Hi All,
Welcome to topic 5 for 624EHS - Contemporary Issues in Equine Science.
This topic is all about parasite control practices. Make sure that you look at the launch PowerPoint, which has been posted in the Classroom. You are required to contribute to this blog as part of their CW3 assessment. All students have from now until 5 pm on Friday 25th of March 2022 to contribute to this blog, to debate the issues surrounding parasite control practices within the equine sector. Ensure you can also evidence your opinions and remember that you are also required to submit a reference list (word document emailed to module leader) by 5 pm on Friday 25th of March 2022. You will be graded on the quality and quantity of both your blog contributions and your reference list. Remember, the point of this is to debate the issues, so you should be replying to each other's posts. I will be keeping an eye on the blog, but if you have any issues, you should email me. Please remember to register your name with your comments so that I know who has contributed with which comment.
Rosa
Parasite control in the equine population is everywhere within the Uk and is important to maintain the condition of the horse. Traditionally, blanket worming was implemented - this refers to worming horses frequently and regularly with anthelmintics. Traditional worming normally consists of controlling equine parasites to identify one or two species of importance (Strongyles, roundworms, bots, pinworms, and tapeworms etc.) and implementing strategies to target this within animals (Drudge et al.,1966). However the recent increase in parasite resistance to “blanket” worming has resulted in the equine industry having to determine new practices to limit a further increase (Nielsen, 2012)
ReplyDeleteJasmine pook
Moreover, Traditional methods for controlling parasites should be reconsidered, for example worming and rotating wormers based on active ingredients in the wormer. The trends within equine control appear to be constantly changing and evolving. New parasite control strategies perhaps focus on one parasite problem at a time as there is a risk of invoking another problem and always seems to threaten equine health.
DeleteJasmine pook
KAYA: Jaz makes a good point, the traditional approach to de-worming; “blanket worming” has indeed gained much scrutiny in recent years due to rising resistance, with very little if any scientific evidence to support it (Austin 2017). This is compounded by the alternative possibilities there are in de-worming approaches. Yet somehow, the blanket method remains the most common method of endoparasite control in the UK and much of the world. There are many reasons for this, but in the UK particularly, many believe in the traditions surrounding equine care for the sake of tradition itself, thus it is very difficult to persuade those of the more modern approaches even if the evidence suggests they are more effective (Leathwick 2019).
DeleteTo further Jaz's second point, rotation has been shown to be effective, however resistance for all three effective drug groups (benzimidazoles, macrolides, pyrantels) exists. Additionally, having largely relied on a very limited number of different anthelmintic compounds to control helminths, anthelmintic resistance appears to be established in all pathogenic species, aswell. So the longevity of rotational wormings effectiveness may be an issue (van Dijk 2021)
Delete(Apologies, the above comment that ended with “Leathwick 2019” was meant to end with “Becher et al 2018” - got my references mixed and I cant go back and edit/delete comments)
DeleteTo elaborate further on Kaya's comment. Martins et al., (2009) conducted a survey to determine the control and management practices of equine helminths infection within brazil. 29 farms were included in the study and were interviewed about management practices on the farm, moreover faecal samples where collected from mares and analysed via EPG technique, faecal culture. The prevalence of helminths in the mares were calculated, Stocking rates of pastures, change of horse bedding, absence of pasture rotation, lack of technology, less frequent treatment of animals were associated with greater worm burdens, demonstrating that these variables must be considered in equine control groups.
DeleteJasmine pook
Despite increasing awareness within the veterinary and equine industry of the potential implications of anthelmintic resistance (AHR) there is a concern that insufficient measures are being done to reduce the development and spread of parasites. Rendle et al., (2019) conducted a study implementing a two round Delphi process suggested that documents should be commissioned to provide veterinary surgeons with current information on worm control, which will prevent clinical disease and minimise selection pressure for resistance. However, it is important to consider that the research utilised published and unpublished data, it would be beneficial to consider as to why some research was not published, perhaps there was a lack of funding, lack of peer reviewed journals or perhaps there could be flaws within the research. However, Rendle et al., (2019) stated that where research was conflicted or absent, expert opinions, based on the experience of the group were applied, but, it is important to consider that there could potentially be bias. Majority of the papers focused on donkeys and problems facing parasite burdens within the animals, for example there are ten species of small strongyles that are specific to donkeys (Zarkari et al.,2015). Roundworm parascaris equorum is associated with horse foals, then adults develop immunity. However, this is not the case in donkeys and they continue to be susceptible into adult life. It is important to consider donkey's in regards to AHR and further research is required to determine specific recommendations for preventing further resistance.
