One Health: parasites and beyond

The field of parasitism is broad, encompassing relationships between organisms where one benefits at the expense of another. Traditionally the discipline focuses on eukaryotes, with the study of bacteria and viruses complementary but distinct. Nonetheless, parasites vary in size and complexity from single celled protozoa, to enormous plants like those in the genus Rafflesia. Lifecycles range from obligate intracellular to extensive exoparasitism. Examples of parasites include high profile medical and zoonotic pathogens such as Plasmodium, veterinary pathogens of wild and captive animals and many of the agents which cause neglected tropical diseases, stretching to parasites which infect plants and other parasites (e.g. (Blake et al., 2015; Hemingway, 2015; Hotez et al., 2014; Kikuchi et al., 2011; Meekums et al., 2015; Sandlund et al., 2015). The breadth of parasitology has been matched by the variety of ways in which parasites are studied, drawing upon biological, chemical, molecular, epidemiological and other expertise. Despite such breadth bridging between disciplines has commonly been problematic, regardless of extensive encouragement from government agencies, peer audiences and funding bodies promoting multi-disciplinary research. Now, progress in understanding and collaboration can benefit from establishment of the One Health concept (Stark et al., 2015; Zinsstag et al., 2012). One Health draws upon biological, environmental, medical, veterinary and social science disciplines in order to improve human, animal and environmental health, although it remains tantalizingly difficult to engage many relevant parties. For infectious diseases traditional divides have been exacerbated as the importance of wildlife reservoirs, climate change, food production systems and socio-economic diversity have been recognised but often not addressed in a multi-disciplinary manner. In response the 2015 Autumn Symposium organized by the British Society for Parasitology (BSP; https://www.bsp.uk.net/home/) was focused on One Health, running under the title ‘One Health: parasites and beyond…’. The meeting, held at the Royal Veterinary College (RVC) in Camden, London from September 14th to 15th, drew upon a blend of specialist parasitology reinforced with additional complementary expertise. Scientists, advocates, policy makers and industry representatives were invited to present at the meeting, promoting and developing One Health understanding with relevance to parasitology. The decision to widen the scope of the meeting to non-parasitological, but informative topics, is reflected in the diversity of the articles included in this special issue. A key feature of the meeting was encouragement of early career scientists, with more than 35% of the delegates registered as students and 25 posters

Genetička raznolikost unutar 18S rRNA i aktin-lokusa Cryptosporidium scrofarum (Apicomplexa: Cryptosporidiidae) pri invaziji domaćih svinja (Sus scrofa domesticus) u Indiji

The genetic diversity was studied of Cryptosporidium scrofarum (syn Cryptosporidium pig genotype II) of domestic pigs (Sus scrofa domesticus) from Punjab, India. Nested PCR amplification targeting the 18S rRNA and actin gene loci from Cryptosporidium positive samples was carried out, and the amplicons were sequenced. Phylogenetic comparison of a partial 18S rRNA gene revealed that they were genetically most similar to C. scrofarum isolated from other parts of the world. However, comparison of sequences representing a fragment of the genomic actin locus identified a new genotype conserved within the isolates sampled from India but distinct from other published sequences, suggesting the presence of a different Indian genotype.U ovom je radu istraživana genetička raznolikost Cryptosporidium scrofarum (syn Cryptosporidium pig genotype II) domaćih svinja (Sus scrofa domesticus) iz regije Punjab, Indija. Provedeno je umnožavanje 18S rRNA i lokusa aktin-gena pomoću ugniježđene PCR metode iz uzoraka pozitivnih na Cryptosporidium te su sekvencirani amplikoni. Filogenetska usporedba parcijalnog 18S rRNA gena pokazala je da su uzorci genetski najsličniji C. scrofarum izoliranom u drugim dijelovima svijeta. Također, usporedba sekvencija dijela lokusa genomskog aktina otkrila je novi genotip očuvan unutar izolata uzorkovanih u Indiji, ali različitih od drugih objavljenih sekvencija, upućujući na postojanje zasebnog indijskog genotipa

Are Eimeria Genetically Diverse, and Does It Matter?

Eimeria pose a risk to all livestock species as a cause of coccidiosis, reducing productivity and compromising animal welfare. Pressure to reduce drug use in the food chain makes the development of cost-effective vaccines against Eimeria essential. For novel vaccines to be successful, understanding genetic and antigenic diversity in field populations is key. Eimeria species that infect chickens are most significant, with Eimeria tenella among the best studied and most economically important. Genome-wide single nucleotide polymorphism (SNP)-based haplotyping has been used to determine population structure, genotype distribution, and potential for cross-fertilization between E. tenella strains. Here, we discuss recent developments in our understanding of diversity for Eimeria in relation to its specialized life cycle, distribution across the globe, and the challenges posed to vaccine development

