Hormonal and behavioral changes induced by acute and chronic experimental infestation with Psoroptes cuniculi in the domestic rabbit Oryctolagus cuniculus

A novel cystatin in Psoroptes ovis var. cuniculi: molecular characterization, serodiagnostic potential, and its anti-inflammatory property on rabbit peripheral blood mononuclear cells

BACKGROUND

The ectoparasite Psoroptes ovis var. cuniculi causes substantial economic losses to the global rabbit industry. Currently, microscopy for identifying Psoroptes mite in skin scrapings, as the "diagnosis gold standard," remains a challenge owing to its poor sensitivity in detecting low-level and/or early stage mite infestations. Additionally, Psoroptes infestations rapidly trigger cutaneous inflammation, thus the mites might produce some molecules to deal with the harmful effects of inflammation for their long-time survival on the host skin, but these molecules are still mostly unknown.

METHODS

To seek a sensitive diagnostic method and illuminate the new antiinflammatory molecules, we characterized a novel cystatin of P. ovis var. cuniculi (PsoCys) using bioinformatics and molecular biology methods.

RESULTS

The results showed that PsoCys comprised the classical features of the type II cystatin superfamily including an N-terminal glycine residue, a central QXVXG motif, and a C-terminal LW motif. In mixed stages of mites, the transcription level of PsoCys was significantly higher in "fed" mites than in "starved" mites (P < 0.001), and among the different life-cycle stages of "fed" mites, the expression of PsoCys was higher in adult males than in larva, nymph, and adult females (P < 0.001). The established indirect ELISA based on recombinant PsoCys (rPsoCys-iELISA) presented 95.4% sensitivity and 95.7% specificity. The area under the receiver operating characteristic curve (AUC) for this method was 0.991, indicating its excellent diagnostic performance. Moreover, rPsoCys-iELISA had advantages over microscopy for detecting low-level and/or early stage mite infestations (90% versus 40% in artificial infestation cases at 3 weeks post-infestation; 61.9% versus 22.6% in clinical cases). In addition, rPsoCys could inhibit the activity of papain and cathepsin B in vitro, and significantly suppressed mRNA levels of toll-like receptors (TLR 1, 2, 4, and 6) and downstream molecules (NF-κB, p38, MyD88, IL-10, and IFN-γ) in LPS-stimulated rabbit PBMCs, indicating its anti-inflammatory property.

CONCLUSIONS

Our findings indicated that PsoCys was a novel type II cystatin of Psoroptes mites, and it served as a potential serological diagnostic antigen for detecting low-level and/or early stage mite infestations, as well as a novel anti-inflammatory molecule of Psoroptes mites.

Effect of infestation with Psoroptes cuniculi on reproduction and behavior of obese rabbit does (Oryctolagus cuniculi)

Parasites and obesity are health problems worldwide. Rabbits are production animals yielding one of the healthiest meats, also taking advantage of skin, hair, limbs and excreta. It is among the most frequent pets in some countries and widely used as animal model in research. Psoroptes cuniculi is a mite of high transmission rate, affecting welfare and production and obesity causes multiple metabolic, endocrine and immunological disorders, being an emerging problem in domestic animals. Obesity and acarosis are prolonged stressors, modifying the activity of the hypothalamic-pituitary-adrenal axis that can induce metabolic and behavioral disorders. Alterations caused by comorbidities could be similar to or different from those induced by each morbidity separately. We analyzed the influence of obesity on the infection degree with P. cuniculi and on behavior and production. Rabbit does induced to obesity were infected and mated; behaviors in the open field test, obesity estimation indices and productive parameters at delivery and weaning were analyzed. The acarosis induced a decrease in feed intake and a decrease in body weight, a decrease in locomotor, exploratory and chinning behaviors in normal weight and obese does. The infection induced 23% mortality at birth, obesity 45% and comorbidity 74%, while in normal weight rabbits a 6.5% was observed. Weight gain from birth to weaning was lower in the comorbid group, reaching a litter weight of 4.5±0.13 kg in healthy normal weight does and 2.6±0.67 kg in comorbid does. The disturbances induced by the comorbidity were magnified in both behavioral and productive parameters.

