Showing papers in "American Journal of Tropical Medicine and Hygiene in 1978"

Concentration from continuous culture of erythrocytes infected with trophozoites and schizonts of Plasmodium falciparum.

Abstract: Gelatin, from readily available sources, at specified concentrations in RPMI 1640 medium enhances sedimentation rates of suspensions of Plasmodium falciparum-infected erythrocytes from continuous cultures, resulting in an enrichment of the trophozoite- and schizont-infected cells to parasitemias of 75% or more with no deleterious effects to the parasites.

Evaluation of serodiagnostic tests for visceral larva migrans

Abstract: Four serologic techniques for the diagnosis of visceral larva migrans caused by Toxocara canis, namely indirect hemagglutination (IHA), bentonite flocculation (BF), enzyme-linked immunosorbent assay (ELISA), and double diffusion in agar (Ouchterlony), were evaluated using sera sent to the Center for Disease Control from patients with a presumptive diagnosis of visceral larva migrans (VLM). Patients having 5-6 of the clinical or laboratory criteria for VLM were designated as cases while those with 0-2 criteria served as controls. The sensitivity of the ELISA was 78.3% compared to 18.2%, 25.8% and 65.2% for the IHA, BF, and Ouchterlony, respectively; the sepcificity of all four tests was greater than 92%. The predivtive value of positive test was greater than 85% for all tests except the IHA, while the predictive value of a negative test was greater than 85% only for the ELISA. The results of a ELISA were reproducible in different laboratories. Based on these findings, the ELISA using a larval antigen appears to be the serodiagnostic method of choice for VLM.

Epidemiologic, clinical, and virologic observations on dengue in the Kingdom of Tonga.

Abstract: An outbreak of dengue type 2 infection occurred in the Pacific island Kingdom of Tonga in 1974 and an outbreak of dengue type 1 occurred there in 1975. The 1974 outbreak was characterized by relatively mild clinical disease with few hemorrhagic manifestations, a low attack rate, and relatively low viremia levels. The 1975 outbreak was characterized by relatively severe disease with frequent hemorrhagic manifestations and a high attack rate. The differences between the outbreaks could not be attributed to differences in abundance of, or susceptibility to infection of, mosquito vectors or to the prior immune status or other characteristics of the human population. It appeared that a difference in viral virulence was the most likely explanation.

Diagnostic value of the Widal test in areas endemic for typhoid fever.

Abstract: The usefulness of a single Widal test to diagnose typhoid fever in endemic areas was investigated. Reciprocal Salmonella typhi O and H titers greater than or equal to 40 and greater than or equal to 80, respectively, occurred in approximately 90% of 42 Mexican patients with bacteriologically-confirmed typhoid fever at the time of presentation to hospital and, by day 4 to 5 of clinical illness, in 70% of U.S. adult volunteers who developed typhoid fever in the course of vaccine efficacy trials but in only 0.7% (O) to 3% (H) of 275 healthy individuals from a non-endemic area. Healthy Peruvians from areas endemic for typhoid fever commonly had antibody which was age-related. Peak prevalence was found in 15- to 19-yr-olds in whom 29% had O titers greater than or equal to 40 and 76% had H titers greater than or equal to 80. A single Widal test in an unvaccinated individual showing elevated O and H titers is strongly suggestive of typhoid fever if the person comes from a non-endemic area or is a child less than 10 yr of age in an endemic area. Because of the high prevalence of antibody amongst healthy invididuals over 10 yr of age in endemic, areas, a single Widal test offers virtually no diagnostic assistance in adolescents and adults.

Plasmodium Falciparum in Culture: Establishment of Additional Strains*

Abstract: The establishment of new strains of Plasmodium falciparum in continuous culture is described. One line (FCR-2), isolated from an individual who had traveled extensively through South America, was passed initially through Aotus trivirgatus monkeys and then cultured into human erythrocytes using the flow-vial technique. A strain of P. falciparum FMG), shipped by air freight on wet ice from The Gambia, was cultured directly from a human infection into continuous culture using the Petri dish-candle jar technique, giving line FCR-3. Two other strains (6252 and FSG) were hand carried by a commercial flight on wet ice from the Gambia and were initiated into culture at the same time using the same media, sera, and erythrocytes. After 6 wk in vitro the 6252 strain became adapted as line FCR-4, whereas FSG had died out. Normal-looking gametocytes were seen in all four strains reported here. Notwithstanding their normal appearance they would not exflagellate in vitro, nor were they infective to Anopheles stephensi mosquitoes via membrane feeding. Production of new gametocytes continued for 6 mo, then gradually stopped.

