthelmintic resistance. In recent years, there has been increasing interest in the evaluation of traditional ‘ethnoveterinary’ medicines as alternatives to chemical anthelmintics. The cysteine proteinases (CPs), a group of enzymes derived from fruits such as papaya (Carica papaya), pineapple (Ananas comosus) and figs (Ficus spp.), have shown good efficacy against adult stages of a range of parasitic nematodes, in vitro and in vivo. The efficacy of CPs against cyathostomins remains to be explored. In this study, the efficacy of a crude preparation of CPs, papaya latex supernatant (PLS), against the free-living stages of cyathostomins was evaluated using two in vitro tests, the egg hatch test (EHT) and the larval migration inhibition test (LMIT). It was demonstrated that PLS had a potent effect in the EHT, with EC-50 values in the range of 0.12-0.22 μM. At concentrations above 6.25 μM the eggs did not develop, below this concentration the L1 developed but they lost integrity of the cuticle upon hatching. These effects were inhibited by pre-incubation of PLS with the CP inhibitor L-trans-epoxysuccinyl-L-leucylamido-(4-guanidino butane) (E64), indicating that CPs were responsible for the anti-parasitic activity. A dose-dependent inhibition of migration of third stage larvae (L3) in the LMIT was demonstrated at higher concentrations of PLS, with EC-50 values in the range of 67.35-106.31 μM. Incubation of PLS with E64 prior to use in the LMIT did not reverse the anti-migratory effect, suggesting that CPs were not responsible for the reduced migration of cyathostomin L3 and that PLS also contains an additional active compound. This is the first report of PLS and/or CPs showing activity against the free-living stages of a parasitic helminth. In addition, it suggests that cyathostomins are highly sensitive to the effects of CPs and further evaluation of their efficacy against parasitic stages and in vivo are strongly indicated.

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Equine central nervous system trypanosomosis in The Gambia is caused by genetically diverse populations of Trypanosoma brucei parasites

Citation

Demelza Kingston, Jan Rodgers, S. Sharpe, K. Berman, Liam Morrison, P. Kennedy, B. Bradley, David Sutton. April 2016. Equine central nervous system trypanosomosis in The Gambia is caused by genetically diverse populations of Trypanosoma brucei parasites. Journal of Equine Veterinary Science. 39:Supplement. 100-101.

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Publication date: 
5 April 2016
Volume: 
39
Issue: 
Supplement
Page numbers: 
100-101
DOI number: 
10.1016/j.jevs.2016.02.214
Abstract

In many countries diseases affecting working equid performance and productivity are detrimental both to equid welfare and to local economic development. Central nervous system (CNS) trypanosomosis, caused by Trypanosoma brucei spp 1, is a severe manifestation of trypanosomosis, which is usually fatal. The causative agent of this condition in the Gambia was investigated further in this study, to determine genotypic variation, mode of transmission and future management interventions. The presence of trypanosomes in local tsetse flies (Glossina spp.) was also investigated due to suspected vector involvement in disease transmission. Working equids exhibiting signs of CNS trypanosomosis were clinically evaluated. Blood was stored in EDTA and on FTA® cards prior to DNA extraction. In advanced neurological disease where prognosis was hopeless euthanasia was performed. CSF and CNS tissue samples were collected post-mortem. CSF was stored on FTA® cards and tissue samples were collected in formalin and RNAlater®. To confirm CNS T.brucei spp infection, immunohistochemistry and T.brucei-specific PCR 2 was performed on tissue samples. DNA was also extracted from blood collected from patients with evidence of generalised T.brucei infection with normal neurological function, and from the midguts of locally caught tsetse. Parasite population structure was investigated using a panel of microsatellite markers 3 together with a reference strain of T.brucei equiperdum (OVI) and a T.b.brucei positive control.Ten cases (5 horses, 5 donkeys) with naturally occurring CNS trypanosomosis were included. Horses presented with rapidly progressive spinal ataxia while donkeys showed slowly deteriorating cerebral dysfunction and cranial nerve abnormalities. CNS trypanosomosis was confirmed post-mortem using immunohistochemistry and PCR. Histopathological evaluation revealed diffuse lymphocytic-plasmacytic meningoencephalomyelitis. Microsatellite fragment analysis showed a heterogenous parasite population with a large range of alleles present, inconsistent with a clonal population. Parasite populations from donkey versus horse, and from blood versus CNS tissue were not found to be significantly different, suggesting that host factors are important in progression of neurological disease. Of 405 tsetse trapped locally and dissected, 11 contained microscopically visible midgut trypanosome infections. DNA extracted from the positive tsetse midguts was positive for equid DNA in 3/11 cases, confirming vector involvement. 5/11 flies were positive for T.brucei but with different microsatellite patterns to that found in infected CNS tissue. Further work is required to develop an optimal panel for use in both tsetse and equine-derived samples. Continued efforts are required to improve understanding of the transmission of this disease to enable the development of effective preventative measures.

Acknowledgements

This work is funded by the Donkey Sanctuary.

