A Giant Scrotal Neurofibroma in a Child Masquerading as Filariasis: Uncommon Presentation of a Common Disease.

Neurofibroma of the scrotum is a very uncommon benign neoplasm, specifically when it affects teenagers and is not associated with neurofibromatosis type I. To the best of our knowledge, only a couple of cases of neurofibroma in children have been documented. Here, we report a case study of a 17-year-old boy who had a giant scrotal lump for ten years masquerading clinically as filariasis. A provisional diagnosis of benign nerve sheath neoplasm was made based on cytology findings. The lump was surgically removed from the patient, and a histopathological and immunohistochemistry examination established the diagnosis of neurofibroma. The combined clinical, preoperative cytological, histological, and immunohistochemistry findings were not presented in the literature in any of the formerly documented cases of scrotal neurofibroma. The current case expands the spectrum of differential diagnoses for scrotal tumours that clinicians have previously observed.

Pelodera strongyloides in the critically endangered Apennine brown bear (Ursus arctos marsicanus).

Skin biopsies from 20 Apennine brown bears (Ursus arctos marsicanus), 17 of which displaying skin lesions, were investigated by histopathology. Different degrees of dermatitis characterized by folliculitis and furunculosis accompanied by epidermal hyperplasia and epidermal and follicular hyperkeratosis were detected. In the most severe lesions, the superimposition of traumatic wounds, probably self-induced by scratching, was observed. In 8 out of 17 (47.0%) affected bears, cross- and longitudinally-sectioned nematode larvae were present within the lumen of hair follicles, whose localization and morphological characteristics were consistent with Pelodera strongyloides. P. strongyloides is a free-living saprophytic nematode whose third-stage larvae can invade the skin causing pruritic dermatitis in several mammalian species. This is the first report of Pelodera infection in the brown bear. Although capable of causing primary dermatitis, the finding of Pelodera is not sufficient to conclude that it is the cause of the lesions observed in bears. Nevertheless, the high prevalence of the infection is indicative of a diffuse phenomenon that requires further specific investigations given the interest and conservational relevance of this relict bear population.

SPINAL NEMATODIASIS IN A LINED FLAT-TAIL GECKO (UROPLATUS LINEATUS).

A 5-y-old female lined flat-tail gecko (Uroplatus lineatus) presented for acute onset of lethargy and paraplegia and was subsequently euthanized. Histologic examination of the spinal cord revealed a verminous myelitis comprising moderate, multifocal, necrotizing myelitis with intramedullary adult and larval nematodes. Molecular data and morphology indicate a cosmocercid nematode, most likely of the genus Raillietnema, a diverse taxon reported to parasitize reptiles, amphibians, and teleost fish. To the authors' knowledge this is the first report of spinal nematodiasis in a reptile species, and the first report of spinal parasitism causing hind-limb paraplegia in a reptile.

Nematode parasitism affects lying time and overall activity patterns in lambs following pasture exposure around weaning.

We investigated the effects of gastrointestinal nematode (GIN) challenge on activity in first season grazing lambs naturally exposed to two different levels of multispecies GIN infections. Ewes and their twin-born lambs were turned-out to graze in two permanent pasture enclosures naturally contaminated with GIN the previous year, thereby exposing them to overwintering strongyle larvae. Animals in the low parasite exposure group (LP) were dewormed monthly with 0.2 mg ivermectin (Ivomec® vet, oral suspension) per kg body weight, whereas those in high parasite exposure group (HP) were left untreated. At weaning, lambs were allocated to one out of four groups based on weight and sex (HPE, n = 15; HPR, n = 15; LPE, n = 14; LPR, n = 14), in four nearby non-contaminated ley enclosures of similar size. Activity patterns were monitored from day -7, i.e. 7 days pre-weaning, until day 49, i.e. 49 days post-weaning, by fitting all lambs with IceQube sensors (IceRobotics). Body weight was monitored weekly from day -21, whereas faecal samples were investigated at days -21, 7, 35 and 49 for nematode faecal egg counts (EPG) using McMaster-technology and a validated Droplet Digital PCR protocol to determine nematode composition. All statistical analyses were performed in R studio, using mixed models with repeated measures. In the data analyses, weekly recordings was treated as a period, generating a total of eight periods. Average daily lying time had a significant interaction between parasite exposure and period (P = 0.0013), with animals in HP having a 101 ± 31 min shorter daily lying time compared to LP. Motion Index (MI; absolute value of the 3-D acceleration) had a significant interaction between parasite exposure and period (P = 0.0001) with lambs in group HP having a lower average daily MI compared with LP. Both body weight gain and EPG levels were significantly different (P<0.0001) between HP and LP groups during the course of the study. The molecular investigation showed that animals were predominantly infected with Teladorsagia spp., combined with low proportions of Haemonchus spp. In conclusion, this study shows that lying time and Motion Index of lambs around weaning was affected by moderate nematode infections. This indicates that there is a potential use of automated behaviour recordings as a diagnostic tool for detection of nematode parasites in lambs even at moderate infection levels.

