Under stress conditions, pacu Piaractus mesopotamicus modulates the metabolic allostatic load even after Dolops carvalhoi challenge to maintain self-protection mechanisms

Fish metabolic allostatic dynamics, when animal present physiological modifications that can be strategies to survive, are important for promoting changes to ensure whole body self-protection and survival in chronic states of stress. To determine the impact of sequential stressors on pacu (Piaractus mesopotamicus), fish were subjected to two trials of stressful treatments, administration of exogenous dietary cortisol, and parasite challenge. The first experiment consisted of a two-day acute stress trial and the second, an eight-day chronic stress trial, and after both experiments, fish parasite susceptibility was assessed with the ectoparasite Dolops carvalhoi challenge. Physiological changes in response to acute trial were observed in glycogen, cortisol, glucose, osmolarity, sodium, calcium, chloride, potassium, hematocrit, hemoglobin, red blood cells and mean corpuscular volume, and white blood cell (P < 0.05), whereas response to chronic trial were observed in glycogen, osmolarity, potassium, calcium, chloride, mean corpuscular volume, white blood cell, neutrophil, and lymphocyte (P < 0.05). Acute trials caused physiological changes, however those changes did not induce the consumption of hepatic glycogen. Chronic stress caused physiological changes that induced hepatic glycogen consumption. Under acute trial, stress experience was important to fish to achieve homeostasis after chronic stress. Changes were important to modulate the response to stressor, improve body health status, and overcome the extra stressor with D. carvalhoi challenge. The experiments demonstrate that pacu initiate strategic self-protective metabolic dynamics in acute states of stress that ensure the maintenance of important life processes in front of sequential stressors.

Hematological alterations in Astyanax altiparanae (Characidade) caused by Lernaea cyprinacea (Copepoda: Lernaeidae)

This study describes the hematological alterations in Astyanax altiparanae associated with infestation with Lernaea cyprinacea. The study was carried out in a lagoon of the Mogi-Guaçu River, in the municipality of Pirassununga, in the state of São Paulo, Brazil. Of 46 fish examined, 45.6% had their integument infested by L. cyprinacea, with a mean intensity of 4.9 parasites per fish and a mean abundance of 2.2, giving a total of 139 recovered crustaceans. The abundance of L. cyprinacea correlated positively with the length and weight of the hosts, and the intensity of infestation was higher in female hosts. Macroscopic observation of lesions associated with the parasite showed a severe inflammatory reaction around the site of attachment of L. cyprinacea, associated with a lower relative condition factor and blood parameters. The hematocrit, number of red blood cells and thrombocytes were higher in non-parasitized than in parasitized fish. However, the hemoglobin concentration, hematimetric indices and the number of white blood cells were not influenced by infestation.

Stress response of Salmo salar (Linnaeus 1758) when heavily infested by Caligus rogercresseyi (Boxshall & Bravo 2000) copepodids

The year-round presence of ovigerous females of the parasite Caligus rogercresseyi in the fish farms of southern Chile results in a continuous source of the copepodid (infestive) stage of this louse. The short generation time in spring-summer could lead to high abundances of this copepodid, potentially leading to high infestation levels for fish. Knowing how heavy lice infestations affect Salmo salar can help determine how to time antiparasitic treatments so as to both minimize the treatment impact and reduce lice infestation levels for fish. This study aimed to describe the effects of high infestations of the copepodid stage of C. rogercresseyi on the physiology of S. salar. Two groups of S. salar were used: an infested group (75 copepodids per fish) and a control group (not infested). Sixty-five days after the first infestation, the infested fish group was re-infested at an infestation pressure of 200 copepodids per fish. Sampling was done prior to and following the second infestation, at 56 and 67 days (the latter 2 days following the second infestation). Several physiological variables were measured: cortisol (primary stress response) and glucose, proteins, amino acids, triglycerides, lactate, osmolality levels, and number and diameter of skin mucous cells (secondary stress responses). The plasma cortisol, glucose, and triglyceride levels were altered in the heavily infested fish, as was the diameter of skin mucous cells. These results suggest that heavy infestations of C. rogercresseyi lead to an acute stress response, metabolic reorganization, and increased mucus production in S. salar under heavy infestation conditions.

