Epidemiology and Phylogenetic Considerations

Table VIII. 11.1 lists the 16 members of the Arenaviridae, their known vertebrate hosts' geographic distribution, date of first finding, and authors) and dates of first description. Four of these are important agents in human disease: LCM, Junin, Machupo, and Lassa. In addition, 10 other members of the group are apparently nonpathogenic (for human beings). Epidemiological information about these is scanty, although several — particularly Tacaribe and Pichinde — have been studied intensively in the laboratory.

Table VIII.11.1. History and natural occurrence of arenaviruses

Virus

First finding

Natural Occurrence Principal host

Geographic distribution

First description

LCM

1933

Mus musculus

America, Europe

Armstrong and

Lillie 1934

Quaranfil

1953

Bubulcus ibis: pigeon Argas ticks

Egypt, S. Africa,

Taylor et al. 1966

Afghanistan, Ni

geria

Tacaribe"

1956

Artibeus literatus

Trinidad, West

Downs et al. 1963

Artibeus jamaicensis

Indies

Junin

1958

Calomys laucha

Argentina

Parodi et al. 1958

Akodon azarae

Amapari

1964

Oryzomys sp.

Brazil (Amazonas)

Pinheiro et al. 1966

Neacomys guianae

Araguari

1964

opossums

Brazil

USPHS 1988

Johnston Atoll

1964

Ornithodorus capensis

Johnston Atoll

Taylor et al. 1966

(Pacific)

Machupo

1965

Calomys callosus

lowland Bolivia

Johnson et al. 1965

Parana

1965

Oryzomys buccinatus

Paraguay

Webb et al. 1970

Tamiami

1965

Sigmodon hispidus

Florida (U.S.A.)

Calisher et al. 1970

Pichinde

1965

Oryzomys albigularis

Colombia

Trapido and

Thomasomys lugens

Sanmartin 1974

Latino

1965

Calomys callosus

Brazil, Bolivia

Webb et al. 1973

Lassa

1969

Praomys natalensis

Nigeria, Liberia

Buckley et al. 1970

Sierra Leone

Flexal

1975

Oryzomys bicolor

Edo. de Para, Brazil

Pinheiro et al. 1977

Mopeia

ca.1976

Praomys natalensis

Southeast Africa

Wulff et al. 1977

Mobala

ca.1982

Praomys jacksoni

Central African

Gonzalez et al. 1983

Republic

Note: Three of these viruses are already named in the International Catalogue of Arboviruses (1975 and 1988 update): Araguari, Quaranfil, and Johnston Atoll are considered possible Arenaviridae, the latter two on basis of electron microscopic studies (Zeller, personal communication, 1989). None of these three viruses has rodent hosts. aThe isolation of Tacaribe from mosquitoes is considered doubtful, and due to a possible laboratory numbering error (Downs et al. 1963).

Note: Three of these viruses are already named in the International Catalogue of Arboviruses (1975 and 1988 update): Araguari, Quaranfil, and Johnston Atoll are considered possible Arenaviridae, the latter two on basis of electron microscopic studies (Zeller, personal communication, 1989). None of these three viruses has rodent hosts. aThe isolation of Tacaribe from mosquitoes is considered doubtful, and due to a possible laboratory numbering error (Downs et al. 1963).

In regard to the Tacaribe group viruses, beginning with LCM, and continuing with other members of the group, a rodent association is usually found. Exceptions are Tacaribe, a virus isolated several times from bats in Trinidad in 1957 (and never reisolated there or elsewhere), and the two recently associated agents, Quaranfil and Johnston Atoll, found in birds and tick ectoparasites of birds (learned from personal communication with wife of H. Zeller in 1989).

A fascinating feature is the geographic-ecological-natural host range of the Arenaviridae. Each rodent species involved with an individual virus has its ecologically determined range, and thus delimits the territory of distribution of the virus. As can be seen in Table VIII. 11.1, the exception to the limited-host-range rule is the house mouse, M. musculus. The genus Mus is an Asiatic and European genus. Mus musculus is well adapted to the human environment and now has worldwide distribution but is found particularly in the temperate regions of America, Europe, and Asia. It moves where humans move, and communication by sea has opened the world to it, although in the tropics it has remained more restricted to coastal or riverine settlements.

Praomys natalensis, the multimammate mouse, is also very common; commensal with humans, it is widely distributed in Africa, and is associated with Lassa virus and Mopeia virus. Praomys jacksoni, another member of the genus, which holds 14 species, is associated with Mobala virus in the Central African Republic. The literature is confusing because Praomys is often referred to as Mastomys. Currently, however, Mastomys, Myomys, and Myomys-cus are all considered to be synonymous with Praomys (Honacki, Kinman, and Koeppl 1982). Praomys is placed in the rodent family Muridae.

The New World rodents associated with arenaviruses are all placed in the family Cricetidae, with several genera involved. It is likely that there have been many opportunities for virus dispersal as well as adaptation of viruses to new rodent hosts, when one considers (1) the number of viruses, such as LCM, Lassa, Junin, Machupo, and others; (2) the diversity of rodents; and (3) the rise (and later enormous development) of intracontinental and intercontinental traffic; and (4) the recently recognized pair of viruses Quaranfil and Johnston Atoll (provisionally placed in the Arenaviridae on the basis of electron microscopic studies), which are associated with birds that disperse widely. Thus it seems evident that the whole world is at risk for species radiation of Arenaviridae.

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