Anthelmintic Activity of Yeast Particle-Encapsulated Terpenes.

Soil-transmitted nematodes (STN) infect 1-2 billion of the poorest people worldwide. Only benzimidazoles are currently used in mass drug administration, with many instances of reduced activity. Terpenes are a class of compounds with anthelmintic activity. Thymol, a natural monoterpene phenol, was used to help eradicate hookworms in the U.S. South circa 1910. However, the use of terpenes as anthelmintics was discontinued because of adverse side effects associated with high doses and premature stomach absorption. Furthermore, the dose-response activity of specific terpenes against STNs has been understudied. Here we used hollow, porous yeast particles (YPs) to efficiently encapsulate (>95%) high levels of terpenes (52% w/w) and evaluated their anthelmintic activity on hookworms (Ancylostoma ceylanicum), a rodent parasite (Nippostrongylus brasiliensis), and whipworm (Trichuris muris). We identified YP-terpenes that were effective against all three parasites. Further, YP-terpenes overcame albendazole-resistant Caenorhabditis elegans. These results demonstrate that terpenes are broad-acting anthelmintics. Terpenes are predicted to be extremely difficult for parasites to resist, and YP encapsulation provides water-suspendable terpene materials without surfactants and sustained terpene release that could lead to the development of formulations for oral delivery that overcome fast absorption in the stomach, thus reducing dosage and toxic side effects.

Nodular and sclerosing gastritis caused by Cylicospirura felineus in a puma (Puma concolor).

An adult male puma (Puma concolor), hit by a car in an urban area, died three days later despite the therapeutic support provided. At necropsy, multiple firm nodules were identified in the gastric mucosa. The nodules were coated by an intact mucosa with a central opening from which reddish and cylindrical nematodes protruded into the lumen. Twenty-seven nematodes were retrieved for morphological and morphometric evaluations. During histopathological examination of the gastric tissue, the adult nematodes appear in longitudinal and transverse sections, surrounded by thick bands of collagen, interspersed with mixed inflammatory infiltrates. The nematodes had an eosinophilic cuticle with caudal serrated projections (bulbar type), coelomyarian musculature, pseudocoelom, and females with uterus containing numerous larvated eggs, characteristics consistent with the Cylicospirura genus. Morphologically, female nematodes had six large tricuspid teeth in the oral cavity and the vulva had an opening anterior to the esophagus-intestinal junction. Male nematodes had five pairs of small papillae near the tip of the tail. These findings were consistent with Cylicospirura felineus. This parasite should be included in the differential diagnosis of nodular gastric wall lesions in wild felids.

Demographic and reproductive associations with nematode infection in a long-lived mammal.

Infection by macroparasites, such as nematodes, varies within vertebrate host systems; elevated infection is commonly observed in juveniles and males, and, for females, with different reproductive states. However, while such patterns are widely recognized in short-lived model systems, how they apply to long-lived hosts is comparatively understudied. Here, we investigated how infection varies with host age, sex, and female reproduction in a semi-captive population of individually marked Asian elephants Elephas maximus. We carried out 1,977 faecal egg counts (FECs) across five years to estimate nematode loads for 324 hosts. Infection patterns followed an established age-infection curve, whereby calves (5 years) exhibited the highest FECs and adults (45 years) the lowest. However, males and females had similar FECs across their long lifespan, despite distinct differences in life-history strategy and clear sexual dimorphism. Additionally, although mothers invest two years in pregnancy and a further three to five years into lactation, nematode load did not vary with four different measures of female reproduction. Our results provide a much-needed insight into the host-parasite dynamics of a long-lived host; determining host-specific associations with infection in such systems is important for broadening our knowledge of parasite ecology and provides practical applications for wildlife medicine and management.