Nest ectoparasites increase physiological stress in breeding birds: an experiment

Parasites are undoubtedly a biotic factor that produces stress. Heat shock proteins (HSPs) are important molecules buffering cellular damage under adverse conditions. During the breeding season, blue tit Cyanistes caeruleus (L.) adults are affected by blood parasites, nest-dwelling parasites and biting flies, potentially affecting their HSP-mediated responses. Here, we treated females with primaquine to reduce blood parasites and fumigated nests with permethrin to reduce nest-dwelling parasites to test whether these treatments affect HSP60 level during the breeding season. Medicated females, but not controls, had a significant reduction of the intensity of infection by Haemoproteus spp. blood parasites. However, final intensity of infection did not differ significantly between groups, and we did not find an effect of medication on change in HSP60 level. Fumigation reduced the abundance of nest-dwelling parasites (mites, fleas and blowfly larvae) and engorged biting midges in nests. Females breeding in non-fumigated nests increased HSP60 levels during the season more than those breeding in fumigated nests. Furthermore, the change in HSP60 level was positively correlated with the abundance of biting midges. These results show how infections by nest ectoparasites during the breeding period can increase the level of HSPs and suggest that biting midges impose physiological costs on breeding female blue tits. Although plausible, the alternative that biting midges prefer to feed on more stressed birds is poorly supported by previous studies.

Application of the analysis of serum antibodies (immunoglobulins M and G) to estimate the seroprevalence of ovine oestrosis and to evaluate the effect of chemotherapy

The analysis of immunoglobulin (Ig) M and IgG serum isotypes as indicators of the presence of Oestrus ovis developmental stages was carried out. A serological survey to discover the seasonal variations in the prevalence of oestrosis in sheep from an oceanic climate area was developed. Six hundred and sixty-nine blood samples were analyzed for the presence of IgM and IgG using an enzyme-linked immunosorbent assay and O. ovis second-stage larvae excretory/secretory antigens. In addition, the effect of an ivermectin-based treatment on the humoral immune response was measured. The percentage of positive animals was 54% for IgM and 55% for IgG. The highest percentages of sheep positive to IgM were recorded in the winter and to IgG in the summer. No animals positive to IgM were detected in the ivermectin-treated sheep. These results seem to underline that oestrosis is a parasitic disease to keep watch for in regions with an oceanic climate. A noninvasive evaluation of the success of chemotherapy seems possible by analyzing the serum IgM response.

Stress response of brown pelican nestlings to ectoparasite infestation

Measurement of corticosterone has become a useful tool for assessing the response of individuals to ecological stressors of interest. Enhanced corticosterone levels can promote survival of stressful events; however, in situations where a stressor persists and corticosterone levels remain elevated, the adrenocortical response can be detrimental. A potential ecological stressor for wild birds is parasitism by ectoparasites. We studied the stress response of 11-23-day-old brown pelican (Pelecanus occidentalis) nestlings by measuring plasma corticosterone levels in relation to the presence of the soft tick Carios capensis at two colonies in South Carolina in 2005. We expected to see higher baseline and stress-induced levels of corticosterone for parasitized chicks compared to those nestlings with no ticks. Although nestlings mounted a response to capture stress, tick category was not associated with corticosterone levels at either colony. Our results appear to contrast those of previous studies and indicate that the adrenocortical response of the host is likely dependent on the type of ectoparasite and the degree of infestation.

