Showing papers in "American Journal of Tropical Medicine and Hygiene in 1972"

Genetic factors in the susceptibility of juvenile Biomphalaria glabrata to Schistosoma mansoni infection.

Abstract: Susceptibility to infection with Schistosoma mansoni was studied in juvenile Biomphalaria glabrata by isolated selfing and by crosses. True-breeding snail stocks were derived testing 100% or 0% juvenile susceptible. Crosses suggested that juvenile susceptibility was regulated by a complex of four or more genetic factors. Genes for insusceptibility could be transmitted by susceptible snails and genes for susceptibility by refractory snails.

The influence of vector behavior on malaria transmission.

Abstract: Summary Delays in malaria eradication programs are caused more by non-response of fully susceptible vectors to attack measures than by physiological resistance, though the latter receives more attention. Currently recommended methods for vector studies are reviewed, with suggestions for their extension. Three principal South American vectors are shown to rest mainly outside houses by day; some exophily existed before the use of DDT. Their biting cycles are unimodal, with peak activity near midnight, contrasting with minor vectors and non-vectors with bimodal or crepuscular cycles. A. nuneztovari, hitherto thought an anomalous exophagic and crepscular vector, includes two species, a widely distributed non-vector, A. dunhami, and an endophagic nocturnal vector. Observations, mainly from Colombia, on nocturnal contacts with indoor surfaces by vectors, and on entry to and exit from houses are described; contacts were mainly with the lowest parts of walls, well below the height to which they are sprayed. The times of sighting of vectors resting unfed and fed showed normal distributions, their means separated by intervals of 30 to 150 minutes. In A. darlingi, the interval was 150 minutes in unsprayed, 78 minutes in sprayed houses; in A. punctimacula and A. nuneztovari in sprayed houses, the intervals were 96 and 30 to 60 minutes, respectively. The durations of the contacts showed skewed distributions with short periods, medians 1 to 2.5 minutes in all three species, predominating. Mean durations, biased by a few long periods, were greater, for A. darlingi reaching 12 minutes in sprayed houses, 6 in unsprayed. Times of entry and exit to houses, studied in A. darlingi with a drop-net lowered to enclose a house at intervals through the night, showed that, before spraying, about half the mosquitoes entering fed inside, during a stay of about 2 hours. For 3 months after use of a DDT-HCH mixture, 65% of those entering failed to leave; mean stay was 3 hours. Later, with DDT treatment only, the proportion entering and failing to leave fell to 28%. Vector attack, human receptivity, and infectivity of the plasmodial gametocyte, all reach maxima inside houses, late at night; this is the key to persistence of transmission by susceptible vectors. In spite of the prevailing daytime exophily, vectors make multiple short contacts with insecticide-treated surfaces, repeated on each gonotrophic cycle; these are inadeuate to halt transmission in areas of low elevation, high humidity, and temperature, occupied by poorly housed colonists; insecticides lacking the locomotor stimulant action of DDT may be the remedy.

A Prospective Study of Serum Antibody and Protection Against Smallpox

Abstract: In order to prospectively evaluate the relation between serum antibody and protection against smallpox, blood was drawn from 146 contacts of Pakistani smallpox cases before the end of the usual incubation period. Most were well vaccinated, and after follow-up only three cases of secondary smallpox appeared. Hemagglutination inhibition antibody titers proved to have virtually no predictive value for assessing susceptibility against smallpox, since most contacts, despite their protection, had undetectable antibodies. Neutralizing antibodies were present in high titer in most contacts and no contacts with a titer of 1:32 or higher developed smallpox. Two of the cases, however, did have detectable neutralizing antibody at the time of exposure and some persons with no detectable neutralizing antibody were spared. The role of humoral antibody in protection against pox-viruses is still unclear.

