Hymenoscyphus pseudoalbidus and Hymenoscyphus albidus: viridiol concentration and virulence do not correlate

Hymenoscyphus pseudoalbidus is the causal agent of ash dieback, a disease that is presently endangering Fraxinus spp. throughout most of Europe. The phytotoxin, viridiol, was previously isolated from culture extracts of H. pseudoalbidus and found to be toxic to leaves of F. excelsior. Thus, we were interested in learning to what extent viridiol is responsible for pathogenicity of H. pseudoalbidus and investigated this using twelve isolates of H. pseudoalbidus. We also included five isolates of the closely related avirulent species, Hymenoscyphus albidus, in our studies. Some, but not all, isolates of H. pseudoalbidus and H. albidus produced measurable quantities of viridiol in culture. Three tests were used to determine to what extent viridiol concentration correlates with virulence: culture extracts were tested for activity in leaf segment tests and for inhibition of germination of seedlings of Fraxinus excelsior; virulence of the isolates was tested following infection of axenically cultured ash seedlings. Activity of the culture extracts varied, as did virulence of the isolates following inoculation into seedlings. No correlations were found between viridiol concentration and activities of culture extracts in leaf segment tests or in the germination test, nor between viridiol concentration and disease symptoms when inoculated into seedlings. However, activities of culture extracts in leaf segment and in the germination test correlated, as did the results of each of these tests with virulence in the infection experiment. Apparently, as yet unidentified factors other than the concentration of viridiol play important roles in the virulence of H. pseudoalbidus.     

Mediorhynchus gallinarum (Acanthocephala: Gigantorhynchidae) in Helmeted guineafowls, Numida meleagris, in the Kruger National Park, South Africa

Mediorhynchus gallinarum was recovered from the small intestines of 36 of 50 Helmeted guineafowls sampled from August 1988 to May 1989. The intensity of infection ranged from 1-141 worms per host, with a mean intensity of 23.2 (+/- 34) and a median intensity of 5. The Wilcoxon-Mann-Whitney test revealed no significant differences between the mean worm burdens of male and female birds at the 5% level (P > 0.05). Slightly more female than male acanthocephalans were collected. The majority (63.4%) of females had eggs with fully-developed embryos, 9% had immature eggs, 21.2% had no eggs and the egg status of 6.4% could not be determined. No seasonal pattern of intensity of infection emerged from the data, but worm burdens were markedly higher after good rains in February 1989. South Africa constitutes a new geographic record for M. gallinarum.     

A Chronic Plant Test for the Assessment of Contaminated Soils. Part 1: Method development (9 pp)

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PREAMBLE According to the German Federal Soil Protection Act (BBodSchG 1998), the habitat function of soils must be protected. Despite the fact that in the Federal Soil Protection Ordinance (BBodSchV 1999) it has not been established how this goal can be reached reliably, it is clear that such a biological function can only adequately be assessed using biological test methods. This is especially true when a soil is contaminated by a mixture of often unknown chemicals. In such a case the use of chemical analysis aiming at a small range of known substances is not sufficient and must therefore be supplemented by biological methods. For this reason, several standardised test methods are available (e.g. using earthworms, collembolans or plants; Römbke and Knacker 2003; ISO 2003). Since acute tests are usually not sensitive enough for the assessment of potentially contaminated soils (e.g. Hund-Rinke et al. 2002), chronic tests like the earthworm reproduction tests (ISO 1998) are recommended for this purpose.

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A chronic plant test for the determination of phytotoxicity was missing until quite recently. The term phytotoxicity is understood here as the capacity of a compound or a contaminated soil to cause temporary or long-lasting damage to plants (EPPO 1997). Therefore, the German Ministry for Education and Research sponsored a project (1997 – 1999) in which – based on existing standardised methods – such a chronic plant laboratory test was developed and partly validated (Kalsch and Römbke 2000). The new test can be used for the evaluation of single chemicals (see Part 1 of this mini-series) as well as for the assessment of contaminated or remediated soils (see Part 2 of this mini-series).

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ABSTRACT Background and Scope. As part of the efforts to improve the biological testing of contaminated soils, the German government sponsored the standardisation of a chronic plant bioassay. This new test is based on experiences with various acute plant tests (e.g. published by OECD or ISO) and existing North American Plant-Life-Cycle Bioassays. In this contribution the characteristic properties of the test are described.

Methods

The test can be performed either with Brassica rapa (turnip) or Avena sativa (oat). Its duration is 35 to 64 days with OECD artificial soil and a German standard field soil acting as controls. Water and nutrients are provided by an automatic wick irrigation system. Besides measuring biomass and shoot length, the number of pods, seeds and flowers are applied as chronic measurement endpoints. During the development of the test, TNT (2,4,6-trinitrotoluene) and Pyrene were used as model test substances.

