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Biomedical subjects

D W Crompton

Publications and source records attributed to D W Crompton.

At least 19 recordsLinked to original sources
PubMed2001

Ascaris and ascariasis.

In recent years much new information has been obtained about the epidemiology, population biology and public health significance of infections of Ascaris lumbricoides in humans. Results from experimental infections of A. suum in pigs have helped to elucidate the observations made in the community on human ascariasis. The main purpose of the review is to see how new information may contribute to further acceptance of ascariasis as a serious contributor to ill-health and so to the design and implementation of sustainable control programmes intended to reduce the morbidity due to infection with A. lumbricoides. Eradication is neither a realistic nor prudent aim given the current shortage of appropriate sanitation in many countries where ascariasis is endemic. A substantial body of evidence shows that for the four common species of soil-transmitted nematode, including A. lumbricoides, regular administration of broad-spectrum anthelminthic drugs to children attending primary schools is a cost-effective means of controlling the infections. Anthelminthic drugs must be of proven quality and efficacy and health professionals should be prepared to detect and manage drug resistance should that emerge. Despite a deeper understanding of the immune response of a variety of hosts to infections with either A. lumbricoides or A. suum there is at present little prospect of an effective vaccine against ascariasis. The relationship between A. lumbricoides and A. suum is addressed, particularly since both species, if they are indeed separate species, occur in people and their pigs in many communities.

Adult↗
PubMed2000

The public health importance of hookworm disease.

The public health significance of hookworm disease is briefly reviewed. The latest evidence confirms that blood loss caused by the worms' feeding activity in the gut is a contributing factor in the development of poor iron status leading to iron-deficiency anaemia. The World Health Organization has identified adolescent girls and women of child-bearing age as high-risk groups regarding the impact of hookworm disease. The merits of treating pregnant women with anthelminthic drugs after the first trimester are discussed.

Adolescent↗
PubMed1999

Control strategies for human intestinal nematode infections.

In recent years significant progress has been made in understanding the ecology, epidemiology and related morbidity and development of new tools for the control of soil-transmitted helminths. Such knowledge has recognized the impact of helminth infections on the health of infected groups and has created a rational basis for their control. Schoolchildren harbour some of the most intense helminthic infections, which produce adverse effects on health, growth and scholastic performance. However, although great effort has been put into targeting school-age children, women of child-bearing age and pre-school children are two other groups at high risk of morbidity due to intestinal nematode infections. Highly effective and safety-tested, single-dose anthelminthic drugs are now available, permitting periodical deworming of schoolchildren and other high-risk groups at affordable prices. Four anthelminthics against all intestinal nematodes are included in the WHO Essential Drug List (albendazole, levamisole, mebendazole and pyrantel). Recently ivermectin has also been registered for use against Strongyloides stercoralis in humans. Several well-monitored country experiences have shown that chemotherapy-based control of morbidity due to soil-transmitted helminths is possible and highly cost-effective.

Africa↗
PubMed1999

Reintroduction of Profilicollis Meyer, 1931, as a genus in acenthocephala: significance of the intermediate host.

Polymorphid acanthocephalans with long necks, spheroid proboscides, and eggs without polar swellings of the fertilization membrane constitute a morphologically distinct group of species. In the past, this taxon was considered a separate genus, Profilicollis. More recently, workers have been unwilling to accept these features as generic-level characters, and presently the group is considered a subgenus of Polymorphus. An analysis prompted by our studies of various polymorphid cystacanths in crabs along the coasts of Scotland and the U.S.A. reveals that all records of Polymorphus in decapods refer to species with 6 cement glands frequently assigned to Hexaglandula, to incidental occurrences of species purported to be Polymorphus minutus, or to species of the subgenus Profilicollis. Occurrence in decapod crustaceans implies substantial life history differences from the other species of the genus occurring in amphipod crustaceans. We conclude this, together with morphological distinctiveness, justifies return of Profilicollis to full generic status within Polymorphidae.

Acanthocephala↗
PubMed1998

Transmission and natural regulation of infection with Ascaris lumbricoides in a rural community in China.

A longitudinal study on a cohort of 215 people who remained untreated from June 1993 to June 1994 was carried out using fecal egg counts to examine the course of transmission and aspects of the natural regulation of the infection with Ascaris lumbricoides. The results indicate that the parasite population remained relatively stable during the years since overall prevalence remained steady above 60%. About 40% of the people in the cohort retained their infection intensity status throughout the year, in terms of light, medium, and heavy infections. The regulation of infection in the population could be attributed to the tendency for the loss of worms from people with initial light infections and the movement to medium infection intensity status of people with both light and heavy infections. Compared with adults, children showed a stronger tendency of retaining initial medium infections but weaker tendencies for keeping initial light infections and clearing themselves of infection. Predisposition to light and medium infections was detected in people who had experienced an uninfected period of 4-12 mo before reinfection was established.

