The American Journal of Tropical Medicine and Hygiene - Volume 6, Issue 1, January 1957

The term “sanitary engineering,” like “preventive medicine” and others which pertain to both scientific fields of activity and professional practice, may be employed either in a strictly professional sense or in a generic sense. As a determinant of the metes and bounds of this article, “sanitary engineering” is interpreted as encompassing both the professional and the generic aspects, without attempting to draw any fine lines of distinction between the problems, interests and activities of professional engineers on the one hand and non-engineers on the other. In the large, difficult and complex task of controlling the tropical environment in the interest of man's health and welfare, there is obvious room for contributions by many arts and skills. Appraisal of these problems and of their indicated solutions can only be confused by efforts to subdivide them into respective professional packages.

There is one important exception. Sanitation is thought of as a basic part of or within public health.

A seven-day dietary survey of a random sample of twenty households and twelve post-weaning children in the Santa Cruz area of Bolivia showed generally low intake of calcium, riboflavin, thiamine and vitamin A. Calories and the remaining nutrients for which calculations were made, i.e., protein, iron, and ascorbic acid, were also low in some cases. Diets of farm labor households tended to be lower in nutrient content than those of farm-owner and urban households. Diets of the post-weaning children, ranging in age from one to four years, compared less favorably with recommended allowances than did those of households. Rice, yuca, refined bread, coffee, sugar, and varying amounts of meat constituted the major portion of all diets. A few families ate vegetables and fruits in addition, and some used very small amounts of milk. A program of home food production and possible changes in food preparation and buying practices are suggested as ways of improving dietaries.

The pathogenicity of 37 strains of E. histolytica, isolated from human patients and carriers, was studied in white rabbits. Five of these strains (Group 1) consistently produced severe ulceration in 88.4 per cent of the rabbits inoculated, with crater-like lesions, intense diarrhea, marked loss of weight and huge numbers of trophozoites containing red blood cells. Four of the 5 patients from whom these strains were isolated suffered from amebic dysentery. Group 2, comprising 14 strains, was mildly pathogenic producing only small lesions in 45.2 per cent of the rabbits inoculated, which lost little weight. Two of the patients furnishing these strains had amebic liver abscesses with few or no intestinal symptoms; the rest were asymptomatic. The 18 strains of Group 3, secured from asymptomatic carriers, were also nonpathogenic to rabbits.

The trophozoites of all the highly virulent strains of Group 1 were larger than 10 microns, but there were also large amebae in Group 3; none of the strains measuring less than 10 microns (size of trophozoites in culture) produced macroscopic evidence of lesions in rabbits. Amebae multiplying in ulcers were invariably larger than those in the cultures from which they were derived, but reverted to their former size when cultures were made from the lesions.

The lesions in infected rabbits showed only occasional infiltration by lymphocytes and plasma cells, but in all but 4 of the 36 animals examined there was a characteristic invasion of eosinophils which are believed to correspond to the neutrophils of man.

After oral administration to human subjects, pyrimethamine could be detected chemically and microbiologically for seven days in the serum and for eleven days in the urine. Urinary excretion during the first five days accounted for about twelve per cent of the dose administered. The excretion patterns of materials measured by chemical and microbiological procedures were similar, an observation which speaks against conversion of the parent drug to a metabolite possessing greater anti-folic acid activity.

When administered orally to monkeys, pyrimethamine could be detected for at least five days in the serum and seven days in the urine. Urinary recovery in this period ranged from twenty to forty per cent by chemical determination and from ten to thirty per cent by microbiological assay. Chemically determinable pyrimethamine in both serum and urine was always greater than that measured microbiologically indicating that in the monkey pyrimethamine is converted to a metabolite which has less anti-folic activity than the parent compound.

The “anti-folic acid” activity in urine of human subjects and monkeys receiving pyrimethamine behaved chemically like the parent drug. Evidence for the presence of non-basic pyrimethamine metabolite(s) possessing a higher order of anti-folic activity than the parent compound was not obtained.

