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PubMed1985

Hymenolepis diminuta: a comparison between young developing, and small, destrobilated worms in the rat intestine.

Newly in vitro excysted tapeworms of Hymenolepis diminuta (Cestoda, Cyclophyllidea), 1- to 3-day-old worms and destrobilated worms from rat intestines were investigated by means of light microscopy (LM) and scanning electron microscopy (SEM). It was found that the scolex of 1- and 2-day-old worms had shallow suckers with smooth brims, while 3-day-old and older worms, including destrobilated worms, had deep suckers with puckered brims. The posterior end of 1- and 2-day-old worms had a central cone-shaped structure not present in 3-day-old and older, or destrobilated worms. The repairing of the posterior end and the protonephridial system after excystation or destrobilation was much the same. Tissue remnants moved into the centre of the posterior end, resulting in an indentation with a pore to the exterior. The indentation and its pore became connected to the emptying canals of the protonephridial system, i.e. they developed into the excretory bladder and pore respectively.

Aging↗

PubMed1992

The expulsion of Echinostoma trivolvis (Trematoda) from ICR mice: scanning electron microscopy of the worms.

Echinostoma trivolvis adults are rejected from ICR mice within 3 weeks postinfection (p.i.) but are retained in golden hamsters for greater than 15 weeks. The present study used scanning electron microscopy (SEM) to examine worm topography in ICR mice, particularly that of the collar spines, and to correlate worm loss with tegumentary changes. The topography of the worm in ICR mice was similar to that observed in previous studies on this echinostome in domestic chick embryos, chickens, and golden hamsters. Observations were made on the pattern of collar spines in 115 worms from ICR mice at 3-14 days p.i. All worms examined at 3 days exhibited extended spines, whereas about 70% of the worms examined at 14 days displayed retracted or missing spines. Eight worms from golden hamsters examined at 14 days p.i. showed extended collar spines. The retraction or loss of collar spines may play a role in the expulsion of E. trivolvis from ICR mice.

Animals↗

PubMed1995

Relationship of blood loss to worm numbers, biomass and egg production in Haemonchus infected sheep.

Chromium51 labelled erythrocytes were used to measure blood loss in sheep infected with either H. contortus, H. placei or the F1 of their reciprocal cross hybrids (H. contortus males x H. placei females = CXP, H. placei males x H. contortus females = PXC). CXP consisted of sterile males and semi-sterile females and sheep infected with this hybrid had nil egg counts; while PXC consisted of semi-sterile males and females and their hosts had some eggs in their faeces. Immediately after their blood loss was estimated the sheep were killed and their worms counted. One hundred male and 100 female worms from each sheep were dried at 60 degrees C overnight and then weighed to give an estimate of the biomass in each infection. Total daily egg production was calculated from egg counts made on 3 random 2 g samples from the 24 h faecal collection. The relationship of the log blood loss to log worm number, to log biomass of infection in each sheep and to log total egg production in the parental species was linear. Biomass was no better an estimator of blood loss than was worm number. There was no improvement in the estimation of blood loss by regressing the male and female worms separately. In all of the analyses, there was no improvement by regressing H. contortus and H. placei or their hybrids separately. It appeared that egg production was not a major factor in the requirement for blood by Haemonchus. The size of individual female worms was negatively correlated with the number of worms in the infection.(ABSTRACT TRUNCATED AT 250 WORDS)

Anemia↗

PubMed1995

Experimental Oesophagostomum dentatum infection in the pig: worm populations resulting from single infections with three doses of larvae.

This report describes the effect of different dose levels of infection upon worm burdens and development and fecundity of the parasites. Three groups each of 40, 9-week-old, helminth naive pigs were inoculated once with either 2000 (group A), 20,000 (group B), or 200,000 (group C) infective third stage larvae of Oesophagostomum dentatum. Subgroups of 5 pigs from each major group were killed 3, 6, 11, 14, 18, 25, 34 and 47 days post inoculation (p.i.) and the large intestinal worm burdens were determined. Faecal egg counts were determined at frequent intervals after day 13 p.i. There were no overt clinical signs of gastrointestinal helminthosis during the experiment. Faecal egg counts became positive in groups A and B at around day 19 p.i., whereas most pigs in the high dose group C did not have positive egg counts until day 27-33 p.i. and some pigs remained with zero egg counts until the end of the study. Throughout the experiment the worm populations in group C consisted mainly of immature larval stages, while those in groups A and B were predominantly adult stages after days 14-18. Adult worms from the low dose group A were significantly longer than those from group C. At high population densities, stunted development of worms and reduced fecundity among female worms were found. Furthermore, there was a tendency for the distribution of the worms within the intestine to be altered with increasing population size.

