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Mann DN, Hobert KT, Biddle AS, Crossley MS. Black soldier fly (Diptera: Stratiomyidae) larvae reduce cyathostomin (Nematoda: Strongylidae) eggs but develop poorly on horse manure. JOURNAL OF ECONOMIC ENTOMOLOGY 2024:toae183. [PMID: 39197658 DOI: 10.1093/jee/toae183] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2024] [Revised: 07/08/2024] [Accepted: 08/01/2024] [Indexed: 09/01/2024]
Abstract
Cyathostomins are common digestive tract parasites of grazing horses that spread through contact with horse feces. Horse feces are colonized by a variety of organisms, some of which could serve to reduce parasite loads in horse pastures. Black soldier fly (Hermetia illucens L.; Diptera: Stratiomyidae) larvae (BSFL) could be an ideal candidate for biological control of cyathostomins, due to their near-global distribution, low risk of pathogen transmission, ability to develop on a variety of nutrient-poor substrates (including horse manure), and dramatic effect on microbial communities that cyathostomins depend on. Here, using controlled feeding bioassays, we evaluated the effect of BSFL on cyathostomin egg densities in horse manure while also tracking BSFL performance on manure relative to standard grain-based diets. We found that BSFL consumed less substrate, were slower to reach the prepupal stage, and ultimately yielded less biomass when reared on horse manure compared to grain-based diets. However, BSFL reduced average cyathostomin egg densities in horse manure by over 3-fold. Overall, our results suggest that despite horse manure being a poor substrate for BSFL growth, BSFL effectively reduce cyathostomin egg loads in infected horse manure, though the mechanisms by which they do this are uncertain. While BSFL are known to transform the microbial communities within a diversity of rearing substrates, their effect on larger, parasitic organisms in animal manures may be underappreciated. Promoting the decomposition of infected horse manure with BSFL might be a promising approach to managing parasite populations among grazing horses.
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Affiliation(s)
- Destiny N Mann
- Department of Entomology and Wildlife Ecology, University of Delaware, Newark, DE, USA
| | - Kasey T Hobert
- Department of Food and Animal Sciences, University of Delaware, Newark, DE, USA
| | - Amy S Biddle
- Department of Food and Animal Sciences, University of Delaware, Newark, DE, USA
| | - Michael S Crossley
- Department of Entomology and Wildlife Ecology, University of Delaware, Newark, DE, USA
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Molento MB, Pires LSA, Dall'Anese J, Yoshitani UY, Almeida T. Prevalence and risk factors of gastrointestinal helminths infection in Brazilian horses: A retrospective study of a 12-year (2008-2019) diagnostic data. Res Vet Sci 2024; 173:105272. [PMID: 38718543 DOI: 10.1016/j.rvsc.2024.105272] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Revised: 02/29/2024] [Accepted: 04/14/2024] [Indexed: 05/19/2024]
Abstract
Understanding gastrointestinal parasite distribution is crucial for effective control programs in horses. This study reports the prevalence of helminth infections in horses and selected risk factors (i.e., breed, age, climate, season) by analyzing 19,276 fecal samples from the Laboratory of Veterinary Clinical Parasitology, in Curitiba, Southern Brazil. The analyses were carried out from 2008 to 2019, coming from 153 stud farms located in 60 municipalities of nine Brazilian states. The parasite prevalence was 73.3%, with 72.1% present in the adult population and 80.6% in young horses. Strongyles were present in 100% horse farms. Strongyles had a prevalence of 72.1% with a mean FEC of 453.53 (+/- 717.6). Parascaris spp. had a prevalence of 5.8% and a FEC of 17.11 (+/- 149.2). The tropical wet/monsoon climate (Am) showed the lowest FEC for strongyles and Parascaris spp. when compared to the other climates. In the logistic regression analysis, young horses exhibited 4.6 times higher odds ratio (OR) (3.9-5.5) of Parascaris spp. and 1.2 (1.1-1.4) times higher OR of strongyles egg shedding when compared to adults (P < 0.001). Summer presented a higher risk for Parascaris spp. and Strongyles eggs when compared to the other seasons (P < 0.001). Mangalarga Marchador, Criollo, and Crossbred breeds were identified with higher OR of Parascaris spp. egg shedding than Thoroughbred. The extensive prevalence of strongyles across ages, seasons, breeds, and climates alerts for the risk of clinical manifestations in equines raised on pastures designing optimal health management and parasite control strategies worldwide.
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Affiliation(s)
- Marcelo Beltrão Molento
- Laboratory of Veterinary Clinical Parasitology, Department of Veterinary Medicine, Federal University of Paraná, Rua dos Funcionários, 1540, Curitiba, PR CEP: 80035-050, Brazil.
