Effects of blood-induced infections of Plasmodium hermani on domestic and wild turkey poults

Different paths - the same virulence: experimental study on avian single and co-infections with Plasmodium relictum and Plasmodium elongatum

Co-infections are prevalent worldwide, however, we are still struggling to understand interactions between different parasites and their impacts on host fitness. In the present experimental study we analysed the infection dynamics of two avian malarial parasites Plasmodium elongatum (genetic lineage pERIRUB01) and Plasmodium relictum (genetic lineage pSGS1) and their impacts on host health during single and co-infections. We reveal that P. elongatum intensity of parasitemia is enhanced by the presence of P. relictum during co-infection, while the parasitemia of P. relictum stays the same. This illustrates how development of a parasite (P. elongatum) which infects both mature and young (polychromatic) red blood cells (RBCs) is facilitated during co-infection with a parasite which specialises in adult RBCs only (P. relictum). The virulence of co-infections was similar to that of the more virulent parasite (P. elongatum). However, the profile of infection and the mechanisms that caused mortality were different. Birds infected with P. elongatum only start to die due to non-regenerative anaemia, when intensity of parasitemia is light and the number of polychromatic RBCs decrease dramatically. Meanwhile, co-infected birds start to die when the mean intensity of parasitemia reaches 10% and the number of polychromatic RBCs increases abnormally, reflecting regenerative anaemia. Our findings reveal that typically measured parameters of virulence (e.g., mortality rate, level of hematocrit) can be the same during single and co-infections, but the mechanisms responsible for the observed virulence can be different. This information serves a better understanding of the processes underpinning the interactions of co-infected parasite species.

Parasites of the Christmas Turkey

In the temperate West, the turkey remains popular fare for festive feasts. It is a large bird, amenable to intensive rearing, and now represents one of the cheapest forms of poultry meat available (Box 1). In the USA alone, nearly 100 million birds are raised annually - mainly in Minnesota and North Carolina. But intensive rearing can incur risks of epizootic parasitic diseases, often responsible for severe economic losses. Improved management and medication have reduced the impact of some, such as 'gapezvorm disease', histomoniasis and intestinal coccidiosis; leucocytozoonosis now presents less of a threat than in the past, but some 'newer' diseases such as cryptosporidiosis may yet present severe problems. In this article, Peter Long, William Current and Gayle Noblet review the main parasite challenges faced by the commercial turkey industry.