A comparison of two methods for quantifying parasitic nematode fecundity

Cross infection of Haemonchus contortus between calves and lambs

Haemonchus contortus can frequently be found infecting pre-weaned beef calves on sheep and beef farms around the North Island of New Zealand. The purpose of this study was to determine whether parasites cycling in young cattle constitute a potentially important source of infection for sheep. A field isolate of H. contortus was cycled through either calves or lambs for 3 generations. The larvae resulting from the third cycle of infection were then used to infect both lambs and calves and the resulting faecal nematode egg count (FEC), worm burden, adult worm length and in utero egg count were measured. Larvae derived from lambs inoculated into calves exhibited lower establishment rates, the adult worms were shorter, had lower in utero egg counts, and the resulting faecal egg counts were also lower than when inoculated into lambs (p < 0.01). H. contortus' lack of ability to passage freely between lambs and calves indicates that large populations are unlikely to occur under mixed grazing, resulting in limited potential as a source of infection in sheep. However, indications of an ability to adapt to the alternative host suggest that some investigation of infection in cattle dominant farming operations in the north of the country might be warranted.

A genome-scale metabolic model of parasitic whipworm

Genome-scale metabolic models are widely used to enhance our understanding of metabolic features of organisms, host-pathogen interactions and to identify therapeutics for diseases. Here we present iTMU798, the genome-scale metabolic model of the mouse whipworm Trichuris muris. The model demonstrates the metabolic features of T. muris and allows the prediction of metabolic steps essential for its survival. Specifically, that Thioredoxin Reductase (TrxR) enzyme is essential, a prediction we validate in vitro with the drug auranofin. Furthermore, our observation that the T. muris genome lacks gsr-1 encoding Glutathione Reductase (GR) but has GR activity that can be inhibited by auranofin indicates a mechanism for the reduction of glutathione by the TrxR enzyme in T. muris. In addition, iTMU798 predicts seven essential amino acids that cannot be synthesised by T. muris, a prediction we validate for the amino acid tryptophan. Overall, iTMU798 is as a powerful tool to study not only the T. muris metabolism but also other Trichuris spp. in understanding host parasite interactions and the rationale design of new intervention strategies.

Influence of probiotic supplementation on parasitological parameters in lambs

The control of parasitosis is based on the use of anthelmintics. However, its long-term and indiscriminate use can select populations of resistant nematodes. New alternatives such as probiotics are being studied to solve this problem. This study aimed to investigate the effects of an oral probiotic containing six different bacterial strains and the yeast Saccharomyces cerevisiae on the blood biochemistry, parasitological, and histological parameters of naturally infected lambs. Forty-two weaned Texel or Ile de France crossbred lambs aged 86.9 ± 8.0 days and weighing 27.4 ± 3.7 kg were randomly allocated into three groups (n = 14 lambs). The control group (CG) was fed a basal diet without probiotic supplementation. The treatment group 1 g (T1G) was fed a basal diet with commercial probiotic supplementation at a dose of 1 g/lamb/day. The treatment group 5 g (T5G) was fed a basal diet with commercial probiotic supplementation at a dose of 5 g/lamb/day. The experimental period was 84 days, where the groups undergo mild natural infection. Every two weeks the hematocrit, total protein, albumin, globulin, fibrinogen, plasma protein, fecal egg count (FEC), and fecal consistency score were evaluated. Twenty lambs were slaughtered for histological evaluation of the rumen and abomasal wall and for counting abomasal nematodes. The area, length, and number of eggs from the recovered Haemonchus contortus female uteri were measured. Data were analyzed using analysis of variance (ANOVA) and Tukey's test (p ≤ 0.05). The area and length of Haemonchus contortus females from T1G were smaller (p < 0.01) than those of CG and T5G. The number of eggs from the H. contortus female uterus was lower (p < 0.01) in T1G and T5G. Evaluating the incidence of diarrhea, the T1G and T5G groups had a higher prevalence with a 35% and 39% score of zero, respectively (p < 0.05), while the CG group had 22%. All other evaluated parameters showed no significant differences (p > 0.05) between the groups. The probiotic had a beneficial effect on the gastrointestinal health of the weaned lambs through a decrease of the area, length, and the number of eggs of female H. contortus and an improvement in fecal consistency.

Phenotypic characterization and multiple resistance analysis in an experimentally selected albendazole-resistant hookworm isolate

For some nematodes, alterations that leads to a resistance genotype may be accompanied by other modifications, causing changes in the biology of the parasite, although the exact mechanisms of this relationship are still not very clear. These alterations can have deleterious effects on their survival or even potentiate their pathogenicity. In this study a phenotypic characterization was carried out to compare two Ancylostoma ceylanicum isolates, a wild type one, kept in the laboratory and an albendazole selected resistant isolate (AceyBZR2). Differences in some analyzed parameters, between the two strains, were registered, as patency period, number and size of the recovered worms, including differences in the body structures. The AceyBZR2 isolate showed to be less adapted to the host, leading to a smaller number of recovered worms. However, no difference on the female egg content was observed between the two isolates. Concerning blood evaluation, no differences were found between the wild type and AceyBZR2 isolates, related to hemoglobin and hematocrit levels. However, animals in the group infected with the wild type isolate had lower serum iron concentrations than animals in the AceyBZR2 group. The possibility that the AceyBZR2 isolate might be resistant to other drugs was evaluated and it was demonstrated that it does not present cross-resistance to ivermectin and nitazoxanide. However, when animals infected with the AceyBZR2 were treated with another drug from the benzimidazoles group (mebendazole), the cross-resistance effect was observed. Morphometric analyses were performed comparing female and male adult worms from the two isolates. The results presented here allow a better understanding of the parasite-host relationship and may constitute a useful basis for establishing future control strategies for soil-transmitted helminths.