ReplyDeleteJasmine pook
It is of the utmost importance that equine professionals, particularly veterinary practises, are aware of their role to implement sustainable parasite control strategies, yet engagement with practice-led targeted worming plans remains poor and many owners still administer anthelmintics in a haphazard manner. It is concerning that some believe not enough is being done within the veterinary industry to reduce the development and spread of parasites. Aside from the possibility of reducing anthelmintic resistance in previous research by Rendle, Rendle 2018 found that veterinary practices which implement worming plans, can do so to their advantage. Many have seen benefits from increased anthelmintic and laboratory test sales, improved uptake of other packaged services and greater client engagement with the practice. Veterinary practices should be in a position to offer better services to their clients than any other provider, if they have the motivation to do so.
DeleteAnthelmintic resistance is a global threat to food security. One theory in alleviating the selection pressure for resistance thus maintaining drug efficacy, is the concept of “refugia” (Hiney and Giedt 2021). Refugia refers to preserving a proportion of the parasite population unexposed to treatment (Leathwick, Sauermann, and Nielsen 2019). While persuasive in its logic, it is currently widely advocated as best practice. However evidence for its ability to slow the development of drug resistance in parasitic helminths is limited.
ReplyDeleteHodgkinson et al 2019 reviewed the conditions needed for refugia to work and examined the assumptions surrounding refugia and its application in different situations. They found that the factors potentially most important to refugia success is the intensity of drug resistance within the population, the degree of mixing between parasite sub-populations and lastly the parasites life history; genetics and environment in the population's resistance vary. Therefore, to generate a successful population of refugia highly depends on the deworming system already in place. Additional research is needed on the concept of refugia and the underlying principles for its application across systems, as well as empirical studies within systems that prove and optimise its usefulness (Hodgkinson et al 2019).
In comparison, to blanekt worming, a study conducted by Stratford et al., (2014) investigated gastrointestinal parasite control methods in Scotland. Anthelmintic resistance in equine gastrointestinal nematodes is a threat to health and welfare. It is important to determine parasite control methods to determine potential risk factors for resistance. Stratford et a;., (2014) implemented a questionnaire to identify parasite control practices within horse owners in Scotland and investigate management factors associated with resistance. At 193 responses suggested that Moxidectin and Ivermectin or a related combination products were the most commonly administered anthelmintics in the next 12 months. Treatment licensed against cyathostomin encysted larvae and tapeworms were administered by 80% and 90% of respondents. This was achieved through “blanket” worming using Moxidectin and Ivermectin, whereas, 62% of owners implemented Faecal egg counts (FEC) and this inturn reduced annual administration of anthelmintic frequency. Vets had the greatest influence on management practices, with 40% stating that they believed practised targeted dosing, this was not associated with delaying treatment beyond the egg reappearance period of the anthelmintic used. Stratford et al., (2014) concluded that increasing veterinary involvement and FECs would be beneficial to reduce resistance. The majority of responcents administered anthelmintics licensed against cyathostomin encysted larvae and tapeworm. Despite this, responses demonstrated that owners did not understand “targeted” dosing regimens.
ReplyDeleteJasmine pook
Mixed grazing is assumed to reduce strongyle load on the pasture as the result of a dilution effect. The dilution effect refers to reduced pasture contamination: parasites and their hosts having evolved together, so the parasites adapted to the equine digestive system cannot survive in a ruminant digestive system and vice versa. So when these animals are housed together they consume a proportion of each other's parasites, killing them thus naturally keeping parasite burdens at bay for each other. This has been shown in small ruminants such as sheep and goats grazing with horses, but the putative benefits of co-grazing between horses and cattle have not yet been evaluated. Forteau et al 2020 went about correcting this, by conducting field surveys and face-to-face interviews on 44 farms in Normandy and northern Massif Central, to compare worming management practices between specialised systems and mixed horse-cattle systems. Every breeder relied on systematic calendar treatments, and only 8 out of the 23 mixed breeders were aware that co-grazing of horses with cattle could be used as part of their strongyle control strategy. Forteau et al 2020 discovered that practices were similar across both systems in Normandy, but in Massif Central, deworming was less frequent and stocking density was higher on mixed farms, while specialised breeders seemed more willing to integrate herd and plot management into control strategies. Interestingly, faecal egg counts from Massif Central were significantly reduced when horses were grazed with cattle. They found that young horses grazed with cattle had 50% fewer strongyle eggs excreted in their faeces than horses grazed in equine-only pastures (P < 0.01). This is the first evidence of the benefits of mixed grazing with cattle as an alternative to control strongyle infection in horses (Forteau et al 2020).