Animals↗

PubMed1987

Necator americanus in neonatally infected hamsters. The time-course of infection and antibody response to the surface antigens of L4 and adult worms.

Neonatal hamsters were infected with a hamster-adapted strain of Necator americanus, and the time-course of infection was followed by worm and faecal egg counts. Parasite eggs were first recorded during the 6th week of infection, increasing rapidly thereafter to peak in weeks 7-10. Male hamsters excreted more eggs than females, but both sexes were equally susceptible to infection and harboured comparable worm burdens. Faecal egg counts declined from week 10 onwards and this was associated with a loss of worms from animals with heavy infections. Low level infections were stable over the first 114 d of infection but worm fecundity nevertheless still declined over this period. Both hamster sexes responded similarly to surface antigens on adult worms, the antibody levels rising from week 5 onwards to reach a plateau in weeks 6-7, which persisted until the experiments were terminated. The major antigens recognised on the surface of adult worms had molecular masses corresponding to 25 kDa, 32 kDa, a doublet with the heaviest polypeptide resolving at 46 kDa, and a triplet with the heaviest at 67 and 93kDa. In contrast L4 had only 2 major cuticular antigens resolving at 41 and 93kDa. The 93kDa molecule on L4 and adult worms may be antigenically related.

Animals↗

PubMedDate not supplied

Lack of effect of ivermectin on prepatent guinea-worm: a single-blind, placebo-controlled trial.

The effect of ivermectin on prepatent guinea-worm was tested in a single-blind placebo-controlled trial; 400 adults were randomly allocated to a single dose of ivermectin (150 micrograms/kg) or placebo. Fifty-four of the 385 participants who were followed for 15 months developed a total of 69 emergent guinea-worms. There was no significant difference in the proportion of persons with emergent guinea-worms between the 2 treatment groups; 58% appeared in males. 80% of emergent guinea-worms were located below the knee. Migration of guinea-worms in the tissues was not affected. It is concluded that ivermectin has no effect on prepatent guinea-worms nor does it disturb their migration pattern. No adverse reaction to treatment was seen. It appears that ivermectin can be used safely as mass chemotherapy against onchocerciasis and lymphatic filariasis in areas where guinea-worm is also endemic.

Adolescent↗

PubMed1989

The relation between the natural worm burden of steers and the faecal egg count differentiated to species.

The relation between the faecal egg count and the worm burden was investigated in 104 steers of three breeds, 9-24 months of age, which were subjected to natural infection with nematode larvae from pasture at The National Cattle Breeding Station near Rockhampton in central Queensland. The worm species found were Cooperia spp., Haemonchus placei, Trichostrongylus axei, Oesophagostomum radiatum and small numbers of Bunostumum phlebotumum. The faecal egg count was found to be a reliable measure of the size of the worm burden. Steers slaughtered at 24 months of age had 90% fewer worms and 96% fewer eggs g-1 faeces (P less than 0.001) than those slaughtered at 9 months of age. Adjusted for age, the estimated faecal egg count increased 14 times (95% confidence limits 7.2, 35) for each 10-fold increase in estimated worm numbers. The proportion of each species of larvae obtained from faecal culture (larval differential count) was related to the composition of the worm burden as measured by the proportion of worms in selected maturity categories and in selected length categories for each species (P less than 0.001).

Analysis of Variance↗

PubMed1996

Nematode burdens and immunological responses following natural challenge in Romney lambs selectively bred for low or high faecal worm egg count.

