Neurological disease in man following administration of suckling mouse brain antirabies vaccine*

Bull. Org. mond. Sante 1972, 46, 321-327 Bull. Wid Hith Org.f Neurological disease in man following administration of suckling mouse brain antirabies vaccine* J. R. HELD & H. LOPEZ ADAROS 2 In Latin America, suckling mouse brain (SMB) vaccine has become the most com- monly used vaccine for immunization ofboth man and animals against rabies. This vaccine is highly immunogenic, is relatively economical and easy to produce, and is believed to be free of the immunoencephalitogenic factor. From 1964 to the end of 1969, there were 40 reported cases of neurological disease following administration of SMB vaccine, 32 of which met the criteria for inclusion in this report. These 32 cases occurred in 8 different countries. In contrast to neurological disease following the administration of other types ofnervous tissue vaccine, the majority of the cases following vaccination with SMB vaccine had a Guillain-Barre-type syndrome with peripheral nervous system involvement and a higher case-fatality rate. The causative agent has not been demonstrated. Modifications in the production and handling ofthe vaccine may be producing changes that are responsible. INTRODUCTION Post-exposure immunoprophylaxis of man against rabies has long been the physician's dilemma because of the well-known risk of a neuroparalytic accident resulting from the administration of the vaccine. This type of reaction is generally considered to be allergic in nature and provoked by the presence of central nervous system myelin in vaccines prepared from the brains and/or spinal cords of infected animals. In the past, the animals most commonly used were adult rabbits, sheep, or goats. In an effort to reduce or eliminate this risk, various vac- cines have been developed in which the virus is grown in embryonated eggs that are free, or nearly free, of myelin. Fuenzalida & Palacios (1955) in Chile reported the development of an antirabies vaccine produced in suckling mice. Their primary reason for using suckling mice, which are highly susceptible to rabies virus, was to produce a vaccine with a very high titre. The mice are inoculated when they are 3-5 days old and their brains are harvested when they are 7-9 days old. Myelin has not formed in the brains of mice at that age, and the vaccine is believed to be F i * From the Pan American Zoonoses Center, Pan Ameri- can Sanitary Bureau, Casilla 23, Ramos Mejia, Prov. de Buenos Aires, Argentina. 1Veterinary Epidemiologist. Epidemiologist. free of the immunoencephalitogenic factor, which is an additional benefit. Because of this, and because this vaccine is highly immunogenic and is relatively economical and easy to produce, it has become the most commonly used vaccine in Latin America for the vaccination of both man and animals. Nearly all vaccines produced in suckling mouse brains are called Fuenzalida vaccines, but in reality there are several different suckling mouse brain (SMB) vac- cines. A 0.03-ml quantity of the vaccine for use in man as originally described and currently produced in many places contains: supernatant from a 1% suspension of brain tissue, 105MLD50 of rabies virus, inactivated by ultra- violet light, double-distilled water, phenol 1 : 1 000 as a preservative, and thiomersal 1: 10 000 as a preservative. Some vaccine producers have somewhat empiri- cally modified the vaccine in different ways or have omitted some steps. For example, 0.5% brain super- natant is used instead of 1 %, or /3-propiolactone (2-oxetanone) or phenol may be used to inactivate the virus instead of UV light: sometimes diluents other than distilled water are employed. Some pro- ducers do not centrifuge the brain suspension. 2807 - 321- 322 J. R. HELD & H. LOPEZ ADAROS The first reported neuroparalytic accident follow- ing the use of SMB vaccine occurred in a patient in Venezuela (Lopez Adaros, 1967). Further investi- gation revealed that this case was somewhat unchar- acteristic of neuroparalytic accidents following vac- cination with other types of nerve-tissue vaccine in that the clinical syndrome concerned the peripheral rather than the central nervous system. In Venezuela, a programme of surveillance was initiated to detect the occurrence of such cases. It was found that one case had occurred in 1966; 14 cases were reported in 1967 and 3 in 1968. The most striking feature of these cases was that most of them involved the peri- pheral nervous system. Of the 18 cases reported during these 3 years in Venezuela, one was a fatal encephalitis, which could possibly have been caused by a rabies infection, and two were peripheral in nature