Mate choice is affected by parasite infestation rate of the choosing individual as well as of potential mating partners

Parasites are known to be a key driving force in mate choice and are important for the expression and evolution of ornaments and behavioral traits being used. However, there is little experimental evidence on how the parasite's burden of the choosing individual is integrated into the mate-choice process and how it affects decision-making, especially in relation to parasite infestation of potential mates. Thus, the aim of our study was to determine whether female house sparrows Passer domesticus adjust their mate preference according to their own as well as the parasite load of prospective partners. To do this, we experimentally manipulated female parasite load and determined their mate preferences prior to and after parasite treatment. We manipulated the chronic coccidian parasite burden of females either by initiating the acute infection phase via re-infecting them with coccidian or by temporally reducing the parasite load of coccidia. We then measured the effect of this manipulation on mate preference by presenting females with a choice of four stimuli: three males with similar ornaments, but unmanipulated, naturally varying chronic coccidiosis levels, and an unmanipulated control female. Additionally, we recorded some males' behavior in relation to their infection status pointing toward an increased or reduced interest in mating. We found that females preferred highly infested males prior to manipulation, regardless of their own infestation level. However, after manipulation, infested females avoided highly infested males probably in response to the deterioration of their health condition by parasites. Our study suggests that mate-choice decisions are more complex when they are mediated by parasites. The implications of parasites for evolutionary theories of sexual signaling and mate choice are discussed.

Effects of Taenia Pisiformis Infection and Obesity on Clinical Parameters, Organometry and Fat Distribution in Male Rabbits

Taenia pisiformis infection causes important economic loss in farms. It is suggested that obesity has a major impact on infection and reproduction. We addressed the impact of T. pisiformis infection in normal and obese rabbits to evaluate its effect on parameters important in behavior and reproduction. T. pisiformis infection in obese rabbits decreased body weight. In the obese-infected rabbits, eosinophils and heterophiles were increased 23% by the infection (P ≤ 0.05). T. pisiformis decreased cholesterol by 13% in normal weight infected rabbits and 10% in obese group (P ≤ 0.05), while triglyceride and VLDL were increased by 23% and 45% in the non-infected obese group (P ≤ 0.05). The infection increased serum cortisol levels only in normal weight rabbits (P ≤ 0.05). Liver weight was 20% higher in obese and obese-infected rabbits (P ≤ 0.05). Testicular weight in obese-infected was 46% higher than normal weight (P ≤ 0.0001) and 20% more than the obese-non-infected (P ≤ 0.0001). Furthermore, the infection reduced the weight of submandibular glands in infected and obese-infected rabbits (P ≤ 0.05), body fat increased 10% in the obese-infected than in the obese, and infected group was 35% over the normal weight non-infected (P ≤ 0.01). Our results show that T. pisiformis alters metabolic characteristics in rabbits, which can impact on the production and welfare of animals.

Patterns and variation in the mammal parasite-glucocorticoid relationship

Parasites are ubiquitous and can strongly affect their hosts through mechanisms such as behavioural changes, increased energetic costs and/or immunomodulation. When parasites are detrimental to their hosts, they should act as physiological stressors and elicit the release of glucocorticoids. Alternatively, previously elevated glucocorticoid levels could facilitate parasite infection due to neuroimmunomodulation. However, results are equivocal, with studies showing either positive, negative or no relationship between parasite infection and glucocorticoid levels. Since factors such as parasite type, infection severity or host age and sex can influence the parasite-glucocorticoid relationship, we review the main mechanisms driving this relationship. We then perform a phylogenetic meta-analysis of 110 records from 65 studies in mammalian hosts from experimental and observational studies to quantify the general direction of this relationship and to identify ecological and methodological drivers of the observed variability. Our review produced equivocal results concerning the direction of the relationship, but there was stronger support for a positive relationship, although causality remained unclear. Mechanisms such as host manipulation for parasite survival, host response to infection, cumulative effects of multiple stressors, and neuro-immunomodulatory effects of glucocorticoids could explain the positive relationship. Our meta-analysis results revealed an overall positive relationship between glucocorticoids and parasitism among both experimental and observational studies. Because all experimental studies included were parasite manipulations, we conclude that parasites caused in general an increase in glucocorticoid levels. To obtain a better understanding of the directionality of this link, experimental manipulation of glucocorticoid levels is now required to assess the causal effects of high glucocorticoid levels on parasite infection. Neither parasite type, the method used to assess parasite infection nor phylogeny influenced the relationship, and there was no evidence for publication bias. Future studies should attempt to be as comprehensive as possible, including moderators potentially influencing the parasite-glucocorticoid relationship. We particularly emphasise the importance of testing hosts of a broad age range, concomitantly measuring sex hormone levels or at least reproductive status, and for observational studies, also considering food availability, host body condition and social stressors to obtain a better understanding of the parasite-glucocorticoid relationship.

Prevalence, Morphological and Molecular Phylogenetic Analyses of the Rabbit Pinworm, Passalurus ambiguus Rudolphi 1819, in the Domestic Rabbits Oryctolagus cuniculus

INTRODUCTION

Passalurus ambiguus, a pinworm nematode parasite, infects domestic and wild rabbits, hares, and rodents worldwide.