| | - Luciana S A Pires
- Laboratory of Veterinary Clinical Parasitology, Department of Veterinary Medicine, Federal University of Paraná, Rua dos Funcionários, 1540, Curitiba, PR CEP: 80035-050, Brazil
| | - Julia Dall'Anese
- Laboratory of Veterinary Clinical Parasitology, Department of Veterinary Medicine, Federal University of Paraná, Rua dos Funcionários, 1540, Curitiba, PR CEP: 80035-050, Brazil
| | - Ursula Y Yoshitani
- Laboratory of Veterinary Clinical Parasitology, Department of Veterinary Medicine, Federal University of Paraná, Rua dos Funcionários, 1540, Curitiba, PR CEP: 80035-050, Brazil
| | - Thayany Almeida
- Laboratory of Veterinary Clinical Parasitology, Department of Veterinary Medicine, Federal University of Paraná, Rua dos Funcionários, 1540, Curitiba, PR CEP: 80035-050, Brazil
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Nielsen MK, Slusarewicz P, Kuzmina TA, Denwood MJ. US-wide equine strongylid egg count data demonstrate seasonal and regional trends. Parasitology 2024; 151:579-586. [PMID: 38629125 PMCID: PMC11428020 DOI: 10.1017/s0031182024000489] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2024] [Accepted: 04/08/2024] [Indexed: 05/07/2024]
Abstract
Equine strongylid parasites are ubiquitous around the world and are main targets of parasite control programmes. In recent years, automated fecal egg counting systems based on image analysis have become available allowing for collection and analysis of large-scale egg count data. This study aimed to evaluate equine strongylid fecal egg count (FEC) data generated with an automated system over three years in the US with specific attention to seasonal and regional trends in egg count magnitude and sampling activity. Five US regions were defined; North East, South East, North Central, South Central and West. The data set included state, region and zip code for each FEC. The number of FECs falling in each of the following categories were recorded: (1) 0 eggs per gram (EPG), (2) 1 ⩽ 200 EPG, (3) 201 ⩽ 500 EPG and (4) >500 EPG. The data included 58 329 FECs. A fixed effects model was constructed fitting the number of samples analysed per month, year and region, and a mixed effects model was constructed to fit the number of FECs falling in each of the 4 egg count categories defined above. The overall proportion of horses responsible for 80% of the total FEC output was 18.1%, and this was consistent across years, months and all regions except West, where the proportion was closer to 12%. Statistical analyses showed significant seasonal trends and regional differences of sampling frequency and FEC category. The data demonstrated that veterinarians tended to follow a biphasic pattern when monitoring strongylid FECs in horses, regardless of location.
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Affiliation(s)
- Martin K. Nielsen
- M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, Kentucky, USA
| | - Paul Slusarewicz
- Parasight System, Inc, 1532 North Limestone Road, Lexington, Kentucky, USA
| | - Tetiana A. Kuzmina
- I.I. Schmalhausen Institute of Zoology NAS of Ukraine, Bogdan Khmelnytsky Street 15, Kyiv, Ukraine
- Institute of Parasitology, Slovak Academy of Science, Hlinkova 3, Košice 04001, Slovak Republic
| | - Matthew J. Denwood
- Department of Veterinary and Animal Sciences, University of Copenhagen, Denmark
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Hamad MH, Islam SI, Jitsamai W, Chinkangsadarn T, Naraporn D, Ouisuwan S, Taweethavonsawat P. Metabarcoding study to reveal the structural community of strongylid nematodes in domesticated horses in Thailand. BMC Vet Res 2024; 20:70. [PMID: 38395874 PMCID: PMC10893705 DOI: 10.1186/s12917-024-03934-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Accepted: 02/12/2024] [Indexed: 02/25/2024] Open
Abstract
BACKGROUND Mixed strongylid infections significantly impact equine health and performance. Traditional microscopy-based methods exhibit limitations in accurately identifying strongylid species. Nemabiome deep amplicon sequencing approach previously succeeded in describing the strongylid communities in livestock including equids. However, there are no available studies that describe the structural communities of strongylid parasites in horses in Thailand. Therefore, this study was undertaken encompassing the ITS-2 rDNA metabarcoding assay to characterize strongylid species within horse fecal samples collected from a cohort of yearlings at the largest domesticated stud farm in Thailand. In addition, to investigate the capability of ITS-2 rDNA in assessing the phylogenetic relationships among the identified strongylid species. RESULTS The study identified 14 strongylid species in the examined equine populations, each with varying prevalence. Notably, Cylicocyclus nassatus and Cylicostephanus longibursatus were identified as the predominant species, with Strongylus spp. conspicuously absent. The phylogenetic analysis of 207 amplicon sequence variants (ASVs) displayed a complex relationship among the investigated cyathostomin species, with some species are positioned across multiple clades, demonstrating close associations with various species and genera. CONCLUSION The ITS-2 nemabiome sequencing technique provided a detailed picture of horse strongylid parasite species in the studied population. This establishes a foundation for future investigations into the resistance status of these parasites and enables efforts to mitigate their impact.
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Affiliation(s)
- Mohamed H Hamad
- The International Graduate Program of Veterinary Science and Technology (VST), Faculty of Veterinary Science, Chulalongkorn University, Bangkok, 10330, Thailand
- Infectious Diseases, Department of Animal Medicine, Faculty of Veterinary Medicine, Zagazig University, Zagazig, 44511, Egypt
- Parasitology Unit, Department of Veterinary Pathology, Faculty of Veterinary Science, Chulalongkorn University, Bangkok, 10330, Thailand
| | - Sk Injamamul Islam
- The International Graduate Program of Veterinary Science and Technology (VST), Faculty of Veterinary Science, Chulalongkorn University, Bangkok, 10330, Thailand
- Parasitology Unit, Department of Veterinary Pathology, Faculty of Veterinary Science, Chulalongkorn University, Bangkok, 10330, Thailand
| | - Wanarit Jitsamai
- Department of Parasitology and Entomology, Faculty of Public Health, Mahidol University, Bangkok, Thailand
| | - Teerapol Chinkangsadarn
- Department of Surgery, Faculty of Veterinary Science, Chulalongkorn University, Bangkok, 10330, Thailand
| | - Darm Naraporn
- Horse Farm and Laboratory Animal Breeding Center, Queen Saovabha Memorial Institute, The Thai Red Cross Society, Hua-Hin, Prachuap Khiri Khan Province, 77110, Thailand
| | - Suraseha Ouisuwan
- Horse Farm and Laboratory Animal Breeding Center, Queen Saovabha Memorial Institute, The Thai Red Cross Society, Hua-Hin, Prachuap Khiri Khan Province, 77110, Thailand
| | - Piyanan Taweethavonsawat
- Parasitology Unit, Department of Veterinary Pathology, Faculty of Veterinary Science, Chulalongkorn University, Bangkok, 10330, Thailand.
