This resource has been updated as part of the veterinary review process as of December 14, 2021.
What Is The Barber Pole Worm?
Barber pole worm (Haemonchus contortus, sometimes called wireworm) is a gastrointestinal roundworm of ruminants and camelids that can cause serious disease, especially in sheep, goats, llamas, and alpacas. Adult cowsWhile "cows" can be defined to refer exclusively to female cattle, at The Open Sanctuary Project we refer to domesticated cattle of all ages and sexes as "cows." are less commonly affected by this parasite, but calves can be susceptible. While other gastrointestinal parasites can cause illness in small ruminants and camelids, barber pole worm is especially dangerous because it is a blood-sucking parasite that has the potential to cause life-threatening anemiaAnemia is a condition in which you don't have enough healthy red blood cells to carry adequate oxygen to the body's tissues.. These worms have a short life cycle and one female can produce between 5,000 and 10,000 eggs per day. Individuals can have thousands of adult worms within their stomach. Combined with the fact that each worm can consume 0.05ml of blood per day, it is obvious that severe barber pole worm infestation could have dire consequences.
The Life Cycle Of Haemonchus contortus
Barber pole worm is a strongylid parasite, and its life cycle is similar to that of other strongylids. Adult worms feed and reproduce inside the abomasum of ruminants and the third stomach compartment (C3) of camelids. Eggs released by the adult female worms are passed in the feces of the infected individual. Development of the parasite outside of the host is dependent on environmental conditions, such as the temperature and presence of moisture (described more below). When the conditions are conducive, eggs hatch inside the feces and develop into first stage larvae (L1) and then second stage larvae (L2) while remaining within the feces, which offers environmental protection to the parasite. The parasite is not able to leave the protection of the fecal pellet until it becomes a third stage larva (L3) or infective larva. The L3 moves from the feces onto grass or other pasture vegetation, where it moves up the plant in droplets of water, such as dew or rain. Sheep, goats, llamas, and alpacas then consume infective, third stage larvae while grazing. Once inside the host, infective larvae develop into fourth stage larvae (L4). The L4, which is able to suck blood, then moves into the abomasum or C3 (depending on the species of the host), where it develops into an adult, and the process begins again. The lifespan of an adult worm is typically a few months.
The ideal temperature range for barber worm development is 68-86 degrees Fahrenheit (20-30 degrees Celsius) and, under these conditions, it typically takes 7-10 days for eggs to develop into the infective L3 stage. However, these parasites can develop in temperatures ranging from 50-96 degrees Fahrenheit (10-36 degrees Celsius), with development taking longer in cooler temperatures and progressing faster in hotter temperatures, so long as they also have moisture. In hot and humid climates, development from an egg to L3 can happen in just 3-4 days. Though the parasite does not survive as well in freezing temperatures, they have been found in cold regions and have even been found under ice and snow.
The length of time that infective L3 can survive on the pasture depends on environmental factors. At this stage, the parasite cannot feed and survives off their metabolic reserves. Once those reserves are used up, they will die. L3 usually survive about six months in temperate weather, but there have been instances of the parasite living longer than this. In hot weather, L3 typically survive 2-3 months on the pasture, though exposure to sunlight will kill them faster.
Larval migration on the pasture depends on the temperature, humidity, and moisture level of the soil. L3 can travel about 4-6 inches up vegetation, so long as there is moisture to do so and the temperature is not too hot. In very hot temperatures, the L3 will stay lower on the grass where they are protected from the sun and heat.
During colder weather, the parasite (both those outside the host as well those already inside them) undergo hypobiosis, a state of arrested development. This delays the progression to adulthood and delays egg production. During this time, a fecal egg count will not be reflective of how many worms are actually inside the host. When the weather starts getting warmer, larvae will resume development and egg production will continue.
Barber Pole Worm Infections
Within every herd or flock that is exposed to barber pole worm there will be some individuals who carry heavier parasite loads than others. Additionally, not every individual who has this parasitic infection will show clinical signs of disease (the term haemonchosis describes clinical illness caused by barber pole worm infections), and different individuals will be able to tolerate different parasite loads.
Host Immunity
The term “resistance” is used in a few different ways when talking about barber pole worm. In this section we will discuss what it means when the term is used to describe sheep, goats, llamas, or alpacas. Later in this resource we will talk about what it means when used to describe the parasite population. Here, it refers to a strong immune response to barber pole worm infections and is used to describe an individual, breed, or species that tends to carry lower worm burdens than others when exposed to the same number of parasites (this can be assessed through fecal egg counts). It’s important to note that this resistance is never complete, and various factors, such as heavy exposure or stress, can overwhelm an individual’s immune response. Immunity also does not prevent infection, but rather limits the number of worms an individual carries and also reduces the chances of successful reproduction of the worms (resulting in lower fecal egg counts and less contamination of pastures).
