ORCID Profile
0000-0002-3608-0175
Current Organisations
The University of Edinburgh
,
University of Glasgow
,
University of Salford
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Publisher: Cambridge University Press (CUP)
Date: 03-2005
DOI: 10.1017/S0031182004006614
Abstract: Recent research suggests that vertical transmission may play an important role in sustaining Toxoplasma gondii infection in some species. We report here that congenital transmission occurs at consistently high levels in pedigree Charollais and outbred sheep flocks s led over a 3-year period. Overall rates of transmission per pregnancy determined by PCR based diagnosis, were consistent over time in a commercial sheep flock (69%) and in sympatric (60%) and allopatric (41%) populations of Charollais sheep. The result of this was that 53.7 % of lambs were acquiring an infection prior to birth: 46.4% of live lambs and 90.0% of dead lambs (in agreement with the association made between T. gondii and abortion). No significant differences were observed between lamb sexes. Although we cannot distinguish between congenital transmission occurring due to primary infection at pregnancy or reactivation of chronic infection during pregnancy, our observations of consistently high levels of congenital transmission over successive lambings favour the latter.
Publisher: Cambridge University Press (CUP)
Date: 09-10-2007
DOI: 10.1017/S0031182007003721
Abstract: A study carried out on a sheep farm examined whether Toxoplasma gondii foetal infection and associated abortion occur in successive lambings. We identified 29 ewes that gave birth to lambs on at least 2 successive years over our study period, 2000–2003. Tissue s les from the progeny of these ewes were analysed by PCR to determine infection status with T. gondii . T. gondii -infected lambs were born in 31% of successive pregnancies. T. gondii -positive lambs were aborted in successive pregnancies in 21% of lambings during study period, 2000–2003. The frequency of successive abortions within this flock over the period 1992–2003 was 18%. If a lamb was congenitally infected there was a high risk (69%) that the successive lamb from that ewe would also be congenitally infected. Similarly, if a lamb was aborted there was a high risk (55%) of abortion in the next lamb produced. These data suggest that life-long immunity to T. gondii infections may not always be acquired following an initial infection and raises the question as to whether the mechanisms of T. gondii transmission prior to and during ovine pregnancies are fully understood.
Publisher: Elsevier BV
Date: 02-2001
DOI: 10.1016/S0020-7519(00)00158-2
Abstract: The position of mobile genetic elements (MGE) within eukaryotic genomes is often highly variable and we have exploited this phenomenon to develop a novel approach to strain differentiation in Toxoplasma gondii. Two PCR based strategies were designed in which specific primers were used to lify T. gondii MGE's revealing information on element size and positional variation. The first PCR strategy involved the use of a standard two primer PCR while the second strategy used a single specific primer in a step-up PCR protocol. This approach was applied to T. gondii reference strains which were either acute virulent or avirulent to mice. The use of a standard two primer PCR reaction revealed the presence of a virulence related marker in which all avirulent strains possessed an additional 688 bp band. The single primer PCR strategy demonstrated that all virulent strains had identical banding patterns suggesting invariance within this group of strains. However, all avirulent strains had different banding patterns indicating the presence of a number of in idual lineages within this group. The applicability and sensitivity of MGE-PCR in epidemiological studies was demonstrated by direct lification of T. gondii from sheep tissue s les. All sheep isolates, tested in this way, gave identical banding patterns suggesting the presence of an endemic Toxoplasma strain on this farm.
Publisher: Cambridge University Press (CUP)
Date: 15-09-2005
DOI: 10.1017/S0031182005008784
Abstract: Neospora caninum and Toxoplasma gondii are closely related intracellular protozoan parasites associated with bovine and ovine abortion respectively. Little is known about the extent of Neospora/Toxoplasma co-infection in naturally infected populations of animals. Using nested PCR techniques, based on primers from the Nc5 region of N. caninum and SAG1 for T. gondii , the prevalence of N. caninum and its co-infection with T. gondii were investigated in populations of Mus domesticus , Rattus norvegicus and aborted lambs ( Ovis aries ). A low frequency of infection with N. caninum was detected in the Mus domesticus (3%) and Rattus norvegicus (4·4%) populations. A relatively high frequency of infection with N. caninum was detected in the brains of aborted lambs (18·9%). There was no significant relationship between N. caninum and T. gondii co-infection. Investigation of the tissue distribution of Neospora , in aborted lambs, showed that Neospora could not be detected in tissues other than brain and this was in contrast to Toxoplasma where the parasite could be frequently detected in a range of tissues.