MATERIALS AND METHODS

The current parasitological study was performed during January-December 2016, to investigate helminth parasites infecting the domestic rabbit species Oryctolagus cuniculus at the Department of Animal Production, Faculty of Agriculture, Cairo University, Cairo, Egypt.

RESULTS

Of the twenty rabbit specimens examined for gastrointestinal nematodes, 75% were infected with adult oxyurid species, which were morphologically characterized using light and scanning electron microscopy studies. The oxyurid species had a triangular mouth opening surrounded by simple lips with four cephalic papillae and a pair of lateral amphidial pores with three teeth-like structures, an esophagus divided into a cylindrical corpus and globular bulb supported internally with tri-radiate valvular apparatus, and four caudal papillae distributed on the posterior end of males with a single short protruding spicule and ovijector apparatus opening ventrally by the vulva, surrounded by protruded lips in female worms. The species were compared morphometrically with other Passalurus species described previously; light differences were found in different body part sizes. Molecular characterization based on 18 small subunit (SSU) rDNA sequences showed ~ 85% similarity with other Chromadorea species. A preliminary genetic comparison between the 18S rDNA sequences of the isolated parasite and those of other oxyurid species suggested that it belonged to Passalurus ambiguus. The 18S rDNA sequence of the parasite was deposited in GenBank (accession no., MG310151.1).

CONCLUSION

The 18S rDNA gene of P. ambiguus was shown to yield a unique genetic sequence that confirms its taxonomic position within the Oxyuridae family.

Behavioural and productive response to experimental infection with stage 3 larvae of Haemonchus contortus in feedlot bull-calves

Haemonchus contortus is a nematode parasite that establishes in the abomasum of ruminants, it has a cosmopolitan distribution and is a worldwide health problem for livestock. As a first line of defence against parasites, behaviour can help to prevent or fight infection, and may even serve as a method of early presumptive diagnosis. Parasites can affect performance of cattle and cause significant economic losses. The aim of this study was to determine the behavioural and productive changes induced by an experimental infection with H. contortus L3 in bovines. We used 32 dewormed bull calves, randomly divided into two groups, 8 no inoculated controls and 24 that were inoculated with 4000 L3 of H. contortus. Inoculation did not influence haematocrit or haemoglobin values at 0, 28 and 42 days post infection (P> 0.20); however, an increase in the frequency of urination (P = 0.0001) and defecation (P = 0.0001), number of steps (P < 0.001) and self-grooming (P < 0.01) events were observed, even in inoculated animals in which not parasite eggs were found in faeces. During the first 28 days post-inoculation with H. contortus, feedlot performance was not affected (P = 0.16), but during the last 14 days (29-42) inoculated animals gained 15% less weight compared to controls (P = 0.04). Over 42 days, inoculated calves showed a 28% poorer feed efficiency during the 42 days post-inoculation than controls (P < 0.01). Across the experiment, calves inoculated with H. contortus obtained less net energy both for maintenance as for gain from diet (P < 0.01). It is concluded that both, performance and behaviour were modified in feedlot bull-calves parasitized by H. contortus, supporting the practice of deworming when eggs of this parasite are detected in the faeces even in low amounts.

Biomarkers as predictive tools to test the in vivo anti-sarcoptic mange activity of propolis in naturally infested rabbits

The present study was designed to investigate the use of specific biomarkers, such as albumin, serum total protein, aspartate amino transferase (AST), globulin, alanine amino transferase (ALT), serum cortisol and alkaline phosphatase (ALP), as predictive tools for sarcoptic mange in rabbits. A total of 40 naturally infested rabbits were equally divided into four groups.Thirty infested rabbits were administered with three different treatments (propolis,ivermectin, and propolis with ivermectin) and were compared to10 infested un-treated rabbits. The impact of treatment was assessed via microscopic examination of skin scrapings, clinical signs, and blood measurements relating to the liver. The present study demonstrated that topical application of 10% propolis ointment resulted in complete recovery from clinical signs and complete absence of mites based on microscopic examination after 10-15 days of treatment. Moreover, AST, ALP, ALT, and cortisol were determined to be acceptable biomarkers to track the response of diseased rabbits to the therapeutic use of propolis.

Prolactin as immune cell regulator in Toxocara canis somatic larvae chronic infection

Toxocariasis is a zoonotic disease produced by ingestion of larval Toxocara spp. eggs. Prolactin (PRL) has been considered to have an important role in Toxocara canis infection. Recent evidence has found that PRL directly can increase parasite growth and differentiation of T. canis The present study, evaluated the effect of high PRL levels on the immune system's response and parasites clearance in chronic infection. Our results showed that hyperprolactinemia did not affect the number of larvae recovered from several tissues in rats. Parasite-specific antibody production, showed no difference between the groups. Lung tissue presented eosinophilic granulomas typical of a chronic infection in all the experimental groups. Flow cytometry analysis was made in order to determine changes in the percentage of innate and adaptive immune cell subpopulations in the spleen, peripheric (PLN) and mesenteric (MLN) lymphatic nodes. The results showed a differential effect of PRL and infection on different immune compartments in the percent of total T cells, T helper cells, T cytotoxic cells, B cells, NK cells, and Tγδ cells. To our knowledge, for the first time it is demonstrated that PRL can have an immunomodulatory role during T. canis chronic infection in the murine host.