A Fatal Human Infection with Mokola Virus

Abstract: A six-year-old Nigerian girl presented in hospital with symmetrical paralysis of the extremities and drowsiness which progressed to deep coma. She died 72 hours after admission. Mokola, a rabies related virus, was isolated from brain material obtained at autopsy, making her the first known case of fatal human infection with this virus. Histologically, sections of the brain showed perivascular cuffing mostly by lymphocytes, although many atypical primitive lymphoblastoid cells were also present. Sections stained with phloxine tartrazine revealed large numbers of finely granular, stippled cytoplasmic inclusion bodies in many neurons. The inclusion bodies are easily distinguishable from Negri bodies and may be a distinctive feature of infection with Mokola virus.

Development of Toxoplasma oocysts in neotropical felidae.

Abstract: Toxoplasma gondii oocysts were isolated from the feces of one Felis yagouaroundi (jaguarundi) and two Felis pardalis (ocelot) which initially lacked antibody to Toxoplasma gondii, establishing that not only domestic cats, but other members of the family Felidae can spread Toxoplasma via their feces. These findings explain the reported occurrence of toxoplasmosis in jungle wildlife in the absence of a domestic cat population. A number of Felidae with positive antibody titers to Toxoplasma did not excrete Toxoplasma oocysts after being fed cysts of Toxoplasma. Members of the Procyonidae (raccoon family), Potos flavus, Nasua nasua, and Bassaricyon gabbii, failed to produce oocysts although they became infected and developed antibody to Toxoplasma.

Effect of mosquito density on the interrelationship of host behavior and mosquito feeding success.

Abstract: A night heron, a green heron, a white ibis, and a cattle egret were individually exposed overnight in 8-ft cages to densities of Culex nigripalpus ranging from 25 to 1,200 per cage. Surviving mosquitoes were examined the following morning and engorgement rates were determined as a measure of effect of antimosquito activity. In addition, the behavior of each bird was recorded for 2-hr periods at three different mosquito densities. Results indicated an inverse relationship between the density of mosquitoes and the proportion that successfully obtained blood. This relationship was ascribed to the increase in defensive activity displayed by the birds (differing in degree according to species) when exposed to increases in mosquito density. The frequency of interrupted feeding (= partial blood meals) was also related to host behavior and mosquito density.

Raised Levels of Serum IgE in Human Helminthiases

Abstract: The concentration of serum IgE in four human helminthiases was determined by an indirect single radial immunodiffusion method. Whereas in most normal adults serum levels of IgE were below 300 units/ml, raised levels of IgE were found in patients infected with helminths. Mean values were 1,210 units/ml in 60 cases of schistosomiasis japonica, 3,400 units/ml in 5 cases of paragonimiasis, 2,960 units/ml in 4 cases of fascioliasis hepatica, and 570 units/ml in 10 cases of hookworm infection. The results clearly indicate that an increase of serum IgE concentration occurs in various helminthic infections, although the significance of this is still obscure.

The impact of malaria on economic development. A case study.

Abstract: Summary An attempt is being made to demonstrate concretely the economic impact which malaria has had on a group of about 300 farm families in Eastern Paraguay. Families were chosen in eight clusters of approximately forty families each, in areas expected to have a high incidence of malaria during the early portion of the period of data collection. Field activities were carried on for 18 to 20 months, depending upon the area, August 1968 to June 1970. A national malaria eradication campaign was in preparatory phase and in the 9th month of data collection initiated DDT spraying in the areas under study, thus providing a relatively malaria transmission-free condition from the 11th month on. Data concerning the health of all residents on the farms, and detailed information concerning all economic activities—farm work, non-farm work, harvests, sales, purchases, cattle and poultry owned—were registered at 2-week intervals for all farms, by personnel of the project resident in the eight localities under study. Health information has been processed and shows that in 2 of the 8 areas there was high malaria incidence from August 1968 until June 1969, in 3 areas medium-high incidence, and in 3, very little. In the succeeding months, after DDT spraying, there was low to very low incidence in all areas. Of working time lost because of illness, 55% was due to malaria during the first 10 months, and 26% (of a much reduced total) in the remaining months. Economic data are now being processed. Indicators to be investigated include days worked as per cent of available work-days; proportion of work done by children; proportion done by paid help; total value of harvests; division of harvest as between cash crops and subsistence crops; yield per hectare, per 1,000 plants sown, and per day of work done; hectares of land newly brought into production; maximum hectares cultivated during the crop year; number and condition of farm buildings and construction activities; numbers and changes in stocks of animals and poultry; non-farm work done; earnings from non-farm work, total and per day; division of expenditures between consumption and investment; total level of expenditures; total consumption including self-produced; total income; and various other relationships and series. It is expected that the most fruitful approach will be the comparison of the performance of each farm during the later period with its own performance during the first 10 months (using equivalent months in the 2 crop years). As some families suffered from malaria heavily, others more lightly, and some not at all, this will permit comparisons among them. The techniques of linear multiple regression and analysis of variance will be applied.

