Predicting the effects of parasite co-infection across species boundaries

Abstract

It is normal for hosts to be co-infected by parasites. Interactions among co-infecting species can have profound consequences, including changing parasite transmission dynamics, altering disease severity and confounding attempts at parasite control. Despite the importance of co-infection, there is currently no way to predict how different parasite species may interact with one another, nor the consequences of those interactions. Here, we demonstrate a method that enables such prediction by identifying two nematode parasite groups based on taxonomy and characteristics of the parasitological niche. From an understanding of the interactions between the two defined groups in one host system (wild rabbits), we predict how two different nematode species, from the same defined groups, will interact in co-infections in a different host system (sheep), and then we test this experimentally. We show that, as predicted, in co-infections, the blood-feeding nematode Haemonchus contortus suppresses aspects of the sheep immune response, thereby facilitating the establishment and/or survival of the nematode Trichostrongylus colubriformis; and that the T. colubriformis-induced immune response negatively affects H. contortus. This work is, to our knowledge, the first to use empirical data from one host system to successfully predict the specific outcome of a different co-infection in a second host species. The study therefore takes the first step in defining a practical framework for predicting interspecific parasite interactions in other animal systems.

Microbiome analysis as a platform R&D tool for parasitic nematode disease management

“…Co-infection models are important because it is accepted that different parasites co-habiting the same host can affect each other profoundly in ways that would not occur were they infecting the host as lone pathogens (34). This can result in one parasite creating a permissive environment for the other parasite or, conversely, one parasite negatively affecting the other parasite's growth.…”

“…Therefore, the effects of H. contortus or T. circumcincta alone on the ovine microbiome may be different than what is observed here. In response to a critical lack of information regarding the effects of co-infection on cohabiting parasites, a recent study has successfully employed methodology to predict how two nematodes will influence each other in terms of survival, even when they are examined in different host species (34). Future research would benefit this field by attempting to predict how host co-infection influences the microbiome compared with single-strain infections.…”

Gastrointestinal Helminths of a European Moose Population in Poland

“…In the present study, the presence of Haemonchinae infection appeared to predispose the host to higher counts of other abomasal parasites, and thus could worsen the course of parasitic infections, as previously observed in other moose parasites [ 21 , 22 ]. However, Haemonchinae nematodes, having wide-ranging immunomodulatory capacities [ 23 ], may also inhibit the occurrence of other nematodes under some conditions [ 24 ].…”

Infection against infection: parasite antagonism against parasites, viruses and bacteria

“…Although nematodes had the potential to suppress other parasitic infections, the interaction between coinfecting nematodes was intriguing and required further study. Pre-existing Trichostrongylus colubriformis negatively affected the survival of Haemonchus contortus, but contradictory results occurred with different infection orders [23]. The primary pathogen infecting the host was likely a determining factor in the relationship between Tetracapsuloides bryosalmonae and Myxobolus cerebralis [43] , but obvious antagonism was found between another two protozoa, Babesia microti and Plasmodium cynomolgi [24] .…”