Breeding lines of Romney sheep, selected as lambs for consistently low or high faecal nematode egg count (FEC) following periods of natural challenge, have been maintained at Wallaceville for some years. In order to determine the extent to which FECs in low and high genotypes reflected their ability to resist the establishment of gastro-intestinal nematode burdens, we investigated the infection status and immune responses in 8- to 9-month-old progeny of selected rams from low and high FEC breeding lines following a period of grazing without anthelmintic treatment in autumn/early winter. In each of the 2 years of the study, outcross male progeny of the two lowest FEC (LFEC) (i.e. most 'resistant') and two highest FEC (HFEC) (i.e. most 'susceptible') rams from the divergent lines were slaughtered shortly after autumn/early winter FECs had been analysed. Post-mortem worm counts and examination of intestinal histology were then undertaken. Blood samples collected before slaughter in the second year of the study were assayed to measure serum levels of Trichostrongylus colubriformis-specific antibody and immunoglobulins (IgG1 and IgM), and numbers of circulating eosinophils. Overall, correlations between pre-slaughter FEC and total trichostrongyle burdens in the lambs proved to be very high (0.91 and 0.85, respectively, for the 2 years studied). In the first year, LFEC lambs, which were shedding only 28.6% as many strongyle eggs as their HFEC counterparts at slaughter, were found to harbour 37.6% as many adult trichostrongyle worms, while in the second year, LFEC lambs, which were shedding 16.1% as many strongyle eggs as their HFEC counterparts at slaughter, were found to harbour 33.5% as many adult trichostrongyle worms. Results, particularly in the second year, confirmed that significantly fewer worms of most of the important abomasal and small intestinal nematode species which infest lambs in New Zealand (i.e. Haemonchus contortus, Ostertagia circumcincta, Cooperia curticei, Nematodirus spathiger, T. colubriformis, and Trichostrongylus vitrinus) had established in the LFEC genotypes than in their HFEC counterparts. In addition, in utero egg counts of female intestinal Trichostrongylus spp. were significantly lower in LFEC lambs than in their HFEC counterparts, indicating a reduction in fecundity of those worms which did establish. There was also some evidence of an effect of host response on the developmental composition of burdens in the case of some worm species. In relation to host responses, numbers of globule leucocytes/mucosal mast cells in the intestinal mucosa were significantly higher (P < 0.01) in LFEC lambs than in HFEC lambs in both years of the study. Numbers of connective tissue type mast cells and eosinophils in the intestinal mucosa were also significantly higher in LFEC lambs but only in the second year of the study (P < 0.01 and P < 0.05, respectively). Numbers of circulating eosinophils did not differ significantly between the genotypes. T. colubriformis-specific antibodies, IgG1 and IgM to both L3 and adult worm antigens were all significantly higher (P < 0.01 or P < 0.05) in LFEC lambs than in HFEC lambs.

Abattoirs↗

PubMed1986

Transfer of [14C] cholesterol and its metabolites between adult male and female worms of Schistosoma mansoni.

Adult male and female worms of Schistosoma mansoni are able to incorporate [14C]cholesterol and convert it into several metabolites. Schistosomula on the other hand cannot convert the incorporated cholesterol. Male worms are able to transfer the [14C]cholesterol and labelled metabolites to female worms but labelled female worms can transfer cholesterol but are unable to transfer the conversion products of cholesterol to male worms. Uptake by female worms of labelled products shed by male worms seems to occur more efficiently in the presence of serum than in its absence.

Animals↗

PubMed2005

Do tubificid worms influence the fate of organic matter and pollutants in stormwater sediments?

In urban area, management of stormwater leads to the accumulation of polluted sediments at the water-sediment interface of various aquatic ecosystems. In many cases, these sediments are colonised by dense populations of tubificid worms. However, the influence of tubificid worms on the fate of stormwater sediments has never been tackled. The aim of this study was to measure in sediment columns the influence of tubificid worms on sediment reworking, organic matter processing (O(2) uptake and release of NH(4)(+), NO(3)(-), PO(4)(3-), and dissolved organic carbon), release of hydrocarbons and heavy metals, and microbial characteristics. Results showed that tubificid worms increased the release of NH(4)(+), PO(4)(3-), and dissolved organic carbon by 2-, 4-, and 3-fold, respectively. O(2) uptake also increased by more than 35% due to tubificid activity. The increase in the percentages of active bacteria and hydrolytic activity in the presence of worms indicated that the higher sediment respiration was caused by the stimulation of microbial communities. A reduction of the number of sulphate-reducing bacteria in the uppermost layers of the sediment was attributed to the penetration of O(2) due to worm activity. These significant effects of tubificid worms were probably linked to the dense network of burrows, which enhanced the exchange surface between the water column and the sediment. No release of heavy metals and hydrocarbons to the water phase was detected in the sediment columns. Understanding the fate and effect of organic stormwater sediments in the natural environment requires the integration of the role of bioturbation in urban pollution studies.