Overall, sheep tend to develop a stronger immune response to barber pole worms than goats, possibly because sheep are natural grazers, whereas goats are browsers by nature and thus their food supply is elevated away from the parasites. If allowed to browse, goats would be exposed to far fewer of these parasites than sheep, so they may not have developed the same type of immune response as sheep, leaving them more vulnerable in settings where they have to graze on pasture for the bulk of their food. Some breeds of sheep (such as Katahdins and Black Bellied Barbados) and, to a lesser extent, goats (possibly Kikos), are believed to be more resistant to barber pole worm than others.
There is less research available regarding resistance in camelids, but studies suggest that alpacas may be more resistant to barber pole worm than sheep. A retrospective review of llamas and alpacas admitted to The University of Georgia Veterinary Teaching Hospital and Athens Diagnostic Laboratory between 2002 and 2013 found that llamas had higher rates of barber pole worm infection than alpacas, but more research is needed to determine if this is due to differences in immunity between the two species or the result of other factors.
In addition to the species and breeds that may be more resistant to barber pole worm infections, other factors contribute to the immune response of an individual. Individuals develop some degree of immunity as they age; this is more pronounced in sheep than in goats. Therefore, very young residents will be more vulnerable than mature residents. Elderly individuals are also more susceptible due to waning immune system function. Individuals in late pregnancy or who have recently given birth are also more susceptible to infection and will also be more likely to shed eggs. Additional factors that can result in increased susceptibility include poor nutrition, a weakened immune system due to stress or illness, and being exposed to barber pole worm for the first time.
Signs Of Haemonchosis
In addition to anemia, which manifests as pale mucous membranes, barber pole worm infections can also cause bottle jaw (fluid-build up under the jaw), inappetence, lethargy, weakness, and weight loss. Diarrhea is not associated with barber pole worm. However, it is not uncommon for individuals to harbor multiple different gastrointestinal parasites at once, so an individual could have haemonchosis as well as another parasitic infection that causes diarrhea.
Anthelmintic Resistance
Anthelmintics, or dewormers, are drugs that kill or remove parasitic worms. In this section we will talk about resistance when used to describe a worm population rather than the host. Dr. Kaplan, Professor of Veterinary Parasitology at University of Georgia, describes resistance as “a heritable genetic change (meaning it is passed genetically directly from a worm to its offspring) in a population of worms that enables some individual worms to survive drug treatments that are generally effective against the same species or worm and stage of infection at the same drug dose rate.” In simpler terms, anthelmintic resistance means that a worm is able to survive despite being exposed to a dose of dewormer that should have killed or removed it. Preventing parasites from developing resistance to dewormers is not possible – it is a natural evolutionary process. However, certain practices will increase the rate at which this resistance develops, while other practices will slow this rate.
Over the years, dewormingThe act of medicating an animal to reduce or eliminate internal parasites, either prophylactically or in response to illness. recommendations, especially for small ruminants, have evolved in response to the growing issue of anthelmintic-resistant parasites. Anthelmintic-resistant barber pole worms are an issue in sheep, goats, llamas, and alpacas around the world, though the degree of resistance and to which drugs worms are resistant will vary region by region and also property to property.
A History Of Overuse
There was a time when it was standard practice to rely much more heavily on deworming medications and to use them prophylactically (preventatively). At the time, the thinking was to eliminate as many worms as possible, regardless of whether or not an individual was showing clinical signs of parasitism. Strategies that were once widely recognized as good practice but are no longer recommended because they led to overuse of dewormers include:
- Deworming an entire flock or herd
- Deworming at specific times each year
- Deworming a group before moving them to a new pasture
- Deworming based on a fecal egg count alone (more on this below)
These practices accelerated the rate that parasites, especially barber pole worm, developed resistance to dewormers. Through random genetic mutation, there will always be some worms within a species that are not susceptible to a certain drug, without ever having been exposed to the drug before. However, these mutations are rare and occur in very low numbers compared to the rest of the worm population that does not have this mutation and is susceptible. When a worm population is exposed to a dewormer, worms with a mutation that allows them to withstand the treatment will have an advantage, while those without the mutation will be killed. Every time this occurs, the ratio of resistant to susceptible parasites increases, resulting in an increased chance of two resistant worms mating with each other and passing along this drug resistance to the next generation of worms (more on this when we discuss refugia).
Unfortunately, without using diagnostic tools (discussed below) to assess whether or not resistance is an issue on your property, this growing problem can go undetected until you have an irreversible problem on your hands.
Understanding Anthelmintic Groups
In order to fully understand anthelmintic resistance in barber pole worms, it’s important to understand that dewormers are a limited resource. If you haven’t looked into the various dewormers available, you may not realize how limited the supply actually is. While there are many products available, in the United States there are actually only three classes of anthelmintics that are used in sheep, goats, llamas, and alpacas. If a parasite develops resistance to one drug in a class, it will usually have resistance to all drugs in that class. Studies show that in the U.S. there are varying degrees of resistance to all available deworming classes though, as mentioned above, resistance will vary by location. While there are additional deworming options in other parts of the world, there is no indication that these treatments will be available in the U.S. any time soon and, even if they were to become available, developing resistance would continue to be an issue. In fact, there has already been evidence of worms becoming resistant to monepantel (Zolvix), a newer drug available in some parts of the world that belongs to a 4th class of dewormers.
