Reducing Risks of Wildlife/Livestock Parasite Transmission

Progress report for GNE20-244

Project Type: Graduate Student
Funds awarded in 2020: $14,907.00
Projected End Date: 08/31/2022
Grant Recipient: University of Maine
Region: Northeast
State: Maine
Graduate Student:
Faculty Advisor:
Anne Lichtenwalner, DVM PhD
University of Maine
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Project Information

Summary:

White-tailed deer (Odocoileus virginianus; WTD) pose a risk to livestock health due to a parasite, meningeal worm (Parelaphostrongylus tenuis; P. tenuis) also called brainworm. Farms where livestock grazing systems overlap with WTD habitat (P .tenuis definitive host) and that harbor high numbers of terrestrial gastropods (P. tenuis intermediate hosts) face elevated risk of brainworm infection in their livestock. Brainworm often causes severe neurologic disease or death in livestock, primarily to small ruminants (sheep, goats, llamas and alpacas)¹. Small-scale farmers face a large risk of production loss due to meningeal worm, as even a small increase in mortality can have a large financial impact. The objectives of this project include 1) establishing baseline abundance for brainworm on Maine farms, 2) estimating risk of P. tenuis infection to small ruminants in overlapping grazing systems with WTD and 3) proposing risk management and preventive measures to producers. 

In our first year, 2020, we were restricted to Covid-19 protocols, limiting what research we could do in the field and laboratory. We were able to collect preliminary data and test and refine methods. In 2021, gastropods and WTD fecal samples were collected from six farms in Maine to determine meningeal worm prevalence in pasture systems. Prevention methods such as pastured poultry and mowing treatments were investigated. Producer education will be developed to minimize risk, to aid early detection, and to direct producers to seek appropriate veterinary treatment.  Several abstracts and presentations to national and regional audiences have been produced and additional educational materials will be disseminated via Extension publications, a recorded presentation, and a peer-reviewed publication during the second year.

On the six small ruminant farms that were sampled, gastropod and larval populations varied. Out of over 2,600 gastropods collected, only around 1.8% were found to harbor meningeal worm (via morphological measurements). An average of 4% carried larva, in general, which will be genetically identified. Gastropod population trends varied from farm to farm, however all farms experienced a population reduction in June, likely due to drought conditions, snail life cycle, or a combination of both. The effect of climatic conditions, such as soil moisture, air temperature, humidity, vegetation type and height, and shade content will be examined to determine correlations with gastropod presence. All farms experienced WTD presence, with use in or around livestock grazing areas. WTD fecals collected did have first stage larvae present. 

Experimental treatment methods aimed at mitigating risk of P.tenuis exposure to small ruminants included pastured poultry and mowing. A group of around 200 laying hens routinely rotated proved to significantly reduce snail populations. Additionally, intensive mowing to keep vegetation short (<6”) is an effective method in reducing snail populations. A combination of these prevention methods in areas of high WTD use and gastropod abundance may reduce risk of P.tenuis infection to small ruminates. 

Our survey suggests that most farmers know about meningeal worm risk on farms (95%) and some have had suspected cases (41%). 98% said their farm was near white-tailed deer habitat, and 88% said that deer were observed near their livestock grazing system.

The exploration of transmission factors of P. tenuis and other gastropod-born helminths between wild cervids and small ruminants can inform methods to decrease risk. In grazing areas with observed WTD use and high gastropod abundance, risk of P. tenuis transmission to small ruminants increases. Specific microclimatic conditions may increase or decrease gastropod populations; these are currently being analyzed for linear relationships. By understanding risk factors associated with gastropod- borne helminth transmission, farmers can make management decisions to minimize threat of disease to their livestock. In addition, prevention methods that reduce snail and slug populations can decrease risk. In systems where farmers have suspected meningeal worm cases, pastured poultry before small ruminant grazing and/ or intensive mowing in areas of abundant gastropod populations can significantly reduce gastropod populations, thus reducing the chances of P.tenuis uptake. These approaches provide farmers with a solution to controlling P.tenuis transmission to livestock. Emotional and financial effects from the morbidity or mortality caused by this worm may be lessened due to these methods. 

