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Biomedical subjects

R B Tesh

Publications and source records attributed to R B Tesh.

At least 91 records · Page 5Linked to original sources
PubMed1989

Experimental infection of Old and New World phlebotomine sand flies (Diptera: Psychodidae) with Ascogregarina chagasi (Eugregarinorida: Lecudinidae).

The aseptate gregarine, Ascogregarina chagasi (Adler and Mayrink), found in a Colombian strain of Lutzomyia longipalpis (Lutz and Neiva), was fed to the larvae of seven species of laboratory-bred sand flies: Phlebotomus papatasi (Scopoli), P. argentipes Annandale and Brunetti, P. perniciosus Newstead, L. serrana (Damasceno and Arouck), L. abonnenci (Floch and Chassignet), L. columbiana (Ristorcelli and Van Ty), and a gregarine-free Brazilian strain of L. longipalpis. Trophozoites of the gregarine were recovered from adult sand flies of four species: P. papatasi, L. serrana, L. columbiana, and the Brazilian strain of L. longipalpis; the parasites were able to complete their life cycle only in the Brazilian strain of L. longipalpis. The infection rate and parasite density of A. chagasi were higher in the Colombian strain of L. longipalpis than in the Brazilian strain. Infection with A. chagasi significantly reduced adult longevity of the Brazilian strain of L. longipalpis, but it had little effect on fecundity.

Animals↗
PubMed1989

Transovarial transmission of Gamboa virus in a tropical mosquito, Aedeomyia squamipennis.

We report transovarial transmission of Gamboa virus (Bunyavirus) in Aedeomyia squamipennis, a tropical mosquito which is active and bloodfeeding throughout the year. Gamboa virus was isolated during each of the 28 months of the study from every mosquito stage, including eggs, demonstrating that vertical transmission is a maintenance mechanism of this virus. The overall minimum infection rate was 5.1/1,000 mosquitoes. Identification of the 567 isolates by neutralization indicated that greater than or equal to 2 serotypes or subtypes of Gamboa virus circulate at the study site.

Animals↗
PubMed1989

Identification, using isoenzyme electrophoresis and monoclonal antibodies, of Leishmania isolated from humans and wild animals of Ecuador.

Six strains of Leishmania isolated from wild mammals and humans on the Pacific Coast of Ecuador were identified by isoenzyme electrophoresis and by their reactivity patterns to a cross-panel of specific monoclonal antibodies using a radioimmune binding assay. Single isolates from Sciurus vulgaris, Potos flavus, and Tamandua tetradactyla were identified as Leishmania amazonensis. Three other strains, isolated from cutaneous lesions of humans, were identified as Leishmania panamensis.

Animals↗
PubMed1989

Ultrastructural biology of Leishmania (Viannia) panamensis (=Leishmania braziliensis panamensis) in Lutzomyia gomezi (Diptera: Psychodidae): a natural host-parasite association.

The development of Leishmania (Viannia) panamensis in a natural sand fly host, Lutzomyia gomezi, was studied by light and transmission electron microscopy. New aspects of peripylarian parasite behavior and morphology in the sand fly gut, early bloodmeal stages, and ultrastructural development in the anterior gut were documented. Eight distinct morphological forms were observed in the life cycle of the parasite within the insect. In the bloodmeal, amastigotes (1) transformed into stumpy promastigotes (2) which rapidly multiplied, resulting in spatulate-shaped nectomonad promastigotes (3) and elongate nectomonad promastigotes (4). These latter forms migrated primarily into the hindgut, where both were observed attached (=haptomonad phase) to the cuticular intima by hemidesmosomes within extremely shortened flagella. Spatulate haptomonad promastigotes predominated, colonizing the entire length of the hindgut, with the greatest density at 2 disjunct sites: the pylorus/ileum and the anterior rectum/rectal sac. Paramastigotes and dividing flagellates were rare. Some parasites migrated directly to the cardia/stomodeal valve region without a hindgut phase; however, major movement anteriorly was from the hindgut beginning at 6 days postinfection. In the cardia lumen, dividing short Type A promastigotes (5) predominated, intermixed with short Type B promastigotes with longer flagella (6). Paramastigotes (7) were free-swimming in the lumen as well as attached to the stomodeal valve. The primary colonizers of the valve were pear-shaped haptomonad promastigotes (8), with flagella of variable lengths and multi-segmented hemidesmosomal attachment points to the intima. Promastigotes and paramastigotes colonized the esophagus-pharynx region and attached to the foregut lining by flagellar hemidesmosomes. Both forms may represent infective stages of L. (V.) panamensis; however, no parasites were detected in the cibarium or proboscis. L. (V.) panamensis appeared well-adapted to the gut of Lu. gomezi, multiplying extensively at 2 sites, changing morphological form, and adhering to host surfaces by variously modified flagellar hemidesmosomes.