Below is a breakdown of the available drug groups and deworming medications currently available for use against barber pole worm in the U.S., though for some species this would require extra-labelExtra-label use means that a drug is used in a way other than what is described on the label or package insert. If a drug is used in a different species than what it has been approved for, this is extra-label use. Other examples include using a drug to treat a different condition than it is approved for or administering it in a different way than the directions describe. Extra-label drug use can only occur within the confines of a valid veterinarian-client-patient relationship. use*:
Class 1- Benzimidazoles, which include:
- Fenbendazole (Safe-Guard, Panacur)
- Albendazole (Valbazen)
- Oxfendazole (Synthantic)
Class 2- Macrocyclic lactones, which include two sub groups:
Avermectins:
- Ivermectin (Ivomec, Noromectin)
- Eprinomectin (Eprinex)
- Doramectin (Dectomax)
Milbemycins:
- Moxidectin (Cydectin, Quest)
Class 3- Cell Depolarizers or Nicotinics, which include:
- Levamisole (Prohibit, LevaMed)
- Morantel tartrate (Rumantel)
*This slideshow, created by Susan Schoenian, Sheep and Goat Specialist at University of Maryland Extension, shows which drugs are FDA-approved for use in sheep and goats, and also provides information on extra-label use in goats and camelids (slides 7-10).
As mentioned above, resistance to one drug in a class likely means resistance to all of the drugs in that class. Drugs in the same class but in different sub-groups, such as ivermectin and moxidectin, may have different degrees of resistance initially, but worms will eventually develop resistance because of the similarities between the two drugs.
Recently published data from Dr. Kaplan’s lab at the University of Georgia that looked at anthelmintic resistance in the U.S. (primarily the Eastern U.S.) between 2011 and 2016 found that of 39 goat farmsFor-profit organizations focused on the production and sale of plant and/or animal products., 100% had resistance to benzimidazoles (class 1), 95% had resistance to ivermectin (class 2), and 41% had resistance to levamisole (class 3). The results were similar with the 58 sheep farms they looked at with 97% having resistance to benzimidazoles, 81% having resistance to ivermectin, and 21% having resistance to levamisole.
The Role Of Refugia
The term refugia refers to the portion of the parasite population that does not get exposed to a deworming treatment when it is administered. It will include eggs and larvae that are on the pasture at the time of treatment, as well as the parasites inside of any hosts who are not treated when another member of the herd or flock is dewormed. Refugia is a critical component of any parasite management plan because it acts as a reservoir for parasites that are susceptible to treatment (who would have otherwise been killed if exposed to the drug). While you may think that it’s all about numbers and that fewer worms is always better, this is not correct; it’s important to consider the percentage of resistant to susceptible parasites. If the majority of a worm population is resistant to treatment, this will result in a problem that worsens exponentially as resistant worms breed with resistant worms. However, by maintaining refugia, you “dilute the parasite pool” with susceptible worms, decreasing the chance that two worms with genes to confer anthelmintic resistance can breed. Ultimately, this slows the rate of resistance development.
Let’s look at some of the practices listed above, that were once standard but are no longer recommended, and consider their impact on refugia.
- Deworming an entire flock or herd– By deworming everyone in a group, you will eliminate nearly all of the susceptible parasites inside each host, leaving only resistant worms. This will mean that the only refugia will be the parasites that are on the pasture, which varies based on the season and weather (at some times of year, the majority of the population will be on the pasture, whereas at other times a higher percentage will be inside your residents). By deworming an entire group, especially during times when there are fewer parasites on the pasture to replace the susceptible worms killed by a treatment, you will end up with a situation where the rate of resistance increases because of the high ratio of resistant to susceptible parasites.
- Deworming a group before moving them to a new pasture (or deworming a group at the start of the grazing season before they are given access to pasture)– In addition to the impact described above regarding deworming an entire group, deworming and then immediately moving the group to a “clean” pasture that does not have parasites on it will further reduce refugia. Because your newly dewormed residents will pretty much only be carrying resistant worms, and the pasture will not have any (or very few) parasites on it, the ratio of resistant to susceptible worms will be very high, accelerating the rate at which resistance develops.
Maintaining refugia is now considered one of the most important ways to slow the development of anthelmintic resistance.
How Is Anthelmintic Resistance Assessed?
There are two main diagnostic tools used to assess anthelmintic resistance. The first is through fecal egg counts, or quantitative fecal analysis (a qualitative analysis will not give you a specific egg count and will not be useful in this case). By comparing pre- and post- deworming egg counts, you can assess the effectiveness of a deworming treatment. If the treatment results in less than a 95% reduction in eggs, the worm population is considered to have some resistance.
