Showing papers in "American Journal of Tropical Medicine and Hygiene in 1991"

Parasitologic and clinical human response to immunoglobulin administration in falciparum malaria.

Abstract: The protective effect of African IgG antibodies against Plasmodium falciparum malaria was investigated by passive transfer in Thai patients. Sera from 333 African adults were collected in the Cote d'Ivoire and subjected to extensive screening. One hundred fifty-three samples were discarded for safety reasons, and IgG was extracted from those remaining under conditions allowing their use by the intravenous (iv) route. Eight Thai patients with P. falciparum parasitemia were treated by iv inoculation of the IgG: six with a 100 mg/kg dose given over three days, one with a single 20 mg/kg dose, and one with a single 200 mg/kg dose. To ensure a safety margin of at least 48 hours, subjects were chosen among patients having a recrudescent parasitemia following quinine treatment failure at the RI level. At that stage, symptoms were mild or absent and parasitemia was low but increasing (range 4, 200-9,000/microliters). The IgG pool exerted a profound, stage-specific, but non-sterilizing effect on each of the strains tested, and proved to be safe. Asexual parasitemia decreased by a mean 728-fold (range 46-1,086), while gametocytes were unaffected. Clearance of parasites and symptoms was as fast or faster than with drugs, and was consistent in the eight patients treated, suggesting that target antigens were equally expressed in geographically remote isolates. In peripheral blood smears, no mature forms were seen at any time during the followup, which does not support the hypothesis that reversal of cytoadherence occurred. After the disappearance of the transferred antibodies, recrudescent parasites from three patients were found to be susceptible to the same extent (mean decrease of 1,310-fold) to the same IgG preparation, indicating that selection of parasites able to escape the effect of antibodies had not occurred. No adverse side-effects were detected during the followup, which lasted one year.

Leishmaniasis in Bahia, Brazil: evidence that Leishmania amazonensis produces a wide spectrum of clinical disease.

Abstract: One hundred fourteen Leishmania isolates from patients with different clinical forms of leishmaniasis in the State of Bahia, Brazil, were characterized by indirect radioimmune binding assay using specific monoclonal antibodies (serodeme analysis). Seventy-five of these isolates were also analyzed by enzyme electrophoresis, based on 11 enzyme loci; parasite species were compared, according to their characteristic zymodemes, to those of WHO Leishmania reference strains. All isolates could be classified into one of three species: Leishmania amazonensis (n = 40), L. braziliensis (n = 39) or L. chagasi (n = 35). The most interesting information obtained from this study is the realization that L. amazonensis is capable of producing a wide spectrum of disease in humans. Infection with this parasite was associated with many different clinical presentations, including cutaneous leishmaniasis [CL] (20/49 cases), mucocutaneous leishmaniasis [MCL] (5/13 cases) and, of special note, visceral leishmaniasis [VL] (11/46 cases), as well as four cases of post kalaazar dermal leishmaniasis [PKDL]. In situ tissue parasite characterization, by immunoperoxidase assay and employing anti-L. amazonensis amastigote monoclonal antibodies, confirmed the infection with this species in two cases of CL, one case of DCL, one case of MCL and one case of PKDL. Our results also demonstrate the difficulty of parasite differentiation based on clinical grounds, since at least L. amazonensis infection can be associated with all types of leishmanial diseases, and different Leishmania species may be associated with indistinguishable clinical presentations. Since leishmanial parasites may vary in their biological behavior or in their response to treatment, it is important that their identification be made by reliable methods.

Microvascular sequestration of parasitized erythrocytes in human falciparum malaria: a pathological study.

Abstract: Thirty-nine falciparum malaria autopsy cases from the Hospital for Tropical Diseases, Mahidol University, Bangkok, Thailand were divided into two groups that had had either cerebral malaria (CM) or non-cerebral malaria (NCM). We then studied significant pathological differences between these groups in order to investigate the correlation between parasitized erythrocyte (PRBC) sequestration in small blood vessels in the brain, heart, lungs and small intestines. We found that the percentage of PRBC sequestration in the organs which we studied was higher in the CM patients than in the NCM patients. The difference of PRBC sequestration among the organs of two groups was significant (P less than 0.05). In the CM group, the average percentage of PRBC sequestration in the brain was significantly higher than in the heart, lungs and small intestines (P less than 0.05). No statistically significant difference was found between PRBC sequestration in the brains, hearts, lungs and small intestines in the NCM group (P greater than 0.05). Our study indicates that severity of malaria in the CM patients depends on PRBC sequestration, especially in the brain. A combination of functional disturbances of the other organs, in addition to the cerebral pathology, may augment the severity of the disease.

