Biomedical subjects

D W Crompton

Publications and source records attributed to D W Crompton.

At least 37 records · Page 2Linked to original sources

PubMed1993

Hookworm infections and human iron metabolism.

Ancylostoma duodenale and Necator americanus are extremely common species of soil-transmitted helminth which flourish where poverty and malnutrition prevail. Hookworms contribute significantly to iron-deficiency anaemia, which remains one of the world's major nutritional problems, through the feeding activities of intestinal stages leading to chronic blood loss into the gut. In this article, a mathematical model is proposed to explain how human iron metabolism may respond to hookworm infection of varying intensity. The model draws attention to the importance of the regulation of stored iron levels in the process. The results from the model are presented for the effects of hookworm infection on the iron metabolism of a healthy adult male. Calculations are also presented in which the effects of hookworms on the iron metabolism of a non-pregnant woman are compared with those of a pregnant woman. Use of the model may help develop a better understanding of the pathology of hookworm disease.

Adolescent↗

PubMed1993

A quantitative study of the susceptibility of cockroach species to Moniliformis moniliformis (Acanthocephala).

We exposed 19 species of cockroaches to Moniliformis moniliformis by administering shelled acanthors orally and by injecting hatched acanthors directly into the body cavity. The exposure method had little influence on susceptibility: with one exception, species that were susceptible to oral exposure were also susceptible to injected acanthors and, in no case, did acanthors develop in injected animals when they did not develop in orally exposed conspecifics. We found no support for the hypothesis that the intestine may be a barrier to M. moniliformis establishment in cockroaches. There is, however, clear interspecific variation in susceptibility to M. moniliformis infection.

Administration, Oral↗

PubMed1993

Centrorhynchus aluconis (Acanthocephala) and other helminth species in tawny owls (Strix aluco) in Great Britain.

Observations on the distribution of Centrorhynchus aluconis (Acanthocephala) and 6 other species of helminths in the definitive host Strix aluco, in tawny owl, are presented. Infected owls were collected from 16 sites ranging from Tarbet, Strathclyde, Scotland, to Ewhurst, Surrey, in the south of England. In addition, unidentified cyclophyllidean cestodes were found in the alimentary tract of the tawny owls. Centrorhynchus aluconis was the most prevalent helminth found and had the highest intensity. It appears that C. aluconis is widely distributed in the tawny owls of Great Britain. Porrocaecum spirale (Nematoda) was the second most prevalent species of helminth. This species and C. aluconis are believed to be dependent on shrews (Sorex araneus and Sorex minutus) for their transmission to owls.

Acanthocephala↗

PubMed1993

Intestinal parasitic infections and urbanization.

About a third of the population in the cities of developing countries live in slums and shanty towns. By the year 2000 it is estimated that this number will grow to 2200 million, and by 2025 about 57% of the population in developing countries will be in urban areas. The prevalence of infections caused by Entamoeba histolytica and Giardia intestinalis and the prevalence and intensity of Ascaris lumbricoides and Trichuris trichiura infections may increase among the rural populations who are migrating to these urban and suburban settings owing to the favourable conditions for transmission. Urgent consideration should therefore be given to improving sanitation in deprived urban areas and to treating periodically these populations to reduce the worm burden, especially in school-age children.

Developing Countries↗

PubMed1992

The prevalence and intensity of soil-transmitted helminthiases in rural communities in southern Nigeria.

An investigation of the prevalence and intensity of soil-transmitted helminthiases was undertaken in four villages in Oyo state, Nigeria. Diagnosis was based on examination of stool samples for the presence of helminth ova in all age classes. The prevalence of Ascaris lumbriocoides ranged from 61.5-72.2%, of Trichuris trichiura from 65-74%, and of hookworm from 52.4-63% depending on the village concerned. Intensity, assessed indirectly as the mean eggs per gram of faeces (epg), varied with regard to the four villages. The mean egg count of A. lumbricoides varied from 6815-10,823 per gram, of T. trichiura from 127-246, and of hookworm from 122-267. Host age, sex and household size were found to be significant factors influencing faecal egg output, and indirect measure of the intensity of the helminth infections.

Adolescent↗

PubMed1992

The nutritional status of Guaymi Indians living in Chiriqui province, Republic of Panamá.

