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

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.

Endemisation and management of Babesia divergens on a beef production farm

“…Although a lower number of ticks was collected in October compared to May, especially regarding adult females, the seasonal detection frequency was almost equal with 1.0% and 0.7%, respectively. A similar prevalence of 1.0% B. divergens -infected I. ricinus nymphs was determined in a recent study from Ireland, a country particularly affected by bovine babesiosis ( McKiernan et al, 2022 ). This confirms the endemisation of B. divergens in the farm’s tick population and may indicate an increase in prevalence between the two surveys, which might be expected due to transovarial transmission in ticks ( Joyner et al, 1963 ; Donnelly and Peirce, 1975 ).…”

“…The pastures border a nature reserve, which is a popular tourist destination with many hiking trails. Apart from cattle, red deer have been suggested as potential reservoir hosts ( McKiernan et al, 2022 ), which might be responsible for spreading the pathogen within the area, in addition to translocation of infected ticks by various wildlife.…”