Transmission of Ehrlichia risticii, the agent of Potomac horse fever, using naturally infected aquatic insects and helminth vectors

Preliminary report

John E Madigan, Nicola Pusterla, E. Johnson, J. S. Chae, J. Berger Pusterla, E. Derock, S. P. Lawler

Research output: Contribution to journalArticle

33 Citations (Scopus)

Abstract

Ehrlichia risticii, the agent of Potomac horse fever (PHF), has been recently detected in trematode stages found in snail secretions and in aquatic insects. Based on these findings, horses could conceivably be exposed to E. risticii by skin penetration with infected cercariae, by ingestion of infected cercariae in water or via metacercariae in a second intermediate host, such as an aquatic insect. In order to test this hypothesis, horses were challenged with infectious snail secretions and aquatic insects collected from a PHF endemic region in northern California. Two horses stood with their front feet in water harbouring E. risticii-infected cercariae, 2 horses drank water harbouring E. risticii-infected cercariae, and 6 horses were fed pools of different aquatic insects harbouring E. risticii-infected metacercariae. In this preliminary study, only the one horse infected orally with mature caddisflies (Dicosmoecus gilvipes) developed the clinical and haematological disease syndrome of PHF. The agent was isolated from the blood of the infected horse in a continuous cell line and identified as E. risticii by characterisation of the 16S rRNA gene. Therefore, E. risticii is maintained in nature in a complex aquatic ecosystem and transmission to horses can occur through accidental ingestion of insects such as caddisflies containing infected metacercariae. At present, the small number of horses used in this study does not exclude other insects and free trematode stages as potential sources of infection.

Original languageEnglish (US)
Pages (from-to)275-279
Number of pages5
JournalEquine Veterinary Journal
Volume32
Issue number4
StatePublished - Jul 2000

Fingerprint

Neorickettsia risticii
Insect Vectors
aquatic insects
Helminths
helminths
Horses
Fever
horses
cercariae
Insects
Cercaria
metacercariae
Potomac horse fever
Metacercariae
Trichoptera
Trematoda
snails
Snails
ingestion
secretion

Keywords

  • Aquatic insects
  • Ehrlichia risticii
  • Horse
  • Natural infection route
  • Potomac horse fever
  • Snails
  • Trematode

ASJC Scopus subject areas

  • veterinary(all)

Cite this

Transmission of Ehrlichia risticii, the agent of Potomac horse fever, using naturally infected aquatic insects and helminth vectors : Preliminary report. / Madigan, John E; Pusterla, Nicola; Johnson, E.; Chae, J. S.; Berger Pusterla, J.; Derock, E.; Lawler, S. P.

In: Equine Veterinary Journal, Vol. 32, No. 4, 07.2000, p. 275-279.

Research output: Contribution to journalArticle

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