Incidence Of Viral Infections Research Articles

Immunosuppression Related to De Novo Donor-Specific HLA Antibody Production after Renal Transplantation

Aim One of the major factors influencing graft loss is antibody-mediated rejection caused by the production of donor-specific HLA antibodies (DSA). The optimization of multidrug combination therapy using immunosuppressants is required in order to prevent DSA production. We herein evaluated the relationships among clinical variants including immunosuppressant levels and the prediction of DSA production after renal transplantation (Tx). Methods Living renal transplant patients (n=160) at our institute who received standard immunosuppressant protocols with basiliximab, tacrolimus (Tac), mycophenolate mofetil (MMF), and steroids between July 2004 and September 2013 were enrolled. The production of serum anti-HLA antibodies at one-year post-Tx was analyzed by solid-phase bead-based assays using Luminex. The HLA specificity of DSA was evaluated based on the data of donor HLA typing. In the present study, preformed DSA and de novo DSA were defined as those detected pre-Tx and at one-year post-Tx, and those detected at one-year post-Tx only, respectively. Risk factors for DSA production were statistically evaluated using clinical variables including Tac trough levels and the incidence of virus infections. Results DSA production at one-year post-Tx was observed in 15 patients including 9 with preformed DSA and 7 with de novo DSA. Preformed and de novo DSA were detected in one patient. De novo DSA production was more likely to occur in patients with low serum Tac levels (cut-off value: 3.2 ng/mL), in those who ceased MMF medication, and in those who acquired CMV infection within one-year post-Tx (p=0.008, 0.044, and 0.050, respectively). Conclusions The appropriate control of Tac trough levels, continuation of MMF intake, and prevention of CMV infection were found to be important for avoiding de novo DSA production at one-year post-Tx in the present study.

DYNAMICS OF EPIDEMIOLOGICAL PARAMETERS OF TYPE 1 DIABETES MELLITUS IN CHILDREN IN THE REPUBLIC OF KARELIA

Type 1 diabetes mellitus is one of the most common autoimmune diseases in the world. The Republic of Karelia belongs to a group of regions with a high prevalence rate of type 1 diabetes mellitus (over 200 per 100,000 residents). In the last 20 years, type 1 diabetes incidence has increased 3.4 times, mostly due to the onset at an early age. The incidence rate of new cases of type 1 diabetes among children and adolescents does not show any clear linear dependence. Significant incidence occur every 4 or 5 years, which is most likely to be connected with an increase in the incidence of virus infection in these years. The primary incidence of type 1 diabetes mellitus among children per every 100 thousand of the child population is also higher in the Republic of Karelia compared to the Russian Federation. 17,4% children in Karelia have a genetic predisposition to type 1 diabetes mellitus (positive for HLA-DQB*0302 and/ or *02 and negative for the protective alleles *0602/03, *0301), which is lower than in Finland (23%).Genetic heterogeneity among ethnic populations in conjunction with environmental factors can determine the peculiarities of type 1 diabetes mellitus prevalence rate.

P083 Prediction of de novo donor specific HLA antibody production in the follow-up period of kidney transplantation

Aim One of the major factors for the graft loss is antibody-mediated rejection caused by the production of donor-specific HLA antibody (DSA). Optimization of multidrug combination therapy of immunosuppressant agents is required to prevent the production of DSA. In this study, we evaluated the relation of clinical variants including immunosuppressant levels to the prediction of DSA production in post-renal transplantation (Tx). Methods We enrolled a total of 160 living kidney transplant patients at our institute from July 2004 to September 2013. The patients were subjected to standard immunosuppressant protocols with basiliximab, tacrolimus (Tac), mycophenolate mofetil (MMF), and steroids. The production of the serum anti-HLA antibody at one-year post-Tx was analyzed by solid-beads assay using Luminex system. HLA specificity of the DSA was identified based on the data of donor HLA typing. In this study, preformed DSA and de novo DSA are defined as that detected at both pre-Tx and one-year post-Tx, and that detected at only one-year post-Tx, respectively. Risk factors for DSA production were statistically evaluated by Mann–Whitney U-test or Fisher’s exist test using clinical variables including the Tac trough levels and incidence of virus infections. Results DSA production at one-year post-Tx was observed in 15 patients including 9 preformed DSA and 7 de novo DSA. In one patient, both preformed and de novo DSA were observed. De novo DSA production was more likely to observed in patients who experienced the low serum Tac level (cut-off value: 3.2 ng/mL), in patients who ceased MMF medication, and in patients who acquired CMV infection within one-year post-Tx (p = 0.008, 0.044 and 0.050, respectively). Conclusions To avoid de novo DSA production at one-year post-Tx, the appropriate control of Tac trough levels, the continuation of MMF intake, and the prevention of CMV infection were important in this study.

