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Biomedical subjects

K D Murrell

Publications and source records attributed to K D Murrell.

At least 37 records · Page 2Linked to original sources
PubMed2001

Trichinellosis: now and forevermore?

The re-emergence of the zoonotic importance of trichinellosis reminds us that this parasite's unique biological features serve it well in helping it to persist in the face of 150 years of efforts to eliminate it from the food chain. Because of Trichinella's re-emergence as an important public health risk, and the consequent stimulation of research, our knowledge of the parasite has grown, especially on the complexity of its biology and epidemiology. This overview will highlight the major features of this parasite's adaptive traits and the human factors that account for its re-emergence in many regions, along with the actions of the International Trichinellosis Commission to address these issues. The attractiveness of Trichinella as a research subject for study of the parasitic lifestyle will also be emphasized, including areas for future research.

Animals↗
PubMed2001

The lateral flow card test: an alternative method for the detection of Trichinella infection in swine.

A novel lateral flow card (TS-Card pork) test was developed for the serological detection of Trichinella infected pigs. Based on extensive studies performed in Romania during 1999-2000 this test proved to be highly specific sensitive, rapid (3-12 minutes) and easy to use (no need for laboratory facilities). It can be used both for the detection of Trichinella infection in carcasses and for epizooliological studies using a variety of samples including whole or dried blood, serum, or tissue fluids. The TS-Card pork test, used as a screening test, can be the foundation of an on-farm or field based inspection system to significantly improve food safety in countries with a high prevalence of Trichinella in pigs or other food animal species. The results presented are also promising for application of the test in an on-line laboratory based inspection system since the speed of the test allows sufficient time to rail out suspected hog carcasses during the slaughter process.

Animals↗
PubMed2000

The systematics of the genus Trichinella with a key to species.

The authors review the major biological, biochemical, and molecular characters that are used to distinguish the seven Trichinella species (T. spiralis, T. nativa, T. britovi, T. pseudospiralis, T. murrelli, T. nelsoni, T. papuae) and three genotypes whose taxonomic status is yet uncertain (T-6, T-8, T-9). A comparison of host specificity, morphology, reproductive abilities, nurse cell development and freeze resistance is presented, along with useful biochemical and molecular markers. Finally, this information is used to construct a diagnostic key for the species. A phylogenetic classification of the species is needed.

Animals↗
PubMed2000

Pigs become infected after ingestion of livers and lungs from chickens infected with Ascaris of pig origin.

An experimental infection with Ascaris of pig origin showed that Ascaris suum larvae can migrate extra-intestinally in chickens. Furthermore, after feeding piglets with Ascaris infected chicken liver and lungs, it was possible to recover larvae from their lungs. These observations suggest that the chicken could serve as a paratenic host for Ascaris. There is also the possibility for zoonotic transmission if raw chicken livers are consumed by humans.

Animals↗
PubMed2000

Trichinellosis: the zoonosis that won't go quietly.

Trichinellosis, is normally not included among those regarded as emerging zoonoses because it has been a public health threat for more than 150 years. However, its dramatic re-emergence in many areas around the world over the past 10-20 years, inspite of a century of veterinary public health efforts to control and eradicate it, justifies it being included in this group. The reasons for this re-emergence are diverse, and include human pertubation and manipulation of ecosystems, war and political turmoil, rapidly changing food distribution and marketing systems, and even, surprisingly, rising affluence in developing countries. These influences, and their impact on the epidemiology of both domestic and sylvatic trichinellosis, are discussed, along with recommendations for confronting this altered status as a public health threat.

Animals↗
PubMed1998

Trichinella spiralis, T. britovi, and T. nativa: infectivity, larval distribution in muscle, and antibody response after experimental infection of pigs.