To date, there is no diagnostic for P.tenuis in small ruminants, however, promising developments in this area using blood serum have proved effective in detecting P.tenuis presence in moose. Because the symptoms of the worm’s presence within livestock can be mistaken for many other diseases, such as rabies, listeriosis, polioencephalomalacia (PEM), bacterial/ viral meningitis, farmers must take caution when assessing animals, as some of these can transmit to humans. It is vital for farmers to establish a relationship with a veterinarian for the care of sick animals and for guidance in treating suspected meningeal worm cases. Prevention methods recommended in this study have associated financial costs such as feeding chickens or fuel for mowing machines. Additionally, these approaches require time for moving temporary fences or to mow. Pastured poultry promotes healthy soils and is a common practice in sustainable or regenerative farming systems. Conversely, frequent mowing may reduce soil moisture and quality. Nonetheless, repetitive mowing in areas of gastropod abundance can lower populations by the reduction of suitable habitat. Further studies to identify which poultry species are more effective at gastropod reduction may be warranted. 

Conflicts between farming and nature have been recorded for centuries and are well known. Sustainable farming provides solutions for farmers to work with the environment (soil, water, and even wildlife) in a holistic way. Integrative pest management (IPM) using biological controls for unwanted pests is a common practice in sustainable agriculture. The implications of reducing gastropod populations are not well known. These molluscs are important nutrient cyclers and decomposers. Further studies to determine the long-term effect of gastropod reduction on pasture systems may determine if their presence is more vital than their absence. 

An extension of this study, formed by two undergraduate students, found presence of microplastics within gastropods, and livestock and deer feces. This finding raises concerns for the health of these animals and the environment. Our survey indicated that farmers are concerned about microplastic effects for themselves, their animals, and the environment. More studies on the effect of plastics in livestock and soils, as well as behavior of farmers/ use of plastics, could enact change in farmer use of plastic on farms and even policy for plastic uses.

Project Objectives:

1) Assess the prevalence of P. tenuis on Maine’s agricultural landscape

Results from our nation-wide survey will give general insight to the perceived incidence of P.tenuis on farms. Examining fecal samples and gastropods in the lab will indicate the prevalence of brainworm on Maine farms. Necropsy, followed by histology, of animals showing neurologic symptoms before death will be performed as appropriate using the UMaine VDL resources

2) Establish the risk factors associated with brainworm to determine likelihood of infection to livestock.

Farmers across the north east utilize various grazing strategies which often overlap with WTD habitat. This, in combination with high gastropod numbers,creates risk of livestock brainworm infection on a farm. Weather trends, grass height, wetness, topography, and woody debris may change gastropod behavior or abundance. These factors, once quantified, can be entered into a statistical model to determine the likelihood of infection to animals exposed to different grazing systems, climatic events, and preventive treatments. These factors will be explored across several farms in Maine where pastures support deer and small ruminant livestock, such as sheep and goats. This study will be the first evaluation of P.tenuis on Maine livestock farms.

3) Create management strategies for farmers.

After analyzing the risk factors associated with increased prevalence of brainworm, preventive measures to combat the parasite will be suggested in project publications. In a closely related project, integrated pest management using poultry (ducks, other species) is being explored by an undergraduate member of the Lichtenwalner lab.  This additional project has been funded via 2 internal grants and the IACUC approval is in place.

Introduction:

The purpose of this project is to evaluate risk of brainworm to domestic livestock, and to evaluate risk management techniques. Brainworm infection of small ruminants often causes death, resulting in emotional and financial difficulties for small farmers. Diagnostic serologic tests are not optimized for use in livestock, and diagnostic fecal examinations don’t work for livestock, as the worm cannot reproduce in any species other than the white-tailed deer (Odocoileus virginianus; WTD).  Additionally, preventive practices for agriculture have not been well documented. The results of this project will inform future outreach efforts to producers about risk assessment, preventive steps, and recognition/treatment for this deadly infection in livestock.

Problem 1: Diagnosis.

Currently, diagnosis of P. tenuis in livestock is neither easy nor cost-efficient but is important due to zoonotic and very serious “look-alike” diseases, like rabies, eastern equine encephalitis (EEE), listeriosis, polioencephalomalacia (PEM), scrapie, and bacterial meningitis¹.  While infection can be confirmed by histology of the spinal cord and brain post-necropsy, this is time-consuming and expensive. Recently, a serologic test has been developed for brainworm detection in moose, but is not validated for small ruminants.  As well, response to larvicidal treatment may assist with diagnosis, but may enhance anthelmintic resistance on small ruminant farms, a serious problem for farmers.