Species-diagnostic differences in a ribosomal DNA internal transcribed spacer from the sibling species Anopheles freeborni and Anopheles hermsi (Diptera:Culicidae).

Abstract: Approximately 460 base pairs (bp) of DNA sequence that included the second internal transcribed spacer (ITS2) and some flanking 5.8S and 28S ribosomal RNA coding regions were compared between the two closely related and morphologically indistinguishable mosquito species Anopheles freeborni and A. hermsi and a third related species, A. occidentalis. Sequences were determined from 14 clones of polymerase chain reaction (PCR)-amplified DNA obtained from four colonies of A. freeborni, two colonies of A. hermsi, and one individual A. occidentalis. Four clones showed independent single bp differences from the consensus for the relevant species. Eleven sites differed between the consensus sequences of A. hermsi and A. freeborni; 28 sites differed between A. hermsi and A. occidentalis. With the exception of a single bp mismatch in the 5.8S and two single bp mismatches near the undetermined junction of the ITS2 and 28S regions, all differences were confined to the ITS2 region. A PCR-based species-diagnostic assay for the cryptic species A. hermsi and A. freeborni was developed; it uses four synthetic oligonucleotides, two derived from areas of interspecies sequence difference in the ITS2, and two derived from highly conserved regions in the flanking coding sequences. Small amounts of mosquito DNA amplified in the presence of these four primers produce fragments of diagnostic size for each species: 900 bp for A. freeborni, 350 bp for A. hermsi, and approximately 1.2-1.4 kb for various other Anopheles species tested. We believe that this general approach to the development of species-diagnostic assays can be extended easily to other complexes of closely related, morphologically indistinguishable species.

Resistance to chloroquine by plasmodium vivax in irian jaya, indonesia

Abstract: Evidence of emerging resistance to chloroquine by Plasmodium vivax is described from Irian Jaya (Indonesian New Guinea) Sixteen of 24 residents in the village of Arso PIR II taking supervised weekly chloroquine prophylaxis (5 mg base/kg) had asexual parasitemia with P vivax at least once during eight weeks of surveillance An American working in the same village developed symptomatic P vivax parasitemia despite chloroquine prophylaxis Five days after therapy with 600 mg chloroquine base, the asexual parasitemia in the American increased 40-fold, but cleared after treatment with 1,500 mg chloroquine base Serum samples were not available from many of the cases, but six local residents and the American had serum levels of chloroquine in excess of the ordinarily suppressive 15 ng/ml at the time of their asexual parasitemias (16-70 ng/ml) The weekly 300 mg base tablet of chloroquine, which has been the standard for prophylaxis against malaria for more than 40 years, was not effective against P vivax in Arso PIR, Irian Jaya

A modified agar plate method for detection of Strongyloides stercoralis.

Abstract: The agar plate method is a new technique with high detection rates for coprological diagnosis of human strongyloidiasis. This report details modifications of the technique and establishes a standardized procedure. We recommend that all plates should be carefully observed using a microscope because macroscopic observation can lead to false negative results. It is also advisable to pour formalin solution directly into microscopically positive dishes to collect worms by sedimentation. This procedure enables one to observe worms otherwise hidden. Sealing dishes with adhesive tape prevents larvae from crawling out of the dishes, eliminating any possibility in the reduction of detection rates, and greatly improves the safety conditions for the technician performing the procedure. We consider the agar plate method to be superior to the filter paper method in detecting Strongyloides, and we believe that it will eventually become the technique of choice.

Neuropsychiatric Side Effects after the use of Mefloquine

Abstract: This study describes neuropsychiatric side effects in patients after treatment with mefloquine. Reactions consisted mainly of seizures, acute psychoses, anxiety neurosis, and major disturbances of sleep-wake rhythm. Side effects occurred after both therapeutic and prophylactic intake and were graded from moderate to severe. In a risk analysis of neuropsychiatric side effects in Germany, it is estimated that one of 8,000 mefloquine users suffers from such reactions. The incidence calculation revealed that one of 215 therapeutic users had reactions, compared with one of 13,000 in the prophylaxis group, making the risk of neuropsychiatric reactions after mefloquine treatment 60 times higher than after prophylaxis. Therefore, certain limitations for malaria prophylaxis and treatment with mefloquine are recommended.

Age-dependent acquired protection against Plasmodium falciparum in people having two years exposure to hyperendemic malaria.

