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Biomedical subjects

R B Tesh

Publications and source records attributed to R B Tesh.

At least 109 records · Page 6Linked to original sources
PubMed1987

A newly recognized vesiculovirus, Calchaqui virus, and subtypes of Melao and Maguari viruses from Argentina, with serologic evidence for infections of humans and horses.

In 1983, 17 virus strains were isolated from mosquitoes collected during an outbreak of western equine encephalitis in Santa Fe Province, Argentina. Strains of western equine encephalitis, Venezuelan equine encephalitis, St. Louis encephalitis, and Antequera viruses were isolated, as were several bunyaviruses of the California and Bunyamwera serogroups and a new vesiculovirus. Complement fixation and neutralization tests were used to identify the California serogroup virus as a subtype of Melao virus, the Bunyamwera serogroup virus as a subtype of both Maguari and Playas viruses, and the vesiculovirus as a newly recognized agent for which the name Calchaqui virus is proposed. A limited serosurvey of horses and humans in Santa Fe Province and horses from the adjacent Santiago del Estero Province was performed to determine the prevalence of neutralizing antibody to the subtypes of Melao and Maguari viruses and to Calchaqui virus. The high prevalence of antibodies to these three agents indicates the need for further studies of their disease potential in horses, because they are closely related to several other viruses that are known equine pathogens.

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PubMed1987

Maintenance of Toscana virus in Phlebotomus perniciosus by vertical transmission.

Toscana virus was maintained in a laboratory colony of Phlebotomus perniciosus by vertical (transovarial) transmission for 13 consecutive generations over a 23-month period. No significant biological changes were noted in the virus after prolonged vertical passage in the sand flies, and transovarially infected females were able to transmit the agent by bite to susceptible animals. Chronic infection of Ph. perniciosus with Toscana virus had no apparent effect on the insects' rate of eclosion. In the absence of selection and with random matings, the virus infection rates in each subsequent generation of the colony decreased, suggesting that Toscana virus cannot be maintained in Ph. perniciosus by transovarial transmission alone. Alternative mechanisms for virus maintenance are discussed.

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PubMed1987

Host-parasite relationship of Leishmania mexicana mexicana and Lutzomyia abonnenci (Diptera: Psychodidae).

The life cycle of Leishmania mexicana mexicana in the gut of the sand fly, Lutzomyia abonnenci, was studied by light and electron microscopy. Development was suprapylarian with initial establishment of parasites in the bloodmeal (posterior midgut), and anterior migration of parasites to the cardia/stomodeal valve region beginning at 2.5 days post-infection. Flagellates were first observed in the esophagus at 3.5 days, in the posterior armature region of the pharynx at 5 days, and in the anterior pharynx at 7 days; but they were not detected in the cibarium or proboscis. Infection of the pylorus region of the hindgut and of the Malpighian tubules was also commonly observed. Three different morphological forms of L. m. mexicana developed in the gut: nectomonad promastigotes, short promastigotes, and paramastigotes. Nectomonads occurred primarily in the abdominal midgut after bloodmeal digestion, where they were oriented in longitudinal masses in the lumen, or interdigitated with epithelial microvilli via the flagellum. Short promastigotes found in the cardia/stomodeal valve region are described for the first time. These forms were smaller than nectomonads, showed an amplification of the kinetoplast, apposition of kinetoplast and nucleus, and were embedded in a gel-like matrix. To maintain position in the cardia, parasites commonly inserted the flagellum deep into microvilli or cytoplasm of the epithelium; adherence to the cuticular intima of the stomodeal valve was by flagellar modification and formation of hemidesmosome plaques. Paramastigotes occurred in the esophagus, were sometimes degenerated in appearance, and were attached via flagellar hemidesmosomes. Paramastigotes observed in the lumen of the pharynx were commonly degenerated and were not attached to the intima. L. m. mexicana was able to colonize the various gut habitats of Lu. abonnenci by a number of adaptations; this sand fly appears to be a suitable biological host for the parasite.

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PubMed1987

Natural infection of humans, animals, and phlebotomine sand flies with the Alagoas serotype of vesicular stomatitis virus in Colombia.

