Anthelmintic therapy of equine cyathostomin nematodes – larvicidal efficacy,egg reappearance period,and drug resistance

Cyathostomins are ubiquitous in grazing horses across the world, and anthelmintic resistance has been reported with increasing levels over past decades. The aims of the present study were (i) to investigate the efficacy against encysted larval stages of moxidectin (0.4?mg/kg) and fenbendazole (10?mg/kg daily for five consecutive days) and compare these regimens at 2 and 5?weeks post-treatment, (ii) to investigate individual cyathostomin species associated with shortened egg reappearance periods, and (iii) to document species exhibiting decreased susceptibility to the evaluated compounds. Thirty-six ponies were allocated to treatment groups with half euthanatized 2?weeks post-treatment, and the remainder necropsied after 5?weeks. Luminal and mucosal worm counts were conducted and strongyle egg counts were determined at weekly intervals. At 2?weeks, mean reductions of early L3s were 50.4% and 73.8% for fenbendazole and moxidectin, respectively. At 5?weeks, the respective efficacies were 51.3% and 71.8%. Two week efficacies against late L3s and L4s (LL3s/L4s) were 70.8% and 74.6% for fenbendazole and moxidectin, respectively, whereas very low numbers were found in all three groups at 5?weeks. None of the mucosal counts were significantly different between treatment groups. Fenbendazole and moxidectin reduced luminal worm counts by 93.2% and 98.3% at 2?weeks following administration, with moxidectin group adult counts being significantly lower than the other two groups (P?<?0.0001). Both treatment groups had increased counts 3?weeks later (P?=?0.0415). A moxidectin ERP of 4?weeks was associated with surviving luminal L4s, and adult species contributing to this were Cyathostomum catinatum, Cylicostephanus longibursatus, Cylicocyclus ashworthi and Cylicocyclus nassatus. This study documented (i) larvicidal efficacy of fenbendazole much lower than historical standards, (ii) survival of luminal immatures (L4) following moxidectin administration, and (iii) new information about cyathostomin species associated with these phenomena.     

Prevalence and abundance of equine strongyles (Nematoda: Strongyloidea) in tropical Australia

A postmortem survey of 57 horses in tropical northern Queensland revealed 41 (89%) infected with intestinal strongyles. Thirty-five strongyle species (8 large strongyles and 27 small strongyles [Cyathostominae]) were recorded of which 9 species are reported from Australia for the first time. The 14 most prevalent small strongyles were Cyathostomum catinatum (in 76% of horses), Cyathostomum coronatum (65%), Cyathostomum pateratum (33%), Cyathostomum labiatum (30%), Cylicostephanus calicatus (70%), Cylicostephanus longibursatus (67%), Cylicostephanus goldi (43%), Cylicostephanus minutus (26%), Cylicocylus nassatus (67%), Cylicocyclus leptostomus (41%), Cylicocylus insigne (41%), Cylicocyclus radiatus (33%), Cylicocyclus brevicapsulates (22%), and Poteriostomum imperidentum (24%). The remaining cyathostomes were each found in less than 15% of horses. The 4 most common large strongyles were Triodontophorus serratus (30%), Strongylus vulgaris (28%), Strongylus equinus, and Strongylus edentatus (both 22%). The number of species of small strongyles per horse showed a marked variation (mean 10.3, range 2-21) but bore no relationship to either the total number of strongyles per horse, age, sex, and breed of horse, or season. Total number of strongyles per horse (mean 15,890, range 20-165,000) was less than in recent surveys in Europe and the U.S.A. Most horses had low worm burdens, whereas a very small number were heavily infected. Ninety-seven per cent of the total strongyle counts were small strongyles. Strongylus species contributed just over 1%. Small numbers of large strongyles per horse were usual with T. serratus (mean 570), S. vulgaris (mean 330), and S. equinus (mean 330) the most numerous.(ABSTRACT TRUNCATED AT 250 WORDS)     

Morphology and diagnosis of the fourth-stage larva of <Emphasis Type="Italic">Coronocyclus labratus</Emphasis> (Looss, 1900) (Nematoda: Strongyloidea) parasitising equids

