Showing papers in "American Journal of Tropical Medicine and Hygiene in 1983"

Quantitation of amastigotes of Leishmania donovani in smears of splenic aspirates from patients with visceral leishmaniasis.

Abstract: During a 20-month period, more than 500 splenic aspirations were performed in 89 patients with suspected or proven visceral leishmaniasis. The two complications which occurred (intra-abdominal bleeding and penetration of the intestine in one patient each) both resolved with conservative management. Parasite density in splenic aspirate smears was graded on a logarithmic scale from 0 (no parasites in 1,000 microscopic fields) to 6+ (greater than 100 parasites per microscopic field). Among 46 newly diagnosed and 17 relapsed or drug-resistant patients with visceral leishmaniasis, the average initial parasite grade was 4.35 +/- 0.92 (mean +/- SD) and 4.15 +/- 1.37, respectively. The grading system was useful in measuring the speed of response to treatment, and in distinguishing slow responders from nonresponders. This was especially valuable for managing patients with drug-resistant visceral leishmaniasis. The system also provided a means of comparing the efficacy of different treatment regimens, and for calculating the optimum duration of treatment.

Original antigenic sin in dengue.

Abstract: Sequential blood samples were obtained from eight Thai children before, during and 3-5 months after hospitalization for dengue shock syndrome. All patients experienced a secondary-type antibody response as evidenced by hemagglutination-inhibition antibody responses in acute and convalescent sera. Dengue 2 viruses were recovered from two patients. In their pre-illness blood sample, all children had monotypic neutralizing antibodies; five to dengue 1, two to dengue 3 and one to dengue 4. The highest neutralizing antibody titers in acute phase and late convalescent sera were to the initial infecting virus type. This report documents for sequential dengue infections the existence of an original antigenic sin antibody response. It may be possible to apply this phenomenon to identify initial dengue serotype infection in individuals experiencing secondary dengue infections, thus helping to clarify the antecedents to dengue shock syndrome.

Transovarial transmission of dengue viruses by mosquitoes: Aedes albopictus and Aedes aegypti

Abstract: Transovarial transmission of all four dengue serotypes was demonstrated in Aedes albopictus mosquitoes. The rates of such transmission varied with the serotype and strain of virus. In general, the highest rates were observed with strains of dengue type 1 and the lowest with dengue type 3. Surprisingly, despite the use of viral strains of the four dengue serotypes which gave the highest rates with Ae. albopictus, transovarial transmission was observed in Aedes aegypti only with dengue type 1, and then only at a relatively low rate. Five different strains of Ae. aegypti were employed, including one that was known to be relatively susceptible to oral infection with dengue viruses. The findings support the view that Ae. aegypti, while of major importance from the point of view of transmission of dengue to man, may be relatively unimportant in the overall natural history of dengue viruses.

Rapid identification of dengue virus isolates by using monoclonal antibodies in an indirect immunofluorescence assay.

Abstract: Type-specific monoclonal antibodies prepared against the four dengue (DEN) virus serotypes were evaluated for their ability to identify low-passage human and mosquito isolates from Jamaica and West Africa by an indirect immunofluorescence assay. Serotyped human isolates from Jamaican dengue fever patients included 12 DEN-1, two DEN-2, and five DEN-4 viruses. Viruses from West Africa included 84 DEN-2 mosquito strains as well as two DEN-1 and one DEN-2 from humans. Results obtained using the immunofluorescence assay were consistent with virus identifications obtained using the more classical but costly and time-consuming plaque-reduction neutralization test. More viral isolates and higher virus yields were obtained using the C6/36 clone of Aedes albopictus cells rather than LLC-MK2 (monkey kidney) cells. Dengue type-specific monoclonal antibodies detected prototype viral antigens 24-48 hours postinfection in C6/36 cells. This is the first time that monoclonal antibodies have been used to serotype low-passage flavivirus isolates.

Quinine loading dose in cerebral malaria.

Abstract: In cerebral malaria, the use of currently recommended doses of intravenous quinine may result in subtherapeutic plasma concentrations during the critical first 24 hours of treatment. A loading dose of quinine (20 mg/kg quinine dihydrochloride, equivalent to 16.7 mg/kg base, infused over 4 hours) proved a rapid and safe method of achieving plasma concentrations above the high minimum inhibitory concentrations for Plasmodium falciparum prevalent in Eastern Thailand.

