Blood Parasites and Health Status of Hibernating and Non-Hibernating Noctule Bats (Nyctalus noctula)

Abstract

Co-existence of bats with a wide range of infectious agents relates to their co-evolutionary history and specific physiology. Here, we examined blood samples collected during hibernation and the post-hibernation period to assess the influence of trypanosomes and babesias on the health status of 50 Noctule bats (Nyctalus noctula) using nested PCR. The impact of blood parasites on health was assessed by analysis of haematology and blood chemistry parameters in 21 bats. Prevalence of trypanosomes (Trypanosoma dionisii and T. vespertilionis) and babesia (Babesia vesperuginis) was 44% and 8%, respectively. Analysis of blood parameters indicated impact of babesia on acid-base balance. Blood chemistry parameters showed a significant decrease in total dissolved carbon dioxide and bicarbonate, increased anion gap, and no change in blood pH, suggesting compensated metabolic acidosis. Adverse effects of babesia were only apparent in hibernating bats. Our results suggest differences in the pathogenicity of trypanosomes and babesia in bats. While trypanosomes in general had no significant impact on the health status, we observed alterations in the blood acid-base balance in Babesia-infected bats during hibernation. Despite being infected, Babesia-positive bats survived hibernation without showing any clinical signs.

Keywords: Babesia vesperuginis; Chiroptera; Schizotrypanum; Trypanosoma dionisii; Trypanosoma vespertilionis; acid–base balance; blood chemistry; haematology.

Figure 1

Trypanosoma dionisii in a blood smear from a Noctule bat female in hibernation (Giemsa staining, magnification of 1000×).

Figure 2

Babesia vesperuginis in a blood smear from a heavily infected Noctule bat female with acid–base imbalance in hibernation (Giemsa staining, magnification of 1000×).

Figure 3

Differences of (A) total carbon dioxide values (negative–Babesia-negative, B. vesperuginis–Babesia-positive, p = 0.001589), (B) bicarbonate values (negative–Babesia-negative, B. vesperuginis–Babesia-positive, p = 0.002188), (C) anion gap values (negative–Babesia-negative, B. vesperuginis–Babesia-positive, p = 0.003313) and (D) eosinophils (negative–Babesia-negative, B. vesperuginis–Babesia-positive, p = 0.020801) in blood of a Babesia-positive bats in hibernation; * = p < 0.05, ** = p < 0.01.