Abstracts of the
Int. Conference on Diseases of Zoo and Wild Animals
Beekse Bergen, May 2009
MORTALITY AND MORBIDITY OF WILD ELEPHANTS (ELEPHAS MAXIMUS MAXIMUS) OF SRI LANKA,
AS A RESULT OF LIVER FLUKES (FASCIOLA JACKSONI) INFESTATION
Perera, BVP1, Rajapakse, RPVJ2
The free ranging elephant (Elephas maximus) population in Sri Lanka is estimated to be around 4,000 and it represents 10 % of the endangered Asian elephants. Gastro-intestinal diseases have been found to be a significant natural cause of mortality and morbidity of elephant calves and adults in Sri Lanka. In this study we investigated the prevalence of Fasciola jacksoni among free ranging elephants in Sri Lanka.
This study was carried out from January 2000 to April 2008. The liver was examined for the presence of adult liver flukes in 84 elephants that died either due to anthropogenic causes or naturally. These post mortems were performed within 48 hours from the time of death. Adult flukes were identified visually and the species was determined through laboratory investigations. The severity of the parasitic infestation in the affected animals was accessed by considering the total number of flukes in the liver. In addition, laboratory investigations for the presence of fluke eggs were carried out for 48 dung samples from the living wild elephants. Parallel to these investigations, pathological investigations of fasciola infestation and life cycle of F. jacksoni were being conducted.
Age categories of the study population were 1 - 5 yrs (6 calves), 6 - 10 yrs (3 juveniles), 11 - 20 yrs (16 sub-adults), 20 - 40 yrs (48 adults) and > 40 yrs (11 prime adults). The sex ratio (male: female) was 61:23. The causes of death consisted of; gunshot associated wounds leading to septicaemia (33), gunshot wounds associated with severe damage to the brain, heart or lungs (9), deaths due to electrocution (11), railway accidents (9), incidences of drowned animals (1), anaesthesia associated deaths (4), respiratory diseases-pneumonia (2), fasciola associated parasitism (2), tape worm infestation (1), other intestinal parasitism (1), old age with severe debility (7), and dead animals in which a cause could not be ascertained (2). The liver flukes found in the elephants were identified as F. jaksoni, of which the average size was 12 - 14 mm x 9 - 12.5 mm. Forty-five animals were found to be infected with the fluke from all age categories. The severity of the infestation was very variable from most severe (> 100 flukes) in 6 animals, moderate (50 - 100 flukes) in 9 animals, mild (10 – 50 flukes) in 11 animals, and low - (< 10 flukes) found in 19 animals. It was clear that the severity of the infection was higher in weaker animals than in healthy animals. Histopathological changes in the affected liver tissue were cholangitis and fibrous tissue proliferation of the wall of the bile duct.
F. jacksoni was identified very recently in Sri Lanka; however this study revealed that it is a common parasite in most parts of the country. Although recorded number of mortalities due to fascioliosis is minimal, it is obvious that fasciolosis has potential to cause a disastrous impact on elephant populations in Sri Lanka. Currently, confining elephants into protected areas is a popular management practice for mitigating human-elephant conflict; however this practice has forced elephants to live in restricted areas with higher densities which is an ideal situation for enhancing the efficiency of the life cycle of F. jacksoni.