Interspecific larval competition between Aedes albopictus and Aedes japonicus (Diptera: Culicidae) in northern Virginia.

Aedes albopictus (Skuse) and Aedes japonicus (Theobald) are two of the most recent and widespread invasive mosquito species to have become established in the United States. The two species co-occur in water-filled artificial containers, where crowding and limiting resources are likely to promote inter- or intraspecific larval competition. The performance of northern Virginia populations of Ae. japonicus and Ae. albopictus competing as larvae under field conditions was evaluated. Per capita rates of population increase for each species were estimated, and the effects of species composition and larval density were determined. In water-containing cups provided with oak leaves, Ae. albopictus larvae exhibited a competitive advantage over Ae. japonicus as a consequence of higher survivorship, shorter developmental time, and a significantly higher estimated population growth rate under conditions of interspecific competition. Intraspecific competition constrained population performance of Ae. albopictus significantly more than competition with Ae. japonicus. In the context of the Lotka-Volterra model of competition, these findings suggest competitive exclusion of Ae. japonicus in those habitats where this species co-occurs with Ae. albopictus.

Thermal relaxation and low-frequency vibrational anomalies in simple models of glasses: a study using nonlinear Hamiltonians.

Glasses exist because they are not able to relax in a laboratory time scale toward the most stable structure: a crystal. At the same time, glasses present low-frequency vibrational-mode (LFVM) anomalies. We explore in a systematic way how the number of such modes influences thermal relaxation in one-dimensional models of glasses. The model is a Fermi-Pasta-Ulam chain with nonlinear springs that join second neighbors at random, which mimics the adding of bond constraints in the rigidity theory of glasses. The corresponding number of LFVMs decreases linearly with the concentration of these springs, and thus their effect upon thermal relaxation can be studied in a systematic way. To do so, we performed numerical simulations using lattices that were thermalized and afterwards placed in contact with a zero-temperature bath. The results indicate that the time required for thermal relaxation has two contributions: one depends on the number of LFVMs and the other on the localization of modes due to disorder. By removing LFVMs, relaxation becomes less efficient since the cascade mechanism that transfers energy between modes is stopped. On the other hand, normal-mode localization also increases the time required for relaxation. We prove this last point by comparing periodic and nonperiodic chains that have the same number of LFVMs.

Hosts of sandfly vectors of Leishmania braziliensis guyanensis in the central Amazon of Brazil.

The blood meals of 2,569 phlebotomine sandflies from areas endemic for cutaneous leishmaniasis in the central Amazon of Brazil were tested by the microcapillary precipitin method to determine their vertebrate hosts. The two-toed sloth, Choloepus didactylus, was the predominant host of two incriminated vectors of Leishmania braziliensis guyanensis in the region, Lutzomyia umbratilis and Lu. anduzei (64.0% and 63.6%, respectively). The Lu. "shannoni" group, a complex of several species in which females are indistinguishable, also fed predominantly on sloths (73.0%). Species comprising the Lu. "shannoni" group have not been implicated as vectors of leishmaniasis; however, their feeding patterns in the study area illustrate their potential involvement in the transmission of the parasites to two-toed sloths, which are the principal reservoir hosts of L. braziliensis in Panama. Rodents, and particularly porcupines, were the second most frequently fed-on mammal by Lu. umbratilis (11.6%) and the Lu. "shannoni" group (8.5%).

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

A total of 46 Trypanosoma rangeli stocks were isolated from naturally infected mammals and triatomine vectors. Twenty-two stocks were from the common opossum (Didelphis 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, inoculative (anterior station) transmission to mice, morphological parameters in parasitemic mice and comparisons of isozyme profiles with a known stock of T. rangeli isolated from man. Three other trypanosome stocks from D. marsupialis, T. tetradactyla and the three-toed sloth (Bradypus tridactylus) were morphologically similar to T. rangeli in culture but had quite different isozyme profiles and were not identified. It is concluded that T. rangeli is widely distributed in Amazonas, Pará 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 man. It is likely that T. rangeli is also occasionally transmitted to man in the Amazon basin.

Flagellate infections of Brazilian sand flies (Diptera: Psychodidae): isolation in vitro and biochemical identification of Endotrypanum and Leishmania.

