Go to National Library of New Zealand Te Puna Mātauranga o Aotearoa
Volume 73, 1943-44
Previous Article | Table of Contents | Next Article
This text is also available in PDF
(800 KB) Opens in new window
– 239 –

Studies on the Entozoa of Man in New Zealand.*
Part 1.—A Preliminary Note on the Results from the Examination of Inmates of a Mental Hospital.

By L. R. Richardson, M.Sc., Phd.; A. Elizabeth Clark, B.A., M.Sc.; and Patricia M. Ralph, M.Sc.
Department of Biology, Victoria University College.

[Read before Wellington Branch, October 27, 1943; received by the Editor, October 2, 1943; issued separately, December, 1943.]

These studies have been commenced with a view to determining the nature of the intestinal fauna of man in New Zealand. We present in this initial paper the data from the examination of stools of individuals selected at random from the inmates of a mental hospital in the North Island. The work of Dobel, Matthews and Smith, Boeck and Stiles, Bach, Svensson, and others have clearly established the fact that institutional life favours the dissemination of entozoa, and that in consequence of difficulties in personal hygiene the incidence of entozoa is commonly higher in mental hospitals than in other institutions or in the general community. A mental hospital is accordingly a good starting point for such studies as the present, and we are deeply indebted to Dr T. G. Gray, Director-General of the Mental Hospitals Department, and to Dr B. D. Hart, Medical Superintendent of the Porirua Mental Hospital, for the many facilities which they have so freely extended to us, and to Dr R. W. Medlicott, Medical Officer of the Porirua Mental Hospital, for his kindly interest, which has been invaluable.

The data obtained from the study of a single sample from each of 100 individuals form the basis of this report. Slightly more than half of the specimens were examined fresh, and the rest examined after preservation in 5 per cent. formalin. A minimum of three cover-slip preparations, when possible each from a different part of the sample, has been taken as the standard, though additional preparations are made when required, and in most cases four preparations have been examined. Each cover-slip is prepared to the optimum reading density as defined by Boeck and Stiles (1923), and Gram's iodine solution employed for differentiation; but saline, acidulated methyl green, and iron haematoxylin preparations are also put up when needed. The reading of the individual cover-slip averages fifteen minutes, and approximately 225 separate fields are examined in each preparation.

The incidence recorded for each of the species cannot be considered as the actual incidence of the entozoan in the group. The cyclical nature of egg-laying and of cyst-formation, and the probabilities of locating eggs or cysts in the small quantity of material which can be examined are both factors which enable infestations to escape detection. However, the examination of a single stool

[Footnote] * This paper has been published through a grant from the Publications Fund of Victoria University College.

– 240 –

has been a common standard in survey work. We have retained this standard, and our findings are reasonably comparable with those of Matthews and Smith (1919), Boeck and Stiles (1923), Meleney, Bishop and Leathers (1932), and others. Although the number of individuals in the group is small, random sampling has yielded a group of 44 individuals faulty or faulty at times in their habits, and a group of 56 individuals of normal behaviour in regard to their personal hygiene. It may be pointed out that this is not cross-sectional of the hospital community.

Species Determined.

Entamoeba histolytica Schaudinn.

Cysts of this protozoan were observed in the stools from 15 individuals, and trophozoites were found in three fresh samples. These 18 records were equally divided between the faulty and the normal groups, the incidence being 20.5 per cent. in the former and 16.2 per cent. in the latter, with a total incidence of 18 per cent. Matthews and Smith (1919) recorded E. histolytica in 9.7 per cent. of 207 patients in an English mental hospital; Boeck and Stiles (1923), 6.1 per cent. in 1182 individuals examined on an average of 3.2 times each, and 15 per cent. in 505 individuals examined six times each, all inmates of a mental hospital in the District of Columbia; Bach (1932), 14.83 per cent. in a mental hospital in north-west Germany; and Reardon has recently (1941) recorded as high as 44 per cent. infestation with E. histolytica in a small group of the inmates of the State Hospital, Georgia, U.S.A. Fortunately it appears that strains of E. histolytica in mental hospitals are in general of low virulence, and the presence of this species is of minor significance excepting in the case of the occasional individual of low tolerance, or of the entry of a strain of E. histolytica of higher than usual virulence. Barcelos (1940) has given an account of the tragic possibilities of the latter occurrence in the case of a children's institution. In the present study, infestations with E. histolytica were found in all age-groups and in individuals of long-standing as well as of recent admission to the hospital community. Two individuals examined within a fortnight of their admission showed infestations of a chronic nature. The cysts observed ranged in size from 8 microns to 12 microns in diameter, were typical in appearance, and many examples showed clearly the nuclear morphology characteristic of the species.

