Search PubMed⌕ Search

Biomedical subjects

I D Robertson

Publications and source records attributed to I D Robertson.

At least 55 records · Page 3Linked to original sources
PubMed1996

Studies on pathogenesis, tissue infection and congenital transmission in cows experimentally infected with Sarcocystis cruzi by various routes.

A group of nine cows, naturally infected with Sarcocystis, were challenged with Sarcocystis cruzi: three intrarumenally with sporocysts, two intrarumenally with water (controls), two intravenously with merozoites grown in vitro and two intravenously with saline solution (controls). The animals intrarumenally challenged with sporocysts developed acute sarcocystiosis and produced stillborn calves, whereas those intravenously challenged with merozoites suffered from subclinical sarcocystiosis with premature births. No parasites were found in calves from cows challenged with sporocysts; however, a meront of Sarcocystis was found within a macrophage in the cerebrospinal fluid of a calf from a cow intravenously inoculated with merozoites of S. cruzi. This is the first time that merozoites of S. cruzi grown in vitro have been demonstrated to retain the ability to infect their natural intermediate host and complete their life cycle.

Animals↗
PubMed1996

Genetic characterization of Mycobacterium avium isolates recovered from humans and animals in Australia.

Genetic relationships amongst 115 mainly Australian isolates of Mycobacterium avium were assessed using multilocus enzyme electrophoresis (MEE). The isolates were divided into 58 electrophoretic types (ETs), with a mean genetic diversity of 0.29. Isolates from humans were closely related to but distinct from those cultured from birds, whilst some porcine isolates belonged to the same ETs as certain human isolates. Pulsed field gel electrophoresis (PFGE) was used to differentiate related isolates, and those from birds and some from other animals, including pigs, were distinguished from the human isolates. The results of MEE and PFGE suggested that certain strains of M. avium may be transmitted between birds and pigs, but there was no clear evidence of transmission to humans. The serovar of the M. avium isolates was not obviously related to their ET assignment or their PFGE type.

Animals↗
PubMed1996

Genomic analysis of Mycobacterium bovis and other members of the Mycobacterium tuberculosis complex by isoenzyme analysis and pulsed-field gel electrophoresis.

Initially, multilocus enzyme electrophoresis was used to examine genetic relationships among 63 isolates of Mycobacterium bovis and 13 other members of the M. tuberculosis complex. The isolates were divided into five electrophoretic types, with a mean genetic diversity of 0.1. The strains were genetically homogenous, indicating that members of the complex were closely related. This supported the suggestion that they should be considered as subspecies of a single species. Pulsed-field gel electrophoresis (PFGE) was then used to differentiate these isolates, as well as 59 additional isolates of M. bovis from different parts of the world. PFGE differentiated these strains into 63 patterns (53 patterns for M. bovis). Isolates of M. bovis from Western Australia (n = 46) were more homogenous than isolates from other regions. Eight strains were identified in that state, and one predominantly bovine strain was isolated from two human beings and a feral pig. Although M. bovis isolates from different parts of the world had distinct DNA patterns, some were very similar. PFGE is a highly discriminatory technique for epidemiological studies of bovine tuberculosis. For example, it allowed differentiation between isolates of M. bovis cultured from animals in separate outbreaks of tuberculosis, it suggested the transmission of infection between certain properties, and it demonstrated the existence of multiple infections with different strains at certain farms.

Animals↗
PubMed1995

A survey of urban pet ownership in Bali.

A personal interview survey was conducted to determine the type and characteristics of the animals kept by 200 households in a traditional Balinese community in Denpasar, Indonesia. Fifty-seven per cent of the households owned an animal. One or more birds were kept by 45.2 per cent of households, dogs were owned by 39 per cent, cats by 18.5 per cent and some other sort of animal was owned by 4.5 per cent of households. Chickens were the most commonly kept bird (29.5 per cent of households) followed by cuckoos (10.5 per cent) and doves (8.5 per cent). More cats were kept in households with cats (average of 1.5) than dogs in the households with dogs (1.32. More male dogs and cats (85 per cent and 73 per cent, respectively) were kept than females. Only 11 per cent of the female dogs were neutered compared with 44 per cent of males and no female cats were neutered compared with 9.5 per cent of males. This low level of neutering accounted for the finding that 69 and 78 per cent of the entire bitches and queens had had litters in the 12 months preceding the survey.

Animals↗
PubMed1994

Radical excision of sacrococcygeal tumours.

