Woody encroachment over 70 years in South African savannahs: overgrazing, global change or extinction aftershock?

Woody encroachment in 'open' biomes like grasslands and savannahs is occurring globally. Both local and global drivers, including elevated CO2, have been implicated in these increases. The relative importance of different processes is unresolved as there are few multi-site, multi-land-use evaluations of woody plant encroachment. We measured 70 years of woody cover changes over a 1020 km(2) area covering four land uses (commercial ranching, conservation with elephants, conservation without elephants and communal rangelands) across a rainfall gradient in South African savannahs. Different directions of woody cover change would be expected for each different land use, unless a global factor is causing the increases. Woody cover change was measured between 1940 and 2010 using the aerial photo record. Detection of woody cover from each aerial photograph was automated using eCognitions' Object-based image analysis (OBIA). Woody cover doubled in all land uses across the rainfall gradient, except in conservation areas with elephants in low-rainfall savannahs. Woody cover in 2010 in low-rainfall savannahs frequently exceeded the maximum woody cover threshold predicted for African savannahs. The results indicate that a global factor, of which elevated CO2 is the likely candidate, may be driving encroachment. Elephants in low-rainfall savannahs prevent encroachment and localized megafaunal extinction is a probable additional cause of encroachment.This article is part of the themed issue 'Tropical grassy biomes: linking ecology, human use and conservation'.

Gut and intestinal passage time in the Rainbow Skink (Trachylepis margaritifer): implications for stress measures using faecal analysis.

Stress levels in organisms provide a rapid measure for assessing population health. Handling and capture stress, however, cause error in blood measures, so this method is rapidly being replaced by assessing levels of stress metabolites in faeces. This eliminates the source of error because there is a lag period between stress perception and the resultant stress metabolite accumulation within faeces. This lag period is correlated with specific intestinal passage time, a measure that can vary greatly between taxa, particularly amongst ectotherms. Due to two deleterious consequences associated with extended exposure of the metabolites to the intestinal environment, species that exhibit long and variable intestinal passage times are not good candidates for metabolite studies. We measured gut and intestinal passage times in Trachylepis margaritifer to ascertain whether it would be an appropriate candidate for stress metabolite studies. We first tested if barium sulphate in the meal had an effect on gut passage time at three ambient temperatures (25, 27 and 32 °C). Barium sulphate had no effect; however, temperature had a significant effect with an unexpected pattern: gut passage time was fastest at 32 °C but was slower at 27 °C than at 25 °C. We then used X-ray technology and barium sulphate-loaded meals to measure gut and intestinal passage times at 25 and 27 °C. This allowed us to observe which parts of the digestive process were responsible for increased passage times at 27 °C: the faster passage time at 25 °C was due to faster intestinal passage time; there was no difference in gastric emptying time. We assess the species to be a suitable candidate for studies using faeces to measure stress. It is imperative however, that the effect of temperature on passage rates is known and taken into account in such studies.

Tissue tropism of African horsesickness virus in the chicken embryo demonstrated with the avidin-biotin complex immunoperoxidase method.

In horses, African horsesickness virus (AHSV) exhibits marked tropism for certain microvascular endothelia and components of the mononuclear phagocyte system. In this study, the tropism of a field isolate of AHSV serotype 5 was studied in 24 chicken embryos. Histopathology on embryonic tissues harvested with 12 hour intervals revealed progressive changes associated with endothelial damage. Immunolabeling demonstrated viral antigens in the microvascular endothelium of the spleen, lungs, and the mesenchymal connective tissue at the base of the neck, from 24 hours post inoculation. Subsequently, specific immunolabeling increased steadily in endothelia of these and other tissues such as skeletal and cardiac muscle, gastrointestinal smooth muscle, mesonephric glomeruli, liver, subcutis and feathers. Positive immunolabeling was also occasionally observed in circulating mononuclear cells and in Kupffer cells in the liver. It was concluded, that this isolate of AHSV displayed similar tissue tropism in the chicken embryo as in the horse.

Influence of catheter design on lumen wall temperature distribution in intracoronary thermography.