 

Problem 2: Risk Evaluation and Risk Management.

In natural grazing systems, P. tenuis risk to livestock is not well documented. Farmers in the North East who graze their animals in WTD habitat would be expected to face an increased risk of brainworm exposure, as approximately 84% of WTD are infected with brainworm² ³ ⁴. Environmental conditions and frequent mild winters/early springs increase deer survival, resulting in escalated production of larvae². Additionally, gastropod abundance might be expected to increase under these conditions. Height of vegetation, wet fields, and woody debris may also increase gastropod presence⁵.

This project seeks to quantify the variables associated with risk of infection within different livestock grazing strategies in high deer population areas. Implementation of this goal will include visiting several farms across Maine to quantify the different risk factors. Observations will include measuring and identifying vegetation in grazing plots, documenting climate and weather trends, assessing deer abundance and movement with the use of game cameras, identifying infected gastropod species, and counting infected gastropods within the study sites. These variables may create a model that could assist farmers or consultants with preventive grazing strategies.

 

Problem 3: Producer Knowledge.

By deploying a nationwide survey, we will gain insight about producer knowledge of the disease and quantify the perceived infections across the United States. Questions also focus on grazing systems and WTD habitat overlap with livestock. This survey will help identify future study sites in the state of Maine, as well as risk perception areas of need. This and project results will create educational opportunities that can help with risk management and reducing infection in livestock.

Cooperators

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  • Joshua Hatley (Educator)

Research

Materials and methods:

Establish the risk factors associated with brainworm to determine likelihood of infection to livestock.

To establish the risk factors associated with brainworm, visits to working farms is necessary. Sampling will be held over ten weeks between May- August for two seasons.

  1. Study locations: From voluntary recruitment, six farms in Maine will be selected at random based on project criteria: forty or more small ruminants (goats, sheep, alpacas, and/or llamas), an abundant and active deer population, and observation of gastropods. Farms will be mapped to document areas of wetness, forest, field, rockiness, and man-made influence (driveways, barns, etc.).
  2. Sample sites: One grazing field per farm will be chosen randomly based on time of grazing when animals are about to be, or are currently, grazing. Sampling sites within the field will be stratified random samples to include inside, outside, and on the fenceline of pastures. PVC grids measuring 45cm x 90cm and a search time of ten minutes will be used for collections.  
  3. Vegetation within the field, on the field’s fence line or boundary line, 10m out of the grazing area, will be mapped. Land use type (agricultural, forest, commercial) will be documented in a 1mile (1.6km) radius of the field site. The grazing system which sample sites are located will be recorded (rotational, permanent pasture, dry lot, etc.). Within the grazing system, vegetation density, height, and species will be recorded.
  4. When visiting sample sites, climatic data such as ambient air temperature, precipitation, wind direction, and humidity will be recorded.
  5. Game cameras will be deployed on habitat buffers (field edges) to record deer movement and visitation to the field. Deer abundance is related to increased brainworm within gastropods, since deer feces carry the infective larval form that must gestate within the gastropod intermediate host

Document prevalence of brainworm on Maine farms.

To establish the baseline of prevalence of brainworm we will experiment on gastropod and deer fecal samples from the farms, mentioned above, in the laboratory. A survey, made by an undergraduate in our project group, that encompasses risk perception questions will be sent to producers across the country.

