Efficiency of Phytoseiulus longipes Evans as a control agent of Tetranychus evansi Baker & Pritchard (Acari: Phytoseiidae: Tetranychidae) on screenhouse tomatoes

The spider mite Tetranychus evansi Baker & Pritchard can cause severe damage to tomato crops. The predatory mite Phytoseiulus longipes Evans was recently reported in association with T. evansi in Uruguaiana, Rio Grande do Sul State, Brazil. The objective of the present study was to evaluate the effects of P. longipes on the population of T. evansi on tomatoes under screenhouse condition. The study consisted on four experiments, in each of which 80 potted plantlets were distributed in two plots of 40 plantlets each. Two weeks later, each plantlet of both plots was infested with eight adult females of T. evansi; one week after, four adult females of P. longipes were released onto each plant of one plot. The population levels of T. evansi and the damage caused by these mites were significantly lower (P < 0.05; linear mixed-effect model) in the plots where P. longipes had been released. The results indicate the potential of this predator as a candidate for classical biological control of T. evansi by inoculative releases on tomato plants.     

Prevalence of Antibody to Hepatitis E Virus among Healthy Individuals in Southern Taiwan

The seroprevalence of hepatitis E virus (HEV) among 997 healthy individuals aged 6 to 84 years, collected between July 1993 and June 1994 at Kaohsiung-Pingtung area in Southern Taiwan was studied. Of the study populations of vegetable farmers, elementary school children, volunteer blood donors and college students, the prevalence of IgG anti-HEV ranged from 6.4% to 8.8%. In suburban elemantary school children of Mang-Chou Village at Pingtung-Hsien, the seroprevalence rate (9.6%) was significantly higher than the positive rate (1.5%) found in rural aboriginal elementary school of San-Min Village at Kaohsiung-Hsien. IgG anti-HEV antibodies were widely distributed among all age groups, with a significantly higher percentage (13.1%) in the age group of 46-55 years old.     

The re-emergence of American visceral leishmaniasis in an old focus in Venezuela. II. Vectors and parasites.

As part of an epidemiological study in an old focus of American Visceral Leishmaniasis (AVL) in Venezuela (Guayabita, Aragua State), a longitudinal entomological survey (January 1993-June 1994) was carried out. A total of 3,239 males and 6,043 females belonging to 11 phlebotomine sandfly species were collected. The two recognised vectors of AVL in the New World, Lutzomyia evansi and Lu. longipalpis were found to be sympatric. Lutzomyia evansi was the dominant species (86.4%), almost ten fold times more abundant than Lu. longipalpis (10.6%). The two species alternated seasonally: Lu evansi peaked at the end of the rainy season while Lu. longipalpis, almost virtually absent during such period, increased in the dry season. This species seems more greatly influenced by the temperature. Seven of 4,559 Lutzomyia evansi (0.15%) and one of 353 Lu. longipalpis (0.28%) were found positive for suprapyloric promastigotes. Using the polymerase chain reaction (PCR) with universal primers, all isolates were identified as Leishmania spp. Two cultures from Lu. evansi, IEVA/VE/93/UCNA-2 and IEVA/VE/93/UCNA-3, were established. k-DNA restriction analysis showed high homologies between these isolates and Leishmania chagasi. High hybridization signal with L. chagasi specific kDNA confirmed these results. These findings suggest that Lu. evansi may play a role as vector of visceral leishmaniasis in this area. The identity of the parasite carried by Lu. longipalpis needs to be confirmed.     

Risk factors for human T cell lymphotropic virus type I among injecting drug users in northeast Brazil: possibly greater efficiency of male to female transmission

It was observed in the city of Salvador, State of Bahia, the highest seroprevalence of human T cell lymphotropic virus type 1 (HTLV-I) infection in Brazil as demonstrated by national wide blood bank surveys. In this paper, we report results of an investigation of drug use and sexual behavior associated with HTLV-I infection among male and female injecting drug users (IDUs) in Salvador. A cross sectional study was conducted in the Historical District of Salvador from 1994-1996 (Projeto Brasil-Salvador) and 216 asymptomatic IDUs were selected using the snowball contact technique. Blood samples were collected for serological assays. Sera were screened for human immunodeficiency virus (HIV-1/2) and HTLV-I/II antibodies by ELISA and confirmed by Western blot. The overall prevalence of HTLV-I/II was 35.2% (76/216). The seroprevalence of HTLV-I, HTLV-II and HIV-I was for males 22%, 11.3% and 44.1% and for females 46.2%, 10.3% and 74.4% respectively. HTLV-I was identified in 72.4% of HTLV positive IDUs. Variables which were significantly associated with HTLV-I infection among males included needle sharing practices, duration of injecting drug use, HIV-I seropositivity and syphilis. Among women, duration of injecting drug use and syphilis were strongly associated with HTLV-I infection. Multivariate analysis did not change the direction of these associations. Sexual intercourse might play a more important role in HTLV-I infection among women than in men.     