The second way to assess anthelmintic resistance is through a DrenchRite Assay.* Unlike fecal egg count testing, the DrenchRite assay uses a pooled sample (a sample from multiple individuals) to look for resistance in all classes of anthelmintics at once. This test can also detect resistance sooner than fecal egg counts. One major drawback is that this test is expensive.
Talk to your veterinarian about their recommendations regarding testing to assess drug resistance. Most recommendations suggest checking resistance levels every 2-3 years, but your veterinarian can make recommendations based on your region and the specifics of your sanctuary. Without diagnostic tools to evaluate anthelmintic resistance, developing resistance in parasite populations may go unnoticed until treatments are less than 50% effective and fail to produce an improvement in clinical signs.
Proper Use Of Dewormers
It’s important to view dewormers as just one part of your barber pole worm control strategy. There are certainly times that they must be used, but dewormer use should always be done thoughtfully. In addition to avoiding the practices described above that result in frequent and widespread use of dewormers, it’s imperative that you know how to use and store these drugs properly and to avoid practices that contribute to resistance. The following are important ways to slow the development of resistance:
- Use Targeted Deworming– We’ll discuss this a bit more later on in this resource, but the main point here is that rather than deworming entire groups, you should only deworm the individuals who actually need it (and we’ll talk more about how to determine who needs treatment later). Targeted deworming helps maintain refugia.
- Make Sure You Know The Proper Dose– If you care for goats, llamas, or alpacas, you’ll be using dewormers in an extra-label manner, which requires that you work with your veterinarian. Be aware that sheep and goats metabolize dewormers differently and goats may require a higher dose of dewormer than sheep. Your veterinarian will be best able to advise you on appropriate dosing information. You can find more information about drug dosing recommendations on the ACSRPC website, but this information should not take the place of veterinary involvement.
- Weigh Your Residents To Ensure Proper Dosing– Whenever possible, avoid estimating a resident’s weight and opt for actually weighing them in order to ensure that you calculate the proper dose. In fact, a scale is one of the best purchases a sanctuary can make. Underdosing of dewormers will reduce efficacy and contribute to resistance issues because partially resistant worms that would have been killed by the proper dose will survive the treatment. In general, slightly overdosing is better than underdosing, but different drugs have different safety margins (levamisole has a much lower safety margin than fenbendazole, for example). The best way to avoid over- or underdosing is to get an accurate weight on an individual before treating. Even if you think you are good at estimating weights, consider that when researchers asked 237 farmers to estimate the weights of sheep, they found that 85% would have underdosed the sheep based on their weight estimates.
- Use Oral Drenches– Using injectable dewormers speeds up resistance because they stay in the system longer. Pour-on dewormers aren’t recommended for sheep, goats, llamas, or alpacas because they are not designed for these species and may result in a sub-therapeutic dose. Deworming pastes, such as those designed for horses, are difficult to accurately measure and are easier to spit out than a properly administered oral drench.
- Administer Drenches Properly– Drenches should be administered using a drench syringe (sometimes called a dosing syringe). The drench tip will allow you to administer the dewormer in the back of the mouth and over the tongue. Administration at the front of the mouth could result in residents spitting out some or all of the medication. Additionally, when medicating young individuals with a suckle reflex, administration at the back of the mouth will prevent the esophageal groove from closing, which would result in the dewormer by-passing the rumen and going directly into the abomasum. These medications are formulated to go through the rumen, which allows them to stay in the GI tract longer. This results in higher absorption and greater efficacy.
- Be Careful When Mixing Solutions– If using a powdered drug like levamisole that needs to be mixed with water prior to use, be sure to do so carefully and follow package recommendations. Please note that levamisole has directions for a standard and concentrated solution – be sure to use the proper dose based on the solution you are using.
- Follow Direction Regarding Proper Storage– Not observing storage recommendations can reduce the efficacy of the drug and contribute to resistance.
- Pay Attention To Expiration Dates– Just as storing these medications inappropriately can affect their efficacy, using them past their expiration date can also result in using medication that is less effective. If using levamisole, be sure to pay attention to how long the mixed solution will be good for and clearly date any mixed solution.
Slowing The Development Of Anthelmintic Resistance
As explained above, there is no way to fully prevent anthelmintic resistance from developing, but there are ways to slow the process. It’s important to implement multiple strategies for managing barber pole worm rather than simply relying on dewormers. Below we will describe some of the strategies that you should consider including in your overall management program. However, not all of the strategies will work or be possible for every situation, so be sure to consider which are a good fit for your sanctuary. We recommend working with an experienced veterinarian to establish a parasite management program, taking into consideration any other problematic parasites that are common in your area. Remember, the goal is not worm eradication – attempting to eradicate barber pole worm will speed resistance for sure. Instead, focus on strategies that reduce your residents’ exposure to worms and implement screening protocols to identify individuals who require deworming.