Aedes Aegypti in Puerto Rico: Environmental Determinants of Larval Abundance and Relation to Dengue Virus Transmission

Abstract: In order to understand adequately the dynamics of vector-borne disease, one must understand how and why vector populations change over time. We describe a long-term, cooperative study of seasonal fluctuation in populations of the Aedes aegypti mosquito in Puerto Rico. During each month of the first 3 years of the project, A. aegypti was found breeding in all five communities studied. Mosquito density was positively correlated with rainfall, the relationship being more marked in the dry, south-coastal part of the island. Discarded tires and animal watering pans were the two most common larval breeding sites. In general, houses in Puerto Rico harbor more potential A. aegypti breeding sites than those in other tropical locations, probably because Puerto Rico is relatively more affluent.

Liver changes in hamsters infected with a liver fluke of man, Opisthorchis viverrini.

Abstract: Thirty male Syrian golden hamsters were each infected with 100 metacercariae of Opisthorchis viverrini. The hamsters were killed at 3, 7, 15, 30, 154 days of infection. The early pathological changes consisted of an acute inflammatory reaction involving the bile ducts of the second order and the portal connective tissue, especially the large veins, as well as focal coagulation necrosis of the liver lobules. As the flukes developed into adults they induced hyperplasia and adenomatous formations of the bile duct epithelium. There was also a granulomatous response to the adult flukes and eggs. Resolution of the granulomas led to periductal and portal scarring. These findings suggest that immunopathologic mechanisms may be important in the pathogenesis of liver fluke disease.

Blood meal size as a factor affecting continued host-seeking by Aedes aegypti (L.).

Abstract: The effect of ingested blood on the host-seeking response of two strains of Aedes aegypti was examined. Using an olfactometer, females fed partial blood meals were scored for host-seeking behavior within 1 h, and their blood meal sizes were measured chemically immediately afterwards. The suppression of host-seeking within 1 h after a blood meal appears to be caused by abdominal distention from ingested blood. Mosquitoes of either strain were attracted to a host when the blood meal size was less than 2.5 microliter; above this threshold there was a sharp decline in the tendency to respond. Small mosquitoes resulting from a low larval diet had a lower threshold, and were more likely to cease host-seeking after a small blood meal. Multiple feeding within a single gonotrophic cycle may result if mosquitoes take small blood meals which are insufficient to terminate host-seeking. Partial meals and reduced feeding success of mosquitoes can result from defensive host behavior, which in the laboratory rat was shown to increase at high mosquito densities.

Immunization of mice with cobalt-60 irradiated Schistosoma mansoni cercariae.

Abstract: Parameters of immunization of mice with /sup 60/Co-irradiated Schistosoma mansoni cercariae are described and related to protection against subsequent challenge infection. Such immunization was found to be dependent on dose of irradiation, number of immunizing cercariae, and number and time course of infections. Low levels of resistance were obtained with low irradiation doses, in contrast to previous studies in mice. In general, resistance increased with increasing irradiation doses, up to approximately 48 to 56 Kr. Maximal resistance (70 to 80%) was induced by a single exposure to 250 to 500 cercariae, irradiated at a dose rate of 2 Kr/minute to a total dose of 56 Kr, administered percutaneously 4 to 6 wk prior to challenge. Challenge could be delayed for at least 15 wk after immunization without a decrease in resistance. The resistance obtained was not attributable to a delayed migration of challenge worms.

Babesia microti infection in man: evaluation of an indirect immunofluorescent antibody test.

Abstract: An indirect immunofluorescent antibody test was used to detect antibody to Babesia microti in human sera. Nine patients from Nantucket Island, Massachusetts infected with B. microti had serum titers greater than or equal to 1,024. Of 84 control sera from New York City residents, 246 sera from patients with possible exposure to ticks, and 36 sera from patients with suspected or confirmed tick bites, none was reactive at titers of 1:16 or above. The within-test reproducibility was within one fourfold dilution in 95% of trials. Test-to-test reproducibility was within one fourfold dilution in 33% of trials and within two fourfold dilutions in 100% of trials. Although cross-reactions among infected patients' sera and antigens of B. argentina, B. equi, B. bigemina, Plasmodium vivax, P. falciparum, and P. brasilianum were common, titers were highest to the homologous antigen.

