Arenaviruses

What are Arenaviruses?

They are a group of RNA viruses, which belong to the family Arenaviridae. These viruses are usually transmitted from rodents to human beings. The name Arena belongs to the Latin word (arenosos), which means ‘Sandy’ (which describes grainy appearance). They are spherical, enveloped in a lipid membrane, with a diameter of about 110-130nm [1]. In addition, there is a new and highly divergent series of arenaviruses, known as reptarenaviruses, that have been discovered which infect snakes and cause inclusion body disease.

History of Arenavirus

The first Arenavirus, Lymphocytic Choriomeningitis Virus (LCMV), was isolated in 1933 during a study of an epidemic of St. Louis encephalitis. During the study, it was discovered that LCMV was not the cause of the outbreak. By the 1960s, several types of similar viruses had been discovered. They were classified into the new family Arenaviridae. In 1956 another Arenavirus, Tacaribe virus, was found. After that, a new Arenavirus was discovered on average every one to three years. Many other Arenaviruses have been isolated in rodents only, but only a few cause hemorrhagic diseases. The first virus is known to cause VHF was the Junin virus, isolated in 1958. Junin virus is known to cause Argentine hemorrhagic fever in a restricted agricultural area of the pampas in Argentina. Machupo virus was also isolated in 1963 in the remote savannas of Beni province of Bolivia after several years. The next member of the Arenaviridae family to aggravate an outbreak of human illness was the Lassa virus in Nigeria in 1969. The most recent discoveries of these human pathogenic viruses were Guanarito in Venezuela in 1989, Sabia in Brazil in 1993, Chapare in Bolivia in 2004, and Lujo in South Africa in 2008.

Classification

Arenavirus is a virus that belongs to the higher classification family Arenaviridae. Therefore, scientifically it is called Arenavirus, in the rank of Genus and class of Ellioviricates.  Arenavirus is divided into two groups:

• The New World or Tacaribe complex
• The Old World or LCM/Lassa complex

Viruses in these groups cause mild to severe illnesses in humans.

Animal Host

In nature, those viruses are found in animals. In other words, they are zoonotic. Furthermore, each virus is associated with either one species or a few closely related rodents, forming the virus’s natural reservoir. Tacaribe complex viruses are connected or associated with the New World rats (family Muridae, subfamily signodontinae). On the other hand, the LCM/Lassa complex viruses are connected to Old World rats (family Muridae, subfamily Murinae). On the whole, these types of rodents live across a wide proportion of territorial landmass, including Asia, Africa, Europe, and the Americas. A noticeable exception is the Tacaribe virus (found in Trinidad) traced from bats and mosquitoes.

Spread & Transmission of Arenavirus Infections

It has been known that the rodent hosts of Arenavirus species are chronically infected with the virus. Despite this, however, the viruses seem not to cause obvious illness in them. Some types of Arenavirus appear to be passed from mother rodents to their offspring during pregnancy and therefore remain in the rodent population from one generation to another. This hereditary transfer establishes the rodent as an indubitable vector for Arenavirus. Most infections are spread among adult rodents, probably through fighting and inflicting bites. Also observable is that only a number of the rodents in each host species is infected per time, and in most cases, only in a limited portion of the hosts’ geographical range. Viral, environmental pollution is through urine or droppings of the infected hosts. Human infection with Arenavirus is accidental and happens when an individual comes into contact with excretions (urine or feces) or items contaminated with the excretions of an infected rodent. Contact sources may be through ingestion of the virus-contaminated food or direct contact with rodent excrement. Inhalation is another means by which a man is infected. Tiny particles (including dust), soiled with rodent excrement- urine, saliva, or excretes) if inhaled is infectable. The types of incidental contact depend on the habits of both humans and rodents. Some rodent species are found more in the farmland where they feed on the cultivated crops. Some species are dominant in human homes feeding on food remnants, while others live in industrial or administrative buildings and feed on wastes. Consequently, man becomes helpless and is at risk of not avoiding rodents’ operational habitat. Some Arenavirus, such as Lassa, Machupo, and Liyo viruses, are involved with secondary person-to-person and nosocomial (hospital setting) transmission. This may occur when a person infected by exposure to the virus from the rodent host transfer the virus particulars of an infected person. Certain viruses are also transmitted airborne. Additionally, contaminated objects, such as medical equipment office equipment (e.g., laptop systems, stapler, video camera, others) transmit viruses. In those situations, protective clothing and disinfection procedures (generally called barrier nursing) can help prevent the further spread of infection. In conclusion, personal health care methods, obeying regulated health instructions, the need for information and awareness, and a determined effort to adjust lifestyle and habits are the only steps out of the spread of arenavirus infections.

Treatment

No specific medical care is required in case of mild symptoms. In the case of Lassa fever or any other South American Hemorrhagic fever, aggressive medical care is required to decrease the mortality rate. An antiviral drug called Ribavirin is used to treat Lassa fever and South American hemorrhagic fever. Convalescent human plasma is used in the treatment of Junin virus infection. According to the type of virus, the best bet to know about treatment plans will be consulting with your doctor.

Morbidity and Mortality Rate

Arenavirus species may be identified by their unique surface glycoprotein and infectivity neutralization. Case fatality rates range from 5 to 20% for hospitalized cases. The risk of humans getting affected by Arenavirus is mainly dependent on age, gender, race, only to the degree that these variables impact contact with rodent urine, feces, saliva, or infected rodent hosts. Clinical symptoms of infection by another arenavirus in South America are similar to those described for Lassa. Although the available epidermis logical data is very limited, case-fatality rates may be higher up to 30% for the Guanarito virus. The mortality rate of the Lassa virus is found to be 80% in pregnant females, especially in their third trimester, where the chances of fetal death are more. However, the overall mortality rate is 1% [2]. 

Symptoms

SYMPTOMS

The early symptoms of arenaviruses follow common symptoms, which include:

• Headaches
• Fever
• Fatigue
• Hot teary eyes, etc.

Other symptoms will follow the specific type of virus.

FAQ

• What is Lassa fever?

Lassa fever is an animal-borne [or zootomic] acute viral illness. It is endemic in West Africa, including Sierra Leone, Liberia, Guinea, and Nigeria. However, neighboring countries are also at risk, as the animal vector for the Lassa virus, the “multimammate rat” (Mastomys natalensis} is distributed throughout the region.

• What is LMC disease?

Lymphocytic choriomeningitis virus, or LCM, is a rodent-borne viral infectious disease caused by Lymphocytic choriomeningitis virus (LCMV), a member of the family Arenaviridae, that was initially isolated in 1933. The primary host is the common house mouse, Mus musculus. 

 

References:

1. Britannica
2. medscape
3. Vanzee BE, Douglas RG, Betts RF, et al. Lymphocytic choriomeningitis in university hospital personnel. Clinical features. Am J Med. 1975 Jun. 58(6):803-9. [Medline].CDC. Lymphocytic Choriomeningitis (LCM). Centers for Disease Control and Prevention. https://www.cdc.gov/vhf/lcm/index.html. 6 May 2014; Accessed: 11 May 2019.
4. Holmes GP, McCormick JB, Trock SC. Lassa fever in the United States. Investigation of a case and new guidelines for management. N Engl J Med. 1990 Oct 18. 323(16):1120-3. [Medline].CDC. Viral Hemorrhagic Fevers. Centers for DiseasControlandPrevention.  https://www.cdc.gov/vhf/index.html. 29 Jan 2014; Accessed: 11 May 2019.