The infectivity of Trichinella spiralis, T. nativa, and T. britovi was experimentally compared in pigs. Blood sampling was performed weekly, and muscle juices were obtained at slaughter 10 weeks after inoculation. Muscle larvae were found in all of four pigs inoculated with T. spiralis [mean 190 larvae per gram (lpg)] and in three of four pigs inoculated with T. britovi (mean 7 lpg). No larvae were found in pigs inoculated with T. nativa. For T. spiralis and T. britovi, the neck muscle (m. splenius) appears to be a predilection site in addition to the tongue, the diaphragm, and the jaw. High antibody responses were found in all experimental groups, independent of the antigen used, and even in pigs in which no muscle larvae were recovered. The strong and consistent antibody response found with meat juice indicates the usefulness of this material where a blood sample is not obtainable, e.g. meat samples from wild animals. Immunoblotting (Western blots) on slaughter sera revealed no species specificity when comparing homologous versus heterologous staining.

Animals↗
PubMed1998

Evaluation of the infectivity of Trichinella spp. for reptiles (Caiman sclerops).

Experimental inoculation with nine well-characterised Trichinella isolates was performed on caimans (Caiman sclerops) to determine their infectivity for reptiles belonging to the family Crocodilidae. As controls, the same larval batches of Trichinella isolates were inoculated into mice and guinea pigs. It was suggested that Trichinella pseudospiralis was more likely to infect reptiles than encapsulating species, but whereas all Trichinella species established in mice and guinea pigs, the caimans remained negative. The finding that caimans could not be experimentally infected contrasts with a recent report on infections in farmed crocodiles (Crocodylus niloticus).

Alligators and Crocodiles↗
PubMed1998

Detection of parasites in food.

The importance of foodborne parasitic zoonoses remains high in many regions of the world. Although control efforts have been exerted for quite some time, overall progress has not been satisfactory, even in many well developed countries. An important drawback in control programmes for parasites such as Trichinella, Toxoplasma and Taenia has been the absence of rapid, accurate and sensitive diagnostic tests for these meatborne parasites. However, the rapid advances in the molecular biology of these organisms has yielded concomitant gains in precision of detection. This review highlights these advances and their impact or potential application to the control of foodborne parasites.

Animals↗
PubMed1998

Early Ascaris suum migration in mice as a model for pigs.

A study was made of the early migratory pattern of Ascaris suum in mice. Mice were each inoculated orally with a single dose of 2,500 infective eggs and then killed at 2, 4, 6, 8, 10, and 12 hr postinoculation (PI). At necropsy, it was observed that the larvae had penetrated the mouse cecum and colon and had reached the liver by 4 hr PI. This migratory behavior closely mimics what is observed in the pig and suggests that the mouse may serve as an experimental model for intestinal immunity in the early phase of A. suum infection.

Animals↗
PubMed1997

Transmission dynamics of helminth parasites of pigs on continuous pasture: Ascaris suum and Trichuris suis.

In Denmark, alternative outdoor production systems for pigs are becoming more frequent, and information on the transmission of Ascaris suum and Trichuris suis under continuously grazed pasture conditions is needed. A group of pigs was turned out on a pasture in May 1993 (Year 1 of the study), inoculated with 200 eggs of A. suum and 1000 eggs of T. suis, and followed parasitologically. A non-experimentally infected group of pigs was similarly turned out on the same pasture the following year (Year 2) and again followed parasitologically. Pasture infectivity was measured using helminth-naïve tracer pigs. During the summer of Year 1, A. suum eggs became infective within 4-6 weeks on the pasture. However, transmission was moderate until August of Year 2, when a pronounced increase in transmission occurred. After 2 months on the pasture, the continuously exposed pigs in summer seasons of both Years 1 and 2 harboured small overdispersed populations of adult A. suum, moderate numbers of liver white spots, and high specific IgG responses. These parasitological measures on chronically exposed pigs did not, however, correlate well with pasture infectivity or with each other. In contrast, the liver inflammation and specific IgG responses (but not the intestinal A. suum burdens) of the tracer pigs were highly correlated (P = 0.0001) and appeared to better reflect pasture infectivity. The inoculated pigs excreted T. suis eggs by the late summer of Year 1, but no transmission took place before August of Year 2. Thus, the T. suis population of infective eggs built up very slowly. The results indicate that T. suis eggs may survive for a considerable time, however. The study results reveal that A. suum and T. suis eggs are much more resistant to environmental factors than free-living infective larvae of pig parasites such as Oesophagostomum dentatum and Hyostrongylus rubidus. Control of these parasites in outdoor systems will present more difficult challenges than that for parasites transmitted by free-living larvae.

