Experimental rabies in skunks: mechanisms of infection of the salivary glands

Striped skunks (Mephitis mephitis) were inoculated into the right submandibular salivary gland with street rabies virus. They were killed at various times after inoculation and several tissues were examined by immunofluorescence and light microscopy. Right and left superior cervical, nodose and trigeminal ganglia, medulla oblongata and at least three regions of right and left submandibular salivary glands were examined by the fluorescent antibody technique. Intracerebral titrations of salivary gland suspensions were made in weanling white Swiss mice. Immunofluorescent material (inoculum) was detected in septa and connective tissue surrounding secretory units of the right submandibular gland immediately after inoculation, but otherwise antigen was not detected in either right or left submandibular glands without coincident antigen in the medulla oblongata. This occurred first on day 12 in areas of the gland remote from the inoculation site. Titers of virus were low at this time. Serum neutralizing antibodies occurred by day 7 in a few skunks. The time of development and distribution of antigen strongly suggest that, even after direct inoculation, neural networks are necessary for development of widespread infection of the salivary gland. The early occurrence of serum neutralizing antibodies in some of the skunks suggests that the immune response was activated by virus in the inoculum since immunofluorescence was not detected in any tissue at this time.

Rabies virus in the tonsils of a carrier dog

A female dog, inoculated with a rabies isolate from the saliva of an apparently healthy Ethiopian dog, developed rabies but later recovered without supportive treatment. Rabies virus was isolated from the saliva collected 42, 169 and 305 days after recovery. Sixteen months after it recovered, the dog suddenly died after giving birth to two stillborn puppies. At necropsy, viral antigen could be detected in the tonsils and the brain tissue, but viable virus was isolated from the Palatine tonsils only.

[Biological variants of a population of strains of the rabies street virus]

Experiments in mice weighing 6-7 g showed that a population of wild street rabies virus strains could contain from 1 to 3 biologic variants determining the clinical characteristics, duration of the incubation period and of the disease, and virus titres in the brain. Fox strains L-1 and L-2 produced only paralytic rabies, the BE strain isolated from a badger induced paralytic and chronic disease, and the population of the Yak strain isolated from a boy bitten by a fox and timely given a complete course of postexposure treatment contained 3 biologic variants: (1) VAR produced acute paralytic rabies throughout 59 passages, (2) VVR induced a disease of the type of "violent" rabies throughout 20 passages, and (3) VCR provoked chronic rabies in 27 passages.

The dissemination of rabies virus into cranial nerves and other tissues of experimentally infected goats and dogs and naturally infected skunks

Immunofluorescence examination for rabies virus antigen performed on skin specimens acquired from experimentally inoculated rabid goats and some dogs, often show little or not fluorescence. This observation is contrary to results obtained by comparable examination of the skin of naturally infected animals and most experimentally infected dogs. In an effort to elucidate some factors associated with this experience, an experiment was performed to similarly examine the cranial nerves to see if the limited amounts of fluorescing antigen observed in the skin were also found there. Direct immunofluorescence examination for rabies virus antigen was therefore performed on cranial nerves, face, skin and other tissues excised from experimentally inoculated goats and dogs, and naturally infected skunks. We observed that the cranial nerves of those animals with limited fluorescence in nerves of the skin also contained only limited amounts of rabies virus antigen, while both the cranial and peripheral nerves of naturally infected skunks had large amounts of antigen. All the cranial nerves checked in the experimentally inoculated animals had virus antigen at points close to the brain. Limited fluorescence in the peripheral nerves of rabid animals has been associated with the short incubation period often experienced with experimentally inoculated animals, with the exception of the goat. The incubation period, in turn, is related to the degree of susceptibility of the new host, the quantity of virus, the route of infection, and the degree of adaptation of the virus to the new host.