- Biomarkers in Animals Parasitology Research Unit, Chulalongkorn University, Bangkok, 10330, Thailand.
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Abbas G, Ghafar A, Beasley A, Stevenson MA, Bauquier J, Koehler AV, Wilkes EJA, McConnell E, El-Hage C, Carrigan P, Cudmore L, Hurley J, Gauci CG, Beveridge I, Jacobson C, Nielsen MK, Hughes KJ, Jabbar A. Understanding temporal and spatial distribution of intestinal nematodes of horses using faecal egg counts and DNA metabarcoding. Vet Parasitol 2024; 325:110094. [PMID: 38091893 DOI: 10.1016/j.vetpar.2023.110094] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2023] [Revised: 11/30/2023] [Accepted: 11/30/2023] [Indexed: 12/25/2023]
Abstract
This study reports the spatial and temporal distribution of ascarid and strongylid nematodes in Thoroughbred horses by age category across different climatic zones in Australia over an 18-month period. Faecal samples (n = 2046) from individual horses were analysed using the modified McMaster technique for faecal egg counts (FECs). Strongylids were identified using PCR-directed next-generation sequencing of the second internal transcribed spacer (ITS-2) of the nuclear ribosomal DNA. Yearlings had the highest prevalence (82%) of strongyle eggs followed by weanlings (79%), foals (58%), wet mares (49%) and dry mares (46%). For Parascaris spp., foals had the highest prevalence (35%) followed by weanlings (21%) and yearlings (10%). The highest mean FECs for Parascaris spp. were observed in foals (525 eggs per gram [EPG] of faeces) while those for strongyles were in yearlings (962 EPG). Among horses that were classified as adults at the time of sampling, 77% (860 of 1119) of mares were low (i.e., <250 EPG) strongyle egg-shedders. Mean strongyle FEC counts were highest in the Mediterranean (818 EPG) followed by summer (599 EPG), winter (442 EPG), and non-seasonal (413 EPG) rainfall zones. Twenty-six nematode species were detected, with Cylicostephanus longibursatus (26.5%), Cylicocyclus nassatus (23.7%) and Coronocyclus coronatus (20.5%) being the most frequently detected species. Their richness and relative abundance varied with horse age, season and climatic zone. In addition, Strongylus equinus and Triodontophorus spp. (T. brevicauda and T. serratus) were also detected. This comprehensive study elucidates spatial (climatic zone) and temporal (i.e., seasonal) trends in prevalence and burdens of intestinal nematodes in Australian horses using non-invasive conventional and molecular methods. The information presented in this study is crucial for developing integrated management strategies to control horse parasites in farmed horses.
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Affiliation(s)
- Ghazanfar Abbas
- Melbourne Veterinary School, The University of Melbourne, Werribee, Victoria 3030, Australia
| | - Abdul Ghafar
- Melbourne Veterinary School, The University of Melbourne, Werribee, Victoria 3030, Australia
| | - Anne Beasley
- School of Agriculture and Food Sustainability, University of Queensland, Gatton, Queensland 4343, Australia
| | - Mark A Stevenson
- Melbourne Veterinary School, The University of Melbourne, Werribee, Victoria 3030, Australia
| | - Jenni Bauquier
- Melbourne Veterinary School, The University of Melbourne, Werribee, Victoria 3030, Australia
| | - Anson V Koehler
- Melbourne Veterinary School, The University of Melbourne, Werribee, Victoria 3030, Australia
| | | | - Emma McConnell
- Centre for Animal Production and Health, Murdoch University, Murdoch, Western Australia, Australia
| | - Charles El-Hage
- Melbourne Veterinary School, The University of Melbourne, Werribee, Victoria 3030, Australia
| | - Peter Carrigan
- Scone Equine Hospital, Scone, New South Wales 2337, Australia
| | - Lucy Cudmore
- Scone Equine Hospital, Scone, New South Wales 2337, Australia
| | - John Hurley
- Swettenham Stud, Nagambie, Victoria 3608, Australia
| | - Charles G Gauci
- Melbourne Veterinary School, The University of Melbourne, Werribee, Victoria 3030, Australia
| | - Ian Beveridge
- Melbourne Veterinary School, The University of Melbourne, Werribee, Victoria 3030, Australia
| | - Caroline Jacobson
- Centre for Animal Production and Health, Murdoch University, Murdoch, Western Australia, Australia
| | - Martin K Nielsen
- M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY, USA
| | - Kristopher J Hughes
- School of Agricultural, Environmental and Veterinary Sciences, Charles Sturt University, Wagga Wagga, New South Wales 2650, Australia
| | - Abdul Jabbar
- Melbourne Veterinary School, The University of Melbourne, Werribee, Victoria 3030, Australia.