Cellular Immune Therapy for Epstein-Barr Virus Infection after Hematopoietic Stem Cell Transplantation

Hematopoietic stem cell transplantation is an effective method for treatment of hematologic malignancies. Due to the use of immunosuppressive agents and a long time of immune restoration after transplantation, the incidence of virus infection is high. Epstein-Barr virus (EBV) infection is a common viral infection after transplantation. In spite of the low incidence of post transplantation lymphoproliferative disorder (PTLD) caused by EBV, this disease is characte-rized by rapid progression and high mortality. T lymphocytes play an important role in anti-viral immunity, and the cellular immune therapy based on virus-specific cytotoxic T lymphocyte (CTL) is safe and efficient. This review presents the domestic and foreign advances in cellular immune treatment against EBV infection, and explores the clinical application prospects as well as problems.

First Report of Zucchini yellow mosaic virus in Watermelon in Bosnia and Herzegovina.

Several potyvirus species cause severe economic losses in cucurbit crops in the Mediterranean region, but Zucchini yellow mosaic virus (ZYMV) is regarded as one of the most destructive (2,3). In June 2012, field-grown watermelon plants (Citrullus lanatus [Thunb.] Matsum and Nakai) showing mild to severe mosaic, mottling, and bubbling followed by leaf deformation with blistering were observed in the Kukulje locality (Region of Banja Luka) in Bosnia and Herzegovina. Incidence of virus infection in the field was visually estimated at 15%. Symptomatic watermelon plants were collected and tested for the presence of the most prevalent watermelon viruses including ZYMV, Cucumber mosaic virus (CMV), Watermelon mosaic virus (WMV), Papaya ringspot virus (PRSV), and Squash mosaic virus (SqMV) (1) using commercial double-antibody sandwich (DAS)-ELISA diagnostic kits (Bioreba AG, Reinach, Switzerland). Commercial positive and negative controls were included in each assay. Of the 14 watermelon plants tested, all were positive for ZYMV and negative for WMV, CMV, PRSV, and SqMV. Sap prepared from an ELISA-positive sample (isolate 314-12) and healthy watermelon plants, using 0.01 M phosphate buffer (pH 7) was mechanically inoculated onto five carborundum-dusted plants of each Chenopodium quinoa and Citrullus lanatus 'Creamson sweet'. Mechanically inoculated C. quinoa plants exhibited chlorotic spots 5 days post-inoculation, while severe mosaic accompanied by crinkling and leaf deformation were observed on all inoculated watermelon plants 12 days post-inoculation. For further confirmation of the virus identity, total RNAs from all 14 naturally and 5 mechanically infected watermelon plants were extracted with the RNeasy Plant Mini Kit (Qiagen, Hilden, Germany) and subjected by reverse transcription (RT)-PCR. RT-PCR was carried out with One-Step RT-PCR Kit (Qiagen) using ZYMV-specific primer pair, CPfwd and CPrev (4), designed to amplify an 1,100-bp fragment covering the entire coat protein (CP) gene and part of the nuclear inclusion (NIb) and 3'-UTR. Total RNAs obtained from the Serbian ZYMV isolate from winter squash (GenBank Accession No. JN315861) and tissue sample from healthy watermelon leaves were used as positive and negative controls, respectively. The expected size of the RT-PCR product was amplified from each of the watermelon plants assayed confirming serological virus identification. One amplicon derived from isolate 314-12 was purified (QIAquick PCR Purification Kit, Qiagen) and sequenced directly (KF836440). Sequence analysis of the complete CP gene, conducted by MEGA5 software, revealed that watermelon isolate from Bosnia and Herzegovina showed the highest nucleotide identity of 99.8% (99.6% amino acid identity) with 14 ZYMV isolates originating from different hosts from Serbia (HM072431, JF308189 to 90, JN315856 to 57, JN315859 to 61) and Austria (AJ420012 to 17). To our knowledge, this is the first report of ZYMV in Bosnia and Herzegovina, which is an important discovery. It represents expansion of this virus to new geographical area. Considering that the ZYMV is among the most devastating pathogens of cucurbits (3), further survey is needed to determine its distribution in Bosnia and Herzegovina.