Animals↗
PubMed1989

Epidemiology of visceral leishmaniasis in Colombia.

Epidemiologic studies were conducted during the period 1986-1988 in a small rural community in Colombia (El Callejon) where visceral leishmaniasis is highly endemic. In this community of 185 people, 14 cases of infantile visceral leishmaniasis were diagnosed in the 9 years 1981-1988. Leishmanin skin testing of a sample of the human residents showed that prevalence of Leishmania chagasi infection increased with age; overall, 51.2% of the subjects had a positive reaction. A canine surveillance program was instituted, using introduced sentinel dogs as well as the indigenous dog population. Eleven of 16 sentinel dogs were infected within 8 months of exposure; mean seroconversion time was 4.4 months. Eleven of 25 seronegative local dogs were also infected during the 26 month period; mean seroconversion time was 8 months. Parasites identified by isozyme electrophoresis as L. chagasi were recovered from 18 of 22 seropositive dogs. Collections of wild animals using baited live traps yielded mainly the neotropical opossum, Didelphis marsupialis. Leishmania chagasi was recovered from 12 of 37 (32.4%) opossums. Six of 681 female Lutzomyia longipalpis collected in the community had flagellates in their guts; cultures from 4 were identified as L. chagasi. These data confirmed that active parasite transmission occurred. The relatively high prevalence of L. chagasi infection found among D. marsupialis captured near human dwellings suggests that these animals may be an important peridomestic reservoir.

Age Factors↗
PubMed1989

A review of the geographic distribution and epidemiology of leishmaniasis in the New World.

A review of the epidemiologic aspects of the New World leishmaniases, including their known geographic distribution, etiologic agents, zoonotic reservoirs, and insect vectors, based on biological and molecular characterization of Leishmania isolates is presented. Data summarized in this paper on parasite taxonomy and geographic distribution come from our studies of greater than 1,000 New World Leishmania isolates identified by species-specific monoclonal antibodies using an indirect radioimmune binding assay and from scientific literature.

Animals↗
PubMed1989

Characterization of five new phleboviruses recently isolated from sand flies in tropical America.

Five new phlebotomus fever virus serotypes (Bunyaviridae: Phlebovirus) are described. These viruses, designated Ambe, Ixcanal, Mariquita, Armero, and Durania, were isolated from sand flies (Diptera: Psychodidae) collected in Brazil, Colombia, and Guatemala. Two of the agents were recovered from pools of male sand flies. The new viruses are antigenically related to other members of the phlebotomus fever serogroup by immunofluorescence, but are distinct from the other 39 members of this serogroup by plaque reduction neutralization test.

Animals↗
PubMed1989

Ultrastructural development of Leishmania chagasi in its vector, Lutzomyia longipalpis (Diptera: Psychodidae).

