The Control of Rinderpest in Tanzania between 1997 and 1998

In January 1997, Tanzania requested international assistance against rinderpest on the grounds that the virus had probably entered the country from southern Kenya. Over the next few months, a variety of attempts were made to determine the extent of the incursion by searching for serological and clinical evidence of the whereabouts of the virus. At the clinical level, these attempts were hampered by the low virulence of the strain, and at the serological level by the lack of a baseline against which contemporary interpretations could be made. Once it became apparent that neither surveillance tool was likely to produce a rapid result, an infected area was declared on common-sense grounds and emergency vaccination was initiated. The vaccination programme had two objectives, firstly to prevent any further entry across the international border, and secondly to contain and if possible eliminate rinderpest from those districts into which it had already entered. On the few occasions that clinical rinderpest was subsequently found, it was always within this provisional infected area. Emergency vaccination campaigns within the infected area ran from January to the end of March 1997 but were halted by the onset of the long rains. At this time, seromonitoring in two districts showed that viral persistence was still theoretically possible and therefore a second round of emergency vaccination was immediately organized. Further seromonitoring then indicated a large number of villages with population antibody prevalences of over 85%. These populations were considered to have been `immunosterilized'. Although no clinical disease had been observed in them, it was decided to undertake additional vaccination in a group of districts to the south of the infected area. Serosurveillance indicated that rinderpest could have been present in a number of these districts prior to vaccination. Serosurveillance in 1998 suggested that numerous vaccinated animals had probably moved into districts outside the infected and additional vaccination areas, but did not rule out the continued presence of field infection.     

Effect of Immunization with Plasmid DNA Encoding for Rinderpest Virus Matrix Protein on Systemic Rinderpest Virus Infection in Rabbits

Plasmid vaccine pBK-CMVMP1LC113 expressing the matrix (M) gene of rinderpest virus was assessed for its potential to protect rabbits against a lethal viral challenge. Rabbits immunized with plasmids expressing the M gene were not protected when challenged with lapinized rinderpest virus, despite the production of anti-M antibodies, while rabbits immunized with rinderpest tissue culture vaccine were completely protected from a lethal challenge with lapinized rinderpest virus. The plasmid vaccine also had no significant effect on the lymphopenia in challenged rabbits. The results indicate that rinderpest M protein does not have a protective role in rinderpest infection.     

Production and Characterization of Monoclonal Antibodies to Peste des Petits Ruminants (PPR) Virus

Peste des petits ruminants (PPR) is an acute, febrile viral disease of small ruminants, caused by a virus of the genus Morbillivirus. PPR and rinderpest viruses are antigenically related and need to be differentiated serologically. In the present study, 23 mouse monoclonal antibodies were produced by polyethyleneglycol (PEG)-mediated fusion of sensitized lymphocytes and myeloma cells. Among these, two belong to the IgM class and the remaining 21 to various subclasses of IgG. The MAbs from the IgG class designated 4B6 and 4B11 neutralized PPR virus in vitro. In radioimmunoprecipitation assay, 10 MAbs recognized nucleoprotein, 4 recognized the matrix protein and one each haemagglutinin and phosphoprotein. The remaining 7 MAbs failed to precipitate any defined viral protein. The reactivity pattern of the monoclonal antibodies in indirect ELISA indicated a close antigenic relationship within three Indian PPR (lineage 4) virus isolates and also within two rinderpest vaccine strains. All PPR virus isolates could be distinguished from rinderpest vaccine viruses on the basis of the reactivity pattern of all MAbs and anti-N protein MAbs. A set of six monoclonal antibodies specific to PPR virus could also be identified from the panel. From the panel of MAbs available, two MAbs were selected for diagnostic applications, one each for the detection of antigens and antibodies to PPR virus.     