Animals↗

PubMed2005

Brugia malayi: effects of gamma radiation on adult worms and their intracellular Wolbachia bacteria.

Prior studies have shown that intracellular Wolbachia endobacteria are necessary for the normal development, reproduction, and survival of filarial nematodes. The purpose of this study was to examine effects of gamma radiation on Wolbachia and reproduction in Brugia malayi adult worms. Worms were exposed to 0, 10, 25, 45, 75, and 105 krad of gamma radiation from a 137cesium source and cultured in vitro for 10 days. Irradiation reduced production of microfilariae in a dose-dependent manner. Embryograms of irradiated female worms showed dose-related abnormalities with arrested development at the early embryo stage. Irradiation reduced the viability of adult worms in a dose-dependent manner, but no lethal effect was observed. Electron microscopy studies showed that irradiation cleared Wolbachia from worm tissues. Real-time polymerase chain reaction studies demonstrated greatly reduced Wolbachia DNA in irradiated worms. These effects are essentially the same as those observed in adult worms treated with doxycycline. These studies suggest that effects of irradiation on reproduction in Brugia malayi may be caused by effects of irradiation on Wolbachia.

Aedes↗

PubMed2004

Dirofilaria immitis: worm burden and pulmonary artery proliferation in dogs from Michigan (United States).

Despite the ability to prevent heartworm disease, infection with Dirofilaria immitis continues to be a major problem for domestic dogs. To determine worm burden in heartworm-positive dogs from three county animal shelters in the state of Michigan in the United States and to assess the relationship between gross intimal proliferation and worm burden, necropsy was done on 176 heartworm-positive dogs. Adult heartworms were found in the heart and pulmonary artery of 170 of the 176 (96.6%) dogs examined. Mean worm burden was 14 +/- 13 (range 0-85). Fifty-nine percent of dogs had < or =10 heartworms. In contrast, 52% of dogs in a published report from the southern US (Florida) had worm burdens >10 [C.H. Courtney, Q.Y. Zeng, The structure of heartworm populations in dogs and cats in Florida, in: Proceedings of the American Heartworm Symposium, 1989]. These data suggest that mean worm burden in northern areas may be < or = that in warmer areas. Also, since diagnostic tests are less sensitive with lower worm burdens, diagnosis of heartworm infection in Michigan and other surrounding more northern states may be a greater challenge than in areas with higher worm burdens.

Animals↗

PubMed2001

Selection of different genotype larvae and adult worms for anthelmintic resistance by persistent and short-acting avermectin/milbemycins.

To understand the factors that influence selection for anthelmintic resistance, it is necessary to examine the impact of drug treatment, particularly persistent drugs, on all phases of the worm life cycle. The efficacy of various avermectin/milbemycin anthelmintics was determined against resident worms, incoming larvae (L3) and development of eggs in faecal culture. Homozygote-resistant and maternal and paternal F1-heterozygote genotypes of Haemonchus contortus were used to infect sheep before or after treatment with ivermectin (IVM) oral, IVM capsule, moxidectin (MOX) oral or MOX injectable. Total worm count and quantitative larval culture were used to determine efficacy against parasitic and free-living stages, respectively. Selection for resistance by IVM capsules occurred at the adult and L3 stages because of poor efficacy against these stages for all resistant genotypes. However, the selective advantage of these surviving worms was reduced due to the low development of their eggs to L3 in faecal culture. For MOX, selection for resistance predominantly occurred after treatment because of high efficacy against resident adult worms of all resistant genotypes but poor efficacy against resistant L3 ingested after drug administration. The results indicated no evidence of sex-linked inheritance for IVM resistance. Mean IVM efficacies against homozygous and heterozygous resistant adult worms were not different, and IVM capsule efficacy against incoming L3 was approximately 70% for all resistant genotypes, consistent with a dominant trait. MOX was highly effective against adults of all resistant genotypes and approximately 76% effective against incoming L3 regardless of resistance genotype, also consistent with a dominant trait. These results will enable the impact of persistent drugs on worm control and anthelmintic resistance to be estimated. The results indicate that IVM capsules should not be used in populations where avermectin/milbemycin resistance is present.