Guaymi Indian children have recently been identified as a population group who are at risk for vitamin A deficiency with numerous cases of xerophthalmia with ocular perforation being reported. A four-day parasitological and nutritional clinic based survey was conducted with 335 Guaymi women and children in the towns of San Felix and Alto Caballero to identify the prevalence of parasitic infections and factors associated with malnutrition. A subsample of 79 children, under 19 years of age, from independent families was constructed for the current analysis. The results of the study indicated that 20% of the children had a plasma vitamin A concentration less than 20 micrograms/dl. Significant associations were identified between ascariasis, age, a food diversity score and vitamin A concentrations. Other indicators of nutritional status were also negatively associated with intestinal parasitic infections, and a modernization index, using multivariate regression analysis. In conclusion, this study identified several factors associated with poor nutritional status that can be used by health officers to identify Guaymi children at risk for malnutrition.

Adolescent↗

PubMed1992

A possible genetic factor influencing protection from infection with Ascaris lumbricoides in Nigerian children.

An epidemiological study of Ascaris lumbricoides infections was carried out in primary school children aged 5-16 yr from Ile-Ife, Nigeria. Intensity of infection was assessed directly by means of counting worms passed during a 48-hr period after chemotherapy. Reinfection patterns of A. lumbricoides were assessed at 2 6-mo intervals and statistical evidence of predisposition to infection status was obtained. An investigation of 3 groups of children who were judged to be predisposed not to be infected, to be lightly infected, and to be heavily infected was undertaken. Assignment to the groups was based upon the mean worm burden plus 1 SD above the mean, measured at 2 6-mo intervals. The distribution of class I human leucocyte antigens among the 3 groups of children was described. None of the children who were predisposed to remain uninfected was found to possess the A30/31 antigens in contrast to those children who remained infected.

Adolescent↗

PubMed1992

Infectivity of plerocercoids of Schistocephalus solidus (Cestoda: Ligulidae) and fecundity of the adults in an experimental definitive host, Gallus gallus.

Aspects of the infectivity of the plerocercoid stage and the fecundity of the adult stage of Schistocephalus solidus were examined using the chicken, Gallus gallus, as an experimental host. To investigate size-related infectivity of the plerocercoid stage to a definitive host, a range of plerocercoids (166) were weighed, and each was fed to an individual male chicken. Only a very small percentage of plerocercoids weighing less than 50 mg established compared with in excess of 50% in all other weight classes. To examine the factors affecting the quantity of eggs produced by the adult stage, 15 similar-sized plerocercoids (160-218 mg) were fed to chickens. The majority of plerocercoids administered established as adults and survived until the experiment was terminated on day 7 postinfection (PI). Fecal egg counts indicated that all established worms commenced egg production on day 2 PI with peak output on day 2 or 3 PI. By day 7 PI, egg production in the surviving worms had declined, but it was still evident. The final weight of the adult and the average egg output per worm were unrelated to the initial weight of the infecting plerocercoid. However, the average egg output was predicted by the final adult dry weight and to a lesser extent by the proportion of weight lost in the transition from plerocercoid to adult, but not by the absolute weight loss.

Analysis of Variance↗

PubMed1991

Community control of Ascaris lumbricoides in rural Oyo State, Nigeria: mass, targeted and selective treatment with levamisole.

A study to compare effects of mass, targeted and selective chemotherapy with levamisole (Ketrax) as an action for the control of Ascaris lumbricoides was carried out in three communities in rural Oyo State, Nigeria. Selective treatment was applied in one village by treating the most heavily infected 20% of the inhabitants, targeted treatment in the second village involved children aged 2-15 years, while mass treatment was offered to all inhabitants excluding infants under 1 year and pregnant women in the third village. Recommended doses of levamisole were given in the villages, as described above, at 3-monthly intervals during a period of 1 year. Prevalence and intensity (epg) of A. lumbricoides infection were determined immediately before and 3 months after the period of intervention using a modified Kato-Katz technique. In the selective treatment village, no significant differences were found between the pre- and post-treatment egg counts (mean (+/- S.D.) epg 6776 +/- 10,791 versus 4259 +/- 10,909 respectively) of A. lumbricoides in the total population. In the targeted treatment village, significant differences were recorded in pre- and post-treatment egg counts for the total population (9057 +/- 15,797 versus 2579 +/- 6529) among the children alone (10,935 +/- 20,094 versus 992 +/- 3175) and among the untreated adults (7742 +/- 9782 versus 4561 +/- 8798). In the mass treatment village, significant differences in pre- and post-treatment egg count values were also recorded (11,907 +/- 17,220 versus 1489 +/- 5165). The intensity of Trichuris trichiura and hookworm infections among the villagers before and after intervention were not observed to have changed significantly regardless of selective, targeted or mass treatment.