but were mild, not showing sufficient signs to warrant their inclusion in this study. Of the remaining 15 cases, 1 1 could be classified as Guillain- Barre syndrome. Of the 15 cases, 1 occurred in 1966, 11 in 1967, and 3 in 1968 (Table 1). Vaccines produced by two different manufacturers were involved. After the first cases occurred, vaccine production was terminated by producer A and the same type of vaccine was imported from producer B, located in another coun- try nearly 5 000 km away. After the occurrence of the cases, the various lots of vaccine involved were Table 1. Number of cases of neurological disease in man following antirabies prophylaxis with SMB vaccine in Venezuela by year, producer, and lot number of vaccine, 1 966-68 Vaccine Year Total Producer Lot no. 1966 1967 1968 A 37 1 1 46 4 4 48 2 2 43/50 a 1 1 unknown 1 1 B 4 3 2 5 5 1 1 total 1 11 3 15 a One case was given vaccine from two different lots. tested for safety, purity, and sterility; and the only significant finding was the presence of minute amounts of active rabies virus in vaccine lot no. 46. Of the four cases of disease that followed vaccination with this lot, only one patient died; and no rabies virus could be isolated from his brain. About 500 patients vaccinated with lot no. 46 were kept under surveillance for more than a year, and there was no evidence that rabies occurred in any of them. No rabies virus could be isolated from any of the other lots of vaccine. Studies of patients' sera for different microbial antibodies, including the most common human and murine viruses, were inconclusive." In Venezuela, which has a population of approxi- mately 9 million persons, 30-40 cases of Guillain- Barre syndrome are reported annually. Among the 20 000 persons who were vaccinated in 1967 and 1968 there were 14 cases. The authorities of the Depart- ment of Demography and Epidemiology, Ministry of Health and Social Assistance, felt that the asso- ciation between the use of vaccine and the observed syndrome was statistically significant in comparison with the incidence of the syndrome among the non- vaccinated population. Because of these cases, the Pan American Zoonoses Center initiated a surveil- lance programme in an attempt to collect informa- tion and specimens for examination from cases that had occurred with this vaccine in any country in the past and from those that might occur in the future. Suckling mouse brain vaccine for rabies immuno- prophylaxis in man was first introduced into general use in Chile in 1963 (Table 2). In that year a total of 16900 persons were vaccinated with 14 doses each in Chile, and an unreported number were vac- cinated shortly thereafter in Uruguay. In 1969, Ecuador and Guatemala began producing SMB vac- cine, making a total of at least 11 countries in which it was then employed. Each year there was a sub- stantial increase in the use of this type of vaccine, and more than 1/2 million persons were vaccinated with it between 1963 and 1968. CASES OF NEUROLOGICAL DISEASE So far, information has been received on 40 cases of neurological disease following the administration of suckling mouse brain vaccine. Of these, 8 cases were eliminated; one was a fatal case on which no autopsy was done and the history of which could 1 Trejos, A., Lewis, V., Fuenzalida, E., & Larghi, 0. P., unpublished results. NEUROLOGICAL DISEASE IN MAN AFTER RABIES VACCINATION Table 2. Number of persons (in thousands) given suckling mouse brain vaccine in Latin America by country and year, 1963-68 Year a Country Total 1963 1964 1965 1966 1967 1968 Chile 16.9 b 10.0 10.0 8.0 7.0 7.0 58.9 Uruguay ?b ? ? 20.0 ? 7 20.0 Argentina 15.0 b 15.0 15.0 25.0 30.0 100.0 Peru 10.0 b 10.0 10.0 10.0 10.0 50.0 Brazil 20.0 b 25.0 35.0 35.0 115.0 Venezuela 9.6 b 10.0 10.0 10.0 39.6 Colombia 20.0 b 20.0 20.0 60.0 Cuba ?b ? ? Mexico 7.0 b 60.0 67.0 total 16.9 35.0 64.6 108.0 114.0 172.0 510.5 a ? = SMB vaccine used but quantitative information not available. b Year in which SMB vaccine was first used in the indicated country. have been compatible with rabies, and the other 7 were cases for which the information submitted lacked conclusive evidence of the presence of neuro- pathology. Of the 32 remaining cases considered in this report, the first occurred in Argentina in 1964, the first year in which SMB vaccine was used in that country (Table 3). After 1964, the number of cases per year increased until 1967, and since then the annual number has decreased each year. The cases occurred in several different Latin American countries, but the greatest concentration was in Venezuela. Of the 32 cases, 7 (21.9%) presented a predomi- nantly central nervous system disease