Animal Husbandry↗
PubMed1997

Transmission dynamics of helminth parasites of pigs on continuous pasture: Oesophagostomum dentatum and Hyostrongylus rubidus.

An increase in alternative outdoor pig production systems is occurring in Denmark, and this study was designed to elucidate the transmission patterns of Oesophagostomum dentatum and Hyostrongylus rubidus in pigs allowed to graze continuously on a pasture. A group of pigs was turned out in May 1993 (Year 1 of the study) and subsequently inoculated with low numbers of both helminths. These pigs were followed parasitologically until October by serial necropsy and sampling of faeces, grass and soil. A non-inoculated group of pigs was similarly followed on the same pasture in Year 2 (1994). Pasture infectivity was measured using helminth-naïve tracer pigs during all seasons. The pasture vegetation was rapidly destroyed by the pigs, resulting in a dirt lot by the autumn of Year 2. The area was soon contaminated with eggs, resulting in heavy pasture infectivity and increasing worm burdens in late summer; then the numbers of larvae declined markedly. In May of Year 2, newly exposed pigs became only lightly infected (mostly O. dentatum), and no transmission was observed in July-August of Year 2, probably due to an unusually dry summer and a lack of protecting vegetation. The results indicate that both O. dentatum and H. rubidus are very sensitive to environmental factors, because significant transmission occurred only under the most favourable conditions (summer combined with protecting vegetation as in Year 1). Transmission was severely reduced during the low temperatures experienced in the winter between Years 1 and 2 and during the dry summer of Year 2, when vegetation was lacking. Continuous grazing actually reduced transmission of O. dentatum and H. rubidus because of the reduction in vegetation. This, however, is not a desirable alternative farming system, because of its adverse environmental effects. This environmental impact may be mitigated by employment of a pasture rotation system in place of continuous grazing.

Animal Husbandry↗
PubMed1997

Comparison of methods for recovery of Ascaris suum larvae from tissues of mice.

Experiments were undertaken to compare procedures for isolating Ascaris suum from mice. A standardised intragastric procedure for inoculation of A. suum eggs, which had a very low interdose variation (S.D. = 6.2% of mean inoculation dose), was developed. There was no significant difference in the number of larvae recovered from the large intestine 4 h post inoculation (p.i.) by using either Baermannisation of washed intestinal wall or submucosal scrapings. In contrast, a significantly higher recovery of larvae was achieved by incubating the intestines vertically in a cylindrical saline-filled funnel. An agar-gel method was used to recover larvae from mucosal scrapings; however, the number of larvae recovered was the lowest of the methods tried. It was found that a significant increase in larval recovery from the liver at 24 h p.i. resulted when the liver was pressed through a garlic press, rather than by using homogenisation. For lung recovery, the highest recovery of larvae (at day 8 p.i.) was obtained by disintegration of tissue with a pair of scissors and incorporating the tissue into agar-gel. The methods presented in this study may be useful for investigation of the histology, morphology and molecular biology of the early of A. suum.

Animals↗
PubMed1997

Parasites of fish and risks to public health.

A multitude of parasites have been reported in fish, but only a few species are capable of infecting humans. The most important of the helminths acquired by humans from fish are the anisakid nematodes (particularly Anisakis simplex and Pseudoterranova decipiens), cestodes of the genus Diphyllobothrium and digenetic trematodes of the families Heterophyidae, Opisthorchiidae and Nanophyetidae. Seafood-associated infections by acanthocephalans are rarely reported in humans. All of the helminths mentioned above are associated with social-cultural and behavioural factors, in particular the consumption of raw or undercooked seafood. Measures can be taken during harvesting, processing or post-processing (e.g., by the consumer) to mitigate the risks of infection. The seafood industry and government authorities can apply various programmes to reduce these risks, including good manufacturing practices (GMPs) and hazard analysis and critical control point (HACCP) systems. Such measures may include avoiding particular harvest areas, sizes of fish, or even particular species of fish. The method of capture, handling and storage of the catch can directly affect the quality of the seafood with regard to the presence and numbers of parasites. The extent of processing--including heading and gutting, candling and trimming--and the type of product derived (fresh, frozen, salted or pickled) can all contribute to the control of the risks posed by helminths. The most effective means of killing the parasites are either freezing or heat inactivation.