Large sacrococcygeal tumours are rare and remain a difficult management problem. Chordomas are one of the most common tumours in this region and may account for 30-40 per cent of postrectal tumours. Four patients aged between 22 and 66 years, three with chordomas and one with a schwannoma, are described. Each was managed by a combined general and neurosurgical approach. Major radical excision of the tumour involving high amputation of the sacrum and lower sacral nerve root division was performed. These large lesions can be radically excised with limited postoperative morbidity and excellent preservation of neurological function, including sphincter control, provided that one S2 nerve root is left intact.

Adult↗
PubMed1994

Evaluation of a serological test system for the diagnosis of Sarcocystis cruzi infection in cattle using S. cruzi merozoite antigen.

Fifty serum samples were examined by enzyme-linked immunosorbent assay (ELISA) for antibodies directed against crude antigens isolated from cystozoites and merozoites of Sarcocystis cruzi and Sarcocystis tenella/Sarcocystis arieticanis and merozoites of Toxoplasma gondii. Of these 50 samples, 25 were from cattle originating from an area where the prevalence of S. cruzi was found to be very low (9%) and in which no cystozoites were detected, and 25 were from cattle which were found by a digestion method to be heavily infected with S. cruzi. A very high correlation was observed between the parasitological data and the results obtained from the serological assays which used antigens from either cystozoites or merozoites of S. cruzi. The assay using the antigen derived from merozoites provided the best result for discriminating infected and non-infected animals. There was some cross-reactivity between the antigen derived from cystozoites of heterologous species of Sarcocystis and S. cruzi antibodies, and some cross-reactivity between antigen of T. gondii and antibodies to S. cruzi. The reproducibility of the assays was found to be high and similar results were observed when the sera were tested on two separate occasions. The unpurified S. cruzi merozoite antigen produced in vitro is relatively accurate in discriminating positive and negative animals and may be used for diagnosis in economically important hosts such as cattle and sheep.

Animals↗
PubMed1994

Clonal analysis and virulence of Australian isolates of Streptococcus suis type 2.

Multilocus enzyme electrophoresis was used to divide 124 Australian isolates of Streptococcus suis type 2 into 17 electrophoretic types (ETs). Isolates in ET 1 were the most frequent cause of disease amongst Western Australian pigs, but isolates of ET 8 were more commonly associated with disease in other Australian states. Multiple isolates from 10 of 19 farms all belonged to the same ET, whilst isolates from the other farms belonged to between 2 and 4 different ETs. Some isolates could be differentiated further by DNA restriction endonuclease analysis, whilst others with the same restriction pattern were located in different, but closely-related ETs. Fourteen isolates were tested for their virulence in mice. Most caused disease if given in high numbers, but isolates in ET 1 were virulent at lower dose rates. This virulent clone also was distinguished by the fact that 80% of isolates produced extracellular factor (EF).

Animals↗
PubMed1993

Hydatid disease in Western Australia: a novel approach to education and surveillance.

Hydatid disease (echinococcosis) remains a public health and economic problem of global proportion. Treatment usually requires major surgery and the prognosis for some forms of the disease is poor. The variable transmission patterns exhibited by the causative agents of this complex zoonosis, and inadequate support both internationally and nationally, have resulted in the establishment of control campaigns that are usually organized and funded at a local level. Here, Andrew Thompson, Ian Robertson, Robin Gasser and Clare Constantine describe a novel, targeted campaign of education and surveillance that has recently been initiated in Western Australia, where a totally artificial cycle of transmission for Fchinococcus granulosus has been established as a result of human activity.

Journal Article↗
PubMed1993

The carriage of Streptococcus suis type 2 by pigs in Papua New Guinea.

An indirect fluorescent antibody test was used to detect the presence of Streptococcus suis type 2 in nasal and pharyngeal swabs taken from pigs in Papua New Guinea. The rate of carriage for the two sites in domesticated indigenous village pigs was 0.5 and 2.5% respectively, compared to 39 and 43% for intensively reared pigs. These findings were supported by the results of a serological survey, using an enzyme linked immunosorbent assay, in which 87% of intensively reared pigs but only 8% of village pigs were seropositive to S. suis type 2. It is proposed that in intensive piggeries S. suis type 2 is continually cycled between pigs. In village pigs, the low population density and harsh environmental conditions prevents this cycle of infection.