Yersiniosis in mammals and birds in the United States: case reports and review.

Abstract: Yersinia pseudotuberculosis infection has been reporte in the United States in six species of domestic mammal (cat, cow, goat, rabbit, sheep, and swine), five species of wild mammal including black-tailed jack rabbit (Lepus californicus), white-tailed antelope squirrel (Citellus lecurus), eastern cottontail (Sylvilagus floridanus), black-faced kangaroo (Macropus melanops), and albino fallow deer (Dama dama), and three birds (canary, dove, and pigeon). Also, epizootics in chinchilla caused by Yersinia enterocolitica have been recorded in the United States. The importance of intestinal carriers in fecal-oral spread of infection is emphasized in the epizootiology of yersiniosis (infection with Y. pseudotuberculosis or Y. enterocolitica). Wild birds and rodents appear to be significant reservoirs of Y. pseudotuberculosis, but birds have not been found infected with Y. enterocolitica.

Serodiagnosis of American leishmaniasis by indirect fluorescent antibody test.

Abstract: The frequent difficulty of establishing a parasitologic diagnosis in American leishmaniasis has established the need for a reliable serologic test, which has not been available up to this time Preliminary attempts to adapt the indirect fluorescent antibody test were unsuccessful when promastigote forms of a recent human isolate of Leishmania braziliensis from culture were used as antigen However, the use of intracellular amastigote forms freed from Vero tissue culture cells by osmotic disruption, resulted in reproducible specific reactions in 89% of 75 sera of leishmaniasis patients Reactions up to a dilution of 1:1,024 were obtained, with a mode at 1:16 In comparison, 93% of control sera from 100 healthy persons and 75 hospital patients with other diseases gave completely negative reactions, and the great majority of those nonspecific reactions which did occur were at a dilution of 1:8 This test has proved to be a useful adjunct to other diagnostic procedures

Toxicity of Costa Rican snake venoms for the white mouse.

Abstract: Venom yields and toxicity levels for Costa Rican snakes are reported. It was found that the sea snake, Pelamis platurus, possesses the most potent venom. Taking into consideration toxicity and venom yields, the fer-de-lance, Bothrops asper (formerly included in B. atrox), appears to be the most dangerous snake in Costa Rica and Lachesis muta, despite its impressive size, occupies a relatively unimportant position. The data show that in toxicity or neutralization experiments in which mice are used it is desirable to prolong the observation period up to 48 hours when employing crotalid venoms and up to 72 hours when using elapide venoms.

Studies on the characterization of plasmodium vivax strains from Central America.

Abstract: Summary Four strains of vivax malaria from three Central American countries (Panama, El Salvador, Nicaragua) were studied in volunteers for characteristics of their relapse patterns and for their response to recommended dosage regimens of some standard antimalarial drugs. The relapse patterns of the four Central American vivax strains fell into the “temperate zone” category of relapse pattern; namely, an early primary attack (short prepatent period) followed by a long period of latency before appearance of frequent relapse activity. The characteristics and classification of relapse patterns are discussed.