Biochemical characterization of some species of Trypansoma (Schizotrypanum) from bats (Microchiroptera).

Abstract: Trypanosoma (Schizotryanum) species isolated from bats (Microchirotera) in Europe and Latin America were examined by determining the buoyant densities of their nuclear and kinetoplastic deoxyribonucleic acid (DNA) and the electrophoretic patterns of six isoenzymes. By these criteria they were separated into three distinct groups -- two from Europe (T. dionisii and T. vespertilionis) and one from America. T. dionisii was also separable by its morphology in vitro. Geographical location and DNA buoyant densities suggested that the American stocks were more closely related to T. cruzi than to the European species, though they differed from it marginally in kinetoplastic DNA density and in being noninfective to mice. Similar stocks studied by other workers have been shown to differ from T. cruzi also in reduced infectivity to, and lack of natural association with, Triatominae, and in antigenic composition. It is therefore proposed that trypanosomes of the subgenus Schizotryanum occuring naturally in Microchiroptera and differing from T. cruzi sensu stricto as outlined above should be treated as a distinct subspecies, T. cruzi marinkellei ssp. nov. T. cruzi sensu stricto thus becomes the nominate subspecies T. cruzi cruze Chagas 1909.

Schistosoma mansoni and S. haematobium infections in Egypt. III. Extrahepatic pathology.

Abstract: Schistosoma mansoni and S. haematobium infections were studied quantitatively in 400 consecutive autopsies in Cairo, Egypt. Pathological findings were correlated with the presence or absence of schistosome infection as well as with the intensity of infection. The intensity of S. haematobium infection was much greater in cases with obstructive uropathy (hydroureter or hydronephrosis) than in those without; however, infection intensity was similar in cases with mild or severe obstructive uropathy; i.e., the presence, but not the degree, of obstructive uropathy was related to infection intensity. The presence of focal lesions was more important in the pathogenesis of severe obstructive uropathy than was the concentration of eggs in the ureters or bladder. The most severe cases of schistosomal obstructive uropathy were usually caused by ureteral stenosis, ureteral stones or distortion of the ureteral orifices. Pyelonephritis was of similar frequency in cases with and without schistosomiasis. Pyelonephritis occurred most often in patients with bladder outlet obstruction or distortion of the ureteral orifices. In the absence of these lesions, hydroureter did not predispose to pyelonephritis. Glomerulonephritis was not positively associated with S. haematobium infection. S. mansoni infection caused severe schistosomal colonic polyposis in three heavily infected individuals. Both S. mansoni and S. haematobium also caused less marked polyposis. Salmonella infections were infrequent and not significantly associated with schistosomiasis. In this series, schistosomiasis was rare in patients 9 yr or less of age. Among cases over 9 yr of age, schistosomiasis was considered the cause of death in 9.2% of infected cases (6.2% of all cases). Among infected cases, 2.5% of deaths were ascribed to schistosomal obstructive uropathy, 2.4% to bladder cancer associated with schistosomiasis, 3.1% to Symmers' fibrosis of the liver, 0.8% to schistosomal colonic polyposis and 0.4% to salmonellosis associated with schistosomiasis. Although we made no deliberate selection of cases for study, any hospital-based series gathers a highly selected group of patients. Our results should be applied to other infected populations with great caution. In addition, pathologic studies concentrate on serious anatomic lesions and cannot accurately evaluate the effects of other important lesions, such as schistosomal cystitis, which produce considerable morbidity.

Antibody response to a polysaccharide antigen present in the schistosome gut. I. Sensitivity and specificity.