Correlation of these findings with earlier observations on the antimalarial activity of pyrimethamine suggests that the prolonged suppressive activity of this compound against infections with Plasmodium vivax in man and P. cynomolgi in the rhesus monkey is due to retention of the parent compound.

Studies by electron microscopy of allantoic-amniotic fluid from embryonating chicken eggs infected with Sindbis virus show the virus to be spherical in shape with a diameter between 45 mu and 55 mu. These bodies could not be demonstrated in concentrated suspensions of normal filtered allantoic-amniotic fluid. Neutralization tests confirmed the virus to be Sinbis tropical virus.

This preliminary study was designed to determine the prevalence of Salmonella and Shigella in human population groups without reference to the presence or absence of frank diarrheal disease. Twelve communities in Guatemala were selected for study, and children 0–10 years of age examined by means of rectal swabs. Data on the external environment were obtained by observation and by compilation of locally available statistics.

The high prevalence rates for Shigella were shown to be comparable with rates obtained in selected specific areas of the United States during periods when Shigella infection was determined to be the major cause of diarrheal disease deaths. Although not all of the diarrheal problems in Guatemala are related to shigellosis, the data strongly suggest that organisms of the genus Shigella cause the major portion of diarrheal diseases in the communities studied in Guatemala and that diarrheal diseases caused by Shigella represent a major public health problem in the country.

The high rates in Guatemala, as in the United States, were associated with the lack of sanitary facilities, with poor housing, with limited water supply and with poor personal hygiene.

The incidence of relapse in typhoid fever treated with chloramphenicol is dependent on the period of time during which therapy is continued. Where this is less than about seven days very high relapse rates may be experienced. The relapse state is probably initiated by intracellular forms of S. typhi present in reticuloendothelial cells. It is suggested that chloramphenicol promotes phagocytosis of viable organisms and that this creates a reservoir of tissue forms of the organism which is responsible for the high relapse rates in those patients who are inadequately treated.

Two of the fungi, Trichophyton mentagrophytes and Microsporum gypseum which cause ringworm in man infect many domestic and wild animals in nature. Most of the human cases of T. mentagrophytes in rural areas are presumed to be of animal origin, but M. gypseum infections are believed to be acquired more often from soil contacts.

Commensal rats were collected from rural premises in four counties of south-western Georgia and their hairs were tested for ringworm. Approximately 5 per cent of the 350 Norway rats and 7 per cent of the 84 roof rats trapped had ring-worm infections as shown by culture methods. Only Norway rats were caught in Mitchell County and none of 150 specimens were found infected. Rats positive to T. mentagrophytes came only from Grady and Thomas Counties. Two Norway rats from the 35 trapped in Baker County showed the presence of M. gypseum. The degree of rat infestation of premises as indicated by success in trapping was directly related to the percentages of premises with ringworm-positive rats. An inverse relationship between the degrees of rat infestation of premises and percentages of rats infected by ringworm was indicated by the limited data considered.

Twenty-eight soil samples taken from rat ranges on six premises where ring-worm-positive rats were trapped showed the presence of M. gypseum only, over half of the samples containing this primarily saprophytic fungus.

Three cases of isosporiasis in native-born Tennesseans who have never been abroad are reported. Two of the cases recovered spontaneously; the third, a seventy-seven-year-old white woman, expired with signs of electrolyte imbalance. Necropsy findings showed necrosis of the terminal ileum and colon and a sterile peritonitis. The organisms could not be demonstrated in the tissues.

A modified method for the extraction of ESS from leptospirae has been developed which yields preparations stable for at least 41 weeks at 4°C. ESS antibody apparently deteriorated on storage at -20°C. for more than 1 to 1.5 years. Good correlation between the SEA and the agglutination-lysis tests were obtained with fresh sera. Unsatisfactory results were obtained with sera shipped from Australia. About 8 per cent of sera sent to the Massachusetts Department of Public Health for various diagnostic tests were positive in the SEA test, the significance of which is not ascertained. Different antibodies are responsible for the SEA and the agglutination-lysis reactions.