  1. A survey will be sent nationwide to assess producer knowledge of brainworm. This survey will help identify future study sites in the state of Maine, as well as risk perception areas of need. Questions also focus on grazing systems and WTD habitat overlap with livestock.
  2. Collection of deer fecals: fecal samples from deer will be collected within the field while the livestock are grazing. As deer fecal pellets look similar to that of sheep and goat, we may have to choose deer fecal pellets from areas adjacent to the field or slightly before livestock are introduced to the pasture.
  3. Examination of fecal pellets for P. tenuis: grouped deer feces from sample fields will be placed in a Baermann apparatus to extract stage 1 larvae.
  4. Collection of terrestrial snails and slugs: gastropods will be collected in transects (mentioned above). Different materials will be offered for longevity and moisture-holding ability. “Traps” staked to the ground will provide shelter from brisk mornings or weather events. Cardboard or plastic at a slight vertical angle may provide shelter for climbing species and those less dominant. Three 1m x 1m plots will be chosen randomly each farm visit to account for free-living gastropods in the field.
  5. Gastropod movement: Travel of snails will be a subproject to determine the migratory behavior of common land snails. A mark-recapture method will be utilized by an undergraduate member of our project.
  6. Examination of gastropods for P.tenuis: Gastropods will be placed in an artificial digest to entice the third-stage larvae out of the host tissue. These will be quantified, measured, and genetically tested.
  7. Necropsy will be performed on up to six deceased individuals from these farms that had neurologic symptoms leading to death.
  8. Diagnosis in livestock will be confirmed via necropsy of deceased animals from project farm sites at the UMaine VDL. 

Surveying for gastropods on a Maine farm.
Amber snails (family Succineidae) on wildlife scat.
Baermann technique to examine living larva from fecal samples.

Create management strategies for farmers.

Creating management strategies for farmers will first require statistical analysis of significant risk factors found from the study. Response variables include animal health indices (eg. behavioral analysis, symptomatic response, or death) after ingesting meningeal worm larvae. Modeling risk will include the factors that increase likelihood of infection. Management strategies will be informed from the results of this study and broadcasted to a wide audience (see Outreach section). Organic control methods of pastured poultry and mowing will be examined on two farms to assess before and after gastropod population numbers at one week intervals. In exploring the gastropod-borne helminths on Maine’s farmed landscapes, we may uncover other harmful parasites in addition to P. tenuis.

  1. Duck effectiveness in a lab setting: Members of our group for an undergraduate capstone project (not part of this proposal) will be testing the effectiveness of ducks as “snail grazers”. Some ducks will be experimentally infected with P. tenuis at different levels to test if the ducks readily ingest gastropods, if they become infected, if their enteric tract kills the infective larvae, or if they expel viable P. tenuis larvae in their feces.
  2. Pastured poultry effectiveness: Large-scale organic poultry growth operations often place poultry on their fields to manage for insect pests, rejuvenate the soils, and substitute feed. We will examine the before-and-after poultry flock foraging gastropod numbers to assess the effectiveness of poultry management. Three 10m lines will be surveyed for ten minutes each before and after poultry exposure to pasture. 
  3. Mowing effectiveness: Although many producers use pasture as primary feed sources, and are eager to get small ruminants out onto lush spring pastures, mowing pastures may significantly reduce gastropod numbers. Population densities of gastropods will be measured to determine the effectiveness of mowing on gastropod control with a random complete block design. 

 

RCBD Mow treatment layout.
Research results and discussion:

Gastropod and Larval Collection Results:

In 2021, the graduate student researcher and undergraduate research assistant visited six different farms twice per month from mid May until early September. Farm locations in Maine were coastal, mid-coast, central, and western/ mountains. Farmers managed their sheep ad lib, with the majority rotating herds on pasture throughout the summer. Gastropods were gathered in the mornings with an average collection time lasting 3 hours. With each collection, biotic and abiotic factors were recorded such as soil moisture, air temperature, air humidity, dew point, weather, vegetation type and height, duff depth, and shade cover. Animal presence and timing of pasture exposure was also recorded. Additionally, any instance of animals with neurological symptoms and treatment were recorded. Monthly fecal collections of deer and livestock were observed with a Baermann apparatus for living larvae. Game cameras were deployed to observe deer presence on livestock grazing areas.

