Population dynamics of the parasitic stages of Oesophagostomum dentatum in pigs in single and trickle infections

A mathematical model was developed to describe the dynamics of the parasitic stages of Oesophagostomum dentatum in pigs. An immigration-death model with constant establishment, development and death rates was fitted to L3, L4 and adult worm burdens observed in a single-infection experiment. Female worm length was modelled by a function of worm age and total worm burden, while worm egg production (eggs per gram faeces per female worm) was modelled by a function of worm age and worm length. The model was then used to predict worm burdens observed in a trickle-infection experiment. The predicted worm burdens were much higher than those observed, suggesting that worm death rates were higher during the trickle infection. After increasing worm death rates to fit the observed worm burdens, female worm lengths and egg production in the trickle infection were predicted. At the medium- and high-dose rates, predicted worm lengths and, thus, egg production were lower than observed, while at the low-dose rate predicted egg production was too high. It appeared that in the trickle infections, total worm burden had less influence on observed female worm length and egg production than in the single infections. The results suggest that the demography of O. dentatum in pigs differs between single and trickle infections.     

Schistosoma mansoni oviposition in vitro reflects worm fecundity in vivo: individual-, parasite age- and host-dependent variations

In an attempt to determine whether in vitro oviposition of adult S. mansoni reflects the fecundity status of worms in vivo, Mongolian gerbils and ICR, BALB/c and SCID mice were infected with about 100 cercariae and examined on an individual basis, 5-12 weeks later, for worm burden, counts of eggs in liver and small intestine, and for the rate of egg deposition of ex-vivo female worms cultured in vitro, singly or in pairs, over a 3-5 day incubation period. The percentage of egg-laying female worms and the number of eggs laid/female after 3 days in culture showed, like worm fecundity in vivo, wide inter-worm variability, especially in 5-, 6- and 12-week-old worms; varied significantly with the age of the parasite with a maximum level attained by worms of approximately 8 weeks of age; and differed in worms recovered from different host species and strains. The data taken together indicate that measuring the egg-producing ability of S. mansoni in vitro reflects the fecundity status of worms in vivo and additionally provides likely explanations for hitherto poorly understood findings on schistosome fecundity.     

The influence of high- and low-fibre diets on the activity of piperazine against Oesophagostomum spp. in pigs

An in vivo study evaluated the effect of diet on the efficacy of piperazine against nodular worms of pigs. Twenty pigs, later allocated into five groups, were each infected (and 37 days later re-infected) with 3000 infective larvae of a mixed isolate of Oesophagostomum dentatum and Oesophagostomum quadrispinulatum. Beginning on day 23 post infection (p.i.), pigs in groups 1 and 2 were fed a low-fibre diet consisting of 70% barley flour and 30% protein concentrate, while pigs in groups 3, 4 and 5 were fed a high-fibre diet consisting of 55% barley flour, 21% oat-husk meal and 24% protein concentrate. On day 42 p.i., pigs in groups 1 and 3 were orally dosed with 200 mg piperazine dihydrochloride (Ascarex D, 53%) per kg bodyweight, the recommended dose, while pigs in group 4 were given 100 mg kg-1. Groups 2 and 5 served as non-treated controls for the respective dietary regimens. Eight days after treatment, the pigs were slaughtered and worms recovered from the caecum and large intestine (divided into five sections) and counted. The mean worm count reduction (WCR) in group 1 (full-dose piperazine with low-fibre diet) was 89.8%, while the high-fibre diet in group 3 increased the WCR to 99.4%. In group 4, where the pigs were fed the high-fibre diet and treated with only 100 mg piperazine kg-1, the WCR was 90.9%, identical to the "low fibre" group 1 treated with twice this piperazine dose. There was a zero efficacy recorded against immature worms in all three treated groups. The high-fibre diet improved the efficacy of piperazine against more pathogenic and generally more tolerant O. quadrispinulatum to 99.2% compared with 84.3% at the low-fibre diet.     

Oesophagostomum spp. in pigs: resistance to reinfection

For a study on the occurrence of resistance to reinfection with porcine nodular worm species, pigs were infected twice weekly with 1,000 infective larvae (L3) of Oesophagostomum quadrispinulatum for 8 weeks. All pigs, including noninfected controls, were then treated with fenbendazole. At 10 days after treatment, all pigs received a single challenge inoculation of 5,000 L3 of either O. dentatum or O. quadrispinulatum, respectively. Pigs were slaughtered at 6 weeks after the challenge infection for determination of their worm burdens. The pigs trickle- and challenge-infected with O. quadrispinulatum had significantly lower egg excretion levels (P < 0.01) and worm burdens (P < 0.05) than challenge control pigs, thus indicating some degree of host immunity against the homologous challenge infection. No resistance to reinfection was evident for the heterologous challenge infection. This study elucidates further aspects of the interaction between nodular worm species in the pig.     

