Date of Thesis

2015

Description

The origins of many emerging zoonotic diseases in humans have been traced to bats as natural hosts known to coexist with pathogens without signs of disease. However, the presence of every zoonotic agent is often first identified by the presence of disease in humans, and surveillance for disease emergence is largely restricted to identifying incident cases of disease in humans rather than monitoring infection or disease among wildlife. Understanding how bat health and immunity vary by factors such as sex, age, reproductive class, and season is important for understanding variations in spillover risk and for mitigating such risk through conservation. This study assessed the overall health of free ranging little epauletted fruit bats (Epomophorus labiatus) by measuring multiple parameters such as body mass indices (BMI), percentage total white blood cell (WBC) counts, chiropteran malaria parasite infections (Hepatocystis sp.), analysis of blood chemistry, and through measuring the response to challenge with phytohemagglutinin (PHA). Bats were trapped from South Sudan during wet seasons of 2010 and 2011 and in dry season of 2015. Morphological measurement for calculating body condition were taken, blood samples drawn to determine total WBC counts and screen for malaria parasitemia. For the bats sampled in 2015, (i) blood samples were additionally analyzed for blood electrolyte, hydration and acid-base parameters using VetScan i-Stat machine; and (ii) bats were subjected to an immune challenge by injecting them with PHA and PBS used as control. Results showed that bats were in better body condition in the wet versus the dry season, with females in better condition than males across season, although higher mean total WBC counts and parasite loads were registered during the dry season. Blood chemistry analysis from 100% of bats sampled revealed many conditions of imbalance, relative to standardized mammalian values, ranging from electrolyte depletion, dehydration, starvation, azotemia (renal failure), and metabolic acidosis and alkalosis. All bats mounted significant swelling responses to PHA injection but the magnitude of this response was greater in females than males, with no difference between pregnant and non-pregnant females. These results indicate that free ranging bats face challenges from the environment which in turn might predispose them to pathogenic infections during certain life cycle stages like pregnancy. The findings also suggest that responses of the immune mechanism of bats to disease may be influenced by different ecological parameters and life history traits, which may vary by species. Combining multiple techniques to approach the studies of health and immunity in bats and how bat immune mechanisms respond when encountered by pathogens is recommended.

Keywords

Health in bats, Immunocompetence, Epomophorus labiatus, PHA challenge, Hematology, Bat malaria, Disease ecology, South Sudan

Access Type

Masters Thesis (Bucknell Access Only)

Degree Type

Master of Science

Major

Biology

First Advisor

DeeAnn Reeder

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