Insights on Spirocerca lupi, the Carcinogenic Dog Nematode.

Spirocerca lupi is a nematode transmitted by dung beetles that infects domestic and wild canids in tropical and subtropical regions and is associated with neoplasia. It produces a distinctive pathology with the formation of esophageal nodules classified as inflammatory, preneoplastic, or neoplastic with metastasis to distant organs. Aberrant central nervous system migration of this nematode is also responsible for severe neurological manifestations. Reports of spirocercosis have increased over the last two decades showing spread of this canine helminth in five continents. S. lupi from different geographical locations is genetically distinct with two genotypes, genotype I from Africa, Asia, and Australia, and genotype II from Europe, and recently separated from Spirocerca vulpis, a new species described in red foxes from Europe.

Nodular and sclerosing gastritis caused by Cylicospirura felineus in a puma (Puma concolor) / Gastrite nodular esclerosante causada por Cylicospirura felineus em onça parda (Puma concolor)

Abstract An adult male puma (Puma concolor), hit by a car in an urban area, died three days later despite the therapeutic support provided. At necropsy, multiple firm nodules were identified in the gastric mucosa. The nodules were coated by an intact mucosa with a central opening from which reddish and cylindrical nematodes protruded into the lumen. Twenty-seven nematodes were retrieved for morphological and morphometric evaluations. During histopathological examination of the gastric tissue, the adult nematodes appear in longitudinal and transverse sections, surrounded by thick bands of collagen, interspersed with mixed inflammatory infiltrates. The nematodes had an eosinophilic cuticle with caudal serrated projections (bulbar type), coelomyarian musculature, pseudocoelom, and females with uterus containing numerous larvated eggs, characteristics consistent with the Cylicospirura genus. Morphologically, female nematodes had six large tricuspid teeth in the oral cavity and the vulva had an opening anterior to the esophagus-intestinal junction. Male nematodes had five pairs of small papillae near the tip of the tail. These findings were consistent with Cylicospirura felineus. This parasite should be included in the differential diagnosis of nodular gastric wall lesions in wild felids.

Resumo Uma onça parda (Puma concolor) foi encontrada em uma área urbana após atropelamento e, apesar do suporte terapêutico fornecido, o animal morreu três dias depois. No exame post-mortem, múltiplos nódulos firmes foram identificados na mucosa gástrica. Os nódulos eram revestidos por mucosa intacta com um orifício central, do qual se insinuavam nematódeos cilíndricos e avermelhados. Vinte e sete nematódeos foram recuperados para avaliação morfológica e morfométrica. Na avaliação histopatológica do tecido gástrico, os nematódeos adultos apareceram em cortes longitudinais e transversais, circundados por bandas espessas de colágeno, intercaladas por infiltrado inflamatório misto. Os nematódeos eram constituídos por cutícula eosinofílica, com projeções serrilhadas voltadas caudalmente (do tipo bulbar), musculatura celomiariana, pseudoceloma e, nas fêmeas, útero com numerosos ovos larvados cujos achados foram sugestivos do gênero Cylicospirura. Morfologicamente, a cavidade bucal continha seis grandes dentes trífidos, na fêmea, a abertura da vulva era anterior à junção esôfago intestinal; e os machos tinham cinco pares de pequenas papilas próximas à ponta da cauda. Esses achados foram consistentes com Cylicospirura felineus. Este parasita deve ser incluído no diagnóstico diferencial de lesões nodulares da parede gástrica em felinos selvagens.

Morphological and Pathological Findings in the Middle and Inner Ears of Harbour Porpoises (Phocoena phocoena).