Pasture Management
With grazing comes worms, but there are certain strategies you can implement in order to reduce your residents’ exposure, which can help prevent parasite loads that cause clinical disease. These strategies include:
- Prevent Overgrazing– Remember, while there will be exceptions, most L3 (the infective larval stage) will not travel higher than 4-6 inches up pasture vegetation. If you can rotate pastures so as to prevent residents from grazing on pasture that is 6 inches or shorter, you will reduce their exposure to infective larvae. However, you will also have to consider the nutritional value of the pasture – as the pasture matures, the nutritional value decreases. According to Dr. Whitley, Extension Specialist at Fort Valley State University, 80% of the infective larvae on a pasture will be in the first 2-3 inches of growth. Therefore, though parasites can travel higher than this, you may opt to move residents off a pasture when it reaches 3 inches rather than 6, which will still greatly reduce their exposure to barber pole worm larvae. When evaluating pasture, keep in mind that residents typically won’t graze it uniformly. They often have a preferred area (or multiple areas) where they graze more heavily and, in order to reduce exposure, you’ll want to pay attention to areas that are the shortest/ most popular. This also applies to smaller areas that aren’t really pasture spaces. If your residents have access to a small yard with patches of grass, or even just a strip of grass along a fence line, these can have high levels of larvae in them and be a source of infection.
- Avoid Overcrowding Your Residents– Having too many residents on a pasture can result in heavy parasite contamination. While you will have many factors to consider when assessing how many residents can fit in a particular space, when it comes to parasite management, a good starting point is 4-6 sheep, llamas, or alpacas per acre of pasture and 3-4 goats per acre.
- Base Pasture Rotation On The Parasite’s Life Cycle– While not possible at all sanctuaries, one strategy employed by larger agricultural operations is to only allow individuals to graze on a pasture for 1- 3 days before moving them to another pasture (3 days being based on the shortest amount of time it would take for eggs to develop into infective larvae). Then, because the larvae can live on the pasture for some time, the pasture is left to rest for a number of months based on the expected lifespan of the larvae, which varies depending on the climate (refer to the information above regarding the life cycle of the barber pole worm). If this set-up is not feasible (it would require a lot of pasture options), you could follow the 3 day recommendation (or even a little longer in cooler climates), and then wait to return them, or any other species affected by barber pole worm, to this pasture until it has reached a specific length as described above.
- Incorporate Browse Into Outdoor Spaces– This one is especially important and helpful for goats, as they are browsers (not grazers) by nature. By offering safe trees and shrubs, goats will spend less time grazing on pasture, which will limit their exposure to parasite larvae. Sheep, alpacas, and llamas will also enjoy some browse options, but goats really thrive when they have ample browsing opportunities and, given their weaker immune response to barber pole worm infections, limiting their exposure to these parasites is especially important. Keep in mind that just as you must manage your pasture, you must also manage any browse plants. Goats can easily kill plants by eating all of the foliage, so you’ll need to move them accordingly (you generally need to leave at least 20% of the foliage if you want to have any hope of the plant surviving).
- Rotate Susceptible Species With Equines Or Cows– Equines are not affected by the same gastrointestinal worms as ruminants, and while calves can be affected by barber pole worm, healthy adult cows rarely are unless pastures are heavily contaminated. By having equines or mature cows graze a pasture after a group of sheep, goats, llamas, or alpacas, they essentially “clean” the pasture by consuming infective larvae, which do not survive to adulthood and therefore do not shed eggs. If you implement this strategy, be sure to consider the life cycle of the parasite, ensuring you leave equine or cowWhile "cow" can be defined to refer exclusively to female cattle, at The Open Sanctuary Project we refer to domesticated cattle of all ages and sexes as "cows." residents on the pasture long enough for eggs to hatch and develop into the L3 stage. An alternative to rotating these species is to have mixed groups that graze together with the susceptible species.
- Cut Hay To “Clean” Pastures– If you are able to harvest hay, doing so will expose barber pole larvae to more sunlight and heat, which will speed the rate at which they die, making pastures safer sooner.
- Manure Management– Since eggs hatch and larvae develop inside fecal pellets, frequent removal of feces will greatly reduce pasture contamination. Regularly removing sheep and goat feces from pastures is not always practical given the small size of the fecal pellets and wide distribution throughout a pasture, but in smaller spaces that have limited areas of grass, regular removal of sheep and goat feces should be considered. There are pasture vacuums and manure collectors that can be used to remove feces from pastures, but we have heard mixed reviews from folks who have used them (especially regarding their ability to function in tall grass). Llamas and alpacas use communal dung piles which make feces removal a much easier process. By removing feces before larvae hatch and develop into L3, you will break the life cycle before larvae migrate onto the pasture.