A mixed ectoparasite--microparasite model for bat-transmitted rabies

This paper considers the transmission of rabies to domestic livestock by vampire bats. Vampire bats act as ectoparasites on cattle both by ingesting a small amount of blood every night and by prolonging bleeding by the action of anticoagulant substances in their saliva. In addition to this parasitic action bats may also transmit rabies, inflicting important losses on affected herds by the inevitable mortality due to the infection. We modeled this complex interaction and we also demonstrate that bat control measures are more effective in reducing rabies prevalence and mortality by rabies than cattle vaccination.

Physiological and haematological consequences of a novel parasite on the red-rumped swallow Hirundo daurica

Parasite virulence has been hypothesised to increase with the degree of host sociality because highly social hosts have a greater probability of encountering horizontal transmission of parasites and experiencing infections with multiple strains of the same parasites than do solitary hosts. As compared with the defences of closely related social host species, we predicted that solitary hosts should have relatively weak defences against parasites, thus being relatively more affected when parasitised by a novel parasite. We tested this prediction by either experimentally infesting 12 nests of the solitarily nesting red-rumped swallow Hirundo daurica with 50 individuals of the generalist martin bug Oeciacus hirundinis or by fumigation of nine nests. Nestlings 13 days old from the parasite addition group experienced increased mortality, attained lower body mass and tended to have shorter tarsi compared to nestlings from fumigated nests. Surprisingly, nestlings from the parasite addition group had higher packed cell volume (cellular fraction of blood) and lower levels of heat shock proteins (HSP60) than nestlings from the fumigation group. A measure of immunocompetence was not significantly affected by treatment, but its magnitude was positively related to packed cell volume and negatively related to level of HSP60. Solitary hosts like the red-rumped swallow have weak immune responses and low levels of heat shock proteins when infested with ectoparasites while highly social hosts have strong immune responses and high levels of heat shock proteins when infested. These findings partially support the hypothesis that potential host species with weak defences are more susceptible to infection and the deleterious effects of evolving parasites than potential hosts with strong defences.

Changes in physiological parameters and feeding behaviour of Atlantic salmon Salmo salar infected with sea lice Lepeophtheirus salmonis

Atlantic salmon Salmo salar L. artificially infected with salmon lice Lepeophtheirus salmonis (Krøyer 1837) recovered from detrimental physiological changes and skin damage induced by preadult lice as the parasites matured. Growth rates of Atlantic salmon remained unaffected by lice infection, but food consumption decreased with increasing feeding and movement of the lice prior to and post-mating, correlating with the appearance of head erosions and detrimental changes in physiological integrity. Food consumption of the fish increased as the lice moulted to the adult stage and gravid female lice settled in a posterior location on the fish, subsequently reducing the impact of infection and allowing recovery of the skin damage. However, the impact of preadults was limited, as the decrease in food consumption of fish at 21 d post-infection had no effect on either the specific growth rate or condition factor of the fish. Furthermore, the intensity of lice infections at each of the sample days was not correlated with food consumption, specific growth rate or any of the haematological or physiological parameters measured, either before or after infection, indicating that lice intensity was independent of social dominance/subordinance. This work has provided the first evidence that infected fish can recover from the detrimental changes caused by lice infection, even when they are still infected with lice. If fish can survive the preadult stage of lice, then the mortal impact of lice infections is greatly reduced.

[The dynamics of the ectoparasite count and the protein level in the blood serum of infested carp under experimental conditions]

Carps of one and two years age used for laboratory experiments were collected in winter time. 7 groups of carps of one year age were examined each 10th day during 70 days and 5 groups of two years age were examined each 15 days during 75 days. In carps of one year age the increase of different parasites was observed in different time: Dactylogyrus extensus--after 40 and 70 days, Icthyophthirius multifiliis--after 50 days, Trichodina sp.--after 60 days. In carps of two years age the increase of all parasite groups observed after 45 days, extremely great number of D. extensus was recorded after 60-70 days. Contents of proteins in a blood plasma of both age groups of carps is reliably decreased when the number of parasites is increased. Fluctuations of parasite abundance on the body and gills and some morphophysiological indices in carps of one year age in a control and in conditions of starvation were examined.