Manual on Environmental Management for Mosquito Control With Special Emphasis on Malaria Vectors: 283 pages. World Health Organization, Geneva (WHO Offset Publication No. 66). 1982. Sw. fr. 22.-

Abstract: This WHO manual is the result of the collaborative effort of 11 principle contributors and 35 reviewers, all of whom are experts in various aspects of the control of mosquitoes by environmental management. In pooling their knowledge and experience they have produced a manual that is comprehensive in scope and accurate in detail. The manual consists of seven chapters, which are ordered in a fashion to educate and prepare the reader to apply the principles and methodology of environmental management for mosquito control. The introduction (Chapters I and II) recognizes goals and objectives of environmental management, reviews mosquito bionomics related to epidemiology and control, and defines advantages and effects of environmental management. Extensively detailed in methodology, Chapters III, IV and V deal with environmental modification measures, environmental manipulation strategies, and time-honored ways of reducing man-mosquito contact. Chapter VI deals with planning environmental management for mosquito control, presenting an orderly approach from problem definition to project evaluation.

Spirochetes in Ixodes dammini and mammals from Connecticut.

Abstract: Spirochetes were observed in the midguts of 35% of 147 motile Ixodes dammini from three locations in Lyme and East Haddam, Connecticut. Positive ticks were removed from eastern chipmunks (Tamias striatus), raccoons (Procyon lotor), white-footed mice (Peromyscus leucopus), and a red squirrel (Tamiasciurus hudsonicus). Spirochetes were isolated in fortified Kelly's medium from nine questing or partially engorged I. dammini adults and nymphs and from the bloods of a raccoon and a white-footed mouse. Connecticut isolates from ticks and mammals were serologically indistinguishable from the original Shelter Island, New York strain when cross-tested by immunofluorescence against their mouse antisera. Sera from eight patients diagnosed as having Lyme disease contained antibodies to spirochetes isolated from ticks and mammals. Our finding of serologically and morphologically indistinguishable spirochetes in a raccoon, white-footed mouse and ticks suggests that closely related serotypes are present in wild mammals commonly parasitized by I. dammini, and further supports the claim that a spirochete is involved in the etiology of Lyme disease.

Cryptosporidiosis in hospital patients with gastroenteritis.

Abstract: Among 884 hospital patients with gastroenteritis, 36 (4.1%) were excreting Cryptosporidium oocysts in their stools; only 5 of the 36 patients were also excreting other enteropathogens, while none of 320 hospital patients without gastroenteritis were excreting Cryptosporidium oocysts. Children were more commonly infected with Cryptosporidium (4.8%) than were adults (1.6%). The prevalence of infection was higher (7%) during the summer period of February-May 1981 than in the remainder of the observation period to the beginning of June 1982 (1.9%). The most common clinical manifestation of gastroenteritis in Cryptosporidium-infected patients was diarrhea, lasting from 3 to over 14 days, accompanied by vomiting, anorexia, and abdominal pain. The results show that a small proportion of patients with gastroenteritis are infected with Cryptosporidium, and the importance of the infection needs to be examined.

Effects of antibiotics on Plasmodium falciparum in vitro.

Abstract: Evidence from in vivo experiments and clinical reports in humans has indicated that some antibiotics demonstrate antimalarial activity. Twelve antibiotics have been tested against Plasmodium falciparum in vitro, including cycloheximide, streptomycin, erthromycin, tetracycline, chloramphenicol, clindamycin, actinomycin D, rifampin, nalidixic acid, penicillin G, chlorhexidine, and isoniazid. Inhibitory effects obtained at various drug concentrations in vitro were compared to drug levels reported to be effective against bacteria in vivo. Several antibacterial drugs, including erythromycin, chloramphenicol, clindamycin, rifampin and tetracycline, demonstrated significant antiparasitic effects at concentrations within or near those observed during therapy in vivo; the potency of erythromycin and tetracycline was greater at 96 hours of exposure than at 48 hours.

Studies of Trypanosoma cruzi clones in inbred mice. I. A comparison of the course of infection of C3H/HEN- mice with two clones isolated from a common source.