Adolescent↗

PubMed1991

Influence of host strain and helminth isolate on the first phase of the relationship between rats and Moniliformis moniliformis (Acanthocephala).

Eleven trials, involving 440 rats bred from 3 laboratory strains and worms from 4 isolates of Moniliformis moniliformis, were carried out with each rat receiving an oral dose of 15 cystacanths. The results showed that the infectivity of the cystacanths was not affected by their age (range 55-194 days) or by their density per cockroach during development (16.1-88.6 cystacanths per cockroach). The numbers of worms per rat recovered at 35 days postinfection (p.i.) were shown to be related to rat strain, with highly inbred strains (PVG and F344) being more supportive of numbers of worms than an outbred Wistar strain. There was no evidence to suggest that the sex of the rats had any influence on the numbers of worms recovered at 35 days p.i. Evidence was obtained to suggest that smaller (younger) rats are likely to support more worms on average than larger (older) rats. There was no evidence of any relationship between worm weight and numbers of worms present per rat on day 35 p.i. Generally, rat strain had little effect on the dry weight (growth) of male M. moniliformis, in contrast to observations made for female worms. The greatest range of worm weights was observed from the recent isolate of the worm (1982) as compared with the well established isolate (1956) and the rats that supported most worms differed from those that harbored the largest worms. Rat sex was not observed to be associated with worm weight. The frequency distributions of numbers of M. moniliformis per rat were not described readily by the negative binomial distribution.

Analysis of Variance↗

PubMed1991

The occurrence of Centrorhynchus (Acanthocephala) in shrews (Sorex araneus and Sorex minutus) in the United Kingdom.

Encysted acanthocephalans belonging to the genus Centrorhynchus were found in the body cavities of Sorex araneus (common shrew) and Sorex minutus (pygmy shrew) from Boxworth, Cambridgeshire, U.K. Fifty percent of the male S. araneus and 67% of the male S. minutus examined were found to be infected, with the mean intensity (+/-SD) being 54.3 +/- 91.3 and 14.7 +/- 18.4, respectively. The species of Centrorhynchus in the shrews may be Centrorhynchus aluconis, which is distributed widely in tawny owls, Strix aluco, in the United Kingdom. Shrews appear to serve as paratenic hosts for C. aluconis.

Acanthocephala↗

PubMed1989

The epidemiology of Ascaris lumbricoides and other soil-transmitted helminths in primary school children from Ile-Ife, Nigeria.

An epidemiological survey of intestinal helminthiases was conducted on 766 primary school children aged 5-16 years from Ile-Ife, Nigeria. On the basis of stool examinations, the prevalence of Ascaris lumbricoides, Trichuris trichiura, hookworm and Strongyloides stercoralis was 88.5, 84.5, 33.1 and 3% respectively. Intensity of infection was measured indirectly by egg counts for each species of helminth and also by counting worms passed after chemotherapy in the case of A. lumbricoides. The influence of host age and sex on infection levels was assessed. Relationships between the intensities of A. lumbricoides, T. trichiura and hookworm in individual children were identified. After anthelmintic treatment with levamisole, the frequency distribution of A. lumbricoides per host and the relationship between parasite fecundity and worm burden were investigated. Reinfection patterns of A. lumbricoides were assessed at two 6-monthly intervals and even within the narrow age range described, differences were found. In addition, evidence was obtained for predisposition of individuals to heavy or light infection with A. lumbricoides.

Adolescent↗

PubMed1989

Soil-transmitted helminth infections in school children from Cocle Province, Republic of Panama.

A survey was carried out to determine values for the prevalence and intensity of infection of intestinal helminths in children living in Cocle Province, Republic of Panama. The data set consisted of the results of microscopic examinations (modified Kato Katz technique) of stool samples collected in November 1987 from 661 children attending primary schools in 4 communities in the province. The overall prevalences of Ascaris lumbricoides, hookworm and Trichuris trichiura infections were found to be 18.2, 12.0 and 27.5% respectively. There were significant differences between the infection prevalence values for children attending the different schools, but not with respect to age or sex. Positive associations were detected between particular pairs of infections and these were most evident when Trichuris trichiura was involved. The data revealed evidence of a positive association between siblings at one school only for each helminth infection. There was extreme variation in the values for intensity of infection (20-126180 epg for A. lumbricoides). Highly significant, and unexplained, differences were observed in the intensity of A. lumbricoides infection by primary school; this finding did not apply to hookworm or T. trichiura. The analysis also revealed that children heavily infected with A. lumbricoides were also likely to be heavily infected with T. trichiura. Comparisons with the results of surveys carried out in Cocle Province in 1926 and 1974 indicate that these infections are declining in this region of Panama.