Abstract: Specific IgM and IgG antibody to a polysaccharide present in the epithelial cells of the gut of adult schistosomes was measured in four groups of infected patients: I) patients with documented acute schistosomiasis; II) Americans exposed to schistosomiasis within the preceding 0–4 years; III) chronically and heavily infected patients, mostly from Puerto Rico, without hepatomegaly or hepatosplenomegaly; and IV) heavily infected Brazilian children with hepatic or hepatosplenic schistosomiasis. Specific IgM and IgG titers were both highest in the acute Group I patients and lowest in the chronically infected Groups III and IV. Total IgG and IgM levels were compared to specific antibody titers. Immunoglobulin levels tended to follow specific antibody titers except in the chronically infected Groups III and IV in which total IgG rose to high levels. The decrease in specific antigen titers over the course of time occurred despite continued antigenic stimulation and suggests a modulation of the humoral response. The mechanism remains obscure.

Plasmodium falciparum and Plasmodium vivax infections in the owl monkey (Aotus trivirgatus). I. The courses of untreated infections.

Abstract: This study, the first of three designed to determine the feasibility of using owl monkeys infected with human plasmodia in the search for new, more broadly active antimalarial drugs, dealt with the characteristics of untreated infections with eight strains of Plasmodium falciparum and two strains of P. vivax. Such infections, induced by standardized inocula of these strains in 1,733 monkeys, all Aotus trivirgatus griseimembra, were followed from day of inoculation to death of self-cure. The virulence of the various strains differed strikingly. Incidences of fatal reactions, ranging from 24.4--89.4% and 8.1--45.8%, respectively, in infections with strains of P. falciparum and P. vivax, were closely related to the rate at which parasitemia evolved, the height of parasitemia in the primary attack, and/or the time period over which a high parasite level was sustained. Antemortem symptom complexes and gross tissue and organ reactions in infections with P. falciparum varied with survival time, but within that boundary, were the same for infections with all eight strains of this plasmodium. Morbidity in both fatal and self-limited infections with both plasmodial species was related to height of parasitemia; however, at comparable parasite levels, symptoms exhibited in infections with P. vivax were more severe than in infections with P. falciparum. Overall, the characteristics of infections with these plasmodia in owl monkeys were remarkably similar to those of human infections. With respect to biological features, infections with P. falciparum and P. vivax in this simian host appear to have much to offer in the search for new antimalarial drugs.

Epidemiologic Investigation of Marburg Virus Disease, Southern Africa, 1975

Abstract: During the first 10 days of February 1975, an Australian hitchhiker contracted Marburg virus disease while traveling through Rhodesia and died; the infection was subsequently passed to two other persons, who recovered. Investigators retraced the hitchhiker's steps in March and again in June 1975 in an effort to uncover the natural reservoir of the virus and determine how it was transmitted. Serum samples were collected from humans and animals wherever the patient had come in close contact with animals or insects. Arthropods of various types were collected in June 1975 and again in February 1976 for virus isolation attempts; at no time did the patient come in direct contact with nonhuman primates of any kind, or any other animals. Indirect contact with bats, monkeys, and birds through aerosols was possible, though at some distance. Direct contact with arthropods occurred throughout the trip; on several occasions it was notably severe. We believe that during this outbreak the first Marburg virus infection occurred by vector-borne transmission from an arthropod yet to be identified, and that patients 2 and 3 acquired the disease by exposure to the oropharyngeal secretions of patients 1 and 2, respectively. Studies are underway to identify the species of arthropod involved in this transmission.

Present status of kala-azar in Iran.

Abstract: Sporadic cases of visceral leishmaniasis have been reported from all parts of Iran except the deserts and very arid zones in the southeast. About 120 cases have been reported up to the present time, the majority from the mountainous areas of the southwest. Most patients (76%) have been children under 10 years of age. The probable reservoirs of infection are wild carnivores, infection of man and dog being accidental. During a survey conducted in the Caspian area and northeastern part of Iran in 1970, 20 jackals and 10 foxes were shot; examination of smears from bone marrow and spleen showed the infection in a jackal (Canis aureas) and in a fox (Vulpes vulpes). On the basis of epidemiological evidence, Phlebotomus major is the probable vector of kala-azar in Iran.

Leishmania infection of human skin fibroblasts in vitro: absence of phagolysosomal fusion after induced phagocytosis of promastigotes, and their intracellular transformation.

