Fecundity Of Female Worms Research Articles

Effects of Havardia albicans supplementation on feed consumption and dry matter digestibility of sheep and the biology of Haemonchus contortus

This study evaluated effects of Havardia albicans foliage intake on sheep dry matter digestibility (DMD) and included post-mortem evaluation of Haemonchus contortus infection (i.e., worm burdens, worm female length, fecundity). Fifteen hair sheep (16±4.2kg live weight (LW)) raised free of gastrointestinal nematodes were used. Sheep were fed a basal diet: grain based concentrate and Pennisetum purpureum grass (900 and 100g/kg DM, respectively) and were infected on day 0 with 3000 H. contortus infective larvae. On day 28 post-infection (PI) sheep were distributed to three groups being: Control (100g/kg DM of basal diet), HA group (basal diet 600+H. albicans 400) and the HA+PEG group (basal diet 600+H. albicans 400)+Polyethylene glycol (PEG). The H. albicans foliage was supplied for 13d including 7d of adaptation (i.e., day 28–40 PI). The content of condensed tannins (CT), total polyphenols (TP) and total tannins (TT) was determined in the foliage. Concentrate, grass and H. albicans intake (g DM/kg LW0.75), DMD and H. contortus egg excretions were determined. Sheep were slaughtered at day 41 PI to assess adult worm burdens, female worm lengths and fecundity (i.e., eggs in utero). Foliage had (g/kg DM): 71.5 CT, 61.3 TP and 66.9 TT. Experimental groups had similar feed intakes, and intake of H. albicans was not affected by PEG. The DMD of HA+PEG and HA groups was lower than Control (P<0.05). Post-mortem worm burdens were similar in all groups, but the H. contortus females in the HA group were shorter and had reduced fecundity (P<0.05). Adding PEG (HA+PEG) eliminated the effect of H. albicans intake on worm length. A short period of H. albicans intake affected the DMD of sheep and reduced the H. contortus female worm length and fecundity. The use of this type of tannin-rich foliage could bring nutritional and anti-parasitic benefits to the ruminants which consume them.

Anthelmintic efficacy of five tropical native Australian plants against Haemonchus contortus and Trichostrongylus colubriformis in experimentally infected goats (Capra hircus)

The study of the anthelmintic properties of plants rich in plant secondary metabolites can provide ecologically sound methods for the treatment of parasites on grazing animals. The purpose of the present study was to evaluate the anthelmintic effect of five tropical native Australian plant species rich in plant secondary metabolites on adult Haemonchus contortus and Trichostrongylus colubriformis in experimentally infected goats. Thirty young, nematode-free goats were infected with 2500 H. contortus and 5000 T. colubriformis infective larvae thrice weekly for a week (day 1–7 of the experiment). On day 27 after first infection, the goats were allocated into six groups of five animals per group. From day 28 to day 35, fresh leaves from Acacia salicina, Acacia nilotica, Eucalyptus corymbia, Casuarina cunninghamiana and Eucalyptus drepanophylla were included in the goats diet. Five groups were offered leaves from one of these plant species and one group, the untreated control, received only the basal diet formulated with 20% Medicago sativa and 80% Avena sativa. Following plant material administration, the goats were monitored daily until day 40 and then slaughtered on day 41. Total faecal worm egg output, total production of larvae recovered from faecal cultures, total post-mortem worm burdens and the per capita fecundity of female worms were estimated. The toxicity of the plant species for the goats was measured by histopathological analyses of liver and kidney samples. Results showed that goats feeding on the plant material rich in plant secondary metabolites had significantly lower egg output compared to the control goats (P<0.05). A similar response was found for larval production in both H. contortus and T. colubriformis supporting that egg output was affected in both species. Although the total worm burdens were not affected by the plant material (P>0.05), the per capita fecundity was significantly reduced by E. corymbia, A. nilotica and A. salicina (P<0.05). No signs of toxicity were detected in the liver or kidney samples. It is concluded that goats can benefit from the short-term ingestion of plant secondary metabolites, which reduce the total faecal egg output and thus decrease the potential for re-infection from the pasture.