Administration, Oral↗

PubMed1999

The curvilinear relationship between worm length and fecundity of Teladorsagia circumcincta.

The variation among sheep in fecundity of Teladorsagia (Ostertagia) circumcincta was estimated by dividing the faecal egg count by the worm number following deliberate infection of mature Scottish Blackface lambs. Fecundity was skewed and ranged from 0 to 350 eggs per worm per day. Most animals had relatively low worm fecundities, but a small number of individuals had relatively high worm fecundities. However, as fecundity is a ratio of two imprecise estimates, extreme values may be statistical artefacts. Following both deliberate and natural infection, differences in worm fecundity were associated with differences in adult female worm length. In both infections, fecundity varied with worm length to the power 0.4. This relationship should assist the measurement of fecundity in studies of host immunity, in epidemiological modelling and in estimating the influence of density-dependent relationships.

Animals↗

PubMed1998

Guinea worm disease--a chance for successful eradication in the Volta Region, Ghana.

A guinea worm eradication program in two farming communities in the Akatsi District in the Volta region of Ghana was initially threatened by failure to apply simple preventive practices. Persistent monitoring and education on the use of locally supplied, inexpensive materials for water filtration has turned the program around. In March 1996, the Volta rural water supply and sanitation (VRWSS) project commissioned a guinea worm prevalence and knowledge, attitude and practice (KAP) study to collect baseline prevalence data. This study revealed some of the factors that contributed to the persistent high prevalence of guinea worm in the two communities. The community's only source of potable drinking water was irrigation dams which also served as the source of guinea worm infection. The Last quarterly report stated that guinea worm cases had been reduced from 62 to 5 in the two communities. Lessons learnt from Avega and Avevi will be extended to other guinea worm endemic communities that have registered with the project in the region. The prospect of total eradication of guinea worm in the region now exists.

Dracunculiasis↗

PubMed2003

Worm control practices and anthelmintic usage in traditional and dairy cattle farms in the southern highlands of Tanzania.

Worm control practices and anthelmintic usage in 177 cattle farms in Iringa district in the southern highlands of Tanzania was determined through a questionnaire survey. A total of 76 traditional, 92 small-scale dairy and 9 large-scale dairy cattle farms were included in the survey. Results indicated that 87.7% traditional, 97.8% small-scale dairy and 100% large-scale farmers relied solely on the use of anthelmintics, 2.7% traditional farmers used traditional medicines while 9.6% traditional farmers had not any form of worm control practice. Worm infection was ranked the second most important constraint of productivity in cattle in the three production systems. Most farms (57.6% traditional, 35.8% small-scale dairy, 66.7% large-scale dairy) used anthelmintics with a combination of levamisole and oxyclozanide. Benzimidazoles were used only in traditional (25.4%) and small-scale dairy (32.1%) farms while nitroxynil (Trodax) was mostly used in large-scale dairy farms (33.3%). Generally, 40% of farmers treated three or four times a year and the frequency in some farms was surprisingly high for resource poor small-scale farmers. The frequency of anthelmintic treatment was mostly the same regardless of the management system. Treatments in most farms depended on availability of money and drugs and not the epidemiology of parasites. A significant proportion (46.3%, P=0.007) of farmers especially in rural areas failed to follow their pre-planned treatment schedules due to lack of money (86%) and unavailability of drugs (6.6%). Many farmers (58.9%) had used the same type of anthelmintic for four or more consecutive years and 85.3% of them would continue with the same anthelmintic. Farmers in all management systems mostly purchased anthelmintics from private veterinary drug shops and about 43% traditional and 33.3% small-scale dairy farmers mostly in rural areas obtained anthelmintics from village extension officers. Despite the fact that all farmers were aware of worm infection and the associated signs in cattle, 42.5% had poor knowledge on the source of worm infection. Small-scale dairy farmers allowed only a 1-day withdraw period for milk regardless of the type of anthelmintic used and there was no milk and slaughter clearance in traditional farms. It was concluded from this study that worm control in Iringa faces serious constrains and that education of farmers and farm hands is not adequate. Moreover, poor quality control and high price of potent anthelmintics, few extension workers, low income and low education among farmers contributed significantly to erratic worm control practices and anthelmintic usage in peri-urban and rural areas.