Adolescent↗
PubMed1997

The ecology of Diplostomum phoxini infections in two minnow (Phoxinus phoxinus) populations in Scotland.

Data are presented on the infection dynamics of the brain-dwelling metacercariae of Diplostomum phoxini (Digenea: Trematoda) parasitizing European minnow (Phoxinus phoxinus) populations in a lowland river (River Endrick) and a highland loch (Loch Maragan) in central Scotland. Prevalence of the parasite approached 100% in all samples taken from both populations over a 12-month period, and within each population the intensity of infection increased with increasing host fork length. However, the two relationships differed, and size-matched minnows from the Endrick exhibited significantly higher intensities than those from Loch Maragan, suggesting that metacercarial acquisition occurred at different rates in the two populations. Data regarding seasonal trends in the acquisition of D. phoxini indicated that fish in both populations become infected with the parasites mainly during the spring and summer, with negligible infection occurring during winter months. Analysis of size-matched fish from individual samples revealed apparent differences in the distribution of D. phoxini within the two host populations. Whereas D. phoxini metacercariae appeared to be overdispersed amongst length-matched fish from Loch Maragan samples, the parasite was distributed normally amongst fish from the Endrick. Possible reasons for the observed differences in the infection characteristics of D. phoxini in the two minnow populations are discussed, with reference to the parasite's transmission dynamics and local environmental conditions.

Animals↗
PubMed1997

The distribution of the metacercariae of Diplostomum phoxini in the brain of minnows, Phoxinus phoxinus.

Quantitative data are presented on the spatial distribution of metacercariae of the digenean trematode Diplostomum phoxini (Faust, 1918) in the brains of minnows, Phoxinus phoxinus (Linnaeus, 1758), from two Scottish populations. Sequential examination of serial histological sections revealed metacercariae to be unevenly distributed throughout the brain, aggregating in specific regions including the cerebellum, the medulla oblongata and the optic lobes. In addition, a number of metacercariae were found in the anterior part of the spinal cord. The inferior lobe of the cerebellum, pituitary, olfactory lobes and olfactory bulbs were largely free of metacercariae. Reasons for the uneven distribution of metacercariae within the brains of infected minnows are discussed, including the possibility that the parasite may have evolved to enhance its transmission to subsequent hosts by aggregating in regions known to be important in the control of the host's antipredator responses.

Animals↗
PubMed1996

Targeted anthelminthic treatment of school children: effect of frequency of application on the intensity of Ascaris lumbricoides infection in children from rural Nigerian villages.

A study to compare the effects of different frequencies of targeted chemotherapy with levamisole (Ketrax: JAGAL Pharma, Lagos, Zeneca Pharmaceuticals UK) as an action for the control of Ascaris lumbricoides was carried out in 3 communities in rural Oyo State, Nigeria. The targeted group comprised children, age 5 to 15 years, attending primary school within their village. Treatment was provided within the school with the assistance of the school teachers. Three frequencies of targeted treatment were offered. In one village targeted treatment was provided on 1 occasion in 1 year, in another village at two 6-monthly intervals and in the third village every 4 months. Prevalence and intensity (e.p.g.) of A. lumbricoides infection were determined immediately before and after the period of intervention using a modified Kato-Katz technique. In the villages which received treatment once and at 6-monthly intervals, a reduction in post-treatment intensity of A. lumbricoides was observed in the total population but this failed to attain statistical significance. In contrast, within the village which received 4-monthly targeted chemotherapy, a significant reduction in post-treatment intensity of A. lumbricoides was observed in the total population and in the targeted children. In general, reductions in the intensity of A lumbricoides after intervention were not particularly pronounced in untreated children (aged 0-4 years) even in the 4-monthly targeted village, whereas in untreated adults, reductions approached statistical significance in villages which received targeted treatment once and at 4-monthly intervals.

Adolescent↗
PubMed1996

Ascaris, people and pigs in a rural community of Jiangxi Province, China.

A longitudinal investigation on natural populations of Ascaris in humans and pigs and an investigation of soil contamination with Ascaris eggs were carried out from June 1993 to June 1994 in 2 villages, Manhu area, Xinjian County, Jiangxi Province, China. Results from these studies indicate that although human ascariasis is endemic there is significant fluctuation in both prevalence and the mean number of eggs/g faeces (epg) of the communities. Fluctuation of age-stratified prevalence and mean epg was detected in children but not in most adult groups. Most cases of human ascariasis were judged to involve low intensities of infection and a typical overdispersion distribution pattern was observed through the year. It was estimated that during the year, nearly half of the eggs discharged in the environment came from infections in children aged between 2 and 15 years which accounted for about 30% of the total population. Soil in and around houses and in vegetable gardens was found to be contaminated by Ascaris eggs and this situation remained relatively stable throughout the year. Monthly developmental rate of Ascaris eggs in soil was detected and the results suggest that the fluctuation in prevalence observed during the year should be directly attributed to the effect of seasonality of egg development. Features of Ascaris infection in pigs were found to be similar to those in humans except for a lower mean intensity of infection. The possibility of cross-infection of Ascaris between human and pig hosts is discussed.