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6
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Lüthin S, Zollinger A, Basso W, Bisig M, Caspari N, Eng V, Frey CF, Grimm F, Igel P, Lüthi S, Regli W, Roelfstra L, Rosskopf M, Steiner B, Stöckli M, Waidyasekera D, Waldmeier P, Schnyder M, Torgerson PR, Hertzberg H. Strongyle faecal egg counts in Swiss horses: A retrospective analysis after the introduction of a selective treatment strategy. Vet Parasitol 2023; 323:110027. [PMID: 37837729 DOI: 10.1016/j.vetpar.2023.110027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Revised: 07/17/2023] [Accepted: 09/09/2023] [Indexed: 10/16/2023]
Abstract
The standard parasite management of horses based on regular anthelmintic treatments, now practiced for decades has resulted in a worrying expansion of resistant helminth populations, which may considerably impair control on the farm level. The aim of the present study was to obtain a retrospective (year 2010 - 2016) nationwide analysis of faecal egg count (FEC) data from the Swiss adult horse population, related to horse age and geographic region. Thirteen labs provided a total of 16,387 FEC data of horses aged four to 39 years (average: 13.6 years). The annual number of performed FEC tests increased from 38 to 4,939 within the observation period. Independent of the annual sample size the yearly patterns of the FEC were very similar. Seventy-eight percent (n = 12,840) of the samples were negative and 90 % (n = 14,720) showed a FEC below 200 strongyle eggs per gram (EPG) of faeces. The annual mean strongyle FEC ranged between 60 and 88 EPG with a total mean of 75 EPG. Horses aged 4-7 years showed a significantly (p < 0.00001) higher mean FEC compared with the other age groups, differences were not significant among the older horses. Based on ZIP codes, samples were allocated by 70.0 %, 6.0 % and 0.2 % to the German-, French- and Italian-speaking regions of Switzerland, respectively. With 222 EPG the mean FEC in the French part of Switzerland was significantly higher (p < 0.05) than in the German-speaking region (60 EPG). Eggs of Parascaris spp., anoplocephalids and Strongyloides westeri were found in 0.36 %, 0.32 % and 0.01 % of the samples, respectively. Based on 3,813 questionnaire feedbacks from owners in 2017 covering a total of 12,689 horses, sixty-eight percent (n = 8,476) were dewormed without diagnosis, two percent (n = 240) were not dewormed at all, whereas for 30 % (n = 3,721) the selective anthelmintic treatment (SAT) concept was applied. The SAT implementation rate differed significantly (p < 0.0005) between regions, with 33 %, 20 % and 25 % for the German-, French- and Italian-speaking areas, respectively. The rate of horses spending 16-24 h on pasture per day was significantly higher in the French-speaking region compared to the German-speaking part of Switzerland (p < 0.0001). In addition, pasture hygiene was practiced at a significantly lower rate in the French-speaking part compared to the German- and Italian-speaking regions (both p < 0.0001). Overall, the shift towards the SAT-concept represents a very promising development with respect to mitigating the further spread of anthelmintic resistance.
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Affiliation(s)
- S Lüthin
- Institute of Parasitology, Vetsuisse Faculty, University of Zurich, Winterthurerstrasse 266a, 8057 Zurich, Switzerland
| | - A Zollinger
- Agroscope, Swiss National Stud Farm SNSF, Les Longs-Prés, 1580 Avenches, Switzerland
| | - W Basso
- Institute of Parasitology, Vetsuisse Faculty, University of Berne, Länggass-Strasse 122, 3012 Berne, Switzerland
| | - M Bisig
- Bisig Tierärzte AG, Wildbrunnstrasse 3, 8722 Kaltbrunn, Switzerland
| | - N Caspari
- IDEXX Diavet Labor AG, Schlyffistrasse 10, 8806 Bäch SZ, Switzerland
| | - V Eng
- Tierarztpraxis Arche, Sonnenrain 4, 6133 Hergiswil b. Willisau, Switzerland
| | - C F Frey
- Institute of Parasitology, Vetsuisse Faculty, University of Berne, Länggass-Strasse 122, 3012 Berne, Switzerland
| | - F Grimm
- Institute of Parasitology, Vetsuisse Faculty, University of Zurich, Winterthurerstrasse 266a, 8057 Zurich, Switzerland
| | - P Igel
- Tierärztliche Gemeinschaftspraxis Zücken, Zückerain 5, 6017 Ruswil, Switzerland
| | - S Lüthi
- Tierarztpraxis Dr. med. vet. Sybil Lüthi, Attenreute 6, 9315 Neukirch (Egnach), Switzerland
| | - W Regli
- Labor Zentral, Stationsweg 3, 6232 Geuensee, Switzerland
| | - L Roelfstra
- Animal Diagnostic Sàrl, Avenue de Beauregard 28, 2036 Cormondrèche, Switzerland
| | - M Rosskopf
- IDEXX Diavet Labor AG, Schlyffistrasse 10, 8806 Bäch SZ, Switzerland
| | - B Steiner
- Zoetis Schweiz GmbH, Rue de la Jeunesse 2, 2800 Delémont, Switzerland
| | - M Stöckli
- Pferdeklinik Dalchenhof, Talchenweg 7, 4805 Brittnau, Switzerland
| | - D Waidyasekera
- Tierarztpraxis am Pfannenstil, Zelgmatt 69, 8132 Egg b. Zürich, Switzerland
| | - P Waldmeier
- Tierarztpraxis Waldmeier GmbH, Hauptstrasse 15, 5273 Oberhofen AG, Switzerland
| | - M Schnyder
- Institute of Parasitology, Vetsuisse Faculty, University of Zurich, Winterthurerstrasse 266a, 8057 Zurich, Switzerland
| | - P R Torgerson
- Section of Epidemiology, Vetsuisse Faculty, University of Zurich, Winterthurerstrasse 270, 8057 Zurich, Switzerland
| | - H Hertzberg
- Institute of Parasitology, Vetsuisse Faculty, University of Zurich, Winterthurerstrasse 266a, 8057 Zurich, Switzerland; Health Balance Tiergesundheit, Flawilerstrasse 35, 9244 Niederuzwil, Switzerland.
