Yellow Fever, An Emerging Issue!!!

By Maria Kausar

Nowadays, there is an increase, observed in infectious diseases which leads towards a rise in morbidity and mortality both in animal as well as in human population.

One of the main reasons for these infectious diseases is day by day changing climate across the different regions on Earth. This climatic change is resulting in the expansion of vector population due to extreme weather conditions and indirectly a rise in vector-borne diseases. Along with climatic conditions, there are certainly other factors involved in causing infectious diseases. Mosquitoes are very famous as biting pests and they are acting as a source of transmission of many fatal diseases like Malaria, Dengue, West Nile Fever, Lymphatic filariasis, Rift Valley Fever, Yellow Fever, Zika Virus, and Chikungunya. Mosquito bites are very aggravating and cause inflammation at the biting site. Mosquito-borne diseases are offering a great threat globally and these are devastating, causing both economic as well as social losses. No doubt, mosquito-borne diseases are being controlled up to a large extent, but these are still flourishing and causing remarkable morbidity along with mortality in adolescents and children. Transmission of arboviral infections depends upon the level of infectivity of mosquito hosts and the behavior of blood-feeding in mosquitoes.        

The mosquito-borne viral disease, yellow fever, is the sickness triggered by a potentially deadly virus known as yellow fever virus (YFV) and roots disease in humans and monkeys. We termed it yellow fever due to the occurring of jaundice, which is the yellowing of eyes and skin. It is endemic to tropical and subtropical zones of Africa and South America. It spreads through the mosquito bite and causes high fever and jaundice in the affected organism.

Its main symptoms are fever and jaundice. It is transmitted by the biting of the Aedes or Haemagogus species of mosquito. Up till now, there is no medicine to cure or treat this infection. Prevention measures must be taken to prevent oneself from this lethal disease. Mosquito repellent, wearing long shirts and long pants are some precautionary measurements to control this disease. 99% immunity from yellow fever can be obtained by the use of a vaccine against it.

Yellow fever virus is an arthropod-borne virus that belongs to the family Flaviviridae. It is an enveloped RNA virus, having enveloped protein that is used for the viral attachment with the specific receptors on the cells of the host. The viral tegument is also present inside the envelope, which helps the virus to evade the immune system of the organism and to replicate the viral genome. Viral tegument activates the interferon and inhibits the signaling of the immune system. This virus has similarities to the West Nile virus and Japanese encephalitis virus. It is also known as an African mosquito-borne infection.

Yellow fever is a hemorrhagic fever of viral origin that is most common in South American countries, Africa, and the Sub Sahara region of the world. In Africa, each year, 30,000 people die from it. It is rarely present in U.S. travelers. In Pakistan, not a single case of yellow fever is reported up till now. It is transmitted to people through the nibble of an infected mosquito specifically Aedes. These mosquitoes get the virus by nourishing on infected monkeys and then transmit this disease to other primates. But it is not a contagious disease.

This virus completes its life cycle in one host (primates). A Mosquito only causes its transmission. On biting of the mosquito, this virus enters the bloodstream of the organisms and enters the macrophages. On entering the macrophages and other cells of the body, this virus makes its proteins by using host machinery and its RNA. The virus also evades from the immune system of the organisms by inhibiting the signals of the immune system as there is no antigen presentation. The virus enters the other organs via the bloodstream and destroys that organ. It causes dysfunction of the liver that is the main cause of jaundice. In the heart, it causes myofiber degeneration and thus causes bradycardia. Cytokine storm is also another main reason for the dysfunction of the organs. By the multiple organ dysfunction, this disease causes loss of organ function and loss of homeostasis causing the death of the person.

Some common signs and symptoms of yellow fever include temperature, body pain, liver infection or jaundice, muscle ache, bleeding (from mouth, nose, and stomach), nausea, vomiting, fatigue, and chills. This disease has two phases. 1st phase occurs for 3 to 4 days and the virus incubation period completes in this phase. This is also known as the acute phase. If immunity of an affected organism is activated, it causes improvement in the patient’s health and symptoms may disappear. If this phase becomes severe it causes headache, fever, vomiting, and loss of appetite-like symptoms. If this phase is not controlled, the patient enters the toxic or 2nd phase. This phase causes bleeding (from mouth, nose, eyes, or stomach), fever, jaundice, renal function deterioration, and abdominal pain.

In laboratory testing, diagnosis of yellow fever is done through the detection of the virus antibodies in the serum of the affected organism. Mainly IgM antibody test and neutralizing antibodies test are used. The presence of the virus in the blood sample of the affected organism is also seen.

There isn’t any specific drug available for the cure of yellow fever, however, treatment based on the symptoms including rest, use of analgesics, antipyretics, and fluid therapy is found effective. People with severe symptoms should be hospitalized. However, the vaccine is available in the market for the development of immunity.

Prevention is better than cure and in the case of yellow fever, the main control strategy is the control of mosquito population through minimizing the breeding sites for the mosquito vectors. As vector control strategy is the main and most effective tool to prevent any vector-borne disease. To control mosquito-borne diseases, the mosquito is the main target body to control, and it can be achieved by the use of insecticides and integrated larval management. But due to the development of resistance against insecticides and behavioral modification, we must go for alternative methods to control mosquitoes. Use mosquito repellent, wear full shirts and pants to avoid mosquito bites. The use of mosquito coils is also found effective. Travelers should take vaccine shots, must wear full clothing, and use repellents. Use a window or screen door to keep mosquitoes away. Do away with the breeding or egg-laying sites of the mosquitoes through the evacuation of stagnant water from drums, flowerpots, and containers. Keep emptying the water in pet cups and exchange the water in the birdbath on daily basis. Drilling of holes in tire tubes to drain the water from there.

REFERENCES:

1. cdc.gov – healthcare providers.
2. healthline.com-health-yellowfever Medically reviewed by Joseph Vinetz MD — written by Colleen M. story — updated on February 26,2021
3. https://en.wikipedia.org/wiki/Yellow_fever
4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4349381/
5. https://jvat.biomedcentral.com/articles/10.1186/s40409-018-0162-y
6. https://www.who.int/news-room/fact-sheets/detail/vector-borne-diseases

Authors

1. Maria Kausar, M.Phil. Parasitology from University of Agriculture Faisalabad
2. Dr. Muhammad Sohail Sajid, Chairman Dept. of Parasitology at University of Agriculture Faisalabad
3. Arslan Nazim, DVM from University of Veterinary and Animal Sciences Lahore
4. Rana M. Athar Ali, M.Phil. from University of Agriculture Faisalabad