1
Hidden consequences of living in a wormy world: nematode-induced immune suppression facilitates tuberculosis invasion in African buffalo.
Am Nat. 2010 Nov; 176:613-24
All selected articles haveThis article has been added to your saved articles
You can follow/unfollow articles via MyF1000 or via the article or browse pages.
03 Nov 2010
DOI: 10.3410/f.5737957.5721055
This study explores a fascinating topic: how infection with macroparasites can affect the spread of microparasites.
Although the interaction between macro- and microparasite infections have been well described in model systems, this is one of the first studies addressing this question in a natural population...Continue reading
Although the interaction between macro- and microparasite infections have been well described in model systems, this is one of the first studies addressing this question in a natural population...Continue reading
This study explores a fascinating topic: how infection with macroparasites can affect the spread of microparasites.
Although the interaction between macro- and microparasite infections have been well described in model systems, this is one of the first studies addressing this question in a natural population of mammals (African buffalo) infected by nematodes and intracellular bacteria (the agent of the bovine tuberculosis). Helminths are known to induce a Th2-type immune response in their hosts and an impaired Th1 response. The Th1 response mostly drives the clearance of microparasite infections. Helminths can therefore promote microparasite infections by suppressing the Th1 response. In agreement with this idea, Ezenwa and coworkers found that nematode resistance in buffalo is associated with a weaker Th1 response and that experimentally removing nematodes (with antihelminthic drugs) improves Th1 immunity. In addition to these empirical results, they also showed, using a disease dynamic model, that helminth infection might actually be needed to allow the invasion of tuberculosis. These findings corroborate previous results gathered on model species; nevertheless, the fact that the interactions between pathogens and the host immune response occur in natural systems as well highlights the need to take into account this complexity in future work.
Although the interaction between macro- and microparasite infections have been well described in model systems, this is one of the first studies addressing this question in a natural population of mammals (African buffalo) infected by nematodes and intracellular bacteria (the agent of the bovine tuberculosis). Helminths are known to induce a Th2-type immune response in their hosts and an impaired Th1 response. The Th1 response mostly drives the clearance of microparasite infections. Helminths can therefore promote microparasite infections by suppressing the Th1 response. In agreement with this idea, Ezenwa and coworkers found that nematode resistance in buffalo is associated with a weaker Th1 response and that experimentally removing nematodes (with antihelminthic drugs) improves Th1 immunity. In addition to these empirical results, they also showed, using a disease dynamic model, that helminth infection might actually be needed to allow the invasion of tuberculosis. These findings corroborate previous results gathered on model species; nevertheless, the fact that the interactions between pathogens and the host immune response occur in natural systems as well highlights the need to take into account this complexity in future work.
Disclosures
None declared
Add Comment
Sorci G: F1000Prime Recommendation of [Ezenwa VO et al., Am Nat 2010, 176:613-24]. In F1000Prime, 03 Nov 2010; DOI: 10.3410/f.5737957.5721055. F1000Prime.com/5737957#eval5721055
F1000Prime Recommendations, Dissents and Comments for [Ezenwa VO et al., Am Nat 2010, 176:613-24]. In F1000Prime, 24 May 2013; F1000Prime.com/5737957
Only registered/signed-in users can make comments.
Sign in or Subscribe to create your user account and join the discussion.
Sign in or Subscribe to create your user account and join the discussion.
No comments yet.
Most hosts are infected with multiple parasites, and responses of the immune system to co-occurring parasites may influence disease spread. Helminth infection can bias the host immune response toward a T-helper type 2 (Th2) over a type 1 (Th1) response, impairing the host’s ability to control concurrent intracellular microparasite infections and potentially modifying disease dynamics. In humans, immune-mediated interactions between helminths and microparasites can alter host susceptibility to diseases such as HIV, tuberculosis (TB), and malaria. However, the extent to which similar processes operate in natural animal populations and influence disease spread remains unknown. We used cross-sectional, experimental, and genetic studies to show that gastrointestinal nematode infection alters immunity to intracellular microparasites in free-ranging African buffalo (Syncerus caffer). Buffalo that were more resistant to nematode infection had weaker Th1 responses, there was significant genotypic variation in nematode resistance, and anthelminthic treatment enhanced Th1 immunity. Using a disease dynamic model parameterized with empirical data, we found that nematode-induced immune suppression can facilitate the invasion of bovine TB in buffalo. In the absence of nematodes, TB failed to invade the system, illustrating the critical role nematodes may play in disease establishment. Our results suggest that helminths, by influencing the likelihood of microparasite invasion, may influence patterns of disease emergence in the wild.
DOI: 10.1086/656496
PMID: 20849271