The fourth larval stage (L4) of Coronocyclus labratus (Looss, 1900) Hartwich, 1986, one of the common species of the Cyathostominae found in equids, is identified and described. The larvae found were identified as C. labratus by finding moulting forms possessing characters of both larval and adult stages. The larvae are similar to those of Cylicocyclus leptostomum (Kotlán, 1920) Foster, 1936, Cyathostomum catinatum Looss, 1900 and Cylicostephanus goldi (Boulenger, 1917) Lichtenfels, 1975. The buccal capsule (BC) wall of the L4 of Cylicocyclus leptostomum is thinner than that of Coronocyclus labratus, and the ring of the oesophageal funnel is comparatively less well developed. In C. labratus the dorsal tooth protrudes only slightly into the buccal cavity, and this larva possesses a characteristically elongate, pyriform oesophagus. In Cyathostomum catinatum, the BC walls are thicker than in Coronocyclus labratus, and the dorsal tooth is more bluntly pointed. Sublateral teeth, if present, are bluntly pointed in the former species, but usually absent or indistinct in C. labratus. Larvae of Cylicostephanus goldi differ from those of Coronocyclus labratus in the larger size of the BC.     

Parasitic helminths of the cecum and colon of equidae in Italy]

Intestinal helminths from coecum and colon were studied in 93 equidae including 40 horses, 36 donkeys and 17 mules. A total of 38 species, 36 nematodes and 2 cestodes, were identified as follows: 1) Triodontophorus serratus, 2) Triodontophorus brevicauda, 3) Strongylus equinus, 4) Strongylus edentatus, 5) Strongylus vulgaris, 6) Cyathostomum tetracanthum, 7) Cyathostomum coronatum, 8) Cyathostomum labiatum, 9) Cyathostomum labratum, 10) Cyathostomum alveatum, 11) Cyathostomum pateratum, 12) Cyathostomum catinatum, 13) Cyathostomum sagittatum, 14) Cylicodontophorus bicoronatus, 15) Cylicocyclus radiatus, 16) Cylicocyclus auriculatus, 17) Cylicocyclus elongatus, 18) Cylicocyclus nassatus, 19) Cylicocyclus insigne, 20) Cylicocyclus leptostomus, 21) Cylicostephanus calicatus, 22) Cylicostephanus poculatus, 23) Cylicostephanus minutus, 24) Cylicostephanus longibursatus, 25) Cylicostephanus hybridus, 26) Cylicostephanus goldi, 27) Cylicostephanus ornatus, 28) Cylicostephanus skrjabini, 29) Poteriostomum ratzii, 30) Gyalocephalus capitatus, 31) Parascaris equorum*, 32) Probstmayria vivipara, 33) Draschia megastoma*, 34) Habronema muscae*, 35) Habronema majus*, 36) Setaria equina*, 37) Anoplocephala perfoliata, 38) Paranoplocephala mamillana. The asterisked species are those not usually localized in the examined material. The most frequent parasites were found in all three hosts. Species 1, 4, 6, 9, 10, 12, 21, 22, 30 and 35 showed significant differences in prevalence between horses and donkeys, the mule generally having intermediate values. Multiple infections and total worm burden appear to decrease in older animals (> 15 years). Parasite associations occur mostly at random as expected from the values of the respective total prevalences. Some significant excesses on expected values were recorded but not significant deficits. The total worm burden increases with the number of parasite species and the increase appears to follow an exponential pattern.     

Shortened egg reappearance periods of equine cyathostomins following ivermectin or moxidectin treatment: morphological and molecular investigation of efficacy and species composition

