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P J Wilkinson

Publications and source records attributed to P J Wilkinson.

At least 19 recordsLinked to original sources
PubMed1991

Cook-chill, cook-freeze, cook-hold, sous vide: risks for hospital patients?

Changes in eating habits and developments in food technology are occurring at the same time as an upward trend in foodborne infection in Britain. Vulnerable people such as the elderly and hospital patients are increasingly likely to consume food produced by new systems such as 'cook-chill' and 'cuisson sous vide'. The microbiological hazards of these systems are assessed as negligible, provided that production is controlled by appropriate methods such as the hazard analysis critical control point (HACCP) approach. The occurrence and control of bacterial contamination in a hospital cook-chill system is reviewed in this context.

Cooking↗
PubMed1990

Identification of a variable region of the African swine fever virus genome that has undergone separate DNA rearrangements leading to expansion of minisatellite-like sequences.

Nucleotide sequencing identified a tandemly repeated sequence array 22 x 10(3) base-pairs from the right-hand DNA terminus of the African swine fever virus (ASFV) genome. The sequence of the repeat array and sequences closely flanking it were compared in the genomes of four groups of ASFV isolates that had very different restriction enzyme site maps. Arrays present in one group of ASFV isolates from East Zambia/Malawi varied in length and contained between 8 and 38 copies of a 17-nucleotide repeat unit. Repeat arrays in a second group of ASFV isolates from Europe were less variable in length but consisted of different types of repeat unit that were divergent in sequence. A third genetically diverse ASFV isolate. LIV 13 from a South Zambia Game Park, contained repeat unit types that were similar to those of European viruses. MFUE6 isolate from an East Zambia Game Park contained a shorter version of the European repeat unit. An eight-base-pair core sequence was conserved between the East Zambia/Malawi and European and LIV 13 repeat units. These tandemly repeated sequence arrays share a number of properties with chromosomal minisatellite DNA. Similar tandem repeat arrays have not been described in poxviruses.

African Swine Fever↗
PubMed1990

Absence of Ornithodoros moubata, the vector of African swine fever virus, from the main pig producing area of Cameroon.

No evidence for the presence of soft ticks of the Ornithodoros moubata complex was found during a survey of African swine fever carried out between 1985 and 1988 in the West Province and southern parts of the North West and South West Provinces of Cameroon. The survey consisted of interviews of veterinary assistants and farmers, distribution of a questionnaire and tick searches both manually and with carbon dioxide traps. The absence of warthogs (Phacochoerus aethiopicus) from these areas was also recorded.

African Swine Fever↗
PubMed1990

Cryptosporidiosis--an educational experience.

Eleven children aged 7 to 8 years from one school class developed diarrhoea and vomiting after an educational visit to a dairy farm. Three required hospital admission and intravenous fluid replacement for dehydration. Cryptosporidium oocytes were found in the faeces of these three children and from one classmate when the remainder of the class was tested between 16 and 21 days after the visit. At the farm some children tasted pelleted cow feed, silage and dried milk powder. A case-control study showed a significant correlation between diarrhoea and the tasting of silage and pelleted feed. Guidance on the safe conduct of educational visits to farms is given.

Animal Feed↗
PubMed1990

Variable regions on the genome of Malawi isolates of African swine fever virus.

Restriction enzyme site mapping showed that most BamHI and all ClaI sites were conserved on the genomes of 17 African swine fever virus isolates from separate disease outbreaks that occurred between 1982 and 1989 in Malawi. However, frequent variation between virus genomes did occur due to addition or deletion of DNA sequences at various positions along the genome and 11 virus genotypes could thus be distinguished among the 17 isolates analysed. Length variations occurred at 10 different loci on the virus genome. These variable regions were located between the left DNA terminus and a position up to 48 kb from that terminus, in the centre of the genome 90 to 93 kb from the left DNA terminus and between the right DNA terminus and a position 22 kb from that terminus. Length variations in most of these regions were small (less than 1 kb) but variations of about 4 kb occurred in a region up to 20 kb from the left DNA terminus.

African Swine Fever↗
PubMed1989

Infection of pigs with the Cameroon isolate (Cam/82) of African swine fever virus.

African swine fever (ASF) was produced in eight pigs by exposure to donors infected with the Cameroon/82 isolate of African swine fever virus. The primary clinical sign was pyrexia of more than 40 degrees C first observed 10 to 13 days post-exposure (dpe) in all pigs; other clinical signs were rarely observed. The most frequent post-mortem lesion was haemorrhage in the visceral lymph nodes. Other lesions included excess fluid in the abdominal cavity and petechial haemorrhages in the kidneys. Viraemia was first observed 1 to 2 days before the onset of pyrexia and maximal titres of more than 10(7.5) HAD50 per ml occurred 11 to 14 dpe. Virus excretion by the pharyngeal route was observed at 2 to 4 days before the onset of pyrexia and continued throughout the course of infection. Susceptible pigs, mixed directly with infected ones, contracted infection within 2 h; transmission time increased to 2 to 6 h when recipient pigs were separated by wire mesh from the infected pigs. The comparatively low mortality, ill-defined clinical signs and clinical recovery of many of the infected pigs show that the Cam/82 ASF virus is of relatively low virulence and thereby resembles recent European, South American and Caribbean isolates.