In total, we collected over 2,600 gastropods which consisted of 97% snails (n=2,553) and 3% slugs (n=86). The vast majority of gastropods were amber snails (family Succineidae).  Of these, 110 were positive for larvae. 139 larvae were extracted or imaged. Based on morphological measurements of larvae, 36% were identified as P.tenuis. Gastropods were 1.8% positive for meningeal worm and 4% positive for larvae in general. Genetic analysis of collected larvae will determine genus or species of worms. Of the six farms, larval content rates varied from 0%- 10%. Below are the findings for each farm:

  • Farm A Winterport: The Katahdin flock of 50-110 sheep were rotated intensively as groups of 20-50 starting mid- May. This farm had the highest abundance of gastropods (n=1277) and larvae (n=110) with a larval infection rate of 5%. Gastropod populations dropped slightly in June, but rebounded in July and again in August. Larval content was also the highest during these months. Deer were caught on game camera jumping over fences to graze on pasture before and after sheep rotations in both research pastures. Deer fecal pellets were difficult to find due to vegetation height and thickness. The pellets we found had dorsal spined larvae which were collected and frozen. Four lambs from Farm A had clinical symptoms of P. tenuis ( three around September, 2021; one in January, 2022). The farmer reports that the first ewe lamb was “down with a stiff neck and back” and “catatonic stare.” It was treated with thiamine and a 5 day regimen of cydectin, valbazen, and dexamethasone. The second and third lambs showed signs of ataxia and weakness in the hind end; these lambs were also treated with the same 5 day regimen. The three lambs recovered, although they continue to have mild ataxia. The last lamb was euthanized and not available for necropsy. The rotational grazing strategy on this farm may be a factor in abundant gastropod populations. Notably, the farmer actively strives for high soil moisture to promote healthy pasture vegetation. Rotation of sheep occurs when grasses are folded over, not by the height of the vegetation (i.e., the “ankle high” rule), a strategy that is common practice. In the fields closest to the barn, sheep revisited sites 3-4 times. In the larger fields farther away from the barn, sheep were rotated through twice with the field hayed in between.
  • Farm B Washington: This farm uses both rotational and continuous grazing strategies for their 80-120 sheep. Sheep are kept in continuous pasture near the barn at night. The ewe and lamb group is rotated on a ten acre field that is often visited by deer. The wether and ram group is kept on pastures closer to the barn and rotated less frequently. Both groups graze vegetation down to almost bare ground before being rotated. Of 204 gastropods collected, 5 had larvae present (2%). Gastropod populations declined in June, rebounded in early July, declined again in late July and then increased in August. No gastropods were found on the randomized plots mid-August through the rest of the summer. This may be attributed to slow or no regrowth of pasture vegetation and dry soil conditions. It also could be attributed to the random selection process where a section of high abundance was not sampled. Notable populations were found in a sizable (half acre) patch of burdock. The farmer reported frequent visits by numerous (4-8) deer on the larger rotational field. This was supported by game camera photos. Collecting deer fecal pellets was a challenge due to thick, spring vegetation and later abundant sheep pellets over the field. Pellets found in the woods had dorsal spined larvae. 
  • Farm C Palmyra: This farm does not practice rotational grazing often and animals are supplemented with hay. The field used for rotational grazing in the past was used for hay and no animals were exposed to deer overlap. In the continuous grazing area, vegetation was typically short and the soil moisture low. Several dozen poultry were free ranged in the sheep and goat grazing area. Only 15 gastropods were collected; one had larvae for an infection rate of 7%. Snails and slugs were primarily found outside adjacent to the fence or in the hay/ rotation field. Populations dropped in June and no gastropods were found in either field for the remainder of the season. Deer fecals had dorsal spined larvae. One lamb showed symptoms of P. tenuis including ataxia, was treated with five- days of anthelmintic, and recovered. 
  • Farm D Sidney: This farm, consisting of around 50-100 small ruminants, practices both rotational and continuous grazing. Rotations occur when vegetation is short or almost bare. Animals revisit the same grazing areas several times throughout the season. Out of 67 gastropods collected, 10% (n=7) were observed with larvae. The pastures had dry soil conditions and did not contain any gastropods, with exception of the verge area within a pasture adjoining the main barnyard. Notably, gastropods were found closest to anthropogenic sources (barnyard, water sources, veggie garden). The farmer reported that deer frequent the barnyard apple trees located in the driveway between two continuous pastures (the area of highest gastropod abundance). They also note that two kids showed signs of neurological symptoms (“ataxia and hind end weakness”) before they were euthanized. We could not obtain animals for necropsy. 
  • Farm E South Paris: On this western Maine farm, only 8 slugs were collected and no larvae were present. 50- 80 ewes were rotated on a secluded mountain side. Soil conditions were consistently dry and vegetation thin/ short or bare. Sheep revisited the field twice over the summer. Deer frequently visited the field when sheep were not present or bedded down adjacent to the fence. 
  • Farm F Freeport: This coastal Maine farm with around 20 Katahdin sheep, 10 Oberhasli goats, and over 50 Jersey and Holstein cows practices intensive rotational grazing, where animals are moved once vegetation is folded over. Soils stayed relatively moist (~70-100%) in pastures, even during drought conditions. Of 1067 gastropods collected, 29 gastropods contained larvae (3%). Deer fecals contained brainworm. 