Macrocyclic lactones have been the most widely used drugs for equine parasite control during the past four decades. Unlike ivermectin, moxidectin exhibits efficacy against encysted cyathostomin larvae, and is reported to have persistent efficacy with substantially longer egg reappearance periods. However, shortened egg reappearance periods have been reported recently for both macrocyclic lactones, and these findings have raised several questions: (i) are egg reappearance period patterns different after ivermectin or moxidectin treatment? (ii) Are shortened egg reappearance periods associated with certain cyathostomin species or stages? (iii) How does moxidectin’s larvicidal efficacy affect egg reappearance period? To address these questions, 36 horses at pasture, aged 2–5 years old, were randomly allocated to three treatment groups: 1, moxidectin; 2, ivermectin; and 3, untreated control. Strongylid fecal egg counts were measured on a weekly basis, and the egg reappearance period was 5 weeks for both compounds. Strongylid worm counts were determined for all horses: 18 were necropsied at 2 weeks post-treatment (PT), and the remaining 18 at 5 weeks PT. Worms were identified to species morphologically and by internal transcribed spacer-2 (ITS-2) rDNA metabarcoding. Moxidectin and ivermectin were 99.9% and 99.7% efficacious against adults at 2 weeks post treatment, whereas the respective efficacies against luminal L4s were 84.3% and 69.7%. At 5 weeks PT, adulticidal efficacy was 88.3% and 57.6% for moxidectin and ivermectin, respectively, while the efficacy against luminal L4s was 0% for both drugs. Moxidectin reduced early L3 counts by 18.1% and 8.0% at 2 or 5 weeks, while the efficacies against late L3s and mucosal L4s were 60.4% and 21.2% at the same intervals, respectively. The luminal L4s surviving ivermectin treatment were predominantly Cylicocyclus (Cyc.) insigne. The ITS-2 rDNA metabarcoding was in good agreement with morphologic species estimates but suggested differential activity between moxidectin and ivermectin for several species, most notably Cyc. insigne and Cylicocyclus nassatus. This study was a comprehensive investigation of current macrocyclic lactone efficacy patterns and provided important insight into potential mechanisms behind shortened egg reappearance periods.     

Evaluation of the Egg Hatch Assay and the Larval Migration Inhibition Assay to detect anthelmintic resistance in cattle parasitic nematodes on farms

Resistance to anthelmintic drugs, particularly to the widely used benzimidazoles (BZs) and macrocyclic lactones (MLs) is an increasing problem in cattle industries worldwide. Reliable methods for the assessment of anthelmintic efficacy in the field are required in order to react before resistance becomes an obvious problem on individual properties. The ability of the Egg Hatch Assay (EHA) and the Larval Migration Inhibition Assay (LMIA) to detect anthelmintic resistance under field conditions was evaluated on cattle farms in Northern Germany. As published previously Faecal Egg Count Reduction Test (FECRT) was performed using oral albendazole (Valbazen®) or injectable ivermectin (Ivomec®). Herein the FECRT results described earlier were compared with data from EHAs or LMIAs, respectively, performed with eggs from fresh faeces or larvae from faecal cultures of the tested animals before and after treatment. The obtained EC₅₀ values allowed the assessment of efficacy of albendazole and ivermectin on farm level. The results of the FECRTs and the results of both in vitro assays were comparable. In comparison to the FECRT the in vitro assays are less time, labour and cost intensive and are able to assess the susceptibility status of a worm population without treatment. Therefore both are beneficial alternatives for the reliable detection of reduced efficacy of these two drug classes on farms.     

A Field Survey on Anthelmintic Resistance in Equine Small Strongyles in Norway

A field survey at 17 stables involving 221 horses was performed to evaluate the presence of anthelmintic resistance in the equine small strongyles (cyathostomes). The horses were allocated into treatment groups, and resistance to fenbendazole (FBZ), pyrantel pamoate (PYR) and ivermectin (IVM) was tested by the faecal egg count reduction test (FECR-test). Faecal samples were collected at the time of treatment, 14 days post treatment and 90 days post treatment. Resistance to FBZ, which was defined as a faecal egg count reduction <95%, was found in 14 out of 17 stables. In 2 of the 14 stables the egg reductions were close to the limit of 95%, 91 and 93%, respectively. In 1 stable the egg reductions indicated resistance to PYR as well as detection of resistance to FBZ, 94% reduction for PYR and 85% for FBZ. No signs of resistance were detected to IVM. The investigation was performed in late autumn and winter, and due to the climatic conditions and cleaning procedures in the stables no reinfection took place during this period. The faecal egg count reduction from treatment till day 90 post treatment was used as an expression of the effect of PYR and IVM on the early stage (hypobiotic), late third stage and fourth stage larvae in the gut wall. This was justified because there was no reinfection and because the 14 day post treatment egg counts were zero or close to zero for the PYR and IVM treatment groups. The effects of PYR and IVM on the larval stages were compared and no statistically significant differences were found.     