Entamoeba coli (Lösch).

This very common entozoan of man was identified by the presence of cysts in 16 stools (36.2 per cent.) from faulty individuals, and in 18 stools (32.2 per cent.) from the group of individuals normal in their habits. The incidence of 34 per cent. for the entire group studied ranks this as the most common species encountered. The incidence is nevertheless lower than that recorded by Young and Ham (1941), who determined an infestation of 48 per cent. in a selected group of 142 mental cases at the South Carolina State Hospital; or Miller (1939), who recorded an infestation of 45 per cent. of the inmates of a children's institution in midwestern Canada. It is similar to that recorded by Boeck and Stiles

– 241 –

(1923) of 35.5 per cent. for their series of 1182 mental hospital inmates, but lower than their figure of 61 per cent. in their series of 505 cases. The species was recorded in all age-groups, and as in the case of E. histolytica was found in recent admissions as well as in inmates of long standing in the community. The cysts observed ranged in diameter from 14 microns to 22 microns, were generally spheroidal, although in several stools up to 50 per cent. of the cysts observed were ovoidal, and in one case two sub-cylindrical cysts were found. The majority of infestations were of the medium and large races, ranging from 16 microns to 22 microns. In one stool, both the large and the small races of E. coli were present along with an infestation by the medium race of E. histolytica. E. coli was found commonly in the stools of individuals admitted more than 12 months before examination.

Endolimax nana (Wenyon and O'Connor)

Characteristic cysts of this common commensal amoeboid protozoan were found in stools of two individuals of the faulty group. This total incidence of only 2 per cent. is undoubtedly correlated with the nature of the routine technique employed. The cysts of this species are small, usually only 8 microns to 10 microns in diameter and differentiate poorly with simple iodine preparation. Faust and his associates (1939) have shown that the examination of haematoxylin stained films will reveal 60 per cent. more positives for this species than any other technique; but such films prepared from formalinised material are too variable for consistent results, and we could not make this a routine part of our technique. The actual incidence might normally be anticipated to be between 17 per cent. and 24 per cent.

Iodamoeba butschli (Prowazek).

Cysts of this species were observed in one stool (2.25 per cent.) of the faulty group, and three stools (5.35 per cent.) of individuals of the normal group. This total incidence of 4 per cent. is similar to that of 5.4 per cent. determined as the incidence among 1182 mental hospital cases by Boeck and Stiles (1923), and to that of 6 per cent. recorded by Miller (1939) among the inmates of a children's institute. It is almost half the incidence of 9 per cent. determined by Young and Ham (1941) for their selected group of 142 mental hospital inmates of untidy habits. Few cysts were observed in any of the positive preparations. The cysts were subspherical to ovoidal in shape, ranging from 9 microns to 15 microns on the longer axis, but showed clearly in all cases the peculiar nuclear morphology characteristic of the species. It is quite possible that formalin preservation is not favorable for the cysts of this species, as the present records are with one exception from stools examined fresh.

Giardia intestinalis (Lambl).