Abstract: Two single-cell-isolate cloned stocks of the Sylvio-X10 strain, recovered from an acute human Trypanosoma cruzi infection, were used to infect C3H/HEN mice. The Sylvio-X10/4 clone produced a chronic infection in mice; clone Sylvio-X10/7 produced an acute lethal infection under identical experimental conditions. The course of infection of mice with the Sylvio-X10/7 clone was characterized by higher peripheral blood parasitemia and greater tissue involvement, an earlier appearance of specific anti-T. cruzi plasma IgG and shorter survival times than in mice infected with the Sylvio-X10/4 clone. The course of infection in mice with the Sylvio-X10 strain was intermediate between that of the two clones. This is the first demonstration of the pluripotential pathogenetic nature of a T. cruzi strain due to genetic heterogeneity of the population of parasites that constitute the strain. This experimental system is highly stable and reproducible. Consequently, the use of inbred mice and T. cruzi clones appears to provide an excellent model to study factors which influence the course of Chagas' disease.

Transovarial transmission of dengue 2 virus by Aedes aegypti in nature.

Abstract: Dengue 2 virus was recovered from three of 123 pools of naturally infected Aedes aegypti larvae (6,200 insects) collected from water containers in Rangoon. The virus was also isolated from two of 76 pools (7,730 mosquitoes) of male Ae. aegypti, collected as larvae and reared in the laboratory to adults. Minimum field infection rates among these two groups of mosquitoes were 1:2,067 and 1:3,865, respectively. Insect pools were inoculated into Toxorhynchites splendens mosquitoes and dengue viral antigen was subsequently detected in headsquash preparations by direct fluorescent antibody technique. Identification of the dengue serotype was done by complement-fixation test. This is the first report of dengue virus isolation from naturally infected mosquito larvae. These findings suggest that transovarial transmission of dengue virus occurs in nature.

Immunofluorescent antibody test in American visceral leishmaniasis: sensitivity and specificity of different morphological forms of two Leishmania species.

Abstract: This study was designed to determine which morphologic form and species of Leishmania is most suitable for detection of antibody in sera from American visceral leishmaniasis (AVL) patients by the indirect fluorescent antibody test (IFAT). Promastigotes and amastigotes of Leishmania mexicana or Leishmania donovani chagasi were used as sources of antigen. A total of 70 sera, including 30 from AVL patients, 30 from healthy subjects and 10 from Chagas' disease patients, were used in the study. Titers of antibody up to a dilution of 1:64 were found with all four antigens. At a titer of 1:128, the sensitivity of the IFAT using L. d. chagasi promastigotes as a source of antigen was 100% and the specificity at a titer of 1:32 was 98%. Although the sensitivity of the amastigote forms was close to 100% at a similar titer, the specificity at a titer of 32 using the L. d. chagasi amastigotes was 91% and using L. mexicana amastigotes was only 80%. The L. d. chagasi promastigote antigen was also the one that showed less cross reaction with sera from Chagas' disease patients. Since cross reactivity between Trypanosoma cruzi and Leishmania species is well known in serological tests, and minimizing of such cross reactivity is of critical importance for diagnosis, we suggest that L. d. chagasi promastigotes should be the antigen of choice for diagnosis of visceral leishmaniasis by IFAT in areas also endemic for trypanosomiasis.

In vitro study of drug sensitivity of Plasmodium falciparum: evaluation of a new semi-micro test.

Abstract: A modification of Rieckmann's microtechnique was used to determine the drug sensitivity of Plasmodium falciparum. The technique was found to be reliable and adequately sensitive with either blood from a malarial patient or strains of P. falciparum from in vitro continuous culture, with a success rate of 50%. Minor variations in the method had little influence on the results. Inhibition of maturation of parasites was compared with the inhibition of increase in parasitemia.

Effect of temperature of extrinsic incubation on the vector competence of Culex tarsalis for western equine encephalomyelitis virus.