Pathogenesis of rabies in dogs inoculated with an Ethiopian rabies virus strain. Immunofluorescence, histologic and ultrastructural studies of the central nervous system

Dogs were inoculated with either an Ethiopian of Mexican rabies virus strain. The distribution of viral antigen and lesions were studied by immunofluorescence, histologic and electron microscopic techniques. In all dogs inoculated with the Ethiopian rabies virus strain, tremendous whorls of filamentous fluorescing aggregates were observed throughout the brain; these were not observed in dogs inoculated with the Mexican virus. Lesions consisted on neuronal degeneration and neuronophagia, associated with large inclusion bodies and widespread inflammation in dogs inoculated with the Ethiopian isolate. All observed portions of the brain and spinal cord were affected. In general, lesions were much less severe with Mexican isolate. Occasional astrocytes were observed to have inclusions in dogs inoculated both with Ethiopian and Mexican strains. Most neurons examined electronmicroscopically showed signs of infection, varying from a small granular or finely fibrillar viral matrix to numerous matrices accompanied by prolific numbers of virus particles occupying much of the perikaryon. These were found in all dogs inoculated with the Ethiopian strain but were rare with the Mexican isolate. Viral budding occurred from membranes of the rough endoplasmic reticulum, outer lamella of the nuclear envelope, and rarely from the plasma membrane.

Excretion of rabies virus in the saliva of dogs

Thirty-nine dogs were injected intramuscularly with either an Ethiopian strain or a Mexican strain of rabies virus. The excretion of rabies virus in the saliva was studied before and during illness. Nine of 17 dogs that died after injection with the Ethiopian strain had virus in the submaxillary glands. Four of these dogs excreted virus in the saliva up to 13 days before signs of disease were observed. Sixteen of 22 dogs that died after injection with the Mexican strain had virus in the submaxillary glands. Eight of these dogs also excreted virus in the saliva up to seven days before signs of disease were observed. These findings indicate that rabid dogs may excrete virus in their saliva much earlier than previously reported.

Rabies virus pathogenicity and challenge. Influence of the method of preparation, the route of inoculation, and the species. Comparison of the characteristics of the modified, fixed and wild strains

The challenge we carried out, which regularly brought about the death of the control animals, led us to study the different factors influencing the pathogenicity of the rabies virus. So, the method of preparation is important. The strain NYC, prepared from the salivary glands is extremely pathogenic for dogs; however, when it is prepared from mouse brains after nine passages have been made, it proves to be already partially modified. One then notices a death-rate which is less severe, even when larger quantities of virus are employed, and also the presence of some aberrant phenomena. (The survival of some of the infected animals and the nature of their inapparent forms of infection were confirmed by serology.) The significance of the route of inoculation in the different species of animals was studied. The injection in the crotaphytes was reserved for dogs, the cervical muscles for cats and the masseters for sheep. Paradoxically, cats prove to be most resistant to the challenge under our conditions. Finally the numerical data, allowing us to compare the different strains, modified, fixed or wild, was established. The data was based on the incubation period and on the differences between the titres obtained via intramuscular routes and intracerebral routes in the mice.

[Progression of the rabies virus in the visual system of the rat]

The CVS rabies virus, inoculated in the anterior chamber of the eye, is transported from the retina to the central nervous system only along the accessory optic tract and invades transsynaptically its terminal nuclei. On the other hand the retino-geniculo-cortical system is affected much later. Thus the virus shows a special affinity for a well defined neuronal system and behaves as a precise tracer of its intracerebral connections.

[Molecular and cellular aspects of the pathogenesis of rabies]

The true causes of the beginning of the symptoms and the eventual mortality of rabies are not very well known. Immunopathological factors certainly intervene, but they only complete a process of neuronal alteration. Contrary to other viruses which lyse the infected cells, the rabies virus does not necessarily destroy the neurones which are the preferential target cells. On the contrary, RNA synthesis is stimulated during CNS infection by the rabies virus. Synthesis is not stimulated by the multiplication of the rabies virus in the cell lines of fibroblastic or neuronal origin, which suggests the existence of regulations on neuronal level functions in the CNS. Nevertheless, the protein virus synthesis seemed equally submitted to specific neuron regulations or neuronal populations. The traces of a neuronal dysfunction during infection by the rabies virus have been investigated, using as a probe, variations of muscarinic acetyl choline receptors in the CNS. The presence of these receptors is revealed by the use of an antagonistic ligand of acetyl choline, quinuclidinyl benzylate. We were able to show that as regards the rat, the appearance of the first signs of paralysis is correlated with the diminution of the receptor binding. Thus, it seems that the presence of the virus in the CNS provokes neuronal alteration which can in itself condition the viral multiplication and eventually modulate the viral pathogenesis expression.

