Rinderpest

¹⁾ Fig. 1. Cattle scattered across plains in South Africa after epidemic of 1980's.

Rinderpest, also known as the “cattle plague,” was a highly contagious, viral, animal disease that was eradicated from Africa in June of 2011. Also known as RPV, this virus belongs to the family paramyxoviridae, and is related to many other diseases such as the Measles virus in humans.²⁾ Ruminant animals, such as cattle, were affected by this disease which resulted in a major threat to food production.³⁾ Three strains of the virus were identified, two of which came from Africa, and the other coming from Asia.⁴⁾ The signs of Rinderpest differ depending on what strain of the virus, either viral or aviral, the animal possesses, and the physical state which the animal is in.⁵⁾ However, it can be generally seen that the infection of rinderpest causes erosive lesions on the skin, loss of weight, bloody diarrhea, and ultimately death.

Although this disease was eradicated, diagnostic facilities all around the world still contain the rinderpest disease material. With this contained material, the world is potentially at risk of a disease outbreak if for some reason, it would be released. For this reason, the World Organisation for Animal Health as well as the Food and Agricultural Organization of the United Nations are obliged to either destroy the remaining stocks or keep them under extreme international supervision.⁶⁾

Typically there are five different stages that the Rinderpest disease progresses through. The first stage typically begins with a 3-5 day incubation period, allowing the virus to grow and replicate. This then leads into the prodromal stage. In this second stage, a rapid rise in temperature promotes stage three known as the mucosal phase. Here, severe mouth lesions are seen along with nasal and ocular mucopurulent secretions when observing the animals. Additionally, in this phase, it is common for animals become anorexic and depressed, leading into the fourth stage of the viral infection. The fourth stage, known as the diarrheal stage is apparent by several bloody stools that are observed from the animals. This stage typically tends to be the one in which the animal dies. However, if the animals does not die, then the infection proceeds to stage five. In these nonfatal cases, the animal slowly begins to recover over a multiple week time period.⁷⁾ After this recovery phase, the animal will be immune to Rinderpest for the duration of its lifetime.

⁸⁾ Fig. 2. Erosive lesions caused by Rinderpest disease.

The Rinderpest disease was seen to transmit from infected animals to healthy and susceptible animals via large, infected water vapor droplets from the infected animals breath. However, Rinderpest could also be spread through the very virus rich excretions from infected animals. The viral water vapor droplets expelled from the animals are relatively large and short lived. Due to this, a majority of the time, contaminated animals must be in close proximity to healthy animals for the transmission to successfully occur otherwise there is the likelihood the transmission will fail. In rare occasions it was seen that transmission of this disease had occurred through contaminated bedding and water.⁹⁾

The most affected subjects of this viral disease were cattle. During the Great African Pandemic of the 1890's over 2.5 million cattle were killed off. Almost 100 years later, in the 1980's, even with the vaccine readily available, over one million cattle died from the second continental pandemic.¹⁰⁾ Rinderpest is a disease that requires close proximity of its subjects in order for the infection to spread, and because of this, large herds of cattle were being wiped out by the millions. It was seen that almost 95% of all the cattle that had contracted this disease resulted in death, while the other 5% ended up surviving. In this 5% of cattle that ended up surviving this infection, it was recognized that they will have lifelong immunity if outbreaks were to occur in the future.¹¹⁾

Infection in cattle was was examined more closely after their death, and repeatedly, it was seen that the gastrointestinal and respiratory tracts contained a frothy substance throughout the esophagus and lungs.¹²⁾

¹³⁾ Fig. 3. Areas of cattle infected by Rinderpest.

Rinderpest was not a zoonotic disease so humans did not physically get sick from infection of this disease. However, Rinderpest still caused major problems for countries all over the world. For many countries, including South Africa, exportation of livestock was a major source of income.¹⁴⁾ Due to the outbreaks of Rinderpest, countries had begun to put bans on the importation of livestock from these countries with massive amounts of cattle infected. Since the exportation of cattle played such a major role in source of income, the economy was severely effected. Africa in particular, was one country that was denied access to the valuable livestock markets which they depended on.

During earlier years, South Africa had successful Rinderpest vaccinations that were relatively easy to produce, and granted protective immunity to both strains of the virus. However, the production of this vaccination was very expensive, and required a difficult process of refrigeration, or what people often referred to as “cold chain.¹⁵⁾ In 1981, the idea of a thermostable vaccination became a reality. The thermostability of this vaccination, Thermovax was improved by better production and lysophilization techniques, which allowed the vaccination to adapt to the Vero cell line, simplifying production yet again.

A research programme, initiated by Tufts University School of Veterinary Medicine, and the US Department of Agriculture was created, to once again, simplify the rinderpest vaccine so that it met the international required minimum immunizing dose.¹⁶⁾ Through this programme and many modifications that had been made, shelf life was greater than 8 months when contained at 37°C. These advancements allowed this vaccine to be used on site for 30 days without any use of the cold chain.¹⁷⁾ Once this vaccine was accomplished, producing it became a large part of the veterinary service budgets. At this time, veterinarians and para-professionals invested most of their time and career into rinderpest vaccination activities, and found their involvement with campaigns brought a major source of prestige and power to the world.¹⁸⁾

After the development of this vaccine, and the launch of the Rinderpest Eradication Program, many other vaccinations began to be produced for diseases that were caused by infection of the morbilliviruses as well, such as PPR, otherwise known as Peste des petits ruminants. So not only did this vaccination help in regards to Rinderpest, it helped with many other diseases around the world.

Due to the enormous impacts that Rinderpest was having on countries around the world, major efforts to eradicate this virus began in the early 1900's. Before this, individual countries tried to accomplish eradication vaccination campaigns, however these efforts did not work.¹⁹⁾ Finally in 1950, the Inter-African Bureau of Epizootic Diseases formed and created the goal that they would finally eliminate Rinderpest from Africa. This initiated the beginning of surveillance and vaccination use to rid the country of Rinderpest. The first Pan-African rinderpest vaccination campaign, also known as JP 15, occurred from 1962 until 1976 and eliminated the disease.²⁰⁾ Due to these efforts, nearly all of Africa was officially declared Rinderpest free.²¹⁾ At this point, they were not certain the disease was completely eradicated from the entire country due to multiple countries failing to report the last cases of Rinderpest which had been detected. Due to this failure of reporting, a second opinion was needed before the country of Africa could fully declare, without hesitation, it was Rinderpest free.

It wasn't until 2011 when the Food and Agriculture Organization announced confidently that the disease had finally been eradicated in all locations where the disease was last reported and this statement was later confirmed by the World Organization for Animal Health.²²⁾

Morbilliviruses, a group of viruses that causes the outbreak of Rinderpest are extremely fragile. The sensitivity of these viruses allow them to be easily destroyed through lowering or raising pH, exposing them to sunlight, raising the temperature, or putting them in the presence of chemicals, which all cause the destruction of the outer lipid-containing envelope.

Around the world there is the fear that this disease could potentially cause another outbreak, causing our economy to plummet as it did before. The strains of this disease continue to be kept under controlled conditions in labs around the world, however, there is the potential risk for it to get in the hands of the wrong person, or escape due to an accident. For this reason, labs have been either been destroying the strains in an effective and proper manner, or keeping them under extreme supervision, where only the most trusted people are able to access it.²³⁾

Since these viruses also need close contact to a susceptible animal, another way in which future outbreaks could be controlled, if the disease were to accidentally escape from the lab, is through methods of quarantine as well as ensuring the conditions which the animals are kept under is clean.²⁴⁾

Fig. 4. Rinderpest virus under microscope