Expansion of the Cassava Brown Streak Disease Epidemic in Eastern Democratic Republic of Congo.

Cassava plays a key role in ensuring food security and generating income for smallholder farmers throughout Central Africa, particularly in the Democratic Republic of Congo (DRC). This status is threatened, however, by cassava brown streak disease (CBSD), which has expanded its incidence and range in eastern DRC. The study described here comprises the first extensive assessment of temporal change in the occurrence of CBSD and its causal viruses in DRC, based on surveys conducted during 2016 and 2018. Cassava fields were inspected in Ituri, Nord-Kivu, Sud-Kivu, Tanganyika, and Haut-Katanga provinces within eastern DRC to record foliar incidence and severity of CBSD. Leaf samples were collected for virus detection and species-level identification. New occurrences of CBSD, confirmed by virus diagnostic tests, were recorded in two provinces (Haut-Katanga and Sud-Kivu) and nine previously unaffected territories, covering an area of >62,000 km2, and at up to 900 km from locations of previously published reports of CBSD in DRC. Overall, average CBSD incidence within fields was 13.2% in 2016 and 16.1% in 2018. In the new spread zone of Haut-Katanga, incidence increased from 1.7 to 15.9%. CBSD is now present in provinces covering 321,000 km2, which is approximately 14% of the total area of DRC. This represents a major expansion of the CBSD epidemic, which was only recorded from one province (Nord-Kivu) in 2012. Both Cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus were detected in Ituri, Nord-Kivu, and Sud-Kivu, but only CBSV was detected in Haut-Katanga. Overall, these results confirm the increasing threat that CBSD poses to cassava production in DRC and describe an important expansion in the African pandemic of CBSD.

Spatial Analysis of Temporal Changes in the Pandemic of Severe Cassava Mosaic Disease in Northwestern Tanzania.

To improve understanding of the dynamics of the cassava mosaic disease (CMD) pandemic front, geospatial approaches were applied to the analysis of 3 years' data obtained from a 2-by-2° (approximately 222-by-222 km) area of northwestern Tanzania. In total, 80 farmers' fields were assessed in each of 2009, 2010, and 2011, with 20 evenly distributed fields per 1-by-1° quadrant. CMD-associated variables (CMD incidence, CMD severity, vector-borne CMD infection, and vector abundance) increased in magnitude from 2009 to 2010 but showed little change from 2010 to 2011. Increases occurred primarily in the two westernmost quadrants of the study area. A pandemic "front" was defined by determining the values of CMD incidence and whitefly abundance where predicted disease gradients were greatest. The pandemic-associated virus (East African cassava mosaic virus-Uganda) and vector genotype (Bemisia tabaci sub-Saharan Africa 1-subgroup 1) were both present within the area bounded by the CMD incidence front but both also occurred ahead of the front. The average speed and direction of movement of the CMD incidence front (22.9 km/year; southeast) and whitefly abundance front (46.6 km/year; southeast) were calculated, and production losses due to CMD were estimated to range from US$4.3 million to 12.2 million.

A Risk Assessment Framework for Seed Degeneration: Informing an Integrated Seed Health Strategy for Vegetatively Propagated Crops.

Pathogen buildup in vegetative planting material, termed seed degeneration, is a major problem in many low-income countries. When smallholder farmers use seed produced on-farm or acquired outside certified programs, it is often infected. We introduce a risk assessment framework for seed degeneration, evaluating the relative performance of individual and combined components of an integrated seed health strategy. The frequency distribution of management performance outcomes was evaluated for models incorporating biological and environmental heterogeneity, with the following results. (1) On-farm seed selection can perform as well as certified seed, if the rate of success in selecting healthy plants for seed production is high; (2) when choosing among within-season management strategies, external inoculum can determine the relative usefulness of 'incidence-altering management' (affecting the proportion of diseased plants/seeds) and 'rate-altering management' (affecting the rate of disease transmission in the field); (3) under severe disease scenarios, where it is difficult to implement management components at high levels of effectiveness, combining management components can be synergistic and keep seed degeneration below a threshold; (4) combining management components can also close the yield gap between average and worst-case scenarios. We also illustrate the potential for expert elicitation to provide parameter estimates when empirical data are unavailable. [Formula: see text] Copyright © 2017 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Analysis of Interactions Between Cassava Brown Streak Disease Symptom Types Facilitates the Determination of Varietal Responses and Yield Losses.