Ancylostoma ceylanicum: a parasite of man in Calcutta and environs.

Abstract: Sixteen of 183 persons (8.7%) of a predominantly rural sample population (175 from a village 40 miles north of Calcutta and 8 from the city) harbored Ancylostoma ceylanicum. In all but one instance this species occurred concurrently with both Necator americanus and A. duodenale; in the remaining case it was recovered with the latter only. A. ceylanicum constituted 0.1% of all the hookworms recovered, and even in the 16 persons infected with this species it accounted for only 1.3% of the worms. In only one of these infections were both sexes represented.

Rapid bactericidal effect of rifampin on Mycobacterium leprae.

Abstract: Rifampin was rapidly bactericidal for Mycobacterium leprae. Leprosy responds very slowly to current therapy, so there is a special need for more rapidly effective drugs. In mice rifampin exerted a bactericidal-type effect with single administration by gavage; the effect increased with dosage in the range 10 to 40 mg/kg of body weight. Five patients with lepromatous disease were treated with 600 mg rifampin daily, and the viability of the bacilli in their skin lesions was tested by inoculation of mice. Infectivity for mice had completely disappeared in the 1st specimen collected after the start of therapy—at 7 days in 4 patients and 14 days in 1. In 4 control patients treated with dapsone, infectivity for mice was lost much more slowly and in 1 was still present, though decreased, 112 days after the start of treatment. The slower loss of infectivity with dapsone is in accord with our previous experience in which the same methods were used.

Decreased Deformability of Plasmodium Coatneyi-Infected Red Cells and Its Possible Relation to Cerebral Malaria*

Abstract: In a previous study we demonstrated that Plasmodium knowlesi-infected red cells have decreased deformability and suggested that this abnormality may be important in the pathophysiology of malaria. The present rheologic study was performed in monkeys infected by Plasmodium coatneyi in order to assess further the role of abnormal red cell deformability in the pathogenesis of disease. P. coatneyi is much more similar to P. falciparum than is P. knowlesi. Red cells infected by trophozoites and schizonts showed an increase of viscosity when suspended in Ringer's solution, caused increased resistance to flow through pores, 5 µ in diameter, in the polycarbonate sieve and were excluded from rouleaux formed in plasma. Ring forms produced less rheologic abnormality in the red cell than the more mature stages. These studies indicate that red cells infected by mature parasites of P. coatneyi have decreased deformability to the same extent as we observed in P. knowlesi. The possible relationship between the decreased deformability of infected red cells and cerebral malaria is discussed.

Malabsorption in Plasmodium falciparum malaria.

Abstract: Impaired gastrointestinal function was detected during the acute phase of illness in patients with Plasmodium falciparum malaria. Nine of 11 (82%) had diminished D-xylose absorption, 6 of 10 (60%) had decreased absorption of vitamin B12, and 5 of 11 (45%) had low serum carotene levels. A majority of the tests for absorptive function returned toward normal during the convalescent period. Jejunal biopsies in 6 of 7 patients with malaria revealed edema and round cell infiltration of the lamina propria, and shortening and widening of villi. In 5 of these biopsies the presence of malarial pigment and parasitized red blood cells was noted within the mucosal vessels. In each case, the morphologic changes reverted toward normal during convalescence. The pathophysiologic mechanism responsible for the malabsorption syndrome in malaria has not been elucidated but may be due in part to ischemic changes in the mucosa of the small bowel.

Anaphylactic shock following bite by a 'slow loris', Nycticebus coucang.

Abstract: A case of anaphylaxis of the circulatory collapse type and complicated by hematuria following bite by a “slow loris” (Nycticebus coucang) is reported. Treatment consisted in supportive measures and an antihistamine. The patient made a full recovery. There was no clinical evidence of any toxic substance in the saliva of the loris in spite of a northern Thai folklore belief that Nycticebus is a venomous animal.

Serologic diagnosis of amebiasis.