Results

Pyrene did not affect B. rapa (turnip) in concentrations of up to 10.000 mg/kg soil (due to the often low sensitivity of A. sativa (oat) no further test with this substance was performed). Depending on the endpoint the results varied in the tests with TNT. With few exceptions, the NOEC (No Observed Effect Concentration) values were determined as 55.5 mg TNT/kg soil for B. rapa (turnip) and as 75 (unfertilised) and 150 (fertilised) mg TNT/kg soil for A. sativa (oat). The EC50-values varied between 96.3 and 207.2 mg TNT/kg soil for B. rapa (turnip) and 183.1 – 505.6 mg TNT/kg soil for A. sativa (oat), depending on the endpoint.

Outlook

The results of this work have been used to prepare a draft test guideline, which has recently been standardised by the International Organisation for Standardisation (ISO). Practical experiences with this test system are described in Part II of this mini series.     

Gastric nematodes of nile crocodiles, Crocodylus niloticus Laurenti, 1768, in the Okavango River, Botswana

The ascaridoid nematodes Dujardinascaris madagascariensis Chabaud & Caballero, 1966, Dujardinascaris dujardini (Travassos, 1920), Gedoelstascaris vandenbrandeni (Baylis, 1929) Sprent, 1978 and Multicaecum agile (Wedl, 1861) Baylis, 1923 were recovered from the stomach contents of Crocodylus niloticus Laurenti, 1768 from the Okavango River, Botswana, together with Eustrongylides sp., a dioctophymatoid nematode usually parasitizing piscivorous birds. Dujardinascaris madagascariensis was present in most of the infected hosts, while the remaining species were mostly represented in single collections in one to three hosts. All four ascaridoid nematodes represent new geographic records.     

First record of Cylicospirura (Cylicospirura) felineus (Chandler, 1925) Sandground, 1933 (Nematoda: Spirocercidae) from a domestic cat in South Africa

Cylicospirura (Cylicospirura) felineus (Chandler, 1925) Sandground, 1933 is reported from a cat in South Africa for the first time. The nematode was present in a gastric parasitic nodule in a male domestic cat, and three males were recovered as well as the anterior parts of three and the posterior parts of two gravid females. The heads of two specimens of undetermined sex were also found. Part of the removed parasitic nodule was processed for histopathological examination. The parasitic nodule was located in the submucosa and slightly expanded into the muscular layer. In its centre were small necrotic areas containing debris of inflammatory cells, adult nematodes and numerous bacterial colonies. Neutrophils, eosinophils, plasma cells and lymphocytes, as well as fibroblasts, were the predominant cell types. The serosal surface of the stomach remained unaffected. Some comparative morphological as well as ecological data concerning Cylicospirura (Cylicospirura) Vevers, 1922 in other feline hosts, mainly from Australia, India and North America, are included.     

Eustrongylides sp. (Nematoda: Dioctophymatoidea) from the stomach of a Nile crocodile, Crocodylus niloticus Laurenti, 1768, in Botswana

During a study conducted between 2003 and 2005 on the diet of Nile crocodiles in Botswana, two young adult nematodes, one male and one female, belonging to the genus Eustrongylides J?gerski?ld, 1909 were recovered from the stomach contents of one of these animals. The caudal bursa of the male is present and the ejaculatory duct could be identified, but the spicule could not be seen. The vulva of the female has opened and the anus is situated on a terminal protruberance. Measurements and drawings of these specimens are provided, together with some data on the occurrence and life-cycles of members of the genus Eustrongylides in crocodilians world-wide and in African hosts in particular. Piscivorous birds are the usual final hosts of these nematodes. It is probable that the specimens described herein had developed in a paratenic fish host, and that the latter had been eaten by the crocodile.     

COMPUTED TOMOGRAPHY OF CHOLESTERINIC GRANLOMAS IN THE CHOROID PLEXUS OF HORSES

Cholesterinic granulomas are tumor-like masses in the choroid plexuses of horses. This report describes the computed tomographic findings in four horses with cholesterinic granulomas, including the clinical and the pathologic features. All four horses had bilateral cholesterinic granulomas in the lateral ventricles. Computed tomographic images clearly delineated the masses, the opacity of the granulomas, and the enhancement pattern after intravenous bolus injection of contrast medium; these factors varied considerably. Additional CT findings were symmetric or asymmetric widening of the lateral ventricles.