Hearing represents the major sense in harbour porpoises (Phocoena phocoena) and impairment of hearing has a great impact on the survival of these animals. In this communication, some anatomical and histological aspects of the tympanoperiotic complex of harbour porpoises are presented. In addition, the ears of 21 incidentally bycaught or stranded freshly dead harbour porpoises of different age groups and sex were investigated histologically. At the entrance to the middle ear cavity, mucosa-associated lymphoid tissue was present that was often hyperplastic in juvenile (9/10) and adult individuals (7/8). Solitary lymphoid follicles were additionally found in the corpus cavernosum and adjacent to the stapedius muscle in single porpoises. The nematode Stenurus minor represented the most common pathogen observed in the middle ear cavity of juvenile and adult harbour porpoises and the parasite was associated with chronic inflammation with metaplastic and hyperplastic epithelial changes. An unusual bone formation at the attachment of the corpus cavernosum to the perioticum was a common finding, even in young individuals. Whether this represents a normal structure or a metaplastic change remains undetermined. Acute haemorrhages in the cochlea and/or the tympanic cavity occurred in all animals and were most likely agonal changes. Single porpoises suffered from purulent otitis media, mycotic otitis media with osteolysis or chronically fractured tympanic bones, likely causing impairment of hearing that may have contributed to by-catch. There was no evidence that stranding in five porpoises was associated with the aural changes. Histological examination of the ears in harbour porpoises is a valuable part of the assessment of their health status. Damage to hearing structures may explain starvation due to impaired ability to catch prey or unusual behaviour such as stranding or entanglement in nets.

Histopathological study of Corydoras micracanthus (Siluriformes: Callichthyidae) parasitized by the nematode Procamallanus (Spirocamallanus) pintoi (Camallanidae) from Lesser River, northwestern Argentina, South America

The nematode parasites can cause mechanical injuries such as irritation or atrophy of tissue and occlusions of the digestive tract, blood vessels or other ducts in their hosts. Some species belonging to the family Camallanidae have been the focus of histopathological studies because they lacerate the host´s intestinal wall with their buccal capsule. In this study, we describe the histopathological effects produced by Procamallanus (Spirocamallanus) pintoi in the small fish Corydoras micracanthus from Lesser River, in the northwest of Argentina, South America. The samples were processed with routine histology techniques. At light microscopy, specimens of P. (S.) pintoi were observed occupying the lumen of the gut. The histopathological sections revealed damage to the host intestine with the total destruction of the mucosa and submucosa, observed mainly in the region which is surrounding the buccal capsule of parasites. Moreover, an inflammatory reaction was observed with lymphatic accumulations in the affected tissue. This kind of degenerative and necrotic changes in the mucosa could affect negatively the absorption function of the host intestine, which may have adverse effects of the health status of fish. The present study provides the firs data about the histopathological effects of P. (S.) pintoi in C. micracanthus.

Diplotriaena-An Air Sac Nematode Found in a New Holland Honeyeater (Phylidonyris novaehollandiae).

A New Holland honeyeater (Phylidonyris novaehollandiae), a common species found mostly in the southern parts of Australia, was examined after a presumed traumatic incident but died several hours after presentation. At necropsy, a Diplotriaena nematode was found in a cranial air sac. Although no obvious gross pathologic changes were attributed to the nematode, histologic changes of bronchial epithelial hyperplasia and goblet cell metaplasia, consistent with chronic airway irritation were found in the lungs associated with Diplotriaena eggs. Diplotriaena species are parasitic nematodes found in the air sacs of birds. These parasites have an indirect life cycle; larval stages develop in insects, and when eaten by the host, these larvae migrate to the air sac and become adults. Although Diplotriaena species have been found in birds worldwide, none, to our knowledge, have previously been described in New Holland honeyeaters.

Subconjunctival nodule due to Setaria equina erratic migration in a horse: First case report.

An 18-month-old Arabian-English filly resident in southwest France was referred for evaluation of a conjunctival mass in the right eye (OD). A pink, solid, and mobile nodular formation, measuring approximately 1.2 × 0.8 cm was found under the superior nasal bulbar conjunctiva during an ophthalmic examination that was otherwise normal. The mass was surgically removed using a standing procedure. Cytological examination of fine-needle aspirates from the mass revealed a mixed eosinophilic-lymphocytic inflammation. Histological examination confirmed the dense and diffuse eosinophilic-lymphocytic infiltrate of the mass, and it revealed several cross sections of a parasitic nematode. The morphometric diagnosis identified an immature form of a filarial worm, and molecular analysis of the mitochondrial cytochrome c oxydase subunit 1 (cox1) and 12S rRNA gene sequences led to further identification of the specimen as Setaria equina. Microfilaremia was not observed on fresh blood smears. There have been no signs of local recurrence after 18 months, nor any evidence of intraocular involvement. To the authors' knowledge, this is the first documented case of subconjunctival setariasis due to S equina in a horse.