Animals↗

PubMed1996

Monthly fluctuations of worm burdens and hypobiosis of gastrointestinal nematodes of calves in extensive management systems in the Pyrenees (Spain).

Monthly fluctuations of worm burdens and arrested development of gastrointestinal nematodes in cattle from a mountainous region of Spain were studied. Fourteen previously helminth-naive calves grazed together with a herd of 120 cattle from May to November following the traditional extensive grazing system used in mountainous regions of Spain (permanent calves). Each month, throughout the grazing season, two helminth-naive calves (tracer calves) were added to the herd and allowed to graze for 4 weeks. Every 2 weeks, throughout the grazing period, faecal and blood samples from the permanent calves, and pasture grass samples for larval recovery were collected. Every 4 weeks, throughout the grazing period, two tracer and two permanent calves were removed from the herd and housed on concrete for 2 weeks before being slaughtered. The nematode parasite species identified from the animals were: Ostertagia ostertagi, O. lyrata, Teladorsagia circumcincta, Trichostrongylus axei, Cooperia oncophora, Trichostrongylus longispicularis, Capillaria bovis, Nematodirus helvetianus, Oesophagostomum radiatum, Chabertia ovina and Trichuris spp. O. ostertagi was the predominant species, followed by C. oncophora and T. axei. The highest numbers of worms recovered from the tracer calves were observed in May, June, September and November with average worm burdens of 4050, 3775, 2775 and 2825, respectively. These dates corresponded with 2 months of spring grazing in areas below 1000 m (May-June), the last month of grazing in areas higher than 1000 m (September), and the last month of autumn grazing in areas below 1000 m (November), respectively. The highest total worm burden (8000 worms per animal) was observed in the permanent calves in June after 2 months of grazing below 1000 m. The average total worm burden in the permanent calves during the study was 5825 worms per animal. As in other cool temperate regions of the Northern hemisphere, the highest percentage of larval inhibition was observed in autumn, with maximum levels of 63.4% for Ostertagia spp. and 89.3% for Cooperia oncophora. Similar inhibition levels were observed in parasites from both tracer and permanent calves, indicating that previous exposure was not the primary cause of larval inhibition.

Animal Husbandry↗

PubMed2001

Lack of interferon-gamma confers impaired neutrophil granulocyte function and imparts prolonged survival of adult filarial worms in murine filariasis.

We investigated the role of IFN-gamma in host defense during murine filariasis. Using the fully permissive infection of BALB/c mice with the rodent filaria Litomosoides sigmodontis, we show that interferon (IFN)-gamma is essential for encapsulation of adult filarial worms in inflammatory nodules and for normal worm clearance. IFN-gamma knockout (KO) mice had only one third of the nodules of wild-type mice but displayed a more than twofold increase in worm burden and increased microfilaremia. Neutrophil granulocytes, but not macrophages or eosinophils, appear to directly control worm load and nodule formation. Neutrophils, which we showed earlier to be essential for the encapsulation process in the thoracic cavity, where the worms reside, were diminished at this location in IFN-gamma KO compared to wild-type mice; they also displayed strongly reduced chemotactic and phagocytic activity compared to neutrophils of controls. This argues for a distinct defect in neutrophil activation accounting for the low formation of inflammatory nodules. Tumor necrosis factor-alpha, a major neutrophil-activating cytokine expressed by macrophages in the thoracic cavity around the worms, was highly induced in wild-type but absent in KO mice. Diminished activation of neutrophils seems to be a general hallmark of IFN-gamma KO mice, since neutrophils from uninfected KO mice also showed a reduction in chemotactic and phagocytic activity when induced by casein. In conclusion, these data are the first to define an IFN-gamma-dependent immune effector mechanism in murine filarial infection, i.e. neutrophil-mediated control of the adult worm load.

Animals↗