Effects of dietary non-starch polysaccharides on establishment and fecundity of Heterakis gallinarum in grower layers

It was hypothesized that the establishment and fecundity of Histomonas meleagridis free Heterakis gallinarum may be affected by dietary non-starch polysaccharides (NSPs). One-day-old female layer chicks (N=670) were fed ad libitum for 11wk one of the following diets in a three-times repeated experiment: basal diet (CON), basal diet plus pea bran rich in insoluble NSP (I-NSP), basal diet plus chicory root meal as a source of inulin rich soluble NSP (S-NSP). At the end of wk three, each feeding group was subdivided into an uninfected and an infected group of birds each being inoculated with a placebo or with 200 H. meleagridis free eggs of H. gallinarum. The birds were slaughtered 8wk post infection and their worm burdens, the nematode egg excretion, caeca sizes and weights as well as intracaecal pH and volatile fatty acid (VFA) concentrations were determined.The NSP supplemented diets and also infection led to reduced body weights (BWs) of birds and impaired the feed conversion rate (P<0.001). The NSP supplemented diets increased average length of caecum (P<0.001) with S-NSP exerting a stronger effect than I-NSP (P<0.05). Full caeca weight was increased by S-NSP (P<0.001). Feeding S-NSP lowered intracaecal pH and molar proportion of acetate and increased that of butyrate compared to CON and I-NSP (P<0.001). Caecal pool of VFA was increased with S-NSP (P<0.001).The NSP-diets elevated incidence of infection (P<0.01), average number of larvae (P<0.009) and total worm burden (P<0.001) compared to CON. The daily amount of faeces increased in NSP-fed birds (P<0.001). Number of eggs per gram of faeces (EPG), number of eggs excreted per worm population of a bird within 24h (EPD) and female worm fecundity (EPD/female worm) were elevated after feeding S-NSP (P≤0.002), whereas I-NSP led to lower EPG/female worm (P<0.05). The EPD increased in the sequence of CON<I-NSP<S-NSP (P<0.001).It is concluded that the pea bran and chicory root meal used as sources of insoluble and soluble dietary NSPs, respectively, provided favourable conditions for the establishment of H. gallinarum in grower layers. Chicory root meal additionally enhanced fecundity of the nematode. Therefore, the two natural sources of insoluble and soluble NSPs offer no potential as protecting agents against H. gallinarum infections in chicken.

Effect of feeding sericea lespedeza leaf meal in goats experimentally infected with Haemonchus contortus

Effect of sericea lespedeza [SL; Lespedeza cuneata (Dum-Cours.) G. Don.] leaf meal feeding was evaluated in two experiments in indoor reared goats with experimental infection of Haemonchus contortus larvae. In the first experiment, ten 8–10 month old male Spanish and Alpine cross kids pair matched for body weight and age were fed SL or bermudagrass [BG; Cynodon dactylon (L.) Pers.] hay one week before infection and were infected with 5000 H. contortus L3. The animals were maintained on the same diet for the remaining period and were slaughtered 28 days post-infection (DPI) to determine the establishment of incoming infective larvae. Goats fed SL had lower establishment (P<0.05) of H. contortus larvae than that of the control goats fed BG hay. In the second experiment, twenty-five 8–10 months old male Alpine cross, Saanen, Nubian×Saanen and Spanish kids reared in confinement on BG were experimentally infected with 5000 H. contortus L3. On 35 DPI, the animals were allocated to two groups after blocking by fecal egg count (FEC), and one group was fed SL leaf meal (n=13), and another control group remained on BG (n=12). Four goats/group were slaughtered successively on days 7, 14, and 28 days post SL feeding, except on day 7, when five SL fed goats were slaughtered. Fecal egg counts and blood packed cell volume (PCV) were measured at weekly intervals and worm count, female worm fecundity, worm length and mucosal eosinophils, mast cells and globule leucocytes were measured after slaughter. Goats fed SL had a lower FEC (P<0.05) one week after feeding, as compared to those fed on BG, and the values remained at low level thereafter. Similarly, PCV was also significantly affected by feeding (P<0.01), and feeding and time interaction (P<0.05). However, worm burden, female worm fecundity, parasite length, and mucosal inflammatory cell count were similar between the groups. Feeding SL reduced the establishment of infective larvae and FEC of H. contortus in experimental studies and this plant could be used for biological control of parasite infection under field conditions to limit the harmful effects of the parasites in goats.

