Introduction:
Orthonairovirus is a genus belonging to the family Nairoviridae of the order Bunyavirales. This group includes viruses having circular, single-stranded RNA and negative senses. The name of the virus originated from the Nairobi sheep disease, which affects the gastrointestinal tracts of sheep and goats. Most of the viruses in this genus are tick-borne and have hosts like humans or other vertebrates.
How Is It Transmitted?
This virus affects many vertebrate organisms. The transmission happens through ticks. Members of the genus Nairovirus are present worldwide, especially in those places where arthropod vectors and vertebrate hosts occur together.
How Did It Evolve?
Phylogenetic analysis has revealed that these viruses fall into the two major monophyletic groups: the complex (Ixodidae) and soft (Argasidae) tick-vectored groups. Fossil and phylogenetic data analyses mention the evolution of the complex tick-soft tick divergence between 120 million years ago and 92 million years ago. This Dindicates that the Nairo Viruses were related to these ticks for over 100 million years. Also, nairoviruses that are vectored by ticks of the genera Argas, Carios, and Ornithodoros create three separate monophyletic lineages. This is also supportive of host-virus cospeciation.
The hard-bodied tick serogroups have been mentioned below:
-
Crimean-Congo hemorrhagic fever.
-
Tamdy.
-
Nairobi sheep disease.
-
Sakhalin.
The soft-bodied tick serogroups are as follows:
-
Hughes.
-
Qalyub.
-
Dera Ghazi Khan.
The tick vectors for the serogroups Kasokeo and Thiafora are currently unidentified.
What Is Clinical Importance?
Studies have shown only four viruses of this genus to be pathogenic for a human who is as follows:
-
Crimean-Congo hemorrhagic fever virus.
-
Dugbe virus.
-
Kasokeo virus.
-
Nairobi sheep disease virus.
Erve virus, a fifth virus, has been recently added as a pathogenic virus for humans.
Crimean-Congo Hemorrhagic Fever (CCHF)
The causative organism for Crimean-Congo hemorrhagic fever (CCHF) is the infection due to a tick-borne virus called Nairovirus belonging to the family Bunyaviridae. The disease was first discovered in Crimea in 1944; hence, it was named Crimean hemorrhagic fever. Later, it was recognized as the cause of illness in the Congo in 1969. Thus the current name of the disease was mentioned.
This fever is commonly observed in Eastern Europe, especially in the former Soviet Union, throughout the Mediterranean, Central Asia, northwestern China, southern Europe, Africa, the Middle East, and India. The mode of transmission is through a vector. Ixodid (a hard tick) is considered a reservoir and a vector for CCHF virus.
The signs and symptoms of this fever have been mentioned below:
1. Sudden onset of fever.
2. Initially, the affected person has a headache and increased fever.
3. Back pain.
4. Joint pain.
5. Vomiting.
6. Pain in the stomach.
The people who are at risk of developing this fever are animal herders (who controls a group of animals) and slaughterhouse livestock workers. The physician does the diagnosis after assessing the initial history, signs, and symptoms followed by physical examination. Laboratory tests may help in confirming the diagnosis. The tests are antigen-capture, enzyme-linked immunosorbent assay (ELISA). This fever is primarily treated with supportive therapy. This infection can be prevented by using insect repellent on exposed skin and clothing by agricultural workers and those who work with animals.
Nairobi Sheep Disease
Nairobi sheep disease is a severe viral disease that is tick-borne and is witnessed in Africa. It causes peracute deaths and acute illness, along with severe hemorrhagic gastroenteritis. The Ganjam virus, observed in Asia, has been added as a variant of the same virus. There is no specific treatment available for this disease. Also, fatality rates are high.
The incubation period of the virus usually ranges from 2 to 6 days. The initial symptom is fever which steeply raises the body temperature (41°–42°C [105.8°–107.6°F]) and remains for 1 to 7 days. A decrease in white blood cells and viremia usually occur in the febrile phase. Along with fever, the individual may also experience depression, anorexia, and discharge from the nose, which can be mucus, pus, or blood. Some occasionally occurring signs include conjunctivitis and fetid dysentery, which leads to painful straining. Diarrhea is usually experienced 1 to 3 days after the onset of fever and worsens with the progression of the condition.
Pregnant animals frequently undergo abortions. Death can occur 2 to 7 days after the initial clinical signs appear. However, some affected animals can survive up to 11 days. Dehydration and debilitation due to diarrhea are the leading causes of death in the later stages of the illness. Animals showing severe clinical signs and symptoms have a poor prognosis.
The mortality rate in the field in Africa is almost 70 % to 90 % for the indigenous breeds of sheep, whereas exotic and cross-breeds account for 30 %. It is the opposite in the case of the Ganjam virus. It causes increased mortality in exotic than indigenous Indian breeds. Goats show similar clinical signs and symptoms as that sheep, but the intensity is less severe. However, the mortality rate is almost 80 %.
Colostral immunity plays a significant role in defending this disease in lambs and kids by safeguarding them from exposure in their early life. Also, it helps develop active immunity, which enables survival in tick-infested regions.
Dugbe Virus
Dugbe virus most commonly occurs in parts of Africa. It can replicate in blood-fed A. americanum females, as mentioned by Linthicum et al. in 1989.
Kasokero Ortho Nairovirus
Kasokero orthonairovirus is a viral species in the genus Orthonairovirus. The fruit bat, called Rousettus aegyptiacus, is its only known host. This virus was first collected from Kasokero Cave in Uganda and, thus, named after that.
Conclusion:
Orthonairovirus is capable of causing viral infection in humans as well as animals. Early diagnosis and prompt management can help in managing this condition. You can consult a specialist online through online medical platforms to know more about this condition.