Incidence of virus infections in grapevines from Croatian collection plantations

Evaluation of the incidence of virus infections was conducted in two grapevine collection fields. The first was the National collection of Croatian native grapevine cultivars, situated at the “Jazbina” experimentation station in eastern Zagreb, where more than 120 different autochthonous grapevine cultivars are held, collected from different Croatian vine-growing regions. The second was a regional collection located in Risika, on the island of Krk (the North Adriatic region) containing 19 native cultivars from that region. During February 2009 from both collections, 95 plants were selected and tested for presence of eight viruses by ELISA, including: Arabis mosaic virus (ArMV), Grapevine fanleaf virus (GFLV), Grapevine fleck virus (GFkV), G rapevine leafroll-associated virus 1 (GLRaV-1), Grapevine leafroll-associated virus 2 (GLRaV-2), G rapevine leafroll-associated virus 3 (GLRaV-3), Grapevine virus A (GVA) and Grapevine virus B (GVB). The dominant virus in both collections was GLRaV-3, present in 75 vines (78.9%) in the National collection and in 73 vines (76.8%) in the Risika collection. The second most frequent virus in the National collection was GVA (60.0%), followed by GLRaV-1 (29.5%), GFkV (24.2%), GFLV (17.9%), ArMV (12.6%), GLRaV-2 and GVB (2.1%). In the Risika collection, GLRaV-3 was followed by GFLV (42.1%), GFkV (36.8%), GVA (32.6%), ArMV (23.2%), GLRaV-1 (11.6%), GLRaV-2 and GVB (1.1%). Mixed infections with two, three of four different viruses were also common in both collections. In the National collection the most common mixed infections were GLRaV-3 + GVA (15.8%) and GLRaV-1 + GLRaV-3 + GVA (14.7%), while in the Risika collection dominant were mixed infections with GLRaV-3 + GVA (10.5%) and GFLV + GLRaV-3 (8.4%). Free of all eight tested viruses were ten vines (10.5%) in the National collection and only seven vines (7.4%) in the Risika collection. This investigation has demonstrated that there has been deteriorated sanitary status of Croatian autochthonous cultivars, and indicates the need for the production of certified virus-free planting material.

Population size and incidence of virus infection in free-living populations ofCucurbita pepo