A consistent observation among these farms is that populations of gastropods are variable over time. Additionally, each farm’s gastropod populations differ greatly, likely due to local microclimate conditions. Population abundance trends may be associated with the natural life cycle of the gastropods, environmental conditions, or a combination. From early June to July, much of the state was in severe drought, which may have been a factor in the decline of gastropod populations and parasite transmission. Analysis of environmental conditions is currently underway to determine correlations to gastropod presence and abundance. 

Gastropod sampling on a Maine farm, the flock looks on.
Morphologic measurements of a P. tenuis larva [10x]
P. tenuis tail [40x]

Preventative Treatment Results:

Pastured Poultry: Around 200 laying hens were rotated about every four days within a 25,000 sq.foot pasture. Broiler chickens were observed for two weeks, but as they were rotated less frequently (once per 2 weeks), confined to 100 sq. foot chicken tractors and were less active, the data was omitted from the study. Chickens were supplemented with free-choice grain at all times. Vegetation was primarily grass and clover. The mean difference of before and after poultry exposure was statistically significant with a p-value of less than 0.01. This indicates that pastured poultry (laying hens) are an effective strategy for gastropod control. 

(Note: No IACUC was needed, per committee instruction, for the pastured poultry study as the birds were cared for by one of the farmer participants and because there was no direct contact or manipulation from the researchers).

 

Chickens on pasture assessed for efficiency of gastropod control.

Mowing: Mowing took place at the University of Maine’s J. Franklin Witter Teaching & Research Center, also known as Witter Farm. This area carries a healthy population of Succineidae snails. A random complete block design was used with four blocks and three treatments (control, one year mow, two years mow). Each block consisted of three 30m x 20m randomized treatment sections for a total of twelve experimental units. Within treatment plots, 45 x 90 cm sections every 8 meters were surveyed for a maximum of 10 minutes. Gastropod abundance and diversity was documented as well as environmental conditions. The initial plan for biweekly measurements from May- October was altered due to equipment failures. A repeated measures ANOVA followed by pairwise comparison determined that mowed pastures have fewer gastropods than the control (not mowed) in the first 2 monthly observations (p=0.015 and < 0.01, respectively). 

 

Survey:

We have received 65 responses to our nation-wide survey. Our conclusions are that producers are aware of brainworm as a risk to their livestock (95%), with 41% of farmers saying they experienced brainworm related illness on their farm. Survey data is currently being further analyzed. Several respondents from Maine contacted us to volunteer their farms for research. Communication with farmers is a current effort. Some notable results from the survey include:

Hobby farming/ pet livestock consist of 29%, partial income 55%, total income 9%, and other 7%.

Farmer respondents have diverse livestock, including cattle (8%), sheep (19%), pigs (7%), goats (13%), horses (8%), alpacas or llamas (30%), and other (15%).  Brainworm has been documented in several of these mammalian species.

Different grazing systems seem to be used across the same farm, especially with alpacas/llamas and sheep. 

Use of continuous grazing (one pasture all the time) is most common for alpacas/llamas and is followed by goats.  

Use of rotational grazing and dry lots is most common in alpacas/ llamas and is followed by sheep. 

95% of survey participants had heard of brainworm prior to the survey.

41% of producers said they had suspected or confirmed cases of brainworm on their farm.

98% said their farm was near white-tailed deer habitat, and 88% said that deer were observed near their livestock grazing system. 

82% of farmers said their poultry share pasture or housing with livestock. 

Abstracts and presentations were given at the 2022- Maine Agricultural Trade Show; 2021- Conference for Research Workers in Animal Diseases in Chicago, the online University of Maine Student Symposium; 2020- the University of Maine Cooperative Extension’s newsletter “Cows and Crops”, the Extension Risk Management Education National Conference (abstract accepted and travel award granted, but in-person conference canceled in 2020), and the online Everyday Farmers Conference. 

