Alternatives to animal experimentation in parasitology

Battle of the sexes: analysis of sex bias in host use and reporting practices in parasitological experiments

Experimental approaches are among the most powerful tools available to biologists, yet in many disciplines their results have been questioned due to an underrepresentation of female animal subjects. In parasitology, experiments are crucial to understand host-parasite interactions, parasite development, host immune responses, as well as the efficacy of different control methods. However, distinguishing between species-wide and sex-specific effects requires the balanced inclusion of both male and female hosts in experiments and the reporting of results for each sex separately. Here, using data from over 3600 parasitological experiments on helminth-mammal interactions published in the past four decades, we investigate patterns of male versus female subject use and result reporting practices in experimental parasitology. We uncover multiple effects of the parasite taxon used, the type of host used (rats and mice for which subject selection is fully under researcher control versus farm animals), the research subject area and the year of publication, on whether host sex is even specified, whether one or both host sexes have been used (and if only one then which one), and whether the results are presented separately for each host sex. We discuss possible reasons for biases and unjustifiable selection of host subjects, and for poor experimental design and reporting of results. Finally, we make some simple recommendations for increased rigour in experimental design and to reset experimental approaches as a cornerstone of parasitological research.

Caenorhabditis elegans in anthelmintic research - Old model, new perspectives

For more than four decades, the free-living nematode Caenorhabditis elegans has been extensively used in anthelmintic research. Classic genetic screens and heterologous expression in the C. elegans model enormously contributed to the identification and characterization of molecular targets of all major anthelmintic drug classes. Although these findings provided substantial insights into common anthelmintic mechanisms, a breakthrough in the treatment and control of parasitic nematodes is still not in sight. Instead, we are facing increasing evidence that the enormous diversity within the phylum Nematoda cannot be recapitulated by any single free-living or parasitic species and the development of novel broad-spectrum anthelmintics is not be a simple goal. In the present review, we summarize certain milestones and challenges of the C. elegans model with focus on drug target identification, anthelmintic drug discovery and identification of resistance mechanisms. Furthermore, we present new perspectives and strategies on how current progress in C. elegans research will support future anthelmintic research.

Artificial blood feeders for mosquito and ticks-Where from, where to?

Mosquito and tick feeding activity represent a key threat for humans, livestock, pets and wildlife worldwide. Rearing these vectors in laboratory conditions is extremely important to investigate basic facets of their biology, vector competence, new control strategies, as well as mechanisms of pesticide resistance. However, the use of animals or humans to provide blood for hematophagous arthropod feeding poses a strict limit to these researches, due to the accidental transmission of diseases, ethical problems concerning animal welfare, as well as expensive and time-consuming animal rearing procedures. The use of devices to artificially feed arthropod vectors can importantly leverage progresses in parasitology and entomology. The aim of this review is to summarize current knowledge about artificial feeding of mosquitoes and ticks, focusing on key concepts and case studies about the design and fabrication of blood feeding devices. From a technical standpoint, the literature analyzed here showed little standardization of materials used for fabricating membrane interfaces, as well as in the strategy used to heat the "biomimetic host". In addition, a lack of uniform methods to design an architecture merging complex and realistic cues with an easy-to-assemble approach have been found. Some commercial products are available, but they are quite expensive, thus hard to reach for many laboratories, especially in developing countries. An important challenge for future research is represented by the introduction of automation and bioinspired engineered solutions in these devices, improving the effectiveness of blood-feeding systems by increasing their host-mimicking features. Automation can reduce labor costs and provide interesting solutions - in line with the 3R principle "reduce, replace and refine" - aimed to minimize the employ of experimental animals in research.