Five isolations of the Alagoas serotype of vesicular stomatitis virus (Rhabdoviridae: Vesiculovirus) were made from naturally infected phlebotomine sand flies (Lutzomyia spp.) collected in Colombia. These are the first isolations of Alagoas virus from an arthropod. Replication of the virus occurred in laboratory-reared sand flies (Lutzomyia longipalpis) after inoculation. Bite and transovarial transmission of the virus was also demonstrated in experimentally infected sand flies. Alagoas virus neutralizing antibodies were found in sera of humans and animals living near the insect collection site; antibody rates among human residents of two nearby towns were 63% and 83%, respectively. Results of comparative serologic studies demonstrated that Alagoas virus is closely related antigenically to Indiana, Cocal, and Maraba viruses and that these four agents form a complex within the vesicular stomatitis virus serogroup. The antigenic similarity among these four viruses makes their differentiation difficult; it also raises doubts about the accuracy of current laboratory methods used for identifying isolates in this serogroup. A discussion follows on the significance of human antibodies to these agents and on the role of sand flies in their ecology.

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PubMed1987

Viremia and immune response with sequential phlebovirus infections.

Four groups of hamsters were infected sequentially with various combinations of Arumowot, Chagres, and Gabek Forest viruses. Following each infection, the survival, level of viremia, and immune response of the animals were monitored. All of the agents produced viremia in the hamsters, regardless of the order of their administration. The antibody response, as measured by plaque reduction neutralization test, was monotypic even after two consecutive phlebovirus infections. Arumowot and Chagres viruses produced nonfatal infections in adult hamsters, which were characterized by viremia of several days duration and subsequent antibody formation. In contrast, Gabek Forest virus produced a fulminating and rapidly fatal disease in phlebovirus nonimmune animals. In hamsters previously infected with Chagres and/or Arumowot viruses, Gabek Forest infection was less severe, indicating some degree of cross-protection. The degree of cross-protection was in part related to the sequence of previous phlebovirus infections. No evidence of immune enhancement or other immunopathologic events were observed in the animals.

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PubMed1986

Biology of Arboledas virus, a new phlebotomus fever serogroup virus (Bunyaviridae: Phlebovirus) isolated from sand flies in Colombia.

Six isolates of a new phlebotomus fever serogroup virus, designated Arboledas virus, were obtained from sand flies (Lutzomyia spp.) collected in northeastern Colombia. One of the isolates was made from a pool of male sand flies. By immunofluorescence, Arboledas virus is related to Caimito and Pacui viruses; by neutralization test, it is distinct. Arboledas virus neutralizing antibodies were found in the sera of opossums (Didelphis marsupialis) and humans living in the study area. D. marsupialis inoculated with the virus developed a viremia of four days' duration, and sand flies (Lutzomyia gomezi) feeding on a viremic opossum were readily infected. Transovarial transmission of Arboledas virus was also demonstrated in experimentally infected Lu. gomezi. Results of the above laboratory studies suggest that Arboledas virus is maintained in nature by two mechanisms: vertical (transovarial) transmission in the insect vector, and an alternating marsupial-sand fly cycle. The implications of this complex maintenance cycle for other phleboviruses are discussed.

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PubMed1986

Biological and antigenic characterization of Netivot virus, an unusual new Orbivirus recovered from mosquitoes in Israel.

The antigenic and biological characteristics of a new Orbivirus, designated Netivot virus, are described. This agent was originally recovered in cultures of the C6/36 clone of Aedes albopictus cells from a pool of Culex pipiens captured in Israel. Netivot virus is not pathogenic for newborn mice, nor did it initially produce detectable cytopathic effect (CPE) in Vero cells. It is closely related antigenically to Umatilla and Llano Seco viruses; these 3 agents appear to constitute a new serogroup within the genus Orbivirus. Netivot virus is also more distantly related to a number of other orbiviruses in the blue-tongue, epizootic hemorrhagic disease of deer, and Eubenangee serogroups. Netivot virus replicated to high titer and produced CPE in a variety of mosquito cell cultures, but it did not grow in 2 sand fly cell lines. Inoculation of Ae. aegypti and Ae. albopictus with Netivot virus resulted in almost 100% mortality in both species within 15 days after infection. The recovery of this and a number of other yet unidentified viral agents from field-collected mosquitoes in cultures of C6/36 cells, but not in the conventional vertebrate assay systems, suggests the existence in nature of many yet unrecognized mosquito-associated viruses. It also demonstrates the value of using new isolation methods in arbovirus studies.

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PubMed1984

Characterization of the Changuinola serogroup viruses (Reoviridae: Orbivirus).

