A Study of an Outbreak of Bacillary Dysentery with Particular Reference to Detection of its Source and Disseminating Route

Abstract

The drive ‘extrerminate bacillary dysentery’ was conducted in Johana Town, Toyama prefecture during a 3-year period (1962-1964) with every possible measure to be taken at that time.
Notwithstanding such comprehensive countermeasures, an outbreak of bacillary dysentery took place in a creche belonging to town's authority in Feb. 1965.
Both bacteriological and epidemiological investigations were carried out on it. By means of colicine typing technique and drug-sensitivity test on the causative organisms, the source of epidemic was pursued successfully, and at the same time it was made almost clear that contact infections played the main role in disseminating the germs through the epidemic.
This report was submitted from such a viewpoint of the author that these findings would bear the great importance to the prophylaxis of epidemic of this kind of disease.
Results were summed up as follows:
1) An outbreak of bacillary dysentery, occurring in a creche of Johana Town, durated for 27 days from Feb. 5 to Mar. 3, 1965. The creche was, at that time, taking care of 224 infants. The patients involved were 126 in total, including infants of the creche and their families. The peak of incidence was at around 7th and 8th day of the outbreak, and a number of incidence were lingering until the end of epidemic.
Out of total, the majority (65, 53.1%) were infants of 4-5 years age. The second highest incidence was seen in 25-34 years age group of female, mostly the mothers of diseased infants.
Viewing above results, the mode of this epidemic should be appropriately described as ‘continuative lingering’ pattern rather than as ‘in a moment, massively explossive’ pattern. And the fact that the patients involved were mainly infants and their mothers, is suggestive of contact infection as the cause of germ dissemination. Water supply or meals provided by the creche would be almost deniable as a cause of epidemic.
2) The modified colicine typing teehnique by Abbott et al and drug-sensitivity test were applied to detect the route of infection.
Strains isolated through this epidemic were all Sh. sonnei of colicine type 12, and at the same time resistant to three drugs (streptomycin, tetracycline and chloramphenicol) without exception.
It happened to be that a mother, whose child was a patient in earliest incidence, was found to be a healthy carrier and, at the same time, in her past history she was diagnosed on Oct. 26, 1964, the previous year to this occasion, as a carrier of Sh. sonnei, its colicine type and drug-sensitivity pattern being identical to that of the causative strains of this time. No other patients' history revealed such one, then she was desided almost definitely to be an epidemic source of this outbreak. The germ would have been disseminated from her child, who was infected first from her, to the infants in creche, further to their families, possibly by contact.
3) It is surprising that Sh. sonnei were recovered from the dust clogging the connections of japanese style mats (tatami) of the creche that were considered to have already been completely disinfected.
It should be borne in mind that the usual procedures for disinfecting japanese house were not satisfactory at least to Shigella bacilli, considering that such dust could have played the role in some part of contact infections in this epidemic.