Cracking the nodule worm code advances knowledge of parasite biology and biotechnology to tackle major diseases of livestock

Many infectious diseases caused by eukaryotic pathogens have a devastating, long-term impact on animal health and welfare. Hundreds of millions of animals are affected by parasitic nematodes of the order Strongylida. Unlocking the molecular biology of representatives of this order, and understanding nematode-host interactions, drug resistance and disease using advanced technologies could lead to entirely new ways of controlling the diseases that they cause. Oesophagostomum dentatum (nodule worm; superfamily Strongyloidea) is an economically important strongylid nematode parasite of swine worldwide. The present article reports recent advances made in biology and animal biotechnology through the draft genome and developmental transcriptome of O. dentatum, in order to support biological research of this and related parasitic nematodes as well as the search for new and improved interventions. This first genome of any member of the Strongyloidea is 443 Mb in size and predicted to encode 25,291 protein-coding genes. Here, we review the dynamics of transcription throughout the life cycle of O. dentatum, describe double-stranded RNA interference (RNAi) machinery and infer molecules involved in development and reproduction, and in inducing or modulating immune responses or disease. The secretome predicted for O. dentatum is particularly rich in peptidases linked to interactions with host tissues and/or feeding activity, and a diverse array of molecules likely involved in immune responses. This research progress provides an important resource for future comparative genomic and molecular biological investigations as well as for biotechnological research toward new anthelmintics, vaccines and diagnostic tests.

Toxoplasma tachyzoites from cell culture are more appropriate in some situations

BACKGROUND

Laboratories traditionally culture toxoplasma tachyzoites in animals for testing and experimental use. This article considers why available cell culture methods are not used more often.

AIM

To compare HeLa cell culture and animal culture for production of toxoplasma tachyzoites.

METHODS

In 2000 HeLa culture replaced animal culture for continuous production of toxoplasma tachyzoites in the Scottish Toxoplasma Reference Laboratory. The performance of animal culture (1994-1998) was compared with HeLa culture (2004-2008). A PubMed search was carried out for 1998 and 2008 to assess the culture methods used in laboratories.

RESULTS

Animal culture was able to produce higher yields of tachyzoites (10(9) from a cotton rat peritoneal harvest compared to 10(7) from a 75 cm(2) cell culture flask) but significantly more HeLa cultures were successful (93% versus 84%; p=0.025). There was no difference in the quality of tachyzoites from animal and HeLa cultures as demonstrated by the high levels of success in the dye test. HeLa culture offered significant advantages in flexibility and control. A review of the literature showed no significant change in the method of culture used in laboratories between 1998 and 2008 (p=0.36).

CONCLUSION

The availability of cell culture methods and the increasingly stringent regulations on the use of animals have not resulted in a decline in the use of animal culture. Animals are necessary for certain experiments but many studies could use cell-culture-derived parasites.

A simple and rapid method for cryopreservation of Trichomonas vaginalis

A pellet freezing method, one type of rapid freezing protocol, was established for Trichomonas vaginalis. As cryoprotectants, 5-20% dimethylsulfoxide (DMSO), ethylene glycol, propylene glycol, and glycerol were used. Of these, DMSO showed a high protective effect, with a maximum effect at a concentration of 20%. No effect of equilibration time was recognized with any of the cryoprotectants. Therefore, the optimal condition was deemed 20% DMSO without equilibration. The pellet freezing method was also compared with the conventional slow cooling protocol. The survival rate was 73 +/- 8% with the slow cooling protocol and 48 +/- 4% with the pellet freezing method. The delay in growth with the pellet freezing method was no more than 5.4 h compared with the slow cooling protocol, suggesting its validity as a technique for cryopreservation of T. vaginalis.

Oesophagostomum dentatum: potential as a model for genomic studies of strongylid nematodes, with biotechnological prospects

There are substantial gaps in the knowledge of the molecular processes of development and reproduction in parasitic nematodes, despite the fact that understanding such processes could lead to novel ways of treating and controlling parasitic diseases, through blocking or disrupting key biological pathways. Biotechnological advances through large-scale sequencing projects, approaches for the analysis of differential gene and protein expression and functional genomics (e.g., double-stranded RNA interference) now provide opportunities to investigate the molecular basis of developmental processes in some parasitic nematodes. The porcine nodule worm, Oesophagostomum dentatum (order Strongylida), may provide a platform for testing the function of genes from this and related nematodes, given that this species can be grown and maintained in culture in vitro for periods longer than other nematodes of the same order. In this article, we review relevant biological, biochemical and molecular biological and genomic information about O. dentatum and propose that the O. dentatum - pig system provides an attractive model for exploring molecular developmental and reproductive processes in strongylid nematodes, leading toward new intervention methods and biotechnological outcomes.