The Prevalence and Genetic Diversity of Babesia divergens in Ixodes ricinus Nymphs Collected from Farm- and Woodland Sites in Ireland.

Fiona Mckiernan,Jeremy Gray,Annetta Zintl,Jack O’Connor,Amie Flattery,John Browne,Taher Zaid

doi:10.3390/pathogens11030312

Abstract

The parasite, Babesia divergens causes redwater fever in cattle and a rare, albeit life-threatening disease in humans. In Ireland, B. divergens has always been considered an important pathogen as the high incidence of redwater fever precluded areas of the country from cattle farming. Moreover a relatively large proportion of human cases were reported here. Red deer (Cervus elaphus), which often harbour babesias that are genetically very similar (if not identical) to B. divergens, are quite widespread. In this study 1369 nymphal Ixodes ricinus ticks collected from various habitats were screened for the presence of B. divergens using TaqMan followed by conventional nested PCR. Fragments of the 18S rRNA gene locus (560 bp) were compared against published Irish B. divergens isolates from cattle, humans and red deer. Overall just 1% of I. ricinus nymphs were infected with B. divergens, with similar infection rates in ticks collected from farm- and woodland. Most (90%) 18S rRNA gene fragments derived from woodland ticks were 100% identical to published sequences from cattle and humans. One differed by a single nucleotide polymorphism (SNP) as did two isolates from ticks collected in bogland. Two isolates derived from nymphs collected in farmland differed by 2 and 4 SNPs respectively.

Highlights

The protozoan parasite, Babesia divergens, is the causative agent of redwater fever, an important disease of cattle
This study aimed to investigate the potential role of deer in the transmission cycle of B. divergens in Ireland by (i) determining B. divergens infection rates in ticks collected in farmland, woodland and some bog and limestone pavement sites and (ii) by comparing the genetic diversity of isolates from ticks to published sequences from cattle, humans and red deer in Ireland
We reported similar B. divergens infection rates in ticks collected from woodland and farmland

Summary

Introduction

The protozoan parasite, Babesia divergens, is the causative agent of redwater fever, an important disease of cattle. The parasite infects humans where it can cause acute, malaria-like disease. The only deer species where 18S rRNA and cytochrome oxidase subunit 1 (COI) gene fragments that were 100% identical to B. divergens have been reported are red deer [3,4], indicating that they are susceptible to B. divergens infection. This makes them the most likely candidate for a wildlife reservoir host, the extent to which they contribute to tick infection rates (if at all) is unknown

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