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Nielsen MK, Leathwick DM, Sauermann CW. Shortened strongylid egg reappearance periods in horses following macrocyclic lactone administration - The impact on parasite dynamics. Vet Parasitol 2023; 320:109977. [PMID: 37352579 DOI: 10.1016/j.vetpar.2023.109977] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Revised: 06/16/2023] [Accepted: 06/17/2023] [Indexed: 06/25/2023]
Abstract
Over the past three decades, equine strongylid egg reappearance periods (ERPs) have shortened substantially for macrocyclic lactone anthelmintics. The ERPs of ivermectin and moxidectin were originally reported in the 8-10 and 12-16 week ranges, respectively, but several recent studies have found them to be around 4-5 weeks for both actives. This loss of several weeks of suppressed strongylid egg output could have substantial implications for parasite control. This study made use of a computer simulation model to evaluate the impact of shortened ERPs on the anthelmintic performance of ivermectin and moxidectin against equine cyathostomins. The original ERPs were set to 7.1 and 15.4 weeks for ivermectin and moxidectin, respectively, while the reduced ERP was set to 4.6 weeks for both actives. Simulations were set to compare model outputs between original and reduced ERP scenarios and results expressed as percent increase in strongylid egg output, infective third stage larvae on herbage (L3h), and encysted early third stage larvae (EL3). For each drug, simulations were evaluated for two different treatment scenarios (2 and 4 treatments annually), two different age groups (yearlings and adults), and for four different climates (cold humid continental, temperate oceanic, humid subtropical, and hot/cold semi-arid). Across all simulations, there was a substantial increase of the three evaluated parameters. With the ivermectin simulations, all three parameters increased in the 100-300% range across climates, age groups and treatment intensities. The moxidectin simulations displayed a wider range of results with parameters increasing from a few hundred to several thousand percent. The increases were most pronounced for L3h in the two cooler climates, reaching as high as 6727%. Overall, the loss of anthelmintic performance was at a magnitude of 10 times larger for moxidectin compared to ivermectin. This performance loss was climate dependent, and was also affected by treatment intensity, but not by horse age. This is the first study to evaluate consequences of shortened ERPs in horses and demonstrated a substantial loss in anthelmintic performance resulting from this development. The results illustrate that anthelmintic efficacy is more than the percent reduction of fecal egg counts at 14 days post treatment, and that substantial anthelmintic performance can be lost despite FECRTs remaining at 100%.
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Affiliation(s)
- Martin K Nielsen
- M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY, USA.
| | - Dave M Leathwick
- AgResearch Grasslands, Private Bag, 11008, Palmerston North 4442, New Zealand
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8
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Three-year study to evaluate an anthelmintic treatment regimen with reduced treatment frequency in horses on two study sites in Belgium. Vet Parasitol 2021; 298:109538. [PMID: 34364153 DOI: 10.1016/j.vetpar.2021.109538] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Revised: 07/23/2021] [Accepted: 07/24/2021] [Indexed: 11/23/2022]
Abstract
In the present study, an anthelmintic treatment regimen with reduced treatment frequency was evaluated in horses on two study sites in Belgium during three consecutive summer pasture seasons. Historically, the horses on both study sites were treated up to 6 times a year with ivermectin (IVM) or up to 4 times a year with moxidectin (MOX), and previous efficacy evaluations indicated a reduced egg reappearance period in some of the treated horses for both IVM (28 days) and MOX (42 days). In the present study, all horses were treated with IVM or MOX in the spring and in autumn. Faecal egg counts (FEC) were conducted every two weeks during the summer pasture season and whenever the individual FEC exceeded 250 eggs per gram of faeces, the specific horse was treated with pyrantel embonate. No increase in parasitic disease over the three-year period of the study was observed. The FEC data collected in the study as well as the age of the animals and local weather data were then imported into a cyathostomin life-cycle model, to evaluate long term effects of the newly applied treatment regimen on the selection pressure for anthelmintic resistance, and compare to the previous high frequency treatment regimen. The model simulations indicated that the whole-herd treatment regimen with at least 4 macrocyclic lactone treatments annually led 2-3 times faster resistance development than any of the alternative treatment regimens evaluated under the specific conditions of these two study sites. Further lowering the treatment frequency or applying even more selective treatments enhanced the delay in resistance development, but to a lesser extent.
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9
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Nielsen MK, Martin AN, Scare JA, Steuer AE. Precision and spatial variation of cyathostomin mucosal larval counts. Vet Parasitol 2021; 290:109349. [PMID: 33482426 DOI: 10.1016/j.vetpar.2021.109349] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 12/18/2020] [Accepted: 12/19/2020] [Indexed: 11/26/2022]
Abstract
Cyathostomins are pervasive parasites of equids across the world. Larval stages encyst in the mucosa of the cecum, ventral and dorsal colon and can induce an inflammatory response leading to larval cyathostominosis, a life-threatening generalized typhlocolitis. Mucosal digestion is the only gold standard procedure for identifying and quantifying all larval stages. There is a lack of standardization of this technique and several aspects are ambiguous, such as precision of the method and the possibility of spatial variation of mucosal larval counts. The aim of this study was to estimate precision for enumeration of early third stage larvae (EL3) and late third stage/fourth stage (LL3/L4) larvae and investigate spatial variation of encysted counts within large intestinal organs. Six naturally infected and untreated horses aged 2-5 years were euthanized as part of an anthelmintic efficacy study, and the cecum (Cec), ventral colon (VC) and dorsal colon (DC) were collected. Each organ was rinsed, weighed, and visually separated into 3 equally sized sections. Two 5% tissue samples were collected from each section, a total of six replicates per organ. The mucosae were digested, and 2% examined under the microscope for presence of EL3 and LL3/L4 stage larvae. Overall, 59 % of the harvested larvae were EL3s, and 41 % were LL3/L4s. The ventral colons represented 45 % of the total organ weight, and contributed 37 and 41 % of the EL3s and LL3/L4s harvested, respectively. The Cec, representing only 27 % of the weight contributed 23 % of EL3s and 47 % of LL3/L4s. The DC represented 28 % of the total organ weight, and 28 % and 12 % of the total EL3s and LL3/L4s, respectively. Coefficients of variation varied from 33 to 183 % for EL3 counts and 38-245% for LL3/L4 counts. There were no statistically significant associations between EL3 counts and either organ or location. For LL3/L4 counts there were no statistically significant differences between the three locations within organs (p = 0.1166), but the DC had significantly lower counts than the other two organs (p < 0.0001). Increasing the number of mucosal replicates from each organ improved estimation, but required a considerably increased workload. In conclusion, mucosal larval cyathostomin counts are highly variable, complicating their use for treatment efficacy estimation.
