The incursion, persistence and spread of peste des petits ruminants in Tanzania: epidemiological patterns and predictions.

Peste des petits ruminants virus, which causes a severe disease in sheep and goats, has only recently been officially declared to be present in Tanzania. An epidemiological study was carried out between September 2008 and October 2010 to investigate the incursion, persistence and spread of the virus in Tanzania. The investigation involved serosurveillance, outbreak investigation and computation of epidemiological indices such as the effective reproductive number, persistence and the threshold level for vaccination. Field and molecular epidemiological techniques were applied to isolate, characterise and trace the origin of the virus in Tanzania. A total of 2182 serum samples from goats and 1296 from sheep from 79 villages across 12 districts were investigated. Village-level prevalence of infection was variable (0.00% ­ 88.00%) and was higher in pastoral than in agro-pastoral villages. The overall antibody response to the virus was 22.10% (CI95% = 20.72% ­ 23.48%). About 68.00% and 73.00% of seropositive goats and sheep, respectively, did not show clinical signs. The proportion of seropositive animals differed significantly (p ≤ 0.001) between age groups, sex and farming practices. Real-time polymerase chain reaction results showed that the isolated strains belong to lineage III, whose origin is in East Africa and the Middle East. This indicates that one of the northern neighbouring countries is most likely the source of infection. The computed overall effective reproductive number, the threshold level of vaccination necessary to eradicate the disease and persistence were 4.75% and 98.00%, respectively. These estimates indicate that achieving elimination of the peste des petits ruminants virus from pastoral flocks will require significant effort and development of highly effective intervention tools.

Epidemiological perspectives of ticks and tick-borne diseases in South Sudan: cross-sectional survey results.

A cross-sectional study was conducted between September and October 2010 in five states of South Sudan that were selected on the basis of the perceived risk of tick-borne diseases. The purpose was to investigate epidemiological parameters of tick-borne diseases in South Sudan and their uses in future control strategies. A total of 805 calves were assessed by clinical, microscopic and serological examination and tick counts. The indirect Enzyme-Linked Immuno-Sorbent Assay (ELISA) was used to detect antibodies to Theileria parva, Theileria mutans, Anaplasma marginale and Babesian bigemina. Sero-conversion risks for T. parva and T. mutans were 27.3% and 31.3% respectively, whilst the risk was 57.6% and 52.8% for A. marginale and B. bigemina, respectively. Major tick species identified include Rhipicephalus appendiculatus, Rhipicephalus decoloratus, Rhipicephalus microplus, Amblyomma variegatum, and Rhipicephalus evertsi. There was great variation (P ≤ 0.001) in the number of all these ticks, both between herds in a state and between calves in an individual herd. The low and intermediate sero-conversion risks observed in the study states suggest that immunisation against East Coast fever (ECF) is justified. Fortunately, three major genotypes that were identified by applying Polymerase Chain Reaction Restriction Fragment Length Polymorphism (PCRRFLP) analysis on the p104 to the blood samples and T. parva Muguga, matched very well with T. parva Kiambu 5 and T. parva Muguga; therefore the Muguga cocktail can be used for the immunisation of cattle in South Sudan. However, prospective studies are required to develop optimal control measures for tick-borne diseases under different ecological and husbandry practices in South Sudan.

Are we prepared for emerging and re-emerging diseases? Experience and lessons from epidemics that occurred in Tanzania during the last five decades.

This paper reviews preparedness for containing and controlling emerging and re-emerging diseases drawing lessons from disease events that occurred in animal and human populations in the last five decades (1961-2011). A comprehensive analysis based on retrieval and analysis of grey and published literature as well as reported cases was carried out to document type and trend of occurrence of emerging and re-emerging infectious diseases in different parts of Tanzania. Overall, the majority of diseases reported in the country were viral in nature followed by bacterial diseases. The trend for the occurrence shows a number of new emerging diseases as well as re-occurrence of old diseases in both animal (domestic and wild) and human populations. In humans, the major disease epidemics reported in the last five decades include cholera, influenza A H1N1, plague and rubella. In animals, the major epidemic diseases reported were Contagious Bovine Pleuropneumonia, Contagious Caprine Pleuropneumonia, Peste des petits ruminants and Giraffe Ear and Skin Diseases. Some epidemics have been reported in both human and animal populations including Rift Valley fever and anthrax. The emergence of the 'fit-for purpose' approaches and technologies such as the discipline of One Health, use of participatory epidemiology and disease surveillance and mobile technologies offers opportunity for optimal use of limited resources to improve early detection, diagnosis and response to disease events and consequently reduced impact of such diseases in animal and human populations.