- Focus On Your Most Vulnerable Residents– If you are looking at this list and thinking that there is no way you could manage this for all of your susceptible residents, consider if there are certain strategies you can implement with your most vulnerable residents. Often your most vulnerable residents will also be the residents shedding the most eggs, so focusing on limiting their exposure to larvae and being thoughtful about pasture rotation can help protect both your most vulnerable residents and also others who are susceptible (and may be exposed to high numbers of larvae from your most vulnerable residents).
Targeted Deworming
Because dewormers are a finite resource, it’s imperative that they be used strategically. But how do you know who to treat? While we don’t want to overuse these medications, we also don’t want to wait until someone is dangerously anemic before initiating treatment. In areas where barber pole worm infections are a concern, regularly evaluating each individual for signs of parasitism is an important way to identify individuals who may need to be dewormed before they are showing more severe signs of disease.
There are a variety of tools you might use to evaluate whether or not deworming is necessary, and ideally, you’ll use multiple tools in order to gather as much information as possible. We recommended working with your veterinarian to discuss which combination of tools makes the most sense at your sanctuary (and, if needed, to be trained how to properly perform them). They can also help determine how often your residents should be evaluated, which will vary depending on your location and also the season.
Below, we’ll give an overview of some of the tools a sanctuary might consider using to make deworming decisions, along with some recommendations about how to incorporate them into your overall strategy.
- FAMACHA Scoring– If you’ve researched barber pole worm at all, you’ve likely come across FAMACHA. This tool helps identify individuals who may be anemic from barber pole worm infections by evaluating the color of the conjunctiva. Please note, gastrointestinal parasites are not the only cause of anemia- this tool is intended to be used in areas with known Haemonchus contortus. When used in isolationIn medical and health-related circumstances, isolation represents the act or policy of separating an individual with a contagious health condition from other residents in order to prevent the spread of disease. In non-medical circumstances, isolation represents the act of preventing an individual from being near their companions due to forced separation. Forcibly isolating an individual to live alone and apart from their companions can result in boredom, loneliness, anxiety, and distress., the FAMACHA system assigns a score that correlates to recommendations for treatment, all based on a quick and easy check of the mucous membranes. The sanctuaries we’ve talked to that use this tool use it as a way to identify individuals who look like they may be anemic (or are paler than usual) and then they use other screening tools to assess whether or not deworming is necessary. Even in agricultural settings, recommendations are moving away from solely using FAMACHA and instead recommend combining it with other screening tools, because using FAMACHA on its own may result in deworming individuals who do not actually need to be dewormed. For more information on making FAMACHA work in a sanctuary setting, check out our resource here.
- Overall Appearance– In addition to looking for signs of anemia, it’s important to make other observations about the individual. Do they look bright and alert or dull and tired? Do they have bottle jaw or diarrhea? Does their coat look healthy or rough? Do they look like they are losing weight? All of this information is useful when determining if a resident should be dewormed. An individual who otherwise looks very healthy and is a good weight, but has a high FAMACHA score or high fecal egg count may not require immediate deworming, but an individual who does not look well and has a moderate FAMACHA score may require more immediate intervention.
- Fecal Egg Counts (FEC)– Fecal testing alone will not tell you who should be dewormed because an individual’s parasite load does not necessarily correspond to their degree of clinical illness. As explained above, each individual will be impacted by parasitic infection differently. Because of this, there is currently no widely accepted cut-off in terms of an egg count that does not warrant deworming versus an egg count that does. Therefore, some sanctuaries that once used an individual’s fecal egg count to determine whether or not to deworm an individual (for example, deworming anyone who has more than 1,000 eggs per gram), now use fecal egg counts as one piece of information to consider along with an individual’s hematocrit level (described next) and clinical signs. If a resident has an exceptionally high FEC (with “high” being somewhat relative), you may consider deworming them in order to reduce pasture contamination. This is a nuanced decision that is best made under the guidance of an experienced veterinarian. Keep in mind that while a fecal egg count alone is not a reliable tool to determine who should be dewormed, fecal egg counts play a very important role in monitoring for development of resistance.
- Blood Tests– Hematocrit testing, or Packed Cell Volume (PCV), measures the percentage of red blood cells in the body and can be a very useful tool when making selective deworming decisions. Whereas FAMACHA scoring uses the color of the mucous membranes to estimate varying degrees of anemia, hematocrit testing will give you more objective information. Hematocrit testing is part of a complete blood count (CBC), but it can also be done on its own as a simple test; with proper training and equipment, you can check hematocrit levels on-site, which will save both time and money. Caregivers may use hematocrit results to determine if a resident needs immediate intervention due to dangerously low hematocrit levels, or they may use results to determine which individuals should have fecal samples analyzed. It’s important to keep in mind that in areas where barber pole worm is predominant, it is the leading cause of anemia, but it is not the only possible cause. Conducting a fecal analysis will help determine if a parasitic infection can explain an individual’s anemia or if further diagnostics should be pursued. Your veterinarian may also recommend testing the individual’s total protein level, which is another blood test that, with proper training and the right tools, can easily be done on-site. These tools can be very useful not just as screening tools for barber pole worm infections, but also as a means of evaluating an individual who does not look well. These results will give you more information to share with your veterinarian, and in the event of an emergency, will allow you to gather valuable information while waiting for your veterinarian to arrive at the sanctuary, or when determining whether an individual should be rushed to the hospital.
