Diversity of microsporidia (Fungi: Microsporidia) among captive great apes in European zoos and African sanctuaries: evidence for zoonotic transmission?

Abstract: Two hundred and seventeen captive great apes (150 chimpanzees, Pan troglodytes; 14 bonobos, Pan paniscus; 53 western gorillas, Gorilla gorilla) and 20 personnel from thirteen European zoos and two African sanctuaries were sampled and examined in order to determine the occurrence ofEnterocytozoon bieneusi and species of Encephalitozoon in faecal specimens and to compare the epidemiological situation between zoos and sanctuaries. Microsporidia were detected at all sampling sites. Sequence analyses of ITS amplicons generated by using microsporidia-specific primers determined the presence ofmicrosporidia in 87 samples including 13 humans; since two cases of simultaneous occurrence of Encephalitozoon cuniculi and Enterocytozoon bieneusi were identified, 89 full-length ITS sequences were obtained, namely 78 Encephalitozoon cuniculi genotype I, five E. cuniculi genotype II, two E. hellem 1A and four Enterocytozoon bieneusi. No Encephalitozoon intestinalis-positive samples were identified. This is the first report of Encephalitozoon species and Enterocytozoon bieneusi genotypes in captive great apes kept under various conditions and the first record of natural infection with E. hellem in great apes. A comparison of zoos and sanctuaries showed a significantly higher prevalence of microsporidia in sanctuaries (P<0.001), raising a question about the factors affecting the occurrence of microsporidia in epidemiologically and sanitarily comparable types of facilities.     

Detection of plant pathogens using real‐time PCR: how reliable are late Ct values?

Effective detection of pathogens from complex substrates is a challenging task. Molecular approaches such as real‐time PCR can detect pathogens present even in low quantities. However, weak real‐time PCR signals, as represented by high cycle threshold (C_t) values, may be questionable. Therefore, setting a reliable C_t threshold to declare a positive reaction is important for specific detection. In this study, five methods were assessed for their performance in determining a C_t cut‐off value. These methods were based on the widely used probability of detection (POD) or receiver‐operating characteristic (ROC) approaches. Two important forest pathogens, Hymenoscyphus fraxineus and Fusarium circinatum, were used to set up three experimental frameworks that combined two types of substrates (seed lots and spore traps) and different PCR machines. The ROC‐based method emerged as the most complete and flexible method under various experimental conditions. It was demonstrated that the ROC method leads to a cut‐off value below which late C_t results can reliably be considered indicative of positive test results. This cut‐off value must be determined for each experimental approach used. The method based on the distribution of a previously determined set of C_t values corresponding to false‐positives appeared to be better adapted to detecting false‐negative results, and thus useful for testing potentially invasive pathogens.     

Can a chitin‐synthesis‐inhibiting turfgrass fungicide enhance black cutworm susceptibility to a baculovirus?

BACKGROUND: Developmental resistance, i.e. reduced virulence and speed of kill of late instars, is a limiting factor in the use of baculoviruses for caterpillar control. Agrotis ipsilon multicapsid nucleopolyhedrovirus (AgipMNPV) is highly infective to young black cutworms, Agrotis ipsilon, but too slow‐acting against late instars for effective curative control on golf courses or sports fields. Chitin‐synthesis‐inhibiting fungicides containing the active ingredient polyoxin‐d are used to control fungal diseases in turfgrass, and similar compounds have been shown in the laboratory to synergize baculoviruses by disrupting peritrophic membrane function. This study tested whether applying the virus together with such a fungicide can synergize AgipMNPV activity against A. ipsilon in turfgrass. RESULTS: The addition of a chitin synthesis inhibitor failed to increase AgipMNPV infectivity to A. ipsilon in the field. Rather, delayed and slightly reduced mortality from viral infection was seen when larvae fed on fungicide/virus‐treated grasses as opposed to virus‐only treatments. Choice tests revealed the fungicide residues to be a mild feeding deterrent. CONCLUSION: Because polyoxin‐d does not deactivate AgipMNPV, the two substances are compatible. However, combination applications of polyoxin‐d and Agip MNPV on turfgrass might interfere with larval ingestion of a lethal virus dose, resulting in prolonged larval feeding in the field. Copyright © 2011 Society of Chemical Industry     

Are honeybees suitable surrogates for use in pesticide risk assessment for non‐Apis bees?