Abstract: An epidemiologic study of susceptibility to frequent and high-grade parasitemia by Plasmodium falciparum revealed that age-dependent acquired protection developed within a two-year period of exposure to hyperendemic infection pressure The study was conducted in a single village in northeastern Irian Jaya, Indonesia, where half the residents were native to the province and the other half were transmigrants from areas of Java, where there is little or no malaria transmission Five separate measures of susceptibility to the asexual parasitemia of falciparum malaria were derived from results of four months of biweekly surveillance of 240 volunteers Increasing protection as a function of age among the Javanese was a consistent pattern among the five estimates of susceptibility These age-dependent functions of protection were quantitatively parallel to those among life-long residents of Irian Jaya When humoral immune responsiveness to ring-infected erythrocyte surface antigen (RESA) was measured by ELISA, a similar pattern emerged; the relative level of antibody to RESA increased as parallel functions of age among the two subpopulations Acquired protective immunity against P falciparum was not the cumulative product of many years of heavy exposure to antigen Instead, the full benefit of protection appeared to develop quickly The degree of protection was governed by recent exposure and age, independent of history of chronic heavy exposure

Clustering of Malaria Infections within an Endemic Population: Risk of Malaria Associated with the Type of Housing Construction

Abstract: The occurrence of malaria infections due to Plasmodium vivax and P. falciparum was monitored in a population of 3,023 people living in six contiguous villages in Kataragama, an area of endemic malaria in southern Sri Lanka, over a period of 17 months. The annual incidence of malaria in this population during the study period was 25.8%. Malaria attacks were clustered, occurring more frequently than expected in certain individuals and housing groups and less frequently than expected in others. In one of these villages, the distribution of cases was examined in relation to locality and to the type of house construction. There was a strong association between the malaria incidence and house construction, independent of location. The risk of getting malaria was greater for inhabitants of the poorest type of house construction (incomplete, mud, or cadjan (palm) walls, and cadjan thatched roofs) compared to houses with complete brick and plaster walls and tiled roofs. Houses that were better constructed had a significantly lower malaria incidence rate (10.5%) than those that were poorly constructed (21.2%; P less than 0.01, by Student's t-test). There was also a significantly higher number of indoor resting mosquitoes collected from the poorly constructed houses than from those better constructed; the average (geometric mean) of mosquito densities found in houses of better versus poor construction were 0.97 and 1.89 per collection in the dry season, and 1.95 and 3.42 per collection in the wet season, respectively (P less than 0.05 in both seasons). This indicated that the higher malaria risk associated with poorly constructed houses was at least partly due to higher human-mosquito contact among their inhabitants.

An alga-like organism associated with an outbreak of prolonged diarrhea among foreigners in Nepal.

Abstract: An unidentified organism was found in the stools of 55 immunocompetent patients who presented to the CIWEC Clinic in Kathmandu, Nepal between June and November 1989. The microscopic features of the organism share characteristics of both coccidia and cyanobacteria species. From June 26, 1989 to November 17, 1989, 55 persons were identified as having the organism in at least one stool sample. The illness was characterized by prolonged watery diarrhea, anorexia, fatigue, and weight loss. The mean +/- SD duration of illness was 43 +/- 24 days (range 4-107). Thirty-four patients received a total of 78 courses of antimicrobial treatment (2.3 courses/patient). The mean +/- SD duration of illness in 34 treated patients was 46 +/- 24 days. In 14 untreated patients, the mean +/- SD duration of illness was 35 +/- 23 days. The organism is 8.0-9.0 microns in diameter, floats in Sheather's solution, and stains red with the modified acid-fast stain. Since the agent was closely associated with a prolonged, self-limited diarrheal illness, it could easily have been misdiagnosed as Cryptosporidium. The organism should be looked for in the stools of patients with persistent diarrhea and a history of foreign travel.

Successful immunization of humans with irradiated malaria sporozoites: humoral and cellular responses of the protected individuals.

Abstract: Two groups of volunteers were vaccinated by repeated exposure to the bites of Plasmodium falciparum-infected, x-irradiated mosquitoes in order to characterize the humoral and cellular immune responses of sporozoite-immunized, protected individuals. One of the two volunteers in the first immunization trial, when challenged by the bite of P. falciparum-infected mosquitoes, developed an infection only after a prolonged prepatent period. A second group of three volunteers who were exposed more frequently to larger numbers of infected mosquitoes irradiated with a lower x-ray dose was completely protected against sporozoite challenge. These individuals and the volunteer with delayed infection had high levels of antibodies to sporozoites and to the repeat region of the circumsporozoite (CS) protein. The CS-specific cellular immune responses of these volunteers were also stimulated by sporozoite immunization, as determined by proliferation of peripheral blood mononuclear cells (PBMC) and mitogen or antigen-expanded PBMC, in response to in vitro challenge with a recombinant P. falciparum CS protein. Based upon the assays used in this study, it is not possible to reach conclusions regarding specific immunologic responses and protection from sporozoite challenge.

Demonstration of yellow fever and dengue antigens in formalin-fixed paraffin-embedded human liver by immunohistochemical analysis.