African Swine Fever↗
PubMed1989

A study of African swine fever virus infected ticks (Ornithodoros moubata) collected from three villages in the ASF enzootic area of Malawi following an outbreak of the disease in domestic pigs.

A detailed study was made in 1983-5 in three villages in Mchinji district in the African swine fever (ASF) enzootic area of Malawi, following an outbreak of ASF which affected all three villages. Ticks of the Ornithodoros moubata complex were collected from both pig sties and houses shortly after the outbreak, and approximately 24% contained ASF virus. The proportion of ticks infected did not differ significantly in the three villages, or more surprisingly in different types of premises, and was equivalent in all stages of ticks. The proportion infected decreased with the passage of time, but infected ticks were still present in all three villages 8 months after the outbreak, some with high titres of virus. The proportion of seropositive pigs in the three villages approached 100% following the outbreak, with many apparently healthy pigs being seropositive. It is suggested that Malawian isolates of ASF virus may be less virulent in African than European breeds of domestic pig.

African Swine Fever Virus↗
PubMed1989

Spermatogenesis in heterozygotes for Robertsonian chromosomal rearrangements from natural populations of the common shrew, Sorex araneus.

Twenty-two adult male common shrews were collected from 5 sites in the vicinity of Oxford (UK) close to the zone of hybridization between two karyotypic races. The shrews were subdivided into 3 karyotypic categories: homozygotes, simple Robertsonian heterozygotes (which form one or more trivalents at prophase I of meiosis) and complex Robertsonian heterozygotes (which form a quadrivalent). The ratio of primary spermatocytes to round spermatids was determined from transverse sections of seminiferous tubules, to provide an indication of germ cell death. In no individual was there severe germ cells loss. Homozygotes had the highest mean spermatocyte: spermatid ratio and complex heterozygotes the lowest, but there was substantial individual variation and the differences were not significant. Complex heterozygotes also had a higher proportion of defective seminiferous tubules and lower testis weights than did other categories and it is reasonable to propose that, as a population, complex heterozygotes had reduced fitness relative to other categories on the basis of spermatogenic performance. However, there is no evidence from studies of spermatogenesis that simple Robertsonian heterozygotes are less fit than homozygotes.

Animals↗
PubMed1988

Microbiological evaluation of a hospital delivered meals service using precooked chilled foods.

A delivered meals service supplying centrally produced, precooked, chilled foods to 24 hospitals was introduced in Plymouth Health District between August 1985 and July 1986. Over 18 months, 3393 food items were examined microbiologically, using the criteria recommended by the Department of Health and Social Security (DHSS) (1980). No Salmonella spp., Staphylococcus aureus or Clostridium perfringens were detected. Seventy-five (8.6%) of 876 cooked vegetable items had total viable counts (TVC) greater than 1 x 10(5) cfu g-1 (the recommended limit) after aerobic incubation at 37 degrees C for 48 h, whereas only 2.6% (66) of 2517 foods other than vegetables had TVC above this limit. Reasons for high counts were investigated and mostly corrected so that, whereas 8.4% of samples had TVC above recommended limits in the first 4 months of the study, only 1.6% exceeded this limit in the last 3 months. The value of microbiological standards for cook-chill food and their use in hygiene control are assessed.

Cooking↗
PubMed1988

Food hygiene in hospitals.

Food hygiene in British hospitals is reviewed in the context of national trends in food poisoning and changes in food legislation. New methods of large scale catering such as the cook-chill system are considered, and the safe operation of such a system in a typical health district is described. The application of current guidelines for the microbiological quality of cook-chill food is evaluated. The need for careful observance of these principles, together with appropriate microbiological surveillance of the process and the product, is demonstrated.

Cross Infection↗
PubMed1988

Isolation of African swine fever virus from ticks of the Ornithodoros moubata complex (Ixodoidea: Argasidae) collected within the African swine fever enzootic area of Malawi.

Ticks of the Ornithodoros moubata complex were collected from domestic pig sties and dwelling houses, and from a warthog habitat, and tested for the presence of African swine fever (ASF) virus. Collections were made in 9 of the 24 districts of Malawi, these being primarily the districts in which O. moubata is most numerous. ASF virus was isolated from ticks collected in both domestic pig sties and houses in certain villages in Mchinji district where ASF outbreaks had recently occurred. Mchinji district is in the centre of a large ASF enzootic area which stretches into other districts of Malawi and also into Zambia and Mozambique. The high titre of virus in some of the ticks demonstrates that O. moubata can act as a virus reservoir and potential vector of disease in the field situation in Malawi.