The development of Leishmania chagasi, etiologic agent of American visceral leishmaniasis, was studied by light and electron microscopy in the gut of the sand fly, Lutzomyia longipalpis, a natural vector. New aspects of suprapylarian Leishmania behavior were elucidated. In the sand fly midgut, amastigotes transformed into promastigotes (division promastigote I) during a first division sequence within the bloodmeal. Secondary division of these promastigotes resulted in a second form (division promastigote II), and these subsequently elongated into nectomonad promastigotes. Nectomonads existed in long and short populations which divided in the bloodmeal and throughout the midgut lumen after escape from the peritrophic membrane. Nectomonads adhered to the midgut cells in a highly organized manner, with their flagella embedded deep into microvilli and cytoplasm. Migration of parasites from the posterior midgut into the cardia/stomodeal valve region at 36 hr was associated with breakdown of the peritrophic membrane anteriorly. Posterior breakdown at 48 hr resulted in a peritrophic tube open at both ends containing some parasites within the digesting bloodmeal for up to 6 days postinfection. At the stomodeal valve, a myriad of slender and rounded promastigotes attached to the intima by flagellar hemidesmosomes; these may represent a transformation sequence from slender nectomonads to pear-shaped haptomonads. Pear-shaped forms appear to be precursors of paramastigotes, which also attached to the valve intima. Both rounded haptomonads and paramastigotes were found in the esophagus, dividing in a complex sequence initiated by posterior cleavage of the cytoplasm producing unique heart-shaped forms. Dividing paramastigotes also colonized the pharynx up to the cibarial valve. The ultrastructure of paramastigotes suggested that they may be infective forms, capable of some motility in the foregut. Free-swimming "infective" promastigotes were observed throughout the midgut and foregut, were attached in the pharynx (armature region), and were associated with the labrum-epipharynx of the proboscis in 3.6% of flies (16 days). The fine structure of hemidesmosomes in the foregut showed regional specializations, including the presence of plasmalemmar bridges in the gap space.

Animals↗
PubMed1988

RNA genome stability of Toscana virus during serial transovarial transmission in the sandfly Phlebotomus perniciosus.

We have carried out a T1 ribonuclease fingerprinting analysis of the RNA genomes of Toscana virus isolates from successive generations of an experimentally virus-infected laboratory colony of Phlebotomus perniciosus sandflies. This analysis detected no virus RNA genome changes during transovarial transmission of the virus over 12 sandfly generations (a period of almost 2 years). These results demonstrate that although RNA viruses can exhibit high rates of mutational change under a variety of conditions, Toscana virus RNA genomes can be maintained in a stable manner during repeated transovarial virus transmission in the natural insect host. The implications of these results for insect RNA virus evolution are discussed.

Animals↗
PubMed1988

Intra- and inter-serogroup genetic relatedness of orbiviruses. II. Blot hybridization and reassortment in vitro of epizootic haemorrhagic disease serogroup, bluetongue type 10 and Pata viruses.

Viruses which belong to the epizootic haemorrhagic disease (EHD), bluetongue and Eubenangee serogroups of orbiviruses exhibit low level cross-reactions in some serological tests. Although Pata virus cross-reacts at low levels with members of the EHD and bluetongue serogroups, it was assigned originally to the Eubenangee serogroup. RNA-RNA blot hybridization data, however, suggest that Pata virus is not a member of the Eubenangee serogroup. In this study, the genetic relatedness of the EHD serogroup viruses, bluetongue virus type 10 (BTV-10) and Pata virus was assessed by RNA-RNA blot hybridization and by gene reassortment experiments in vitro. The five members of the EHD serogroup examined were highly related by reciprocal RNA RNA blot hybridization. Genes 1, 3, 4 and 6 to 9 were highly conserved with three unique types of gene 2, four variant types of gene 5 and two variant types of gene 10. Geographical boundaries could not be correlated with sequence relatedness because viruses isolated from the same locality were distant relatives when compared with another virus isolated on a different continent. The significance of the unique and variant genes is discussed. The EHD isolates, BTV-10 and Pata virus exhibited distinct profiles on agarose and polyacrylamide gel electrophoresis, and they are related distantly as shown by weak hybridization signals in blot hybridization. Gene 2 was a unique gene among the EHD isolates, BTV-10 and Pata virus. One BTV-10 gene hybridized more strongly to gene 9 of the EHD viruses than the other BTV-10 genes, and its role in encoding the cross-reactive antigen is discussed. Intra-serogroup gene reassortment in vitro was demonstrated in the six crosses among EHD serogroup members. In contrast, gene reassortment was not observed in inter-serogroup crosses between EHD 1 and BTV-10, BTV-10 and Pata virus, and between EHD 1 and Pata virus. Correlation of blot hybridization and gene reassortment indicated that viruses must share high sequence conservation in the majority of their genes before genetic interaction is likely. The usefulness of blot hybridization as an indicator of the likelihood of gene reassortment is discussed. These hybridization and gene reassortment data indicated that Pata virus is not a member of the bluetongue or EHD serogroups and that it should be assigned to the ungrouped set of orbiviruses. The hybridization and gene reassortment data suggest that members of the EHD serogroup, BTV-10 and Pata virus represent three distinct gene pools, and the role of reassortment in the generation of genetic diversity is discussed.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1988