Insights on adaptive and innate immunity in canine leishmaniosis

Canine leishmaniosis (CanL) is caused by the parasite Leishmania infantum and is a systemic disease, which can present with variable clinical signs, and clinicopathological abnormalities. Clinical manifestations can range from subclinical infection to very severe systemic disease. Leishmaniosis is categorized as a neglected tropical disease and the complex immune responses associated with Leishmania species makes therapeutic treatments and vaccine development challenging for both dogs and humans. In this review, we summarize innate and adaptive immune responses associated with L. infantum infection in dogs, and we discuss the problems associated with the disease as well as potential solutions and the future direction of required research to help control the parasite

Dietary vitamin D improves performance and bone mineralisation, but increases parasite replication and compromises gut health in Eimeria infected broilers

Coccidial infections may reduce fat soluble vitamin status and bone mineralisation in broiler chickens. We hypothesised that broilers infected with Eimeria maxima would benefit from increased dietary supplementation with vitamin D (vitD) or with 25-OH-D3 (25D3). Male Ross 308 chickens were assigned to diets with low (L) or commercial (M) vitD levels (1000 vs 4000 IU/kg) supplemented as D3 or 25D3. At d11 of age birds were inoculated with water (C) or 7000 E. maxima oocysts (I). Pen performance was calculated over the early (d1 - 6), acute (d7 - 10) and recovery periods (d11 - 14) post-infection (pi). At the end of each period 6 birds per treatment were dissected to assess long bone mineralisation, plasma levels of 25D3, calcium and phosphorus, and intestinal histomorphometry. Parasite replication and transcription of cytokines IL-10 and IFN-γ were assessed at d6 pi using quantitative PCR. Performance, bone mineralisation and plasma 25D3 levels were significantly reduced during infection (P < 0.05). M diets or diets with 25D3 raised plasma 25D3, improved performance and aspects of mineralisation (P < 0.05). Offering L diets compromised feed efficiency pi, reduced femur breaking strength and plasma phosphorous levels at d10 pi in I birds (P < 0.05). Contrastingly, offering M diets or diets with 25D3 resulted in higher parasite loads (P < 0.001) and reduced jejunal villi length at d10 pi (P < 0.01), with no effect on IL-10 or IFN-γ transcription. Diets with 4000 IU/kg vitD content or with 25D3 improved performance and mineralisation, irrespective of infection status, whilst 4000 IU/kg levels of vitD further improved feed efficiency and mineralisation in the presence of a coccidial infection

A Novel Whole Yeast-Based Subunit Oral Vaccine Against Eimeria tenella in Chickens

Cheap, easy-to-produce oral vaccines are needed for control of coccidiosis in chickens to reduce the impact of this disease on welfare and economic performance. Saccharomyces cerevisiae yeast expressing three Eimeria tenella antigens were developed and delivered as heat-killed, freeze-dried whole yeast oral vaccines to chickens in four separate studies. After vaccination, E. tenella replication was reduced following low dose challenge (250 oocysts) in Hy-Line Brown layer chickens (p<0.01). Similarly, caecal lesion score was reduced in Hy-Line Brown layer chickens vaccinated using a mixture of S. cerevisiae expressing EtAMA1, EtIMP1 and EtMIC3 following pathogenic-level challenge (4,000 E. tenella oocysts; p<0.01). Mean body weight gain post-challenge with 15,000 E. tenella oocysts was significantly increased in vaccinated Cobb500 broiler chickens compared to mock-vaccinated controls (p<0.01). Thus, inactivated recombinant yeast vaccines offer cost-effective and scalable opportunities for control of coccidiosis, with relevance to broiler production and chickens reared in low-and middle-income countries (LMICs)

Development of cross-protective Eimeria-vectored vaccines based on apical membrane antigens

Recently, the availability of protocols supporting genetic complementation of Eimeria has raised the prospect of generating transgenic parasite lines which can function as vaccine vectors, expressing and delivering heterologous proteins. Complementation with sequences encoding immunoprotective antigens from other Eimeria spp. offers an opportunity to reduce the complexity of species/strains in anticoccidial vaccines. Herein, we characterise and evaluate EtAMA1 and EtAMA2, two members of the apical membrane antigen (AMA) family of parasite surface proteins from Eimeria tenella. Both proteins are stage-regulated, and the sporozoite-specific EtAMA1 is effective at inducing partial protection against homologous challenge with E. tenella when used as a recombinant protein vaccine, whereas the merozoite-specific EtAMA2 is not. In order to test the ability of transgenic parasites to confer heterologous protection, E. tenella parasites were complemented with EmAMA1, the sporozoite-specific orthologue of EtAMA1 from E. maxima, coupled with different delivery signals to modify its trafficking and improve antigen exposure to the host immune system. Vaccination of chickens using these transgenic parasites conferred partial protection against E. maxima challenge, with levels of efficacy comparable to those obtained using recombinant protein or DNA vaccines. In the present work we provide evidence for the first known time of the ability of transgenic Eimeria to induce cross protection against different Eimeria spp. Genetically complemented Eimeria provide a powerful tool to streamline the complex multi-valent anticoccidial vaccine formulations that are currently available in the market by generating parasite lines expressing vaccine targets from multiple eimerian species