Animals↗
PubMed1993

Genetic characterisation of isolates of Listeria monocytogenes from man, animals and food.

Multilocus enzyme electrophoresis was used to assess genetic relationships between 95 isolates of Listeria monocytogenes, most of which were isolated in Australia and New Zealand from man, animals and food. The isolates were separable into two major genetic divisions; the majority of those from human patients and animals were in division I, and the majority from those foods that were not specifically associated with human listeriosis were in division II. Isolates in division I were virulent, whereas many isolates from food were probably less virulent and did not pose a large threat to human health. However, isolates from certain foods, particularly paté, were indistinguishable from those causing disease in man, and the consumption of these products represented a clear risk factor for infection. Isolates from infected human patients in Australia and New Zealand belonged to the same clone of serotype 4b that has been responsible for major epidemics in the northern hemisphere. However, a separate clone of serotype 1/2b strains, present in both Australia and New Zealand, was responsible for two major outbreaks that occurred in Western Australia in 1978-80 and 1990-91.

Alleles↗
PubMed1993

Experiences with a vaccine being developed for the control of swine dysentery.

A prototype vaccine that is being developed for the control of swine dysentery (SD) was tested in two groups of experimental pigs. Vaccination induced high circulating antibody titres against the aetiological agent, Serpulina (Treponema) hyodysenteriae. Pigs in the first trial were vaccinated twice before being challenged orally with the bacteria. Five of 6 unvaccinated animals developed dysentery within a fortnight of challenge, but only 1 of 6 vaccinated pigs showed signs of disease at this time. Unexpectedly, 1 mo after challenge, the surviving unvaccinated pig and 2 remaining healthy vaccinated animals succumbed to the disease. The reason for the development of this late-onset form of dysentery was not clear. In the second trial, 8 pigs were vaccinated 3 times. Only 2 of these animals (25%) developed severe dysentery after being mixed with infected pigs, whereas 7 of 8 (88%) unvaccinated control pigs in the same pen became diseased. The late-onset form of dysentery was not observed. The prototype vaccine for SD provided a useful level of protection, and could be used in programs to control the disease in Australia.

Animals↗
PubMed1993

Population structure of Australian isolates of Streptococcus suis.

The genetic diversity of 109 isolates of Streptococcus suis, which were recovered mainly from Australian pigs, was examined by multilocus enzyme electrophoresis. The collection was genetically diverse. Sixty-five electrophoretic types (ETs) were recognized, with a mean genetic diversity per enzyme locus of 0.512, or 0.431 when the number of isolates in each ET was considered. Serotype diversity varied, being greatest for isolates of capsular serotype 15 (0.364), and then diminishing in the order of serotypes 9, 1, 4, 1/2, 2, 7, and 3 (0.120). On average, isolates from these eight serotypes represented 4.13 separate clonal groups per serotype. This diversity indicated that serotyping of S. suis for subspecific differentiation is not a reliable technique for identifying specific strains and is not a good predictor of the genetic background of a given isolate. No tendency for isolates recovered from healthy pigs to be genetically distinct from those from diseases animals was found, nor were there consistent differences between isolates recovered from animals with different disease syndromes (meningitis, pneumonia, and septicemia). Danish reference strains of serotypes 1, 2, and 7 each belonged to one of the same clonal groupings of these types found in Australia, but Danish strains of serotypes 3, 4, 6, and 8 and a strain of serotype 1 from the United Kingdom were each genetically distinct from the Australian isolates. Generally, isolates in the same ET belonged to the same serotype, but one ET contained isolates of types 6 and 6/16, and three were made up of isolates of types 2 and 1/2. One isolate of serotype 2, which was recovered from a human with meningitis, belonged to the same ET as two isolates of serotype 2 that were recovered from pigs. The human infection was therefore likely to have been zoonotic.

Animals↗
PubMed1992

The epidemiology of Sarcocystis spp. in cattle of Western Australia.

Oesophagus samples from 714 cattle from Western Australia were examined by artificial digestion to detect the presence of Sarcocystis spp. The overall prevalence of infection was 52%. The prevalence of infection increased with age and was highest in the entire males (92%). The prevalence was lower in cattle which originated from arid and semiarid regions (9 and 31% respectively) than those from tropical (87%) and temperate (60%) regions. Possible reasons for these differences are discussed and it is concluded that environmental and management factors as well as host age and sex influence the prevalence of infection with Sarcocystis spp. in cattle.

Abattoirs↗