CHAPTER 2. CHAPTER 2. IMPORTANT MILK-BORNE DISEASES OF MAN
A. THE COW AS. CHIEF RESERVOIR AND SPREADER OF INFECTION
3. SCARLET FEVER AND SEPTIC SORE THROAT
Attention was first directed against milk as a vehicle for spreading scarlet fever by Taylor (1870), but this report was overlooked, and it was not until a series of extensive epidemics occurred around about 1912, that general attent. ion was focussed upon milk. One of these outbreaks, described by Capps and Miller (1912), involved
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more than 10,000 cases, but a full review of the epi- dEmiology of scarlet fever during this phase is given by Armstrong and Parr an ( 192?). At this stage it was almost universally believed that some human carrier of strepto- cocci invariably contaminated the milk, but even at this early stage Savage (1911) advanced the hypothesis that scar- let fever streptococci might invade the cows udder, whilst Davis (1912) and Smith and Brown (1915) also favoured this view. The idea was reiterated by Savage in (1931), and again by Minett (1932a), but it was very generally rejected at this stage. The accurate streptococcal typing methods introduced by Lancefield paved the way for the final prov- ing of the hypothesis in a joint report by Bendixen and Minett (1938) describing an outbreak in Denmark, and
another at Doncaster in England, in which the scarlet fever epidemics were definitely caused by cows suffering from Strep. PY£g~ mastitis.
In most of the earlier investigations very ex- tensive efforts were made to find some human carrier, who had had direct or indirect contact with the milk. Vlhen it is remembered that the streptococcal carrier-rate can rise to as high as 25% of the population (vide Topley and Wilson 1936), it will be appreciated that a carrier can generally be found somewhere. In Table 11 is given a list of some of the main epidemics that have been reported fairly fully, the references being classified according to whether or not any serious effort was made to look for a cow carrying scarlet f~ver streptococci in the udder. From this table it is fairly clear that in the majority of ex- tensive epidemics a cow will be found to be a carrier, if an immediate and ,a careful search is made.
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T A B L E 11.
Bibliography referring to rep arts of milk- borne Strep .pyogene s epidemics.
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Cows examined Capps & Miller 1912; Krumweide & Valentine and one incri -
minated. (1915); Rosenau & Hesse·(l9l?); Smillie(l91?) Brown & Orcutt (1920); Benson & Sears (1923);
Frost & Carr (192?); Jones & Little (1928);
Broqkes (l930a); Golledge (1932); Archibald
& Freernster (1932); Robinson & McComb (1932);
Rambe & Hedstrom (1934); Stebbins et alia (193?); Report (193?); Bendixen & Minett(l938) ---~D~o~u~g~las et alia (1941); Dublin et alia{l94~~
Cows not exam- Report ( 1910); Winslow ( 1912); Rosenau &
ined or none
incriminated. Moon (1915); Wilkenson (1931); Welch &
Mickle (1933); Report (1935 b); Camps &
Wood (1936); Sleigh (1936); Stebbins et alia (193?); Henningsen & Ernst (1939).
Of the reports referred to in the lower section, with two exceptions only (viz:- Henningsen & Ernst 1939 and Stebbins et alia 193?) no serious attempt was made to incriminate a cow, or else any effort was made long after the epidemic had subsided.
With the weight of evidence set out by Pullinger and Kemp (193?), and by Bendixen&Minett (1939), it might be thought that the· importance of the cow as the chief vehicle of spread of scarlet fever had been established.
Nevertheless, on page 35 Wilson ( 194 2) states "there is at present some doubt as to which is the commoner method of infection" (i.e. cow or man); so it seems necessary to
clarify the position further. In connection with milk-borne - dipther ia -
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diptheria Topley and Wilson (1936) state that diptheria bacilli are rarely ioolated from milk that is actually causing a milk-borne epidemic, because contamination from the hwnan carrier is such a chance occurrence that gross spoilage of the milk could only occur, if the diptheria bacillus could.multiplf in milk under ordinary conditions of storage. Applying this dictum to the scarlet fever problem, it is reaoonable to argue that if the cow plays no major role in the spread of S)arlet fever, then extensive
and prolonged epidemics such as those described by Capps
& Miller (1912), with 10,000 patients, and by Wilkensen (1931) with 1,000 patients, could only occur if Strep.
pyogen es could multiply rapidly in milk. This point was fully investigated by Pullinger & Kemp (1937), and a clear- cut conclusion was reached that this organism does not mul- tiply under normal conditions of storage. The only re- maining explanation of extensive epidemics is that cows can become infec"te d with Strep. pyogenes, and can excrete organisms in the milk. Since such excretion has been demonstrated on frequent occasions, and since counts of
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streptococci up to 25 (vide Brown & Orcutt 1920) have been recorded, the writer cannot see where room for doubt exists in regard to the importance ·of the role played by the cow. The main point is that, in the case of every milk-borne epidemic of scarlet fever, immediate sear8h
should be made for a carrier cow. The fact that the cow originally was infected by a human carrier is incidental, for Bendixen & Minett ( 1939) recorded the case of a cON which remained infected for 13 months, including a dry
period of 3 months. It must not, however, be thought that the human carrier is a negligible factor. Outbreaks
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recorded by Henningsen & Ernst (1939) and by Stebbins et alia are clear cut examples of contamination by milk handlers, whilst the work of Pullinger & Kemp (1937) showed that multiplication of streptococci might easily occur, if a milk-handler contaminated pasteurised milk,
an example of such an outbreak being given in Report (l938c).