Incidental isolation of Setaria equina microfilariae in preparations of equine peripheral blood mononuclear cells

Michelle R. Yeargan, Eugene T. Lyons, Stephen A. Kania, Sharon Patton, Cormac C. Breathnach, David W. Horohov, Daniel K. Howe

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


In the course of a vaccine experiment on horses, microfilariae were observed in cultures of peripheral blood mononuclear cells (PBMCs) isolated from eleven of fifteen study horses. The microfilariae were clearly viable as evidenced by their vigorous movements in the cultures, thus indicating that they had survived the Ficoll gradient purification and the cryopreservation method used for retaining the PBMCs. The microfilariae were identified as Setaria equina, which is a vector-borne filarial nematode that causes a relatively benign infection of equids in which the adult worms reside in the peritoneal cavity. Although it is not possible to definitely state where the infections were acquired, the horses originated from Saskatchewan, Canada and spent a relatively short period of time in the United States prior to blood sampling. Therefore, it is likely that the infections occurred in Canada. Interestingly, assays conducted to determine levels of cytokine mRNA transcripts in the isolated PBMCs seemed to be largely unaltered by the presence of the microfilariae in the cell cultures. These findings demonstrate that a standard method used to purify and cryopreserve PBMCs from blood can result in the unintended co-isolation of worms from microfilaremic animals. Furthermore, the presence of the microfilariae did not appear to alter significantly the results of our immunologic assays, suggesting either that the nematode antigens were not recognized or that immunological tolerance may have developed in these horses. Although notable effects on the assays were not observed in this study, it seems possible that microfilarial contamination could represent a confounding variable for experiments examining cellular immunity.

Original languageEnglish
Pages (from-to)142-145
Number of pages4
JournalVeterinary Parasitology
Issue number1-2
StatePublished - Apr 6 2009

Bibliographical note

Funding Information:
The authors are grateful to Mr. Lynn Ennis for his assistance in securing and handling the horses. This research was partly supported by funds from Fort Dodge Animal Health. Published as Kentucky Agricultural Experiment Station article number 08-14-138.


  • Horse
  • Microfilariae
  • Peripheral blood mononuclear cells
  • Setaria equina
  • Vaccine

ASJC Scopus subject areas

  • Parasitology
  • General Veterinary


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