Does sunlight enhance the effectiveness of avian preening for ectoparasite control?

Evaluation of the antiparasitic activity of the chitosan-silver nanocomposites in the treatment of experimentally infested pigeons with Pseudolynchia canariensis

This study aimed to evaluate the efficacy of chitosan-silver nanocomposites in the treatment of experimentally infested pigeons with Pseudolynchia canariensis (P. canariensis) with evaluation of different immunological parameters before and after treatment. Therefore, fourteen birds were divided into 2 groups; group1(infested group including 12 birds) which subdivided into 6 sub-groups experimentally infested pigeons 2 pigeons each, and five group of them were treated with chitosan-silver nanocomposites and sub-group number 6 was treated with deltamethrin while, group 2 including two pigeons were kept as control negative ones. P. canariensis flies distributed under the wing and /or under the tail in infested group and these pigeons showed significantly lower RBCs and higher WBCs than that in non-infested pigeons. The cell mediated immune response against experimentally infested pigeons with P. canariensis was studied. P. canariensis infestation in pigeons have a negative impact on pigeon’s blood parameters, increase TNF-α and IL-1β cytokines levels. This study cleared out the role of P. canariensis in the induction of a case of oxidative stress indicated by high level of nitric oxide and malondialdehyde (MDA) with low antioxidant capacity in shape of reduced zinc concentration in the sera of experimentally infested pigeon. Chitosan-silver nanocomposite has a promising effect in the elimination of P. canariensis infestation in pigeons.

Anti-parasite behaviour of birds

Birds have many kinds of internal and external parasites, including viruses, bacteria and fungi, as well as protozoa, helminths and arthropods. Because parasites have negative effects on host fitness, selection favours the evolution of anti-parasite defences, many of which involve behaviour. We provide a brief review of anti-parasite behaviours in birds, divided into five major categories: (i) body maintenance, (ii) nest maintenance, (iii) avoidance of parasitized prey, (iv) migration and (v) tolerance. We evaluate the adaptive significance of the different behaviours and note cases in which additional research is particularly needed. We briefly consider the interaction of different behaviours, such as sunning and preening, and how behavioural defences may interact with other forms of defence, such as immune responses. We conclude by suggesting some general questions that need to be addressed concerning the nature of anti-parasite behaviour in birds.This article is part of the Theo Murphy meeting issue 'Evolution of pathogen and parasite avoidance behaviours'.

Behavioral and hematological responses of broiler chickens administered with betaine and ascorbic acid during hot-dry season

Heat stress is a major problem in poultry production in tropical regions. Assessing the impact of thermally stressful environmental conditions on the welfare of broiler chickens is of great importance. Behavioral responses in a novel environment and hematology of broiler chickens administered with betaine and/or ascorbic acid (AA) during the hot-dry season were evaluated. Broiler chickens were randomly divided into four groups: Group I (control) was given sterile water, Group II was given betaine, Group III was given AA, and Group IV received betaine + AA orally and daily for 42 days. An open-field test was used to assess behavior. Hematological parameters were obtained using a hematology auto-analyzer. The natural environmental conditions were predominantly outside the thermoneutral zone for broiler chickens. Results demonstrated that treated groups exhibited improved ability to adjust faster to a new environment and better hematological responses than controls, evidenced by enhanced behavioral responses, oxygen-carrying capacity, and immune responses of broiler chickens under unfavorable environmental conditions. Betaine and/or AA administration to broiler chickens improved some behavioral responses, hemoglobin concentrations, packed cell volume, and total leukocyte count during the hot-dry season.

Relationships between beak condition, preening behavior and ectoparasite infestation levels in laying hens