Infestations with this flagellate were found in five cases, in three individuals (6.8 per cent.) of the faulty group, and two (3.57 per cent.) of the normal group. The former were young, less than twenty years of age; the latter were in their third and fifth decades. One individual had been admitted less than two months before

– 242 –

examination. In the individuals of the faulty group, large numbers of cysts were being passed. There is a marked age correlation for the determined incidence of this species (Meleney, Bishop, and Leathers, 1932). The incidence of infestation rises to a peak of 25 per cent. between the ages of two and seven years, falls to a minimum of 2.5 per cent. at thirty years, and is maintained near this level in the subsequent age-groups. Miller's (1939) figure of 19 per cent. is high and related to the lower average age of the group he studied. Matthews and Smith (1919) determined an incidence of 3.4 per cent. in mental hospital patients, a figure similar to that of Boeck and Stiles (1923), who record an incidence of 3.1 per cent. for their entire group and of 15.4 per cent. in their group of 505 patients examined six times each. Young and Ham (1941) record an incidence of 6 per cent. in the select group examined by them. The incidence of 5 per cent. recorded here for the whole group agrees well with that of studies elsewhere, and the incidence of 6.8 per cent. for individuals of the faulty group agrees well with that determined by Young and Ham. The cysts observed showed little variation, being mostly 10 microns to 12 microns in length and 6 microns to 8 microns in width. The axostyles and parabasal bodies characteristic of this species in stools from humans were clearly evident.

Trichomonas hominis (Davaine).

The absence of cyst-formation from the life-history of this species limits the detection of Trichomonas infestations to the examination of fresh stools. Many of the fresh specimens examined by us were dry, indurated and unsuitable from the view point of the detection of this species, however in three cases—two of the faulty group (4.5 per cent.), one of the normal group (1.78 per cent.)—this species was observed. The total incidence of 3 per cent. is similar to that of other studies carried out in the present manner; but from the limiting factor mentioned above it is obvious that the results are generally lower than the actual incidence in any group studied.

Chilomastix mesnili (Wenyon).

This species is recorded here on the basis of cysts observed in the stool from one individual of the faulty group. The incidence is exceptionally low and we have no explanation of this since the cysts of this species preserve well and differentiate readily with iodine.

Enterobius vermicularis (Linn.).

Pinworm infestations were recorded in five (11.18 per cent.) of the individuals of faulty habits, and two (3.57 per cent.) of the individuals of normal habits. This total incidence of 7 per cent. is close to that determined by Boeck and Stiles (1923) for their entire group of 1182 inmates of a mental hospital in the District of Columbia, viz., 5.8 per cent. on the basis of an average of 3.2 examinations per person. It contrasts with the negative findings reported for this species by Young and Ham (1941). Reardon (1941) reports 69 per cent. infestation with E. vermicularis in the small group which she examined, but this is the result of examinations by N. I. H. swabs. The present records and those of earlier

– 243 –

surveys are based entirely on simple stool examinations which as is well recognised do not reveal the actual incidence of the species (Sawitz, et al., J. Parasit. Suppl., 1938, No. 9); but for our purposes the results of such survey work are comparable.

Trichuris trichiura (Linn.).

In the group reported on, the whipworm ranks second to E. coli in frequency having in this series a total incidence of 27 per cent. Infestations were recorded in 20 individuals (45.5 per cent.) of the faulty group and seven (12.5 per cent.) of the normal group. Boeck and Stiles (1923) using practically the present technique revealed 50 per cent. of the actual incidence of T. trichiura by the examination of a single stool of each of the individuals in their series of 505 cases ultimately examined six times each. On this basis our figure for the observed incidence of this species in the faulty group indicates a situation approximating to that of the 78 per cent. incidence determined by Young and Ham (1941) in their selected group of 142 patients of untidy habits, and the probable incidence of 54 per cent. for the entire group approximates to the incidence of 61 per cent. to 65 per cent. recorded by Reardon (1941); but in view of the warning given by Svensson and Linders (1934), it is inadvisable to use calculated demonstrabilities in estimating actually existing infestations. In the present study, T. trichiura infestations were detected in all age-groups. The eggs observed fall within the limits of this species, and none were found which might have been assigned to T. ovis or to the other species of the genus which are common in the domesticated animals of this country.

Other Forms Observed.

We note here briefly the occurrence of the vegetable organism Blastocystis hominis which was present in 18 (40.9 per cent.) of the faulty group, and 15 (26.7 per cent.) of the normal group. The total incidence is similar to that of 24.7 per cent. determined by Boeck and Stiles (1923) and others for such communities. Phycomycete spores were observed commonly, but no records were kept. Intestinal yeasts were present in all stools.