Cassava brown streak disease (CBSD), caused by cassava brown streak viruses, is recognized as one of the most important plant disease threats to African food security. This study describes the incidence and severity of the different symptom types caused by CBSD, derived from extensive surveys in the country most severely affected by the disease: Tanzania. Total plant incidence and mean root severity of CBSD, recorded from 341 farmers' fields, were both greater in the Coast Zone (49.5% and 3.05), than in the Lake Zone (32.7% and 2.57). Overall, the differing incidences recorded declined in the following order: total plant incidence (39.1%), plant shoot incidence (33.4%), plant root incidence (19.3%), root incidence (10.5%), and unusable root incidence (5.4%). The much lower-than-anticipated loss due to the root necrosis that is characteristic of CBSD was offset by large reductions of root number in plants expressing foliar symptoms of CBSD (15.7% in the Coast Zone and 5.5% in the Lake Zone). These data suggest that the effects of CBSD on the growth of affected plants are greater than those due to root spoilage. Based on these two factors, annual losses due to CBSD in the parts of Tanzania surveyed were estimated at >860,000 t, equivalent to more than U.S.$51 million. A novel approach to using farm-derived data on the responses of the most frequently cultivated varieties to CBSD infection allowed the grouping of the varieties into four categories, based on their relative resistance or tolerance to infection. This tool should be of value to breeders in identifying and selecting for sources of resistance or tolerance in both local and exotic germplasm, and should ultimately contribute to enhancing the management of one of Africa's most damaging crop diseases.

The Dynamics and Environmental Influence on Interactions Between Cassava Brown Streak Disease and the Whitefly, Bemisia tabaci.

Cassava brown streak disease (CBSD) is currently the most significant virus disease phenomenon affecting African agriculture. In this study, we report results from the most extensive set of field data so far presented for CBSD in Africa. From assessments of 515 farmers' plantings of cassava, incidence in the Coastal Zone of Tanzania (46.5% of plants; 87% of fields affected) was higher than in the Lake Zone (22%; 34%), but incidences for both zones were greater than previous published records. The whitefly vector, Bemisia tabaci, was more abundant in the Lake Zone than the Coastal Zone, the reverse of the situation reported previously, and increased B. tabaci abundance is driving CBSD spread in the Lake Zone. The altitudinal "ceiling" previously thought to restrict the occurrence of CBSD to regions <1,000 masl has been broken as a consequence of the greatly increased abundance of B. tabaci in mid-altitude areas. Among environmental variables analyzed, minimum temperature was the strongest determinant of CBSD incidence. B. tabaci in the Coastal and Lake Zones responded differently to environmental variables examined, highlighting the biological differences between B. tabaci genotypes occurring in these regions and the superior adaptation of B. tabaci in the Great Lakes region both to cassava and low temperature conditions. Regression analyses using multi-country data sets could be used to determine the potential environmental limits of CBSD. Approaches such as this offer potential for use in the development of predictive models for CBSD, which could strengthen country- and continent-level CBSD pandemic mitigation strategies.

Widespread occurrence and diversity of Cassava brown streak virus (Potyviridae: Ipomovirus) in Tanzania.