The leptospiral sensitized erythrocyte lysis test established the diagnosis in all 40 cases of human leptospiroses. The sero-group specificity of the test was substantiated by the ability of L. pomona ESS to detect human infection caused by L. icterohemorrhagiae, L. canicola, L. pomona, L. hyos, L. australis A, L. australis B, “Robinson”, “Kremastos”, and “Celledoni”. The value of the SEL test in survey studies of past leptospiral infection requires further study.

Seventy-four patients with heptaic fibrosis associated with Schistosoma mansoni infection were examined. The intrasplenic pressure measured by the percutaneous method had a direct linear relation with the portal pressure measured directly at operation and by the percutaneous transhepatic method. Hematemesis, esophageal varicosities and venous hum over the abdomen are indications of the level of the portal pressure. The size of the liver and spleen had no constant relation to the portal pressure. Ascites is frequently, but not always, associated with high pressures. Spleno-portal venography used in conjunction with intrasplenic pressure measurement is particularly valuable in diagnosis of portal hypertension and in demonstration of veins suitable for portocaval anatomosis.

An analysis has been made of the composition of the sylvan mosquito fauna of a well developed virgin tropical rain-forest in which yellow fever appeared in 1951. The results are based on two years of collecting mosquitoes attacking human baits on the ground and in the forest canopy, during the daylight and evening hours. The circumstances under which yellow fever occurred are given, and the climate and microclimate of the rain-forest summarized. It is shown that in true rain-forest the vertical stratification of the sylvan mosquito fauna is much more pronounced than in open deciduous forest. The daily activity cycles of 19 species are illustrated, and an analysis made of the regularity of attack in the case of five species known or suspected as sylvan yellow fever vectors. In addition the annual abundance cycles of 19 species are given.

The results are given of forest canopy mosquito surveys at three places in Nicaragua where there was evidence of sylvan yellow fever activity during 1952 and 1953. At these localities five species of Haemagogus were taken: spegazzinii falco, iridicolor, m. mesodentatus, equinus and anastasionis, the last named only on the Pacific slope, and the first three only on the Caribbean slope. H. iridicolor is also present on the Pacific slope in small numbers but was not in the collections made at the two fixed stations operated there. Also present and of interest as possible vectors were Aedes leucocelaenus clarki and Trichoprosopon magnus on the Caribbean side only, and Sabethes chloropterus on both the Caribbean and Pacific versants. On epidemiological grounds H. equinus appears to have been the vector on the Pacific side and H. iridicolor the principal vector on the Caribbean slope. The possible role of S. chloropterus, considered an important species in carrying virus over the dry season in Panama, could not be assessed as the Nicaraguan collections were made only in the rainy season. Also in doubt is the possible part played by Trichoprosopon magnus, the commonest arboreal mosquito at the Caribbean side stations, since its ability to transmit has not yet been determined. It is thought that the numbers of three species known to be vectors elsewhere, H. spegazzinii falco, H. m. mesodentatus and A. leucocelaenus clarki were too small for them to have been significantly involved in transmission.

The DV/D ratio was measured in about three and a half thousand males of pipiens and quinquefasciatus, mostly from North America. It was found that the average ratio in a collection of pipiens is usually 0.1 or less and in quinquefasciatus 0.6 or more. In individual specimens the ratio is usually less than 0.2 in the former and more than 0.4 in the latter. In North America north of 39°N. only pipiens is usually found; south of 36°N. only quinquefasciatus is generally present. Collections from between these latitudes may contain one or the other form, intermediates, or various mixtures of the three. There seems little doubt but that the forms do hybridize in nature. In some localities (Sacramento, Calif.) intermingling seems to be much freer than in others (East St. Louis, Ill.). At the present time it seems wisest to retain subspecific names for the two forms.