Morphology and diagnosis of some fourth-stage larvae of cyathostomines (Nematoda: Strongyloidea) in donkeys Equus asinus L. from Ethiopia

Fourth-stage larvae of four species of the Cyathostominae Nicoll, 1927 parasitic in donkeys Equus asinus L. from Ethiopia were identified mainly using moulting specimens. They are Cylicocyclus asini Matthee, Krecek & Gibbons, 2001, C. auriculatus (Looss, 1900) Chaves, 1930, Cyathostomum tetracanthum (Mehlis, 1831) Molin, 1861 (sensu Looss, 1900) and Cylindropharynx brevicauda Leiper, 1911. The larva of Cylicocyclus asini is similar to those of C. nassatus (Looss, 1900) Chaves, 1930 and C. leptostomum Kotlán, 1920, but differs from the former by the shape of the dorsal tooth in the oesophageal funnel, which is notably smaller than in C. asini but similar to that of C. leptostomum. However, the larva of C. asini differs from that of C. leptostomum in the size of the buccal capsule, which is notably larger than in C. leptostomum but similar to that of C. nassatus. The larva of C. auriculatus is very similar to that of C. insigne (Boulenger, 1917) Chaves, 1930. The larva of Cyathostomum tetracanthum is similar to those of Cylicostephanus bidentatus (Ihle, 1925) Lichtenfels, 1975, C. goldi (Boulenger, 1917) Lichtenfels, 1975 and Cyathostomum catinatum Looss, 1900. The larva of Cylindropharynx brevicauda is similar to that of Petrovinema skrjabini (Ershov, 1930) Ershov, 1943 but smaller in size. Including the four cyathostomine species identified in the present study, 36 species belonging to 13 genera have so far been described and identified of a total of 64 recognised and confirmed species of equine strongyles.     

Simultaneous Detection and Identification of Common Cell Culture Contaminant and Pathogenic Mollicutes Strains by Reverse Line Blot Hybridization

We have developed a reverse line blot (RLB) hybridization assay to detect and identify the commonest mollicutes causing cell line contamination (Mycoplasma arginini, Mycoplasma fermentans, Mycoplasma hyorhinis, Mycoplasma orale, and Acholeplasma laidlawii) and human infection (Mycoplasma pneumoniae, Mycoplasma hominis, Mycoplasma genitalium, Ureaplasma parvum, and Ureaplasma urealyticum). We developed a nested PCR assay with “universal” primers targeting the mollicute 16S-23S rRNA intergenic spacer region. Amplified biotin-labeled PCR products were hybridized to membrane-bound species-specific oligonucleotide probes. The assay correctly identified reference strains of 10 mollicute species. Cell cultures submitted for detection of mollicute contamination, clinical specimens, and clinical isolates were initially tested by PCR assay targeting a presumed mollicute-specific sequence of the 16S rRNA gene. Any that were positive were assessed by the RLB assay, with species-specific PCR assay as the reference method. Initially, 100 clinical and 88 of 92 cell culture specimens gave concordant results, including 18 in which two or more mollicute species were detected by both methods. PCR and sequencing of the 16S-23S rRNA intergenic spacer region and subsequent retesting by species-specific PCR assay of the four cell culture specimens for which results were initially discrepant confirmed the original RLB results. Sequencing of amplicons from 12 cell culture specimens that were positive in the 16S rRNA PCR assay but negative by both the RLB and species-specific PCR assays failed to identify any mollicute species. The RLB hybridization assay is sensitive and specific and able to rapidly detect and identify mollicute species from clinical and cell line specimens.     

The response of red-chested moustached tamarins to long calls from their natal and alien populations

Long calls of red-chested moustached tamarins, Saguinus l. labiatus, typically last 1–2 s and are made up of individual syllables. Their acoustic structure varies between populations. In this study, captive adult male and female tamarins of each of three different populations in Bolivia were played unfamiliar long calls from their natal and alien populations to determine whether they responded differentially to them. The results suggested that female tamarins respond selectively to male long calls from their natal populations.     

