An inverse association between West Nile virus serostatus and avian malaria infection status

Abstract

BackgroundVarious ecological and physiological mechanisms might influence the probability that two or more pathogens may simultaneously or sequentially infect a host individual. Concurrent infections can have important consequences for host condition and fitness, including elevated mortality risks. In addition, interactions between coinfecting pathogens may have important implications for transmission dynamics.MethodsHere, we explore patterns of association between two common avian pathogens (West Nile virus and avian malaria parasites) among a suburban bird community in Chicago, IL, USA that share mosquito vectors. We surveyed 1714 individual birds across 13 species for both pathogens through established molecular protocols.ResultsField investigations of haemosporidian and West Nile virus (WNV) infections among sampled birds yielded an inverse association between WNV serostatus and Plasmodium infection status. This relationship occurred in adult birds but not in juveniles. There was no evidence for a relationship between Haemoproteus infection and WNV serostatus. We detected similar prevalence of Plasmodium among birds captured with active WNV infections and spatiotemporally paired WNV-naïve individuals of the same species, demonstrating that the two pathogens can co-infect hosts.ConclusionsMechanisms explaining the negative association between WNV serostatus and Plasmodium infection status remain unclear and must be resolved through experimental infection procedures. However, our results highlight potential interactions between two common avian pathogens that may influence their transmission among hosts. This is especially relevant considering that West Nile virus is a common zoonotic pathogen with public health implications. Moreover, both pathogens are instructive models in infectious disease ecology, and infection with either has fitness consequences for their avian hosts.Electronic supplementary materialThe online version of this article (doi:10.1186/1756-3305-7-415) contains supplementary material, which is available to authorized users.

Overlap in the Seasonal Infection Patterns of Avian Malaria Parasites and West Nile Virus in Vectors and Hosts

“…Actual coinfections are difficult to confirm with field data given the short viremic period associated with WNV infection. 36,64 However, in a previous study 36 we showed that seven of 23 hosts of the species included in this analysis that had an active WNV infection were also simultaneously infected with a Plasmodium parasite, demonstrating that coinfections occur in this population. We also found that Culex vector pools infected with a Plasmodium parasite had a higher probability of a WNV infection.…”

“…Previous studies have indicated that pathogen-pathogen interactions can have important impacts on disease transmission. 20 Indeed, ubiquitous avian Plasmodium infections may impact WNV transmission by influencing heterogeneity in host-vector interactions, 65,66 the viremia profiles and survival of coinfected hosts, 36 and the vectorial capacity of mosquitoes. 25 Furthermore, Plasmodium species have been shown to influence vector's biting behavior, [66][67][68][69] and this might impact circulation of arboviruses that have similar transmission cycles.…”

“…42 The independent lineages of these parasites have been discussed in previous studies. 36,43,44 We used avian serum from blood samples to test for the presence of WNV antibodies using an inhibition enzyme-linked immunosorbent assay (ELISA). 17,45 For Culex mosquitoes, DNA was extracted from pools of whole-bodied host-seeking female individuals that were collected from the same sites and at the same time.…”

“…A previous study identified a negative association between Plasmodium infection and WNV serostatus among avian hosts in this region. 36 The mechanisms for this negative association remain uncertain but one possibility is Plasmodium-WNV coinfection decreases host survivorship. An additional study from the same region demonstrated that Culex mosquitoes commonly ingest multiple hemoparasites while taking avian blood meals.…”

Exposure of Anopheles mosquitoes to trypanosomes reduces reproductive fitness and enhances susceptibility to Plasmodium

“…In areas with the highest malaria burden, such as in Sub-Saharan Africa, Plasmodium falciparum transmission depends on the complex ecological determinants (biotic and abiotic factors) that drive population dynamics of the primary African vectors Anopheles gambiae s.l. and A. funestus but also mosquito intrinsic factors for pathogen development [2][3][4][5][6][7]. Eukaryotic microbes, including microsporidia, gregarines and trypanosomatids, have been identified in mosquitoes.…”