The Rift Valley Fever is mainly a viral zoonosis, which means that it primarily targets animals. Domesticated animals are the ones that suffer in most cases, such as sheep, cattle, buffalo, camels, and goats. The livestock can get sick through the bites of mosquitos, which carry the RVF virus, belonging to the Phlebovirus type.
History / Origin
The first time the Rift Valley Fever virus was isolated was back in 1931, although the disease was already manifesting among livestock in Rift Valley, Kenya, since the beginning of the 1900s. This particular virus affects mainly animals, although it can also be transmitted to humans. However, there are no human-to-human infections recorded so far. The most severe outbreak of Rift Valley fever occurred between 1950 and 1951, when more than 100,000 sheep died because of this virus, in Kenya. It is worth noting that the outbreaks of this virus occurred in Africa and Arabia only, so it does not pose a danger to the rest of the globe.
What is the Rift Valley Fever?
Researchers believe that bats may be the reservoirs for this particular virus, as it was isolated in two different species of bats, Peter’s epauletted fruit bat and aba roundleaf bat, which may have transmitted the virus to mosquitos. Thus, outbreaks happen most often after periods of heavy rain, when mosquitos thrive due to high humidity and the existence of numerous water puddles. Even if animals get the virus in the majority of the cases, humans can also get sick. If they have been bitten by an infected mosquito. If they are around sick butchered animals and get in contact with their infected blood. Or, if they drink raw milk coming from a sick animal, then there are extremely high chances for a human to suffer from the Rift Valley Fever.
Certain professions that may be exposed to coming in contact with the raw flesh of animals or bitten by the mosquitos that attack animals, are veterinarians, farmers, herders, and butchers, living and working in Africa and Arabia.
Owners of livestock can protect themselves by vaccinating their animals against this disease. This is a preventative method that will keep outbreaks at bay or diminish the consequences of an outbreak once it occurs. Also, when an outbreak occurs in an area, it would be wise for the animal owners to stop moving their livestock around. It decreases the chances for them to get bitten by mosquitos and, therefore, contacting the virus.
It is worth mentioning that people can get sick in certain cases, like if they have a wound on their skin, even if it is just a small cut, and come in contact with infected blood, or if aerosols are created during the slaughtering of infected animals, which can be inhaled, introducing the virus into the system.
The symptoms caused by the Rift Valley Fever can range from mild symptoms to severe symptoms. The mild symptoms usually occur after a period of incubation, which lasts for 2 to 6 days. Still, there are cases in which the infection with the RVF virus produces no symptoms. In case symptoms do occur, they are similar to those triggered by the common cold. An infected period will experience fever, muscles and joint pain, and headaches, these being among the most frequently met symptoms. But, nausea, vomiting, loss of appetite, sensitivity to light, and even neck stiffness can be experienced as well.
As you probably noticed, these symptoms are similar to the ones produced by meningitis, so a person infected with the RVF virus can be misdiagnosed in the early stages of the infection. These symptoms will last for 4 to 7 days until the immune system will create the right type of antibodies and destroy the virus from the body’s bloodstream.
There are also cases, even if in a small percentage only, which develop severe symptoms in case of infection with RVF. Most of the patients that develop a severe form of the illness will have ocular diseases, while the rest, the fewest, will develop meningoencephalitis and hemorrhagic fever. In the case of patients with ocular diseases, retinal lesions will appear after 1 week once the first symptom of Rift Valley Fever manifested. Approximately 50% of these patients risk losing their eyesight. In the case of meningoencephalitis, the illness will evolve anywhere between 1 to 4 weeks after the first symptoms of the Rift Valley Fever appear.
The symptoms are headaches, hallucinations, loss of memory, vertigo, disorientation, confusion, lethargy, convulsions, and coma. Still, in spite of these severe symptoms, death in the case of these patients is a low occurrence. But, they may experience residual neurological deficit that may affect the quality of their life. The hemorrhagic fever is the severe form that gets installed in the shortest period, appearing within 2 to 4 days after the RVF illness started. In this case, the liver will be the one that will be after the first, so patients will experience jaundice.
Other symptoms are vomiting blood, the appearance of blood in stools, bleeding from the nose or gums, and the appearance of the purpuric rash, which means the bleeding occurs in the skin. Approximately 50% of patients lose their lives in this case, usually within 3 to 6 days since the first symptoms appear.
Can the Rift Valley Fever become a major risk for public health?
Having in mind the previously mentioned forms, of which some are very severe, RVF can definitely be considered a major risk to public health. Outbreaks occur periodically, the last one taking place in 2016, in the Tahua region, when 28 people lost their lives because of the Rift Valley Fever. Campaigns of vaccination of the animals in the exposed areas were conducted on several occasions, to encourage livestock owners to stay safe by boosting the immune system of their animals against this virus. There is also an RVF vaccine for humans, although it is not widely available, unfortunately, so vaccinating livestock is more accessible and efficient.