Detection of Rinderpest Virus Using N-Protein Monoclonal Antibodies

A panel of monoclonal antibodies (mAbs) was generated against the RBOK strain of rinderpest virus (RPV). All of them bound to the N protein of RPV. The antigen capture ELISA using the mAbs could detect the virus in crude viral preparations. The mAb 12BF8.1.1 showed higher reactivity with cell-associated (CA) virus, whereas the mAbs 12AD10.1.1, 12BD7.1.1 and 12DG7.1.1 showed higher reactivity with extracellular virus (hereafter referred to as cell-free (CF) virus). The mAbs 12BF8.1.1 and 12AD10.1.1 could detect the virus in infected Vero cell culture supernatants (CCS) as early as 24 h post-cytopathic effect (CPE) initiation. Detergent treatment (Triton X-100) of RPV preparations enhanced the binding of the mAbs to the virus. All the seven mAbs showed specific fluorescence in virus-infected cell cultures. The immunofluorescence (IFA) using mAbs was found to be more sensitive and reliable than the immunoperoxidase test (IPT) for detection of rinderpest.     

Rinderpest Vaccination and the Incidence and Development of Trypanosomosis in Cattle

An investigation was made into whether recent vaccination of cattle with tissue culture rinderpest virus would cause immunosuppression and lead to more frequent or more severe infection with trypanosomes in animals grazing in tsetse-infested areas. Herds of cattle on Galana Ranch in Kenya were divided, with approximately half of each herd being vaccinated with tissue culture rinderpest virus strain Kabete O, while the rest remained unvaccinated. The herds were then exposed to the risk of natural infection with trypanosomes on the ranch. Three experiments were performed during different seasons. Infections with Trypanosoma congolense and Trypanosoma vivax were frequently detected but there was no evidence that vaccinated animals were more likely to acquire trypanosome infections or to show a more severe disease than unvaccinated cattle. It is concluded that tissue culture rinderpest vaccine does not cause immunosuppression and can safely be used in cattle likely to be exposed to tsetse flies and trypanosomosis.     

Diagnosis of Rinderpest in Tanzania by a Rapid Chromatographic Strip-test

A simple chromatographic strip-test based on Clearview technology, is under development as a pen-side test for the detection of rinderpest antigen in eye swabs taken from cattle in the field. An outbreak of rinderpest occurred in the northern zone of Tanzania from late February to June 1997. The affected cattle exhibited very mild clinical signs, which made clinical diagnosis difficult. One hundred and seven eye swabs were collected from cattle suspected of infection with rinderpest. These were tested in the field using a prototype of the pen-side test and 13 (12.15%) of the samples were found to be positive for the presence of rinderpest antigen. These were confirmed by ICE. The positive cases were predominantly found in the Ngorongoro district. This demonstrates the usefulness of such a simple, rapid pen-side diagnostic assay, particularly when clinically `mild' strains of rinderpest are present.     

Rinderpest Antibody Detected in Sheep and Goats Before an Outbreak of Rinderpest Reported in Cattle in Northern Tanzania

In January 1997, serum samples from 1346 adult sheep and goats were tested by a competitive ELISA to determine the prevalence of rinderpest in the northern zone of Tanzania. Seroconversion rates of 20%, 13%, 9%, 7% and 3% in sheep and goats were recorded in Ngorongoro, Monduli, Hai, Arumeru and Simanjiro districts, respectively. The low profile and insidious nature of the rinderpest virus involved caused very mild disease in cattle in some of these area. The mild signs associated with this outbreak of rinderpest resulted in difficulty in its diagnosis. In these circumstances, the presence of rinderpest antibody in sheep and goats served as a valuable and effective indicator of the rinderpest outbreak in cattle.     

Animal Health and Disease Control in the Usangu Wetland of Southwestern Tanzania

The Usangu Wetland in the Southern Highlands of Tanzania has always been a major livestock production area. This paper describes the physical and social enviroment of these Plains before presenting a short history of the veterinary services in the area. The main part of the paper examines, through historical records and interviews with livestock owners and administrative officials, the history of the major diseases affecting livestock.     

“后牛瘟时代”的全球牛瘟研究

2011年，联合国粮食及农业组织(FAO)和世界动物卫生组织(WOAH)联合宣布根除牛瘟。这是历史上首个消灭的动物疫病，也是继天花之后全球第二个被消灭的传染病，自此，世界进入“后牛瘟时代”。牛瘟再暴发风险依然存在，维持全球牛瘟无疫状态意义重大。就维持全球牛瘟无疫状态的框架性文件、牛瘟病毒保藏机构以及宣布消灭牛瘟后所发表的实验性研究等进行了综述，为提升公众风险意识、应对牛瘟再暴发提供参考。