Abstract: Culex tarsalis was a less competent vector of western equine encephalomyelitis (WEE) virus after 2-3 weeks' extrinsic incubation at 32 degrees C than after incubation at 18 degrees or 25 degrees C The high temperature itself was not directly detrimental to mosquito infection as all mosquitoes were initially infected, but subsequently some females were able to limit viral multiplication and/or dissemination Elevated maintenance temperatures enhanced the expression of modulation, and elevated larval rearing temperatures selected for those females with this trait This is the first report of an inverse relationship between temperature of extrinsic incubation within the range of 25 degrees-32 degrees C and vector competence of a mosquito for an arbovirus

The Effect of Laboratory Colonization on the Vector-Pathogen Interactions of Egyptian Culex pipiens and Rift Valley Fever Virus

Abstract: : Field and laboratory findings implicated Culex pipiens as a vector of Rift Valley fever (RVF) virus during the 1977-1978 epizoodtics/epidemics in Egypt. This study evaluated changes in infection and transmission rates, and viral titters in F sub 1 through F sub 16 generation Cx. pipiens mosquitoes orally infected with RVF virus. Infection and transmission rates of RVF virus by this species changed significantly during the colonization process. However, the ultimate viral titers of either the transmitting or the infected nontransmitting mosquitoes were not affected by the colonization process. Following ingestion of virus, Cx. pipiens could be separated into three distinct subpopulations, an uninfected group and two types of infected mosquitoes - transmitters and nontransmitters. Transmitters contained significantly more virus (approximately 100-fold) than nontransmitters. These results demonstrated that not every infected female mosquito should be considered a competent vector, even if the species (population) is known to be a primary vector. Transmission was also accomplished by probing mosquitoes which were unsuccessful in obtaining a blood meal. These data document the long-held suspicion that vector competence studies based upon laboratory-colonized specimens may not represent the field situation.

Case-control study of Mastomys natalensis and humans in Lassa virus-infected households in Sierra Leone.

Abstract: Lassa virus infection and antibodies were studied in households where Lassa fever cases occurred, and compared to those in nearest neighbor houses and "far" houses located across the village from case houses. Seventy-nine percent of all rodents caught in the houses were Mastomys, the natural reservoir of Lassa virus. Rodent infection was not randomly distributed, but rather focal. Thirty-nine percent of the Mastomys in case houses were viremic, compared to 3.7% in control houses. Human antibody prevalence in case houses was 30%, compared to 20% in non-case houses (P less than 0.05, chi-square test, df = 2). Neither seroconversions nor antibody prevalence rates were associated with household size or number of persons per room. Trapping of rodents in half of the case and control houses resulted in a Mastomys reduction ranging from 2.2- to 3.3-fold. This reduction failed to significantly reduce the seroconversion rate to Lassa virus in the people of trapped houses compared to those in untrapped ones. More complete trapping will be needed in order to better evaluate this procedure as a means of interruption of Lassa virus transmission in endemic villages.

Diagnostic criteria for scrub typhus: probability values for immunofluorescent antibody and Proteus OXK agglutinin titers.

Abstract: The sensitivities and specificities of the indirect microimmunofluorescent antibody (IFA) and Weil-Felix (OXK) tests for scrub typhus were established for a range of titers using groups of diseased and control (other febrile illnesses) patients diagnosed by other methods. At a cut-off point of greater than or equal to 1:400, the IFA test was 0.96 specific, and at greater than or equal to 1:320, the OXK was 0.97 specific. Using either these highly specific levels of antibody or other rigorous diagnostic criteria (isolation or 4-fold rising titers), the prevalence of scrub typhus infection was determined to be 0.22 in an unselected population of febrile patients in a rural Malaysian hospital. Probability values (Pr) for the correct diagnosis of scrub typhus were then calculated from the specificity, sensitivity and prevalence determination for a range of titers. The Pr for an OXK titer of greater than or equal to 1:320 was 0.79, and the Pr for an IFA titer of greater than or equal to 1:400 was 0.78. When both these titers were present in a single specimen, the Pr increased to 0.96.

Retinal hemorrhage, a common sign of prognostic significance in cerebral malaria

Abstract: Retinal hemorrhages were seen in 21 patients among a group of 144 with strictly-defined cerebral malaria. Hemorrhages were multiple in 17 cases and bilateral in 14. There was subhyaloid extension in two. Soft exudates were seen in two, the retinae were considered edematous in four and in one there was bilateral papilledema. Retinal hemorrhages were significantly associated with several indices of severity of Plasmodium falciparum infection: high parasitemia with schizontemia, anemia, elevated serum creatinine and reduced plasma antithrombin III. Only two patients with hemorrhages were both severely anemic and thrombocytopenic. It is suggested that retinal hemorrhages, a frequent finding in cerebral malaria, may be visible evidence of vascular lesions involved in the pathogenesis of this condition.