Cassava brown streak disease (CBSD) has been a problem in Tanzania since 1936. Existing literature indicated limited distribution of the disease to low altitudes, usually <100 m above sea level, but the current geographical distribution of the disease was not known. Whether a single or many strains for the virus exist in Tanzania had not been reported to date. In this study, CBSD was recorded from sea level to ≈1,800 m above sea level. In total, 2,730 cassava plants were assessed for CBSD leaf symptoms in 91 fields and root symptoms were assessed at 81 sites. A sample was taken from each site for laboratory screening for Cassava brown streak virus (CBSV). CBSD mean foliar and root incidences were 38 and 36%, respectively. Reverse-transcription polymerase chain reaction of a partial 3'-terminal coat protein (CP) region of CBSV indicated the presence of CBSV in 67 of the 91 (73%) samples. Forty-three amplicons were sequenced, and phylogenetic comparisons with nucleotide sequences from GenBank (National Center for Biotechnology Information database) suggested that one major clade of CBSV primarily exists in Tanzania. However, there was nucleotide sequence divergence of up to 19% among the 42 isolates. In all, 42 of the 43 sequences had 80 to 100% nucleotide identity with 6 previously reported CP-CBSV sequences (from Mozambique and Tanzania). In total, 13 of 42 isolates had <80% nucleotide identities with three previously reported Ugandan CBSV sequences. One isolate, FJ687177, shared <78% sequence identity with the other Tanzanian sequences but was closely related (93%) to Ugandan isolates. It is likely that isolate FJ687177 may belong to a less widely distributed recently described species (clade 2) of CBSV, named Ugandan cassava brown streak virus (UCBSV).

Identification and functional analysis of the ezrin-binding site in the hyaluronan receptor, CD44.

ERM (ezrin, radixin and moesin) proteins function as linkers between the actin cytoskeleton and the plasma membrane. In addition to this structural role, these proteins are highly regulatable making them ideal candidates to mediate important physiological events such as adhesion and membrane morphology and to control formation and breakdown of membrane-cytoskeletal junctions. Recently, a direct interaction in vitro has been demonstrated between ERM proteins and the hyaluronan receptor, CD44. We have mapped the ezrin-binding site to two clusters of basic amino acids in a membrane-proximal 9 amino-acid region within the CD44 cytoplasmic domain. To investigate the functional importance of this interaction in vivo, we created a number of mutations within full-length CD44 and expressed these mutants in human melanoma cells. We demonstrate here that mutations within the ezrin-binding site do not disrupt the plasma membrane localization of CD44 and, in addition, that this region is not required to mediate efficient hyaluronan binding. These studies suggest that ERM proteins mediate the outside-in, rather than inside-out, signalling of adhesion receptors.

Molecular biodiversity of cassava begomoviruses in Tanzania: evolution of cassava geminiviruses in Africa and evidence for East Africa being a center of diversity of cassava geminiviruses.

Cassava is infected by numerous geminiviruses in Africa and India that cause devastating losses to poor farmers. We here describe the molecular diversity of seven representative cassava mosaic geminiviruses (CMGs) infecting cassava from multiple locations in Tanzania. We report for the first time the presence of two isolates in East Africa: (EACMCV-[TZ1] and EACMCV-[TZ7]) of the species East African cassava mosaic Cameroon virus, originally described in West Africa. The complete nucleotide sequence of EACMCV-[TZ1] DNA-A and DNA-B components shared a high overall sequence identity to EACMCV-[CM] components (92% and 84%). The EACMCV-[TZ1] and -[TZ7] genomic components have recombinations in the same genome regions reported in EACMCV-[CM], but they also have additional recombinations in both components. Evidence from sequence analysis suggests that the two strains have the same ancient origin and are not recent introductions. EACMCV-[TZ1] occurred widely in the southern part of the country. Four other CMG isolates were identified: two were close to the EACMV-Kenya strain (named EACMV-[KE/TZT] and EACMV-[KE/TZM] with 96% sequence identity); one isolate, TZ10, had 98% homology to EACMV-UG2Svr and was named EACMV-UG2 [TZ10]; and finally one isolate was 95% identical to EACMV-[TZ] and named EACMV-[TZ/YV]. One isolate of African cassava mosaic virus with 97% sequence identity with other isolates of ACMV was named ACMV-[TZ]. It represents the first ACMV isolate from Tanzania to be sequenced. The molecular variability of CMGs was also evaluated using partial B component nucleotide sequences of 13 EACMV isolates from Tanzania. Using the sequences of all CMGs currently available, we have shown the presence of a number of putative recombination fragments that are more prominent in all components of EACMV than in ACMV. This new knowledge about the molecular CMG diversity in East Africa, and in Tanzania in particular, has led us to hypothesize about the probable importance of this part of Africa as a source of diversity and evolutionary change both during the early stages of the relationship between CMGs and cassava and in more recent times. The existence of multiple CMG isolates with high DNA genome diversity in Tanzania and the molecular forces behind this diversity pose a threat to cassava production throughout the African continent.