[Radio-tracking of rabid foxes]

Three wild foxes were trapped, inoculated with rabid fox salivary glands virus and radio-tracked straightaway for about three weeks until the death of the animal. Comparison of movements between incubation and clinical period indicate principally no obvious alteration of the activity area; an important increase in movement, especially during the day-time and lastly some variable changes in the activity pattern according to the individual. A common characteristic was a long period of immobility, before death, near the border of the usual activity area. In connection with these remarks, many sub-cutaneous lesions were observed from bites on the body of one of these three foxes, after necropsy. Epidemiological consequences of these first results were argued, especially as far as transmission of rabies from one fox to another is concerned.

Entry of rabies virus into the peripheral nerves of mice

Young adult mice were inoculated in the hind limb with rabies virus or Sindbis virus. Rabies 1820B virus antigen was detected in leg sections by immuno-fluorescence at 1 h post-inoculation at sites comparable in form and distribution to cholinesterase-positive sites, which represent motor end-plates (MEPs). Sites which were rabies virus antigen-positive by immunofluorescence were also cholinesterase- positive on double-stained slides. Rabies CVS virus detected by autoradiography was similarly distributed at 6 h post-inoculation. Uptake of rabies virus at motor nerve endings was confirmed by the detection of rabies antigen by immunofluorescence in ventral horn cells in the spinal cord at 20 h post-inoculation before involvement of dorsal root ganglia. Rabies virus antigen could not be detected at MEPs if the virus had been inactivated by beta propiolactone or mixed with antibody prior to injection or if the sciatic nerve had been cut 7 days earlier, similarly treated groups of mice survived for the observation period of 6 weeks. Rabies virus antigen was found at MEPs in mice given antibody 24 h before virus injection, but virus antigen was not found in the spinal cord, and mice similarly treated survived. Sindbis virus strain Ar86, which like rabies virus is neurotropic in adult mice, was also found at MEPs and in peripheral nerves by autoradiography at 6 h post-inoculation. In contrast to results with rabies virus-infected mice, stimulation of the sciatic nerve for the first hour post-inoculation prevented mortality. Sindbis virus strain Ar339, which is not neurotropic in adult mice, could not be detected at MEP's by immunofluorescence or autoradiography and mice injected with virus survived. The results presented here suggest that rabies virus and perhaps other neurotropic viruses can use the motor axon terminal at the neuromuscular junction as a site of entry into the nervous system.

Experimental rabies in skunks: persistence of virus in denervated muscle at the inoculation site

Striped skunks (Mephitis mephitis) were inoculated into the denervated abductor digiti quinti muscle with street rabies virus. They were killed at various times after inoculation and several tissues were examined by immunofluorescence and light microscopy. Muscle at the inoculation site was examined electron microscopically. Rabies antigen was detected in muscle fibers first on day 7 and persisted until day 28. Light and electron microscopic lesions at the inoculation site included atrophic and degenerating muscle fibers and a few focal and regional endomysial accumulations of macrophages, lymphocytes and plasma cells. Scattered myocytes contained bodies of matrix, virions and anomalous tubular structures on electron microscopic examination. The results indicate that replication of rabies virus may occur in infected muscle fibers at the inoculation site until 28 days after exposure. This could contribute to variations in the incubation period for the first two to three months after exposure. However, the results do not support the contention that virus is contained in striated muscle cells throughout the long incubation periods.

Intermittent excretion of rabies virus in the saliva of a dog two and six months after it had recovered from experimental rabies

A dog inoculated with a rabies virus isolate from the saliva of an apparently healthy Ethiopian dog was followed for more than 9 months. Saliva and blood specimens were collected three times weekly and cerebrospinal fluid weekly. Saliva samples collected on days 42 and 169 after the dog's recovery produced fatal rabies infections in mice inoculated intracerebrally.

Rabies virus titer from tissues of naturally infected skunks (Mephitis mephitis)

Rabies virus was titrated from the hippocampus and salivary glands (mandibular, parotid, and sublingual) of 19 naturally infected skunks. Selection of the skunks was based on a positive fluorescent antibody test (FAT) on the hippocampus. One FAT- and virus isolation-negative skunk served as a control. The FAT was positive on 19 mandibular salivary glands, 16 parotid glands, and 17 sublingual glands. Rabies virus was subsequently isolated in albino Swiss mice from all (ie, 19) hippocampi and mandibular salivary glands, 16 parotid glands, and 17 sublingual glands. Virus was not isolated from the FAT-negative tissues. Titers (mouse intracerebral LD50/0.03 ml) were calculated in all FAT-positive tissues by the Reed-Muench method. Rabies titers from hippocampi ranged from 10(0.7) to 10(-4.5); from mandibular salivary glands, 10(2.8) to 10(-7.2); from parotid glands, 10(0.5) to 10(-5.8); and from sublingual glands, 10(-0.3) to 10(-3.8). Results indicate that "rabies-virus inhibiting substance" did not interfere with FAT or virus isolation from tissues of naturally infected skunks.