Cardiopulmonary parasitic nematodes of the red fox (Vulpes vulpes) in Serbia.

Among the wild canids, the red fox (Vulpes vulpes) is recognised as an important reservoir species for a range of parasites, including cardiopulmonary nematodes of public health and veterinary importance. As cross-host transmission between the red fox and domestic carnivores can play an important role in the epizootiology of cardiopulmonary parasitic diseases, the aim of the present investigations was to obtain data on the geographical distribution of cardiopulmonary nematodes of the red fox. The material for examination consisted of 83 foxes which were legally hunted at different locations during a three-month period from December 2017 to February 2018. The presence of four emerging species in Europe (Angiostrongylus vasorum, Crenosoma vulpis, Dirofilaria immitis and Eucoleus aerophilus) was revealed in red foxes of Serbia. Crenosoma vulpis and E. aerophilus were detected in foxes in both the plain and the mountainous areas across the country. Dirofilaria immitis is distributed in red foxes near alluvial rivers in Vojvodina province (northern Serbia). Angiostrongylosis caused by A. vasorum was demonstrated to exist in two enzootic foci with a high percentage of infected foxes in a plain area of northern Serbia. To the best of our knowledge, C. vulpis and A. vasorum were discovered for the first time in red foxes in central Serbia. The results provide strong evidence for veterinarians to take into consideration the parasitic nematodes discovered in red foxes in the differential diagnosis of diseases of companion animals. In the context of the 'One Health' approach the results related to the distribution of the zoonotic species E. aerophilus and D. immitis can be useful for medical epidemiology.

Calodium hepaticum (Trichuroidea: Capillariidae) Infection In Akodon azarae: First Description of Histopathological Lesions In Sigmodontinae.

Calodium hepaticum (Trichinellida: Capillaridae) is a parasitic nematode of mammals distributed worldwide. Although this parasite can infect the liver of a wide diversity of mammals (including humans), it is mostly associated with Muroidea hosts. Sigmodontinae rodents were recently recognized as important hosts of this parasite in Argentina, but the impact of this parasitism on these hosts has not been established. Here we report results of histopathological analyses of 40 livers of Akodon azarae infected with C. hepaticum. Lesions were classified into 4 categories: level 0, absence of lesions; level 1, with focal granulomatous hepatitis; level 2, presence of multifocal granulomatous hepatitis, fibrosis and focal necrosis with neutrophils, and level 3, absence of intact adult parasites, diffuse distribution, necrosis, and fibrosis. Most samples presented lesions of level 2 (55%), but all categories of lesions were found. This is the first study to describe the lesions caused by C. hepaticum in the liver of Sigmodontinae rodents, and the results suggest that infection by this parasite is costly to A. azarae populations.

Variation in phenotypic resistance to gastrointestinal nematodes in hair sheep in the humid tropics of Mexico.

The objective of the study was to evaluate phenotypic resistance against gastrointestinal nematodes in Blackbelly, Pelibuey and Katahdin ewes before pregnancy in the humid tropics of Mexico. Individual faecal and blood samples were taken in 59 Pelibuey, 69 Blackbelly and 73 Katahdin ewes. The egg count per gram of faeces (EPG) of gastrointestinal nematodes (GINs) was determined. The percentage of packed cell volume (PCV) and body condition score (BCS) of each animal were also recorded. The ewes were segregated as susceptible, intermediate or resistant based on the EPG using the quartile method. The data were analysed using the general linear method, and the means between breeds were compared by Tukey's test. The relationships between the EPG, PCV and BCS were evaluated by Spearman correlation. The Katahdin ewes showed the highest EPG counts (3613.6 ± 5649) compared to the Blackbelly and Pelibuey ewes (576.1 ± 1009 and 56.8 ± 187, respectively, P < 0.01). The PCV values between breeds were similar (P > 0.05). The susceptible ewes had the highest EPG counts and the lowest PCV percentage (5069 ± 6404 and 22.8% ± 8.1% respectively) compared to the resistant ewes (P < 0.01). A higher percentage of Katahdin ewes were susceptible compared to the other breeds (P < 0.05). The main GIN species were Haemonchus contortus, Trichostrongylus colubriformis and Cooperia curticei. In conclusion, Katahdin ewes showed susceptibility to GIN compared to Blackbelly and Pelibuey ewes before the pregnancy period in the humid tropics of Mexico.