Effects of feeding willow ( Salix spp.) upon death of established parasites and parasite fecundity

Two indoor feeding experiments with young sheep were conducted to compare effects of feeding condensed tannin (CT) containing willow ( Salix spp.) or chaffed lucerne hay ( Medicago sativa) upon death of established parasites and parasite fecundity. In Experiment 1, 24 parasite-free weaned male lambs were individually penned, fed chaffed lucerne hay ad libitum for 5 weeks and then fed either lucerne ( n = 12) or willow ( n = 12) diets for a further 5 weeks. Twelve days prior to willow feeding, all lambs were infected with a mixed population of 22,300 gastrointestinal nematodes comprising predominantly Teladorsagia spp. (0.93), with the remainder being Trichostrongylus, Cooperia and Haemonchus species. Voluntary feed intake, apparent digestibility, blood composition, faecal nematode egg counts, production of eggs and hatched larvae, female worm fecundity and worm burden at slaughter were measured. In Experiment 2, Teladorsagia eggs were added to the faeces of parasite-free sheep fed either lucerne or willow ( n = 9) to measure proportional recovery. Recovery of added Teladorsagia eggs was 0.85 in lucerne-fed lambs and 0.53 willow-fed lambs (P<0.001) which were then used as correction factors for Experiment 1 data. Hatched larvae per g of wet faeces tended (P=0.081) to be lower for sheep fed willow than lucerne chaff (0.71 versus 0.83 of eggs added). In Experiment 1, total CT concentration in willow was 27 g/kg DM, with only traces in lucerne, while organic matter digestibility was 0.648 versus 0.599 (P<0.001) for willow and chaffed lucerne. Introduction of willow at week 6 reduced VFI (P<0.001) but this progressively increased until it was similar to lucerne-fed sheep during weeks 9 and 10. Feeding willow reduced Haemonchus contortus (P<0.01) and female Teladorsagia circumcinta (P<0.05) worm burdens in the abomasum and reduced Cooperia curticei in the small intestine (P<0.01). Adjusted total daily egg production was lower in willow-fed sheep than lucerne-fed sheep due to reductions for Haemonchus and Teladorsagia spp. (P<0.05). Per capita fecundity ( i.e., eggs produced/worm/day) for H. contortus (P<0.05) and the number of eggs in utero as a measure of fecundity in both T. circumcincta and Trichostrongylus spp. (P<0.001) were lower for willow-fed sheep. Faeces incubation revealed reduced production of L 3 larvae for both H. contortus and T. circumcincta (P<0.05) in willow-fed sheep. Total white blood cells, total lymphocytes and subsets of lymphocytes were similar for both diets. Feeding willow to parasitised young sheep reduced nematode worm burdens and female worm fecundity, with abomasal dwelling species being most affected and conventional methods of measuring FEC underestimated nematode eggs in the faeces of willow-fed sheep.

Effect of a tropical tannin-rich plant Lysiloma latisiliquum on adult populations of Haemonchus contortus in sheep

Bioactive plants with anthelmintic (AH) properties represent a promising alternative solution to chemical treatments. The AH effect of several Mexican tannin-rich (TR) plants has been screened in vitro. The in vivo AH effect of one TR legume, Lysiloma latisiliquum (Tzalam) on nematode larval establishment was confirmed. The present trial aimed at evaluating the direct and indirect effects of L. latisiliquum fodder consumption on adult Haemonchus contortus. Twenty-two parasite-naïve hair sheep lambs were allocated to an infected group (I) (400 H. contortus L 3/kg BW on D0) and a non-infected group (NI). From D0 to D28 post infection (PI), all the lambs were fed a complete diet. On D28, the two groups were sub-divided into four groups. Two control (C) groups maintained on the original basal diet (CI: 6 infected lambs and CNI: 5 non-infected lambs). The two treatment groups (T) received L. latisiliquum fodder ad libitum up to D36 when lambs were humanely slaughtered (TI: 6 infected lambs and TNI: 5 non-infected lambs). From D28 to D36 PI, individual fodder consumption and nematode egg excretion were measured daily. At necropsy, abomasal contents were recovered to obtain worm burdens and measure the female worm length and fecundity. Histological samples were taken from the respective abomasums and small intestines to count mucosal inflammatory cells. An increased consumption of TR fodder was observed in the TI vs. the TNI group ( P < 0.01). Before L. latisiliquum distribution, faecal egg excretion was similar in TI and CI groups. From D29 PI the TI group showed lower faecal egg counts compared to CI group ( P < 0.02). Although no differences in worm burdens were observed, worms of the TI group were smaller and, according to their size, contained fewer eggs in utero than worms from the CI group ( P < 0.05). Only minor differences in mucosal inflammatory cells were observed between groups, indicating that the indirect effect was not evident. Thus, a short-term consumption of L. latisiliquum can modulate directly the biology of adult H. contortus affecting the worm size and female fecundity while the worm burdens were not affected. Infected animals ate more L. latisiliquum fodder than non-infected animals.