Intracoronary thermography is a currently used vulnerable plaque detection method. We studied how catheter design and catheter location influence the temperature readings, and thus its capacity to detect vulnerable plaques. Finite element calculations were performed on geometries representing the coronary artery, the vulnerable plaque and the catheter. Catheter material, diameter and location with respect to the plaque were varied. Both flow and no-flow situations were studied. Maximal lumen wall temperature difference without a catheter (DeltaT=0.12 degrees C, flow=75 cm(3) min(-1)) was considered the reference. Presence of a 1.0mm nitinol catheter right under the plaque increased DeltaT to 0.14 degrees C, whereas a 1.0 mm polyurethane catheter increased DeltaT to 0.51 degrees C. The location at which a thermosensitive element should be placed for most optimal temperature readings during a pullback was shown to lie at the catheter edge for the nitinol catheter and at 1.1mm from the catheter edge for the polyurethane catheter. Temperature readings decreased to background temperature when the catheter was in close proximity but not overlapping the plaque. DeltaT decreased approximately by 70% when a gap of 0.2 mm existed between the catheter and the lumen wall. Occlusion of blood flow increased DeltaT values in all cases, but most pronounced for nitinol catheters. A polyurethane catheter increased the temperature readings, since its heat conductivity is lower than that of blood, which makes it a very good choice for heat source detection. Catheter design can contribute to enhanced temperature readings and thus can enable more optimal vulnerable plaque detection.

Aspects of the working life of women in the nursing profession in South Africa: survey results.

This article reports on a survey done among nurses registered with the South African Nursing Council. The survey was carried out in the last quarter of 2003. The purpose of the survey was to investigate aspects of the working life of women in the nursing profession in South Africa and to make recommendations on how their working environment could be improved. The important findings were that pay-related issues dominate as the main problem at work. Improving pay scales and being paid according to extra experience, responsibilities and qualifications could improve the nurses' working environment. Furthermore, training opportunities, medical insurance and equal opportunities should be addressed as a matter of urgency. In general, respondents had a positive attitude towards their job, which leaves the impression that nurses still regard their jobs as something they do for the sake of a service to the community and not only for the money they earn.

Teratogenicity of a mutagenised Rift Valley fever virus (MVP 12) in sheep.

A 5-fluorouracil mutagenised Rift Valley fever virus strain, which was shown to be attenuated and immunogenic in cattle and sheep, was evaluated for its ability to cause teratogenic effects in pregnant sheep. A group of 50 sheep at various stages of pregnancy was inoculated with the virus and the pregnancies followed to term. There were two abortions and 14% of the lambs produced by vaccinated ewes showed teratogenic effects, the most prevalent being spinal hypoplasia, hydranencephaly, brachygnathia inferior and arthrygryposis. The foetal malformations of the central nervous and musculo-skeletal systems were mostly consistent with those observed in sheep vaccinated with the attenuated Smithburn RVF strain. The teratogenic effects of MVP12 were not seen in previous experiments by other authors as immunisation of sheep took place in the second to third trimester of pregnancy, when the foetal brain tissue has completed most of its cell division.

Assessment of cell culture and polymerase chain reaction procedures for the detection of polioviruses in wastewater.

WHO considers that environmental surveillance for wild-type polioviruses is potentially important for surveillance for acute flaccid paralysis as a means of confirming eradication of poliomyelitis. The present study investigated methods for detecting polioviruses in a variety of water environments in South Africa. Most polioviruses were isolated on L20B mouse cells, which, however, were not selective: 16 reoviruses and 8 enteroviruses, apparently animal strains, were also isolated on these cells. Vaccine strains of polioviruses were isolated from surface waters during and shortly after two rounds of mass vaccination of children in an informal settlement where there was no sewerage. The results demonstrated the feasibility of poliovirus surveillance in such settlements. It was also evident that neither poliovirus vaccine strains nor other viruses were likely to interfere significantly with the detection of wild-type polioviruses. Optimal isolation of polioviruses was accomplished by parallel inoculation of L20B mouse cells and at least the PLC/PRF/5 human liver and buffalo green monkey (BGM) kidney cell lines. Analysis of cell cultures using the polymerase chain reaction revealed that 319 test samples contained at least 263 human enteroviruses that failed to produce a cytopathogenic effect. This type of analysis thus significantly increased the sensitivity of enterovirus detection.

Nursing professionals' views on the workplace. Survey results.

This article reports on a survey done among registered, enrolled and auxiliary nurses registered with the South African Nursing Council. The survey was carried out in the period from the end of December 1997 to the beginning of 1998. The purpose of the survey was to obtain the views of female nurses on various aspects of the workplace. The important findings were the fact that nurses liked working as part of a team and that this contributed the most to their job satisfaction. The item that contributed least to job satisfaction was pay. The most important problems were that they felt that they were not paid enough and that they need better benefits. The majority of nurses were however positive about their jobs and the items the highest on the list of career expectations were job satisfaction, followed by a need for recognition.

Recombinant baculovirus-synthesized African horsesickness virus (AHSV) outer-capsid protein VP2 provides protection against virulent AHSV challenge.