We recommend you work closely with an experienced veterinarian to establish screening protocols for barber pole worm and to work with them when deciding if deworming is necessary. As you can see, for many of these screening tools, it is less about using them to get a straightforward “yes” or “no” in terms of whether or not to deworm, and more about using them as a way to gather information about what is going on with an individual. When making deworming decisions with your veterinarian, be sure to give them specific information such as the individual’s age, species, and breed, as well an overview of their health history (do they have other health challenges such as Caprine Arthritis Encephalitis?) It’s also important to give them information about the individual’s history with barber pole worm infections. Are they a resident who frequently has issues with haemonchosis? Were they recently dewormed? Have their fecal egg counts shown issues with resistance to certain medications? All of this information will help you and your veterinarian make the best decision possible about not just whether or not to deworm, but also what to use, and if other strategies should be employed.
Suggestions For Treating Individuals Who Are Clinically Ill
The specifics of how you respond to an individual who is clinically ill from a barber pole worm infection should be determined based on the specific situation and should involve a discussion with your veterinarian. If an individual is anemic, weak, or lethargic, or if they have bottle jaw, or are showing other concerning signs of illness, contact your veterinarian immediately. They may recommend immediate deworming and, if not already done, blood work to assess the individual’s degree of anemia. Similarly, if you are able to perform hematocrit testing and you find that an individual has a dangerously low hematocrit level, you should contact your veterinarian immediately. Severe anemia is a life-threatening emergency – the individual may need hospitalization in order to receive a life-saving blood transfusion.
Always defer to your veterinarian for treatment recommendations. In this section we will simply provide the most current deworming recommendations, as well as some other treatments your veterinarian may recommend.
Combination Treatments
In recent years, deworming recommendations have moved away from the use of a single drug at a time, to the use of two or three drugs from different classes in combination (while adhering to a targeted deworming approach). Dr. Kaplan explains that there are two important benefits to using combination treatments. First, dewormers used in combination have an additive effect, which increases the efficacy over using dewormers individually. Second, combination treatments will kill a larger number of resistant worms (because worms that are resistant to one of the drugs used will hopefully be killed by one of the other drugs). This will lower the percentage of resistant worms in the population. For more information on the benefits of combination deworming treatments, as well as useful tables that illustrate the additive effect of combination treatments, please refer to this article written by Dr. Kaplan. The article also explains why rotating dewormers is no longer recommended and how it contributes to drug resistance.
While some countries, such as New Zealand and Australia, offer products that contain multiple dewormers in one single formulation, these are not currently available in the U.S. Most recommendations suggest using a combination of albendazole, moxidectin, and levamisole, because these drugs represent the most potent dewormers from each of the three groups of anthelmintics available in the U.S. When using combination treatments, be sure to administer a full dose of each drug you are using. Do not mix these drugs prior to administration! Instead, administer each drug in a separate syringe, one after the other. While combination treatments have shown great success, it is imperative that you maintain refugia, otherwise you will develop a worm population that is resistant to multiple dewormers.
Additional Support
Some individuals may not need much more than deworming and monitoring, but others may need additional support. It is important to make sure the individual is eating and drinking, and if they are not, that supportive care is offered to keep them hydrated and provide the nutrients they need. Additionally, if the individual has diarrhea, your veterinarian may recommend specific treatments to address this issue.
Certain vitamin and mineral supplementation, such as iron or B12, may be beneficial depending on the situation, but supplementation, especially if using injectable medications, must be done in consultation with your veterinarian.
Other Strategies To Help With Worm Control
In addition to the strategies listed throughout this resource, there are some other strategies and products you may want to look into when thinking about how to manage barber pole worm and protect your residents. These include:
- Copper Oxide Wire Particles (COWP)– This is a slow-release, poorly absorbed form of copper, not to be confused with copper sulfate, which is less effective and more likely to result in toxicity. COWP (such as Copasure boluses) are marketed as copper supplements for individuals who are deficient in this nutrient, but they also may have a role in barber pole worm management. Studies show that COWP can be effective against adult barber pole worms and, when used with a dewormer, can increase the efficacy of treatment. However, the decision to use COWP must be done carefully and in consultation with your veterinarian. Because sheep, llamas, alpacas, and some goats are more sensitive to copper, reserving this option for your goat residents may be prudent, but be aware that goats, while being less sensitive to copper, can still develop toxicity. Your veterinarian should look at your residents’ copper intake via all food and also assess other mineral levels that impact copper absorption by doing soil and water testing as well as looking at their mineral supplementation and diet to determine if the use of COWP is advised. Supplementing with too much copper or supplementing without assessing your residents’ copper intake from food, minerals, water, and other sources could result in copper toxicity, which can be fatal. Be aware that recommendations that suggest repeat administration of COWP 4-6 weeks after the initial dose may not be appropriate for sanctuary residents, contradict Copasure instructions (which say to wait at least 6 months), and have not been evaluated for long-term safety if administered year after year. We only talked to a couple sanctuaries that have used COWP, and they worked closely with their veterinarians to determine an appropriate protocol, but neither sanctuary planned to use COWP more than once or twice a year. If you and your veterinarian decide it is safe to incorporate COWP into your control strategies, be sure to talk to them about monitoring your residents’ copper levels, which is complicated and may require post-mortem examinations and liver testing.