Effect of extra dietary lysine in Ascaridia galli-infected grower layers

The hypothesis examined in this study was that extra dietary lysine (Lys) above the recommended standard exerts beneficial effects on the defence reactions, growth performance and nutrient utilization in Ascaridia galli-infected chickens. Therefore, 1-day-old female Lohmann Selected Leghorn chickens were at first fed standard Lys diet (8.5 g Lys/kg DM). At 4 weeks of age, the birds were allocated to groups 1 and 3, both being continued on standard Lys diet, whereas birds in groups 2 and 4 were switched to extra Lys diet (10.5 g Lys/kg DM). Birds in groups 3 and 4 were additionally infected at this age (4 weeks) with 250 embryonated eggs of A. galli. All the birds were slaughtered 7-week-post-infection (p.i.) at an age of 11 weeks. Infected birds on standard Lys diet consumed more feed and reached a similar level of Lys intake as birds on extra Lys diet 7-week-p.i. Utilization of feed, crude protein, and Lys for body weight (BW) gain was adversely affected in infected birds on standard Lys diet ( P < 0.001). Extra Lys diet reduced the incidence of infection ( P < 0.05), but worm counts, worm length, faecal egg counts and female worm fecundity were not different between the infected groups ( P > 0.05). Extra Lys diet led to higher final BW in uninfected and infected birds ( P < 0.05). It is concluded that extra Lys above the normal recommended standard supports the defence reactions and compensates the negative effect of infection on growth performance and nutrient utilization in A. galli-infected birds.

Experimental concurrent infection of Afar breed goats with Oestrus ovis (L 1) and Haemonchus contortus (L 3): Interaction between parasite populations, changes in parasitological and basic haematological parameters

The study was conducted to examine the occurrence and interaction between Oestrus ovis and Haemonchus contortus in experimentally infected Ethiopian Afar breed of goats. Twenty goats were divided into four groups (O, OH, H, and C) of five animals each. Each animal of groups O and OH received weekly infections for 5 weeks with 66 first instar larvae (L 1) of O. ovis. Then animals of groups OH and H were infected with a single dose of 5000 third stage larvae (L 3) of H. contortus. Goats of group C were kept free of any infection as non-infected control. Faecal egg count (FEC), blood cell count, total serum protein level and body weight were recorded weekly throughout the study period. At necropsy worm burden, female worm length, fecundity and larval burden of O. ovis in the nasal-sinus cavities of infected animals were assessed. The results showed that the presence of H. contortus in the abomasum of goats of group OH had no influence on the development of O. ovis. On the contrary, a significant reduction ( P < 0.05) in FEC, worm burden, fecundity and female worm length was revealed in group OH animals compared to the mono-infected animals (group H). This was associated with eosinophilia and reduced packed cell volume.