African horsesickness virus serotype 4 (AHSV-4) outer-capsid proteins VP2 or VP2 and VP5, prepared from single or dual recombinant baculovirus expression vectors grown in Sf9 insect cells, were administered in different amounts to horses and the neutralizing antibody responses were measured. Control and vaccinated horses were challenged with virulent AHSV-4 6 months later and monitored post challenge. The results indicated that two inoculations of extracts containing VP2 and VP5, or VP2 alone, in doses of 5 micrograms VP2 or more per horse, were sufficient to elicit protection against African horsesickness (AHS) disease. The recombinant VP2 protein is a potential candidate vaccine for AHS in horses.

Long-lasting protection of sheep against bluetongue challenge after vaccination with virus-like particles: evidence for homologous and partial heterologous protection.

Insect cells co-infected with appropriate recombinant baculoviruses synthesize double-shelled, virus-like particles (VLPs) with bluetongue virus (BTV) VP2 proteins representing serotype 1 (BTV-1), 2 (BTV-2), 10 (BTV-10), 13 (BTV-13) or 17 (BTV-17) as previously reported for BTV-10 (French, T.J., Marshall, J.J.A. and Roy, P. J. Virol. 1990, 64, 5696-5700). The derived particles were purified and used to vaccine sheep, either as single VLP types (BTV-10, BTV-17) or as a combination of all five serotypes. Control sheep received saline. The virus-neutralizing antibody responses were measured. Depending on the experiment, the sheep were challenged with homologous (BTV-10, -13, -17) or selected heterologous (BTV-4, -11, -16) viruses either after 4 months or 14 months, and the disease, viraemias and clinical reactions monitored. The results indicated that two doses of 10 micrograms of VLPs elicited a long-lasting immune response which protected the sheep against challenge with the homologous virulent virus. In certain cases, partial protection was afforded against challenge by heterologous BTV serotypes.

Antigenic and molecular characterization of host cell-mediated variants of equine H3N8 influenza viruses.

Antigenic differences between three of six equine influenza virus (H3N8) MDCK cell- and egg-derived pairs have been demonstrated using monoclonal and polyclonal antibodies. Sequencing of the haemagglutinin (HA) genes revealed amino acid changes in four of the six virus pairs. These data contrast with those for human isolates of influenza virus in that it was predominantly tissue culture-isolated equine virus and not egg-derived virus which displayed heterogeneity. Some of the molecular changes involved are located within the vicinity of the cell receptor-binding site (positions 156, 158 and 222) whereas others are in the vicinity of the HA1-HA2 cleavage site (positions 18 and 32 of HA1 and position 12 of HA2). Our results indicate that the host cell can play a part in selecting antigenic variants of equine influenza virus and suggest that the egg, and not cell culture as is the case for human isolates, is the preferred host for vaccine and antigenic studies.

Isolation of bluetongue virus serotype 21 from Culicoides spp. in Indonesia.

The isolation of a bluetongue (BLU) virus from Culicoides spp. in Indonesia is reported. BLU serotype 21 was isolated from a mixed pool of C. fulvus and C. orientalis of the Avaritia subgenus.

Genomic variability among globally distributed isolates of equine arteritis virus.

Equine arteritis virus (EAV), a non-arthropod borne togavirus, has been shown to have a global distribution. To date, no major antigenic variation has been demonstrated between EAV isolates from different geographic origins. In this study, the genomic RNA of EAV isolates obtained from horses of different breeds in various countries around the world was oligonucleotide fingerprinted. Comparisons of these fingerprints were used to determine the extent of genomic variation among such isolates. Comparisons among isolates from North American horses revealed, for the most part, oligonucleotide homologies of less than 60%. Only 29 of the 98 comparisons revealed greater than 60% oligonucleotide homology. Nonetheless, several comparisons indicated a close epidemiologic relationship between isolates from horses of different breeds located in different states. Though all European isolates were of Standardbred origin and were from horses located in northern European countries, the majority had oligonucleotide homologies of less than 60%. Where oligonucleotide homology was apparent, it was, with one exception, greater than 70%. The two isolates from New Zealand had 93.2% oligonucleotide homology. This is indicative of an extremely close epidemiologic relationship. Comparisons between EAV isolates from around the world revealed oligonucleotide homologies between viruses from North America, Europe and New Zealand. In several instances, this homology was greater than 70% and in one case greater than 80%. No oligonucleotide homology was evident in comparisons involving the virus from South Africa. The high level of genomic conservation between certain EAV isolates of disparate geographic origins may reflect dissemination of the virus associated with the international movement of horses. The extent of genomic variation demonstrated between most of the EAV isolates used in this study confirms the need for further investigation of genomic heterogeneity among strains of this virus before techniques that rely upon nucleic acid hybridization can be effectively applied as diagnostic procedures.