Impact assessments of virus resistance transgene introgression into wild, free-living populations are important for determining whether these transgenes present a risk to agriculture or the environment. Transgenic virus-resistant Cucurbita pepo ssp. ovifera var. ovifera L. (squash) cultivars have been commercialized, and may be cultivated in close proximity to cross-compatible wild, free-living relatives (C. pepo subsp. pepo vars. ozarkana and texana). Therefore, the potential impact of these virus resistance transgenes was studied by surveying the incidence and fluctuations of virus infection (as assayed by ELISA), virus symptoms (which may not be seen in an infected plant) and population size in forty-three free-living C. pepo populations in Illinois, Missouri, Arkansas, Mississippi, Louisiana, and Texas. Ten of these populations were studied over three consecutive seasons. Depending on the year, 61% to 78% percent of the populations had at least one individual infected by at CMV, ZYMV or WMV2, but the median incidence of infection within populations was 13%. The observed infection level in free-living populations was consistent with levels defined as "low" in field plot experiments conducted by others, leading to the conclusion that transgenic virus resistance should not provide a significant fitness advantage to the free-living populations examined. Viral symptoms were detected in only 2% of plants observed, indicating that severity of viral infection was low. CMV, ZYMV, and WMV2 were not the only viruses infecting these populations, further reducing the likelihood that resistance to these viruses would release populations from constraints imposed by virus diseases.

Characterisation ofApple chlorotic leaf spot virus infecting almonds in India

Restricted field surveys were conducted to determine the presence and incidence of virus infections in almonds. Representative asymptomatic samples from six locations were tested by enzyme linked immunosorbent assay and reverse transcription and polymerase chain reaction for known stone fruit viruses. OnlyApple chlorotic leaf spot virus (ACLSV) infection was detected in one of the six almond samples from the state of Himachal Pradesh. Comparison of sequenced amplicons with two available sequences of ACLSV-almond isolates revealed 92% and 94% amino acid identity. However, the Indian ACLSV-almond isolate shared maximum (98%) homology at the amino acid level to ACLSV-peach (AM498050) and wild apricot (AM498048) isolates from India. The C-terminus is highly conserved within the Indian ACLSV isolates with the exception of a few residues which in the case of the Indian almond isolates are more typical of peach and wild apricot isolate sequences.

Characterisation ofApple chlorotic leaf spot virusinfecting almonds in India

Restricted field surveys were conducted to determine the presence and incidence of virus infections in almonds. Representative asymptomatic samples from six locations were tested by enzyme linked immunosorbent assay and reverse transcription and polymerase chain reaction for known stone fruit viruses. Only Apple chlorotic leaf spot virus (ACLSV) infection was detected in one of the six almond samples from the state of Himachal Pradesh. Comparison of sequenced amplicons with two available sequences of ACLSV-almond isolates revealed 92% and 94% amino acid identity. However, the Indian ACLSV-almond isolate shared maximum (98%) homology at the amino acid level to ACLSV-peach (AM498050) and wild apricot (AM498048) isolates from India. The C-terminus is highly conserved within the Indian ACLSV isolates with the exception of a few residues which in the case of the Indian almond isolates are more typical of peach and wild apricot isolate sequences.

First Report of Zucchini yellow mosaic virus in Cucumber (Cucumis sativus) in India.

In August of 2002, cucumber (Cucumis sativus L. cv. Himangi) plants grown in commercial fields in Pune, western Maharashtra, India, exhibited chlorotic spots, veinal chlorosis, mosaic, blister formation and shoestring symptoms on leaves, stunted growth, and distortion of fruits. Incidence of virus infection in the fields varied from 25 to 38%. Crude sap extracted from infected cucumber leaf samples was inoculated mechanically onto cucumber and indicator host plants. The inoculated glasshouse-grown cucumber plants showed virus symptoms similar to those observed in the field. The virus produced chlorotic local lesions on Chenopodium amaranticolor and chlorotic spots followed by veinal chlorosis, mosaic, vein banding, and leaf distortion on Citrullus lanatus, C. melo, C. sativus, Cucurbita maxima, Cucurbita pepo, Luffa acutangula, and Trichosanthes anguina. The virus did not infect Nicotiana benthamiana, N. glutinosa, and N. tabacum cv. White Burley (1,2). Cucumber and indicator plants were tested using direct antigen coating enzyme-linked immunosorbent assays. A positive reaction was obtained with monoclonal antiserum to Zucchini yellow mosaic virus (ZYMV) but not with antisera to Papaya ringspot virus-P, Cucumber mosaic virus, and Watermelon mosaic virus (Agdia, Inc., Elkhart, IN). The disease was observed again in the field during July to September 2003. Natural infection of zucchini (Cucurbita pepo) by ZYMV has been reported previously from India (3). To our knowledge, this is the first report of ZYMV in cucumber in India.