Adolescent↗
PubMed1996

A cost-effectiveness analysis of anthelminthic intervention for community control of soil-transmitted helminth infection: levamisole and Ascaris lumbricoides.

A study to compare effects of mass, targeted, and selective chemotherapy with levamisole as an intervention for the control of Ascaris lumbricoides was carried out in 3 communities in rural Oyo State, Nigeria. Selective treatment was applied in 1 village by treating the most heavily infected 20% of the inhabitants, targeted treatment in the second village involved children aged 2-15 yr, whereas mass treatment was offered to all inhabitants in the third village, excluding infants under 1 yr and pregnant women. Intensity (eggs per gram,) of A. lumbricoides infection was determined immediately before and 3 mo after the period of intervention as a means of assessing the relative efficacy of the treatment regimes. During the field study, information on resource use was also collected for a retrospective cost analysis of the 3 strategies Resources used included manpower, materials, drugs, and transport. The results of the parasitological evaluation on the effect of treatment on egg intensity were then combined with the cost analysis to provide an overall measure of the cost-effectiveness of mass, targeted, and selective interventions. The results were expressed in terms of the cost per 1,000 egg reduction in intensity and the cost per person treated. The results showed the mass and targeted approach to be considerably more cost effective than the selective approach.

Adolescent↗
PubMed1995

Changes in metabolism and behaviour of the freshwater copepod Cyclops strenuus abyssorum infected with Diphyllobothrium spp.

In a population of copepods (Cyclops strenuus abyssorum), with a naturally high prevalence of infection with procercoids of Diphyllobothrium spp., no difference in body size was found between infected and uninfected hosts. However, a significant reduction in the reproductive capacity of infected females was observed, 87% of uninfected females having developed eggs in their gonads and sacs compared with 21% of infected females. The feeding rate of infected copepods was relatively high soon after infection occurred, but gradually decreased to less than half that of uninfected animals. Respiration rate was also lower in infected copepods. Infected copepods showed reduced motility and impaired escape responses, which is likely to make them more susceptible to predation.

Animals↗
PubMed1995

Andracantha tunitae (Acanthocephala) in the shag (Phalacrocorax aristotelis) from Shetland, Scotland.

Following the wreck of the oil tanker Braer on the coast of Shetland, Scotland, in January 1993, many shags (Phalacrocorax aristotelis) were killed. Sixty-nine per cent of these birds were found to harbor a sexually mature acanthocephalan (5 +/- 4.3 [SE] worms per infected bird) in their small intestines. The acanthocephalan has been identified as Andracantha tunitae (= Corynosoma tunitae) on the basis of its characteristic fields of trunk spines and their distribution in the region of the genital aperture.

Acanthocephala↗
PubMed1995

The ecology of endoparasitic helminth infections of brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) in Scotland.

Two hundred and forty brown trout (Salmo trutta) and 49 rainbow trout (Oncorhynchus mykiss), obtained from 21 locations in Central Scotland between October 1990 and August 1993, were examined for endoparasitic helminth infections. Crepidostomum farionis (Digenea) was the most widely distributed helminth species, followed by Eubothrium crassum (Cestoda), Diphyllobothrium dendriticum and D. ditremum (Cestoda), Neoechinorhynchus rutili (Acanthocephala), Echinorhynchus truttae (Acanthocephala), Eustrongylides sp. (Nematoda), Capillaria salvelini (Nematoda), Cyathocephalus truncatus (Cestoda), Raphidascaris acus (Nematoda) and Cystidicola farionis (Nematoda), in that order. The prevalences and intensities of each helminth infection were recorded. No evidence was found to indicate that even fish with the highest worm burdens (e.g. 339 plerocercoids of Diphyllobothrium spp.) were experiencing any obvious morbidity. An analysis of pairs of associations between species of helminths revealed a significantly positive association between N. rutili and C. farionis (P < 0.01). The results are discussed in terms of patterns in helminth communities in freshwater fish.

Acanthocephala↗
PubMed1994

Bactericidal activity in the pig roundworm Ascaris suum.

A potent, humoral, bactericidal activity against Micrococcus luteus was discovered in pseudocoelomic fluid of the pig roundworm, Ascaris suum. The activity, which was not bacteriolytic, was not due to lysozyme or to a dietary antibiotic. It was not inactivated by exposure to 100 degrees C, to low or high pH, or to ethanol. Dialysis, electrophoresis and agar-diffusion experiments suggested that the main antibacterial activity in the fluid was associated with a basic substance of molecular weight somewhat less than 14,000 Da. Two other Gram-positive organisms, Bacillus megaterium and Staphylococcus aureus, were also killed by the Ascaris fluid, but the Gram-negative Escherichia coli, Proteus vulgaris and Bordetella bronchiseptica were insensitive.

Animals↗