syndrome while 22 (68.7%) involved the peripheral nervous system; in 3 cases the details were not reported. Paralysis was present in 26 cases and absent from 4, and its presence or absence was not reported in 2 cases. One of the 4 central and 6 of the 19 peripheral nervous system cases were fatal. The overall case- fatality rate was 21.9%. Autopsies were performed on 5 of the 7 fatal cases, and rabies virus could not be isolated from any of them. Demyelinization was noted at autopsy in 4 cases: the examination of the fifth case was not suitable for the detection of this type of change. The characteristics of the neurological disease in those cases that followed the administration of other types of nervous-tissue vaccine (as reported in the literature) were compared with those of the cases that followed the use of suckling mouse brain vaccine Table 3. Number of reported cases of neurological disease in man following antirabies prophylaxis with suckling mouse brain vaccine, January 1964-October 1969 Year a Country Total 1964 1965 1966 1967 1968 1969 Argentina 1b - - - 2 2 5 Peru -.b 2 - 1 - - 3 Uruguay ..b - 2 - I - 3 Brazil -b - - - 2 2 Venezuela -b 1 11 3 - 15 Colombia -.b - 1 1 2 Mexico -.b 1 - 1 Guatemala - b 1 1 total 1 2 3 12 8 6 32 a _ = no reported cases. b Year in which SMB vaccine was first used in the indicated country. 4 323 J. R. HELD & H. LOPEZ ADAROS Table 4. Reported cases of neurological disease in man following antirabies prophylaxis with suckling mouse brain vaccine, January 1964-October 1969: age and sex distribution SexAge group MalesFemale Total Percentage(er) Male Female 0-4 1 a 1 2 6.2 5-9 1 0 1 3.1 10-14 1 5 6 18.7 15-19 0 3 3 9.4 20-29 3 a 2 a 5 15.6 30-39 6 a 2 8 25.0 40-49 3 b 2 5 15.6 50-59 2 - 2 6.2 total 17 15 32 100.0 percentage 53.1 46.9 100.0 a 1 fatal case. b 3 fatal cases. and some striking differences were revealed. Follow- ing the administration of suckling mouse brain vac- cine there was a higher proportion of cases with peripheral nervous system involvement and a higher case-fatality rate. In a review of published reports (Appelbaum et al., 1953; Assis & Duchene, 1957; Gospavic et al., 1963; Pait & Pearson, 1949; Rodri- guez Arias et al., 1958; Uchimura & Shiraki, 1957), data were found on 90 cases and, of these, 92.2% involved the central nervous system whereas only 21.9% of the SMB cases involved the CNS. The case-fatality rates were also different: 21.9% of the cases following the use of SMB vaccine and 4.8% of those following the use of Semple, Fermi, or Hempt vaccines. Although the percentage of cases with central involvement and the percentage of case fatalities following the use of SMB vaccine were the same, it was noted earlier that six of the deaths were patients with peripheral nervous system disease and that only one had central nervous system disease. The case-fatality rate following the administration of SMB vaccine was similar to the 20% case-fatality rate reported for Guillain-Barre syndrome from other causes. In 15 cases, the protein and cell contents of the cerebrospinal fluid were reported. Protein contents ranged from 12 to 185 mg per 100 ml with a median of 74 mg/100 ml. The number of cells per cubic millimetre ranged from 0 to 70 with a mean of 3. The cases occurred in all age groups from 0 to 59 years and in both sexes (Table 4): 53.1 % of the cases were males and 46.9% were females. The largest number of cases was in the 30-39-year age group. Of the 7 fatalities, 1 occurred in a male 11/2 years of age. The remainder occurred in persons between 20 and 49 years of age. In Latin America, 41.7% of the population is under 15 years of age, 49.5% is in the 15-59-year age group, and 8.8% is 60 years of age or over (Table 5). Information on the age and sex distribution of persons vaccinated with antirabies vaccine is not readily available. Data from three different areas (the cities of Buenos Aires, Argentina, and Lima, Peru, and the Department of Cordoba, Colombia) have been ob- tained and may indicate which age and sex groups are most commonly vaccinated. Buenos Aires is a somewhat uncharacteristic Latin American city in Table 5. Percentage distribution by age and sex of the population in Latin America, of three groups of persons vaccinated against rabies, and of cases of neurological disease following vaccination with SM B vaccine Age group (years) Population of Groups of vaccinated persons in: SMB andgroups(years) PopulationAmea accidentwsex Latin Americ Argentina Colombia Peru group 0-14 41.7 36.7 58.1 49.3 28 15-59 49.5 55.7 47.9 72 41.9 _60 8.8 7.6 2.8 0 male 50 58 54.3 67.1 53.1 female 50 42 45.7 32.9 46.9 324 NEUROLOGICAL DISEASE IN MAN AFTER RABIES VACCINATION