Fecundity of sealworm (Pseudoterranova decipiens) infecting grey seals (Halichoerus grypus) in the Gulf of St. Lawrence, Canada: lack of density-dependent effects

Uterine egg counts were determined by means of an electronic particle counter in individual female sealworm, Pseudoterranova decipiens (Nematoda: Ascaridoidea: Anisakidae) collected from grey seals (Halichoerus grypus) from Anticosti Island, northern Gulf of St. Lawrence, in August and September 1992. Mean number of eggs per female was 54,916.9 (+/- 51,866.4), with a maximum of 300,000. Egg counts were strongly correlated with worm length, and less so with host sex and age, sealworm sex ratio, and densities of Anisakis simplex and Phocascaris sp. No effect of sealworm density on worm egg counts was determined and competitive effects by Contracaecum osculatum on sealworm fecundity were not observed. Analyses demonstrated that variation in sealworm fecundity was greater among seal hosts within groups than between groups for host age and sex, density of sealworm, and density of C. osculatum. No evidence for density-dependent regulation of sealworm fecundity could be found. Variations in worm egg counts are attributed to individual host effects on worm growth and fecundity.     

Marked eosinophilia in interleukin-5 transgenic mice fails to prevent Trichinella spiralis infection

In order to study the role of eosinophils in the host defense against Trichinella spiralis infection, worm recovery after infection with T. spiralis was compared between interleukin-5 transgenic (IL-5 Tg) mice with a constant high level of peripheral eosinophils and nontransgenic C3H/HeN mice. No significant difference in the recovery of muscle larvae or adult worms in the small intestine, fecundity of female adult worms, or infectivity of newborn larvae was observed between nonimmunized C3H/HeN and IL-5 Tg mice or C3H/HeN and IL-5 Tg mice immunized with somatic antigen of T. spiralis. However, a significant difference was observed in the fecundity of female adult worms and recovery of muscle larvae between nonimmunized and immunized IL-5 Tg mice or C3H/HeN mice. These results demonstrate that having more eosinophils does not improve immunity against the various aspects of T. spiralis infection.     

Airway response of horses with COPD to dry powder inhalation of ipratropium bromide

At some stages of development, it is impossible to identify the porcine nodular worms Oesophagostomum dentatum and O. quadrispinulatum to the species level using morphological parameters. A molecular approach utilizing genetic markers in the second internal transcribed spacer (ITS-2) of ribosomal (r) DNA was developed to overcome this limitation. The ITS-2 sequence of each species was determined, and specific oligonucleotide primers were designed to regions of greatest sequence difference between the species. Utilizing these primers, rapid PCR procedures were developed for the specific amplification of DNA of O. dentatum or O. quadrispinulatum, which are now used routinely to monitor the purity of larval cultures and to confirm the identity of larvae derived from the intestine or faeces. The application of specific PCR has major implications for studying the population biology of nodular worms in the pig model.     

Ascending collaterals of cutaneous neurons in the fasciculus gracilis of the cat during peripheral nerve regeneration

The present investigation was undertaken to determine some morphological characteristics of Japanese strain of Schistosoma japonicum, the results are summarized as follows: (1) The pattern of testes in male worms can be divided into two types: the tandem (37.6%) and non-tandem (62.4%). (2) The number of testes varied from 1 to 13. The percentage of specimens with 7 testes was much higher than of others with both in tandem (70% against 30%) and non-tandem (86% against 14%) arrangement. (3) The unusual/irregular sets of testes including 2-3 additional sets were found in 158 (or 4.5%) of 3,498 male worms. Specimens with 7 testes in the unusual/irregular location numbered the highest (69.6%); the next with 8 (14.6%) and 6 (12%); and the lowest with 5 (3.8%). (4) Forty or 2.8% of 1,417 male worms were found to have 2-4 cecal loops. The cecal union located in 71-80% of worm bodys from the anterior end of male worm was found in highest number; the next in 61-70%; and the lowest in 51-60% and 81-90%. The location of united ceca in female worms was found all in the posterior part of body. (5) The ovary in all 125 females was located in the posterior portion of worm body except in 4 specimens. (6) The number of eggs in the uterus of female worms varied from 50 to 300. The mean number was 103.     

