Carriers

CARRIERS. Normally when an individual recovers from an infective disease he rids himself of the causal organisms so that when he is convalescent or recovered he ceases to be infective. It has been found that a certain proportion of individuals, however, do not rid themselves of the disease-causing germs, but retain them for varying periods of time. These persons—termed carriers —have recovered completely from the disease and are apparently healthy. They exhibit no signs of infection whatsoever, and, al though the bacteria are tolerated by the carriers harbouring them, the germs are capable of giving rise to disease in susceptible in dividuals.

The first direct evidence of the existence of carriers was brought forward by Dr. Robert Koch in 1902, who showed that in typhoid fever the convalescent patient harbours the specific germ and is the most fruitful source of further infection.

The existence of urinary carriers had previously been shown by Horton Smith in England in 19oo, while repeated outbreaks of typhoid fever in Folkestone, due to contaminated milk, were described by Dr. Theodore Thomson in 1901. In these epidemics it was noticed that a certain milker had worked on the three dif ferent farms associated with the outbreaks of enteric fever in the years 1896, 1897 and 1899. The importance of this observation was not realized until the work of Koch appeared, when it was found that this milker constantly excreted large numbers of ty phoid germs.

A certain number of individuals may harbour pathogenic or disease-causing organisms during convalescence, but these bacteria rapidly disappear, and the case is termed a temporary carrier. If pathogenic organisms persist for more than three months, the individual is termed a chronic carrier.

The following diseases are maintained and spread by carriers: typhoid and paratyphoid fevers, bacillary and amoebic dysentery, cholera, diphtheria, cerebrospinal meningitis, scarlet fever, an terior poliomyelitis (infantile paralysis), malaria. (See MALARIA.) Typhoid and Paratyphoid Carriers.—The carrier state is much more common in women than in men. Carriers may be (a) faecal; (b) urinary. In faecal carriers the typhoid germs remain in the upper part of the alimentary tract, and particularly in the gall bladder whence they reach the intestine in the bile. These carriers are very liable to periodic attacks of inflammation of the gall bladder and to gall stones. Typhoid bacilli may appear only intermittently in the excreta so that at times a carrier is infective.

Typhoid and paratyphoid carriers are usually very chronic and may harbour the organisms for many years or even a lifetime. The diseases are spread by the direct contamination of food or water-supply with the specific germ due to the uncleanliness of the carrier. That typhoid is much less common than previously is due to the great improvement in sanitation and provision of pure water-supplies, and the detection and isolation of carriers.

Treatment.

The typhoid carrier presents a difficult problem to the health authorities. The carrier must be isolated, must ob serve rigorous personal cleanliness, and not have anything to do with the preparation of food. Treatment is of little avail, although removal of the gall bladder, particularly when it contains gall stones, brings about the disappearance of the typhoid germs in a number of cases, but even this is often ineffectual. Urinary car riers show no response to treatment and these are more dangerous than faecal carriers owing to the greater difficulty of strict clean liness and disinfection. Some carriers show spontaneous cure.

Dysenteey.

In bacillary dysentery the organisms persist in the lower part of the intestine. They are excreted intermittently as a rule and may only be found when the carrier has a mild dysenteric attack. In amoebic dysentery carriers the parasites pass into a resistant resting state termed cysts. These cysts do not multiply but remain quiescent until they are carried by food or water into the intestinal canal of another individual, when the actively growing stage is resumed with the resultant attack of dysentery. Treatment of amoebic dysentery carriers with emetine is usually effective.

Cholera.

The cholera germ persists in the upper part of the intestine and in the gall bladder, and the condition is similar to the typhoid carrier. The germs are excreted from the bowel only, and food or water is infected as in typhoid. The treatment of cholera carriers is similar to that for typhoid carriers, and as fre quently disappointing.

Diphtheria.

In this disease the germs are present in the throat and nose, and infection is spread direct from one throat to another, either in talking, sneezing, etc., or by contamination of drinking vessels. In diphtheria, carriers are not so persistent as in typhoid fever, and usually become free of infection within a year or two, although in some cases the diphtheria organisms may persist for a long time. Young children are more likely to become carriers than adults. In the throat the germs are found in the tonsils, while in the nose they are associated with a chronic inflammatory condition.

When diphtheria bacilli are found in the nose or throat of a sup posed carrier, it is necessary to test the organisms bacteriologically to prove that they are capable of causing disease. It has been shown that about 9% of all cases of diphtheria become carriers. Usually the carriers are in good health and show nothing abnormal beyond a tendency to nasal catarrh. Outbreaks of diphtheria occur where many persons are congregated together as in schools, institutions, camps, barracks, etc., and the duty of the health authorities is to examine bacteriologically the nose and throat of all contacts in order to discover and isolate the carrier.

In fever hospitals all recovered cases are carefully examined by bacteriological methods for diphtheria bacilli, and cases are not discharged until all virulent germs have disappeared.

found the carrier must be segregated. There is a tendency to spontaneous cure. ' When the germs are present in the throat removal of the tonsils usually brings about a cure, but when the nose is infected this treatment has no effect. Nasal carriers are very refractory to treatment, but recently it has been found that nasal douching with a mild alkaline fluid, and the administration of autogenous vaccines frequently bring about a rapid disappearance of the diphtheria organisms.

Cerebrospinal Fever.

As in diphtheria the germs of the disease—meningococci—are found in the throat, and direct in fection takes place through talking, sneezing, etc., particularly where many individuals are congregated together as in schools, camps, etc. Not every person infected, however, takes the disease, but the meningococci may multiply in the throat and be trans mitted to a third person who may either contract the disease or transmit the infection to others. Thus, where an outbreak of cerebrospinal fever has taken place many healthy persons may have meningococci in the throat, but comparatively few may take the disease. The germs in the throat of the healthy persons usually do not persist more than a very short time and disappear spon taneously. Chronic carriers do occur and the germs may be found over long periods. Gargles and sprays with antiseptic materials often cure the carrier condition.

Scarlet Fever.

It has recently been shown that scarlet fever is due to a haemolytic streptococcus. Patients recovered from scarlet fever may still contain these streptococci in their throats and it appears that scarlet fever is spread by these carriers in a similar manner to diphtheria. Up to the present, however, the examination of convalescent scarlet fever patients before dis charge is not done as a routine as in the case of diphtheria. Gar gles and antiseptic sprays of the nose and throat tend to shorten the period during which streptococci may be found.

Anterior Poliomyelitis (Infantile Paralysis).

It has been shown that during an epidemic of this disease the infective virus may be present in the throats of healthy contacts.

(J. E. M.)