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New World Arenavirus

New World arenaviruses appear to be less transmissible between humans than their Old World counterparts, although human-to-human transmission of Machupo virus has been reported in both community and nosocomial settings.

From: Manson's Tropical Infectious Diseases (Twenty-third Edition), 2014

Related terms:

Nested Gene

Cladistics

Arenaviridae

Old World Arenavirus

Junin Virus

Tacaribe Virus

Lassa Virus

Lymphocytic Choriomeningitis Virus

Rodent

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Lassa, Junin, Machupo and Guanarito Viruses

J.B. McCormick, in Encyclopedia of Virology (Third Edition), 2008

Host Range and Virus Propagation

All of the New World arenaviruses have rodent reservoir hosts with the exception of Tacaribe virus, which was isolated from bats in Trinidad (Table 1). A hallmark of the arenaviruses is their intimate biological relationship with rodents, resulting in lifetime infection and chronic virus excretion. Many arenaviruses have more than one rodent host, although usually a single species will predominate as the reservoir in nature.

The hosts of LCM virus (LCMV) have included Mus species and hamsters. Guinea pigs are also capable of transmitting the virus in laboratory settings. Machupo virus often renders its major natural host, Calomys callosus, essentially sterile by causing the young to die in utero. Machupo virus also induces a hemolytic anemia in its rodent host, with significant splenomegaly, often an important identifier of infected rodents in the field. The major rodent hosts for Junin virus are Calomys species. Transmission of Junin virus from rodent to rodent is generally horizontal, and not vertical, and is believed to occur through contaminated saliva and urine. The Calomys rodents are affected by the virus, with up to 50% fatality among infected suckling animals, and stunted growth in many others. Both Junin and Machupo viruses induce a humoral immune response when transmitted to their suckling natural rodent hosts, which may have neutralizing antibody in the face of persistent infection. Guanarito virus has been isolated from Zygodontomys brevicauda, though its detailed biology remains to be learned.

The only known reservoir of Lassa virus in West Africa is Mastomys natalensis, one of the most commonly occurring rodents in Africa. At least two species of Mastomys (diploid types with 32 and 38 chromosomes) inhabit West Africa, and both have been found to harbor the virus. All species are equally susceptible to silent persistent infection, as seen when LCMV infects mice. This presumably occurs as in LCM infection, from a selective deletion of the thymic T cell response to the virus. All of the arenaviruses pathogenic for humans will also infect and produce illness in a wide range of primates. However, it is not known whether such infections occur in nature, as is known for Ebola virus for example. In addition, human infection plays no biological role in the life cycle and ecology of the arenaviruses.

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Viral Haemorrhagic Fevers

Lucille Blumberg, ... Daniel G. Bausch, in Manson's Tropical Infectious Diseases (Twenty-third Edition), 2014

Epidemiology

Like Old World arenaviruses, New World arenaviruses are maintained in rodents and spread to humans via exposure to rodent excreta.1,59 The reservoirs of Junin and Guanarito viruses are generally found in rural areas, often in agricultural lands. Consequently, the highest risk of Argentine and Venezuelan HFs is among agricultural workers. Incidence may vary considerably with variations in rodent population densities that may relate to both climatic changes and human-induced habitat perturbation. Although cases can be seen throughout the year, incidence is usually highest at times of peak agricultural activity: March–June in Argentina and November–January in Venezuela. The reservoir for Machupo virus is primarily a household pest. Although Bolivian HF may be seen throughout the year, incidence is usually increased during the dry season (June–August), sometimes with family and community clusters. The reservoirs for Sabiá and Chapare viruses are unknown, but are presumed to be rodents.

New World arenaviruses appear to be less transmissible between humans than their Old World counterparts, although human-to-human transmission of Machupo virus has been reported in both community and nosocomial settings. Only one family cluster of Argentine HF is described, with the index case presenting with atypical skin lesions that may have facilitated transmission.

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Arenavirus Infections

Delia A. Enría, ... C.J. Peters, in Tropical Infectious Diseases (Third Edition), 2011

Lassa Fever and Lymphocytic Choriomeningitis

In contrast to the pattern with the New World arenaviruses, LCM and Lassa viruses are thought to be maintained by vertical transmission within reservoir populations. All pups born to chronically infected females are themselves chronically infected