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Affiliation(s)
- Martin K Nielsen
- M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY, USA.
| | - Avery N Martin
- M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY, USA
| | - Jessica A Scare
- Department of Agriculture, Eastern Kentucky University, Richmond, KY, USA
| | - Ashley E Steuer
- Texas Tech University, School of Veterinary Medicine, Amarillo, TX, USA
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Sauermann CW, Leathwick DM, Lieffering M, Nielsen MK. Climate change is likely to increase the development rate of anthelmintic resistance in equine cyathostomins in New Zealand. INTERNATIONAL JOURNAL FOR PARASITOLOGY-DRUGS AND DRUG RESISTANCE 2020; 14:73-79. [PMID: 32992276 PMCID: PMC7527676 DOI: 10.1016/j.ijpddr.2020.09.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 09/13/2020] [Accepted: 09/13/2020] [Indexed: 11/30/2022]
Abstract
Climate change is likely to influence livestock production by increasing the prevalence of diseases, including parasites. The traditional practice of controlling nematodes in livestock by the application of anthelmintics is, however, increasingly compromised by the development of resistance to these drugs in parasite populations. This study used a previously developed simulation model of the entire equine cyathostomin lifecycle to investigate the effect a changing climate would have on the development of anthelmintic resistance. Climate data from six General Circulation Models based on four different Representative Concentration Pathways was available for three New Zealand locations. These projections were used to estimate the time resistance will take to develop in the middle (2040–49) and by the end (2090–99) of the century in relation to current (2006–15) conditions under two treatment scenarios of either two or six yearly whole-herd anthelmintic treatments. To facilitate comparison, a scenario without any treatments was included as a baseline. In addition, the size of the infective and parasitic stage nematode population during the third simulation year were estimated. The development of resistance varied between locations, time periods and anthelmintic treatment strategies. In general, the simulations indicated a more rapid development of resistance under future climates coinciding with an increase in the numbers of infective larvae on pasture and encysted parasitic stages. This was especially obvious when climate changes resulted in a longer period suitable for development of free-living parasite stages. A longer period suitable for larval development resulted in an increase in the average size of the parasite population with a larger contribution from eggs passed by resistant worms surviving the anthelmintic treatments. It is projected that climate change will decrease the ability to control livestock parasites by means of anthelmintic treatments and non-drug related strategies will become increasingly important for sustainable parasite control. The development of anthelmintic resistance under climate change was simulated. Climate can become more suitable for parasite development, increasing population size. The time resistance took to develop was linked to changes in parasite population size. Non-drug related strategies will become increasingly important for parasite control.
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Affiliation(s)
- Christian W Sauermann
- AgResearch, Grasslands Research Centre, Private Bag 11008, Palmerston North, 4442, New Zealand.
| | - Dave M Leathwick
- AgResearch, Grasslands Research Centre, Private Bag 11008, Palmerston North, 4442, New Zealand
| | - Mark Lieffering
- AgResearch, Grasslands Research Centre, Private Bag 11008, Palmerston North, 4442, New Zealand
| | - Martin K Nielsen
- M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY, USA
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11
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Scare JA, Leathwick DM, Sauermann CW, Lyons ET, Steuer AE, Jones BA, Clark M, Nielsen MK. Dealing with double trouble: Combination deworming against double-drug resistant cyathostomins. INTERNATIONAL JOURNAL FOR PARASITOLOGY-DRUGS AND DRUG RESISTANCE 2019; 12:28-34. [PMID: 31883485 PMCID: PMC7139983 DOI: 10.1016/j.ijpddr.2019.12.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Revised: 12/12/2019] [Accepted: 12/12/2019] [Indexed: 12/03/2022]
Abstract
An alternative control regimen for drug-resistant parasites is combination deworming, where two drugs with different modes of action are administered simultaneously to target the same parasite. Few studies have investigated this in equine cyathostomins. We previously reported that an oxibendazole (OBZ) and pyrantel pamoate (PYR) combination was not sustainable against a cyathostomin population with high levels of OBZ and PYR resistance. This study consisted of a field study and two computer simulations to evaluate the efficacy of a moxidectin-oxibendazole (MOX-OBZ) combination against the same cyathostomin population. In the field study, anthelmintic treatments occurred when ten horses exceeded 100 eggs per gram. Fecal egg counts and efficacy evaluations were performed every two weeks. The two simulations utilized weather data as well as equine and parasite population parameters from the field study. The first simulation repeated the treatment schedule used in the field study over a 40 year period. The second evaluated efficacies of combination treatments using selective therapy over 40 years. In the field study, efficacies of MOX and both combination treatments were 100%. The egg reappearance period for MOX was 16 weeks, and the two combination treatments were 12 and 18 weeks. The first (46.7%) and last (40.1%) OBZ efficacies were not significantly different from each other. In the simulation study, the combination treatment delayed MOX resistance development compared to when MOX was used as a single active. This occurred despite the low efficacy of OBZ. The second set of simulations identified combination treatments used with selective therapy to be the most effective at delaying MOX resistance. Overall, this study supports the use of combination treatment against drug-resistant cyathostomins, when one of the actives exhibits high efficacy, and demonstrates benefits of this approach despite substantially lowered efficacy of the other active ingredient. Oxibendazole-moxidectin combination treatments were 100% effective. Oxibendazole efficacies (<50%) did not differ pre and post combination treatment. The model observed oxibendazole-moxidectincombinationto delaymoxidectin resistance. Combination use in selective therapy delayed resistance most effectively.