The effects of beak condition on ectoparasite populations and preening in laying hens were investigated. Beak-trimmed and beak-intact caged Hy-Line W-36 hens were infested with either chicken body lice or northern fowl mites using a 2×2 factorial design with 4 replicate cages (each containing 2 hens)/treatment: 1) BTL: (beak-trimmed lice-infested); 2) BTM: (beak-trimmed mite-infested); 3) BIL: (beak-intact lice-infested); and 4) BIM: (beak-intact mite-infested). Mite scores and lice numbers were estimated weekly. Hens were video recorded the wk before infestation and at wk 6 and 9 post-infestation. Time spent preening on 6 body areas and in total were analyzed using a repeated measures ANOVA. There was a wk×beak condition interaction for lice loads, with BTL harboring approximately 17 times more lice than BIL from wk 7 to 10 post-infestation (P<0.0001). Beak condition affected mite loads (P<0.0001), with BTM having a higher mite score (3.8±0.26) than BIM (1.4±0.26). At peak infestation, BTL spent more total time preening (P=0.02, s±SE: 232.1±37.6) than prior to infestation (33.9±37.6) and directed their preening behavior towards the vent. In contrast, BIL (73.9±37.6), BTM (9.4±1.6), and BIM (8.6±1.6) did not increase total time spent preening over pre-infestation levels (103.6±37.6, 5.8±1.6, 6.7±1.6 respectively), although BTM did redirect their preening behavior toward the vent. This study confirmed previous studies showing that an intact beak is important for reducing ectoparasite infestations. Preening behavior increased in response to lice infestation, but only in beak-trimmed hens; preening behavior and louse load were correlated at peak infestation. In contrast, mite infestation did not lead to increased preening, and there was no correlation between preening and mite load. However, both lice- and mite-infested hens directed preening behavior predominantly towards the vent where these parasites are typically found.

An experimental test of the effects of behavioral and immunological defenses against vectors: do they interact to protect birds from blood parasites?

Background

Blood-feeding arthropods can harm their hosts in many ways, such as through direct tissue damage and anemia, but also by distracting hosts from foraging or watching for predators. Blood-borne pathogens transmitted by arthropods can further harm the host. Thus, effective behavioral and immunological defenses against blood-feeding arthropods may provide important fitness advantages to hosts if they reduce bites, and in systems involving pathogen transmission, if they lower pathogen transmission rate.

Methods

We tested whether Rock Pigeons (Columba livia) have effective behavioral and immunological defenses against a blood-feeding hippoboscid fly (Pseudolynchia canariensis) and, if so, whether the two defenses interact. The fly vectors the blood parasite Haemoproteus columbae; we further tested whether these defenses reduced the transmission success of blood parasites when birds were exposed to infected flies. We compared four experimental treatments in which hosts had available both purported defenses, only one of the defenses, or no defenses against the flies.

Results

We found that preening and immunological defenses were each effective in decreasing the survival and reproductive success of flies. However, the two defenses were additive, rather than one defense enhancing or decreasing the effectiveness of the other defense. Neither defense reduced the prevalence of H. columbae, nor the intensity of infection in birds exposed to infected flies.

Conclusions

Flies experience reduced fitness when maintained on hosts with immunological or preening defenses. This suggests that if vectors are given a choice among hosts, they may choose hosts that are less defended, which could impact pathogen transmission in a system where vectors can choose among hosts.

How effective is preening against mobile ectoparasites? An experimental test with pigeons and hippoboscid flies

Birds combat ectoparasites with many defences but the first line of defence is grooming behaviour, which includes preening with the bill and scratching with the feet. Preening has been shown to be very effective against ectoparasites. However, most tests have been with feather lice, which are relatively slow moving. Less is known about the effectiveness of preening as a defence against more mobile and evasive ectoparasites such as hippoboscid flies. Hippoboscids, which feed on blood, have direct effects on the host such asanaemia, as well as indirect effects as vectors of pathogens. Hence, effective defence against hippoboscid flies is important. We used captive Rock Pigeons (Columba livia) to test whether preening behaviour helps to control pigeon flies (Pseudolynchia canariensis). We found that pigeons responded to fly infestation by preening twice as much as pigeons without flies. Preening birds killed twice as many flies over the course of our week-long experiment as birds with impaired preening; however, preening did not kill all of the flies. We also tested the role of the bill overhang, which is critical for effective preening against feather lice, by experimentally removing the overhang and re-measuring the effectiveness of preening against flies. Birds without overhangs were as effective at controlling flies as were birds with overhangs. Overall, we found that preening is effective against mobile hippoboscid flies, yet it does not eliminate them. We discuss the potential impact of preening on the transmission dynamics of blood parasites vectored by hippoboscid flies.