Abstract: The indirect hemagglutination (IHA), complement fixation (CF), and agar gel diffusion (Gel) tests were evaluated in the diagnosis and management of amebiasis. Axenically-grown Entamoeba histolytica was used as antigen. A survey of 3,033 patients from our hospital population showed IHA titers indicative of infection in 32 patients (1.1%): 6 had parasitologic or clinical evidence of amebic infection and 10 others had additional serologic evidence of E. histolytica antibodies. Of 345 patients in another study with symptoms suggestive of amebiasis, 85% of 107 with proven infections had positive IHA tests. The three serologic tests were compared in 16 extraintestinal and 127 intestinal cases of amebiasis. All tests were positive in 88% of extraintestinal cases. The IHA test was positive in 95, 61, and 58%, respectively, of invasive, symptomatic and asymptomatic colon cases; the CF test in 85, 56, and 58%; and the Gel test in 86, 54, and 52%. The IHA test was somewhat more sensitive and tended to remain positive longer after cure, but all tests often remained positive for 6 to 12 months, and occasionally for 1 to 3 years. The titer was not helpful in differentiating extraintestinal from intestinal, nor even symptomatic from asymptomatic amebiasis. Skilled judgment is essential in clinical use of these serologic tests.

Sporozoite-induced immunity in mammalian malaria. A review.

Abstract: Summary Based on experimental evidence the following fundamental characteristics of sporozoite-induced immunity have, so far, been established. 1. The sporozoite stage of malaria parasites is strongly immunogenic. The intravenous injection of small numbers of attenuated, X-irradiated sporozoites induces a high degree of protective immunity and formation of anti-sporozoite antibodies. 2. Sporozoite-induced immunity is highly stage-specific. Its effects are mainly directed against the sporozoite stage. The erythrocytic stages of the parasite are not affected by this immune mechanism. 3. Considerable cross-protection and serologic cross-reactivity occur among sporozoites of different rodent malaria strains and species. 4. Sporozoites undergo antigenic changes during their process of maturation. These might possibly be correlated with the development of sporozoite infectivity. 5. The spleen does not play an essential role in sporozoite-induced protective immunity. The immunization of splenectomized animals renders them resistant to sporozoite challenge in the absence of antibodies detectable by the CSP reaction. 6. Sporozoite-induced immunity is, at least in part, serum-mediated. The incubation of sporozoites with immune serum considerably reduces their infectivity. The passive transfer of immune serum considerably increases the rate of sporozite clearance observed in normal animals. 7. The non-specific stimulation of the reticulo-endothelial system which occurs during sporozoite immunization is very shortlived. This reticulo-endothelial system stimulation does not play an important role in protection against sporozoite challenge.

Studies on the ecology of Anopheles albimanus.

Abstract: Summary In general, it seems that A. albimanus might be more zoophilic than anthropophilic, more exophagic than endophagic, more exophilic than endophilic, not particularly long-lived, and infrequently found harboring malaria parasites. Yet, this species is considered to have been responsible for the annual transmission of malaria to thousands of people in El Salvador. This might be due to overwhelming numbers, to the existence of extremely effective “strains” or to a combination of reasons not easily understood.

Human amebic dysentery. Electron microscopy of Entamoeba histolytica contacting, ingesting, and digesting inflammatory cells.

Abstract: Biopsy samples from human cases of amebiasis were studied by electron microscopy. Numerous inflammatory cells passed through flattened or damaged epithelium into the colonic lumen. Polymorphonuclear leucocytes, eosinophils, and lymphocytes were eaten and digested by amebae, as in the well-known ingestion of red blood cells. Ingested inflammatory cells have apparently not been recognized because one of the first changes, preceding loss of external membranes in food vacuoles, is loss of nuclear affinity for stain. Inflammatory cell ingestion seems to be characteristic of amebae causing human dysentery. Inflammatory cells do not effectively limit amebic activities and may even contribute to host damage. Cytotoxic materials could be released directly by lysis of uneaten cells or might pass through the amebae and be released (possibly altered) from excretory vacuoles.