Plasma characteristics of beef cattle classified as resistant or susceptible to horn flies

Horn flies inflict economic losses on cattle producers. Therefore, the objective of this study was to identify a serological marker for cows that are innately resistant to horn flies. Plasma characteristics (optical density, cortisol, and protein pattern) were studied in beef cattle classified (cow-type) as horn fly resistant or susceptible. Cows (n = 30) of five breed groups were used in this study. Cows were bled via jugular venipuncture in May (the beginning of the horn fly season). Plasma optical density at wavelengths 200 and 464 nm was different (P < .05) between resistant and susceptible cattle. Cow-type also affected (P < .05) area percentage for proteins with running molecular weights (M(r)) of 74,000 and 54,000 daltons. Breed group affected (P < .05) optical density at wavelengths 200, 280, 320, and 464 nm and concentration of cortisol in plasma. When the ratio of area percentage for protein bands 7 and 9 (M(r) 74,000 and 54,000, respectively) was determined, cows could be categorized as horn fly resistant or susceptible. These data suggest that a serological marker for horn fly resistant cattle has been identified; however, the marker will need to be tested on a larger population of cattle.

Ectoparasite impacts on Gerbillus andersoni allenbyi under natural conditions

To assess ectoparasite impact on individuals and populations of Gerbillus andersoni allenbyi under natural conditions, I addressed the following questions. Do ectoparasites affect their host fitness and, if so, how? Do ectoparasites affect host population level? Does this parasite-host interaction support the traditional concept of parasite evolution towards avirulence? For this purpose, host infestation, infection, survival, haematological indices, and physical condition were recorded. A field experiment which included manipulating host infestation while recording host survival was conducted to determine the causal relations between these variables. G. a. allenbyi was infested by 2 fleas (Synosternus cleopatrae and Stenoponia tripectinata), 5 mesostigmatid mites (Androlaelaps centrocarpus, A. hirsti, A. insculptus, A. marshalli and Hirstionyssus carticulatus), 1 tick (Rhipicephalus sanguineus), and 1 louse (polyplax gerbilli). Ectoparasite burden significantly reduced host survival and red blood cell indices (red cell concentration, haemoglobin concentration and haematocrit). Ectoparasite burden did not significantly affect white blood cell concentration. Gerbils were not infected by haemoparasites or gut helminths which potentially could cause anaemia. The causal relationship between S. cleopatrae burden and host survival was established by manipulation of host infestation. Both ectoparasite removal and initial level of infestation significantly affected host survival. Ectoparasites that caused anaemia were not associated with host physical condition (PC), measured as weight/length3. None of the red blood cell indices was correlated with host PC. These results suggest both that host PC was not affected by ectoparasite burden and that exsanguination leading to anaemia was the main effect of the ectoparasites. Ectoparasite pressure on the host population (based on the ectoparasite effects as estimated by statistical models, combined with dispersion of the infestation within the host population) changed seasonally and was greatest when host density was the highest. A large segment of the gerbil population was affected by ectoparasites during the entire year. An explanation for the evolution of parasite virulence, contrasting parasites that evolve towards increased virulence with parasites that evolve towards avirulence is presented. This classification is primarily based on whether parasite impact is equated with a higher efficiency of host exploitation, or whether it is a 'side effect' of parasite biology.

Mortality in calves, lambs and kids caused by severe infestation with the cat flea Ctenocephalides felis felis (Bouché, 1835) in Israel

Heavy infestation of calves, lambs and kids with the cat flea Ctenocephalides felis felis (Bouché, 1835), accompanied by severe anaemia and mortality, is described. Lambs and kids were affected more severely than calves. Flea infestation was more widespread in summer and autumn than in winter and spring. The clinical findings are discussed in the light of the pertinent literature.

