Anthropogenic activities in ecosystems interfere with natural processes and cause habitat fragmentation and loss. Habitat fragmentation and loss restrict wildlife movement between populations consequently reducing the gene flow and genetic diversity. Increased human encroachment on wildlife habitat compromises immunity and disturbs host-pathogen relationships resulting in disease outbreaks in naïve populations. Tick-borne and infectious diseases are considered a major threat to the health of people and their domesticated animals and as described in this thesis, can cause increased mortality in endangered wildlife species. There is evidence that ecological changes exacerbated by anthropogenic activities are increasing both the threat and economic cost of emerging diseases. The emergence of these diseases is often associated with ecological factors exacerbated by anthropogenic activities. The Serengeti ecosystem is a useful area to study interactions between disease, anthropogenic factors and wildlife because it has some of the largest wildlife populations in Africa and areas surrounding the ecosystem hold some of the highest livestock populations in Tanzania which can interact freely with wildlife in some areas. The area surounding the ecosystem is occupied by about 2 million people; agro-pastoralists in the west and pastoralists in the east who are competing with wildlife for limited resources. This is an ideal condition for disease spillover to susceptible animals or humans.
I start this thesis with a description of the first major veterinary intervention to treat free ranging black rhinos (Diceros bicornis) in the Ngorongoro Crater (hereafter referred to as Crater) against a perceived threat by tick-born diseases in 2001. From this initial disease problem in rhino I developed a research interest in tick ecology which was followed by a detailed investigation of tick ecology, vegetation structure and effect of prescribed fire management that were conducted in the Crater grassland. My interest in tick ecology led me to apply molecular methods to investigate the blood parasites in ticks collected from Crater grassland and on animals. My interest in wildlife diseases prompted me to participate in efforts to identify the cause of the appearance of disease in the spotted hyena (Crocuta crocuta) population in the Crater in 2002. Bacteriological histopathological and molecular analyses were performed on tissue samples collected from dead spotted hyenas in the Crater. News of sick and dying African wild dogs (Lycaon pictus) in one pack in 2007 in the Loliondo Game Control Area (LGCA) prompted me to investigate the problem in this pack, and observation of dying animals suggested to me that the pack was infected with canine distemper virus and I decided that this should be verified by histopathology and genetic analyses. A cross-sectional retrospective study was organized for sero-prevalence of Brucella micro-organism in buffalo (Syncerus caffer) and wildebeest (Connochaetus taurinus) in the Serengeti ecosystem using Rose Bengal Plate Agglutination test followed by competitive ELISA.
My results show that a cascade of ecological changes in the Crater grassland caused by anthropogenic and natural influences were the underlying factors associated with the wildlife mortality. The study on tick ecology revealed an unusually high tick density of 42 and 819 per square meter for adults and immature ticks respectively, in unburned Crater grassland, consisting of about 15 tick species. Tick-borne diseases contributed to the mortality of a number of herbivores and carnivores in the Ngorongoro Crater in year 2000/ 2001. It was observed that nine out of 15 tick species were found to contain at least one or more of infectious haemoparasites. Gradual change in the Crater ecology partly caused by good intention of the NCAA Management to relocate the Maasai and prohibiting burning of the Crater grassland for almost three decades (27 years) were probably the contributing factors for the change in herbivore composition in favour of buffalo and decrease in small herbivores particularly wildebeest. This change occurred concurrently with change in vegetation structure and composition which favoured more tick survival leading to high tick infestation in the Crater grassland and on animals. The study described for the first time, detection of the blood parasite Anaplasma bovis in the tick species Amblyomma gemma and Rhipicephalus praetextatus in Tanzania. Mycoplasma haemofelis and Candidatus Mycoplasma haemominutum were also detected in Rhipicephalus sanguineus ticks collected on lions (Panthera leo) from Ngorongoro Crater. The study reported the highest diversity of tick species (six) detected with Anaplasma marginale including Rhipicephalus praetextatus and Rhipicephalus pulchellus which were previously not described to be of importance as disease vectors in Tanzania.
Similarly, Streptococcus equi subsp.ruminatorum, a bacterium previously described in domestic stock in Europe was identified as the causative agent of severe infection and increased mortality in the spotted hyena population in the Crater in 2002/ 2003. Canine distemper virus (CDV) was identified as the causative agent of high mortality in one wild dog pack in the LGCA in 2007. Genetic sequence data showed this virus to resemble the CDV strain that killed 30% of lions in the Serengeti in 1993/94. A number of other disease pathogens have been discussed that are associated with various anthropogenic activities onto naïve wildlife populations during encroachment onto natural ecosystems.