Intraspecific density-dependent effects on growth and fecundity of Diplosentis nudus (Harada, 1938) Pichelin et Cribb, 2001 (Acanthocephala, Cavisomidae)

AbstractDuring June and July of 2007, a total of 130 specimens of the fish Rastrelliger kanagurta Cuvier (Teleostei, Scombridae), ranging between 19–31 cm in total length, were caught in the Red Sea off the coast of Sharm El-Sheikh, South Sinai, Egypt, and examined for infections by acanthocephalans (65 fish/month). Of this number, 29 (22.30%) were slightly or heavily parasitized by the acanthocephalan Diplosentis nudus (Harada, 1938) Pichelin et Cribb, 2001 (Cavisomidae); no other helminth parasites were found in the intestine of R. kanagurta. Twenty-nine infrapopulations of D. nudus, ranging from 23–218 individuals were collected from the infected fishes. These infrapopulations were distributed in a well-defined fundamental niche along the intestine of R. kanagurta, where the distribution of male worms was not random with respect to female worms size and position and suggests that the male-male competition for access to female may be intense and may select for large males. No correlation between fish size and infrapopulation size was observed. Correlations between female-to-male sex ratio and infrapopulation size, numbers of females and their mean lengths, numbers of males and their mean lengths, mean female length and mean male length within infrapopulation were very strong, and clearly suggest that as the infrapopulation size increased, the number of females and their mean lengths decreased and the number of males and their mean lengths increased. Combination of these results strongly suggests density-dependent effects and competition between male worms. The relationship between the mean female length or size and the number of eggs within its pseudocoel was strongly positive; egg production by female worm significantly decreases as the infrapopulation size increases, suggesting density-dependent reduction in female worm fecundity. Tendency for the variability in male testes size was not significant in infrapopulations of D. nudus. All of these results are discussed.

In silico exploration of the effects of host genotype and nutrition on the genetic parameters of lambs challenged with gastrointestinal parasites

An in silico mathematical model was used to explore the effect of, and the interaction between, (i) nutrition, (ii) genotype for growth and (iii) genotype for resistance, on the estimates of genetic parameters for resistance and performance in a population of lambs trickle-challenged daily with 3,000 L3s of Teladorsagia circumcincta. A previously published model for nematode infections in sheep was developed to include heritable variation in sheep growth traits, as well as in immunologically controlled traits such as establishment of incoming larvae, mortality of the adult worms and fecundity of the adult female worms. The simulated population comprised 10,000 lambs, these being the offspring of 250 sires mated to 5,000 dams. The model assumed the lambs to be parasitologically naïve at weaning (2 months of age), at which point the trickle challenge commenced and the model was updated daily until slaughter (at 6 months of age). Dietary treatments included a good and a poor quality feed, offered ad libitum. Two genotypes for growth were assumed: (i) fast and (ii) slow growing. Three genotypes for resistance were used: (i) benchmark, (ii) susceptible and (iii) resistant, differing in their ability to cope with nematode infections. Genetic parameters for output traits, including growth rate, food intake, worm burden and faecal egg count were estimated using a linear mixed model, fitting sire as a random effect to capture genetic effects. Heritabilities and correlations were found to change over time. In general, the heritabilities of immunity traits increased over time, whereas genetic correlations between production and immunity traits became weaker. Diet had a significant effect on the means and the estimated correlations of output traits, while genotypes for growth and resistance had smaller effects. These results suggest that discrepancies between published genetic parameters for nematode resistance may be a function of environmental factors rather than differences in host genotype.

Acute and chronic toxicities of tributyltin to various life stages of the marine polychaete Hydroides elegans

Experiments were performed to determine the acute and chronic toxicities of tributyltin (TBT) (nominal concentrations) to polychaete Hydroides elegans. Firstly, static tests were performed to examine the lethal effect of TBT on five life stages of H. elegans. The 48-h LC 50 (95% CI) for the eggs, 2-cells, trochophores, juveniles and adults was 0.18 (0.15–0.20), 0.97 (0.77–1.23), 2.36 (2.11–2.65), 2.86 (2.63–3.12) and 4.36 (4.04–4.71) μg TBT l −1, respectively. Secondly, a 17-d static renewal chronic test was conducted to study sensitivity of the early development (egg to juvenile) to TBT. The survivorship, percent settlement and time to reach settlement were significantly reduced at ⩾0.01 μg TBT l −1. Effects of TBT on the juvenile growth and maturation were also studied through a 44-d chronic test. Lower survivorship and reduced tube growth were observed only at ⩾1 μg TBT l −1, however, only H. elegans exposed to ⩽ 0.1 μg TBT l −1 reached maturity. The final experiment examined effects of TBT on the fecundity of female worms through a 60-d chronic test. Although survivorship remained high even at 1 μg TBT l −1, egg production, success in fertilization and egg development were all reduced at ⩾0.1 μg TBT l −1. Our results indicate that the early development of H. elegans is highly sensitive to TBT and this polychaete can be routinely employed as a test organism for both acute and chronic ecotoxicity bioassays in tropical and subtropical regions such as southern China.