A high incidence of infection with T. canis was found in dogs aged 3–6 months. In mature dogs a marked difference in resistance is found between the sexes. Males exhibit little resistance to T. canis as compared to females, whose resistance increases up to the age of 3 years. A pronounced variation in seasonal incidence of T. canis was found in male dogs; the incidence was highest during winter and lowest during summer months. Female dogs showed a fairly uniform seasonal incidence. Evidence is provided in this study to show that in the Midwestern area of the United States Toxocara canis is a common parasite of dogs.

Studies were conducted in 100 privies in the Savannah, Georgia, area from December, 1952, to December, 1953, to determine the species composition of the fly populations produced from this source. More than 175,000 Diptera were collected representing 97 species, 65 genera, and 33 families. Patterns of emergence for individual species of Diptera varied seasonably, with Hydrotaea houghii most prevalent in December, Fannia canicularis in January, Psychodidae in February, Dendrophaonia scabra in March and April, Psychoda alternata in May, Ophyra leucostoma in June, Telmatoscopus albipunctatus in August, September, and October, Leptocera venalicia in November, and Hydrotaea houghii again in December. Musca domestica was not an important species at any time, its maximum prevalence being 6 per cent of the total fly emergence during January. No significant variations in the species of flies emerging from the urban, suburban, or rural privies was noted.

Six different fractions from the venom of Vipera xanthina palestinae were separated out electrophoretically. Eluates of these fractions were tested in mice for lethal, hemorrhagic, neurotoxic and enzymatic activities.

About 80 per cent of the lethal activity of whole venom was concentrated in the A3 fraction which was dominantly hemorrhagic. Combined eluates of fractions K1–A1 and of A4–A5 were exclusively neurotoxic. Indirect hemolytic activity was strongest in fractions A4 and A5, while egg yolk-inhibitory activity was preponderant in fractions A2, A4 and A5.

Specific Vipera palestinae antiserum (Pasteur Institute) neutralized the hemorrhagic action of whole venom and of fraction A3 but it had very little activity against the neurotoxic components of the venom. The bearing of these findings on the pathogenesis of Vipera palestinae snake bite syndrome in human beings is obvious.

African Ixodoidia. I. Ticks of the Sudan, by Harry Hoogstraal. 1101 pages. Wash., D. C., U. S. Govt. Printing Office, 1956.

Home Health Emergencies, ed. by The Equitable Life Assurance Society of the United States. 256 pages. New York, The Life Assurance Society of the United States, 1956.

Lehrbuch der Tropenkrankheiten, ed. by Ernst Georg Nauck. 432 pages. New York, Intercontinental Medical Book Corp., $15.25.

The Happy Life of a Doctor, by Roger I. Lee. 278 pages. Boston, Little, Brown & Company, 1956. $4.00.

Historia da Lepra nó Brasil, Vol. III. Periodo Republicano (1890–1952), by de Sousa-Araujo. 715 pages. Rio de Janeiro, Departamento de Impresna Nacional de Brasil, 1956.

In format, this volume is comparable to the first proceedings (reviewed in this journal Sept., 1952). The Subject matter, however, is organized more along the lines of specific diseases and disease vectors than was the case with the earlier book.

In order to include and appeal to some executives of tropical ventures, the first day's discussions were held in New York and centered around economic and social aspects of health services in the tropics. Dr. Thomas Weller also presented “Recent Developments in Poliomyelitis” at that time. When the Conference subsequently convened in Boston, most of the presentations of recent information on a disease or method of control were made by experts on the subject with discussion by resident physicians in tropical areas. This pattern is examplified not only by Weller's topic but also by “Trachoma” (Phillips Thygeson); “Arthropod-Borne Viruses in the Tropics” (Harold Johnson); and “Human Performance in Excessive Heat” (C. P. Yaglou).