Parasite dynamics in untreated horses through one calendar year

Abstract

Background Horses are host to a plethora of parasites. Knowledge of the seasonality of parasite egg shedding and transmission is important for constructing parasite control programs. However, studies describing these patterns are sparse, and have largely been conducted only in the United Kingdom. This study evaluated strongylid egg shedding patterns and transmission dynamics of Strongylus vulgaris in naturally infected and untreated mares and foals through one calendar year in Kentucky, USA. The study also investigated the existence of a peri-parturient rise (PPR) in strongylid egg counts in foaling mares and collected information about Strongyloides westeri and Parascaris spp. in the foals. Methods This study was conducted from January to December 2018. A herd of 18 mares, one stallion, and 14 foals born in 2018 were followed throughout the year. Sera and feces were collected biweekly from all horses, and worm burdens enumerated in 13 foals at necropsy. An S. vulgaris ELISA antibody test was run on all serum samples. Fecal egg counts were determined for all horses, and coproculture and qPCR assay were employed to test for the presence of S. vulgaris in the mature horses. Data were analyzed using the proc glimmix procedure in the SAS 9.4 software program. Results We found a general lack of seasonality in strongylid egg shedding throughout the year among the mature horses, and no PPR was demonstrated. Shedding of S. vulgaris eggs displayed a higher abundance during the spring, but findings were variable and not statistically significant. Anti-S. vulgaris antibody concentrations did not display significant fluctuations in the mature horses, but evidence of passive transfer of antibodies to the foals was demonstrated, and foals assumed their own production of antibodies starting at approximately 20 weeks of age. Overall, colts shed higher numbers of strongylid, ascarid, and S. westeri eggs than fillies. Conclusions This study demonstrated a lack of seasonality in strongylid egg shedding for the study population, which is in stark contrast to previous studies conducted elsewhere. This strongly suggests that more studies should be done investigating these patterns under different climatic conditions. Graphical Abstract

Species interactions, stability, and resilience of the gut microbiota - Helminth assemblage in horses

“…At the whole blood transcriptome level, the pyrantel treatment per se contributed little to the variance in gene expression (2.92% on average, Figure S3 B) with no evidence of an inflammatory response, as previous data suggested. 70 However, anthelmintic treatment explained 20.2 and 17.3% of the variance in the host expression levels of neuroligin ( NLGN2 ) and solute carrier ( SLC10A7 ) coding gene, a transporter of various drugs 71 , 72 ( Figure S7 ), compatible with a direct effect of the pyrantel treatment on the host. A comparison between the treated and untreated low shedders 24h post-treatment found 13 differentially expressed (DE) genes ( Table 2 ).…”

Epidemiological study on factors influencing the occurrence of helminth eggs in horses in Germany based on sent-in diagnostic samples

“…A Swedish study confirmed the increased egg excretion in summer (Tydén et al 2019 ). The other British study detected no seasonality of strongyle egg shedding (Lester et al 2018 ; Steuer et al 2022 ). A recent study by Nielsen et al ( 2022 ) recommends that strongyles are best examined in spring or winter.…”

US-wide equine strongylid egg count data demonstrate seasonal and regional trends

“…Equine strongylid egg shedding has been demonstrated to fluctuate by season in some studies (Poynter, 1954;Duncan, 1974;Wood et al, 2013;Nielsen et al, 2021), but not in others (Lester et al, 2018;Steuer et al, 2022). However, regardless of whether these fluctuations occur or not, the general recommendation is to focus egg count monitoring and anthelmintic treatments around the active parasite transmission season (ESCCAP, 2019;Nielsen et al, 2019) so that treatments are aimed at reducing pasture contamination.…”