A field trial of the effectiveness of a feline Toxoplasma gondii vaccine in reducing T. gondii exposure for swine

A 3-yr field trial was conducted on 8 commercial swine farms in Illinois to determine the effectiveness of a feline Toxoplasma gondii vaccine in reducing the exposure of swine to T. gondii. A vaccine consisting of live bradyzoites of the mutant T-263 strain, capable of preventing oocyst shedding by cats, was used in this study. Each farm was visited 3 times in 1994, 3 times in 1995, and once in 1996. Cats were trapped and inoculated with the T-263 oral vaccine during 1994 and 1995. On each visit, the following samples were collected: blood from pigs, cats, and mice for detection of serum antibodies to T. gondii, feces from cats to detect oocysts, and heart and brain tissues from rodents to determine the presence of T. gondii tissue cysts. The modified agglutination test (MAT), with a positive titer set at the 1:25 dilution, was used to determine serum antibodies. At first capture, 72.6% (61/84) of juvenile cats and 32.6% (31/95) of adult cats had no detectable antibodies (seronegative), indicating no prior exposure to T. gondii when they received their first vaccine. Of these first-time seronegative cats, 58.1% (18/31) of adult and 45.9% (28/61) of juvenile cats were recaptured and received a second dose of vaccine. Changes in the prevalence of T. gondii infection were evaluated from the prevaccination (1992, 1993) to the postvaccination (1996) period. Eleven cats (5%) were detected shedding oocysts between 1994 and 1996, of which 10 (90.1%) shed during 1994. The last detection of oocyst shedding by cats was during the first farm visit in 1995. There was a significant decrease in T. gondii seroprevalence for finishing pigs (P < 0.05, Wilcoxon sign rank test). There was a positive correlation (Spearman's p = 1.0, P < 0.0001) between the change in prevalence in juvenile cats and the change in prevalence in finishing pigs. The seropositivity rate (MAT > or = 1:25) in mice among all farms decreased from 4% in 1992-1993 to 0% in 1996. The mean prevalence of T. gondii tissue cyst isolation for mice on all farms decreased from 1.1% in 1994, to 0.8% in 1995, and to 0.5% in 1996. The results of this study suggest that the reduced exposure of pigs to T. gondii was due to the administration of the T. gondii vaccine to cats.     

Changes in prevalence of herpes simplex virus type 1 and 2 antibodies from 1973 to 1993 in the rural districts of Japan

Using the gG-capture ELISA, changes in the seroprevalence of HSV-1 and HSV-2 from 1973 to 1993 were studied for 614 sera collected from general adults living in rural Japan. The HSV-1 seroprevalence for men and women decreased from 75.3 and 80.6% in 1973 to 54.4 and 59.6%, respectively, in 1993. The HSV-2 seroprevalence also decreased from 10.2 and 9.9% in 1973 to 1.8 and 1.2%, respectively, in 1993. Although the decrease in HSV-2 prevalence seemed to be correlated with the general decrease of sexually transmitted diseases in Japan since the 1950s, these findings should not be interpreted as typical, as HSV-2 infections are particularly known to distribute unevenly among populations, according to sexual activity and cohorts.     

Limnological conditions in Mono Lake: contrasting monomixis and meromixis in the 1990s

Mono Lake is a large, saline lake, located in the North American Great Basin and is subject to large variations in freshwater inflow as climatic conditions and diversion schemes have changed; consequently, major variations in chemical stratification occur. A transition from monomixis to meromixis occurred from 1994 to 1995. Lake-wide surveys of temperature, conductivity, dissolved oxygen, ammonium and chlorophyll profiles, Secchi depth and light attenuation, and Artemia monica abundances conducted throughout 1993, 1994, 1995, 1996 and 1997 document the contrasts between monomixis and meromixis. During the monomictic conditions in 1993 and 1994, the lake thermally stratified in March and mixed to the bottom by December, the hypolimnion became anoxic in late March and the water column was oxygenated to the bottom by December. During meromictic conditions in 1995, 1996 and 1997, the absence of holomixis during winter resulted in persistent anoxic conditions beneath the chemocline, an accumulation of ammonium in the monimolimnion and depletion in the mixolimnion, and low mixolimnetic chlorophyll concentrations in the spring and autumn. A comparison of the density differences between 2 and 28 m due to thermal versus chemical stratification indicated thermal stratification predominated in 1993 and 1994, while in 1995, 1996 and 1997 chemical stratification dominated the density differences. Ammonium, the limiting nutrient in Mono Lake, was lower in the upper mixed layer throughout 1996 and 1997 compared to the monomictic years, 1993 and 1994. During 1996 and 1997, the annual maxima in Secchi depths were among the deepest observed during the past 19 years, and reflected the lower phytoplankton abundance caused by decreased availability of nitrogen as a result of strong chemical stratification and the absence of a period of holomixis. In both 1996 and 1997, maturation of the spring generation of Artemia was slowed, peak abundance of the first generation of adult Artemia was a month later and percent ovigery, fecundity, and body size were reduced as compared to 1993 and 1994.     