[2 biological variants of the rabies virus obtained from 1 strain]

Two variants of rabies virus were obtained in experimental mice from one wild strain. They differed in the duration of the incubation and clinical periods and in virus titres. One virus variant produced an acute disease and the other acute and chronic forms of the disease. These properties persisted throughout 21 and 12 successive passages, respectively.

[Electron microscopic study of cell cultures chronically infected with fixed rabies virus]

HEp-2 and Vero cell cultures chronically infected with rabies virus were examined electron microscopically. In the cytoplasm and intercellular spaces of these cultures structures were found morphologically similar to virus particles previously described in cells acutely infected with rabies virus. The observed virus particles were elongated, oval or spherical in shape. Their inner structure appeared as homogeneous material of varying optic density surrounded with a 3-layer membrane. Changes in the ultrastructural organization of the infected cells were observed consisting in the appearance of lipid inclusions, formation of structures of concentrically packed membranes, formation of multilayer areas of the cell membrane.

Defective interfering particles of fixed rabies viruses: lack of correlation with attenuation or auto-interference in mice

Six different fixed strains of rabies virus were analysed for their capacity to produce defective particles following acute infection of BHK-21 cells. Five of the six strains produced one or more defective particle populations with strain-specific sedimentation properties, particle length and abbreviated RNA genome size. These defective particles varied in their capacity to interfere with replication of standard rabies virus in cell culture. Each virus strain characteristically either killed adult mice according to a normal dose-response pattern or to an auto-interference type of pattern, or failed to kill mice. Different strains also varied in their capacity to induce a cytopathic effect in cell culture. However, there was no apparent correlation between the presence of defective particles and the pathogenic potential of rabies virus in mice or in cell culture.

[Pathomorphology of abortive rabies]

White random-bred mice inoculated intraperitoneally with street rabies virus were found to have numerous Babes-Negri bodies in cerebral neurons very frequently up to 5 days of the disease. On the 7-11th days of the disease the inclusions were found in some neurons in 11 of 17 mice examined. Among 24 mice with abortive rabies (recovering completely or surviving with residual symptoms such as pareses or paralysis) examined on the 20-240th days after the onset occasional Babes-Negri bodies were found either in the brain or in the spinal cord in 6 animals only. The central nervous system of these animals showed weak degenerative and inflammatory lesions; the animals had high antibody titers but yielded no virus. It is concluded that in some cases abortive infection becomes a latent one.

Prevalence of rabies virus in foxes trapped in the Canadian Arctic

Brains and salivary glands of 521 trapped arctic foxes (Alopex lagopus) submitted from four different settlement areas in the Northwest Territories were examined for rabies by the standard fluorescent antibody and mouse inoculation tests. Rabies antigen was present in 44 of 201 (21.9%) brains from foxes trapped in the Sachs Harbour area, but submissions from Cambridge Bay (127), Spence Bay (93) and Gjoa Haven (100) were negative. Virus was also present in salivary glands from 43 (97.7%) of these 44 positive foxes. The arctic fox continues to be the main wildlife reservoir of rabies in the Canadian Arctic and foxes in the prodromal stage of the disease pose a particular threat to the trapper. Preexposure vaccination should always be a consideration in this occupational group.

Nonlethal infection of laboratory mice induced with "mouse" rabies strains

Nonlethal infection was induced in laboratory mice with sublethal doses of rabies strains isolated from small wild rodents. Three types of nonlethal infecion were observed: persistent--with virus irregularly reisolable for at least 56 days after inoculation: latent--with negative virus reisolation but presence of infection demonstrable by transmission of virus neutralization activity to other animals; and abortive--with only a primary immune response, nontransmissible to other animals. A hyperreactive state called "early death" was observed in some mice. All surviving animals recovered without sequelae.

Rabies virus infection of a flying fox bat, Pteropus policephalus in Chandigarh, Northern India

The present communication reports for the first time in South East Asia an active infection of frugivorous flying fox bat (Pteropus poliocephalus) with a virus belonging to the Rhabdo virus group -- a bat virus. Negri body like structures were demonstrated by Seller's stain and direct immunofluorescence in the brain and salivary gland of the dead bat. The virus was isolated after intracerebral inoculation of homogenate of the bat brain, salivary gland or brown fat separately in new born mice.

