411

Aguaruna communities, where medical care is available onlyfrom lay health promoters, the only medicines are basicanalgesics and antibiotics, the nearest health centre, inSanta Maria de Nieva, is about 5 h away by boat duringgood weather, and rabies vaccines for man are availableonly in Bagua Chica, which is about 18 h away in goodconditions.

Differences between the two communities in type of

housing, use of mosquito nets, and in geographicdistribution of bats may account for the finding that theproportion of Mamayaque residents who died was about sixtimes that in Tutino. Like Hurst we found that deaths werecommonest among children aged 5 to 14 years. Our

investigation suggests that this finding was probably due totheir likelihood of being bitten because of the non-use ofmosquito nets.Low concentrations of rabies neutralising antibody were

found in some healthy relatives of the victims. However,these concentrations did not seem to be related to exposureto bats or epidemiological factors (age, sex, other animalexposures). Although specific information about previousvaccination was not solicited, rabies vaccine had beenavailable to members of this community only once, about 10years previously, after a similar outbreak. Since there was nostatistical relation between age or exposure to bats and

antibody concentration, and since the level of neutralisingantibody was quite low, we believe that the antibodyconcentrations were non-specific. Similar low levels of

neutralising antibody have been reported in unvaccinatedanimals (J. Smith, unpublished).Unpublished reports suggest that similar outbreaks have

occurred in this region for several years, and unless measuresare taken outbreaks will continue to occur. Perhaps thesimplest feasible measure would be the vigorous cleansing ofall suspected bat bites with soap and water. Soap is anexcellent virucidal agent and may alone substantially reducethe risk of exposure. Other measures that should beconsidered include the increased use of physical barriers toreduce the likelihood of bites (ie, bat-proofing of houses anduse of mosquito nets).Although clearly desirable, the widespread use of rabies

pre-exposure or postexposure prophylaxis seems unlikely incommunities such as these. Community-wide rabies pre-exposure prophylaxis would probably protect man afterinapparent or unrecognised exposures to vampire bats, aswell as those with recognised exposure but who do not haveaccess to postexposure therapy. However, delivery of athree-dose pre-exposure regimen to such isolated

populations would be logistically difficult and possiblyprohibitively expensive. Furthermore, how much

protection this approach confers is not known-boosters arebelieved to be necessary to assure protection after exposureto rabies.2° When pre-exposure immunity begins to wane,the need for boosters would increase costs. There is no

programme of childhood immunisation in these villages.Universal pre-exposure immunisation against rabies givenin conjunction with other childhood vaccinations could beone solution, but vaccine interactions would have to becarefully studied. The cost-benefit and cost-effectiveness ofrabies pre-exposure vaccination versus other possible publichealth interventions would therefore have to be determined.

We thank our veterinarian colleagues-Dr Victor Altamirano, Dr AugustoRodriguez, and Dr Cesar Oliden-and Dr Thomas Betz for their help withthe field investigation and Ms Jean S. Smith, Ms Pamela Yager, Dr GeorgeM. Baer, and Dr James Olson for editorial comments and help withlaboratory studies.

REFERENCES

1. Gut HJ. A pleistocene vampire bat from Florida. J Mammal 1959; 40:534.

2. Acha PN, Epidemiology of paralytic bovine rabies and bat rabies. Bull OffInt Epizoot 1967; 67: 343-82.

3. Carini A. Sur une grande épizootie de rage. Ann Inst Pasteur (Paris)1911; 25: 843-46.

4. Arellano-Sota C. Vampire bat-transmitted rabies in cattle. Rev Infect Dis1988; 10 (suppl 4): S707-9.

5. Hurst EW, Pawan JL. A further account of the Trinidad outbreak ofacute rabies myelitis. J Pathol Bacteriol 1932; 35: 301-21.

6. Hurst EW, Pawan JL. An outbreak of rabies in Trinidad without historyof bites and with the symptoms of acute ascending paralysis. Lancet1931; ii: 622-25.

7. Waterman JA. Acute ascending rabic myelitis. Rabies-transmitted bybats to human beings and animals. Caribbean Med J 1959; 21: 46-74.

8. Nehaul BBG. Rabies transmitted by bats in British Guiana. Am J TropMed Hyg 1955; 43: 550-53.

9. Verlinde JD, Li-Fo-Sjoe E, Veersteeg J, Decker SM. A local outbreak ofparalytic rabies in Surinam children. Trop Geogr Med 1975; 27: 137-42.

10. Veterinary Public Health Unit. World Survey of Rabies XXII (for years1984/85). Geneva: World Health Organisation, 1987. WHO/Rabies/89.199.

11. McCarthy TJ. Human depredation by vampire bats Desmodus rotundusfollowing a hog cholera campaign. Am J Trop Med Hyg 1989; 40:320-22.

12. Malaga-Alba A. Vampire bats as a carrier of rabies. Am J Public Health1954; 44: 909-18.

13. Goldwasser RA, Kissling R. Fluorescent antibody staining of street andfixed rabies virus antigens. Proc Soc Exp Biol Med 1958; 98: 219-23.

14. Smith JS, Reid-Sanden FL, Roumillat LF, et al. Demonstration of

antigenic variation among rabies virus isolates by using monoclonalantibodies to nucleocapsid proteins. J Clin Microbiol 1986; 24: 573-80.

15. Dean ADF, Dean JA, Burton JH, Dicker RC. Epi Info, Version 5: a wordprocessing, data base, and statistics program for epidemiology onmicrocomputers. Atlanta, Georgia: Centers for Disease Control, 1990.

16. Smith JS. Rabies virus epitopic variation: use in ecologic studies. AdvVirus Res 1989; 36: 215-53.

17. Nehaul BBG, Dyrting AE. An outbreak of rabies in man in BritishGuiana. Am J Trop Med Hyg 1965; 14: 294-96.

18. Lord RD, Delpietro H, Fuenzalida E, De Diaz AM, Lazaro L. Presenceof rabies neutralizing antibodies in wild carnivores following anoutbreak of bovine rabies. J Wildl Dis 1975; 11: 210-23.

19. Johnson HN. General epizootiology of rabies. In: Nagano Y, DavenportFM, eds. Rabies. Baltimore: University Park Press, 1971: 237.

20. Anon. Human rabies-Kenya. MMWR 1983; 32: 494-95.

From The Lancet

Pig as middleman

The Local Government Board and the Board of Agriculture andFisheries are concerning themselves with the necessity for

increasing the food productions in the country by the developmentof pig, poultry, and rabbit breeding. In regard to the two latter, fewhygienic or dietetic problems arise. But the recommendation toincrease the number of pigs, and that not only in rural districts,where space is abundant and neighbours are distant, raises verydifferent questions. The hygienic aspect is at once apparent.... Thepigsty often smells not because of the pig, but because of theignorance of his keeper. But on the dietetic side, in recommendingpig culture as an economical pastime the fact must not be lost sightof that the alimentary canal of the pig is adapted for much the samekind of food as the human child’s. The growing pig is a typicalomnivore and ordinarily receives a large amount of nutritivematerial, some of which the growing child could well digest.Experiments have shown that via the pig as middleman only some25% of the protein and some 45% of the total energy value of thefood supplied him is ultimately returned to the consumer as pork orbacon. Brokerage of at least 55%, which may well be largelyexceeded, is charged by the pig.

(Jan 13, 1917)