Abstract: Two immunohistochemical techniques to determine the presence of yellow fever and dengue antigens in fixed tissue samples were developed for the purpose of making retrospective diagnoses of these viral diseases in humans. A horseradish peroxidase label was used for one technique and an alkaline phosphatase label for the other. In the former technique, acid hematin was removed from the tissues, iron-containing pigments were counterstained with Prussian blue, and the product of the diaminobenzidine reaction was enhanced with a dilute solution of osmium tetroxide that differentiated antigen from lipofuscin. In the latter technique, alkaline phosphatase was used as the enzyme labeling system with a red chromogen that contrasted nicely with the pigments in the tissues, as mentioned above. Thus, pigment removal or differentiation from antigen was not required. Replicate sections were cut and mouse polyclonal antibodies for yellow fever and all dengue types were applied to individual sections. On samples positive for dengue antigen, monoclonal antibodies were applied to additional replicate sections to demonstrate antigen of dengue types 1 and 4. In order to test the assay, samples of formalin-fixed liver tissue from Brazilian and Peruvian individuals who had died from a variety of causes as long as eight years earlier were received in a blinded fashion for immunohistochemical analysis. The techniques appeared to be highly reliable for yellow fever diagnosis; however, not enough cases were observed to adequately evaluate the procedures for dengue diagnosis. Both procedures appeared to have similar sensitivity.

Sensitivity and specificity of a universal primer set for the rapid diagnosis of dengue virus infections by polymerase chain reaction and nucleic acid hybridization.

Abstract: A set of sense and anti-sense oligomeric DNA primers, degenerate in the third "wobble" base position of codons so as to match all known dengue virus sequences, was evaluated as universal primers in a polymerase chain reaction (PCR) assay for the rapid diagnosis of dengue virus infections. Virus-specific complementary DNA (cDNA) was prepared by reverse transcription (RT) of total RNA extracted from serum. Amplified cDNA was identified by nucleic acid hybridization with four serotype-specific, oligomeric DNA probes. Using sera from patients admitted with dengue fever, RT/PCR followed by nucleic acid hybridization using radiolabeled probes was 68% sensitive (50/74; 95% confidence interval [CI] = 57-78%) and 100% specific. Chemiluminescent detection of hybridized products was 62% sensitive (26/42; 95% CI = 46-75%). Using specimens from which a virus isolate had been obtained, RT/PCR followed by nucleic acid hybridization with radiolabeled probes was 80% sensitive (40/50; 95% CI = 69-91%) and 100% specific. The results suggest that RT/PCR using degenerate primers is a sensitive and specific method for the detection of dengue viruses in clinical specimens.

DNA sequences for the specific detection of Cryptosporidium parvum by the polymerase chain reaction.

Abstract: The objective of this project was to construct specific and sensitive molecular probes and amplification primers for Cryptosporidium parvum that could be used in diagnosis, retrospective tissue studies, and in epidemiologic surveys. Whole genomic DNA was extracted from oocysts of C. parvum purified from human and bovine feces. A genomic library was constructed in plasmid pUC18 and propagated in Escherichia coli DH5 alpha. Transformants were screened by colony hybridization and autoradiography. The 2.3-kilobase segment in plasmid pHC1, a clone specific for C. parvum, was sequenced by the Sanger method. Computer analysis gave a G+C content of 35%. A 400-base region (bases 470-870) was selected as an amplification target because it contained a unique restriction endonuclease site that could serve as a useful marker. Primers of 26 nucleotides each were synthesized. Sensitive and specific amplification of the target sequence was demonstrated both by ethidium bromide staining of agarose and acrylamide gels, and by hybridization with chemiluminescence-labeled synthetic oligonucleotide probes.

Characterization and classification of leishmanial parasites from humans, wild mammals, and sand flies in the Amazon region of Brazil.

Abstract: Ninety-four leishmanial isolates from the Brazilian Amazon Region (Amapa, Amazonas, Para, and Rondonia) were identified and classified using specific monoclonal antibodies and an indirect radioimmunoassay (serodeme analysis); eighty-two were also characterized by enzyme electrophoresis (zymodeme analysis), the results of which were subjected to a numerical phenetic analysis. Six isolates from humans (3), Didelphis marsupialis (1), Lutzomyia olmeca nociva (1), and Lu. reducta (1) showed reactivity patterns and isoenzyme profiles similar to those obtained with the Leishmania amazonensis reference strains, and were identified as this species. Eighty-six stocks were classified as members of the L. braziliensis complex; of these, 61 were L. guyanensis or variants, which presented three serodeme subtypes, but whose isoenzyme profiles were all similar to the reference strain. A total of 15 isolates were distinguished as L. braziliensis or variants and were classified into five serodeme subtypes. The isolate from Psychodopugus davisi appeared, from the numerical analysis, to be a distinct parasite species. Ten isolates showed reactivity patterns and isoenzyme profiles similar to those obtained with the L. naiffi reference strain. A parasite isolated from Ps. claustrei appeared to be different from all reference strains by both techniques, and was classified as probably being a new species. The importance of these results with respect to the taxonomic status of the New World Leishmania, and their implications for both clinical and epidemiologic data are discussed.