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DeleteUnfortunately, this seemingly promising alternative appears largely unknown by horse farmers, or perhaps is just unpopular (Halvarsson, Gustafsson and Höglund 2022). This may be due to farms being more specialised now, perhaps not many equine farmers are interested in also farming cattle or other ruminants. An issue that maybe could be combated by instead advertising the idea of additional livestock primarily as a natural and effective way to combat parasite burdens, rather than entering into a new type of farming. As long as those additional animals are financially ‘breaking even’ by either being sold into the food chain or some other form of ‘earning their keep’ then this method is not only cheap and effective in terms of combating resistance, but perhaps even carries the potential to earn the farmers extra money.
DeleteFuture research may aid equine keepers by determining the ideal grazing companion for horses; sheep, cows, goats ect and what the ideal number of said animal is per horse. For example, does is have to be a 1:1 ratio of horse to ruminant or would 1:2 or maybe even 1:5 may still be effective? For those not particularly interested in farming additional animals, but wanting to experiment with mixed grazing for the potential parasitic benefits may feel comfort in knowing the minimum number of additional animals they need for this practise to be viable.
I failed to mention that mixed grazing is a type of pasture management. Faecal removal is another method of reducing larval burdens in pastures, under the pasture management category. Similarly to mixed grazing, there appears to be a lack of knowledge or inclination, surrounding “poo-picking'', even though many consider it a basic part of pasture management (Cameron 2020). In Papini, De Bernart, and Sgorbini 2015 study, many facilities do not appear to perform poo-picking. Removing faeces from pastures is time consuming and requires special equipment (tractor, manure spreader, and front-end loader), on the other hand it is often performed manually but this may be unrealistic depending on work force and size of farm. Some equid keepers may argue that with rotational and/or mixed grazing, faecal removal is unnecessary. It’s possible that some of the farms involved did not have enough acreage to perform rotational and/or mixed grazing, but if anything this should increase the number of those poo-picking, not decrease. Papini, De Bernart, and Sgorbini 2015 suggested that the low proportion of those removing manure at least once a week means many facilities likely have low hygiene standards. Papini, De Bernart, and Sgorbini 2015 reported percentages for pasture rotation, mixed grazing, and faecal removal were 67.9%–80%, 6%–39.3% and 32%–89.3% in South Africa, Brazil, or Ireland, with 6% of Swedish establishments removing manure weekly and 49% picking up faeces once, twice, or daily each week in the UK. These numbers are concerning when considering how basic an action it is for the benefits it provides.
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DeleteAnother type of pasture management that will reduce parasitic infestation, is pasture rotation. Grazing is how horses contract parasites by ingesting free-living infective larvae from pastures. Grazing horses are less likely to be exposed to risk of infection and clinical disease through pasture rotation, that is, moving them to a “clean” pasture periodically (Papini, De Bernart, and Sgorbini, 2015). This allows the larvae a chance to die-off before they can infect other horses, whilst also allowing the grass to regrow while horses graze elsewhere (Rapiya et al 2019). However this is highly dependent on climate and several other factors (Papini, De Bernart, and Sgorbini, 2015). Its effects are comparable to mixed grazing, which reduces pasture contamination by ruminants ingesting larvae of horse worms, breaking the life cycle but rotational grazing breaks the life cycle by killing off the worms by removing host animals altogether.