A "Screen-and-Treat" Approach for Helicobacter pylori Infection: A Population-Based Study in Vammala, Finland

Background:  To accelerate the decline of Helicobacter pylori infection, and to study the significance of the possible risk factors for H. pylori infection in Finland, we started a voluntary H. pylori "screen-treat-retest-and-retreat" program for all young adults at primary health care in Vammala, Finland after a pilot study in 1994 including 504 subjects aged 15–75.
Materials and Methods:  A total of 3326 aged 15–40 in 1996, and 716 aged 15 and 584 aged 45 in 1997–2000 were screened for H. pylori using serology. Helicobacter pylori positive were treated, cure was verified by serology.
Results:  The eradication rates were 93.8%, 82.2%, and 77.6% per protocol in pilot study in 1994, in subjects invited in 1996 and 1997–2000, respectively. Helicobacter pylori seroprevalence rates were calculated to have decreased from 36% to 14% in pilot study, from 12% to 4% among subjects invited in 1996, from 3% to 2% among subjects aged 15 and from 27% to 12% among subjects aged 45 in 1997–2000. An epidemiologic questionnaire in 1996 revealed that crowding in the childhood household, low education of the mother, current smoking and alcohol consumption, unfavorable housing conditions, and sick leaves due to dyspepsia were independently associated with H. pylori infection.
Conclusions:  This intervention with high participation rates resulted in a significant decline in calculated H. pylori seroprevalence rates. Although the low prevalence of H. pylori infection may limit the cost efficiency of the program, the intervention is expected to reduce the burden of H. pylori -associated diseases.     

Trypanosoma evansi: molecular homogeneity as inferred by phenetical analysis of ribosomal internal transcribed spacers DNA of an eclectic parasite

The protozoan Trypanosoma evansi is described as presenting high morphological and genetic similarities among the isolates despite its biological heterogeneity and wide geographical distribution. PCR amplification of the internal transcribed spacers of the ribosomal gene in combination with the coding region of the 5.8S ribosomal subunit further submitted to restriction enzymes digestion were carried out in DNAs extracted from 41 T. evansi strains isolated from horses, dogs, coatis and capybaras from two distinct regions of the Brazilian Pantanal. We also used one T. evansi isolate from Africa, one from Asia and one isolate of T. b. brucei from Africa. Analysis of the RFLP profiles yielded a unique "riboprinting" that does not vary intraspecifically. These results provide insights on the ribosomal gene organization of T. evansi and showed that ITS analysis by RFLP show high genetic similarity of this locus among isolates of this protozoan parasite.     

Genetic relatedness among Trypanosoma evansi stocks by random amplification of polymorphic DNA and evaluation of a synapomorphic DNA fragment for species-specific diagnosis.

In this study we employed randomly amplified polymorphic DNA patterns to assess the genetic relatedness among 14 Brazilian Trypanosoma evansi stocks from domestic and wild hosts, which are known to differ in biological characteristics. These akinetoplastic stocks were compared with one another, to three Old World (Ethiopia, China and Philippines) dyskinetoplastic stocks of T. evansi, and also with Trypanosoma equiperdum, Trypanosoma brucei brucei, Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense. Randomly amplified polymorphic DNA analysis showed limited heterogeneity in T. evansi stocks from different hosts and geographical regions of the world, or in other species of the subgenus Trypanozoon. However, minor variations generated random amplification of polymorphic DNA analysis disclosed a pattern consisting of a unique synapomorphic DNA fragment (termed Te664) for the T. evansi cluster that was not detected in any other trypanosome species investigated. Pulsed field gel electrophoresis analysis demonstrated that the Te664 fragment is a repetitive sequence, dispersed in intermediate and minichromosomes of T. evansi. Based on this sequence, we developed a conventional PCR assay for the detection of T. evansi using crude preparations of blood collected either on glass slides or on filter paper as template DNA. Our results showed that this assay may be useful as a diagnostic tool for field-epidemiological studies of T. evansi.     