A model to account for the consequences of host nutrition on the outcome of gastrointestinal parasitism in sheep: logic and concepts

A deterministic, dynamic simulation model is developed to account for the interactions between gastrointestinal parasitism and host nutrition, and predict their consequences on performance and level of parasitism of sheep. Larval intake and established adult worms are assumed to result in nutrient loss for the host. In order to reduce this loss the host will mount an immune response, which will affect the establishment rate of incoming larvae, mortality rate of adult worms, and fecundity of female worms, as well as nutrient loss caused by larval intake per se. Host anorexia is modelled as a function of worm mass. Parasitism is also assumed to affect the allocation of ingested nutrients to the host's bodily functions, with maintenance getting absolute priority, and protein allocated to immunity and production proportionally to their requirements. Inputs to the model include the expected growth attributes of the animal, feed quality, various parasitological parameters and daily larval intake. Outputs include feed intake, growth rate and body composition, as well as worm burden and faecal egg counts. The model allows exploration of the consequences of gastrointestinal parasitism on sheep of different growth characteristics, kept under environments that vary in the provision of nutrients and exposure to parasites.

The effect of inulin on new and on patent infections ofTrichuris suisin growing pigs

The objective of this experiment was to investigate the potential influence of inulin on the establishment of new and patent infections of Trichuris suis in growing pigs. Two experimental diets were formulated based on barley flour with either added insoluble fibre from oat husk (Diet 1) or a pure inulin (16%) supplementation (Diet 2). Twenty-eight 10-week-old pigs were divided randomly into 4 groups (Groups 1-4) each of 7 pigs. After 3 weeks adaptation to the experimental diets all pigs were infected with a single dose of 2000 infective T. suis eggs. Group 1 was fed Diet 1 until 7 weeks post-infection (p.i.) and Group 3 until 9 weeks p.i., Group 2 was fed Diet 2 until 7 weeks p.i., Group 4 was fed Diet 1 until week 7 p.i. and was switched-over from Diet 1 to Diet 2 until week 9 p.i. Seven weeks p.i. pigs in Groups 1 and 2 were slaughtered, and pigs in Groups 3 and 4 were slaughtered at 9 weeks p.i. Trichuris suis worm burdens were determined for all pigs. Inulin-fed pigs (Group 2) exhibited an 87% reduction in EPG, compared to the pigs on standard diet (Group 1) (P < 0.0001). The number of worms recovered at week 7 p.i. from pigs on the inulin diet (Group 2) was significantly reduced by 71%, compared to the pigs on standard diet (Group 1) (P < 0.01). At week 9, worm recovery in pigs on the inulin diet switch protocol (Group 4) was reduced by 47% compared to the control pigs in Group 3 (P < 0.01). Further, the inulin-fed pigs exhibited a significant reduction in female worm fecundity and worm large intestine location was more distal compared to those from pigs on standard diet. These results demonstrate that inclusion of the highly degradable fructose polymer inulin in the diet leads to significant reductions in T. suis establishment, egg excretion, and female worm fecundity and can be used as a treatment for patent infections.

A flow cytometry based method for studying embryogenesis and immune reactivity to embryogenic stages in filarial parasites

