Habitat and host factors associated with liver fluke (Fasciola hepatica) diagnoses in wild red deer (Cervus elaphus) in the Scottish Highlands

Sex—the most underappreciated variable in research: insights from helminth-infected hosts

The sex of a host affects the intensity, prevalence, and severity of helminth infection. In many cases, one sex has been found to be more susceptible than the other, with the prevalence and intensity of helminth infections being generally higher among male than female hosts; however, many exceptions exist. This observed sex bias in parasitism results primarily from ecological, behavioural, and physiological differences between males and females. Complex interactions between these influences modulate the risk of infection. Indeed, an interplay among sex hormones, sex chromosomes, the microbiome and the immune system significantly contributes to the generation of sex bias among helminth-infected hosts. However, sex hormones not only can modulate the course of infection but also can be exploited by the parasites, and helminths appear to have developed molecules and pathways for this purpose. Furthermore, host sex may influence the efficacy of anti-helminth vaccines; however, although little data exist regarding this sex-dependent efficacy, host sex is known to influence the response to vaccines. Despite its importance, host sex is frequently overlooked in parasitological studies. This review focuses on the key contributors to sex bias in the case of helminth infection. The precise nature of the mechanisms/factors determining these sex-specific differences generally remains largely unknown, and this represents an obstacle in the development of control methods. There is an urgent need to identify any protective elements that could be targeted in future therapies to provide optimal disease management with regard to host sex. Hence, more research is needed into the impact of host sex on immunity and protection.

Biochemical Evaluation of Antioxidant Enzyme Activities and Lipid Peroxidation Level Associated with Liver Enzymes in Patients with Fascioliasis

Fascioliasis, which is caused by infection with Fasciola gigantica and Fasciola hepatica, is a zoonotic disease with a global distribution. This comparative study aimed to investigate antioxidant enzyme activities and oxidative status of chronic fascioliasis patients. In this study, 20 patients were compared with 10 controls and the levels of superoxide dismutase (SOD), malondialdehyde (MDA), glutathione peroxidase (GPX), catalase (CAT), alanine aminotransferase (ALT) and aspartate aminotransferase (AST) enzymes were evaluated. The results showed that MDA, CAT, AST, and ALT levels were higher in patients than in controls, while SOD and GPX levels were higher in controls than in patients (P≤0.05). Moreover, the enzyme MDA showed a positive correlation with SOD and GPX in the infected group. The enzyme SOD had an indirect correlation with CAT and a direct correlation with GPX. The positive correlation between ALT and AST was shown to be extremely significant (P≤0.05). The significant decrease in antioxidant enzymes and an increase in serum lipid peroxidation in the red blood cells of patients with fascioliasis indicated the presence of oxidative stress, which showed inflammation and oxidative stress, the pathogenesis of which was indicative of the stage of infection.

The influence of liver fluke infection on production in sheep and cattle: a meta-analysis

Liver flukes (Fasciola spp.) are important parasites of ruminant livestock worldwide, causing profound damage to animal health and productivity. Many reviews have discussed the results of decades of research on the impact of fluke on livestock traits such as weight gain and milk production, but there have been no known attempts to collate previous research in a quantitative manner or to determine the factors that vary between studies that find substantial effects of fluke and others concluding that effects of fluke are negligible. Here, we use meta-analysis to provide quantitative "global" estimates of the impact of liver fluke on animal performance, and to identify elements of study design ("moderators") that influence variation between studies in their outcome. A literature search provided 233 comparisons of performance in fluke-infected and uninfected animals. We standardised these data as log response ratios and calculated effect size variances to weight studies by the accuracy of their estimates. We performed multi-level meta-analysis to estimate effects of fluke infection on daily weight gain, live weight, carcass weight, total weight gain and milk production. There were statistically-supported negative effects of fluke infection on daily weight gain, live weight and carcass weight (9%, 6% and 0.6% reductions, respectively), but not on total weight gain or milk production. A mixed-effects meta-analysis revealed that studies of younger animals found more severe effects of fluke on weight gain and that effects on live weight increased with time since infection. Limitations to the data that could be analysed, including a lack of statistical reporting in older papers and variation in the outcome variables measured, may have explained the relatively limited influence of modifiers that we detected. Our results provide, to our knowledge, the first quantitative estimate of the impact of liver fluke on performance across studies and highlight some elements of study design that can influence conclusions.