Encephalitis and chorioretinitis associated with neurotropic African horsesickness virus infection in laboratory workers. Part I. Clinical and neurological observations.

Four laboratory workers from the same vaccine-packing facility developed at different times over an 8-year period an illness characterised by encephalitis (in 3 workers) and uveochorioretinitis (in 4). Low complement fixation titres were detected in all 4 patients to African horsesickness (AHS) virus and enzyme immunoassay and plaque reduction neutralising tests were positive, the latter against both serotypes 1 and 6. Five of 15 laboratory workers from the same facility who were healthy on clinical and ophthalmological examination showed positive plaque reduction neutralising tests but none to both serotypes 1 and 6. It is postulated that the encephalitis with the predominant temporal lobe involvement was caused by an airborne transnasal route of infection of the neurotropic AHS virus released in dried powder form, secondary to the accidental breaking of vaccine bottles. This is possibly the first report of subclinical and probable clinical neurotropic AHS infection in man.

Encephalitis and chorioretinitis associated with neurotropic African horsesickness virus infection in laboratory workers. Part II. Ophthalmological findings.

Four laboratory workers developed uveitis-chorioretinitis, associated with encephalitis in 3 cases. The retinitis was characterised by haemorrhages and areas of retinal oedema, most marked over the posterior polar regions, and was associated with exudative retinal detachments. The lesions progressed over weeks and showed a severe retinal arterial vasculopathy with arteriolar narrowing, ghost vessel formation and the development of optic atrophy. The picture in 2 of the patients resembled that of the acute retinal necrosis syndrome (ARN). Antibodies to African horsesickness (AHS) virus were detected. The serology for AHS virus was positive in all 4 patients as well as in 5 of 15 laboratory workers from the same facility who were clinically and ophthalmologically normal. This is to our knowledge the first description of subclinical and probable clinical neurotropic AHS virus infection in man. AHS is a hitherto-unrecognised possible cause of viral retinitis and the ARN syndrome.

Encephalitis and chorioretinitis associated with neurotropic African horsesickness virus infection in laboratory workers. Part III. Virological and serological investigations.

Four cases of encephalitis with chorioretinitis occurred in the vaccine-packing section of a veterinary research institute: 1 in 1982, 1 in 1985 and 2 in 1989. No viruses were isolated from patients and serological tests failed to reveal significant antibodies to a range of viruses incorporated in veterinary vaccines or to other likely pathogens, except for low titres of complement-fixing antibody to African horsesickness (AHS) virus in all 4 patients. In confirmatory tests, high enzyme immunoassay titres of antibody to AHS virus occurred in the 4 patients and lower titres in 5/58 other workers at the institute. The 4 patients had significant plaque reduction neutralisation antibody titres to some of the strains of virus incorporated in AHS vaccine, particularly to serotypes 1 and 6, which had undergone neuro-adaptation through serial intracerebral passage in mice and which were known to be encephalitogenic following intranasal instillation in horses, guinea pigs and dogs. It is believed that the patients may have acquired aerosol infection with AHS virus as a result of accidental breakage of freeze-dried vaccine bottles.

Encephalitis and chorioretinitis associated with neurotropic African horsesickness virus infection in laboratory workers. Part IV. Experimental infection of the vervet monkey (Cercopithecus pygerythrus).

Neurotropic vaccine strains of African horsesickness (AHS) virus types 1 and 6 were implicated as the possible aetiological agents in 4 cases of encephalitis and uveochorioretinitis in laboratory workers accidentally exposed to the freeze-dried vaccine preparations of the virus. To date, AHS virus has not been known to infect man. To ascertain whether or not primates were susceptible to infection with AHS virus, vervet monkeys (Cercopithecus pygerythrus) were inoculated, either transnasally or intraconjunctivally, with vaccine strains of AHS virus types 1 and 6. The course of infection was monitored using parameters such as behavioural changes, febrile reaction, cerebrospinal fluid pleocytosis, serology, magnetic resonance imaging and autopsy. Encephalitis, manifested by varying degrees of fever, behavioural changes and pleocytosis, but no chorioretinitis was detected in all 6 transnasally infected monkeys. This was confirmed by autopsy, where a meningo-encephalitis affecting the medial temporal lobe but no lesions in the eyes was demonstrated. Neither virus appeared to infect the animals after intraconjunctival inoculation. These findings support the theory that the patients were infected by the inhalation of freeze-dried vaccine preparations. The pathogenesis of the eye lesions, however, remains uncertain.