BackgroundIn the absence of intermediate animal hosts, the process of embryogenesis leading to fecundity of adult female filarial worms is very critical for persistence of these obligate parasites in human communities. Embryogenesis in adult female filarial parasites involves fertilization of eggs or oocytes by sperms and their subsequent development into motile microfilariae inside the uterine cavity of worms. Development of assays for monitoring embryogenesis in adult female worms is a critical requirement in filariasis research – filarial worms are known to harbour endosymbionts such as Wolbachia which play a significant role in fecundity. Tetracycline or doxycycline treatment of the infected hosts effectively eliminates the endosymbionts resulting in inhibition of embryogenesis in female worms. Currently, inhibition of embryogenesis in adult filarial worms can be monitored only by microscopic examination of in vitro harvested intrauterine stages.MethodsAdult female filarial worms of bovine filarial parasites, Setaria digitata were collected from the peritoneum of infected animals and intrauterine stages were harvested in culture medium and were analyzed for forward and side scatter by flowcytometry using a BD FACS Calibur. Different populations were gated, sorted and identified by phase microscopy. Binding of biotinylated lectins to intra uterine stages was monitored using FITC labeled Avidin and monitored by flow cytometry of gated populations. Similarly, binding of antibodies in human filarial sera to intrauterine stages was monitored using FITC labeled anti-human immunoglobulins.ResultsThe forward and side scatter for intrauterine stages delineated 3 distinct populations labeled as R1, R2 and R3. The three populations were sorted and identified to be a) fully stretched microfilariae, b) early and c) late developmental stages of eggs respectively. Lectins such as Wheat Germ agglutinin or Concanavalin-A were found to bind strongly to egg stages and less prominently to intra-uterine microfilariae. Similarly the binding of antibodies in filarial sera to the three intra-uterine stages could also be precisely quantified.ConclusionThe manuscript reports a novel flow cytometry based method to monitor progression of embryogenesis in adult filarial worms. Apart from relative quantification of different intra uterine developmental stages, the assay allows quantitative binding of lectins and antibodies to each of the intrauterine stages. It may now be possible to quantify levels of antibodies in infected and immune hosts to monitor anti-fecundity immunity in filariasis – the assay can thus be used as a powerful tool for drug development and in immunological studies in human and experimental filariasis.

Oral administration of a live Aro attenuated Salmonella vaccine strain expressing 14-kDa Schistosoma mansoni fatty acid-binding protein induced partial protection against experimental schistosomiasis

We report the oral vaccination of SWISS mice with an Aro attenuated Salmonella enterica var. Typhimurium vaccine strain expressing the 14-kDa Schistosoma mansoni antigen, Sm14. Bacterial adjuvants, including (i) Lactococcus lactis expressing interleukin-12 (IL-12) and (ii) Lactobacillus delbrueckii UFV-H2b20, were also employed in oral immunization assays. Detection assays to specific IgG and IgA anti-Sm14 antibodies were performed to evaluate humoral immune responses in vaccinated mice. An increase in specific IgG titers was observed; however, no IgA production was detected. The protection levels against schistosomiasis (34.9–49.5%) obtained with all experimental formulations in this work were very similar to values reported by previous studies, which used purified recombinant Sm14 for parenteral vaccination of mice. There was a slight reduction in hepatic granulomas of mice vaccinated with Salmonella. Oogram studies showed diminished numbers of S. mansoni eggs in the intestinal wall of vaccinated mice, but individual female worm fecundity did not seem to be affected by our immunization protocol.

Increased parasiticide activity against Trichinella spiralis newborn larvae during pregnancy.

To evaluate whether pregnancy has a synergetic effect on the host's immune response against Trichinella spiralis infection, immunological and parasitological parameters relating to the infection were assessed in pregnant rats and compared to those observed in virgin infected rats. The muscle parasite load was lower in pregnant infected rats but no differences were found in the intestinal worm burdens or the fecundity of female worms. The ability of sera to mediate death in newborn larvae (NBL) in an antibody-dependent cell cytotoxicity assay was higher for pregnant rats, even in the absence of specific anti-NBL antibodies. High levels of total and anti-NBL IgE were found in both groups, however, these levels were higher in the group of pregnant infected animals. No differences were found in anti-NBL IgGAM titers, nevertheless in some pregnant infected rats these antibodies were found earlier. No differences were found in peritoneal or blood eosinophil counts. Offspring born to infected dams were found to be infected. The results obtained in this model demonstrate that during pregnancy there is an enhanced helminthotoxic effect towards the NBL. Despite this immunoactivation, vertical transmission of the parasite is possible.