Flagellate infections were found in 1,063 of 18,895 sand flies collected in the states of Amazonas, Pará, Rondonia and Acre, Brazil. Infection rates were 13.4% (species group Shannoni); 7.5% (subgenus Nyssomyia); 6.7% (subgenus Lutzomyia series Cruciata); 0.5% (genus Psychodopygus) and 3.1% for other sand flies (various subgenera). Leishmania braziliensis guyanensis and L. mexicana amazonensis were isolated, respectively, from the known vectors, Lutzomyia umbratilis and L. flaviscutellata. Single stocks of L. braziliensis-like and L. mexicana-like organisms were isolated, respectively, from L. whitmani and L. yuilli. Thirty-eight flagellate stocks, isolated by direct culture from sand flies were characterized in detail by morphology in culture, behavior in hamsters and mice and by enzyme profiles. Sixteen stocks from Lutzomyia sp. (Shannoni group) were identified as Endotrypanum schaudinni; 8 stocks from Lutzomyia sp. (Shannoni group) were identified as Endotrypanum sp.; 7 stocks from Psychodopygus ayrozai and P. paraensis were identified as Leishmania sp. previously isolated from the armadillo, Dasypus novemcinctus; 2 stocks of Trypanosoma rangeli were isolated from recently fed Lutzomyia sp. (Shannoni group) sand flies; the remaining 5 stocks from L. umbratilis and L. yuilli could not be identified. Observations suggested that Shannoni group sand flies were the natural vectors of Endotrypanum. Leishmania sp. infections in the man-biting flies P. ayrozai and P. paraensis were restricted to the midgut and associated with recent bloodmeals. Unidentified flagellates in L. umbratilis and L. yuilli were distributed throughout the digestive tract with no trace of bloodmeals.

The opossum, Didelphis marsupialis (Marsupialia: Didelphidae), as a reservoir host of Leishmania braziliensis guyanensis in the Amazon Basin of Brazil.

A total of 52 opossums (six species) were examined for evidence of infection with Leishmania in three different areas of forest near Manaus, Amazonas State, Brazil. No infections were detected in 27 opossums from a region of relatively undisturbed forest, including specimens of Didelphis marsupialis (18); Metachirus nudicaudatus (four); Monodelphis brevicaudata (one); Marmosa cinerea (two); M. murina (one) and M. parvidens (one). Of 15 D. marsupialis captured from a biological reserve, much disturbed by man, three were infected with L. braziliensis guyanensis: isolations were made from the skin of two of the animals, and from the viscera of the third. The isolates were biologically and biochemically indistinguishable from one isolate of L. b. guyanensis made from man and two from the sandfly vector Lutzomyia umbratilis from the same area. Two of eight D. marsupialis and both of two M. cinerea from another area of virgin forest used for army manoeuvres were infected with Leishmania mexicana amazonensis: the parasite was in all four cases isolated from normal skin. Five of nine specimens of Proechimys guyannensis, from the vicinity of Manaus, were also infected with L. m. amazonensis. A further 13 mammals (eight species) were negative for Leishmania. The importance of opossums as a reservoir of L. b. guyanensis is discussed. Although they may play only a minor role in virgin forest which is undisturbed by man, opossums (D. marsupialis) may become a significant reservoir of infection where man's activities have eliminated the major reservoir--which has yet to be incriminated.

Interferon alpha treatment of chronic hepatitis C in HIV-infected patients receiving zidovudine: efficacy, tolerance and response related factors.

BACKGROUND/AIMS: In our area most of the human immunodeficiency virus (HIV) infected patients are intravenous drug users; HIV and hepatitis C virus infections often coexist in these patients. Due to the repercussions of both infections, we designed a trial to evaluate the efficacy, response-related factors and tolerance during an eight-month regime of recombinant interferon alpha-2b on hepatitis C virus infection. METHODOLOGY: We included 79 patients in an open, prospective and multicentric trial with zidovudine and interferon alpha-2b. Response to interferon treatment was evaluated by biochemical and histopathological criteria. RESULTS: A complete response (alanine aminotransferase normalization) was obtained in 57.4% of patients. The significant response-related factors were: degree of histopathological activity, CD4+ cell number and initial leukocyte number. CONCLUSIONS: Recombinant interferon therapy seems to be effective for chronic hepatitis C in HIV infected patients; the best response was in those with active chronic hepatitis and CD4+ cell counts > or = 200/mm3. General tolerance was variable, although side effects were not different from those seen in non-HIV patients. The most common side effect was flu-like syndrome (constitutional manifestations), with no interference on treatment continuity; however, hematological toxicity prevents the indiscriminate use of interferon.

New records of Histoplasma capsulatum from wild animals in the Brazilian Amazon.