Abstract: Cellular interactions between human skin fibroblasts and promastigotes of two leishmanial species were studied in vitro by light and electron microscopy. Fibroblasts were found to become infected by the species with a history of causing mucocutaneous infection, but not by that of the visceral type or Leishmania donovani. Scanning and transmission electron microscopy revealed that promastigotes of the invasive species entered fibroblasts flagellum-end first through pseudopodia-like structures formed on the host cell surface, reminiscent of “induced phagocytosis.” Ingested promastigotes became lodged in vacuoles that did not fuse with secondary lysosomes prelabeled with an electron-dense marker for identification. Transformation of promastigotes into amastigotes occurred among those located within host cells and was influenced by the ambient temperature. Intracellular parasite populations gradually decreased during a 3-week period in vitro, although dividing forms were occasionally seen at all incubation temperatures (32–37°C). There was evidence that viable amastigotes were liberated by cytolysis and/or exocytosis of some infected cells. It is postulated that invasion of non-phagocytic cells by promastigotes and their subsequent transformation therein may allow them to escape from the often fatal consequence of direct confrontation with mononuclear phagocytes, and may be a survival mechanism associated with this parasite stage during the early host-parasite interaction in natural infection.

Resistance of mice to secondary infection with Schistosoma mansoni. II. Evidence for a correlation between egg deposition and work elimination.

Abstract: Mice reinfected with Schistosoma mansoni 6--8 weeks after a primary infection largely or completely eliminated the second infection prior to the 7-week adult worm stage. In contrast, challenge worm counts were not lower than controls at the 6-day lung schistosomulum stage. At reinfection intervals of 12 or more weeks, worm counts were reduced at both stages. The reduction in lung schistosomulum count was proportional to the number of schistosome eggs present in the lungs, with no significant reduction being detected at any challenge time in mice free of lung eggs. Isolated schistosome eggs injected intravenously into the lungs of normal mice induced moderate to high levels of resistance to infection, while eggs injected subcutaneously or imtraperitoneally did not. It is concluded that the deposition of schistosome eggs in sites encountered by migrating schistosomula may be essential for mice to become resistant to reinfection with S. mansoni.

Plasmodium falciparum and Plasmodium vivax infections in the owl monkey (Aotus trivirgatus). II. Responses to chloroquine, quinine, and pyrimethamine.

Abstract: The studies described in this report were designed to determine the responses of established infections with eight strains of Plasmodium falciparum and two strains of P. vivax in owl monkeys to treatment with chloroquine, quinine, and pyrimethamine. Responses with these different strains ranged from cure via application of well-tolerated doses of two of the above drugs and refractoriness to treatment with maximally tolerated doses of the third, to complete resistance to maximally tolerated doses of all three compounds. The results of treatment exhibited in infected owl monkeys correlated well in two respects with those reported in humans infected with the same plasmodial species. First, calculated on a milligram per M2 basis, the doses of chloroquine, quinine, or pyrimethamine required for a CD90 response in owl monkeys infected with strains susceptible to these drugs were remarkably similar to the doses required and/or employed for cure of infections with so-called drug-susceptible strains in human patients. Secondly, with few exceptions, the responses to the above drugs in owl monkeys infected with the ten specially selected strains were essentially identical with those exhibited by human volunteers or patients infected with the same strains. Together, these findings and correlations provide strong support for use of owl monkeys infected with appropriate strains of P. falciparum and P. vivax in the search for more broadly effective antimalarial drugs.

Trypanosoma cruzi-sensitized T-lymphocyte mediated 51CR release from human heart cells in Chagas' disease.

Abstract: Cytotoxicity of T-lymphocytes from patients with Chagas' disease to parasitized and non-parasitized human heart cells labelled with 51Cr was demonstrated. The highest ratio of 51Cr released from the normal, non-parasitized heart cells was observed when the T-lymphocytes were collected from patients with acute Chagas' disease. The quantity of 51Cr released from the normal heart cells that were destroyed by T-lymphocytes collected from patients with chronic Chagas' disease was also significantly higher than the quantity of 51Cr released from normal heart cells incubated with lymphocytes from normal donors. The specific release of 51Cr from the heart cell cultures destroyed by the immune T-lymphocytes from patients with acute Chagas' disease and from patients with chronic disease was 38.1% and 25.8%, respectively, compared to the release of 51Cr observed in control studies. A small particle human heart cell antigen was shown to inhibit the migration of Trypanosoma cruzi-immune peripheral blood leukocytes. These findings appear to indicate that T-lymphocytes from patients with Changas' disease are susceptible to activation by a cross-reactive heart cell antigen and suggest that an autoimmune mechanism can be established in some cases of acute Chagas' disease and can be perpetuated in the chronic phase of this disease by the continuous antigenic stimulation. Further, these experimental data indicate that the autoimmune destruction of heart cells in Chagas' disease is produced by delayed-type hypersensitivity mediated by T. cruzi-sensitized T-lymphocytes.