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Donkeys - a unique and challenging endoparasite host

Citation

Faith A. Burden, Mulugeta Getachew. April 2016. Donkeys - a unique and challenging endoparasite host. Journal of Equine Veterinary Science. 39:Supplement. S102-S103.

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Publication details
Publication date: 
5 April 2016
Volume: 
39
Issue: 
Supplement
Page numbers: 
S102-S103
DOI number: 
10.1016/j.jevs.2016.02.216
Abstract

Endoparasites in donkeys are ubiquitous and may cause serious disease. All common helminth parasites that affect horses also infect donkeys, therefore donkeys that co-graze can act as a significant source of infection for either species. Whilst donkeys are prone to the same parasite species as horses infection characteristics and presenting signs and symptoms of disease may differ. Large strongyles and cyathostomins are common in donkeys worldwide with Strongylus vulgaris causing significant disease in donkeys with poor anthelmintic treatment history. Cyathostomins infect the majority of donkeys globally and may rarely cause cyathostominosis or colitis; however signs and symptoms of both can vary significantly from those displayed in affected horses. The significance of low level cyathostomin infection on the donkey host is unclear, many donkeys appear to thrive with high faecal egg counts (> 3000epg) and when the donkey is in general good health they may exist with high cyathostomin burdens with little impact on their overall health. The donkey is renowned as the reservoir host for the lungworm, Dictyocaulus arnfieldi. Mature horses are not permissive hosts to the full life cycle of this parasite, but develop clinical signs on infection. In contrast, donkeys are permissive hosts without displaying overt clinical signs and act as a source of infection to co-grazing horses. Donkeys are also susceptible to the flukes, Fasciola hepatica and Fasciola gigantica and may be an important reservoir host for both human and herbivore infections particularly in developing countries. Finally, Parascaris spp. infections in donkeys are common, however infection is not only associated with young, immuno-compromised animals as seen in horses. Parascaris spp. infection is a frequent finding in all age groups of donkeys. The inability of many donkeys to develop lifelong immunity to Parascaris poses problems when attempting to reduce transmission of this parasite in herds which include adult and young donkeys. Anthelmintic treatment is challenging as many anthelmintics are not licensed for use in this species; however dosing should follow best practice used in horses. Anthelmintic resistance is of particular concern in donkeys with recent reports of lack of efficacy of all anthelmintic classes in cyathostomins infecting donkeys. Control of parasites in donkeys must primarily focus on reducing the risk of infection, maintaining good health and targeting drug treatments carefully. Donkeys can be co-grazed safely with other species but careful monitoring and control should be practiced to ensure that donkeys do not act as reservoirs of infection to other, more susceptible animals. The importance of parasite infection, particularly co-infection with multiple species must be appreciated. Donkeys under stress due to malnourishment, infectious disease, overwork or neglect are at a high risk of disease related to parasite infection and consideration must be given to targeted treatments in such circumstances. Whilst the donkey remains a challenging parasite host following simple control measures and improving the overall welfare of the donkey will undoubtedly serve both the donkey and other species grazing alongside.

Online references

Common helminth infections of donkeys and their control in temperate regions

Citation

Jacqui. B. Matthews, Faith A. Burden. March 2013. Common helminth infections of donkeys and their control in temperate regions. Equine Veterinary Education.

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Publication details
Publication date: 
18 March 2013
DOI number: 
doi: 10.1111/eve.12018
Abstract

Roundworms and flatworms that affect donkeys can cause disease. All common helminth parasites that affect horses also infect donkeys, so animals that co-graze can act as a source of infection for either species. Of the gastrointestinal nematodes, those belonging to the cyathostomin (small strongyle) group are the most problematic in UK donkeys. Most grazing animals are exposed to these parasites and some animals will be infected all of their lives. Control is threatened by anthelmintic resistance: resistance to all 3 available anthelmintic classes has now been recorded in UK donkeys. The lungworm, Dictyocaulus arnfieldi, is also problematical, particularly when donkeys co-graze with horses. Mature horses are not permissive hosts to the full life cycle of this parasite, but develop clinical signs on infection. In contrast, donkeys are permissive hosts without displaying overt clinical
signs and act as a source of infection to co-grazing horses. Donkeys are also susceptible to the fluke, Fasciola hepatica. This flatworm can be transmitted, via snails and the environment, from ruminants. As with cyathostomins, anthelmintic resistance is increasing in fluke populations in the UK. A number of the anthelmintic products available for horses do not have a licence for use in donkeys, and this complicates the design of parasite control programmes. As no new equine anthelmintic classes appear to be near market, it is important that the efficacy of currently effective drugs is maintained. It is important that strategies are used that attempt to preserve anthelmintic efficacy. These strategies should be based on the concept that the proportion of worms in a population not exposed to anthelmintic at each treatment act as a source of ‘refugia’. The latter is an important factor in the rate at which resistance develops. Thus, it is imperative that parasite control programmes take into account the need to balance therapy to control helminth-associated disease with the requirement to preserve anthelmintic effectiveness.