In vitro cultivation of the exoerythrocytic stage of Plasmodium berghei in a hepatoma cell line.

Abstract: When inoculated with sporozoites of Plasmodium berghei, a line of hepatoma cells (HepG2-A16) derived from human liver supports the complete asexual developmental cycle of the exoerythrocytic stage Parasites were shown to resemble parasites in vivo in hepatocytes Subinoculation of merozoites into mice induced a red blood cell infection

Circulating Immune Complexes and Rheumatoid Factor in Schistosomiasis and Visceral Leishmaniasis

Abstract: Circulating immune complexes, measured by the C1q binding and Raji cell radioimmunoassays, were detected in 16 of 25 (64%) patients with schistosomiasis alone, in all 13 patients (100%) with schistosomiasis infection associated with prolonged bacteremia by salmonella organisms, and in 15 of 18 (83%) patients with visceral leishmaniasis. The C3 levels in the serum of patients with schistosomiasis, with and without prolonged salmonella bacteremia, were significantly lower in those with renal disease. Further, in patients with schistosomiasis alone, the absence of renal involvement was positively associated with C1q binding within the normal range (P = 0.015) and the presence of IgM rheumatoid factor in serum (P = 0.04). In six of eight patients with visceral leishmaniasis treated with a pentavalent antimonial, there was a fall in Raji cell binding, suggesting indirectly that the parasitic antigen may be involved in the pathogenic immune complexes in serum.

Anisakiasis in the western United States: four new case reports from California.

Abstract: Four cases of transient anisakiasis in northern California acquired by ingestion of raw fish were reported to health authorities between May 1977 and June 1980. A single Phocanema decipiens-like 4th-stage (L4) larva was identified in each of two cases. A recently molted adult male P. decipiens with a fragment of attached L4 cuticle and prominent caudal papillae was recovered from a third person. The latter is the only human case known in which an anisakid worm developed to the adult stage was involved. Two Anisakis type I larvae were recovered in the fourth case, being the first parasitologically confirmed case of human infection with this worm described from the coterminous United States. Differential diagnosis was based on cuticular characteristics of larval types and stages as well as the presence of major internal organs. All infections were acquired during May and June. Subjects were 25-37 years old; three were female; two were of Japanese and one of Polynesian ancestry. Raw salmon or raw "red snapper" (probably Sebastes sp.) was the presumptive source of worms in one case each. Mild stomach pain and nausea were noted from the time of ingestion for up to 20 hours after the infective meal; worms were coughed up or found in the mouth up to 2 weeks thereafter. Five other incompletely documented California cases are discussed.

Development and persistence of antibodies to Entamoeba histolytica in patients with amebic liver abscess. Analysis of 216 cases.

Abstract: The antibody patterns--obtained by enzyme immunoassay (EIA), complement fixation (CF), indirect hemagglutination (IHA), and latex agglutination (LA)--of 216 patients with amebic liver abscess (ALA) were related to the time of onset of illness and to epidemiological data. The usual period between the stay in an Entamoeba histolytica-endemic area and clinical manifestation of the disease was 8-20 weeks. Increasing antibody concentration affected the sensitivity rates for CF and LA in the first 3 weeks of clinical ALA. In comparison with CF, IHA, and LA, EIA was the most sensitive test, showed the most substantial changes in antibody concentration according to the stage of disease, and measured persisting antibodies for the longest period. Neither the duration of previous stay in tropical countries nor the time when specific chemotherapy was started influenced development or persistence of antibodies in ALA patients. ALA occurred with similar frequency regardless of whether the patient was a long-term resident of the tropics or a short-term visitor to an E. histolytica-endemic area.

An enzyme-linked immunosorbent assay (ELISA) for field diagnosis of visceral leishmaniasis.