The antigenic, biological, and chemical properties of 24 selected Changuinola serogroup viruses were examined. The viruses tested were chloroform-resistant, and they were lethal to newborn hamsters after intracerebral inoculation. The prototype Changuinola virus strain (BT-436) replicated in mosquito and sandfly cell cultures. In complement-fixation tests, the viruses were broadly cross-reacting and indistinguishable; but by neutralization test at least 12 distinct serotypes were identified, and by PAGE of double-stranded RNA 22 distinct profiles were found. These data suggest that the Changuinola serogroup may be comprised of a large number of genetically different viruses. A brief review of the natural history of Changuinola serogroup viruses is also given.

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PubMed1984

Characterization of the Palyam serogroup viruses (Reoviridae: Orbivirus).

31 Palyam serogroup viruses were examined by complement-fixation and plaque-reduction neutralization tests and by PAGE of the segmented, double-stranded (ds) RNA genome. Although the viruses were indistinguishable by complement-fixation tests, 10 distinct virus serotypes were identified by plaque-reduction neutralization methods. Palyam group viruses which were distinct by the neutralization test had unique dsRNA profiles, whereas those agents which were indistinct by the neutralization test had identical dsRNA profiles. 20 isolations of 3 Palyam serotypes were made from bovines and Culicoides midges in Australia over a 9-year period. When the genome of these isolates was examined electrophoretically, the dsRNA profiles of virus isolates within a given serotype were identical.

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PubMed1984

Studies on the biology of phleboviruses in sand flies (Diptera: Psychodidae). I. Experimental infection of the vector.

This paper describes a series of experiments which were done to determine the behavior of 14 different phleboviruses in laboratory-reared sand flies (Phlebotomus papatasi, P. perniciosus and Lutzomyia longipalpis) after oral and parenteral infection. Most of the viruses replicated in the sand flies after intrathoracic inoculation; however, the insects were quite refractory to oral infection. Six of 11 phleboviruses tested were transovarially transmitted in one or more sand fly species. The percentage of infected F1 offspring produced by parenterally infected female parents ranged from 1.5-60%, depending on the virus type used. These data support the hypothesis that some of the phleboviruses are maintained in sand flies by transovarial transmission.

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PubMed1984

Association of a Sindbis-like virus with Ockelbo disease in Sweden.

An alphavirus isolated from Culiseta mosquitoes has been associated with Ockelbo disease, an exanthema arthralgia syndrome occurring in Sweden. The isolate was made from mosquitoes collected in Edsbyn (central Sweden), an area with considerable Ockelbo disease morbidity. This isolate proved to be indistinguishable from Sindbis virus by complement-fixation and hemagglutination-inhibition tests, and was antigenically related to Sindbis in plaque reduction neutralization tests. Patients with Ockelbo disease developed neutralizing antibodies to the virus in their convalescent sera, suggesting that it is the etiologic agent of the disease.

Aedes↗
PubMed1984

A simple method for experimental infection of phlebotomine sand flies with Leishmania.

Mouse macrophages, grown in continuous cell culture at 37 degrees C, were inoculated with the promastigote stage of various human pathogenic Leishmania species. Under these culture conditions, the parasites rapidly entered the cells and transformed into amastigotes. Two or 3 days after inoculation, the infected macrophages were mixed with washed human erythrocytes and were fed to female sand flies (Phlebotomus papatasi and Lutzomyia longipalpis) through a chick skin membrane. Within 7-10 days after feeding, large numbers of promastigotes were observed in the anterior portion of the insects' guts, indicating that the infected sand flies were capable of transmitting the parasites by bite. This relatively simple and rapid technique should facilitate studies on the biology of Leishmania in their insect vectors. It also eliminates the need for animals as a source of amastigotes.

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PubMed1984

Carajas and Maraba viruses, two new vesiculoviruses isolated from phlebotomine sand flies in Brazil.

Two new rhabdoviruses, designated Carajas and Maraba, are described. Both were isolated from phlebotomine sand flies (Lutzomyia spp.) collected in the Amazon basin of Brazil. One recovery of Carajas virus was made from male sand flies. By complement-fixation and neutralization tests both agents were shown to be members of the vesicular stomatitis virus (VSV) serogroup (genus Vesiculovirus). The pathogenicity of the two viruses in mice and Vero cells is similar to that of VSV-Indiana and VSV-New Jersey. Both Carajas and Maraba viruses replicated in Lutzomyia longipalpis following intrathoracic inoculation, and both agents were transovarially transmitted in this sand fly species.

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