Incidence of virus infection as a cause of Meniere's disease or endolymphatic hydrops assessed by electrocochleography.

Meniere's disease (MD) may follow viral infection such as by neurotropic viruses known to invade the endolymphatic sac (ES) and provoke endolymphatic hydrops (EH). The objective of this study was to investigate whether neurotropic viruses may cause infection of the inner ear and provoke EH. Antiviral immunoglobulin (IgG) assay against herpes simplex 1 (HSV1), herpes simplex 2 (HSV2), adenovirus (ADV), varicella zoster virus (VZV) and cytomegalovirus (CMV) were performed in 109 patients with an advanced stage of MD and compared with those obtained from 26 patients operated on because of vestibular schwannoma (VS), who served as a control group, to evaluate whether there is an association between the IgG levels and the ECoGs summating potential/action potential ratio (SP/AP ratio) in the MD group. In MD patients, the IgG titre against VZV and ADV were significantly higher than in the control (schwannoma) group. However, no correlation was found between the IgG levels against ADV and VZV with the SP/AP ratio. Neurotropic viruses such VZV and ADV may play a role in the pathogenesis of MD, despite the absence of association between the levels of IgG titres and the SP/AP ratio.

Identification and distribution of viruses infecting sweet potato in Kenya

SummaryFour hundred and forty‐eight symptomatic and 638 asymptomatic samples were collected from sweet potato fields throughout Kenya and analysed serologically using antibodies to Sweet potato feathery mottle virus (SPFMV), Sweet potato chlorotic stunt virus (SPCSV), Sweet potato mild mottle virus (SPMMV), Cucumber mosaic virus (CMV), Sweet potato chlorotic fleck virus (SPCFV), Sweet potato latent virus (SwPLV), Sweet potato caulimo‐like virus (SPCaLV), Sweet potato mild speckling virus (SPMSV) and C‐6 virus in enzyme‐linked immunosorbent assays (ELISA). Only SPFMV, SPMMV, SPCSV, and SPCFV were detected. Ninety‐two percent and 25% of the symptomatic and asymptomatic plants respectively tested positive for at least one of these viruses. Virus‐infected plants were collected from 89% of the fields. SPFMV was the most common and the most widespread, detected in 74% of the symptomatic plants and 86% of fields surveyed. SPCSV was also very common, being detected in 38% of the symptomatic plants and in 50% of the fields surveyed. SPMMV and SPCFV were detected in only 11% and 3% of the symptomatic plant samples respectively. Eight different combinations of these four viruses were found in individual plants. The combination SPFMV and SPCSV was the most common, observed in 22% of symptomatic plants. Virus combinations were rare in the asymptomatic plants tested. Incidence of virus infection was highest (18%) in Kisii district of Nyanza province and lowest (1%) in Kilifi and Malindi districts of Coast province.

Incidence of virus infection in experimental plots, commercial crops, and seed stocks of cool season crop legumes

