PhD-ThesisPeste des petits ruminants (PPR) is a highly contagious transboundary animal disease of domestic small ruminants, camels and some wild artiodactyls. It is caused by Small ruminant morbillivirus (PPRV) of the family Paramyxoviridae classified into four genetically distinct lineages I, II, III and IV; and shares genetic and antigenic characteristics with rinderpest (RP) virus. The disease has significant socio-economic impact on communities which largely depend on livestock for livelihood, and is a threat to endangered susceptible wild species. This study aimed at investigating the spread and maintenance of PPR in the pastoral and agropastoral communities characterized by extensive mobility, in some areas interacting with wildlife, in order to generate necessary information for proper planning of control and eradication strategies for PPR. A Cross sectional studies, complimented with review of previous studies were carried out during the present study. Data collected from livestock and wildlife populations, samples collected from different agro ecological zones and wildlife from different habitats were involved in the study. In ecological studies, purposive sampling was performed in sheep and goats from 32 districts where PPR surveillance had never been carried out after the confirmation of PPR in Tanzania. The 32 districts involved in the study, included 3 (9.4%), 12 (37.5%) and 17 (53.1%) districts from the coast, semi-arid and plateau ecological zones, respectively. For epidemiological characterization of PPR, a total of 78 flocks of sheep and goats were investigated from Karatu (n=10), Longido (n=9), Meatu (n=7), Monduli (n=11), Ngorongoro Conservation Area Authority (NCAA) (n=13), Ngorongoro (n=18) and Serengeti (n=10).iii For the investigation of PPR seroprevalence in wildlife from different habitats, four species of wildlife; buffalos (Syncerus caffer), impalas (Aepyceros melampus), Grant’s gazelles (Nanger granti) and Thomson’s gazelles (Eudorcas thomsonii) were sampled. Sample sizes were calculated based on wildlife population obtained from TAWIRI aerial census of 2009 and 2010. PROMESA software (http://www.promesa.co .nz/ProMESA.htm) was used to estimate sample size per location in three types of wildlife habitats. Habitats were selected based on the level of contacts with wildlife. The habitats included Serengeti National Park (SNP) - designated only for wildlife, Loliondo Game Controlled Area (LGCA) - designated for wildlife livestock and other human activities and Ngorongoro Conservation Area Authority (NCAA) - designated for wildlife and livestock only. Chemical immobilization technique was used to capture buffalos and impalas, whereas gazelles were captured by using a modified netting technique, with trap made using locally available materials. With this technique three vehicles were used to head the animals towards the trap. All collected samples from livestock and wildlife were analysed at the SACIDS laboratory of Sokoine University of Agriculture. On ecological studies, the overall seropositivity across all agro ecological zones based on c-ELISA was 20.1%, of which 18.8%, 9.4%, 37.5% and 34.4% districts had very high, high, low and zero PPR seroprevalence respectively. Very high and high seroprevalence were frequently recorded in the semi-arid districts. Zero and low seroprevalence were mostly observed in districts from plateaux ecological zone. Statistically there were significant differences in PPR seroprevalences among districts of different ecological zones. On PPR outbreak characterization in the Serengeti ecosystem, a total of 160 samples were collected from clinically diagnosed cases, out of which 12 and 11 cases were confirmed using a lateral flow device (LFD) and real time reverse transcription polymerase chain reaction (qRT-PCR) tests, respectively. Of the confirmed cases aboutiv 60% of the animals were aged below six months of age with body temperature ranging from 38.5 to 41.3 o C, about 70% had lacrimation and only 45.5% had diarrhoea. Lineage III of PPRV was found to be circulating in the area. Semi structured interviews indicated pastoral communities were aware of PPR syndromes and had traditional names and remedies unlike in the agropastoral communities who mostly used Swahili terminologies. There was no clinical case of PPR observed in the 3 different wildlife habitats. However, a cross sectional survey was conducted to determine the seroprevalence of PPR in wildlife species. A total of 270 wildlife were captured, 26 (9.6%) from LGCA, 75 (27.8%) from NCAA and 169 (62.6%) from SNP, out of which two (7.7%), seven (9.3%) and 30 (17.8%) were seropositive, respectively. Results for one (3.8%), six (8%) and 42 (24.8%) animals from LGCA, NCAA and SNP, respectively, were doubtful. There were no statistically significant differences in seropositivity between habitats, species, age and sex. A modified netting technique developed and used during the present study, showed high animal and operator safety levels with minimal injuries compared to previous techniques. With this technique it was possible to capture even flighty animals that behave nervously because of hunting and other human activities, including Thomson’s gazelles (Eudorcas thomsonii), a species previously found to be difficult to capture by netting. Peste des petits ruminants was introduced in Tanzania before its confirmation in 2008 in northern Tanzania and has been spreading into different areas of the country through live animal trade and pastoralist migration. Seroprevalence of the disease in sheep and goats has been found to be higher in semi-arid agro-ecological zone. Peste des petits ruminants outbreak characterization in areas where livestock coexist with wildlife indicated age, temperature and lacrimation to be important components of the case definition for PPR syndromic diagnosis. Lineage III was found to be the lineage circulating at the moment in the area.v Although no clinical cases of PPR were observed in wildlife, PPR antibodies have been recovered in wildlife coexisting with livestock confirmed to have PPR cases which indicates that at one point wild animals contracted the virus. There was no statistically significant difference in the PPR seroprevalence between wildlife coexisting with livestock and those with no contact with livestock. Therefore, surveillance, prevention, control and eradication strategies for PPR should consider the agroecological zones favouring survival and perpetuation of the virus among reservoir hosts and the susceptible populations in these areas. Pastoral and live animal traders’ movements need to be considered in planning and implementation of PPR control strategies. Veterinary services and conservation authorities are encouraged to work together on planning PPR surveillance and control at different levels. On syndromic diagnosis of PPR in endemic settings need to consider age, body temperature and lacrimation on case definition. For species other than sheep and goats the c-ELISA test kits need to be validated as there were higher levels of doubtful results on laboratory analysis in wildlife samples.