Abstract: A simplified enzyme-linked immunosorbent assay (ELISA) was evaluated as a diagnostic test for visceral leishmaniasis in the field on 222 individuals with splenomegaly and 110 controls The test was shown to have a sensitivity of 984% and specificity of 100% when compared with parasite identification by splenic aspiration The data indicate that the ELISA is an accurate, safe, and economical alternative to splenic aspiration for the diagnosis of visceral leishmaniasis

An Active Intermediate Host Role for Man in the Life Cycle of Echinococcus Granulosus in Turkana, Kenya

Abstract: Hydatid material removed at operation from 97 Turkana was compared for fertility and viability with hydatid material removed from camels, cattle, sheep, and goats. The results showed that the human material was extremely fertile and viable, as was material from the camels, goats, and sheep. Cattle cysts were invariably sterile, and the protoscoleces, when present, were comparatively less viable. The high incidence and fertility of hydatid cysts in the Turkana, together with the lack of burial customs thus allowing dogs to have ready access to infected human corpses, means that the Turkana are potential biological participants in the cyclic transmission of Echinococcus granulosus in this region. This is a unique situation, for elsewhere in the world man is regarded as an accidental host who plays no role in the parasite's life cycle.

Crimean-congo hemorrhagic fever in South Africa.

Abstract: Crimean-Congo hemorrhagic fever virus was isolated for the first time in South Africa in February 1981, from the blood of a 13-year-old boy who died in Johannesburg after attending a camp in a nature reserve in the western Transvaal. Virus was isolated from 21/120 pools of questing ticks from the nature reserve, the infected species being Hyalomma marginatum rufipes and H. truncatum. Virus was also isolated from 4/38 pools of partially engorged ticks and other ectoparasites collected off hosts, the infected species being H.m. rufipes, H. truncatum and Rhipicephalus evertsi. Antibodies were found in the sera of 5/74 humans, 8/26 wild vertebrates, 74/270 sheep, and 109/170 cattle from the reserve and surrounding farms. Antibodies were also found in 28/200 hares from various locations in the country. It was concluded that the virus is widely prevalent in South Africa, but the full medical and veterinary significance of its presence has yet to be determined.

Late metastatic Leishmaniasis in the mouse. A model for mucocutaneous disease.

Abstract: BALB/c, C57B1/6 and (BALB/c x C57B1/6)F1 mice all proved susceptible to infection by a strain of Leishmania isolated from a Central Brazilian with espundia The course of disease differed markedly between BALB/c and C57B1/6 mice BALB/c mice suffered from a rapidly progressive and widely metastatic, but non-ulcerative, disease resembling diffuse cutaneous leishmaniasis In contrast, C57B1/6 mice initially contained parasite multiplication effectively and appeared clinically cured However, the parasite could persistently be cultured up to about 1 year post-infection At that time, the parasite load in the infected footpad increased and a patent disease developed characterized by distinctive ulcerative metastases with destruction of soft-tissue in the nasal region similar to the one observed in espundia Development of disease in both strains of mice was associated with depression of cell-mediated immunity as monitored by delayed-type hypersensitivity in vivo and lymphocyte transformation in vitro Thus, our study suggests that diffuse cutaneous leishmaniasis and espundia can be caused by the same strain of parasite, and that the particular clinical expression in the individual mouse is determined by the host response

Identification of Leishmania spp. by multiple isozyme analysis.

Abstract: Biochemical data as enzyme profiles which were obtained by cellulose acetate electrophoresis (CAE) are reported on 44 Leishmania isolates. These enzyme profiles contain data from 25 enzyme systems. Calculations from the CAE data on average polymorphism indicated that Leishmania species/types or groups can be expected to be about 25% polymorphic, which suggests that isolate pairs which have profiles about 75% or more identical should be considered samples from the same species/type, and isolates that are significantly less than 75% identical are therefore samples from different species/types. There were five major groupings of isolates according to enzyme profiles, which were for the most part consistent with groupings of the genus based on other criteria: braziliensis, mexicana, donovani, tropica and hertigi profiles. Within these groups there were natural subgroups of isolates among which there was 75% or more allozyme or allomorph (genetic) identity. The braziliensis profile group had two subgroups: panamensis and braziliensis or guayanensis, and the mexicana profile group had three subgroups: mexicana, amazonensis and peruviana. There was an indication that an L. d. infantum isolate might be different from the other L. donovani isolates, and that the L. tropica isolates could be samples from more than one group. The data reported here are consistent with previously reported CAE data, but suggest that isozyme analysis of Leishmania isolates leading to identification should be based on data from many enzyme systems rather than just a few.

RNA fingerprinting as a method for distinguishing dengue 1 virus strains.