Historically, bee regulatory risk assessment for pesticides has centred on the European honeybee (Apis mellifera), primarily due to its availability and adaptability to laboratory conditions. Recently, there have been efforts to develop a battery of laboratory toxicity tests for a range of non‐Apis bee species to directly assess the risk to them. However, it is not clear whether the substantial investment associated with the development and implementation of such routine screening will actually improve the level of protection of non‐Apis bees. We argue, using published acute toxicity data from a range of bee species and standard regulatory exposure scenarios, that current first‐tier honeybee acute risk assessment schemes utilised by regulatory authorities are protective of other bee species and further tests should be conducted only in cases of concern. We propose similar analysis of alternative exposure scenarios (chronic and developmental) once reliable data for non‐Apis bees are available to expand our approach to these scenarios. In addition, we propose that in silico (simulation) approaches can then be used to address population‐level effects in more field‐realistic scenarios. Such an approach could lead to a protective, but also workable, risk assessment for non‐Apis species while contributing to pollination security in agricultural landscapes around the globe. © 2019 Society of Chemical Industry     

Can the parasitic weeds Striga asiatica and Rhamphicarpa fistulosa co‐occur in rain‐fed rice?

Striga asiatica and Rhamphicarpa fistulosa are important parasitic weeds of rain‐fed rice, partly distributed in similar regions in sub‐Saharan Africa (SSA). It is not evident whether their ecologies are mutually exclusive or partially overlapping. In Kyela, a rice‐growing area in south Tanzania where both parasites are present, three transects of about 3 km each across the upland–lowland continuum were surveyed in June 2012 and 2013. A total of 36 fields were categorised according to their position on the upland–lowland continuum as High, Middle or Low and soil samples were taken. In each field, parasitic and non‐parasitic weed species were identified in three quadrats. Additionally, in two pot experiments with four different moisture levels ranging from wilting point to saturation, influence of soil moisture on emergence and growth of parasites was investigated. Striga asiatica was observed in higher lying drier fields, while R. fistulosa was observed in the lower lying wetter fields. Furthermore, non‐parasitic weed species that were exclusive to S. asiatica‐infested fields are adapted to open well‐drained soils, while species that were exclusive to R. fistulosa fields are typical for wet soils. The experiments confirmed that S. asiatica is favoured by free‐draining soils and R. fistulosa by waterlogged soils. These results imply that changes in climate, specifically moisture regimes, will be crucial for future prevalence of these parasitic weeds. The non‐overlapping ecological range between their habitats suggests that their distribution and associated problems might remain separate. Thus, management strategies can be focused independently on either species.     

Search for reservoirs of ‘<Emphasis Type="Italic">Candidatus</Emphasis> Liberibacter solanacearum’ and mollicutes in weeds associated with carrot and celery crops

Currently, the main arthropod vectored pathogens associated with carrot and celery crop diseases are ˋCandidatus Liberibacter solanacearum´, Spiroplasma citri and different phytoplasma species. Mitigation strategies require elucidating whether these pathogens survive in the weeds of these Apiaceae crops, which can act as reservoirs. Weed surveys were conducted in a vegetative cycle (April to October 2012) in the spontaneous vegetation that surrounded crops affected by ˋCa. L. solanacearum´, S. citri and/or phytoplasmas. Sixty-three species of 53 genera that belong to 23 botanical families were collected in the main carrot and celery Spanish production area. Species were identified, estimating coverage and abundance, and conserved in herbarium. Samples were analysed by nested-PCR with universal primers for phytoplasmas detection, and were sequenced for identification purposes; by conventional PCR for S. citri and real-time PCR for ˋCa. L. solanacearum´. The only detected pathogens were ˋCa. Phytoplasma trifolii´ (clover proliferation group 16Sr VI-A) in Amaranthus blitoides and Setaria adhaerens and ˋCa. P. solani´ (stolbur group 16Sr XII-A) in Convolvulus arvensis. These pathogens were also sporadically detected in celery or carrot crops. Unexpectedly, neither ˋCa. L. solanacearum´ nor S. citri was detected in the weed samples, despite the relatively high prevalence of these pathogens (less than 66 % and 25 %, respectively) in the surveyed plots. This suggests that weeds do not play an epidemiological role as reservoirs in the spread of such organisms in the studied region. The use of pathogen-free seed lots and the control of vectors are crucial for preventing the introduction and spread of these economical important pathogens to new areas.     

What is the evidence for sexual reproduction of Phytophthora infestans in Europe?

The biology of late blight of potato and tomato, caused by Phytophthora infestans, changed when sexual reproduction by the pathogen became possible in many parts of the world, including Europe. In northern Europe, especially Scandinavia, there is increasing evidence that the pathogen is reproducing sexually on a regular basis, although in other regions further south or to the west it appears to reproduce primarily in a clonal manner. The presence of both mating types, the production of viable oospores, and observations of fields with soilborne sources of inoculum are consistent with sexual reproduction. Studies with different marker systems have revealed a population structure without any dominating clonal lineages in Scandinavia, and that is most easily explained by sexual reproduction. Phytophthora infestans recovered from the soil can also be linked to parental genotypes using likelihood‐based methods when codominant markers are used. A synthesis of all the available data points to a second centre of sexual reproduction in northern Europe.     