Multiple Infestations.

Infestations with more than one species of entozoan were recorded in 15 of the faulty group and eight of the normal group, in other words 32 per cent. of the infestations were multiple in nature. Fifteen were cases of double infestation as follows:

E. histolytica + E. coli 4
E. histolytica + G. intestinalis 2
E. coli + I. bütschli 1
E. coli + G. intestinalis 1
E. coli + T. trichiura 6
E. vermicularis + T. trichiura 1
Six were cases of triple infestation:
E. histolytica + E. coli + T. trichiura 2
E. coli + T. hominis + T. trichiura 1
E. coli + G. intestinalis + T. trichiura 1
E. coli + E. vermicularis + T. trichiura 1
E. nana + E. vermicularis + T. trichiura 1
– 244 –

and two were quadruple infestations as follows:

E. histolytica + E. coli + T. hominis + T. trichiura 1
I. bütschli + C. mesnili + E. vermicularis + T. trichiura 1

There were seven double infestations and one triple infestation in the normal group, and eight double, five triple, and two quadruple infestations in the faulty group.

Discussion.

The species recorded above possess in common the direct type of life-history. Involving only a single host, auto-infection is a possibility and a contributing factor in the maintenance of untreated infestations throughout long periods in the life of the host. Such sustained infestations survive long journeys and distance is no barrier in the dispersal of these entozoa, which are now cosmopolitan. On the other hand, in the absence of such complications as intermediate obligatory hosts and of free extra-human existence, these entozoa perform their simple life-histories independent of climatic conditions and influenced principally by the sanitary conditions and behaviour of the host.

The 100 individuals examined have been assigned to the categories of faulty or faulty at times, and normal with regard to their personal hygiene. The selection for examination was made at random, and has produced a group of forty-four individuals in the first category, and fifty-six in the second. The groups are not fully equivalent. The normal group is more heavily weighted in the age range of twenty to fifty years which includes forty-one individuals, contrasted with the faulty group which has only eighteen individuals in the same age range. Meleney, Bishop and Leathers (1932) have demonstrated the correlations of age and incidence of entozoan infestations, and the more even distribution of individuals by age in the faulty category might be expected to limit the comparison of the two lots; but such restrictions are greatly curtailed by the auto-infective nature of the organisms, the implications of breaks in personal hygiene, and other factors discussed later.

The data presented above serve to demonstrate the similarity between the entozoal fauna of the group studied and that of the same type of communities in other parts of the world. The occurrence of entozoa in 70 per-cent. of the persons examined by us is quite comparable with the findings of Boeck and Stiles (1923), who reported that 79 per cent. of a group of 505 persons, inmates of a mental hospital in the District of Washington, were infested with entozoa, although it is less than that reported by Young and Ham (1941), who examined a select group of 142 persons of untidy habits and found 90 per cent. infested. Infestations with protozoa, alone and in combination with helminths, were detected in 55 per cent. of the persons examined in the present study. This figure agrees well with the protozoan incidence of 52.15 per cent. reported by Bach (1932) from the examination of inmates of a mental hospital in north-west Germany. It indicates a situation similar to that of the 65 per cent. infestation by protozoa reported by Young and Ham (1941); but where the latter found 82 per cent. of the persons

– 245 –

in the selected group which they studied positive for helminths, we have been able to determine only a 30 per cent. incidence of helminths in the whole group, a figure which is low and even low in comparison with this when the faulty group in which we found 50 per cent. positive for helminths is considered alone. This is quite likely a consequence of the simple direct technique which we have employed as a basic routine without recourse to concentration techniques.