The prevalence of encephalomyocarditis virus neutralizing antibodies among various human populations.

Abstract: The prevalence of encephalomyocarditis virus (EMC) antibodies among selected human populations in various regions of the world was determined by the plaque reduction neutralization method. Antibody rates among children ranged from 1.0 to 33.9%, while those among adults varied from 3.2 to 50.6%. No differences between sexes were found in the frequency of EMC infection. The pattern of age-specific antibody rates observed among the study populations suggests that EMC infection occurs primarily during childhood. There appeared to be no association between the presence of EMC antibodies and potential exposure to rats. Sera from diabetic, suspected encephalitis, and myocarditis patients were also examined for EMC neutralizing antibodies. The prevalence of antibodies among these groups was not significantly different from that of control populations in the same geographic regions. No association was demonstrated between EMC infection and these three diseases. The results of this study indicate that EMC infection in man is fairly common but that most human cases are probably asymptomatic and/or unrecognized.

House construction, triatomine distribution, and household distribution of seroreactivity to Trypanosoma cruzi in a rural community in northeast Brazil

Abstract: Household distribution of seroreactivity to Trypanosoma cruzi in inhabitants was analyzed in relation to house construction and the distribution of Panstrongylus megistus, the principal domestic vector of Chagas' disease in a rural area in northeast Brazil. No children residing in mud-brick houses were seroreactive to T. cruzi. The highest rates of seroreactivity occurred in residents of unplastered mud-stick houses, and were twice as high as those found in persons living in mud-brick houses or plastered mud-stick houses. Two-thirds of seroreactive children in this area resided in unplastered mud-stick houses. Over 90% of the P. megistus infestations were found in mud-stick houses. Mud-brick houses had the lowest infestation rates of P. megistus and the lowest household rates of seroreactivity to T. cruzi.

Epizootiology of epidemic typhus (Rickettsia prowazekii) in flying squirrels.

Abstract: Vector transmission of Rickettsia prowazekii among wild flying squirrels, Glaucomys volans, was suggested by the occurrence of natural infection of squirrel lice and fleas. Lice, mostly Neohaematopinus sciuropteri Osburn, were found infected in the fall in each of 2 consecutive years; 4 of the 8 pools of this insect tested were infected. Fleas, Orchopeas howardii (Baker), were found infected on two occasions in 1 of the 2 consecutive years. However, only 2 of 14 flea pools were infected. No evidence of infection was found in mites, Haemogamasus reidi Ewing and Androlaelaps fahrenholzi (Berlese). These findings implicate the flying squirrel louse and flea as possible vectors in nature. Serologic tests of flying squirrel sera revealed a maximum incidence of seroconversions in the fall and early winter months, coincident with the maximum increase in abundance of the suspected arthropod vectors. The infection was found to persist form year to year in the same enzootic foci. Infection appeared to spread most rapidly in young, non-immune animals born in the preceding spring and summer after congregating in dense aggregations in the fall. No other animals in the same habitat were found to have been infected. Aspects of the ecology of the ectoparasites associated with the flying squirrels are described, especially seasonal activity and abundance in nests. The potential public health importance of this sylvan disease in flying squirrels and in its ectoparasites, particularly the non-host specific, wide ranging squirrel flea, is noted.

Changes in coagulation effects by venoms of Crotalus atrox as snakes age.