Experimental chronic rabies in the cat

Two cats, inoculated with a street rabies virus strain, survived with only some progressive debility and atrophy of musculature in the injected limb for 136 weeks. They had continuously increasing titers of neutralizing antibody in serum and in cerebrospinal fluid, and terminally they had high antibody titers in the brain. Virus was isolated from two brain specimens of one cat obtained at necropsy; isolation was successful only by explant culture and inoculation of explanted tissue into mice. Virus antigen was detected in eight sites in the brain and spinal cord of the same cat by frozen-section immunofluorescence. Lesions in the central nervous system consisted of neuronal degeneration and neuronophagia, associated with the prescence of inclusion bodies and widespread inflammatory cell inflitration into brain and spinal cord parenchyma, perineuronal sites, and perivascular spaces. The inflitrates contained lymphocytes, monocytes-macrophages, and a high proportion of plasma cells. These experimental cases of chronic progressive rabies resembled more closely subacute sclerosing panecephalitis of man than the usual subacute fatal rabies encephalitis of man and other mammalian species.

[Different behaviour of street rabies and virus fixé strains in parabiotic rats (author's transl)]

To resolve the problem by which route rabies virus is migrating within the infected organism, coelioanastomosis was performed by operating two albino rats each so that a connection between blood vessels, however not between nerves was established. One of the partners was infected in each case. As soon as one of the parabionts exhibited specific disease, the animals were disconnected again. A comparison of street virus and strains of virus fixé that had been maintained by intracerebral, plantar, and intramuscular passage revealed basic differences. Street virus was found to be transmitted to the non-infected partner almost regularly while virus fixé maintained by intracerebral passage almost never was transmitted. After i.m. passages, plantar virus held an intermediate position.

Experimental rabies in the vampire bat

Vampire bats were inoculated intramuscularly and subcutaneously with varying doses of rabies virus to simulate bites by rabid animals in nature. Daily saliva samples were then taken from these animals to determine whether they excreted virus and for how long. Vampire bats appear to react to rabies virus as do other animals, with variable incubation periods, some excretion of virus in the saliva, but no prolonged excretion "carrier state."

Early events in non-lethal rabies infection

Inoculation of sublethal doses of rabies virus strains isolated from small wild rodents resulted in non-lethal infection of white mice. During the first 48 hr after inoculation the virus neutralizing and protection activities in mouse sera and brain suspensions increased, followed by a transient decrease on the 3rd and 4th day. In some cases there also occurred transient multiplication of virus, which retained a relatively high infectivity for mice.

Ultrastructure of peripheral nerves of mice inoculated with rabies virus

Fourty adult female albino mice were inoculated in the right hind leg with rabies viruses of the street type. The mice were sacrificed with an interval of 24 hours each, starting in the next day after inoculation. From the 10th day ownwards the animals started presenting signs of paralysis, first on the leg where the viruses were inoculated anbnormalities were found in peripheral nerves compatible with axonal degeneration with secondary demyelination but the rabies viruses were not found in the axoplasm, myelin sheet, Schwann cell cytoplasm, endoneural or in the epineural structures.

Chronic form of experimental rabies in mice

The L-28 strain of street rabies virus isolated from the salivary gland of a red fox caused chronic infection in mice. After intracerebral (i.e.) infection with virus-containing fox salivary gland suspension, 13.9% of mice showed clinical signs of disease for 11--52 days. Clear-cut stages of irritation and paralysis were distinguished in the course of infection of mice. The diagnosis of chronic rabies in mice was confirmed by immunofluorescence and isolation of virus by i.c. inoculation of mice. Electron microscopic examination of the Ammon's horn of mice revealed a slow development of morphological changes connected with the formation of virus-specific structures. The gradual increase in the number and size of aggregates of viral ribonucleoprotein was followed by the appearance of membranous and tubular structures. Along with the latter, typical bullet-shaped particles of rabies virus were found in some neurons on the 43rd day of infection.

Rabies antibody prevalence and virus tissue tropism in wild carnivores in Virginia

Carnivores trapped in a rabies control program in Virginia were examined for rabies virus and serum neutralizing antibody. Local antibody prevalence ranged from 0% to 29% in gray foxes (Urocyon cinereoargenteus). Rabies virus was pantropic in naturally infected gray foxes and a bobcat (Lynx rufus).