Analysis of Variance↗

PubMed1988

The prevalence of Ascariasis.

The common roundworm, Ascaris lumbricoides, is probably the most prevalent human intestinal helminth. Previous estimates of world prevalence range from around 650 million to 1000 million. By a detailed literature search, David Crompton now confirms the upper figure - estimating a world prevalence of 1008 million representing about 22% of the world population. The infection is known from 153 out of 218 recognized countries.

Journal Article↗

PubMed1988

Intestinal helminthiases in relation to the socioeconomic environment of Panamanian children.

A cross-sectional investigation was made into ascariasis and nutritional status in Panamanian preschool children from October 1983 to July 1984. Within this framework, an analysis was undertaken of possible relationships between a range of intestinal helminthiases and the socioeconomic status of the participants. Attention was paid to caregiver's education, parental occupation, family earnings, quality of housing and sanitation in the assessment of socioeconomic status. On this basis, strong associations were established between the socioeconomic status of the children and infection with Ascaris lumbricoides, Trichuris trichiura and hookworm. In general, the prevalence of single and multiple helminth infections was significantly higher in children living in housing made of wood or bamboo than in those living in housing made of concrete blocks. The same pattern applied to levels of sanitation. Ascaris lumbricoides occurred more frequently in children of mothers with the least formal education and in children living in relatively crowded conditions. Evidence was also obtained to indicate that the intensity of the intestinal helminth infections was greater in the children from the poorer environment. Since children from poorer socioeconomic conditions might be more exposed to infective stages than those from a better environment, the possible role of socioeconomic factors in contributing to the predisposition of some individuals to harbour large worm burdens of intestinal helminths was briefly discussed.

Ascariasis↗

PubMed1988

A simple method for the oral transfer of Moniliformis moniliformis (Acanthocephala) between rats.

A technique is described whereby young adult Moniliformis moniliformis, aged up to 7 days, can be transferred via the oral route from one rat to another. The method is dependent on giving the recipient rats a dose of Cimetidine (0.25 ml/250 g body weight of a solution containing 950 mg/ml) 1 h before transfer. Cimetidine functions as an H2-receptor antagonist and gastric acid secretion in the rat is inhibited temporarily. The technique does not appear to interfere with the reproductive biology of the parasite.

Acanthocephala↗

PubMed1988

Evidence for post-cyclic transmission in the life-history of Neoechinorhynchus rutili (Acanthocephala).

Field observations at one site on brown trout (Salmo trutta) and three-spined sticklebacks (Gasterosteus aculeatus) concurrently infected with mature Neoechinorhynchus rutili, together with the knowledge that large trout can be piscivorous in habit led to the proposition that the post-cyclic transmission of N. rutili may occur between these fish species. This route of transmission has been suggested for a number of acanthocephalan species. A laboratory experiment was conducted and it was demonstrated that uninfected rainbow trout (Salmo gairdneri) can acquire a N. rutili infection as a result of feeding on sticklebacks already carrying established worms in their intestines. This finding may help to explain how N. rutili is found in a wide range of fish definitive hosts throughout the northern holarctic region. More generally this example provides further evidence of the flexibility within acanthocephalan life-history patterns.

Acanthocephala↗

PubMed1987

How much Ascariasis is there in Africa?

What is the real burden of parasitic infections? How many people, for example, are infected with the common roundworm Ascaris lumbricoides-usually cited as'number one' in the 'league table' of human parasite prevalence? Extrapolations are often made from figures for helminth infection published in 1947 by Stoll. More recent estimates suggest almost unbelievable numbers of oscoriosis cases - about 1000 million people representing about one quarter of the world population. Such figures are important because they contribute to the perennial debate about: allocation o f scarce health resources in affected countries to infections of greatest public health importance. But where do such figures come from? In this article, David Crompton and Jim Tulley report on their appraisal of Ascaris prevalence data for Africa. Their figures were used to compile the geographic histogram on this month's cover.

Journal Article↗