Recombinant DNA technology for producing new rinderpest virus vaccines

With few exceptions, vaccination aims to control rather than eliminate or eradicate disease. The eradication of smallpox in the 1970s led to two other human diseases, polio and measles, being targeted for eradication by the World Health Organization. In general, animal diseases are ignored by the public, however, recent targeting of the rinderpest virus, the agent of cattle plague, has put this virus on the verge of global extinction. For centuries, this virus was responsible for major cattle plagues in Europe, Asia and Africa. The success of the Global Rinderpest Eradication Program is an illustration of the power of vaccines to alter people's lives economically and socially when used in an internationally coordinated way. In this review, the history of the development of rinderpest vaccines and the new research being undertaken to produce marker vaccines, using recombinant DNA technology and reverse genetics, are described. In addition, the valuable contribution that marker vaccines can make in the final stages of the rinderpest eradication program is outlined.

A model of lineage-1 and lineage-2 rinderpest virus transmission in pastoral areas of East Africa

The development of a stochastic, state-transition model of rinderpest transmission dynamics is described using parameter estimates obtained from both laboratory and participatory research. Using serological data, the basic reproduction numbers for lineage-1 rinderpest virus in southern Sudan and for lineage-2 rinderpest virus in Somali livestock were estimated as 4.4 and between 1.2 and 1.9, respectively. The model predictions for the inter-epidemic period in Sudan and Somalia (1.2 and 4.2 years, respectively) were in agreement with analysis of livestock-owner reports (1-2 years and 5 years, respectively).

Long term immunity in African cattle vaccinated with a recombinant capripox-rinderpest virus vaccine

Cattle were vaccinated with a recombinant capripox-rinderpest vaccine designed to protect cattle from infection with either rinderpest virus (RPV) or lumpy skin disease virus (LSDV). Vaccination did not induce any adverse clinical responses or show evidence of transmission of the vaccine virus to in-contact control animals. Approximately 50% of the cattle were solidly protected from challenge with a lethal dose of virulent RPV 2 years after vaccination while at 3 years approx. 30% were fully protected. In the case of LSDV, all of 4 vaccinated cattle challenged with virulent LSDV at 2 years were completely protected from clinical disease while 2 of 5 vaccinated cattle were completely protected at 3 years. The recombinant vaccine showed no loss of potency when stored lyophylized at 4 degrees C for up to 1 year. These results indicate that capripoxvirus is a suitable vector for the development of safe, effective and stable recombinant vaccines for cattle.

Global eradication of rinderpest. Yea or nay?

Rinderpest is a scourge continuing to change the course of history. The German "Rinderpest" in English fails to convey the spectre of Death, Despair and Desolation long associated with the disease. Although the causal morbillivirus cross-protects against other morbillivirus, there is only one rinderpest serotype which is both immuno-suppressive and immunogenic. Safe vaccines induce lifelong protection in cattle. Transmission follows close contact between sick and healthy artiodactyls. Infectious periods are short and deaths may be curtailed by liberal fluid replacement therapy. Carriers do not exist. In other words rinderpest is a prime candidate for eradication. Why has it not happened? The major obstacle is "man's inhumanity to man". Rinderpest thrives in a milieu of armed conflict and fleeing refugee masses. Until world peace is secured, the "Nays" win the argument.

Animal health risks associated with the transportation and utilisation of wildlife products

The animal health risks associated with the movement of wildlife products are infinitely less than those associated with the movement of live animals. Very few pathogens are sufficiently robust to survive the significant changes in temperature, pH, moisture content and osmolality which occur post mortem, or which are associated with preservation processes such as pickling, smoking or drying. Certain pathogens, however, (e.g. foot and mouth disease, classical swine fever [hog cholera] and African swine fever viruses and the anthrax bacillus) are hardy and resistant to these environmental changes and therefore constitute a finite animal health risk if raw, undercooked or under-preserved products from infected wild animals are imported. Other less robust pathogens, such as rinderpest virus, may remain infectious in animal products if these are obtained from acutely infected animals and frozen immediately. Macroparasitic diseases such as trichinellosis and echinococcosis-hydatidosis, if present in the unprocessed tissues of infected wildlife, are potentially infectious to carnivorous or omnivorous companion animals. The importation of untreated wet hides may result in the introduction of alien ectoparasites and/or the infectious diseases for which they are vectors. The author discusses the more significant pathogens found in free-ranging wildlife which should be taken into consideration when importing wildlife products from endemically or epidemically infected countries.