Cassava mosaic virus disease in East Africa: a dynamic disease in a changing environment.

Cassava mosaic disease (CMD), now known to be caused by cassava mosaic geminiviruses (Family Geminiviridae; Genus Begomovirus), was first reported in East Africa in 1894. Epidemics occurred in Madagascar and Uganda in the 1930s and 1940s, and more localised rapid spread of CMD was observed in parts of coastal Tanzania in the 1930s and coastal Kenya in the 1970s. During the 1990s, a major regional pandemic of an unusually severe form of CMD has expanded to affect parts of at least five countries, causing massive economic losses and destabilising food security. Mechanisms responsible for the development and progress of the pandemic have been described, and comparisons of epidemiological data for varieties grown throughout the period under review suggest that the recent pandemic has been characterised by rapid rates of CMD spread hitherto unknown in East Africa. A key factor in the genesis and spread of the pandemic has been the recombination between two distinct cassava mosaic geminiviruses to produce a novel and more virulent hybrid. Although such events may be common, the known history of CMD in East Africa suggests that the frequency with which they become epidemiologically significant is low. A corollary of this is that resistance, developed originally in Tanzania between 1934 and 1960, and utilized and supplemented at the International Institute of Tropical Agriculture, Nigeria, since 1971, is providing effective CMD control in current pandemic-affected areas of East Africa. Consequently, it is concluded that prospects for managing CMD in the 21st century are good, and that the approach adopted should build on the model of collaborative research and implementation that has been established in tackling the current CMD pandemic.

Methods of surveying the incidence and severity of cassava mosaic disease and whitefly vector populations on cassava in Africa: a review.

Field surveys in many cassava growing areas of Africa have assessed the incidence and severity of cassava mosaic disease (CMD), populations of the whitefly vector (Bemisia tabaci), and the distribution of cassava mosaic begomoviruses (CMBs). The methods employed differ greatly between countries and attempts at standardization were made in recent CMD surveys in East and Central Africa, notably in the systemwide Whitefly IPM Project, which provides a paradigm for future work on CMBs and whiteflies on cassava in Africa and also elsewhere. However, there is a need for greater standardization so as to assess the continued expansion of the current CMD pandemic in eastern Africa. Standardized methods will facilitate the collection of reliable data, which can be used to predict future disease spread, develop appropriate management strategies and compare disease development between seasons and locations. In this review, the methods used and the problems encountered during such surveys are discussed and recommendations made on future procedure.

Drug-related test patterns of depressed patients.

Several types of drugs reportedly have been useful in treating depressions, but the specific effects of these drugs on functioning remain unclear. Forty-nine hospitalized depressed patients were randomly assigned on a double-blind basis to an imipramine, chlorpromazine or placebo group. Psychological test performance was compared after 3 weeks of in-hospital drug treatment. Neither drug produced impairment on most measures of intellectual functioning. The results suggest imipramine may impair ability to assimilate and retain information, and that chlorpromazine may impair sustained attention. The differential effects were discussed in relation to symptoms, and to hypotheses about the relationship between arousal and chlorpromazine and between retardation and imipramine in the treatment of depression.