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Affiliation(s)
- J A Scare
- M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY, USA.
| | - D M Leathwick
- AgResearch, Grasslands Research Centre, Private Bag 11008, Palmerston North, 4442, New Zealand
| | - C W Sauermann
- AgResearch, Grasslands Research Centre, Private Bag 11008, Palmerston North, 4442, New Zealand
| | - E T Lyons
- M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY, USA
| | - A E Steuer
- M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY, USA
| | - B A Jones
- College of Veterinary Medicine, Lincoln Memorial University, Harrogate, TN, USA
| | - M Clark
- College of Veterinary Medicine, Lincoln Memorial University, Harrogate, TN, USA
| | - M K Nielsen
- M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY, USA
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Leathwick DM, Sauermann CW, Nielsen MK. Managing anthelmintic resistance in cyathostomin parasites: Investigating the benefits of refugia-based strategies. INTERNATIONAL JOURNAL FOR PARASITOLOGY-DRUGS AND DRUG RESISTANCE 2019; 10:118-124. [PMID: 31491731 PMCID: PMC6731328 DOI: 10.1016/j.ijpddr.2019.08.008] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Revised: 08/27/2019] [Accepted: 08/27/2019] [Indexed: 02/05/2023]
Abstract
Selective anthelmintic therapy has been recommended as a sustainable strategy for cyathostomin control in horse populations for several decades. The traditional approach has been to determine strongyle fecal egg counts (FEC) for all horses, with treatment only recommended for those exceeding a predetermined threshold. The aims are to achieve a reduction of overall egg shedding, while leaving a proportion of the herd untreated, which lowers anthelmintic treatment intensity and reduces selection pressure for development of anthelmintic resistance. This study made use of the cyathostomin model to evaluate the influence of treatment strategies with between 1 and 8 yearly treatment occasions, where either 1) all horses were treated, 2) a predetermined proportion of the herd remained untreated, or 3) horses were treated if their FEC exceeded thresholds between 100 and 600 strongyle eggs per gram. Weather data representing four different climatic zones was used and three different herd age structures were compared; 1) all yearlings, 2) all mature horses 10-20 years old, and 3) a mixed age structure of 1-20 years of age. Results indicated a consistent effect of age structure, with anthelmintic resistance developing quickest in the yearling group and slowest among the mature horses. Development of anthelmintic resistance was affected by treatment intensity and selective therapy generally delayed resistance. Importantly, the results suggest that the effects of selective therapy on resistance development are likely to vary between climatic zones and herd age structures. Overall, a substantial delaying of resistance development requires that the average number of treatments administered annually across a herd of horses needs to be about two or less. However, results also indicate that an age-structured prioritisation of treatment to younger horses should still be effective. It appears that a 'one-size-fits-all' approach to the management of anthelmintic resistance in cyathostomins is unlikely to be optimal.
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Affiliation(s)
- Dave M Leathwick
- AgResearch, Grasslands Research Centre, Private Bag 11008, Palmerston North, 4442, New Zealand.
| | - Christian W Sauermann
- AgResearch, Grasslands Research Centre, Private Bag 11008, Palmerston North, 4442, New Zealand
| | - Martin K Nielsen
- M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY, USA
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13
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Zynda HM, Scare JA, Steuer AE, Anderson HP, Nielsen MK. Encysted cyathostomin larval counts: Mucosal digestion revisited. Vet Parasitol 2019; 273:86-89. [PMID: 31449972 DOI: 10.1016/j.vetpar.2019.08.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Revised: 08/14/2019] [Accepted: 08/19/2019] [Indexed: 11/18/2022]
Abstract
Cyathostomins are pervasive equine parasites in horses across the world, and larval stages are known to cause the deadly disease larval cyathostominosis. The mucosal digestion technique is widely used for enumeration of encysted larval stages. Previous studies have investigated the spatial variation of encysted larvae, however current protocols lack a description of a standardized area from which to take the tissue sample. This study sought to evaluate spatial variation in encysted cyathostomin larval counts among the large intestinal organs and their subsections. Following humane euthanasia, ceca, ventral, and dorsal colons were harvested from 8 foals (aged 4-8 months) raised in an anthelmintic naïve parasitology research herd. Each organ was weighed and separated into 3 equal sections by length: the orad, intermediate, and aborad portions. From each of those sections, two 5% weight tissue samples were collected and digested to quantify the early third stage larvae (EL3) and late third stage larvae/fourth stage larvae (LL3/L4). A mixed model statistical analysis was carried out to evaluate for differences of larval counts among the different organs, sections, and the interaction term between the organs and sections. There were significant differences among organs (P < 0.0001), with the ceca having higher counts than the ventral and dorsal colons. However, there were no significant differences among the three defined organ sections (P = 0.1076). Coefficients of variation (CV) were all calculated to be greater than 1, suggesting a high level of variability among the samples; the least amount of variation can be found in the cecal data with a CV of 1.4024 compared with the ventral colon's 1.529845 and dorsal colon's 3.339135 within the respective organ. The following sections had the highest mean counts of encysted larvae: intermediate cecum, orad ventral colon, and aborad dorsal colon. Though only a portion of the results were significant, trends were observed and these should be investigated further in future studies and potentially employed in larvicidal efficacy evaluations.