The iodine-stained wet-preparation employed in the present work has been adopted as the standard on the basis of its broad general utility. The use of stained films, concentration techniques and other aids to greater efficiency in the determination of entozoa are not generally applicable with varying conditions of material or working quarters. The present technique can be employed equally on preserved or fresh material with a fairly constant relative efficiency. Accordingly, this technique has been chosen as the basic routine, although as shown by Faust and his associates (1939) in their studies on the comparative efficiency of various techniques, the saline and iodine wet-preparations have an efficiency of only 41 per cent. for entozoa generally, and detect only 33 per cent. of E. histolytica, 55 per cent. of E. coli, 62 per cent. of G. intestinalis, 6 per cent. of T. trichiura, etc., when two cover-slips are examined and ten minutes allowed for the examination. It is apparent from the incidence recorded for the several species determined by us that we have been able to achieve a better efficiency with this technique. This is the result of the considerable period of time allotted to the examination of each sample.

Comparison between the infestations of the normal and of the faulty groups is of particular interest. We have been unable to find, in previous accounts, any distinction drawn between the infestations observed in various groups in mental hospitals. In the present work, the total infestation by protozoa, including all records of infestations both alone and in combination with helminths, is closely similar for the two groups, the incidence being 54.4 per cent. for the forty-four members of the faulty group, and 55.4 per cent. for the fifty-six members of the normal group. The total helminth incidence is in striking contrast to this. Infestations with helminths were recorded in 50 per cent. of the members of the faulty group, alone and in combination with protozoa, while only 14.2 per cent. of the members of the normal group were positive for helminths. Clearly in these figures there is a relationship between personal cleanliness and helminth infestation; but equally clearly, the incidences recorded reveal no correlation between personal behaviour and protozoan infestation. There is a strong indication in these figures that although the life-cycles of these entozoa have a common pattern, a factor is operating which enables the protozoa to achieve more successes than do the helminths. There is, of course, the possibility that helminth infestations run their course more rapidly than do protozoan, but it seems unlikely that this has brought about the present situation in view of the persistent possibilities for reinfestation. It seems more probable that some route is open for the dissemination of protozoa, but closed to the helminths.

– 246 –

Infested food-handlers have been commonly considered as potential factors in the distribution of protozoa. Sapero and Johnson (1939) have pointed out in this connection that they have been unable to determine significant differences between the incidence of E. histolytica in groups which contact, and others which do not contact food-handling carriers of this entozoan, nor does the food-handler seem a likely element in this case unless negative for helminths. The possibility of dust-borne infestations has been shown by Porter (1928), and of water-borne infestations by several workers (e.g. Hardy and Specter, 1935). Both of these routes would serve as a common entry to the whole community, but are also available for helminths, as has been shown by Porter, by Nolan and Reardon (1939), and others. In explanation of this common incidence in the two groups it seems necessary to assume some factor of a nonpersonal nature freely favouring the dissemination of protozoa but unsuitable for the transmission of helminths. The insect vector suits these three primary requirements. It has strictly limited powers to tranmit helminth infestations by external carriage; but possesses, as shown by Frye and Meleney (1932) and reaffirmed by Pipkin (1942), definite ability to transmit protozoan infestations by both external and internal carriage. At this stage we feel unable to do more than indicate the nature of the problem.

Summary.

The incidence of entozoa in 100 inmates of a North Island mental hospital has been determined on the basis of the examination of a single stool from each individual. The species recorded and their incidence for the entire group are: Entamœba histolytica, 18%; Entamœba coli, 34%; Endolimax nana, 2%; Iodamœba bütschli, 4%; Giardia intestinalis, 5%; Trichomonas hominis, 3%; Chilomastix mesnili, 1%; Enterobius vermicularis, 7%; Trichuris trichiura, 27%; and the vegetable organism, Blastocystis hominis, 33%; Negative findings were recorded in 30%. Total incidence of protozoan infestations, 55%; of helminths, 30%. The incidence of entozoa generally and of the various individual species is compared with findings from studies of similar institutional populations in North America, Europe and elsewhere, and it is shown that the nature of the intestinal fauna is, in general, similar.