Publisher: Elsevier BV
Date: 12-2018
DOI: 10.1016/J.VPRSR.2018.10.009
Abstract: Toxoplasmosis is a zoonotic disease of worldwide distribution. The parasite exhibits strong geographical patterns of strain variation with contrasting high levels of ersity across South America and restricted variation across North America. Little is known about the ersity of strains in the transitional area between the two continents. Here we present data on the prevalance and ersity of Toxoplasma gondii in the Yucatan peninsula of Mexico, through a study in commercially reared pigs. A survey of 12 farms found evidence of circulating T. gondii DNA in 125 of 632 blood s les (19.8%, CI: 16.7%-23%). In addition, 46 tongue s les were collected from culled animals and 16 of these were positive for T. gondii DNA and 3 were positive in mouse bioassay. PCR-sequencing was used to generate genotyping data from blood and tissue s les. Four loci (SAG1, 2, 3 and GRA6) were reliably lified and revealed a high ersity among Yucatan strains with evidence of recombination and novel alleles. Sequencing data from the four loci was achieved in eight s les each of which had a different genotype. The predominant allelic type was atypical, in relation to the dominant strain types (I, II, III), the number of allelic variants being 27 (I, II-III, u-1-25), 20 (I, III, u1-18), 6 (I, III, u1-4) and 11 (I, II, u1-9) for the SAG1, SAG2, SAG3 and GRA6 loci respectively. Phylogenetic analysis showed that T. gondii strains from Yucatan shared alleles with strains originating from both North and South America. Our findings are consistent with data from other regions of Central America and suggest the genetic population structure of the parasite, with significant levels of allelic variation and recombination, constitutes a reservoir from which new strains may emerge. Positive bioassay results (7.5%) indicate that consumption of undercooked pork could be a potential T. gondii infection risk to humans.
Publisher: Cambridge University Press (CUP)
Date: 21-09-2009
DOI: 10.1017/S0031182009990941
Abstract: Toxoplasma gondii is a highly ubiquitous and prevalent parasite. Despite the cat being the only definitive host, it is found in almost all geographical areas and warm blooded animals. Three routes of transmission are recognised: ingestion of oocysts shed by the cat, carnivory and congenital transmission. In natural populations, it is difficult to establish the relative importance of these routes. This paper reviews recent work in our laboratory which suggests that congenital transmission may be much more important than previously thought. Using PCR detection of the parasite, studies in sheep show that congenital transmission may occur in as many as 66% of pregnancies. Furthermore, in families of sheep on the same farm, exposed to the same sources of oocysts, significant ergent prevalences of Toxoplasma infection and abortion are found between different families. The data suggest that breeding from infected ewes increases the risk of subsequent abortion and infection in lambs. Congenital transmission rates in a natural population of mice were found to be 75%. Interestingly, congenital transmission rates in humans were measured at 19·8%. The results presented in these studies differ from those of other published studies and suggest that vertical transmission may be much more important than previously thought.
Publisher: Elsevier BV
Date: 12-2001
DOI: 10.1016/S0020-7519(01)00282-X
Abstract: Our current understanding of congenital transmission of Toxoplasma gondii from ewe to lamb dictates that infection frequently results in abortion and the death of the developing foetus, that the birth of live infected lambs occurs rarely and that the cat is the predominant source of infection in ewes. Using direct polymerase chain reaction detection of T. gondii, we report high levels of congenital transmission occurring in a commercially managed sheep flock. We s led foetal-derived placental tissue and tissues from aborted lambs and showed that congenital transmission was detected in these tissues from 61% of all pregnancies. Where pregnancies resulted in the death of one or more lambs, T. gondii was detected in the lamb tissue for all but one of 18 (94%) pregnancies. Of the successful pregnancies resulting in the birth of live lambs we were able to detect T. gondii in foetal-derived placental tissue from 37 of 70 (42%) pregnancies. These results show that congenital transmission is occurring in a high percentage of lambings including normal healthy lambings, at this farm, suggesting that this route of transmission from generation to generation may be much more significant than that reported previously. These results may have implications for sheep husbandry and future epidemiological studies of T. gondii.