Table 6. Distribution of the reported cases of neuro- logical disease in man following antirabies prophylaxis with suckling mouse brain vaccine by number of days to onset of symptoms January 1964-October 1969 No. of days from first Cases dose to onset of symptoms No. % 4-6 4a 13.3 7-9 1 3.3 10-12 8 26.7 13-15 11 36.7 16-18 5 16.7 25 1 3.3 not reported 2 total 32 100.0 aTwo of these subjects had received antirabies immunopro- phylaxis previously. that it has a predominantly older population. The percentage of those under 15 years of age vaccinated in recent years was 36.7% in Buenos Aires, 58.1 % in Cordoba, and 49.3% in Lima. Among the per- sons vaccinated, 35-58% were under 15 years of age. If the post-vaccinal reactions occurred uni- formly in all age groups, it would be expected that 35-58% of the cases would be under 15 years of age; however, in this survey only 28% of cases were in this age group. Although actual incidence data are not available, this finding suggests that the prevalence of reactions may be considerably higher in the age groups over 15 years. In all three areas, more males than females were vaccinated against rabies, 58% of the total being male in Buenos Aires, 54.3% in Cordoba, and 67.1% in Lima. The pro- portion of males in the group that experienced neurological accidents was similarly higher. The delay between injection of the first dose of vaccine and the onset of symptoms ranged from 4 to 25 days, with a median delay of 13 days (Table 6). In at least 3 cases, the patients had been given anti- rabies vaccine on a previous occasion: one of these had an incubation period of 5 days, one of 6 days, and one of 17 days. Fourteen of the patients received 14 doses of vac- cine and 13 received less than 14 doses (Table 7): all except one of the latter group received less than 14 doses because administration of the vaccine was Table 7. Distribution of the reported cases of neuro- logical disease in man following antirabies prophylaxis with suckling mouse brain vaccine by no. of doses received, January 1 964-October 1969 No. of doses No. of cases 5-7 6 8-10 2 11-13 5 14 14 16 1 21 2 25 1 not reported 1 total 32 suspended upon the onset of symptoms. The one exception was a patient who received 7 doses of vaccine when revaccinated after a new exposure to rabies less than 12 months after a primary course of 14 doses. This was the patient with an incubation period of 17 days. Of the 32 patients, 7 were exposed to known rabid animals and 2 to nonrabid animals; for 23 the health status of the animal was unknown or not reported. Eighteen were bitten or scratched by the exposing animal, 3 had only contact, and for 11 the type of exposure was not reported. Antirabies serum was administered to 2 of the patients and antitetanus serum to 4. In 14 cases no antiserum was administered and in 12 cases it was not reported whether antiserum was administered. Nine different producers manufactured the vaccines administered to these patients. Two cases occurred in two different countries in patients treated with vaccine from the same manufacturer; only in Vene- zuela, however, was there more than one case asso- ciated with any one lot of vaccine. DISCUSSION The finding in Venezuela of such a high rate of the Guillain-Barre syndrome among vaccinated per- sons compared with the rate in the general popula- tion, and the temporal relationship between the administration of vaccine and the onset of symp- toms in all the cases, support the hypothesis that 325 326 J. R. HELD & H. LOPEZ ADAROS these cases were vaccine associated. If this hypo- thesis is accepted, the causative agents could be an infectious agent, a toxic product, or an allergen. Laboratory studies of the batches of vaccine con- cerned and of specimens from patients have been carried out and these will be reported elsewhere (Trejos et al., unpublished data). So far, none of these etiological agents has been found. Perhaps the most difficult agent to demonstrate would be an allergen. Theoretically, suckling mouse brain vac- cine should contain no myelin and should produce no allergic encephalomyelitis or allergic peripheral neuritis. It is possible, however, that there are minute amounts of brain myelin present and that we are seeing the manifestations of a cross-reaction between central and peripheral nervous system tis- sues, or that small amounts of peripheral nerve tis- sue are incorporated into the vaccine and that the syndrome is an allergic neuritis provoked by peri- pheral nerve myelin. It is also possible that the reac- tions might result from the potentiation by one of the vaccine constituents of an etiological agent com- pletely unassociated with the