Animals↗
PubMed1997

Ascaris suum: a revision of its early migratory path and implications for human ascariasis.

During the course of carrying out studies on the role of intestinal immunity in blocking the migration of larval Ascaris suum in the pig, it was discovered that the prevailing understanding of larval penetration sites was at variance with our observations. Therefore, a detailed investigation of the migration of A. suum 1.2 larvae through the intestine was initiated. The results demonstrate that the 1.2 larvae invade almost exclusively the wall of the pig cecum and colon and not the small intestine as is generally believed. The larvae were recovered from the mucosa of the cecum and colon as early as 3 hr postinoculation (PI) with infective eggs and were recovered from the liver by 6 hr PI. The maximal recovery of larvae (total larvae and larval/g of mucosa) from the intestinal mucosa occurred between 6 and 12 hr PI; by 24 hr PI, virtually all of the larvae had disappeared from the mucosa. These observations correct a common misunderstanding of this aspect of the life cycle of A. suum in the pig, and they raise 2 issues related to the biology and pathogenesis of Ascaris in humans. What is the actual migratory and development behavior of Ascaris lumbricoides and A. suum in humans and the potential risk for liver lesions? Most authors, in describing the life cycle of A. lumbricoides, either ignore or discount a possible obligatory liver stage of development, and, consequently, the potential for lesion formation similar to that which occurs in pigs infected with A. suum. This issue takes on added importance with the growing evidence that A. suum is an important zoonoses.

Animals↗
PubMed1997

Improved method for the recovery of Ascarus suum larvae from pig intestinal mucosa.

In the course of a comprehensive study on the population biology of Ascaris suum, it became necessary to determine quantitatively the migration of the larvae (L2) through the pig intestine. Because no satisfactory methods for recovering these larvae from the intestinal mucosa were apparently available in the literature, we undertook the development of such a procedure. Direct Baermannization of the intestine proved inadequate, so a series of studies was undertaken to find a method to solubilize the mucosa and free the larvae. Both pepsin digestion and mucus reduction with N-acetyl cysteine were evaluated. The highest recovery rates were obtained with short-term pepsin digestion (45-90 min), followed by a specific settling and washing procedure. A third alternative, migration of larvae out of agar-gel, was also tested. Although the recovery efficiency was low (10% of pepsin digestion), the larvae recovered were clean, with good motility. The agar-gel procedure could be useful when L2 larvae are needed for other purposes, such as antigen preparation or cultivation.

Acetylcysteine↗
PubMed1996

Communications: technology transfer in the developed world.

Support for research is increasingly dependent upon the results of that research having relevance to society's needs and public benefits. This increase pressure to move research results out of the laboratory and into the user's hands. To facilitate this, a variety of technology transfer mechanisms have evolved to facilitate transfer of knowledge and processes. These mechanisms, in addition to their implied benefits for the researchers and the user, often have certain consequences which are unanticipated and cause transfer to fail or not meet expectations. Foremost, cultural change on the part of both private organizations and public laboratories is probably necessary to allow effective partnerships. Coupled with the transfer of knowledge is the opportunity to more effectively explain to society the benefits it receives for its investments in research. Such communication has not been especially successful for veterinary parasitology. However, the revolution in communication (e.g. rise of mass media, computer networks) presents new opportunities to parasitologists to more effectively communicate both technology and knowledge directly to the users, and also to inform supporters, policy-makers and the general public of the relevance and importance of veterinary parasitology in improving society's well-being. This review will discuss these new instruments of communication, the need to construct better messages, the benefits of technology transfer and the various means to meet the challenges associated with transferring research innovation to the user and the marketplace.

Animals↗