Three recently recognized species of cyathostomes (Nematoda: Strongylidae) in equids in Kentucky

Meta-analysis of cyathostomin species-specific prevalence and relative abundance in domestic horses from 1975-2020: emphasis on geographical region and specimen collection method

Background

Cyathostomins infect virtually all horses, and concomitant infections with 10 or more species per horse is standard. Species-specific knowledge is limited, despite potential species bias in development of disease and anthelmintic resistance. This is the first meta-analysis to examine effects of geographical region and cyathostomin collection method on reported composition of cyathostomin communities.

Methods

Thirty-seven articles published in English in 1975 or later, in which adults of individual species were systematically enumerated, were included. Seven regions; North America, South America, eastern Europe, western Europe, northern Europe, southern Africa, and Oceania, and three cyathostomin collection methods; (i) standard necropsy recovery from the large intestine, (ii) critical test collection from post-treatment feces and necropsy, and (iii) diagnostic deworming recovery solely from post-treatment feces, were considered. Generalized mixed linear models analyzed the effects of region and collection method on species-specific prevalence and relative abundance. Species richness was analyzed by mixed linear models.

Results

Definitively, the most prevalent and relatively abundant species were Cylicocyclus nassatus (prevalence = 93%, relative abundance = 20%), Cylicostephanus (Cys.) longibursatus (93%, 20%), and Cyathostomum catinatum (90%, 16%). A bias toward horses with high infection intensities and cyathostomin collection from feces resulted in North American critical tests and eastern European diagnostic deworming overestimating the species-specific prevalence and underestimating the relative abundance of rare/uncommon species compared to respective intra-regional standard necropsies. North American critical tests underestimated species richness due partially to identification key errors. Inter-regional standard necropsy comparisons yielded some species-specific regional differences, including a significantly higher Cys. longibursatus prevalence and relative abundance in North America (92%, 33%) than in eastern Europe (51%, 7%) (P > 0.0001). Localization of critical tests to North America and diagnostic deworming to Eastern Europe precluded expansive ‘region by collection method’ interaction analyses.

Conclusion

We provide substantial data to inform study design, e.g. effect and study size, for cyathostomin research and highlight necessity for method standardization and raw data accessibility for optimal post-factum comparisons.

Fatal parasite-induced enteritis and typhlocolitis in horses in Southern Brazil

Abstract Diseases related to the alimentary system are the main cause of death in horses. This retrospective study aimed to describe the pathological findings of fatal parasite-induced enteritis and typhlocolitis caused by cyathostominae, Eimeria leuckarti, Balantidium coli, and Strongyloides westeri in horses. The records of parasite-induced intestinal lesions in horses necropsied in Southern Brazil between 2005 and 2017 were reviewed. Ten horses had fatal parasitic enteritis and/or typhlocolitis, and the main causes were: cyathostominae typhlocolitis (6/10), E. leuckarti enteritis (1/10), S. westeri enteritis (1/10), B. coli colitis related to cyathostominae (1/10), and infection by multiple agents (1/10). Cyathostominae typhlocolitis showed marked mucosal thickening, with multifocal elevated nodules containing tangled filiform parasites. Microscopic examination revealed that the mucosa and submucosa had encysted parasitic structures surrounded by eosinophilic and granulomatous inflammation. E. leuckarti enteritis was microscopically characterized by macrogamonts, microgamonts, and oocysts inside the host cells. S. westeri enteritis showed microscopic atrophy of the villi with numerous mucosal encysted parasitic structures. B. coli typhlocolitis showed severe diffuse mucosal reddening, with microscopic superficial mucosal necrosis associated with multiple protozoan trophozoites. Fatal parasite-induced enteritis and typhlocolitis are important causes of death in horses in Southern Brazil.

The prevalence, abundance and distribution of cyathostomins (small stongyles) in horses from Western Romania

Forty seven working horses from Romania were post-mortem examined for small strongyles (Cyathostominae) infections. All horses were found infected. The overall cyathostomins intensity ranged from 390 to 13,010 and horses were infected by 8-24 species. The intensity was higher in ventral colon (1531) and dorsal colon (824), the lowest in the caecum (524). Twenty four species were identified. Cyathostomum catinatum, Cylicocyclus insigne, and C. Nassatus had 100% of prevalence. Over 50% of horses were infected by Coronocyclus coronatus, Cylicostephanus calicatus, C. goldi, and C. longibursatus. Other prevalent species (34%-45%) were Cyathostomum tetracanthum, Cylicostephanus minutus and Gyalocephalus capitatus. Coronocyclus labiatus, Parapoteriostomum mettami, Poteriostomum imparidentatum and P. ratzii had the lowest prevalence. Most species showed high organ preference with a niche breadth value between 1 and 1.96 while only 7 species (Coronocyclus labiatus, Cyathostomum tetracanthum, C. brevicapsulatus, Cylicocyclus elongatus, C. insigne, C. leptostomum and C. radiatus) showed a more generalist selection. The niche breadth of 10 species was significantly (p<0.05) influenced by itself intensity (Coronocyclus labratus, Cyathostomum pateratum, C. tetracanthum, Cylicocyclus elongatus, C. radiatus, C. ultrajectinus, C. leptostomum, Cylicodontophorus euproctus, Poteriostomum imparidentatum, P. ratzii). The niche breadth of Cylicocyclus nassatus was positively (p<0.05) influenced by the summed intensity of the other species while that of Cylicocyclus elongatus was negatively (p<0.05) influenced by the intensity of the other species. The cluster analysis of the Cyathostominae community composition showed a major cluster composed by the three dominant species, followed by a cluster composed by Coronocyclus coronatus, while all the other species presented a tree like structure.