Trial of a capripoxvirus-rinderpest recombinant vaccine in African cattle

Cattle were vaccinated with differing doses of an equal mixture of capripox-rinderpest recombinant viruses expressing either the fusion protein (F) or the haemagglutinin protein (H) of rinderpest virus. Animals vaccinated with 2 x 10(4) p.f.u. or greater of the combined viruses were completely protected against challenge, 1 month later, with both virulent rinderpest and lumpy skin disease viruses. Vaccination with any of the doses did not induce any adverse clinical response in the animals or transmission of the vaccine virus between animals. All cattle challenged 6 or 12 months after vaccination with 2 x 10(5) p.f.u. of the mixture of recombinant viruses were protected from severe rinderpest disease. Ten out of 18 were completely protected while the remaining 8 developed mild clinical signs of rinderpest. Cattle vaccinated with the recombinant vaccines after prior infection with the parental capripox virus showed more marked clinical signs of rinderpest after challenge with virulent rinderpest, but 9 out of 10 recovered, compared with 80% mortality in the unvaccinated controls.

Rinderpest: at war with the disease of war

Rinderpest, the legendary cattle plague, has caused devastating losses for centuries and remains the biggest threat to sustainable livestock production in developing countries. Strenuous efforts are now being made to achieve global eradication of this viral disease, a goal made feasible through the use of attenuated live vaccines developed in the 1950s. Their use almost resulted in eradication in the 1970s but left several foci of disease from where the plague then re-emerged. Recent mass vaccination has resulted in the limitation of disease to parts of Africa, Pakistan, Afghanistan, the Middle East and India. Confirmation of the disease status of the countries has been aided by developments in serological techniques through exploitation of monoclonal antibodies (in Enzyme Linked Immunosorbent Assay-ELISA) and by advances in molecular biology such as in the use of polymerase reaction technologies (PCR). This has extended into the development of new recombinant vaccines. It is anticipated that eradication will be complete by the year 2010. This would be only the second example, after smallpox in man, of the eradication of a viral disease. The picture shows a scene of devastation during the Great Rinderpest Pandemic of 1889-1897 in South Africa. The disease swept through the African continent killing virtually all the cattle and wild ungulates.

Protection of goats against rinderpest by vaccination with attenuated peste des petits ruminants virus

The ability of the attenuated peste des petits ruminants vaccine virus to protect small ruminants against virulent rinderpest virus was investigated. Out of four susceptible goats that were infected with the highly virulent Saudi strain of rinderpest virus by intranasal ioculation, three developed mild clinical signs of disease and infected susceptible in-contact goats and cattle with rinderpest virus. However, four goats which had been vaccinated with the attenuated peste des petits ruminants virus resisted challenge with virulent rinderpest virus and did not infect susceptible in-contact animals.

Observations on the pathogenicity for sheep and goats and the transmissibility of the strain of virus isolated during the rinderpest outbreak in Sri Lanka in 1987

The pathogenicity for sheep and goats of the virus strain that caused acute rinderpest in cattle and domestic buffalo in Sri Lanka after an interval of over 40 years has been examined. The results show that it can cause overt clinical disease in goats, but only mild or unapparent infection in sheep. The disease was transmitted from infected sheep to in-contact susceptible sheep and calves.

An epidemiological model of rinderpest. II. Simulations of the behaviour of rinderpest virus in populations

Fixed parameters for different hypothetical strains of rinderpest virus (RV) and different susceptible populations are described together with details of their derivation. Simulations were then carried out in a computer model to determine the effects that varying these parameters would have on the behaviour of RV in the different populations. The results indicated that virulent strains of RV are more likely to behave in epidemic fashion whereas milder strains tend towards persistence and the establishment of endemicity. High herd immunity levels prevent virus transmission and low herd immunity levels encourage epidemic transmission. Intermediate levels of immunity assist the establishment of endemicity. The virus is able to persist in large populations for longer than in small populations. Different vaccination strategies were also investigated. In areas where vaccination is inefficient annual vaccination of all stock may be the best policy for inducing high levels of herd immunity. In endemic areas and in herds recovering from epidemics the prevalence of clinically affected animals may be very low. In these situations veterinary officers are more likely to find clinical cases by examining cattle for mouth lesions rather than by checking for diarrhoea or high mortalities.

Use of the caprinised strain of rinderpest virus for potency testing an attenuated cell culture rinderpest vaccine

The caprinised strain of rinderpest virus was inoculated into goats to produce a challenge stock. These goats were kept with control animals (goats, sheep, calves). In this trial the caprinised strain was shown to have a mild pathogenicity for goats and it spread to one of two contact goats but not from goats to other species. The caprinised strain was then tested on cattle where a febrile reaction was observed. The caprinised strain also did not spread between cattle. The cattle vaccinated with a freeze-dried vaccine produced from the attenuated Kabete RBKO strain on bovine kidney cells were then challenged with the caprinised strain with good results.