Homoplastic evolution of external colouration in Asian stout newts (Pachytriton) inferred from molecular phylogeny

Wu, Y., Wang, Y., Jiang, K., Chen, X. & Hanken, J. (2009). Homoplastic evolution of external colouration in Asian stout newts (Pachytriton) inferred from molecular phylogeny.—Zoologica Scripta, 39, 9–22. The Asian stout newts of the genus Pachytriton (Salamandridae) inhabit montane streams in south-eastern China. Despite their abundance in the pet trade, the phylogeny and systematics of this genus are poorly understood. Colouration is often used to delimit species under the assumption that consistent chromatic differences characterize independent evolutionary lineages. We present the first phylogenetic study of Pachytriton that incorporates 2.35 kb of mitochondrial DNA (ND2, cytb) and 1.2 kb of nuclear sequence data (RAG-1) along with morphometric characters to infer evolutionary relationships and patterns of colour evolution among the three described species: Pachytriton brevipes, Pachytriton labiatus and Pachytriton archospotus. Our results support the monophyly of Pachytriton and recover P. archospotus as the sister taxon to P. brevipes. Monophyly of P. labiatus is significantly rejected: south-western populations are sister to the group of P. brevipes plus P. archospotus, whereas north-eastern populations nest with P. brevipes. The two geographic units are further separated by multivariate morphological analyses. South-western P. labiatus is the type species; misidentification of north-eastern populations as P. labiatus results from their similar colouration. An unspotted, dark brown dorsum is the likely ancestral state for the genus, whereas black-spotted colouration characterized the common ancestor of P. brevipes, P. archospotus, and north-eastern P. labiatus and was secondarily lost in the latter group. Homoplastic evolution and intraspecific variation render colour pattern in Pachytriton an unreliable character for delimiting species boundaries. North-eastern populations of P. labiatus are declining as the result of human collection and habitat destruction and are in urgent need of conservation protection.     

Horses grazing with cattle have reduced strongyle egg count due to the dilution effect and increased reliance on macrocyclic lactones in mixed farms

Strongyle infection is an important issue in horse breeding. It impairs horse health and performance, with young horses being the most sensitive. Strongyle control has long relied on the systematic use of chemical treatments. However, expanding anthelmintic resistance among strongyles calls for alternative options. Mixed grazing is assumed to reduce strongyle load on the pasture as the result of a dilution effect. This has been shown in small ruminants grazing with cattle, but the putative benefits of co-grazing between horses and cattle have not yet been evaluated. Here, we conducted field surveys and face-to-face interviews on 44 farms from two contrasted saddle-horse production areas, Normandy and northern Massif Central, to compare equine strongyle management practices between specialized systems and mixed horse-cattle systems. Our goals were (i) to quantify breeders’ awareness of the putative benefits associated with the co-grazing of horses and cattle, (ii) to establish whether mixed farming was associated with different strongyle management strategies and (iii) to test whether strongyle egg excretion was reduced in horses grazed with beef cattle. Every breeder relied on systematic calendar treatments, and only 8 out of the 23 mixed breeders were aware that co-grazing of horses with cattle could be used as part of their strongyle control strategy. Management practices were similar across both systems in Normandy. In Massif Central, mixed breeders formed a distinct cluster from their specialized counterparts: deworming was less frequent and stocking density was higher in mixed farms, while specialized breeders seemed more willing to integrate herd and plot management into control strategies. Faecal egg counts measured in horses from Massif Central were significantly reduced when horses were grazed with cattle. This was the result of an increased reliance on macrocyclic lactones in mixed farms (P < 0.01) and a significant dilution effect (P < 0.01). When considering a subsample of horses treated with macrocyclic lactones only, young horses grazed with cattle had 50% fewer strongyle eggs excreted in their faeces than horses grazed in equine-only pastures (P < 0.01). This is the first evidence of the benefits of mixed grazing with cattle as an alternative to control strongyle infection in horses, although this promising alternative remains largely unknown by horse breeders.     

Enterocytozoon bieneusi Genotypes and Infections in the Horses in Korea

Enterocytozoon bieneusi is a microsporidian pathogen. Recently, the equestrian population is increasing in Korea. The horse-related zoonotic pathogens, including E. bieneusi, are concerns of public health. A total of 1,200 horse fecal samples were collected from riding centers and breeding farms in Jeju Island and inland areas. Of the fecal samples 15 (1.3%) were PCR positive for E. bieneusi. Interestingly, all positive samples came from Jeju Island. Diarrhea and infection in foals were related. Two genotypes (horse1, horse2) were identified as possible zoonotic groups requiring continuous monitoring.     