Prevention of HIV transmission.

Primary care physicians continue to play an important role in preventing HIV transmission by targeting messages to their high-risk patients. The risk of HIV transmission cannot be eliminated entirely; however, clinicians have a variety of prevention interventions at their disposal. Behavioral and therapeutic interventions offered in a client-centered environment have the greatest chance of success. Patients can benefit from individualized prevention plans that decrease risk by treating drug addiction and by modifying sexual and drug-taking behaviors. The risk of HIV infection in health care workers can be reduced by strict adherence to universal precautions and the use of postexposure antiretroviral therapy.

Symptom management in HIV-infected patients.

HIV infection predisposes patients to many opportunistic infections that can be treated readily once they are diagnosed. Diagnosis is sometimes difficult because these complications may be unfamiliar, and even familiar diseases present atypically in the setting of HIV. Several clinical syndromes that are common in HIV patients are described. Discussion of each syndrome includes differential diagnosis, diagnostic evaluation, and interval symptomatic treatment to alleviate distress, pending definitive treatment.

The prevalence of beta-lactamase producing bacteria in subgingival plaque and their sensitivity to Augmentin.

Subgingival plaque samples from 20 patients with chronic periodontitis who had received no antibiotics for at least 3 months were screened for the presence of beta-lactamase-producing bacteria. Thirteen of the patients harboured beta-lactamase producing bacteria, most of which were members of the genus Bacteroides. The most frequently isolated species were Bacteroides melaninogenicus and Bacteroides capillosus which are often implicated in acute oral infections. All of the beta-lactamase-producing bacteroides strains were sensitive to a combination of amoxycillin with clavulanic acid (Augmentin).

Asthma--the changing face of drug therapy.

Until the recent introduction of long acting beta 2-agonists and the leukotriene antagonists, the drug treatment of asthma had remained largely unchanged for a quarter century. Recent studies have demonstrated the efficacy of the long acting beta 2-agonists in the management of asthma in children and highlighted their value as an adjunct to inhaled corticosteroids. The leukotriene antagonists are an important new class of drug therapy which target a specific area of asthma pathogenesis. Whilst they have been shown to be effective for asthma, their exact role in the clinical situation remains to be established. Recent guidelines have emphasised the important role of inflammation in persistent asthma and recommended the early institution of anti-inflammatory treatment. Many patients remain uncontrolled despite high doses of anti-inflammatory agents including oral corticosteroids. Recent experience with other immunomodulatory agents such as cyclosporin, methotrexate and intravenous immunoglobulin has highlighed their potential as steroid sparing agents. With improved understanding of asthma pathogenesis the potential for specific targeted therapies has become evident. Monoclonal antibodies to IgE and certain cytokines are being investigated as possible treatments for asthma. Similarly, preliminary studies of selective phosphodiesterase inhibitors in asthmatic individuals have been encouraging. Other potential therapies include platelet-activating factor receptor antagonists, tryptase inhibitors and prostaglandin E analogs. The continued development of such targeted treatments should ensure a greater diversity of therapeutic options for the management of asthma in the new millennium.

Provider efforts to increase mammography screening.

This article examines barriers to mammography screening and reviews the professional literature on provider interventions to increase screening. Interventions appropriate for radiologic technologists are evaluated and discussed in an effort to expand R.T.s' role in improving mammography screening rates.

Doctorally prepared R.T.s: a professional profile.

Registered radiologic technologists holding doctoral degrees were surveyed to establish demographic and professional profiles. In addition, the scholarly production of this unique group was quantified by self-reports. A majority of respondents (67%) were not employed in the radiologic sciences and most had not authored journal articles, books or submitted grant proposals. Doctorally prepared technologists reported several professional and personal benefits in earning the degree, including self-fulfillment, respect and advanced occupational opportunities.