The group consisted of 44 individuals of faulty habits, and 56 of normal behaviour in regard to their personal hygiene. Protozoan infestations were recorded in 54.4% of the former, and 55.4% of the latter. A striking contrast was recorded for helminth infestations, the faulty group being 50% infested; and the normal group, 14.2% positive for helminths. This is interpreted as indicating that personal cleanliness is an effective factor in preventing or reducing helminth infestation, but only a secondary factor in the problem of protozoal infestations. It is suggested that there is a common agency active leading to general infestation with protozoa, and not available to helminths. It is suggested that the insect vector may provide this agency.

– 247 –

Literature Cited.

[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]

Bach, F. W., 1932. Untersuchungen über die Verbreitung parasitischer Darmprotozoen des Menschen, insbesondere Entamoeba histolytica, in nordwest Deutschland. Zeitschr. Hgy. u. Infektionskrank. 113 (2/3): 321–344.

Barcelos, V. F., 1940. An Outbreak of Amoebic Dysentery. Arq. Hig. (R. de Janeiro), 10 (1): 109–126.

Boeck, William C. and Stiles, Ch. Wahdell, 1923. Studies on Various Intestinal Parasites (Especially Amoebae) of Man. U.S. Publ. Health Service, Hygienic Lab. Bull. no. 133: iii-xxvi, 1–202.

Faust, E. C.; Sawitz, W.; Tobie, J.; Odom, V.; Peres, C.; and Lincicome, D. R., 1939. Comparative Efficiency of Various Technics for the Diagnosis of Protozoa and Helminths in Feces. J. Parasit, 25 (3): 241–262.

Frye, W. W. and Meleney, H. E., 1932. Investigations of Endamoeba histolytica and Other Intestinal Protozoa in Tennessee. iv. A Study of Flies, Rats, Mice and Some Domestic Animals as Possible Carriers of the Intestinal Protozoa of Man in Rural Communities. Am. Journ. Hyg., xvi (3): 729–749.

Hardy, A. V. and Spector, Bertha K., 1936. The Occurrence of Infestations with E. histolytica, Associated with Water-borne Epidemic Disease. U.S. Public Health Kept., 50 (10): 323–334.

Matthews, J. R. and Smith, A. Malins, 1919. The Spread and Incidence of Intestinal Protozoal Infections In the Population of Great Britain. iv. Asylum Patients. v. University and School Cadets. Ann. Trop. Med. and Parasit. 13 (1): 91–94.

Meleney, H. E.; Bishop, E. L.; and Leathers, W. S., 1932. Investigations of Endamoeba histolytica and Other Intestinal Protozoa in Tennessee. iii. A State-wide Survey of the Intestinal Protozoa of Man. Am. Journ. Hyg., xvi (2): 523–539.

Miller, M. J., 1939. The Intestinal Protozoa of Man in Mid-Western Canada. J. Parasit., 25 (4): 355–357.

Nolan, M. O. and Reardon, Lucy, 1939. Studies on Oxyuriasis, xx. The Distribution of the Ova of Enterobius vermicularis in Household Dust. J. Parasit., 25 (2): 173–177.

Pipkin, A. C., 1942. Filth Flies as Transmitters of Endamoeba histolytica. Proo. Soc. Exp. Biol. and Med., 49 (1): 46–48.

Porter, Annie, 1928. Notes on the Distribution of Animal Parasites in Street Dust Examined in Johannesburg from 1923–1928. Journ. Med. Assoc. S. Africa, 2 (21): 571–577.

Reardon, Lucy V., 1941, Incidence of Endamoeba histolytica and Intestinal Nematodes in a Georgia State Institution. J. Parasit., 27 (1): 89–90.

Sapero, J. J. and Johnson, C. M., 1939. An Evaluation of the Role of the Food-handler in the Transmission of Amebiasis. Am. Journ. Trop. Med., 19 (3): 255–264.

Svensson, Ruth and Linders, F. J., 1934. The Chances of Detecting Infections With Intestinal Protozoa. A Parasitological and Statistical Study. Acta. Med. Scand., 81 (¾): 267–324.

Young, Martin D. and Ham, Coyt., 1941. The Incidence of Intestinal Parasites in a Selected Group at a Mental Hospital. J. Parasit., 27 (1): 71–74.

Previous Article | Table of Contents | Next Article