 

Research conclusions:

Exploring alternative control methods for helminth control in agricultural systems is important for the health of livestock animals. While the practice of integrated pest management (IPM) isn’t new, specifically targeting parasite intermediate hosts is an emergent area. Our research using pastured poultry for the control of gastropods, which are frequent intermediate hosts of parasites such as meningeal worm (Parelaphostrongylus tenuis), flukes (Fasciola sp.), and rat lungworms (Angiostrongylus cantonensis), shows that the rotation of poultry across gastropod abundant areas can lower snail and slug populations. Active breeds that do well on pasture, such as Rhode Island Red chickens or Khaki Campbell ducks, may perform better than broiler chickens, although further research is needed to confirm this. The integration of this prevention method would require poultry exposure to pasture before small ruminant grazing access. Such a process is a reversal of common IPM practices using pastured poultry, where birds are rotated after ruminants for the purpose of scratching manure into the soil and ingesting fly larvae on manure. In grazing areas with high white-tailed deer use and gastropod abundance, or a farm with a history of suspected P. tenuis infection in animals, farmers may want to consider rotating poultry onto pastures before introducing livestock, then, if desired, rotating them or another bird group back on once ruminates leave. 

A potential setback to the pastured poultry control method is that birds may pass ingested larva through their digestive tracts. In our lab, we inoculated Succineidae snails with stage one larva to incubate under controlled conditions, then fed snails with infective stage larvae to ten Grimaud hybrid meat-type ducks. Fecals from ducks were observed before and after infective gastropod exposure. Around 25% of stage three larvae passed though the ducks’ digestive system intact. However, there is little evidence suggesting stage three larvae can survive outside of a host. In addition to poultry, mowing as a control method for gastropods is another method that farmers can try. Mowed or low vegetation areas contain fewer gastropods than unmowed areas. Repeated mowing efforts in areas intended for grazing may not be ideal for soil health, however, in areas of high P. tenuis probability this method may be ideal to practice over a grazing season or two to limit gastropod population growth. Then, after forage regrowth, introduce livestock to the area. A combination of mowing and pastured poultry could be used. The second season of our project will determine if snail populations stay low at intensively mowed sites and the rate of which gastropods repopulate areas previously mowed.

Participation Summary
6 Farmers participating in research

Education & Outreach Activities and Participation Summary

5 Consultations
8 Webinars / talks / presentations

Participation Summary:

20 Farmers
125 Number of agricultural educator or service providers reached through education and outreach activities
Education/outreach description:

Farmer involvement with the project is integral to its success, and farmer networks will be utilized to design, implement and share experimental information. In-progress results will be shared via Extension websites, direct-to-farmer workshops, webinars, a “Brainworm Blog”, 4H and FFA youth workshops, and peer-reviewed publications. The project is designed to assist primarily small-scale or beginning farmers, but may also assist wildlife managers who seek to advise the public on the dangers of wildlife feeding. 

  1. Farmer surveys will be distributed via UMaine Extension social media accounts (including livestock owners and the Beginning Farmers Resource Network); responding farmers will be contacted for potential recruitment into the study.
  2. Participating farmers will be visited up to 10 times yearly, at each visit, risk factors and small ruminant health will be discussed.
  3. Survey and other in-progress study results will be posted on the UM VDL website (http://umaine.edu/veterinarylab/ ) as a “Brainworm Blog”.
  4. Online or in-person Extension Small Ruminant Workshops are held 1 to 2 times yearly in Maine; these presentations reach both sheep and goat farmers. This project’s interim and final results will be shared with these audiences. Additional presentations will be made to the Maine Sheep Breeders Association during the Maine Agricultural Trade Show (yearly in January; Augusta, Maine).
  5. One webinar will be held yearly to engage a national audience on this topic; the event will be publicized on eXtension and other sheep and goat websites (e.g,, sheepandgoat.com).
  6. At least one publication will be shared with a wildlife biologist audience via a regional meeting (North East Association of Fish and Wildlife Agencies), as well as the NorthEast Wildlife Disease Cooperative (NWDC), of which the UMaine Veterinary Diagnostic Lab is a member.
  7. Both 4H and Future Farmers of America (FFA) youth workshops on veterinary science are held yearly at the UMaine Veterinary Diagnostic Lab; this project’s findings will provide case-report discussions for teaching purposes.
  8. Final results will be reported to SARE, and will be submitted as peer-reviewed publications to both Extension journals (Extension Risk Management Education and the Journal of Extension), and an open-access journal (such as Small Ruminant Research, a One Health journal, and/or a wildlife journal). Further outreach to farmers will consist of a follow-up survey to evaluate impacts of the study, and will be designed to best address preferences indicated by the study. For instance, farmers may prefer to engage in online educational efforts about reducing parasite risks, versus engaging in workshops. Farmers may be interested in using innovative methods, such as working with drone-based farm risk assessment to design livestock holding/pasture areas. The educational products of this study will impact the small ruminant farming community at the student level, such as 4H and FFA students, at the beginning farmer level via BFRN (https://extension.umaine.edu/beginning-farmer-resource-network/ ), and at the practicing small farmer level via direct involvement. Information shared with the wildlife management community may also have the effect of informing policy about deer population management, and creating a bridge between the farmer and local/regional wildlife managers.