In vivo microscopic observations of the pathogenesis and pathophysiology of hepatosplenic schistosomiasis in the mouse liver.

Abstract: In vivo microscopic observations have elucidated the pathophysiology of hepatosplenic schistosomiasis mansoni in the mouse. Numerous schistosome eggs trapped in the interlobular portal venules partially or completely obstruct flow. Each egg is capable of obstructing blood flow to about 10 functional hepatic units (defined in text). In mice with severe hepatosplenic disease and portal hypertension, egg loads may reach 10,000 per gram of liver, but they block blood flow to only 6% of the total number of functional units. The host's granulomatous and fibrotic reaction to the eggs, which more than doubles the weight of the liver, imposes an extensive presinusoidal block to liver blood flow. Neovascular formation occurs in the scar tissue and provides a bridge between the presinusoidal vasculature and the sinusoids. The rapidity of the blood flow in these new vessels suggested that they were arterial; this was confirmed when ligation of the hepatic artery resulted in cessation of blood flow not only in the scar tissue but also in the adjacent sinusoids and central venules. On the basis of these studies, the pathophysiology of hepatosplenic schistosomiasis mansoni may be summed up as follows: schistosome eggs and the granulomatous inflammation and scar tissue around them gradually shut down portal venous flow. This results in portal hypertension, congestive splenomegaly, and the development of portal-systemic collateral circulation. Compensatory arterialization occurs through neovascular formation and this maintains sinusoidal perfusion and liver function within relatively normal limits.

Effects of minocycline against chloroquine-resistant falciparum malaria.

Abstract: The antimalarial effects of minocycline, a semi-synthetic tetracycline, were evaluated in chloroquine-resistant Plasmodium falciparum infections. Nine volunteers infected with the Vietnam (Marks) strain were cured after each received a 7-day course of minocycline. Two additional subjects infected with the same Vietnamese strain were cured after each received a combination of minocycline and quinine. Minocycline protected 16 of 18 volunteers after challenge with Anopheles stephensi mosquitoes infected with chloroquine-resistant strains of P. falciparum. Eleven men were protected against a single challenge by mosquitoes infected with the Cambodia (Buchanan) strain. Five of seven volunteers were protected against a single challenge by mosquitoes infected with the Vietnam (Marks) strain. No sporontocidal or gametocytocidal effects occurred in one volunteer who received a 7-day course of minocycline.

La Crosse Virus Isolations from Mosquitoes in Wisconsin, 1964–68*

Abstract: Eight isolates of La Crosse virus were obtained from 182,437 mosquitoes (4,643 pools) processed during 4 years of a 5-year study. Of the 8 isolates, 5 were from 1,985 Aedes triseriatus (70 pools), and 1 each was from 1,818 Culex pipiens, 35,867 Aedes communis group, and 36,800 Aedes trivittatus. Six of the isolates were from mosquitoes collected by aspiration, and the other two from Culex pipiens and Aedes trivittatus collected in carbon dioxide-baited cone traps. Seasonal distribution of the isolates was similar to that of cases of California encephalitis: 3 in July, 2 in August, and 3 in September. Aedes triseriatus is common in hardwood deciduous forests where in small wild mammals antibodies to the virus are prevalent and where children hospitalized with the disease have been exposed to the virus in nature.

The epidemiologic interpretation of serologic data in malaria.

Abstract: Summary The indirect fluorescent antibody test promises to be of value for epidemiologic work in malaria. Some of the variables which may affect this test are discussed briefly. A mathematical model for analyzing age-related antibody prevalence rates is described and its application is illustrated by data from recent surveys in East Africa and in Amazonas, Brazil. Fallacies and difficulties, such as congenital antibodies and the use of simian parasites as antigens, are discussed, together with conditions where the use of serologic methods may be valuable.