Experimental plots of cool season crop legumes growing at diverse locations in Western Australia were inspected for plants with suspect virus symptoms over 4 growing seasons (1994, 1997, 1998, 1999), and plant samples were tested for infection with alfalfa mosaic (AMV), bean yellow mosaic (BYMV), cucumber mosaic (CMV), and pea seed-borne mosaic (PSbMV) viruses. All 4 viruses were detected in faba bean (Vicia faba); BYMV, CMV, and PSbMV in field pea (Pisum sativum); AMV, CMV, and PSbMV in lentil (Lens culinaris); and AMV and CMV in chickpea (Cicer arietinum). Among minor crop species, AMV, BYMV, and CMV were found in narbon bean (V. narbonensis) and grass pea (Lathyrus sativus); BYMV and CMV in dwarf chickling (L. cicera); BYMV in bitter vetch (V. e r v i l i a ) and L. clymenum; and AMV in fenugreek (Trigonella foenum-graecum). Incidences of individual viruses varied widely from site to site but plot infection sometimes reached 100%. Symptom severity varied widely with virus–crop combination. In large-scale surveys of commercial crops of field pea and faba bean over 2 (1998, 1999) and 3 (1994, 1998, 1999) growing seasons, respectively, randomly collected samples from each crop were tested for presence of AMV, BYMV, CMV, and PSbMV. In 1999 they were also tested for beet western yellows virus (BWYV). All 5 viruses were detected in both species. BWYV was found in 35% of faba bean and 56% of the field pea crops sampled in 1999, with incidences of infection in individual crops up to 40% and 49%, respectively. PSbMV was found in 42% and BYMV in 18% of field pea crops in 1999. In individual crops, highest infection incidences of BYMV and PSbMV detected were 31% for BYMV in faba bean in 1998 and 9% for PSbMV in field pea in 1999. CMV and AMV incidences in both species never exceeded 7% of crops or 4% of plants within individual crops. Infection by 2 different viruses within individual crops was common, even 3 were sometimes found. Cultivars infected with most viruses were Fiesta and Fiord for faba bean, and Dundale, Laura, and Magnet for field pea. BYMV was detected in the crop tested of dwarf chickling. In tests on seed samples from Western Australia of 30 commercial seed stocks of field pea, 11 of faba bean, and 50 of chickpea, PSbMV was detected in 11, 1, and 1, respectively; CMV in 1, 1, and 3; BYMV in 3, 1, and 0; and AMV in 0, 0, and 1. This appears to be the first record of seed transmission of CMV in pea and faba bean. Seed samples from Victoria were also found to contain viruses: PSbMV in pea and AMV in lentil. Widespread infection with viruses in evaluation plots and commercial crops of cool season crop legumes is a cause for concern, especially where individual crop incidences are high and 2 or more viruses are present. Sowing of infected seed stocks leads to introduction of randomly dispersed sources of virus infection within the crop sown, resulting in spread of infection and yield losses. Appropriate control measures are discussed.

Five viruses in Narcissus spp. from New Zealand

Narcissus spp., showing virus-like symptoms from Otago Province New Zealand, were surveyed for viruses using ELISA and mechanical transmission tests. High incidence of virus infection was detected at five sites. Cucumber mosaic virus, Narcissus latent virus, Narcissus mosaic virus, Narcissus tip necrosis virus, and Narcissus yellow stripe virus (NYSV) were detected, but not Tobacco rattle virus, the only virus previously reported from Narcissus spp. in New Zealand. There was a high incidence of NYSV in infected plants both as single and mixed infections.

Further studies on the incidence of virus infection in white clover pastures

Leaf samples of white clover were collected from 19 irrigated white clover (Trifolium repens) pastures in the south-west of Western Australia and tested for virus infection by enzyme-linked immunosorbent assay. Clover yellow vein virus (CYVV) was found in 16 pastures at infection levels of up to 23% and white clover mosaic virus (WCMV) in 10 at levels up to 83%. None of the white clover pastures with a high incidence of WCMV had been resown with white clover within the last 10 years, whereas those resown within the last 5 years had little or no infection. As previously reported in tests on different white clover pastures in the same irrigation area, widespread infection with alfalfa mosaic virus (AMV) and occasional infection with subterranean clover red leaf virus (SCRLV) was also found. Two or more viruses were found within 16 of the pastures with at least 3 having all 4 viruses. AMV and WCMV were detected in flatweed (Hypochaeris glabra) and AMV was detected in clustered dock (Rumex conglomeratus), both commonly occurring weeds in the pastures. In tests on the perennial ryegrass (Lolium perenne) component of 18 white clover pastures, infection with barley yellow dwarf virus was found in 14 at levels up to 5%. In addition, 11 of the pastures contained a virus which reacted with potyvirus-specific monoclonal antibodies, presumably ryegrass mosaic virus (RyMV), which was detected at levels up to 34%. Live aphids were trapped at 8 different times during 1995 in one pasture that was infected with WCMV, CYVV, AMV, and SCRLV. Blue-green aphid (Acyrthosiphon kondoi) and oat aphid (Rhopalosiphum padi) were the only species caught, both reaching peak populations in midwinter, but only the latter was found in summer. No virus transmission was detected when the aphids caught were fed individually on subterranean clover (T. subterraneum) indicator plants. It is concluded that WCMV poses a threat to the productivity of white clover within irrigated pastures, especially when present in mixed infection with AMV. CYVV is also commonly found but normally not at high enough incidences to pose a serious threat. RyMV may pose a threat to the productivity of the perennial ryegrass component within white clover-based pastures.

