Shortened strongyle-type egg reappearance periods in naturally infected horses treated with moxidectin and failure of a larvicidal dose of fenbendazole to reduce fecal egg counts

Rossano, M.G.; Smith, A.R.; Lyons, E. T.

doi:10.1016/j.vetpar.2010.07.001

Cited by 60 publications

(43 citation statements)

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“…In the Lexington, Kentucky area and several other geographic locations worldwide where chemical control of parasites has been used routinely, small strongyles are resistant to fenbendazole, oxibendazole, and pyrantel pamoate (Kaplan et al 2004). Also, ivermectin and moxidectin are becoming less effective on small strongyles (Lyons et al 2011;Molento et al 2008;Rossano et al 2010;Samson-Himmelstjerna et al 2007). Additionally, in many places, ivermectin and moxidectin essentially are ineffective against ascarids (78) 108 (22) a All Thoroughbreds from the 24 farms sampled with this breed b All Standardbreds from the one farm (DM) sampled with this breed c All mixed light horses from the one farm (VS) sampled with these types (Parascaris equorum) now (Boersema et al 2002;Hearn and Peregrine 2003;Stoneham and Coles 2006;Schougaard and Nielsen 2007;Slocombe et al 2007;Reinemeyer 2009a).…”

Section: Discussionmentioning

confidence: 99%

Investigation of strongyle EPG values in horse mares relative to known age, number positive, and level of egg shedding in field studies on 26 farms in Central Kentucky (2010–2011)

2011

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A parasite study was done in 1,300 horse mares on 26 farms in Central Kentucky over a 5-month period in 2010 and 2011. The mares included 1,114 Thoroughbreds (TB) on 24 farms, 64 Standardbreds (SB) on 1 farm, and 122 mixed light horse types (MLH) on 1 farm. The objective of this research was to determine strongyle eggs per gram of feces (EPG) counts for evaluation by known age, number positive, and level of egg shedding by the mares. This was done to establish strongyle EPG profiles for the mares to aid in determining whether antiparasitic treatment was necessary. Eggs found were considered those of small strongyles. (A) For the Thoroughbred mares, (1) 362 (32%) were EPG-positive, and (2) the average (percentage) of EPG-positive mares by year of age was 3-5 (54%), 6-10 (36%), 11-15 (24%), 16-20 (17%), and >20 (21%); (3) EPG average counts were similar for all age categories except for the 6- to 10-year-olds, which were higher; (4) and the average (percentage) of positive mares by 100 units of EPG counts was ≤100 (50%), ≤200 (62%), ≤300 (70%), ≤400 (76%), ≤500 (80%), and >500 (20%). (B) For the Standardbred mares, 31 (48%) were EPG-positive; (2) the average (percentage) of EPG-positive mares by year of age (no >20 sampled) was lowest for the 3-5 and 16-20 categories and highest for the 6-10 and 11-15 groups; (3) EPG average counts by years of age were lowest for 3-5, 11-15, and 16-20 groups and highest for the 6-10 group; and (4) the average (percentage) of positive mares by 100 units of EPGs was 62% for the ≤100 category, 71-84% for ≤200 to ≤400 units, and the highest (97%) for the ≤500 unit. (C) For the mixed light horse type mares: (1) 94 (77%) were EPG-positive, (2) the average (percentage) of EPG-positive mares by age was lowest for the two oldest age groups, higher for the 11 to 15-year-old age group, and highest for the two youngest age groups; (3) EPG average counts by year of age were lowest for the 16-20 group, higher for the 6-10 and >20 groups, and highest for 3-5 and 11-15 groups; (4) the average (percentage) of positive mares by 100 units of EPG counts was lowest for the ≤100 category (23%), increasing about 10% progressively in ≤200 to ≤500 categories, but lower (37%) for the >500 category. (D) For all the three mare types (TB, SB, and MLH), 37% of the mares were EPG-positive, and 63% of the mares were EPG-negative; for the age (years) of positive mares, about one half belonged to the 3-5 category and a progressive decrease was seen for the 6-10, 11-15, and 16-20 groups, and 36% for the >20-year-olds; the mean strongyle EPGs highest range was seen in the 11- to 15-year-olds; the highest mean was in the 6- to 10-year-olds, and the lowest mean in the 3- to 5- and 16- to 20-year-olds. For the grouping of the strongyle EPG values by units of 100, three-fourths were in the ≤500 category, and the lowest percentage was for the >500 category. This research showed the value of strongyle EPG profiling for the mares. It was most useful for TBs where data from a large number of horses showed that over two-third...

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Section: Discussionmentioning

confidence: 99%

Investigation of strongyle EPG values in horse mares relative to known age, number positive, and level of egg shedding in field studies on 26 farms in Central Kentucky (2010–2011)

2011

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“…Despite widespread acceptance that fenbendazole may no longer have satisfactory adulticidal efficacy, an annual five-day larvicidal fenbendazole treatment at 7.5 or 10 mg/kg/day is still widely used as a distinct element of a parasite management program on many farms. However, this approach has failed to achieve acceptable egg count reduction in several studies (Chandler et al, 2000;Rossano et al, 2010;Mason et al, 2014). In addition, recent studies have reported a marked decrease of the egg reappearance period following moxidectin treatment (Rossano et al, 2010;Lyons et al, 2011;Relf et al, 2014), and this has been found to be associated with survival of luminal L4 cyathostomin larvae .…”

Section: Introductionmentioning

confidence: 99%

“…However, this approach has failed to achieve acceptable egg count reduction in several studies (Chandler et al, 2000;Rossano et al, 2010;Mason et al, 2014). In addition, recent studies have reported a marked decrease of the egg reappearance period following moxidectin treatment (Rossano et al, 2010;Lyons et al, 2011;Relf et al, 2014), and this has been found to be associated with survival of luminal L4 cyathostomin larvae . However, it remains unknown whether these developments may affect the larvicidal efficacy of moxidectin.…”

Section: Introductionmentioning

confidence: 99%

Local and systemic inflammatory and immunologic reactions to cyathostomin larvicidal therapy in horses

Nielsen

Loynachan

Jacobsen

et al. 2015

Veterinary Immunology and Immunopathology

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“…Parasitic nematodes of the group Cyathostominae are a potential cause of serious (Canever et al, 2013), with several studies reporting a shortened strongyle egg 81 reappearance period following ivermectin (Geurden et al 2014;Relf et al, 2014) and 82 moxidectin (Rossano et al, 2010;Relf et al, 2014) treatment. A shortened helminth egg 83 reappearance period is generally regarded as an early indicator of resistance (Sangster,84 1999), highlighting the threat of cyathostomin resistance to all available classes of broad 85 spectrum anthelmintic.…”

mentioning

confidence: 99%

Development of a recombinant protein-based ELISA for diagnosis of larval cyathostomin infection

et al. 2016

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Shortened strongyle-type egg reappearance periods in naturally infected horses treated with moxidectin and failure of a larvicidal dose of fenbendazole to reduce fecal egg counts

Cited by 60 publications

References 10 publications

Investigation of strongyle EPG values in horse mares relative to known age, number positive, and level of egg shedding in field studies on 26 farms in Central Kentucky (2010–2011)

Investigation of strongyle EPG values in horse mares relative to known age, number positive, and level of egg shedding in field studies on 26 farms in Central Kentucky (2010–2011)

Local and systemic inflammatory and immunologic reactions to cyathostomin larvicidal therapy in horses

Development of a recombinant protein-based ELISA for diagnosis of larval cyathostomin infection

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