Publisher: Cambridge University Press (CUP)
Date: 2004
DOI: 10.1017/S0031182003004189
Abstract: The relative importance of different transmission routes of Toxoplasma gondii has been a matter for debate. This ubiquitous parasite is generally thought to be transmitted by infective oocysts excreted by the definitive host, the cat. Ingestion of undercooked meat has also been considered an important route of transmission in many mammals while congenital transmission has generally been considered relatively rare. Experimental studies demonstrate the ability of T. gondii to be transmitted congenitally, but few studies have investigated the frequency of this transmission route in natural populations. We use PCR lification of the SAG1 gene to investigate the frequency of congenital transmission in a wild population of mice ( Mus domesticus ) and show that congenital transmission is occurring in 75% of pregnancies in this population. Furthermore, for infected pregnant mice, transmission occurs to at least one foetus in 100% of cases while variable penetrance of congenital infection is observed. These high levels of congenital transmission in this wild population of mice, taken together with other recent data on congenital transmission in sheep, suggests that this phenomenon might be more widespread than previously thought.
Publisher: Cambridge University Press (CUP)
Date: 18-04-2005
DOI: 10.1017/S0031182005007614
Abstract: A study was carried out to investigate the frequencies of abortion and congenital Toxoplasma gondii infection within 27 families (765 in iduals) of a pedigree Charollais sheep flock maintained on a working farm in Worcestershire, UK, since 1992. Pedigree lambing records were analysed to establish the frequency of abortion for each family. The frequency of congenital infection was determined for each family by PCR analysis of tissue s les taken from newborn lambs. A total of 155 lambs were tested for congenital T. gondii infection, which were all born during the study period 2000–2003. Significant differences in the frequency of abortion between sheep families within this flock were observed with frequencies ranging between 0% and 48% ( P ·01). Significantly different infection frequencies with T. gondii were also observed for different families and ranged between 0% and 100% ( P ·01). Although the actual cause of each abortion was not verified, a highly significant positive correlation was found to exist between the frequency of abortion and the frequency of T. gondii infection in the same families ( P ·01). The data presented here raise further questions regarding the significance of congenital transmission of T. gondii within sheep populations, the possible successive vertical transmission of T. gondii within families of sheep, and the potential role of inherited genetic susceptibility to abortion with respect to T. gondii infection. This work invites further study into the epidemiology of ovine toxoplasmosis and may have implications for sheep husbandry methods in the future.
Publisher: Elsevier BV
Date: 08-2014
DOI: 10.1016/J.MEEGID.2014.05.032
Abstract: Toxoplasma gondii is a highly successful parasite with a worldwide prevalence. Small rodents are the main intermediate hosts, and there is growing evidence that T. gondii modifies their behaviour. Chronically infected rodents show impaired learning capacity, enhanced activity, and, most importantly, a reduction of the innate fear towards cat odour. This modification of host behaviour ensures a successful transmission of T. gondii from rodents to felids, the definitive hosts of the parasite. Given the negative fitness consequences of this behavioural manipulation, as well as an increased mortality during the acute phase of infection, we expect rodents to evolve potent resistance mechanisms that prevent or control infection. Indeed, studies in laboratory mice have identified candidate genes for T. gondii resistance. Of particular importance appear to be the innate immune receptors Toll-like receptor 11 (TLR11) and Toll-like receptor 12 (TLR12), which recognise T. gondii profilin and initiate immune responses against the parasite. Here we analyse the genetic ersity of TLR11 and TLR12 in a natural population of wood mice (Apodemus sylvaticus), and test for associations between TLR11 and TLR12 polymorphisms and T. gondii infection, as well as for epistatic interactions between TLR11 and TLR12 on infection status. We found that both TLR11 and TLR12 were polymorphic in wood mice, with four and nine amino acid haplotypes, respectively. However, we found no evidence that TLR11 or TLR12 genotypes or haplotypes were significantly associated with Toxoplasma infection. Despite the importance of TLR11 and TLR12 in T. gondii recognition and immune defence initiation, naturally occurring polymorphisms at TLR11 and TLR12 thus appear to play a minor role in mediating qualitative resistance to T. gondii in natural host populations of A. sylvaticus. This highlights the importance of assessing the role of candidate genes for parasite resistance identified in a laboratory setting in an ecologically meaningful context to quantify their role in mediating host-parasite interactions in the wild.
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Geoff Hide.