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Affiliation(s)
- Haley M Zynda
- M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, Kentucky, USA.
| | - Jessica A Scare
- M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, Kentucky, USA
| | - Ashley E Steuer
- M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, Kentucky, USA
| | - Haley P Anderson
- M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, Kentucky, USA
| | - Martin K Nielsen
- M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, Kentucky, USA
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Sauermann CW, Nielsen MK, Luo D, Leathwick DM. Modelling the development of anthelmintic resistance in cyathostomin parasites: The importance of genetic and fitness parameters. Vet Parasitol 2019; 269:28-33. [PMID: 31079825 DOI: 10.1016/j.vetpar.2019.04.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Revised: 04/13/2019] [Accepted: 04/16/2019] [Indexed: 11/18/2022]
Abstract
Previously described models for the free-living and parasitic phases of the cyathostomin life-cycle were combined into a single model for the complete life-cycle. The model simulates a single free-living population on pasture utilising parasite egg output from the horses and localised temperature and rainfall data to estimate infective larval density on herbage. Multiple horses of different ages are possible, each with an individualised anthelmintic treatment programme. Genotypes for anthelmintic resistance are included allowing for up to three resistance genes with 2 alleles each. Because little is known of the genetics of resistance to anthelmintics in cyathostomins, the first use of this model was to compare the effect of different assumptions regarding the inheritance of resistance on model outputs. Comparisons were made between single and two-gene inheritance, where the heterozygote survival was dominant, intermediate or recessive under treatment, and with or without a fitness disadvantage associated with the resistance mechanism. Resistance developed fastest when the heterozygotes survived anthelmintic treatment (i.e., were dominant) and slowest when they did not (i.e., were recessive). Resistance was slower to develop when inheritance was poly-genic compared to a single gene, and when there was a fitness cost associated with the resistance mechanism, although the latter variable was the least influential. Importantly, while these genetic factors sometimes had a large influence on the rate at which resistant genotypes built up in the model populations, their order of ranking was always the same, when different anthelmintic use strategies were compared. Therefore, the described model is a useful tool for evaluating different treatment and management strategies on their potential to select for resistance.
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Affiliation(s)
| | - Martin K Nielsen
- M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, Kentucky, USA
| | - Dongwen Luo
- AgResearch Grasslands, Private Bag 11008, Palmerston North, 4442, New Zealand
| | - Dave M Leathwick
- AgResearch Grasslands, Private Bag 11008, Palmerston North, 4442, New Zealand
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15
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Nielsen MK, Sauermann CW, Leathwick DM. The effect of climate, season, and treatment intensity on anthelmintic resistance in cyathostomins: A modelling exercise. Vet Parasitol 2019; 269:7-12. [PMID: 31079830 DOI: 10.1016/j.vetpar.2019.04.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Revised: 04/01/2019] [Accepted: 04/06/2019] [Indexed: 10/27/2022]
Abstract
Anthelmintic resistance is widespread in equine cyathostomin populations across the world, and with no new anthelmintic drug classes in the pharmaceutical pipeline, the equine industry is forced to abandon traditional parasite control regimens. Current recommendations aim at reducing treatment intensity and identifying high strongylid egg shedders in a targeted treatment approach. But, virtually nothing is known about the effectiveness of these recommendations, nor their applicability to different climatic regions, making it challenging to tailor sustainable recommendations for equine parasite control. This study made use of a computer model of the entire cyathostomin life-cycle to evaluate the influence of climate and seasonality on the development of anthelmintic resistance in cyathostomin parasites. Furthermore, the study evaluated the impact of recommended programs involving selective anthelmintic therapy on delaying anthelmintic resistance development. All simulations evaluated the use of a single anthelmintic (i.e., ivermectin) over the course of 40 model years. The study made use of weather station data representing four different climatic zones: a cold humid continental climate, a temperate oceanic climate, a cold semi-arid climate, and a humid subtropical climate. Initially, the impact of time of the year was evaluated when a single anthelmintic treatment was administered once a year in any of the twelve months. The next simulations evaluated the impact of treatment intensities varying between 2 and 6 treatments per year. And finally, we evaluated treatment schedules consisting of a combination of strategic treatments administered to all horses and additional treatments administered to horses exceeding a predetermined fecal egg count threshold. Month of treatment had a large effect on resistance development in colder climates, but little or no impact in subtropical and tropical climates. Resistance development was affected by treatment intensity, but was also strongly affected by climate. Selective therapy delayed resistance development in all modelled scenarios, but, again, this effect was climate dependent with the largest delays observed in the colder climates. This study is the first to demonstrate the value of cyathostomin parasite refugia in managing anthelmintic resistance, and also that climate and seasonality are important. This modelling exercise has allowed an illustration of concepts believed to play important roles in anthelmintic resistance in equine cyathostomins, but has also identified knowledge gaps and new questions to address in future studies.
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Affiliation(s)
- Martin K Nielsen
- M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY, USA.
| | | | - Dave M Leathwick
- AgResearch Grasslands, Private Bag 11008, Palmerston North, 4442, New Zealand
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