- BioWorma– This product only recently became available in the U.S. and contains a fungus (Duddingtonia flagrans) that eats barber pole worm larvae. When consumed by sheep, goats, llamas, or alpacas, the fungus passes through the individual with no effects. When passed in their feces, it goes to work trapping and consuming worm larvae, thus reducing the number of infective larvae that develop. We have not connected with any sanctuaries that currently use this product, and it sounds like it might be both cost prohibitive and also logistically difficult to administer to everyone, however, this might be something to look into if you have a smaller group of residents who have severe parasite issues, especially if anthelmintic resistance has seriously reduced treatment efficacy. If you would like to learn more about this product, check out this webinar with Chris Lawlor from International Animal Health, hosted by ACSRPC.
- High Condensed Tannin Plants– Plants such as Sericea lespedeza, sainfoin, and big trefoil that contain condensed tannins can be beneficial in managing worms. Research has focused on Sericea lespedeza, with studies showing that it reduces parasite loads in sheep and goats. You may consider incorporating some of these plants into your residents’ living spaces, and your local cooperative extension office should be able to offer recommendations for plants suitable in your area, but we recommend you also have a discussion with your veterinarian or a nutritionist about which plants to use and in what proportion. Keep in mind much of this information comes from agricultural settings where they are likely primarily caring for females and intact males. Any time you make dietary changes, it’s important to consider any unintended consequences that may arise. When caring for male sheep and goat residents, be sure to investigate if a particular change might increase your residents’ risk of developing urinary calculi and potentially life-threatening urinary blockages.
Managing barber pole worm is complicated and requires implementing multiple strategies. By understanding the life cycle of this parasite and how drug resistance develops, you will be better able to identify ways to reduce your residents’ exposure to this parasite and avoid practices that speed resistance. As mentioned in the beginning of this resource, be sure to keep up-to-date about the most recent recommendations for barber pole worm management and treatment so that you are best able to slow resistance and protect your residents from parasitic disease.
SOURCES:
Review of Anthelmintic Resistance | ACSRPC
Farmers’ Estimations Of Sheep Weights To Calculate Drench Dose | R B. Besier and Diane Hopkins
Public Enemy #1: The Barber Pole Worm | Dr. Kwame Matthews (Non-Compassionate Source)
Part 1: Being A Worm | Dr. Anne Zajac (Non-Compassionate Source)
Part 2: Managing Worms | Dr. Anne Zajac (Non-Compassionate Source)
Parasite Biology Impact Control | ACSRPC (Non-Compassionate Resource) *graphic featured photo*
Large Animal Internal Medicine 5th Edition | Bradford P. Smith (Non-Compassionate Source)
Medicine and Surgery of Camelids, Third Edition (Non-Compassionate Source)
Haemonchus contortus Infections in Alpacas and Sheep | Sarah Jane Casey (Non-Compassionate Source)
Pathology Of Haemonchus contortus In New World Camelids In The Southeastern United States: A Retrospective Review | Erin E. Edwards, Bridget C. Garner, Lisa H. Williamson, Bob E. Storey, Kaori Sakamoto (Non-Compassionate Source)
How And Why Resistance To Worm Remedies Develops | Dr. Ray M. Kaplan (Non-Compassionate Source)
Deworming Right | Susan Schoenian (Non-Compassionate Source)
Worms and Drench Resistance | Elizabeth Garner-Paulin (Non-Compassionate Resource)
SCOPS Calls For Action As First Case Of Resistance To Group 4 Wormer (Monepantel) Is Reported In The UK | SCOPS (Non-Compassionate Source)
Why And How To Practice Integrated Parasite Control For Sheep And Goats | Dr. Anne Zajac (Non-Compassionate Source)
Grazing Away Parasites | Dr. Niki Whitley (Non-Compassionate Source)
Combination Dewormers: The Time Is Now | Dr. Ray Kaplan (Non-Compassionate Source)
When Deworming Is Not Enough | Dr. Niki Whitley (Non-Compassionate Source)
Copper Oxide Wire Particles | ACSRPC (Non-Compassionate Source)
BioWorma | Chris Lawlor (Non-Compassionate Source)