Ultrasonographical investigation of periportal fibrosis in children with Schistosoma mansoni infection: reversibility of morbidity seven months after treatment with praziquantel

Abstract: Five hundred thirty six Sudanese schoolchildren with Schistosoma mansoni infection were treated at random with either 20 mg or 40 mg/kg praziquantel. Seven months later 420 children could be reinvestigated by ultrasonography. Reduction of egg excretion and reversibility of sonographically-proven periportal fibrosis (PF) was not significantly different in the two groups. Schistosoma mansoni-induced PF grade II decreased from 22.9% to 6.7% and grade III from 5.2% to 1.6%. An increased prevalence of PF grade I, from 10% to 29.8% of the investigated patients, was observed. This increase was caused partly by a downshifting of patients who had PF II (n = 45) and PF III (n = 8) before therapy, but also by patients who developed PF I in the seven months after therapy (n = 56). The overall percentage of patients with PF before and after treatment was 38.1%. Of 420 children, 17.4% increased in their PF grade, 55% remained at the same level and 27.6% improved. Children younger than 11 years of age had a higher rate of complete reversibility than older ones. The percentage of patients with hepatomegaly decreased significantly (11.6% to 6.9%; p = 0.001). The rate of splenomegaly remained unchanged. It was concluded that within seven months therapy with praziquantel resulted in a considerable qualitative improvement of PF in Sudanese schoolchildren with S. mansoni infection.

Human-rodent contact and infection with lymphocytic choriomeningitis and Seoul viruses in an inner-city population.

Abstract: We collected 1180 sera and 1363 questionnaires with information on demography, rodent exposure, and history of travel from persons visiting a sexually transmitted disease (STD) clinic in Baltimore between 1986-1988. Serological tests for two rodent-borne viruses detected antibodies to lymphocytic choriomeningitis virus (LCMV) in 54 individuals (4.7%; n = 1149) and antibodies to Seoul virus (SEOV) in three persons (0.25%; n = 1180). Antibody prevalence to LCMV increased with age, but there were no racial or sexual differences. Neutralization tests and questionnaire responses implicated a domestic, rat-borne hantavirus as the source of SEOV antibody. Self-reported human-rodent contact indicated more exposure to house mice than rats within residences, although rats were more commonly sighted on streets. Infections with rodent-borne viruses were rare compared to the high rates of reported contact.

Comparative susceptibility of anopheline mosquitoes in Rondonia, Brazil to infection by Plasmodium vivax.

Abstract: Seven anopheline species from Costa Marques, Rondonia, Brazil were compared with Anopheles darlingi for susceptibility to infection by Plasmodium vivax. Laboratory-reared F1 progeny of field-collected An. darlingi and the test anopheline species were fed at the same time on the same patients, all of whom had gametocytes in peripheral blood before treatment. Mosquitoes were dissected on day 8 after infection for oocysts and on days 14-16 after infection for sporozoites. The mean numbers of P. vivax oocysts and the percent of salivary gland infections for An. darlingi and An. deaneorum were similar and far exceeded those found in the other anopheline species tested. Anopheles albitarsis and An. mediopunctatus were less susceptible to infection by oocyst measurements than An. darlingi. However, for oocyst-infected An. albitarsis and An. mediopunctatus, the percent of mosquitoes with salivary gland infections and the numbers of sporozoites in the salivary glands were similar to An. darlingi. Anopheles triannulatus and An. oswaldoi were both susceptible to P. vivax infection, but the sporozoite infection rates and the numbers of sporozoites observed in the salivary glands were very low. Anopheles braziliensis and An. benarrochi both developed oocysts, but were never observed to have sporozoites in the salivary glands. These studies implicate some anopheline species as potential malaria vectors, but also show that species previously incriminated by ELISA techniques are not vectors of malaria parasites in Costa Marques, Rondonia, Brazil.

Central nervous system involvement during infection by Phlebovirus toscana of residents in natural foci in central Italy (1977-1988).