National survey of viruses in pastures of subterranean clover. I. Incidence of four viruses assessed by ELISA

A nationwide survey was made of the time-course incidence of alfalfa mosaic virus (AMV), clover yellow vein virus (CYVV), subterranean clover mottle virus (SCMoV) and subterranean clover red leaf virus (SCRLV) in improved pastures in southern regions of Australia over a 3-year period. Up to 2 500 samples (cvv. Mt Barker or Woogenellup) were collected in winter and spring of 1984, 1985 and 1986 in each of New South Wales, Victoria, South Australia. Western Australia and Tasmania, and assayed by ELISA. Usually, each sample consisted of one or two plants or parts thereof. However, a small number of samples in winter contained parts of up to 10 seedlings. For this reason, incidences are expressed as percentage of infected samples rather than percentages of infected plants. All four viruses occurred in all five states. Averaged over all states, the incidence of infected samples increased progressively from 15.3 to 19.9 to 22.5% from 1984 to 1985 to 1986, respectively, in spring, and from 6.8 to 13.8 to 18.8% respectively in winter. The incidence of samples infected with multiple infections (2-4 viruses) increased from 1.9 to 3.2 to 5.0% from 1984 to 1985 to 1986, respectively, in spring, and from 0.5 to 1.6 to 4.0%, respectively, in winter. Since 1-4 viruses were detected in each infected sample, more individual infections than infected samples were recorded. For example, the incidence of virus infections per paddock increased progressively from 17.5 to 24.1 to 28.6% from 1984 to 1985 to 1986, respectively, in spring. On a state basis, the incidence of infected samples was greatest in W.A., reaching 38.9 and 34.9% in spring of 1985 and 1986, respectively, and in S.A. reaching 30.3% in spring of 1986; these high levels were due largely to SCMoV which reached 97% in one paddock in each of the two states. In N.S.W., Vic. and Tas., the highest incidences of infected samples in either winter or spring were 21.4, 16.2 and 23.1%, respectively. Averaged over all states, the highest mean incidence recorded for samples infected with individual viruses in either winter or spring was 9.4% for AMV, 5.7% for CYW, 10.9% for SCMoV and 7.5% for SCRLV. For AMV and SCRLV, there was an increasing trend from spring 1984 to spring 1986. A similar increasing trend for SCMoV was more evident in winter than in spring. For CYVV, no time-course pattern was evident. These results support the proposition that viruses contribute significantly to 'clover-decline', a well-known problem in pastures of subterranean clover.

