Date of Award

2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biology

Abstract

The overall health of an individual or population can be measured in various ways. This research investigates bat health and reports baseline values of 1) hematological measures, 2) ectoparasite and endoparasite indices, and 3) prevalence of a zoonotic bacterium Bartonella , in four bat species, including big brown bat ( Eptesicus fuscus ), eastern red bat ( Lasiurus borealis ), Indiana bat ( Myotis sodalis ), and the evening bat ( Nycticeius humeralis ) that I captured at six state-protected sites in northeastern Missouri, USA over three summers. Such baseline values are needed, for example, when comparing diseased and stressed animals to healthy individuals or when comparing individuals from anthropogenically altered habitats to those from reference populations. However, relatively few studies report such values for North American bats. Here I report descriptive statistics to provide these baseline measures. I also used an information theoretic modeling approach to evaluate variation in the health measures as a function of demographic groups (age, sex, reproductive condition) and time intervals (summer months, years). My hematological measures included differential white blood cell counts and the neutrophil to lymphocyte (N:L) ratio, which can be elevated under infections and stressful events. My parasite indices included measures of prevalence, indicating how prevalent a parasite is in a population, and two measures of parasite loads (abundance, intensity), which indicate how heavily infected bats are in a population. I also examined the prevalence of the Bartonella bacterium, which is important as it can threaten bats, other wildlife populations, and humans. In Study 1, I documented descriptive statistics and models explaining the variation in the N:L ratio and the white blood cell counts. I found that variation was best explained by age, sex, reproductive condition (adult female and all male), summer month, and year, although the specific combination of these factors differed somewhat for the bat species. However, adults and females generally had higher N:L ratios than juveniles and males. In Eptesicus fuscus , a sex and month interaction term revealed that females from June had higher N:L ratios than females from August. In Study 2, in evaluating ectoparasites, I found some consistent patterns across three of the four bat species in the differences in ectoparasite indices among some demographic groups. For example, juveniles and females had higher mite (both prevalence and abundance) and bat bug (prevalence) indices compared to adults and males. However, I observed the opposite pattern in ticks; male Eptesicus fuscus had a higher prevalence of ticks than females. Additionally, the intensity of mites was best explained by predictor variables age, sex, and summer months in Eptesicus fuscus and Nycticeius humeralis . In contrast to ectoparasites, patterns in demographic groups for the endoparasite indices appeared to vary more across bat species, with higher indices in males than females for two species ( Nycticeius humeralis , L. borealis ) and the opposite for a third ( Myotis sodalis ). Also contrary to ectoparasites, I observed a higher prevalence and abundance of endoparasites in adults than juveniles in Nycticeius humeralis . Finally, I could not determine what best explained endoparasite intensity based on the models I had created. In Study 3, I describe how I extracted Bartonella DNA from 309 dried blood dot blots using a nested PCR targeting the citrate synthase gene ( gltA ). Confirmed with Sanger sequencing, I detected Bartonella in seven Myotis sodalis samples, yielding a prevalence of 17% (7/42). Some of the sequences from Myotis sodalis closely resembled strains from human samples. Although small sample sizes, there was approximately similar annual prevalence in two summers suggests persistent Bartonella presence, and I found a significantly higher prevalence of mites in the Bartonella -infected Myotis sodalis (43%) compared to the uninfected Myotis sodalis (26%) but no differences in prevalences of ticks or bat bugs. I also found that both monocyte and basophil counts were higher in infected bats compared to uninfected bats. I did not detect Bartonella in the other three species of bats, Eptesicus fuscus (N=179 blood samples), Lasiurus borealis (N=31), or Nycticeius humeralis (N=57). Overall, this research contributes to our understanding of the immunological and parasite dynamics of these North American bat species and also provides baseline data for these health parameters in bats from populations captured in state-protected forested areas embedded in a larger agricultural landscape.

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