In the past year, several presentations and educational abstracts were produced related to this project.

Date

Venue

Product

Spring 2022

UMaine Extension website & newsletter

“Prevention Methods to Reduce Small Ruminant Exposure to Meningeal Worm.”

Jan. 2022

Maine Agricultural Trade Show (virtual)

Presentation, “Assessing Gastropods as Parasite Vectors: Reducing Risks on Maine Farms,” and “Assessing Microplastic Risks in Maine’s Agricultural Systems.”

https://www.maine.gov/dacf/php/nutrient_management/education.shtml

Dec. 2021

Conference for Research Workers in Animal Diseases, Chicago, IL

Poster presentation, “Assessing Gastropods as Parasite Vectors: Reducing Risks on Maine Farms.”

April 2021

UMaine Student Symposium (virtual)

Presentations, “Risk management solutions for brainworm (Parelaphostrongylus tenuis) on farms with domestic livestock,” and, “Control of a Ruminant Pathogen, Parelaphostrongylus tenuis, Using Poultry: Effects of Gastropod Diets on Ducks,”

April 2020

Extension Risk Management Education National Conference, 

Denver, CO (moved online)

Poster presentation, “Grazing with White-tailed Deer: Simple Solutions for Complex Problems.”

https://agrisk.umn.edu/Conferences/Record/2020_extension_risk_management_education_nati 

Jan. 2020

Everyday Farmers Conference (virtual)

Presentation, “Small Ruminant Health.”

Dec 2019

UMaine Extension Cows and Crops  E-Newsletter

Article, Managing Pastures to Reduce Risk of Meningeal Worm ("Brainworm" or Parelaphostrongylus tenuis) Infection in Ruminants

Project Outcomes

3 Farmers reporting change in knowledge, attitudes, skills and/or awareness
1 Farmers changed or adopted a practice
2 Grants applied for that built upon this project
2 Grants received that built upon this project
$840.00 Dollar amount of grants received that built upon this project
5 New working collaborations
Knowledge Gained:

This project has enlightened us to the current need, as well as future research possibilities, of prevention efforts for not just meningeal worm risk reduction, but also for other pests like ticks. During presentations, several people, including agricultural educators, we unaware of the efficiency of poultry on pastures. This provided educational opportunities to highlight this treatment method for gastropods- borne vector control, as well as soil nutrient management. 

This venture has also revealed a need for animal health management and farmer behavior assessment and education across the region. One area of future focus is an effort to bring an experienced group of small ruminant farmers together to form a panel with the purpose of generating information. We hope to create a network of information gathering. Topics could include parasite and disease prevention and treatment, predation conflicts, farm biosecurity, grazing and pasture management, etc. 

An incidental finding if this research was the presence of microplastics within gastropods and livestock and deer feces. This finding generated a further study into the prevalence of larvae and microplastics within gastropods, hypothesizing that the presence of plastics would make the gastropods more susceptible to larval infection. Another effort was the formation and dissemination of a survey for farmers on their attitudes and practices dealing with plastics. This is an important topic with human, animal and ecological significance.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.