Abstract: Central nervous system (CNS) involvement was detected during infection caused by the sand fly-transmitted Phlebovirus Toscana. One hundred fifty-five cases of Toscana virus-associated meningitis or meningoencephalitis were identified in a survey that lasted ten years, conducted in two regions of central Italy. Diagnosis was performed by different serologic tests. A combination of hemagglutination-inhibition and plaque-reduction neutralization or indirect immunofluorescence for IgM, and enzyme-linked immunosorbent assays for IgM were considered the most suitable tests for the diagnosis of Toscana virus infection. A few strains of Toscana virus were isolated from the cerebrospinal fluid of seropositive patients. Toscana virus-associated CNS disease occurred during the summer, reaching a peak value in August, when the maximum activity of the sand fly vector occurs and virus isolates are obtained in their natural foci. The results suggest that Toscana virus should be considered as a possible cause of CNS disease in Mediterranean countries where sand flies of the genus Phlebotomus are known to be present.

Quantitation of Plasmodium falciparum sporozoites transmitted in vitro by experimentally infected Anopheles gambiae and Anopheles stephensi.

Abstract: The frequency and numbers of Plasmodium falciparum sporozoites transmitted in vitro and corresponding sporozoite loads were determined for experimentally infected Anopheles gambiae and An. stephensi. Geometric mean (GM) sporozoite loads in three experiments ranged from 808 to 13, 905 for An. gambiae and from 6, 608 to 17, 702 for An. stephensi. A total of 44.1% of 68 infected An. gambiae and 49.2% of 63 infected An. stephensi transmitted sporozoites in vitro. The GM number of sporozoites transmitted was 4.5 for An. gambiae and 5.4 for An. stephensi. Overall, 86.9% of the mosquitoes transmitted from one to 25 sporozoites, and only 6.6% transmitted over 100 sporozoites (maximum = 369). Sporozoite loads were not a useful predictor of potential sporozoite transmission. Despite higher sporozoite loads, the numbers of sporozoites transmitted in vitro by the experimentally infected mosquitoes were similar to estimates obtained, using the same techniques, for naturally infected An. gambiae in western Kenya. The low but highly variable numbers of sporozoites transmitted in vitro by mosquitoes used in malaria vaccine challenge studies appears to be a reasonable simulation of natural sporozoite transmission.

Antibodies against dengue viral proteins in primary and secondary dengue hemorrhagic fever.

Abstract: Antibodies against dengue viral proteins were demonstrated in sera from dengue-infected patients by polyacrylamide gel electrophoresis, Western blotting, and enzyme immunoassay. Primary dengue cases showed low titers of IgG class antibodies to envelope (E) proteins and two non-structural proteins, NS3 and NS5, in sera collected during the convalescent phase. Secondary dengue- infected patients always demonstrated IgG antibodies to E proteins in sera collected during the acute phase, and high titers of IgG antibodies to many other proteins, including NS1, NS3, NS5, and C proteins in sera collected during the convalescent phase. Appearance of antibodies to E, NS3, and NS5 could be detected within five days after the onset of fever. These three dengue viral proteins and their corresponding antibodies may be involved in the immunopathologic mechanism underlying this disease. For diagnostic purposes, identifying the non-structural proteins such as NS3 and NS5 may be the best means for early confirmation of the disease.

Leishmanin skin test standardization and evaluation of safety, dose, storage, longevity of reaction and sensitization.

Abstract: Leishmanin skin test (LST) antigens prepared from Leishmania braziliensis panamensis were compared with respect to sensitivity, specificity, and side effects. Within the dose range 0.5-3.0 x 10(5) promastigotes of L. b. panamensis and 10 x 10(5) promastigotes of combined L. amazonensis and L. b. panamensis, specificity in healthy controls was nearly 100% for all antigens. Sensitivity increased minimally with increasing dose. Lot-to-lot differences were small. Side effects, such as vesiculation and ulceration at the site of LST application increased with antigen dose. Storage under harsh conditions decreased LST potency but not sensitivity while storage at 2-8 degrees C affected neither potency nor sensitivity. Eighty-five percent of parasitologically diagnosed, LST-positive cases of leishmaniasis remained LST-positive when retested six months to three years later. The LST did not sensitive 19 healthy controls who were skin tested twice or thrice.

Epidemiologic study and control of Taenia solium infections with praziquantel in a rural village of Mexico.