Cysteine protease inhibitors block schistosome hemoglobin degradation in vitro and decrease worm burden and egg production in vivo

Schistosome parasites utilize hemoglobin as a major protein source for their metabolism. Degradation of hemoglobin has been hypothesized to be mediated by both cysteine and aspartyl proteases secreted into the lumen of the parasite intestine. We now show that two distinct types of irreversible cysteine protease-specific inhibitors both arrest schistosome hemoglobin degradation in vitro. Arrest of hemoglobin degradation is followed by death of developing schistosomula 1 week later. Schistosome infected mice treated by a dose of 2 mg inhibitor per day for 1 week early in infection, and 2 weeks at the time of egg production, showed a significant reduction in worm burden, hepatomegaly, and the number of eggs produced per female worm. Histopathology showed a minimal immune response to those eggs which were produced, consistent with a delay in egg production relative to untreated infections. By tagging the inhibitor with biotin, specific cysteine protease targets were identified in extracts of schistosome worms.     

Exogenous estrogen may exacerbate thrombophilia, impair bone healing and contribute to development of chronic facial pain

Humoral and cellular responses to Schistosoma bovis antigens have been evaluated over a period of 11 weeks in mice exposed to S. bovis cercariae and data analysed in the context of the parasitic parameters (worm and egg loads) recorded at days 30, 60 and 80 of the ongoing infection. Results revealed a decrease of worm burden, particularly marked for female worms, between day 60 and day 80 of infection suggesting a higher susceptibility of female schistosomes to attrition mechanisms. The B-cell response, studied by measuring the production of different isotypes, was directed against different stage specific antigens, with a predominance of IgG1 antibodies associated with a significant increase of IgA and IgE antibodies after egg deposition. The T-cell response, assessed after in vitro stimulation of splenocytes, showed a predominant production of Th-2 cytokines (IL-4, IL-5 and IL-10) occurring after egg laying. Interestingly in contrast to S. mansoni infection the Th-2 polarization did not seem to be exclusively triggered by egg-associated antigens since significant amounts of IL-10 were produced after stimulation with adult worm antigen preparation (SWAP) before the beginning of egg deposition.     

Egg production capacity of Paragonimus pulmonalis in cats

In the present study, each of 43 cats was fed with a single metacercaria of Paragonimus pulmonalis and 2 cats (controls) with 2 metacercariae. They were killed 22-372 days postinfection. In the test group, 18 (41.9%) cats were infected, as well as the 2 cats in the control group. Among the 18 worms recovered from the test group, 9 found in the lungs were mature, whereas 5 mature and 4 immature worms were in the pleural cavity. Most eggs from worms encased in a cyst were passed in the feces. However, eggs from worms in the pleural cavity were only found on the lung surface and pleural cavity. Mature worms in cysts seemed to exhibit higher egg production capacity than those in the pleural cavity. Paired mature worms from a cyst laid more eggs than a single encysted mature worm in vitro at room temperature.     

The pipette aspiration applied to the local stiffness measurement of soft tissues

The prevalence and development of adult worms in the lungs of mice and gerbils infected with Schistosoma mansoni was investigated. All infected BALB/c mice harbored the schistosomes in their lungs at 10-12 weeks post-infection, showing the distinct relocation of adult worms to the lungs, from the hepatic portal system. The male and female flukes from lungs of BALB/c mice were significantly smaller than those from livers. The percentage of gravid females in lungs was considerably lower than that in the livers. The number of eggs recovered from lungs of BALB/c mice and gerbils having lung female worms, however, was higher than that from animals without lung females, indicating egg deposition of lung females. The number of eggs detected in the brains correlated well with the number of eggs from the lungs in BALB/c and ICR mice. Out of 119 infected gerbils at 8 weeks post-infection, only two animals had egg-emboli in the brain vessels, although many eggs embolized in the lungs of those animals. These data suggest that transfer of worms to the lungs from livers involves reduction of worm recovery from the portal circulation, and also pulmonary pathology of the disease.     

Strongyloides stercoralis: maintenance of exceedingly chronic infections

Two hypotheses were tested to identify the mechanism(s) by which chronic Strongyloides stercoralis infections are maintained in experimental dogs as a model to explain delayed onset recrudescence in humans. Investigations tested the hypotheses that chronic infections result from 1) periodic reactivation of third-stage larvae from a reservoir of dormant parasites outside the gastrointestinal tract or 2) the periodic rejuvenation of postreproductive female worms remaining from a previous infection, lodged in the mucosal crypts. Populations of parenteral larvae survived in mature experimentally infected female dogs for 66 days; individual worms survived for 88 days, but there was no evidence that these larvae re-established patent, adult worm infections. Late in these infections, female worms were present in greater than predicted numbers with no evidence that autoinfection had occurred, suggesting that some postreproductive worms were long-lived. In separate trials, long-lived spent females were once again capable of producing viable larvae when the host was treated with corticosteroids.     