Is acetyl/butyrylcholine specificity a marker for insecticide‐resistance mutations in insect acetylcholinesterase?

Substrate specificity has been widely studied in vertebrate cholinesterases and it has been shown that two phenylalanines in the acyl pocket of acetylcholinesterase govern the acceptance of the acetyl/butyryl moiety of the choline esters. As an insecticide‐resistance mutation has been evidenced in the acyl pocket of Drosophila melanogaster and Musca domestica acetylcholinesterase we investigated the possibility of linking changes in acetyl/butyrylthiocholine specificity with mutations in insect acetylcholinesterase. We thus analyzed the effect of 28 mutations in Drosophila enzyme on acetyl/butyrylthiocholine, N‐methyl/N‐propyl‐carbamates and ethyl/methyl‐paraoxon preference. It appeared that the highest changes on acetyl/butyrylthiocholine and N‐propyl/N‐methyl‐carbamates preference were due to mutations in the acyl pocket. Nevertheless, other insecticide‐resistance mutations, not located in the acyl pocket, also modified these substrate preferences. Moreover, the effect of mutations in the acyl pocket was hidden when some other insecticide‐resistance mutations were combined in the enzyme. Consequently, acetyl/butyrylthiocholine preference alteration cannot be used as a marker to localize a mutation in the insect AChE. © 2000 Society of Chemical Industry     

How can natural hybridisation between self‐compatible and self‐incompatible species be bidirectional?

Self‐compatible (SC) plants often deposit pollen on their own stigmas before flowers open. Thus, if we find natural hybrids between a SC species and a closely related self‐incompatible (SI) species, the pollen donor is usually expected to be the SC species. However, in previous studies of naturally occurring mixed populations of invasive Cakile maritima (SI) and Cakile edentula (SC) in Australia, hybridisation was found to have been bidirectional. Here, we explored the floral development of these species in order to test the hypothesis that there might be a short opportunity for pollinators to visit open SC flowers before the self‐pollen is released. Results indicated that both species showed reverse herkogamy during early development, though by the time pollen was ripe the four long anthers always overtopped the stigma; in C. maritima, most of the short anthers remained below the stigma. In both species, ripe, compatible pollen was able to germinate on the stigmatic surface at all stages of floral development. Anther dehiscence commenced earlier in C. edentula and well before flowers opened, in contrast to C. maritima, but the timing of pollen release varied between individual flowers, with a small proportion of uncontaminated stigmas after flowering; therefore, C. edentula can be either pollen recipient or pollen donor when interspecific outcrossing occurs. In summary, our results suggest that the variation between individual flowers of C. edentula contributed to the bidirectional hybridisation despite being a predominant selfer, providing new insights into plant colonisation.     

Regulated non‐quarantine pests: fact or fiction?

A new category of officially regulated pests has been introduced during the past decade. The aim of this new categorization is to protect plant health and, in particular, farmers’ and growers’ crops against the introduction of pests via propagation material. The phytosanitary term ‘regulated non‐quarantine pests’ (RNQPs) is relatively new. It was introduced in 1997 as part of the new revised text of the International Plant Protection Convention. These RNQPs differ from the common category of quarantine pests in that they can be widespread within the territory of concern. Unlike quarantine pests, a level of tolerance could be applied for RNQPs infesting certain plants for planting. Some certification systems for the production of propagation material may specify certain tolerance levels, however, these systems are usually not regulated by national plant protection organizations and the tolerance levels are usually not based on scientific evidence. To date, only a few countries have applied the concept of RNQPs: notably Uruguay and Brazil. To apply the concept and, in particular, to determine specific tolerance levels presents many challenges. The concept may be embraced in the coming years by the European Community as part of the revision of the EU Council Directive 2000/29/EC.     

Can poisons stimulate bees? Appreciating the potential of hormesis in bee–pesticide research

Hormesis, a biphasic dose response whereby exposure to low doses of a stressor can stimulate biological processes, has been reported in many organisms, including pest insects when they are exposed to low doses of a pesticide. However, awareness of the hormesis phenomenon seems to be limited among bee researchers, in spite of the increased emphasis of late on pollinator toxicology and risk assessment. In this commentary, we show that there are several examples in the literature of substances that are toxic to bees at high doses but stimulatory at low doses. Appreciation of the hormetic dose response by bee researchers will improve our fundamental understanding of how bees respond to low doses of chemical stressors, and may be useful in pollinator risk assessment. © 2015 Society of Chemical Industry