Sarcoptes scabiei alters follicular dynamics in female Iberian ibex through a reduction in body weight

Normal development of the ovarian cycle is a key factor in ensuring female reproductive success. Sarcoptes scabiei has been shown to induce changes in host physiology, although the effects of this mite on the female reproductive cycle are still unknown. In an attempt to clarify this issue, the number of ovarian structures (primary follicles, secondary follicles, Graaf follicles, corpus luteum and corpus albicans) in female Iberian ibex (Capra pyrenaica) affected by sarcoptic mange was explored by histological analysis of samples taken from 102 females selectively harvested in the Sierra Nevada Natural Space, southern Spain. The effect of mange status, body weight (corrected for age), age and year of sampling on the number of ovarian structures was assessed using generalized linear models. Our results provide evidence that sarcoptic mange alters follicular dynamics through a reduction in host body weight, whose main consequences are noted in follicular maturation and ovulatory capacity.

Taenia pisiformis cysticercosis induces decreased prolificacy and increased progesterone levels in rabbits

Reproductive alterations in hosts infected by parasites have been recognized in several phyla, especially in arthropods and mollusks, but it has been less studied in higher vertebrates, particularly in mammals. In the present study, ten eight week-old female New Zealand rabbits (Oryctolagus cuniculus) were either infected with Taenia pisiformis eggs or uninfected, and 7 weeks later they were mated. We found that serum progesterone levels were increased during pregnancy in infected does. At birth, litter size of infected does was reduced by half as compared to the control group, and, at weaning, the number of kits and the weight of litters was lower. Since serum progesterone levels have a key role in the maintenance of pregnancy and implantation, we propose that the observed prolificacy alterations in does infected with T. pisiformis infection were due to changes in the levels of circulating progesterone during pregnancy.

Behavioral and hormonal changes associated with the infective dose in experimental taeniasis in golden hamsters (Mesocricetus auratus)

INTRODUCTION

It has been reported that behavioral changes relate to infection in different parasitoses. However, the relation between the extent of the behavioral changes and the magnitude of the infection has been scarcely studied. The aim of this study was to evaluate the relationship between different doses of infection and the behavioral changes induced in the experimental Taenia pisiformis taeniasis in golden hamsters.

METHODS

Groups of nine hamsters were infected with three or six T. pisiformis metacestodes. The locomotor activity was quantified daily in an open field test during the 21 days after infection; anxiety test was performed in an elevated plus-maze with a dark/light area at 7, 14 and 21 days post-infection, and serum cortisol levels were determined by radioimmunoassay before infection and at day 22 after infection.

RESULTS

The challenge itself induced modifications on behavior and cortisol levels in hamsters, with or without successful infection (taenia development). Animals challenged with three metacestodes induced a decrease in locomotor activity and an increase in anxiety in infected animals. A higher and earlier decrease in locomotor activity and increased anxiety levels were observed in hamsters challenged with six cysticerci, which were accompanied by higher levels of sera cortisol at the end of the experiment. At necropsy, 44-55% of hamster became infected with an efficiency of implantation of 22-26%, challenged with three or six cysticerci respectively.

CONCLUSION

The challenge of hamsters with metacestodes, promote behavioral changes in an extent dependent on the magnitude of the challenge, disregarding the effectiveness of the infection.

Morphologic and Genotypic Characterization of Psoroptes Mites from Water Buffaloes in Egypt

Species delimitation of Psoroptes spp. and identity of the parasite in water buffaloes remain poorly defined. In this study, Psoroptes infestation on three water buffalo farms in Egypt was examined based on morphometric characteristics, especially the opisthosomal setae of adult male mites. Clinical investigations showed that 28% (196/700) of the sampled animals had mange infestation. Microscopic examinations of 80 skin scrapings indicated the occurrence of Psoroptes mites in 17 (21.3%) samples, Sarcoptes mites in 27 (33.7%) samples, and the concurrence of both in 36 (45.0%) samples. Morphologically, the Psoroptes parasite was identified as Psoroptes natalensis. DNA sequence analysis of the second internal transcribed spacer (ITS2) in 11 representative samples confirmed the diagnosis and suggested the presence of a distinct variety of Psoroptes natalensis in Egypt.