FAMILY ERKONACEAE 



1259 



2. Legio erebea spec. nov. From Latin 

 erebeus, belonging to the Lower World. 



Common names: Choriomeningitis vi- 

 rus, lymphocytic choriomeningitis virus. 



Hosts : MURIDAE — Mns muscrdvs L., 

 graj' or white mouse. HOM I N IDAE — 

 Homo sapiens L. , man . CERCOPITHECI- 

 DAE — Macaca mulatla, rhesus monkey. 

 P^xperimentally, also guinea pig; white 

 rat; dog (masked); ferret (masked); 

 Macaca irus, crab-eating macaque; Syri- 

 an hamster; chick- or mouse-embryo 

 serum-Tyrode solution culture; chick 

 embryo. 



Insusceptible species: Pig, rabbit, 

 field vole, bank vole, canary, hen, para- 

 keet. 



Geographical distribution: France, 

 England, United States. 



Induced disease : In white mouse, more 

 virulent in young than in old individuals ; 

 infection may take place in utero or soon 

 after birth; some mice become carriers 

 after recovery, with virus in organs, 

 blood, urine, and nasal secretions; car- 

 riers are immune to large intracerebral 

 inoculations of virus; expei'imentallj^ 5 

 to 12 days after intracerebral inoculation 

 of susceptible mice, somnolence, photo- 

 phobia, tremors of the legs, tonic spasms 

 of muscles in the hindquarters upon 

 stimulation ; recovery or death. In man, 

 disease may be subclinical at times as 

 shown by the fact that some supposedly 

 normal sera contain specific antibodies; 

 not all clinical cases develop protecting 

 antibodies against testing strains, so that 

 disease may be somewhat commoner than 

 can be ascertained readily ; in all cases 

 benign, but in the more severe of these an 

 acute aseptic meningitis ; after incubation 

 period of !§ to 3 days, spells of fever ex- 

 tending as long as 3 weeks ; late in the 

 disease there may be a meningeal reaction 

 both clinically and cytologically ; lympho- 

 cytes and some large mononuclear cells 

 appear in the meningeal fluids, although 

 symptoms remain benign ; there may 

 be virus in the blood from the beginning 

 of fever to the end of the second week ; the 



spinal fluid is not infective at first but 

 may become so before there is a change in 

 cell count ; urine and saliva remain unin- 

 fect ious. 



Transmission : In white mouse, by con- 

 tact with mice infected when young, not 

 with those infected when old; nasal 

 mucosa considered portal of entry. In 

 wild gray mouse of the same species, Mus 

 muscvlus, by contact but less readily 

 than in white mouse. Experimentally, 

 by mosquito, Aedes aegypti L. (C ULICI- 

 DAE), at 26 to 34° C ; by bedbug, Cimex 

 lectularius {CIMIDAE), but defecation 

 on site of bitten area is essential, bite 

 alone being ineffective. Experimentally, 

 to guinea pig, by application of virus to 

 normal and apparently intact skin; not 

 by contamination of food or litter. 



Serological relationships: Serum of 

 recovered subjects usually neutralizes 

 choriomeningitis virus. Hyperimmune 

 serum is ineffective against pseudo-Iym- 

 phocytic choriomeningitis virus and hy- 

 perimmune serum for that virus is inef- 

 fective in its turn when used with 

 choriomeningitis virus. No cross neu- 

 tralization with St. Louis encephalitis 

 virus. A specific soluble antigen asso- 

 ciated quantitatively with virus in all 

 hosts fixes complement in the presence 

 of immune serum; virus does so poorly 

 if at all; the anti-soluble-substance anti- 

 bodies seem to be independent of virus- 

 neutralizing antibodies. A soluble pro- 

 tein, readily separable from virus, gives 

 a specific precipitin reaction with immune 

 serum ; antibodies concerned are probably 

 not the virus-neutralizing antibodies. 



Immunological relationships : Intra- 

 peritoneal injection of about 160 intra- 

 cerebral lethal doses has been found to 

 protect the white mouse against infection 

 by subsequent intracerebral injection of 

 10,000 lethal doses. The immune mouse 

 differs from the immune guinea pig in 

 showing no neutralizing antibodies in its 

 blood; even the guinea pig may develop 

 resistance before antibodies appear in its 

 serum. Formalized vaccines made from 