Abstract: This study reports the results of an epidemiologic survey for the detection of Taenia solium in a rural village of 559 inhabitants in Sinaloa, Mexico, as well as a large scale treatment of the population with praziquantel. The study was carried out in two stages. In stage I, serial stool analysis of 392 persons detected a cluster of three T. solium tapeworms. A fourth T. solium tapeworm was detected through a household census, giving a 1.32% prevalence rate for this helminth. Over 70% of the population over five years of age was treated with a 10mg/kg dose of praziquantel, and no additional tapeworms were found. Environmental studies for the detection of Taenia sp. eggs in soil, water, and and objects from the houses of tapeworm-infected individuals showed only one soil sample containing eggs compatible with Taenia sp. A total of 72 domestic pigs were examined for the presence of cysticerci under the tongue. One animal had cysts, and belonged to a household that had two T. solium tapeworm infections. Stage 2 of the study was carried out one year after large scale antihelminthic treatment (LSAT), and no infections with Taenia sp. eggs were found. No cysticercus-infected pigs were detected. Intestinal parasitosis decreased from 69.2% to 37.5%. It is concluded that LSAT with praziquantel is efficient in decreasing endemic foci of T. solium. Seropositivity to T. solium bladder fluid antigens was tested by enzyme-linked immunosorbent assay and found to be 11% before LSAT and 7% one year later. In family members living with T. solium tapeworm carriers, the number of seropositive individuals was 28%. The relative risk ratio of seropositivity for persons living in the same household with a T. solium tapeworm carrier was 2.95. Positive response was significantly higher in the 30–39-year-old age group, in which 30% were seropositive in stage 1, compared with 7% one year after LSAT. High seropositivity rates were significantly associated with tapeworm clusters as well as with individuals with a clinical history of seizures.

Hosts on which nymphal Ixodes ricinus most abundantly feed.

Abstract: To identify hosts that may serve as European reservoirs for the agent of Lyme disease, Borrelia burgdorferi, we determined whether nymphal Ixodes ricinus feed mainly on particular mice (Apodemus flavicollis or A. agrarius), voles (Clethrionomys glareolus) or on sand lizards (Lacerta agilis) and whether the abundance of these hosts corresponds to the seasonal activity of the subadult stages of the vector tick. In all sites, the mice appeared most heavily infested by larvae; at least seven parasitized each mouse, about three per vole and four per lizard. Many fewer nymphal I. ricinus parasitized A. flavicollis and C. glareolus than did larvae. Although more than 30 times as many larval than nymphal ticks parasitized the two most abundant hosts (C. glareolus and A. flavicollis), about 15 times as many fed on A. agrarius and twice as many on lizards. Nymphal and larval ticks fed on rodents at about the same time. Lizards were most abundantly parasitized by nymphs somewhat earlier than by larvae. Early in the season of transmission of Lyme disease, virtually all A. agrarius as well as lizards were potentially exposed to spirochetes borne by nymphal I. ricinus. We concluded that larval and nymphal I. ricinus differentially parasitize different hosts. Because so many of these nymphs feed on them, A. agrarius may more effectively serve as reservoirs for the agent of Lyme disease than do other putative reservoir hosts. The presence of lizards may inhibit transmission.

Genetic selection of a flavivirus-refractory strain of the yellow fever mosquito Aedes aegypti.

Abstract: Two inbred (isofemale) Aedes aegypti mosquito lines were derived that manifested a resistant or susceptible phenotype following ingestion of yellow fever virus; lack of virus movement from the midgut defined the resistant phenotype. Other flaviviruses, including dengue 1–4, Uganda S, and Zika, viruses behaved in a similar fashion in the two mosquito lines. Crosses between the two lines produced progeny that were of intermediate susceptibility, indicating codominance; F2 backcrosses to the parents yielded results consistent with a major controlling genetic locus and provide evidence of a second locus capable of modulating the phenotype of the major gene. The rapid selection necessary to fix the susceptible and refractory phenotypes support the hypothesis of a single major controlling locus. Viral movement across the midgut is likely to be governed by a single major gene and modifying minor genes or a group of closely linked genes. These inbred mosquito lines will be useful in discovering the molecular basis for flavivirus resistance in Ae. aegypti.

Five cases of encephalitis during treatment of loiasis with diethylcarbamazine.

Abstract: Five cases of encephalitis following treatment with diethylcarbamazine (DEC) were observed in Congolese patients with Loa loa filariasis. Two cases had a fatal outcome and one resulted in severe sequelae. The notable fact was that this complication occurred in three patients hospitalized before treatment began, with whom particularly strict therapeutic precautions were taken, i.e., initial dose less than 10 mg of DEC, very gradual dose increases, and associated anti-allergic treatment. This type of drug-induced complication may not be that uncommon in highly endemic regions. It occurs primarily, but not exclusively, in subjects presenting with a high microfilarial load. The relationship between the occurrence of encephalitis and the decrease in microfilaremia is evident. The pathophysiological mechanisms are discussed in the light of these observations and the few other comments on this subject published in the literature.