African Swine Fever↗
PubMed1988

The distribution of African swine fever virus isolated from Ornithodoros moubata in Zambia.

African swine fever (ASF) has been reported in the Eastern Province of Zambia since 1912 and is now considered to be enzootic there. A survey of the distribution of ASF virus in Zambia was carried out by virus isolation from Ornithodoros moubata ticks collected from animal burrows in National Parks and Game Management Areas in northern, eastern, central and southern Zambia. ASF virus was isolated from ticks in all areas examined. The prevalence of infection in O. moubata was between 0.4% in South Luangwa National Park and 5.1% in Livingstone Game Park and mean infectious virus titres ranged from 10(3.4) HAD50/tick in Kakumbe Game Management Area to 10(5.9) HAD50/tick in Chunga and Nalusanga Game Management Areas. The prevalence of infection in adult ticks was between 4.7% and 5.3% in all areas examined except Sumbu National Park and Livingstone Game Park, where the prevalence was 15.1% and 13.2% respectively in adult ticks. The ratio of infected females to males for all the infected adult ticks in all areas of Zambia was 3.2:1.

African Swine Fever↗
PubMed1988

Genetic diversity of African swine fever virus isolates from soft ticks (Ornithodoros moubata) inhabiting warthog burrows in Zambia.

The genomes of African swine fever virus isolates collected from soft ticks (Ornithodoros moubata) inhabiting warthog burrows in four areas of Zambia were compared by restriction enzyme site mapping. Isolates from different areas showed considerable diversity. The regions of genomes that differed between isolates were distributed throughout the virus genome, although some more conserved regions were identified, such as the right-hand third of the genome. The genomes of seven isolates from neighbouring warthog burrows within Livingstone Game Park in southern Zambia were more similar to each other than those from different areas. However, a number of differences were observed even between the genomes of isolates from the same warthog burrow. The variation between these latter isolates probably resulted from point mutations located at various positions along the genome, in addition to small additions or deletions at both terminal regions. Restriction enzyme site mapping indicated that one isolate may have originated by earlier recombination between two distinguishable viruses.

African Swine Fever Virus↗
PubMed1987

Mechanical transmission of capripox virus and African swine fever virus by Stomoxys calcitrans.

Stomoxys calcitrans can act as an efficient mechanical vector of capripox virus and African swine fever virus. Capripox virus was transmitted to a susceptible goat by flies infected 24 hours previously and the virus survived in some flies for at least four days. African swine fever virus was transmitted to susceptible pigs by flies infected one hour and 24 hours previously and the virus survived in these flies for at least two days without apparent loss of titre.

African Swine Fever↗
PubMed1987

Arachidonic acid metabolites in the pathophysiology of thrombocytopenia and haemorrhage in acute African swine fever.

Changes in the production of proaggregatory (thromboxane A2 and prostaglandin E2) and antiaggregatory (prostacyclin) prostaglandins by blood platelets, macrophages and endothelial cells during acute African swine fever caused by both a highly virulent virus and a less virulent virus were studied. No impairment in thromboxane A2 release by either platelets or macrophages could be detected but prostacyclin production by the endothelium was impaired. There was also a significant increase in prostaglandin E2 release by macrophages at the time when thrombocytopenia was most marked. However, the early event that causes primary aggregation remains obscure.

African Swine Fever↗
PubMed1986

The XYY condition in a wild mammal: an XY/XYY mosaic common shrew (Sorex araneus).

XY/XYY sex-chromosome mosaicism was demonstrated in both bone marrow and germ cells of a wild adult common shrew. Secondary sexual characteristics were those of a normal male, but the testes were small, and the sperm count was only about 3% of normal. Most of the seminiferous tubule cross-sections examined revealed serious spermatogenic impairment and a reduced diameter. A range of sex-chromosome pairing configurations was observed in XYY primary spermatocytes, including configurations involving the X and both Y chromosomes in a linear or radial array. The presence of metaphase II (MII) spreads with an XY sex-chromosome complement indicated that XYY primary spermatocytes could contribute products to MII. Following Burgoyne (1979) and Burgoyne and Biddle (1980), a number of models of spermatocyte loss were tested. The data indicated that there was an association between the sex-chromosome complement of primary spermatocytes and their contribution to MII. The best fit to the observed MII frequency data was provided by a model which assumed that all XYY primary spermatocytes with a univalent Y chromosome and a high proportion of XYY primary spermatocytes with an unpaired X chromosome failed to contribute products to MII.

Animals↗