Patterns of avian malaria in tropical and temperate environments: testing the "The enemy release hypothesis"

Abstract

According to the enemy release hypothesis (ERH) the spread of invasive species will be facilitated by release from their enemies as they occupy new areas. However, the ERH has rarely been tested by comparing populations of native (non-invasive, long established) species with expanding or shifting ranges, to the same species as invasive in another area. We tested the ERH with respect to blood parasite levels (prevalence and intensity of Plasmodium spp. and Haemoproteus spp.) of (a) two closely related, widely distributed species of thrush (Turdus leucomelas and T. merula), and (b) an invasive sparrow (Passer domesticus) whose range has expanded from the Old World to the New World since the 18th century. A total of 158 birds were sampled in Portugal and 99 in Brazil. All bird species were parasitized, and 55% of the individuals collected were parasitized, and the mean intensity of infection was of 28 parasites per 10,000 erythrocytes. We assessed whether differences in levels of infection (prevalence and intensity) were due to site (tropical/New World and temperate/Old World) or host species. The ERH was supported: Passer domesticus and Turdus merula had higher levels of parasitism in the Old World than in the New World. Thus, P. domesticus seems to be benefitting from its "recent" range expansion, compared to T. leucomelas, through ecological release from its native parasites and because the parasites of the recently invaded area seem to be infesting native species instead.

Prevalence of Haemosporidian parasites of Chukar Partridge Birds in Sulaimani Province/Kurdistan Region of Iraq

“…In the present study, Plasmodium, and Haemoproteus protozoan parasite were identified in partridges. Out of the total examined birds (100) in this study, 60(60%) were infected at least with one of the protozoan parasite this result concurs with prevalence reported by (28) that was (60%), and was relatively high compared to that previously reported (32.9%, 3.91%) from southern Iran (29,30), (7.7%) in Iraq (31), (5.9%) in Japan (32) and (6.2%) in Bulgaria (33).The high prevalence rate of blood parasites (60%) in the studied regions of Sulaimani Province, North of Iraq, maybe due to appropriate environmental conditions for vectors as well as the large population of free-ranging poultry in the area where they kept in free-range systems or on pastures are more exposed to vectors. Forty six samples (46%) were diagnosed to be infected with Plasmodium spp.…”

Host migration and environmental temperature influence avian haemosporidians prevalence: a molecular survey in a Brazilian Atlantic rainforest

“…Prevalence may increase with age of host, since older individuals tend to have higher infection risk as a result of accumulated exposure to parasites or potentially immunosenescence (Atkinson et al, 1995;Ricklefs et al, 2005;Wood et al, 2007;Eastwood et al, 2019). However, this relationship is not consistent among studies and is not always observed, which may be indicative that it depends on the parasite and host species studied (Wood et al, 2007;Antonini et al, 2019). Shape and height of birds nest may also influence haemosporidian prevalence, nest height must be associated with the spatial feeding preferences of vectors when seeking hosts, while its shape must determine the birds' exposure to vectors (Cerný, Votýpka & Svobodová, 2011;Fecchio et al, 2011;González et al, 2014;Lutz et al, 2015;Matthews et al, 2015).…”

Environmental, geographical and time‐related impacts on avian malaria infections in native and introduced populations of house sparrows (Passer domesticus), a globally invasive species

“…To our knowledge, general patterns of infections have rarely been characterized in the same focal bird species as in the current study (but see Colautti et al, 2005). Indeed, few studies have compared the haemosporidian parasite infections in native and introduced populations within the same host species at a regional (Ishtiaq et al, 2006; Lewicki et al, 2014), inter‐continental (Antonini et al, 2019; Clark et al, 2015; Lima et al, 2010; Marzal et al, 2018; Prüter et al, 2020) or global scale (Marzal et al, 2011).…”