Comparison of Regimes of Treatment of Antimony-Resistant Kala-Azar Patients: A Randomized Study

Abstract: Three hundred twelve patients with antimony-resistant kala-azar were randomized into three groups. The first group (A) received pentamidine isethionate intravenously three times each week until parasitological cure was achieved. Group B received pentamidine concomitantly with a 20-day regimen of sodium stibogluconate. Group C received pentamidine injections that were followed by 20 days of sodium stibogluconate therapy. All patients became afebrile after 10 injections of pentamidine. Parasitologic cure was achieved in approximately 98% of the patients who had 33 or more injections of this drug. The addition of the antimony compound did not appear to enhance the rate of parasitologic cure. Three patients continued to have parasites after 40 injections of pentamidine. After six months, the rate of parasitologic cure was significantly higher in Group C (pentamidine followed by sodium stibogluconate) than in either Group A or B. Forty patients relapsed after apparent parasitologic cure and were successfully treated with five additional injections of pentamidine, followed by a course of antimony therapy. Minor side effects with pentamidine included an uneasy feeling during intravenous injection (12%), intestinal disturbances (6%), cellulitis (5%), abscess formation (1%), and allergic manifestations (2%). Major reactions to this drug included hyperglycemia (10%; reversible in 6% and irreversible in 4%), and delayed hypoglycemia (8%). Four deaths were associated with the administration of this compound. It is concluded that pentamidine is an effective but toxic drug for the treatment of antimony-resistant kala-azar. When used, treatment schedules should be continued for some time after disappearance of amastigotes from bone marrow or spleen aspirates, rather than adhering to a fixed number of injections. Better results were achieved by pentamidine followed by a course of antimony, but no advantage was achieved by the simultaneous administration of the two drugs.

The number of sporozoites produced by individual malaria oocysts.

Abstract: Mature oocysts of Plasmodium falciparum and P. vivax from western Thailand were separated from the midguts of Anopheles dirus by collagenase digestion, and the number of sporozoites contained in each was counted. For 26 P. vivax oocysts, the mean count was 3, 688 (range 1, 954–5, 577) and for 14 P. falciparum, the mean count was 3, 385 (range 1, 359–4, 554); a single P. cynomolgi oocyst contained 7, 521. Counts were not significantly correlated with oocyst density, oocyst age, or identity of the examiner. There may have been strain differences in fecundity, particularly between P. falciparum lines maintained in vitro. Mosquitoes receiving a second, uninfected blood meal seven days after feeding on P. vivax-infected volunteers developed no additional sporozoites per oocyst, but had salivary glands 3.4 times as infected. By calculation, more than 20% of P. vivax sporozoites released from oocysts subsequently invade the salivary glands.

Comparative Susceptibility of Anopheline Mosquitoes to Plasmodium Falciparum in Rondonia, Brazil

Abstract: Five anopheline species, Anopheles deaneorum, An. albitarsis, An. triannulatus, An. oswaldoi, and An. mediopunctatus were compared to An. darlingi for susceptibility to infection by P. falciparum in Costa Marques, Rondonia, Brazil. Laboratory reared F1 An. darlingi and anopheline test species were allowed to feed at the same time on falciparum malaria patients who had gametocytes in their blood, and who had not yet been treated with quinine. Mosquitoes were dissected and examined for occysts on day 9, and for sporozoites on days 16–20 after feeding. Anopheles mediopunctatus had higher mean numbers of oocysts and oocyst positive rates than An. darlingi. The oocyst positive rate and the mean number of oocysts in An. deaneorum and An. darlingi were similar. Anopheles triannulatus and An. oswaldoi had fewer oocysts than An. darlingi. The salivary gland sporozoite infection rate was similar for An. mediopunctatus and An. deaneorum and much lower for An. triannulatus and An. oswaldoi when compared to An. darlingi. Anopheles albitarsis developed oocysts, but sporozoites did not invade the salivary glands. In relative levels of susceptibility to P. falciparum, An. darlingi was equal to An. mediopunctatus which was greater than An. deaneorum, which was greater than An. triannulatus, which was greater than An. oswaldoi.

Yellow fever: Victor, Victoria? Conqueror, conquest? Epidemics and research in the last forty years and prospects for the future.

Abstract: Yellow fever once ranked among the greatest of human afflictions, conquered attempts at colonial settlement and economic development, and caused epidemics with much suffering in towns and cities as far north as Boston and Swansea. The conquest of yellow fever began in 1900 with Walter Reed's decisive investigations that proved transmission of the virus by Aedes aegypti, expelled public fear and confusion about causation, and provided a practical recipe for combating the disease. By 1927, the yellow fever virus had been isolated. Within a decade, tests were generated for measuring human immunity, and the French neurotropic and 17D live, attenuated vaccines were developed. Although discovery of the jungle cycle of yellow fever transmission in 1935 dispelled hopes of ever eradicating the disease, widescale use of vaccines in the 1940s and systematic efforts to subdue Ae. aegypti brought yellow fever under control.