on february 13 , 1996 , a 7-year - old boy from doihue in administrative region vi was admitted to the hospital clnico fusat of rancagua in the region ( figure 1 ) with a 2-day history of adynamia and dizziness . on admission , , progressive paralysis developed that evolved to respiratory failure ; the boy was connected to a mechanical ventilator . cat scan showed diffuse cerebral edema , and the electroencephalogram indicated no electric activity . intracranial hypertension developed , and the patient map of south america showing the geographic position of chile and map of chile presenting the geographic distribution of the administrative regions of the country . a virus was considered the most probable cause , laboratory tests were conducted to determine the presence of the following viruses : herpes , measles , coxsackie , echo , and polio . interviews with relatives and the boy s nanny revealed that bats had been observed in the family s house . the nanny also reported that she had seen a bat flying away from the child s toy box . even though these interviews failed to reveal any direct contact with bats or any history of an animal bite , this epidemiologic information prompted the physicians to suspect rabies . on february 26 , 1996 , a serum sample and corneal smear were obtained from the patient and sent to the rabies laboratory of the instituto de salud pblica de santiago ( isp ) . a rabies antibody titer of 1:625 was found in the serum specimen by using the indirect fluorescent - antibody ( ifa ) technique ( 14 ) . the patient had no history of rabies vaccination to account for the presence of antibodies . the corneal smear was negative for rabies antigen by the direct fluorescent - antibody ( dfa ) assay ( 15 ) . on march 4 , a second serum sample , the second serum sample was tested simultaneously with the first one by ifa assay , and a titer of 1:15,625 was detected . the saliva sample was negative by dfa assay and suckling mouse inoculation ( 15,16 ) . the patient died on march 5 , 1996 , when artificial respiratory support was disconnected . postmortem tissue samples of cerebral cortex , hippocampus , cerebellum , and nuchal skin biopsy were sent to the isp rabies laboratory for diagnosis . rabies postexposure prophylaxis with the suckling mouse brain fuenzalida - palacios vaccine was administered to the victim s mother and to 10 health - care providers who had possible contact with the patient s saliva . the rabies postexposure prophylaxis schedule used was 2 ml of vaccine , subcutaneously , on each of days 1 , 2 , 3 , 4 , 5 , 6 , 21 , and 90 . blood samples were taken from vaccinees on day 14 after the initial dose of vaccine ; ifa assay showed that adequate immune responses had developed . the virus was isolated from the patient s brain tissue by intracerebral inoculation of suckling mice ( 16 ) . to help identify the possible source of infection , the virus was antigenically and genetically characterized . antigenic characterization of the virus was carried out by using a panel of eight monoclonal antibodies directed against the viral nucleoprotein , provided by the centers for disease control and prevention . these analyses identified a rabies antigenic variant associated with tadarida brasiliensis ( free - tailed bat ) in chile , which had been designated as antigenic variant 4 ( agv4 ) ( 9,17 ) . genetic characterization was done by sequencing a 320-bp portion of the rabies virus nucleoprotein gene from nucleotide position 1,157 to 1,476 , as compared with the sadb 19 strain ( 18,19 ) . briefly , genomic viral rna was extracted from infected tissue by using trizol ( invitrogen , san diego , ca , formerly gibco - brl inc . ) according to the manufacturer s instructions . complementary dna was produced by a reverse transcription polymerase chain reaction with primers 10 g and 304 ( 19 ) and was sequenced by using the taq big dye termination cycle sequencing ready reaction kit ( applied biosystems , foster city , ca ) , according to the manufacturer s protocol , on an applied biosystems 377 dna automated sequencer ( applied biosystems ) . this human rabies virus isolate was compared with viruses obtained from domestic animals and insectivorous bats in urban centers in chile from 1977 to 1998 ( 18 ) . pileup and pretty programs of the wisconsin package , version 10 ( genetic computer group , 2000 , madison , wi ) , were used to produce sequence alignments and comparative nucleotide analyses . the programs dnadist ( kimura - two parameter ) , neighbor ( neighbor - joining method ) , and dnapars ( parsimony method ) from the phylip package , version 3.5 ( 20 ) , were used in the phylogenetic studies . the bootstrap method , as implemented by the seqboot program from phylip , was followed by the use of dnadist and neighbor for the distance matrix analyses . although five genetic variants of rabies virus are found in chile ( 18 ) ( figure 2 , groups a to e ) , a reservoir has been identified for only two : t. brasiliensis ( figure 2 , group d ) and lasiurus sp . phylogenetic analyses of the chilean human isolate demonstrated that it segregated in group d. this group represents the genetic variant of rabies virus most frequently isolated throughout the country , formed by viruses from the metropolitan region and regions iv , v , vi , vii , viii , ix , and x ( figure 1 ) . the high bootstrap value that supports the inclusion of this virus in group d and the very close genetic relationship it has with the other members of this group ( average genetic distance 0.5% ) clearly show that t. brasiliensis is the likely reservoir of the rabies virus isolated in this case . neighbor - joining tree comparing the human rabies isolate with representatives of the rabies genetic variants obtained from insectivorous bats and domestic animals in chile ( 18 ) . bootstrap values obtained from 100 resamplings of the data by using distance matrix ( top ) and parsimony methods ( bottom ) are shown at nodes corresponding to the lineages representing the rabies virus variants ( a , b , c , d , and e ) currently circulating in chile . only bootstrap values duvenhage virus , genbank accession number , european bat lyssavirus , myotis chiloensis , roman numerals indicate the administrative region where the sample was obtained , tadarida brasiliensis , metropolitan region , lasiurus borealis . the absence of a history of an animal bite , the clinical presentation of the disease without the classic signs of hydrophobia or aerophobia , and the absence of any human rabies cases for a period of 24 years in chile were the primary reasons that rabies was not first suspected and a definitive diagnosis was delayed in this case . retrospective studies of human rabies epidemiology have demonstrated that it is not uncommon to observe rabies cases in which there is no history of a bite , mainly in situations involving insectivorous bat rabies variants . for example , of the 17 human rabies cases associated with insectivorous bats reported in the united states from 1980 to 1996 , only one had clear documentation of a bite ( 22 ) . without proper education , patients may not be aware of the risks from a bat bite . moreover , the wound may not be appreciated as a concern because of the limited injury inflicted by the bat 's small teeth ( 23 ) . finally , there may not be an opportunity to obtain a history from a pediatric patient or to discern an exposure that occurs during sleep or other circumstances ( 24 ) . in cases in which a patient shows clinical signs of central nervous system involvement of unknown or suspected viral origin , health - care providers should be aware of the importance of conducting a thorough medical history to appropriately assess the possibility of rabies . with the important changes in the epidemiologic patterns of rabies in latin america , this disease should be included in the differential diagnosis of neurologic diseases characterized by acute encephalitis and progressive paralysis , even when no previous history of an animal bite exists and even in regions where canine rabies has been eradicated .
the first human rabies case in chile since 1972 occurred in march 1996 in a patient without history of known exposure . 
 antigenic and genetic characterization of the rabies isolate indicated that its reservoir was the insectivorous bat tadarida brasiliensis . 
 this is the first human rabies case caused by an insectivorous bat rabies virus variant reported in latin america .