Twenty-eight isolates of Histoplasma capsulatum were obtained from eight species of forest mammals from the States of Amazonas, Pará and Rondônia in the Amazon Region of Brazil. Primary isolates were obtained by inoculating triturated liver and spleen tissue intradermally and intraperitoneally in hamsters. Mycological diagnosis in hamsters presenting lesions was confirmed by histopathology and culture on Sabouraud dextrose-agar. Infected hamsters developed signs of disease within two to nine months; all had disseminated visceral lesions and most also had skin lesions at the sites of inoculation. None of the hamsters inoculated with skin macerates of the original hosts developed histoplasmosis, and histopathological examination of the viscera of the wild hosts failed to reveal H. capsulatum. Prevalence of infection was considerably higher in females than in males both for the opossum Didelphis marsupialis and for total wild animals (479) examined. It is proposed that canopy-dwelling mammals may acquire the infection from conidia borne on convective currents in hollow trees with openings at ground-level.

Thermal conductivity, relaxation and low-frequency vibrational mode anomalies in glasses: a model using the Fermi-Pasta-Ulam nonlinear Hamiltonian.

We present a nonlinear model that allows exploration of the relationship between energy relaxation, thermal conductivity and the excess of low-frequency vibrational modes (LFVMs) that are present in glasses. The model is a chain of the Fermi-Pasta-Ulam (FPU) type, with nonlinear second neighbour springs added at random. We show that the time for relaxation is increased as LFVMs are removed, while the thermal conductivity diminishes. These results are important in order to understand the role of the cooling speed and thermal conductivity during glass transition. Also, the model provides evidence for the fundamental importance of LFVMs in the FPU problem.

[Morbimortality of acute endocarditis caused by Streptococcus agalactiae]. / Morbimortalidad de la endocarditis aguda por Streptococcus agalactiae.

INTRODUCTION: Streptococcus agalactiae is an uncommon cause of acute endocarditis. It is more likely to occur in people with underlying diseases and usually evolves poorly. MATERIALS AND METHODS: We have conducted a retrospective study comparing the clinical features of Streptococcus agalactiae acute endocarditis attended in our Hospital during the last twelve years with the ones caused by other microorganisms; we have analized as dependent variables the vegetation size, surgery needing, complications, time of hospitalisation and global mortality. RESULTS: All the cases by SGB had a great vegetation size, all needed surgery in its management with long hospitalisation periods, and the mortility was of 40%; everything was higher than other microorganism's endocarditis. CONCLUSION. Streptococcus agalactiae acute endocarditis is a serious disease which requires early surgery in its management. Its mortality rate, complications and hospitalisation time are high.

[Besnoitia (Protozoa: Toxoplasmatinae) isolated from opossums Didelphis marsupilis in the Amazon region, Brazil]. / Besnoitia (Protozoa: Toxoplasmatinae) isolado de mucuras Didelphis marsupialis na região Amazõnica, Brasil.

From a total of 224 Didelphis marsupialis examined, in 15 were found cysts of Besnoitia in muscles and viscera. It's the first time that this protozoan is isolated from naturally infected animals in Brazil. The experimental transmission to laboratory animals was done by the inoculum of tissue and cysts triturated.

A pilot study to control Lutzomyia umbratilis (Diptera:Psychodidae), the major vector of Leishmania braziliensis guyanensis, in a peri-urban rainforest of Manaus, Amazonas State, Brazil.

In the second half of 1980, 112 (or ca. 16%) of the inhabitants of the new settlement of São José, city of Manaus, contracted cutaneous leishmaniasis whilst clearing their properties of terra firme rainforest. With the aid of SUCAM, the authors carried out a pilot study to investigate the feasibility of reducing populations of Lutzomyia umbratilis, the local silvatic vector of Leishmania braziliensis guyanensis, by spraying insecticide on its favoured diurnal resting sites, the bases of the larger forest trees. Most manvector contact is at these resting sites and, therefore, it was encouraging to record a marked reduction of the tree-base populations of L. umbratilis for 21 days following just one application of D.D.T. emulsion in an area 200m square. Most of the treated trunks were not occupied by L. umbratilis for at least eleven months. Suggestions for extending the pilot study are made, and the need for collaboration with a clinical team is emphasized. Leishmania b. guyanensis is the aetiological agent of "pain bois", which is hyperendemic from French Guiana to central Amazônia. In the absence of proven vaccines or methods of vector control, some simple methods for limiting transmission of Le. b. guyanensis to man are listed.