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Field efficacy of praziquantel oral paste against naturally acquired equine cestodes in Ethiopia

Citation

Mulugeta Getachew, Giles T. Innocent, Christopher Proudman, Andrew F. Trawford, Feseha Gebreab, Stuart W. Reid, Faith A. Burden, Sandy Love. September 2012. Field efficacy of praziquantel oral paste against naturally acquired equine cestodes in Ethiopia. Parasitology Research.

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Publication details
Publication date: 
22 September 2012
DOI number: 
DOI 10.1007/s00436-012-3117-1
Abstract

The efficacy of an oral formulation of praziquantel (Equitape, Horse paste, Fort Dodge) in the reduction of cestode egg counts and serum antibody level against Anoplocephala perfoliata was assessed in 44 donkeys under field conditions. The donkeys were confirmed both by faecal examination and serum antibody assessed by an enzymelinked immunosorbent assay to have natural infection with tapeworms. The donkeys were randomly allocated into treatment (n022) and control (n022) groups. The treatment group was treated with both praziquantel and ivermectin (Ivomec, Merial) at a dose rate of 1 mg/kg and 200 μg/kg, respectively while the control group was treated only with ivermectin. Faecal samples were collected before treatment (day-0) and 2, 6, 8, 12, and 16 weeks post-treatment while blood samples were collected before treatment and 8 and 16 weeks after treatment and analysed. The results of the study demonstrated that praziquantel paste was highly effective in reducing cestode eggs in donkeys and had an efficacy of more than 99 % until week 16 (day112). No cestode egg reappearance by 16 weeks post-treatment in any animal in the treatment group was observed while donkeys in the control group continued shedding cestode eggs. The immunological assay also showed a significant reduction in serum antibody level against A. perfoliata in treated donkeys compared to the control group (p00.0001). This marked decrease in serum antibody level indicates reduced risk of cestode-associated colic and other gastrointestinal disorders and clinical diseases. No adverse reactions or clinical effects were encountered in any animal within either group throughout the trial period.

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Drug Resistant Cyathostomins in Donkey Herds; Lessons in Management for All Equids

Citation

Andrew F. Trawford, Faith A. Burden. Drug Resistant Cyathostomins in Donkey Herds; Lessons in Management for All Equids. Presented at International Conference on Equine Infectious Diseases IX. (21 October - 26 October 2012). Kentucky, USA.

Authors
Presentation details
Date presented: 
Sunday 23 October 2011
Abstract

The Donkey Sanctuary has over 2500 donkeys on its farms in the UK. Endoparasite control in these herds has been a major focus for the last 10 years. Monitoring of the herds has identified significant levels of anthelmintic resistance in the cyathostomins parasitising the donkey herds. Lack of efficacy of ivermectin, moxidectin, pyrantel and fenbendazole has been identified on multiple sites and in a number of cases treatment of donkeys harbouring such parasites is becoming increasingly challenging. Changes in management practices and approach to parasite treatment is discussed. Research to establish the extent of drug resistance and clinical significance of parasitism in donkeys is of primary concern; projects have focussed on identification of drug resistance, impacts of pasture management, validation of thresholds of faecal egg counts for treatment and alternatives to anthelmintics. Significant changes in management practices have been based upon results of these studies and new ideas and techniques are being developed. Treatment of all donkeys is carried out on the basis of a strongyle faecal egg count which is carried out on a 4-weekly basis throughout the year. Preliminary data and clinical experience has shown that increasing the FEC treatment threshold for healthy, mature donkeys to ≥ 1000 strongyle epg is sufficient to control clinical disease whilst reducing pasture contamination. Application of new treatment thresholds have reduced the reliance on chemical treatment. The mean number of anthelmintic treatments per year per animal was one in 2011; this is a significant reduction from previous dosing regimes where animals would be treated a minimum of four times per year. Animals are monitored frequently with problematic herds being 100% sampled every four weeks; such monitoring allows individualised treatment programmes and highlights reduced egg reappearance periods early. Reduced ERPs are investigated immediately with suspect animals undergoing a faecal egg count reduction test (FECRT) at the next treatment. Failed FECRTs trigger an alternative approach to treatment and further investigation. It is evident that some individual cases are becoming increasingly difficult to treat effectively; future trials of combinations of anthelmintics are being considered. Effective parasite control has also led to an increased emphasis on pasture management; dung is closely managed and carefully composted. Pasture is also rested in 6 month blocks with mixed species grazing instigated where possible. Good pasture management practices produce significant drops in pasture larval counts and is the primary mechanism used to reduce parasitism. Research and practical experience has emphasised the importance of good pasture management, treatment based upon faecal egg counts and routine assessment of efficacy of treatment. Researching and trialling higher dosing threshold has also led to significant decreases in the reliance of the organisation on anthelmintics with no recorded clinical effects. The lessons learnt from management of these large herds of donkeys may provide salient and important foundations for future equid herds that undoubtedly will experience similar problems in the future.

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