AERIAL APPLICATION OF NUCLEAR POLYHEDROSIS VIRUS AGAINST DOUGLAS-FIR TUSSOCK MOTH, ORGYIA PSEUDOTSUGATA (McDUNNOUGH) (LEPIDOPTERA: LYMANTRIIDAE): I. IMPACT IN THE YEAR OF APPLICATION

AbstractFour 10-ha plots located in Kamloops Forest District, British Columbia, containing Douglas-fir trees infested with Douglas-fir tussock moth were aerially sprayed with nuclear polyhedrosis virus (Virtuss) in 1982 when most larvae were in the first instar. A dosage of 2.5 × 1011 polyhedral inclusion bodies (PIB) per hectare was applied in an emulsifiable oil tank mix to one plot and the same dosage in an aqueous tank mix containing molasses was applied to a second plot. The remaining two plots were treated with dosages of 8.3 × 1010 and 1.6 × 1010 PIB per hectare, respectively, in the oil mix. The treatments were applied with a fixed-wing aircraft fitted with boom and nozzle equipment and calibrated to deliver 9.4 L/ha. A further four plots were selected as checks.Population reduction at 6 weeks post-spray (calculated using a modified Abbott’s formula) was 65% in the plot receiving the lowest dosage and from 87 to 95% in the remaining three plots. Incidence of virus infection, determined microscopically, peaked at 5–6 weeks post-spray with 85–100% of the larvae scored as positive. Levels of naturally occurring virus remained low in the check plots. Adult emergence from the pupae collected in the treated plots ranged from 4 to 19% and from 28 to 43% in the check plots. Reduction in egg-mass density attributed to the treatments was 97% in one plot, 99% in two others, and not determined for the fourth.A virus dosage of 8.3 × 1010 PIB per hectare, which is one-third of the previously recommended dosage, is adequate, and either tank mix is acceptable.

Incidence of yellows in sugar beet as affected by variation in plant density and arrangement

AbstractAphid species found infesting sugar-beet in Tasmania were Aphis craccivora Koch, Aulacorthum solani (Kalt), Macrosiphum euphorbiae (Thos.) and Myzus persicae (Sulz.). The activity of infective alatae over plots of sugar-beet established by sowing at different densities and arrangements to produce 12 treatments was gauged by recording the numbers of plants which became affected with virus yellows symptoms. The incidence of yellows increased as plant density decreased and as plant arrangement altered from rectangular to more square patterns. A regression equation of the form: where a, b, c and d were constants and x and y the intra- and interrow spacings, respectively, accounted for 92% of the variation produced by the 12 treatments. These results indicate that the incidence of virus infection in row crops resulting from aphid flight activity may be manipulated through altering plant density and arrangement.

Horizontal transmission of lymphoid leukosis virus. influence of age, maternal antibodies and degree of contact exposure

Eight groups of 1-day-old or 8-week-old chickens were exposed by contact to lymphoid leukosis virus (LLV) infection. Five groups of about 60 spf chickens were used. Three groups of the same size were progeny from LLV vaccinated hens. Five groups were housed in one chicken house in close contact with a large number of immunologically tolerant chickens (virus "spreaders"). On two occasions infectious LLV was recovered from air/dust samples collected in this house. In the second house a small number of congenitally infected birds generated a mild degree of LLV exposure. It was demonstrated that infection by contact may lead to lymphoma formation and congenital virus transmission. The incidence of virus infection and LL mortality in the groups of birds exposed at 8 weeks of age were significantly lower than in chickens exposed at 1 day of age. In addition, about 100-fold differences in numbers of LLV-associated white blood cells were observed between both age groups. These results indicate that in addition to resistance to tumour formation, resistance to LLV infection develops in the chicken with increasing age. Maternal antibodies, present in three groups exposed at 1 day of age, reduced the rate of infection and the incidence of LL.

Further studies on the mode of transmission of herpes-like virus in guinea pigs.

SummaryHartley guinea pigs can be infected with HLV by various routes of inoculation. These animals were found to be uniformly susceptible to intranasal inoculation of 3.0 log TCID50 of virus. Infection could also be achieved by oral inoculation. Four out of 7 animals inoculated orally had virus in their blood. Contact infection was achieved in 2 out of 7 animals that were housed with or adjacent to infected ones. Incidence of virus infection in newborns from both intraperitoneally inoculated or naturally infected parents was low, but the frequency increased to 59% or higher when the offspring were 6 months of age or older. No virus was isolated from the offspring of intracerebrally inoculated guinea pigs.