Worm population characteristics and pathological changes in lambs after a single or trickle infection with Teladorsagia circumcincta

The regulation of the worm population and of its pathological effects was studied after a single or trickle infection with T. circumcincta. One hundred and twenty lambs, 60 Romanov and 60 Mérinos d'Arles, 3 months old, were distributed in four balanced groups: non-infected (G0), infected with 7000 L3 per animal once and slaughtered after 4 weeks (G14) or 8 weeks (G18), and infected 8 times and slaughtered after 8 weeks (G88). Parasitological, histological, haematological parameters and weight gains were recorded on each animal. Female and artificially nursed lambs had lower worm burdens and egg counts (epg) than males and naturally suckled lambs. No difference in parasitological parameters was seen between the two breeds, but Mérinos lambs infected once, had a higher increase in pepsinogen concentrations than Romanov lambs. In the infected animals, a significant proliferation of mast and eosinophil cells was observed in the abomasum wall. Serum pepsinogen concentrations were significantly higher 3 weeks p.i. and the weight gain was depressed during the first month p.i. The worm population was more numerous and younger in group G14 compared with G18 in which 24% of the worms had been expelled during the second month p.i. The female worms in G18 were longer and had more eggs in utero and higher egg output. After the trickle infection (G88) the take was reduced, female worms were longer with more eggs in vagina (pars ejectrix) and there was a higher variability in the number of eggs (compared with G18 data). The pepsinogen rise was smaller but no specific effect was seen on histological and haematological parameters.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cross reacting antibodies against keyhole limpet haemocyanin may interfere with the diagnostics of acute schistosomiasis

The number of individuals catching schistosomiasis has increased with the popularity of 'primitive tourism' in Africa. Highly immunogenic material originating from the intestine of intravascular adult schistosomes gives rise to an antibody response making possible early identification of infected individuals using serology. Antibodies against gut associated antigens (anti-GAA), detected by indirect immunofluorescence microscopy employing sections of adult worms as antigen may occur before the onset of egg production. In the present study we show that this well known schistosomiasis-specific anti-GAA staining reaction can be confused with a similar staining reaction with ducts of both male and female worms. Antibodies with duct reactivity were seen in sera both from schistosomiasis-patients and patients with some other invasive worm infections. Cross reactive anti-duct antibodies appear to have different specificity. One cross reactive antibody reacted with antigenic epitopes present in keyhole limpet haemocyanin (KLH). Anti-duct reactivity could be inhibited by absorption with KLH. This was most obvious in the trichinellosis patient sera.     

Factors influencing the development and carbohydrate metabolism of Echinococcus granulosus in dogs

Echinococcus granulosus adult worms, 35 days postinfection, were measured for dispersion in the intestines of 10 dogs, a range of morphological characters, and the excreted end products of carbohydrate catabolism following 4 hr incubation in vitro. Most worms were found in the proximal sections of the small intestine, but the pattern of dispersion differed between dogs. Worm development varied both between dogs and between different regions of the small intestine of individual dogs. Overall there was a high level of variability with no simple patterns. Worm metabolism was related to worm development and, also independently, to local population density within the intestine. Larger, more mature worms produced less lactate and, at higher densities, worms tended to produce more acetate and succinate (pathways with a higher energy yield than lactate) and less ethanol. Thus, both more developed worms and high population density are associated with a shift from cytosolic to mitochondrial metabolism. The variation between worm populations along the small intestine along with the observed variation between worm populations from sibling dogs infected with genetically identical parasites suggests that the local host environment has a significant effect on parasite development.     