Plasmid Profiles of Virulent Rhodococcus equi Strains Isolated from Infected Foals in Poland

Rhodococcus equi is an important bacterial pathogen in foals up to 6 months old, widespread in horse farms all over the world. It was found that only virulent R. equi strains expressing 15–17 kDa virulence-associated protein (VapA) and having large virulence plasmid of 85–90 kb containing vapA gene are pathogenic for horses. To date, 12 plasmid types have been reported in VapA positive strains from horses. There are no data concerning plasmid types of Polish field R. equi strains isolated from horses and horse farm environment. The aim of the study is to determine plasmid profiles of virulent R. equi strains isolated in Poland from dead foals as well as from soil samples taken from horse breeding farms. Plasmid profiles of 10 clinical strains derived from 8 farms and 11 environmental strains from 3 farms, confirmed as virulent by PCR, were compared with 12 reference strains containing the known plasmid size and type. Plasmid DNAs were analysed by digestion with the restriction endonucleases BamHI, EcoRI, EcoT22I, and HindIII for detailed comparison and estimation of plasmid sizes. The results of RFLP analysis revealed that all except one isolates used in the study are classified as VapA 85 kb type I plasmid. One strain harboured VapA 87 kb type I plasmid. This is the first report of plasmid types of Polish field R. equi strains. The results of our preliminary investigations on horse farms located in central and eastern Poland indicate that the virulent R. equi strains thus far isolated from diseased foals and horse farms environment represent a highly uniform plasmid pattern.     

Use of new strains of Rhodobacter sphaeroides and a modified simple culture medium to increase yield and facilitate purification of the reaction centre

A new gene expression system was developed in Rhodobacter sphaeroides, replacing a pRK415-based system used previously. The broad host-range IPTG-inducible plasmid pIND4 was used to create the plasmid pIND4-RC1 for expression of the puhA and pufQBALMX genes, encoding the reaction centre (RC) and light-harvesting complex 1 (LH1) proteins. The strain R. sphaeroides ΔRCLH was used to make a knockout of the rshI restriction endonuclease gene, enabling electroporation of DNA into the bacterium; a subsequent knockout of ppsR was made, creating the strain R. sphaeroides RCx lacking this oxygen-sensing repressor of the photosynthesis gene cluster. Using pIND4-RC1, LH1 levels were increased by a factor of about 8 over pRS1 per cell in cultures grown semi-aerobically. In addition, the ppsR knockout allowed for photosynthetic pigment–protein complex synthesis in the presence of high concentrations of molecular oxygen; here, LH1 levels per cell increased by 20 % when grown under high aeration conditions. A new medium (called RLB) is the E. coli medium LB supplemented with MgCl₂ and CaCl₂, which was found to increase growth rates and final cell culture densities, with an increase of 30 % of LH1 per cell detected in R. sphaeroides RCx(pIND4-RC1) grown in RLB versus LB medium. Furthermore, cell density was about three times greater in RLB compared to semi-aerobic conditions. The combination of all the modifications resulted in an increase of LH1 and RC per mL of culture volume by approximately 35-fold, and a decrease in the length of culture incubation time from about 5 days to ~36 h.     

Interaction of anthelmintic benzimidazoles and benzimidazole derivatives with bovine brain tubulin

The binding and inhibitory properties of 11 benzimidazoles for bovine brain tubulin were investigated. The effects of the benzimidazoles on the initial rates of microtubule polymerization were determined by a turbidimetric assay. The median inhibitory concentrations (I₅₀) for nocodazole, oxibendazole, parbendazole, mebendazole and fenbendazole ranged from 1.97 · 10⁻⁶ to 6.32 · 10⁻⁶ M. Benomyl, cambendazole and carbendazim had I₅₀ values from 5.83 · 10⁻⁵ to 9.01 · 10⁻⁵ M. Thiabendazole had an I₅₀ value of 5.49 · 10⁻⁴ M. Inhibitor constants (K_i) were determined by the colchicine binding assay. Oxibendazole, fenbendazole, and cambendazole had K_i values of 3.20 · 10⁻⁵, 1.73 · 10⁻⁵ and 1.10 · 10⁻⁴ M, respectively. Oxibendazole and fenbendazole were competitive inhibitors of colchicine. In contrast, cambendazole was a noncompetitive inhibitor of colchicine. The ability of these benzimidazoles to inhibit microtubule polymerization and the mode of action for the anthelmintic benzimidazoles is discussed.     

