Haematozoa infections in a Great TitParus majorpopulation in Central Portugal: relationships with breeding effort and health

Abstract

Blood parasites may act as modulators of their hosts' ecology, life histories and fitness. We studied the prevalence of Plasmodium sp., Haemoproteus sp. and Leucocytozoon sp. and their effects on morphological, biochemical and haematological variables and on breeding effort of Great Tits Parus major. Total prevalence (percentage of individuals infected by any parasite) ranged from 7.7% to 61.1%. There was an overall positive association in prevalence between the three haematozoan parasites. No effect of sex or age on infection status was observed. Negative impacts of infection on physiological condition depended largely on year and ⁄ or season and included effects on body condition index, plasma protein and haemoglobin index. There were also indications that parasite infection increased immune response and stress levels and activated antioxidant defence mechanisms. Males with higher fledging success had a higher probability of Haemoproteus infection, and females laying heavier eggs had a higher probability of Plasmodium infection. However, clutch size was negatively associated with the probability of infection by Leucocytozoon and Haemoproteus. Surprisingly, males raising second broods had a lower prevalence of both Haemoproteus and Leucocytozoon. Only 5.7% of first-brood nestlings were infected, but those in infected nestboxes had a lower heterophil ⁄ lymphocyte ratio. This study confirms the pathogenicity of blood parasites to the host by demonstrating negative effects of infection on both physiology and breeding performance.

Avian haemosporidian prevalence and its relationship to host life histories in eastern Tennessee

“…Similarly, infection status could be influenced by sex, with males experiencing higher susceptibility to parasites, possibly as a result of the energetic trade-off between immunocompetence and reproductive effort (Norris et al 1994;Richner et al 1995;Zuk and McKean 1996). Norte et al (2009) suggested that females experience more costly energetic constraints on immune function during the incubation period, while males experience depressed immune function during the brood-rearing period. Such partitioning of reproductive investment could influence the appearance of malaria infections in the circulating blood.…”

“…Such partitioning of reproductive investment could influence the appearance of malaria infections in the circulating blood. Infection status may also be influenced by body condition, with infection or failure to control infection more likely among birds in poorer condition (Dawson and Bortolotti 2000;Norte et al 2009). …”

Haemosporidian infections affect antioxidant defences in great tits Parus major but are not related to exposure to aerial pollutants

“…Haemosporidian prevalence usually increases in spring in temperate regions (Hatchwell et al 2000;Norte et al 2009), and an autumn peak may also be observed (Cosgrove et al 2008). In this study, we found that haemosporidian prevalence had a different pattern, being lower in spring, intermediate in autumn and higher in winter.…”

“…The increase of glutathione peroxidase activity may be one protective action to recover from the potential unbalance in oxidative status (Meister and Anderson, 1983). Our previous study, in a nearby mixed deciduous woodland, also showed that both Plasmodium and Leucocytozoon infected great tits had significantly higher glutathione peroxidase activity (Norte et al 2009). Isaksson et al (2013) also reported that the levels of total and oxidized glutathione in great tits were significantly affected by the Plasmodium infection status, which could be related with the activity of glutathione peroxidase (Meister and Anderson, 1983).…”

“…They can also affect other life history traits such as decrease the breeding success of hosts (Merino et al 2000;Marzal et al 2005;Valkiunas, 2005;Asghar et al 2015). Reported effects of their infection on health status in the wild include decrease in body mass and condition (Figuerola et al 1999;Garvin et al 2006;Valkiunas et al 2006;Norte et al 2009), decrease in total plasma proteins (Norte et al 2009), decrease in haemoglobin levels (Norte et al 2009;Krams et al 2013), increase in total white blood cell (WBC) counts (Figuerola et al 1999;Norte et al 2009), modification of the leucocyte profiles (Ots and Hõrak, 1998;Fokidis et al 2008;Norte et al 2009), decrease in T-cell-mediated response to phytohemagglutinin (PHA response; Navarro et al 2003) and increase in circulating immunoglobulin levels (Ots & Hõrak, 1998). However, the magnitude of those effects depends on the degree of co-evolution between the parasite and host and is also linked to environmental conditions (Lindström et al 2005).…”