Effect of hemodialysis on leukocyte adhesion receptor expression

Onchocerciasis is associated with blindness and gross skin changes, believed to be a consequence of the immune response to antigens released from the offspring of the female worm of Onchocerca volvulus, the microfilariae (mf). An effective microfilaricidal drug is now available which quickly reduces the mf burden without affecting the adult worm. There exist foci in onchocerciasis endemic areas where some of the patients have many mf in their skin but relatively few clinical symptoms. This state of hyposensitivity is believed to be due to immunosuppression. The aim of this study was to address the question of the basis of, and the effect of ivermectin treatment on this immunosuppression. Female adult worms of O. volvulus were used as whole or fractionated antigens to stimulate peripheral blood mononuclear cells. Microfilariae are found in the reproduction tract of the female worms, and thus an antigen preparation of the female adult O. volvulus contains both exclusive adult antigens as well as antigens from microfilariae. Cells were obtained from onchocerciasis patients, individuals of similar socio-economic status living in the same Ghanaian village, but who showed no parasitological or clinical evidence of onchocerciasis (exposed endemic controls), healthy Ghanaians living in areas where transmission of onchocerciasis does not seem to occur (non-exposed endemic controls) and unexposed healthy Swedish donors. As a group, cells from onchocerciasis patients proliferated to a lesser degree than cells from the exposed endemic control and the non-exposed endemic control groups to the whole worm antigen, whereas the phytohaemagglutinin (PHA) response was strongest in the patients. Proliferative responses of above 1000 ct/min to fractions of the worm extract were only evident in the cells from a few individuals in each of the various groups. However, 28 days following ivermectin treatment, cells from all onchocerciasis patients were able to mount significantly enhanced proliferation to a fraction of approximately 96 kD (fraction 3), while only four of nine of this group showed an increased response to the whole worm antigen. The proportional increase in the response to the whole organism in these individuals was of a much lower magnitude than the increased response to fraction 3. The O. volvulus antigen-specific immunosuppression observed in these onchocerciasis patients appears to be due to suppressive antigens which have the capacity to mask the potential response to selected antigens of O. volvulus, and ivermectin treatment possibly modulates the immune response, allowing for stepwise recognition of such antigens. Since ivermectin treatment kills only the microfilariae and not the adult worm, the putative suppressive antigens would be expected to be from the microfilariae.     

False-positive Ascaris suum egg counts in pigs

False-positive Ascaris suum egg counts in pig faeces are frequently observed under both experimental and natural conditions. Data from 12 experiments with A. suum infections in pigs were summarized and showed that the percentage of false-positive faecal samples ranged from 4 to 36%. False-positive egg count values varied greatly between pigs and experiments (range 20-1060 eggs per gram faeces). Indoor experiments with pigs housed groupwise in pens generally produced more and higher false-positive egg counts, which may reflect differences in surface area and hence exposure to infective eggs, compared with pasture experiments. The positive predictive value (the number of pigs diagnosed positive by faecal sample that actually harboured worms) was low for indoor experiments (45%) compared with pasture experiments (89%). Differences in design for indoor experiments, such as floor type and use of bedding material, did not influence the positive predictive value (44-47%). A positive correlation was found (r = 0.56, P < 0.05) between faecal egg counts of true-positive and false-positive pigs that were penned together. The results of this survey strongly support previous suggestions that false-positive A. suum egg counts in pigs are the result of coprophagia in indoor experiments and coprophagia/geophagia in pasture experiments. False-positive A. suum egg counts in pig faeces may vary greatly in prevalence and magnitude, and depend in part on management/housing factors.     

In vitro dog detrusor strip contractile responses and calcium ion activity

An attempt was made to immunise lambs by the intra-muscular injection of concentrated metabolites obtained from the in vitro culture of Ostertagia circumcincta, by the oral administration of lyophilised metabolites or by the subcutaneous injection of living third, fourth and fifth stage worms grown in vitro. Protection appeared to have been elicited by each treatment as the worm burdens, the lengths of the worms and the faecal worm egg counts in the immunised lambs were less than those of the control lambs.     

Genetic instability in radiation-induced leukaemias: mouse models

Ivermectin is not lethal to the adult worms of Onchocerca volvulus or to those of O. ochengi, a cattle parasite closely related to O. volvulus. Although ivermectin penetrates the nodules in which the adults of these nematodes live, it is not known what levels of the drug enter the worms. Adult male O. ochengi were incubated in [3H]ivermectin in a saturated solution of unlabelled ivermectin (11.44 microM), to measure uptake by the oral and transcuticular routes, and in [3H]inulin, to ascertain if oral ingestion occurs in vitro. Uptake of [3H]ivermectin was high [1040 disintegrations/min (d.p.m.) at 3 h, representing a mean total of 86 pmoles ivermectin/worm] and occurred predominantly by the transcuticular route. Viability of worms was not reduced by this exposure, and uptake continued for up to 12 h. Only low levels of [3H]inulin (four d.p.m.) were detected in worms, indicating that the gut is probably not functional in vitro. Scanning and transmission electron microscopy revealed that the epicuticle of both sexes had an irregular surface which was pitted with a honeycomb structure in males, and rough and abundantly folded in females. These structures greatly increased the absorptive surface of the worms. In conclusion, ivermectin is able to enter adult O. ochengi males at concentrations sufficient to kill non-filarial nematodes.