Strongylids (Nematoda: Strongylidae) of domestic horses in Ukraine: modern state of Fauna and structure of the parasite community

Species composition and structure of the strongylid community was studies on helminthological material collected from 162 domestic horses from 11 regions of Ukraine by the in vivo method. Animals were treated with anthelmintic drug "Univerm" (0.2% aversectin C, Russia). Faecal samples (200 g each) were collected from every horse at 24, 36, 48 and 60 hours after treatment; all nematodes expelled (90.851 specimens) were collected and identified. Thirty-three strongylid species from 12 genera (8 species of subfamily Strongylinae and 25--of Cyathostominae) were found in domestic horses in Ukraine. Cyathostominae dominated in the strongylid community; they were found in 100 % horses and composed 98.21% of community. "Core" of the strongylid community was composed by 7 cyathostome species. Decreasing of proportion of Strongylinae in the community for last 40 years was registered; strongylines were found in 37.6% of horses and composed 1.25% of community. Maximal prevalence was 20.98% (Strongylus vulgaris). Bray-Curtis cluster analysis revealed high similarity of strongylid communities in horses from various regions of Ukraine. Difference in general structure of strongylid communities of horses from different horse-keeping conditions was established. Horses from farms with stable-paddock keeping conditions had bimodal strongylid community structure; while horses from stable-pasture keeping conditions possessed multimodal community structure.     

Faecal egg counts and nemabiome metabarcoding highlight the genomic complexity of equine cyathostomin communities and provide insight into their dynamics in a Scottish native pony herd

Understanding the composition of gastrointestinal nematode communities may help to mitigate or exploit parasite adaptations within their host. We have used nemabiome deep amplicon sequencing of internal transcribed spacer-2 (ITS-2) ribosomal DNA to describe the temporal and host species composition of gastrointestinal nematode communities following sampling of six Scottish ponies across 57 months. In the absence of parasite control, each horse showed seasonal trends of increases and decreases in faecal egg counts, consistent with the epidemiology of equine strongylid parasites, however, the composition of parasites within individuals changed over time. Sixteen presumptive strongylid species were identified in each of the horses, 13 of which were distributed in a complex clade together with small numbers of amplicon sequences which could not be classified beyond the Cyathostominae subfamily level. Egg shedding of seven trichostrongylid species, which had previously been identified in co-grazed Soay sheep, was identified during the early spring. Faecal egg counts and the percentage of amplicon sequences assigned to each gastrointestinal nematode species were combined to describe their relative abundance across both host and time. Significant differences in species diversity between horses and between months were observed, being greatest from March to May and least from October to December. The magnitude of the individual horse effect varied between months and, conversely, the magnitude of the seasonal effect varied between individual horses. The most abundant gastrointestinal nematode in each of the horses was Cylicostephanus longibursatus (46.6% overall), while the abundance of the other strongylid species varied between horses and relative to each other. Patent C. longibursatus infections over the winter months might represent a genetic adaptation towards longer adult worm survival, or a lower rate of developmental arrest in the autumn. This study provides insight into highly complex phylogenetic relationships between closely related cyathostomin species; and describes the dynamics of egg shedding and pasture contamination of co-infecting equine gastrointestinal nematode communities. The results could be applied to determine how climatic and management factors affect the equilibrium between hosts and their parasites, and to inform the development of sustainable gastrointestinal nematode control strategies for different host species.     

Ivermectin and moxidectin against soil-transmitted helminth infections

Ivermectin and moxidectin, two macrocyclic lactones, are potent antiparasitic drugs currently registered and mainly used against filarial diseases; however, their potential value for improved soil-transmitted helminth (STH) control has been acknowledged. This review provides insights on recent studies evaluating the efficacy of ivermectin and moxidectin as single or coadministered therapy against human soil-transmitted helminthiases (including Strongyloides stercoralis infections) and on pharmacokinetic/pharmacodynamic parameters measured in treated populations. Furthermore, we discuss current gaps for research, highlight advantages – but also existing challenges – for uptake of ivermectin and/or moxidectin treatment schemes into routine STH control in endemic countries.