Rabies: recent advances in pathogenesis and control

Current knowledge of rabies is reviewed, with emphasis on recent developments in virology, immunology, pathogenesis, treatment, and prophylaxis. Although only a few cases of human rabies occur annually in the United States, the infection is enzootic in wildlife, and an estimated 30,000 possible exposures requiring treatment occur each year. Rabies belongs to the family rhabdovirus, and its molecular anatomy and biochemistry of replication have been described in some detail. There have been advances in measurement of antirabies antibodies, and techniques for measuring cellular immune response have recently been developed. Early stages of infection are more fully understood, with a hypothesis to explain peripheral sequestration of virus during prolonged incubation periods. Rabies was once thought to be uniformly f fatal, but a few patients have survived with aggressive supportive measures. A newly developed vaccine (soon to be licensed in the United States) has been shown highly potent for preexposure immunization and promises to be very effective for postexposure prophylaxis. Current Public Health Service recommendations for postexposure treatment are summarized. Recent research has suggested a novel approach to control of wildlife rabies through oral immunization.

Characteristics of 11 rabies virus isolates in mice: titers and relative invasiveness of virus, incubation period of infection, and survival of mice with sequelae

Mice were inoculated intracerebrally or in the footpad with 11 salivary gland suspensions from rabid foxes, skunks, and bobcats. The 11 isolates differed in their ratios of intracerebral titer to footpad titer, a result indicating that the "invasiveness" of different isolates varies markedly. The degree of invasiveness could not be correlated with the species of animal. The inoculation of the less invasive isolates resulted in an appreciable number of permanently paralyzed animals (survivors with sequelae). These animals had high titers of neutralizing antibody in serum but no neutralizing antibody in the brain, a finding suggesting that virus had invaded only the peripheral nervous system or the spinal ganglia. Pathological examination of the paralyzed mice and normal mice confirmed this finding.

Neurological symptoms in a cat following vaccination with high egg passage Flury rabies vaccine of chicken embryo origin

The development of neurological symptoms in a cat following vaccination with the high egg passage Flury rabies vaccine and the subsequent isolation of a virus with characteristics consistent with the criteria for distinguishing the high egg passage Flury strain of rabies virus are described.

[Chronic cell culture infection with the rabies virus]

Three cell cultures chronically infected with fixed rabies virus, strain MNIIVP-74, have been obtained: HEp-2/2, BHK/13S, and RK-13. In the former two cultures, the infectious virus titers were 2.0 to 5.25 Ig LD50/ml. In RK-13 cells, traces of the infectious virus were found. In the chronically infected HEp-2/2 culture the maximum amount of the antigen-containing cells determined by the fluorescent antibody procedure was 60% and in BHK/13S 80%. Chronically infected cultures had a reduced growth rate and were as sensitive as the controls of superinfection with vesicular stomatitis virus. The virus recovered from chronically infected culture produced a disease in mice at later intervals than the original virus used in the same doses.

Rabies virus and antibody in bats in Grenada and Trinidad

Rabies virus was detected by fluorescent-antibody and mouse inoculation tests in the brain of one bat, Artibeus jamaicensis, collected at La Tante, Grenada on 19 June 1974. No rabies virus was found in the brains and/or salivary glands of 411 other Grenadian bats of 6 species tested, including 56 A. jamaicensis. Rabies neutralizing antibody was detected by the rapid fluorescent focus inhibition test (RFFIT) in 27 of 353 Grenadian bats. Positives occurred in each of the 6 species sampled, with 40.5% prevalence in A. jamaicensis. In 11 of 86 Trinidadian bats of 4 species known to carry rabies, positive sera occurred only in A. jamaicensis (18.6%) and A. lituratus (18.1%). The potential use of the REFIT indetermining rabies activity is discussed.

Airborne rabies encephalitis: demonstration of rabies virus in the human central nervous system

A veterinarian contracted rabies in the course of laboratory work with homogenates of rabid goat brain. Epidemiologic study determined a respiratory mode of transmission. After a fulminant encephalitic illness, formed rabies virions were identified in the synaptic zones of the olfactory glomeruli. Identification, isolation, experimental disease production, and tissue cytopathic effects of virus recovered from the brain fulfilled Koch's postulates in this unusual instance of virus disease of the nervous system.