Abstract: : Virion RNAs of 12 geographically distinct dengue type 1 (DEN-1) virus isolates were clearly unique by RNA fingerprinting. Isolates from the same geographic area were very similar but differed from those of other areas, allowing us to establish three geographical groupings based upon percent shared oligonucleotides. Three Caribbean strains were virtually identical (85-91% homologous oligonucleotides) whereas Pacific/S.E. Asian strains exhibited considerably less homology to one another (44-49%). The Pacific/S.E. Asian strains exhibited little relationship (20-30%) to the Caribbean and African strains. A Sri Lankan isolate displayed a relatively high degree of homology to Nigerian isolates (60-66% homologous oligonucleotides), suggesting that the Sri Lanka DEN-1 infection originated from Africa. A 1978 Nigerian DEN-1 isolate and the 1969 Sri Lankan strain each exhibited greater than 50% homology with a 1977 Jamaican strain. The similarities observed between the African/Sri Lankan and Jamaican strains suggest that the DEN-1 virus which caused the 1977 Jamaican epidemic may have originated from Africa or Sri Lanka. The RNA fingerprint is a unique characteristic of DEN-1 strains from a particular geographic region, suggesting this technique as a useful tool for dengue epidemiological investigations.

Vertebrate hosts and vectors of Trypanosoma rangeli in the Amazon Basin of Brazil.

Abstract: A total of 46 Trypanosoma rangeli stocks were isolated from naturally infected mammals and triatomine vectors. Twenty-two stocks were from the common opossum (Di- delphis marsupialis), one from the brown "4-eyed" opossum (Metachirus nudicaudatus), one from the anteater (Tamandua tetradactyla), one from the coati (Nasua nasua), seven from Rhodnius pictipes and 14 from Rhodnius robustus. Two stocks were also isolated from recently fed sandflies (Lutzomyia sp., Shannoni group). The stocks were identified as T. rangeli on the basis of natural or experimental salivary gland infections in Rhodnius, inoc- ulative (anterior station) transmission to mice, morphological parameters in parasitemic mice and com pari sons of isozyme profiles with a known stock of T. range li isolated from mano Three other trypanosome stocks from D. marsupialis, T. tetradactyla and the three-toed sloth (Bradypus tridactylus) were morphologically similar to T. range li in culture but had quite different isozyme profiles and were not identified. It is concluded that T. rangeli is widely distributed in Amazonas, Para and Rondonia States of Brazil, and probably extends into other regions where R. pictipes and R. robustus are known to occur. R. pictipes is light-attracted into houses and occasionally transmits Chagas' disease to mano It is likely that T. range li is also occasionally transmitted to man in the Amazon basin.

Neuropharmacology of the parasitic trematode, Schistosoma mansoni.

Abstract: Neuropharmacological studies of Schistosoma mansoni were conducted in vitro using visual observations of motor activity and measurements of worm length and extracellular electrical activity. The instrumentation and methodology described quantitatively measure extracellular electrical potentials associated with motor activity, and provide a highly sensitive, objective technique for studying effects of antischistosomal compounds and for evaluating schistosomes as a model for neuropharmacological investigation. The visual motor and electrical responses of schistosomes to various pharmacological agents support earlier claims for the presence of an excitatory tryptaminergic system and an inhibitory cholinergic system. The stimulation of motor activity by 5-hydroxytryptamine was blocked by the antagonists metergoline and cyproheptadine in a dose-dependent manner. The hypermotility induced by cholinergic blockade (atropine or mecamylamine) or 5-hydroxytryptamine release (p-chlorophenylethylamine) was abolished by these antagonists. The cholinomimetic agents, acetylcholine, carbachol and arecoline, and the cholinesterase inhibitors neostigmine and metrifonate, caused a flaccid paralysis of schistosomes. Carbachol-induced paralysis was reversed by both the nicotinic cholinergic blocker, mecamylamine, and the muscarinic cholinergic blocker, atropine. This reversal occurred in a dose-dependent manner. It is suggested that the cholinoceptive site in S. mansoni has unique pharmacological properties, distinctly different from those in mammals. Dopamine, apomorphine, epinephrine and norepinephrine had little effect on schistosome motility, but produced marked increases in worm length. The dopaminergic antagonist, haloperidol, completely blocked the dopamine response. A broad range of putative amino acid neurotransmitters failed to alter schistosome motor activity. The simple nervous system of the schistosome appears to have many unique pharmacological features which may make it a useful model for the study of drugs for human use, as well as providing an effective point for chemotherapeutic attack.