vaccine. It is known that the condition occurs in unvaccinated persons and perhaps the rate is higher in vaccinated persons only because of a synergistic effect. For example, contamination by microorganisms considered non- pathogenic might result in the presence of metabolic products that act as an adjuvant. One possibility that must be considered is that modifications in the production and handling of the vaccine may be producing subtle changes in the end- product that are responsible. More than half of these 32 cases were given vaccine that was produced by methods differing, in one way or another, from the techniques originally described and tested by Fuenzalida & Palacios (1955). Finally, it should be noted that in 1967 in Latin America, the rate of neuroparalytic accidents follow- ing the use of this vaccine was only 1 in 7 865 per- sons treated, in comparison with the rate of 1 in 2 844 persons treated with Semple-type vaccine.' It is apparently nearly 3 times as safe. As a part of its programme, the Pan American Zoonoses Center will continue to maintain its sur- veillance of such complications and, in co-operation with investigators in other agencies, will try to arrive at more definite conclusions regarding the etiological factor involved in these cases. 1 World Health Organization (1968) World survey of rabies, IX (unpublished document WHO/Rabies/68.167). RESUME AFFECTION NEUROLOGIQUE CHEZ L'HOMME APRES ADMINISTRATION DE VACCIN ANTIRABIQUE PREPARE SUR CERVEAU DE SOURICEAU NON SEVRt Le vaccin antirabique prepare sur cerveau de souriceau non sevre (vaccin SMB), mis au point en 1955, est le plus couramment utilise pour l'immunisation de l'homme et des animaux en Amerique latine. Fortement immuno- gene, il est ais6 a produire et relativement peu cofiteux. En outre, comme on emploie des souriceaux ages de 7 it 9 jours, dont le cerveau ne contient pas de myeline, on considere que ce vaccin est depourvu de facteur ence- phalitogene. Le premier cas d'affection neurologique consdcutive 'a l'administration prophylactique de vaccin SMB a ete signale au Venezuela en 1967. Apres investigations, il est apparu que des cas similaires etaient survenus dans d'autres pays d'Amerique latine et qu'avant 1967 il s'en etait produit 6 qui n'avaient fait l'objet d'aucun rapport. Au total, de 1964 it 1969 on a compte 40 accidents neuro- logiques suivant l'administration du vaccin. Huit d'entre eux ont ete exclus de la presente etude, l'un pour diag- nostic de rage douteux, les autres pour atteinte neurolo- logique non demontree avec certitude. Les 32 cas restants ont ete observes dans huit pays d'Amerique latine, et pres de la moitie au Venezuela. Les complications dues au vaccin SMB different des accidents neuro-paralytiques observes apres administra- tion d'autres types de vaccins prepares sur tissu nerveux. Elles revetent le plus souvent la forme d'un syndrome de Guillain-Barre. Les atteintes du systeme nerveux peri- pherique sont plus frequentes et le taux de letalite plus eleve. Les cas surviennent dans tous les groupes d'age et dans les deux sexes. L'incidence parait notablement plus forte chez les sujets ages de plus de 15 ans. Le delai entre l'injection de la premiere dose de vaccin et l'appa- rition des sympt6mes, qui varie de 4 a 25 jours, est en moyenne de 13 jours. Dans 3 cas au moins, les malades avaient requ anterieurement du vaccin antirabique. Plusieurs faits plaident en faveur de l'hypothese selon laquelle ces accidents neurologiques sont lies a la vacci- NEUROLOGICAL DISEASE IN MAN AFTER RABIES VACCINATION 327 nation antirabique. Le facteur responsable, qui pourrait etre un agent infectieux, un produit toxique ou un aller- gene, n'a pas ete identifie. II se peut que des modifica- tions legeres du produit final, resultant de procedes de fabrication differents de la technique originale, soient a l'origine des accidents. I1 reste que la frequence des troubles neuro-paralytiques apres administration du vac- cin SMB est faible et, d'apres des donnees recentes rela- tives a l'Amerique latine, apparemment trois fois moins elevee qu'apres emploi de vaccins de type Semple. REFERENCES Appelbaum, E., Greenberg, M., & Nelson, (1953) J. Amer. med. Ass., 151, 188-191 Assis, J. L. de & Duchene, G. H. (1957) Arch. Neuro- psiquiat., (S. Paulo), 17, 235-250 Fuenzalida, E. & Palacios, R. (1955) Bol. Inst. bact. Chile, 8, 3-10 Gospavic, J. et al. (1963) Srpski Arh. Celok., 91, 141-148 Lopez Adaros, H. (1967) Rev. Fed. med. Vesez., 17, 34-35 Pait, C. F. & Pearson, H. E. (1949) Amer. J. Publ. Hlth, 39, 875-877 Rodriguez Arias, B. et al. (1958), Rev. neurol., 98, 807-814 Uchimura, I. & Shiraki, H. (1957) J. Neuropath. exp. Neurol., 16, 139-203