Blood leukocyte response in hosts parasitized by the hematophagous arthropods Triatoma protracta and Lutzomyia longipalpis

The kinetics of peripheral blood basophil and eosinophil responses in guinea pigs to multiple infestation by nymphal and adult Triatoma protracta (vessel feeder) and adult Lutzomyia longipalpis (pool feeder) were examined. Hosts exhibited significant blood basophil and eosinophil responses to feeding by both arthropods. Basophilia was slow to develop and mild in intensity following primary Triatoma infestation but exhibited immediate anamnestic-type responses to secondary infestation, with marked but delayed-type responses to tertiary infestation. Basophilia developed quickly in guinea pigs infested with Lutzomyia, and this response remained fairly consistent throughout the three infestation periods. Eosinophils did not respond to primary Triatoma infestation but exhibited marked immediate responses to both secondary and tertiary infestations. Lutzomyia-infested hosts exhibited marked eosinophilia in response to all infestations. Eosinophil levels returned to control levels 10 days post-tertiary infestation in Triatoma hosts, whereas Lutzomyia hosts exhibited normal eosinophil levels within 3-4 days after peak response. This study demonstrates that hosts respond to fast-feeding hematophagous arthropods with a peripheral blood basophilia and eosinophilia, as reported for slow-feeding (ticks) hematophagous arthropods. The difference in feeding strategy, whether vessel or pool feeder, appears to be reflected by differences in host blood leukocyte kinetics in response to parasitization by specific arthropods.

Ctenocephalides canis infestation of sheep and goats

An investigation into infestation of sheep and goats with Ctenocephalides canis showed that while only a light degree of infestation was observed in the affected goats, light to heavy degrees of infestation occurred in sheep. In both species a light degree of infestation had no marked effect on the packed cell volume (PCV). Both medium and heavy degrees of infestation resulted in a significant lowering of the PCV of the affected sheep.

Glochidiosis of salmonid fishes. IV. Humoral and tissue responses of coho and chinook salmon to experimental infection with Margaritifera margaritifera (L.) (Pelecypoda: Margaritanidae)

Coho salmon (Oncorhynchus kisutch) are more resistant than chinook salmon (O. tshawytscha) to experimental infection with the glochidia of the freshwater mussel Margaritifera margaritifera. Histological sections of gills from coho salmon 16 hr postinfection (p.i.) showed that parasite encystment either did not occur or had progressed incompletely, which accounted for the loss of many glochidia from the gills. The remaining encysted glochidia were sloughed within 2 days (p.i.) by a well-developed hyperplasia. On chinook salmon, the parasites developed normally with no sloughing or hyperplasia. Analysis of blood samples taken from coho salmon at intervals during the infection showed significant increases in hematocrit, hemoglobin, the mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and leukocyte numbers when compared with control fish. In infected chinook salmon only the hematocrit, erythrocyte numbers, and MCV increased while the MCHC decreased. Total plasma protein increased in coho salmon but decreased in chinook salmon during infection. Glochidial antibodies were demonstrated in the blood plasma of coho and chinook salmon 8 to 12 wk p.i. Fewer glochidia attached to the excised gills of coho salmon than to the gills of chinook salmon. Also, the in vitro survival time of parasites in mucus and plasma from coho salmon was less than in the same chinook salmon fluids.

Haematological changes in fowls infested with black flies (Simulium griseicolle)

The effect of Simulium griseicolle on the blood of growing and laying birds was studied for periods of 10 and eight weeks respectively. The red cell counts and the haemoglobin concentrations were reduced but the mean corpuscular volume was increased. The packed cell volume and the mean corpuscular haemoglobin concentration were only slightly changed. The macrocytic normochromic anaemia thus observed in the infested birds might have been due to nutritional factors rather than to blood loss caused by the feeding insects. Morphological changes were observed in the erythrocytes of the infested birds and these suggest presence of in vivo haemolysis, probably caused by some haemolysing agents in the saliva of the insects.