Abstract: Venom samples separately collected at monthly intervals from three Crotalus atrox specimens as they aged from 2 to 22 months showed many quantitative changes of biological activities. But more important were qualitative changes of coagulation activity. Up to 8 months the venoms clotted fibrinogen solutions directly. At 9 to 10 months, plasma was clotted but not fibrinogen. Subsequently the venoms no longer clotted plasma. Qualitative venom changes with growth of snakes could explain some of the conflicting reports both on clinical aspects of snake bite in man and on experimental venom work. The findings emphasize the importance for clinicians dealing with snake bite to monitor the clot-quality of their patient's blood--a simple bedside test for defibrinogenation, no-clot indicating zero fibrinogen and speck-clot representing fibrinogen concentrations under 50 mg/100 ml. With strongly defibrinating venoms, non-clotting blood is a very sensitive sign of systemic envenoming. In contrast, the relatively feeble defibrinating activity of juvenile C. atrox venom suggests that, if the blood is non-clotting in C. atrox bites, this indicates the victim has received a potentially lethal or near-lethal dose of venom urgently requiring effective antivenom therapy. Language: en

Immunological features of kala-azar.

Abstract: Serum immunoglobulins, complement C3c, percentage of T and B cells, and skin reactivity to Leishmania were studied in ten cases of kala-azar. Immunoglobulin G was increased in a majority of these patients. The C3c level in two out of six patients tested was lower than normal. The percentage of T cells in peripheral blood of nine patients tested was reduced and in seven of these patients the percentage of B cells was elevated. After a full course of anti-kala-azar therapy the percentage of T and B cells remained the same in five patients studied. All the patients showed a negative skin reaction when they were tested with Leishmania antigen.

The Antileishmanial Activity of Lepidines

Abstract: A series of lepidines (6-methoxy-4-methyl-8-aminoquinoline derivatives) was studied in a hamster-Leishmania donovani model. Members of this class were found to have activity many-fold that of the standard, meglumine antimoniate (Glucantime). One of them, 8-(6-diethylamino-hexylamino)-6-methoxy-4-methylquinoline, designated WR 6026, when given orally was over 700 times as effective as the standard antimonial drug.

Heterogeneity of Culicoides variipennis field populations to oral infection with bluetongue virus.

Abstract: A standard colonized population (000 line) of Culicoides variipennis (Coquillett) was used as the control for comparing the infection rate (IR) responses of different field populations of the vector to oral infection with several strains of bluetongue virus (BTV) that belonged to four serotypes. Three field populations from Colorado and Oregon tested concurrently in 1969 were differently susceptible to three BTV strains representing three serotypes. The IR's of each of the three populations varied greatly for the three serotypes, and the lowest IR for each of two Colorado populations was for a different serotype. The IR's of different populations to the same BTV strain varied greatly, and the lowest and highest IR's for two serotypes with adequate virus concentration occurred in different populations. Two Kentucky field populations in 1971 were completely resistant to oral infection with a BTV strain; in 1972, one population remained resistant and the other became moderately susceptible. The IR's of different field populations in 1971 to a single BTV strain ranged from 0 to 68%. The IR's of an Idaho population to three BTV strains representing three serotypes showed that a susceptibility rate (SR) could be calculated if the IR's were similar for one and for two infective blood meals. The average SR of this population was 42%; the SR's to each serotype were 32%, 40%, and 54%, with the highest response for the serotype that included the BTV strain collected during the BT outbreak from which the vector population was also collected.

An epidemic of yellow fever in Central Brazil, 1972-1973. I. Epidemiological studies

Abstract: An epidemic of jungle yellow fever occurred in Goias State, Brazil, between December 1972 and March 1973. Laboratory confirmed cases were observed in 36 counties located in the central and southern parts of the State. Seventy-one cases were proved, of which 44 were fatal. The diagnosis was made on the basis of pathology, serology, and virus isolation. Besides yellow fever, malaria and viral hepatitis were present, and in two fatal cases there was malarial pigment in the liver in addition to the specific lesions associated with yellow fever virus infection. The fact that male patients strikingly outnumbered females (9:1) and that young adults were predominantly affected indicates that transmission occurred mainly inside or adjacent to the forests. The lack of cases in urban areas can be attributed to the absence of Aedes aegypti in these areas. Yellow fever complement-fixing antibody in high titers was found in 18 of 1,201 (1.4%) persons living in eight counties of the affected area. This finding suggests that at least 21,000 persons out of the 1.5 million rural inhabitants of the three districts where the epidemic occurred had been infected by the virus. The epidemic subsided following an intensive vaccination campaign, and the last four cases were observed in March 1973.