DeleteDue to increasing reports of multidrug resistance, faecal egg counts (FEC) have become an essential tool for determining which treatment is most appropriate, by deciphering the type and intensity of infestation. FEC also allows targeted anthelmintic programs. In well-managed adult (older than three years old) herds exposed to low to moderate levels of pasture contamination, FEC egg distribution shows a negative binomial pattern: an overdispersion of eggs from certain members of the herd. This is referred to as the “80:20 rule” whereby under normal control conditions, 80% of the parasite eggs are excreted by 20% of the animals in the herd, with the other 80% of the herd showing low (20% or less) or even negative counts. With effective pasture and anthelmintic control conditions, the proportion of high shedders is often well below 20% (Rendle et al 2019). Testing within this regime is conducted at 8 to 12-week intervals, with an adulticidal anthelmintic only administered to the “high shedders” of the herd, saving the other 80% from drug administration, therefore lessening the chances of resistance building. This will reduce overall egg output and the infective pasture larval burden (Hallowell-Evans and Hallowell 2017). This is a highly recommended procedure for adult herds, but unfortunately in youngstock, pasture management strategies such as these must be employed with caution as strongyle egg output does not adhere to the 80:20 rule outside of adult herds (Rendle et al 2019). Additionally, the increased risk of clinical disease and complication that comes from ascarid burdens at a young age, means targeted regimes such as these are not advised (Hallowell-Evans and Hallowell 2017).
ReplyDeleteOne great benefit of pasture management parasite control, is that these practices reap compacted benefits when used together. It would be incredibly interesting to see the combined results of pasture rotation (Rapiya et al 2019), mixed grazing (Forteau et al 2020) and thorough weekly faecal removal (Cameron 2020) used together. Taking FEC counts throughout the year, accounting for the natural spikes in parasite counts in certain seasons and comparing them to a year of combined good pasture management techniques. Then there are the concepts of refugia (Hodgkinson et al 2019) and the 80:20 rule (Rendle et al 2019), which although not entirely natural as they still involve anthelmintics and FECs, they are arguably a more natural way of fighting resistance compared to non targeted worming practises, like blanket worming. If good pasture management was implicated alongside a targeted anthelmintics regime, such as the 80/20 rule with frequent FECs, from the research collected thus far I predict the herd would experience a significant drop in endoparasites thus use far fewer worming drugs and within 5 years, a noticeable if not significant drop in resistance within the herd. Obviously, as long as any newcomers undergo a period of quarantine and any changes within members of the groups, such as low shedders becoming high shedders is kept track of and handled correctly.
ReplyDeleteThese practices are obviously not applicable to all herds and farms, such as youngstock (Hallowell-Evans and Hallowell 2017) etc but it would be incredibly interesting to see the results of combining these more natural methods. It may sound like a nice ideal but unrealistic, but it would actually be quite simple to implicate and there is likely to be additional benefits such as increased hygiene (Cameron 2020), better grass quality (Rapiya et al 2019) and/or adding a secondary financial avenue by adding a small amount of secondary livestock to the farm. The first year may appear to require more financial investment and effort, but in reality FECs are a similar price to wormers, so for those worming every 8-12 weeks financially it would be comparable as farmers only need to obtain 20% of the anthelmintics they would usually buy and once effects have taken place, if would certainly be much cheaper as owners would be buying even fewer drugs and diseases associated with heavy worm burdens, such as colic would likely be eliminated.
DeleteIn contrast to Kaya's comment, Most vets continue to administer worming routines based on evidence and practices determined 40 years ago. However, much has changed since the practices were first introduced and current practices routinely fail to provide optimal parasite control, this could be due to several factors. Recent literature demonstrates that anthelmintic resistance in parasites is highly prevalent and multiple drug resistance is common in some countries but few vets take this into account when making treatment decisions/ rotating wormers. Furthermore, current practices such as treating all horses at frequent intervals were designed to control large strongyle, Strongylus vulgaris. But this parasite is now quite uncommon in managed horses in most of the world. Common practices of treating horses with the same worm treatment despite varying burdens is outdated and potentially increases resistance, moreover, administering treatment to all horses without indication of parasitic problems or not knowing the species of the parasites infecting the horse, recommending drugs without knowledge of efficacy and failing to perform diagnostic techniques are all incompatible with current veterinary practices/ Because of this, attitudes and approaches to parasite control needs to completely change, this, could be achieved by following an evidence based approach (Kaplan and Nielsen et al., (2010).
Deletejasmine Pook
Example worming plan - (Kaplan and Nielsen et al., (2010).
ReplyDeleteCategory
Frequency of deworming per year
Light shedder
2 x per year (or no treatment at all)
(late autumn after the first frost and spring)
Moderate shedder
3 to 5 times a year
(late autumn after the first frost and spring, sometimes in summer, especially in warmer environments)
Heavy shedder
5-6 times per year (approximately every other month) Intensive treatment required all through the main seasons of transmission
jasmine pook