Pelagic larvae of benthic gastropods from shallow Antarctic waters of Admiralty Bay,King George Island

The occurrence, distribution and summer variation of pelagic larvae of benthic gastropods in the shallow coastal area of Admiralty Bay were determined for the summers of 1993/1994, 1994/1995 and 1996/1997 from plankton samples taken at 15- to 30-m depths in 12 stations. Significant differences were found among years at the end of January and February. Results of Principal Component Analysis showed the inverse relation of high wind speed and abundance of gastropod larvae in the three austral summers sampled, and suggested that environmental conditions prevalent during 1994/1995 and 1995/1997 were similar and differed from those of 1993/1994, which may have influenced the number of larvae observed.     

Trypanosoma evansi: cloning and expression in Spodoptera frugiperda [correction of fugiperda] insect cells of the diagnostic antigen RoTat1.2

A complementary DNA encoding the variant surface glycoprotein (VSG) of Trypanosoma evansi Rode Trypanozoon antigenic type (RoTat)1.2, currently used for experimental serological diagnosis of T. evansi infection in livestock, was cloned as a recombinant plasmid and sequenced. A recombinant baculovirus containing the coding region of RoTat1.2 VSG was constructed to express the protein in Spodoptera frugiperda [corrected] insect cells. From this, sufficient quantities of the recombinant protein are being produced for empirical and wide-scale objective assessment of the diagnostic potential of this antigen. The gene encoding the RoTat1.2 VSG was shown by PCR to be present in the genomes of many different cloned isolates of T. evansi, but not T. brucei, from geographically separate regions of Africa, Asia, and South America. With the recombinant RoTat1.2 at hand, it is now possible to investigate the extent to which epitopes on this VSG are conserved among different T. evansi isolates.     

The detection of non-RoTat 1.2 Trypanosoma evansi

The majority of Trypanosoma evansi can be detected using diagnostic tests based on the variant surface glycoprotein (VSG) of Trypanosoma evansi Rode Trypanozoon antigen type (RoTat) 1.2. Exceptions are a number of T. evansi isolated in Kenya. To characterize T. evansi that are undetected by RoTat 1.2, we cloned and sequenced the VSG cDNA from T. evansi JN 2118Hu, an isolate devoid of the RoTat 1.2 VSG gene. A 273 bp DNA segment of the VSG gene was targeted in PCR amplification for the detection of non-RoTat 1.2 T. evansi. Genomic DNA samples from different trypanosomes were tested including 32 T. evansi, 10 Trypanosoma brucei, three Trypanosoma congolense, and one Trypanosoma vivax. Comparison was by PCR amplification of a 488 bp fragment of RoTat1.2 VSG gene. Results showed that the expected 273 bp amplification product was present in all five non-RoTat 1.2 T. evansi tested and was absent in all 27 RoTat 1.2-positive T. evansi tested. It was also absent in all other trypanosomes tested. The PCR test developed in this study is specific for non-RoTat 1.2 T. evansi.     

Diapause, pupation sites and parasitism of the horn fly, Haematobia irritans, in south-eastern Brazil

In order to verify the occurrence of diapause, preference for pupation sites and hymenopteran parasitism, the pupae of the horn fly, Haematobia irritans (Diptera: Muscidae), were collected from undisturbed cattle dung pats in pastures, and adults of the fly were sampled from cattle in São Paulo State, south-eastern Brazil, from April 1993 to July 1994. Diapause was verified in 7.7% of pupae sampled from pastures in June and July of 1993 and in 9.9% of those sampled in May, June and July of 1994 (overall rate of 9.1%). Approximately 8.3% of the pupae were parasitized by microhymenopterans, mostly Spalangia nigroaenea and S.cameroni (Hymenoptera: Pteromalidae). Horn fly pupae were found almost exclusively inside the pat or in the soil immediately beneath and adjacent to it, and very few were collected elsewhere. Pupa mortality was 54.4% and did not change significantly during the year, but mortality was greater among pupae collected in pastures when compared to those obtained from experimental pats, lacking natural enemies.     