Tyvelose and protective responses to the intestinal stages of Trichinella spiralis

The unusual sugar tyvelose is the immunodominant portion of the major larval glycoprotein antigens of Trichinella spiralis, which play an important role in generating immunity against the intestinal stages of infection. The possibility that the tyvelose component itself may have a host- or parasite-protective role in the intestine was tested by following the outcome of challenge infections in mice primed and boosted with tyvelose-BSA, or in mice primed with tyvelose-BSA before boosting with larval antigen. Although antibody responses were raised against tyvelose there was no evidence of protective immunity against the intestinal stages, as assessed by total adult worm recovery or by size and fecundity of female worms in immunized mice. Equally, priming with tyvelose-BSA before boosting with larval antigen had no effect on the expression of immunity against a challenge infection. The predominant antibody isotype recorded in all immunized mice was IgG1, suggesting the induction of type 2 T cell responses, and this was confirmed by cytokine analysis, mesenteric node lymphocytes of all mice showing production of IL-5 but not IFN-gamma. Clearly immunization with tyvelose had no significant effect on T cell polarization. The data show that, with the experimental design employed, there was no evidence for a functional role of tyvelose in either host- or parasite-protection during the intestinal phase of infection.

Fecundity and egg output by Toxocara canis in the red fox, Vulpes vulpes.

The role of the red fox Vulpes vulpes in the dissemination of eggs of Toxocara canis into the environment is considered with reference to female worm fecundity and egg output in the faeces of infected foxes collected from four localities in southern England. A significant positive correlation was found between female worm size and the number of eggs in the uterus but there was no significant relationship between T. canis worm numbers and egg output in fox faeces. Reliable estimates of worm burdens in foxes could not, therefore, be determined from faecal egg counts alone. The highest mean egg output of 2145.0 epg recorded from adult foxes indicated that fox cubs are not necessarily the main sources of environmental contamination with T. canis eggs. Saturated magnesium sulphate was found to be a more effective flotation solution than zinc sulphate and sodium chloride for recovering eggs from fox faecal samples.

Effect of iron deficiency onTrichuris suisandAscaris suuminfections in pigs

The objective of this experiment was to detect a possible interaction between iron deficiency and intestinal nematode infections. We report on a 2 x 2 study where thirty-one 10-week-old pigs fed a low or a normal iron diet were infected with both Trichuris suis (4500 eggs) and Ascaris suum (1200 eggs). No significant difference was detected between diet groups with respect to parasitological parameters for A. suum or the total number of adult T. suis recovered at necropsy 10 weeks p.i. However, in the low iron group T. suis were located more proximally and the worms were increased in length. A higher proportion of pigs with initial faecal egg excretion at 6 weeks p.i. was observed in the low iron group, indicating a shortened pre-patency period. Worm fecundity and total faecal egg excretion were also highest in the low iron group. A significant correlation was found between female worm length and fecundity. The peripheral eosinophil counts were diminished in the low iron host groups. The infected low iron group experienced more severe pathophysiological changes in terms of hypoalbuminaemia and decreases in erythrocyte volumes. A significant inverse correlation existed between iron content in the bone-marrow and liver (body) store. In conclusion, iron deficiency increased the severity of T. suis infection in pigs.

Vaccine Strategies against Schistosomiasis: From Concepts to Clinical Trials

Schistosomiasis, the second major parasitic disease in the world after malaria, affects 200 million people. Vaccine strategies represent an essential component of the control of this chronic debilitating disease where the deposition of millions of eggs in the tissues is the main cause of pathology. Research developed in our laboratory over the last 20 years has led to the identification of novel effector mechanisms, pointing for the first time to the protective role of Th2 responses and of IgE antibodies now supported by seven studies in human populations. The identification and molecular cloning of a target antigen, a glutathione S-transferase (GST), has made it possible to demonstrate its vaccine potential in several animal species (rodents, cattle, primates) and to establish consistently the capacity of vaccination to reduce female worm fecundity and egg viability through the production of neutralizing antibodies (IgA and IgG). Following promising preclinical studies, clinical trials (phase I and II) have been undertaken using Schistosoma haematobium GST, Sh28GST. High titers of neutralizing antibodies were produced (IgG3 and IgA) together with Th2 cytokines, consistently with the concepts developed from experimental models. With these results we are on the way towards a feasible approach of vaccine development against a major human parasitic disease.