Survival of albumin, IgG, IgM, and complement (C3) in human blood after ingestion by Aedes albopictus and Phlebotomus papatasi.

The levels of albumin, IgG, IgM, and complement (C3) were determined by enzyme-linked immunosorbent assay in Aedes albopictus and Phlebotomus papatasi at regular intervals after feeding on human blood. Albumin disappeared most rapidly; by 48 hr, detectable levels of albumin had decreased 100-fold. In contrast, IgG and IgM survived longer and were still detectable at low levels several days after ingestion. C3 was intermediate in its rate of degradation. In general, serum protein disappearance occurred more rapidly in Ae. albopictus than in Ph. papatasi, despite a larger volume of blood ingested by the former.

Aedes↗
PubMed1988

A human case of encephalitis associated with vesicular stomatitis virus (Indiana serotype) infection.

This paper describes a case of severe encephalitis in a 3-year-old Panamanian boy infected with the Indiana serotype of vesicular stomatitis virus. The virus was recovered from the child's throat on the fifth day of illness and a rise in neutralizing antibody titer was demonstrated in paired serum specimens. This is the second report of childhood encephalitis associated with vesicular stomatitis virus infection. These suggest that infection with vesicular stomatitis viruses may cause severe disease. Human infection with vesicular stomatitis viruses is common throughout the tropical Americas.

Child, Preschool↗
PubMed1988

Malpais spring virus: a new vesiculovirus from mosquitoes collected in New Mexico and evidence of infected indigenous and exotic ungulates.

Two virus isolates, 1 each from Aedes campestris and Psorophora signipennis mosquitoes collected in south central New Mexico in August 1985, were shown by neutralization tests to be identical to each other, but not to any of more than 250 arthropod-borne and other viruses. Electron microscopy of 1 isolate (85-488NM, chosen as the prototype) indicated that this strain shares morphologic characteristics with viruses of the family Rhabdoviridae. Indirect fluorescent antibody tests indicated that this virus is a member of the genus Vesiculovirus, but is not closely related to any of the North American or other rhabdoviruses with which it was tested, including vesicular stomatitis (Indiana) and vesicular stomatitis (New Jersey) viruses. The name Malpais Spring virus is proposed for this newly recognized vesiculovirus. A serologic survey indicated that Malpais Spring virus infects indigenous (mule deer and pronghorn) and exotic (gemsbok) ungulates at and near the sites where the mosquitoes from which the virus strains were isolated were collected. Antibody prevalence in wild animals indicates that the pronghorn and gemsbok may play roles as hosts for Malpais Spring, epizootic hemorrhagic disease (New Jersey), and bluetongue viruses in this area.

Aedes↗
PubMed1988

Effect of human gamma interferon on yellow fever virus infection.

We studied yellow fever virus infection in two species of monkey: Saimiri sciureus (squirrel monkeys) and Macaca mulatta (rhesus monkeys). Human gamma interferon was administered intravenously in five equal doses, one was given 24 hr before infection followed by four doses 24 hr apart. Interferon reduced the levels and duration of viremia and the severity of hepatitis in squirrel monkeys. Interferon prolonged survival time and delayed the appearance of viremia and hepatitis in infected rhesus monkeys, but it did not change overall mortality.

Alanine Transaminase↗