A herbivorous mite down-regulates plant defence and produces web to exclude competitors

Herbivores may interact with each other through resource competition, but also through their impact on plant defence. We recently found that the spider mite Tetranychus evansi down-regulates plant defences in tomato plants, resulting in higher rates of oviposition and population growth on previously attacked than on unattacked leaves. The danger of such down-regulation is that attacked plants could become a more profitable resource for heterospecific competitors, such as the two-spotted spider mite Tetranychus urticae. Indeed, T. urticae had an almost 2-fold higher rate of oviposition on leaf discs on which T. evansi had fed previously. In contrast, induction of direct plant defences by T. urticae resulted in decreased oviposition by T. evansi. Hence, both herbivores affect each other through induced plant responses. However, when populations of T. evansi and T. urticae competed on the same plants, populations of the latter invariably went extinct, whereas T. evansi was not significantly affected by the presence of its competitor. This suggests that T. evansi can somehow prevent its competitor from benefiting from the down-regulated plant defence, perhaps by covering it with a profuse web. Indeed, we found that T. urticae had difficulties reaching the leaf surface to feed when the leaf was covered with web produced by T. evansi. Furthermore, T. evansi produced more web when exposed to damage or other cues associated with T. urticae. We suggest that the silken web produced by T. evansi serves to prevent competitors from profiting from down-regulated plant defences.     

Occurrence of co-infection by Leishmania (Leishmania) chagasi and Trypanosoma (Trypanozoon) evansi in a dog in the state of Mato Grosso do Sul, Brazil

A natural case of co-infection by Leishmania and Trypanosoma is reported in a dog (Canis familiaris) in south- western state of Mato Grosso do Sul, Brazil. Both amastigote and trypomastigote forms were observed after Giemsa staining of cytological preparations of the dog's bone marrow aspirate. No parasite was detected using medium culture inoculation of the sample. DNA obtained from the bone marrow aspirate sample and from the blood buffy coat was submitted to polymerase chain reaction (PCR) with a set of rDNA-based primers S4/S12. The nucleotide sequence of the PCR product was identical to that of Trypanosoma (Trypanozoon) evansi. The S4/S12 PCR was then used as template in a nested-PCR using a specific Leishmania set S17/S18 as primers, to explain the amastigote forms. The nucleotide sequence of the new PCR product was identical to that of Leishmania (Leishmania) chagasi. This case, as far as we know, is the first report of a dog co-infected with these parasites, suggesting that besides L. (L.) chagasi, the natural transmission of T. (T.) evansi occurs in the area under study.     

A winter's tale: Among-year variation in bird community structure in a southeastern Australian forest

Abstract The bird community structure of an undisturbed forest (Olinda State Forest) east of Melbourne, Victoria, varied greatly among the winters of 1993, 1994 and 1995. Increases in the total density of all diurnally active species were as much as 66% between winters [381 versus 633 birds per 50 ha (the density unit used throughout)]. Community structure differed significantly among all three winters, although 1993 and 1994 differed most (1995 was intermediate). One of the striking features was the heterogeneity in patterns among species, families and foraging guilds over the three winters: some taxa (guilds) showed significantly higher densities in the middle year (1993 < 1994 > 1995), others increased monotonically (1993 < 1994 < 1995), while others increased from 1993 to 1994 and maintained those densities in 1995. The species showing significantly higher densities in 1994 were mostly nectarivorous, which seemed to accord with profuse and sustained flowering by Eucalyptus cypellocarpa in 1994 alone. The results are discussed in the context of non-equilibrial community dynamics, large- versus small-scale processes, and the implications of this magnitude of variation in unperturbed forests for environmental monitoring and impact assessments.     

First report of establishment of Trypanosoma evansi infection in pigeon nestlings (Columba livia)

Trypanosomosis (surra) caused by Trypanosoma evansi is quite common among horses where the parasite is endemic. In the present study, T. evansi was isolated from an infected horse and maintained by subinoculation in Swiss albino mice. At the peak of parasitemia (5 x 10(6) parasites per ml of blood), 0.25 ml of the tail blood from infected mice was inoculated intraperitoneally and subcutaneously to 2 groups of adult pigeons and 2 groups of pigeon nestlings. Four days after inoculation, the trypanosomes occurred in the peripheral circulation of pigeon nestlings, but no parasitemia was observed in adult pigeons. The body temperatures of infected nestlings increased to 104 F, whereas uninfected controls remained steady at 102 F; thus, elevated temperatures coincided with parasite presence in the peripheral circulation. A decrease in hemoglobin concentration of blood also was observed in infected nestlings. On microscopic examination, increases in length and breadth of trypomastigotes and vigorous flagellar movement of the parasites were observed. The virulence and pathogenicity of the parasites after adaptation to nestlings remained unchanged for albino mice as proved by the death of all subinoculated mice. Furthermore, polymerase chain reaction studies confirmed that the genomic DNA of trypanosomes in pigeon blood was the same as that of T. evansi. This is the first report of the establishment of T. evansi infection in pigeon nestlings.