Clinical Case of Respiratory Eucoleosis in a Dog from Bosnia and Herzegovina.

AIMS: This case report describes a clinical case of patent and natural infection with trichuroid Eucoleus aerophilus in a 5-month-old, mixed-breed female dog in Bosnia and Herzegovina. METHODS: A detailed history was taken from the owner. Physical exam and thoracic radiography were performed. Faecal sample was processed by the passive flotation tube test with saturated zinc sulphate solution. After the final diagnosis, a dose of 0.4 mg /kg ivermectin was applied subcutaneously to the diseased dog. RESULTS: The history revealed intermittent, non-productive cough after physical exercise. During the physical exam, mild signs of general distress, moderate cachexia with bad body condition, increased heart and respiratory rates, mild dyspnoea and increased bronchovesicular respirations were observed. Thoracic radiography showed mixed bronchial-alveolar lung pattern compatible with chronic bronchopneumonia. Trichuroid eggs of Eucoleus aerophilus were detected in faecal samples from the affected dog. Ivermectin administration at a dose of 0.4 mg/kg was sufficient to eliminate parasitic infection with Eucoleus aerophilus. CONCLUSION: This is the first report of respiratory eucoleosis in a dog from Bosnia and Herzegovina.

Impact of gastrointestinal parasitism on dry matter intake and live weight gain of lambs: A meta-analysis to estimate the metabolic cost of gastrointestinal nematodes.

This study aimed to estimate the effect of gastrointestinal nematodes (GIN) on the productive performance assessed by the live-weight change (LWC) of lambs, and the metabolic cost associated with parasitism by means of a meta-analysis. Data used in the meta-analyses were obtained from twenty papers selected using the following criteria: (a) lambs with (I) and without (NI) GIN; (b) lambs fed ad libitum; (c) LWC data; (d) feed consumption data; and (e) chemical composition of diets. The effect of diet composition (crude protein [CP] and metabolizable energy [ME]) on dry matter intake (DMI), and the effect of composition and nutrient intake (DMI and CP intake [CPI]) and ME intake (MEI) on LWC was evaluated using respective regression analyses. The metabolic cost of worm burden was determined as the difference in CP and ME requirements between NI and I lambs for each adult parasite. The CP and ME cost were evaluated for lambs at two different levels: maintenance level 0 g LWC and 100 g LWC. The worm burden had an impact on the DMI and LWC of lambs (P < 0.05). The association of CP x infection level was the best predictor of DMI. The association between MEI and infection level were the best predictors of LWC. The metabolic cost of GIN increased to 0.30 mg CP/kg LW0.75 and 0.0056 kJ ME/kg LW0.75 for each adult parasite. The metabolic cost was not modified by diet quality (maintenance level 0 g LW/day or 100 g LW/day). In conclusion, GIN has a negative effect on DMI and LWC. The metabolic cost of GIN infection can be covered by supplying the additional requirements for protein and energy in the diet of infected lambs.

The effects of living in an outdoor enclosure on hippocampal plasticity and anxiety-like behavior in response to nematode infection.

The hippocampus of rodents undergoes structural remodeling throughout adulthood, including the addition of new neurons. Adult neurogenesis is sensitive to environmental enrichment and stress. Microglia, the brain's resident immune cells, are involved in adult neurogenesis by engulfing dying new neurons. While previous studies using laboratory environmental enrichment have investigated alterations in brain structure and function, they do not provide an adequate reflection of living in the wild, in which stress and environmental instability are common. Here, we compared mice living in standard laboratory settings to mice living in outdoor enclosures to assess the complex interactions among environment, gut infection, and hippocampal plasticity. We infected mice with parasitic worms and studied their effects on adult neurogenesis, microglia, and functions associated with the hippocampus, including cognition and anxiety regulation. We found an increase in immature neuron numbers of mice living in outdoor enclosures regardless of infection. While outdoor living prevented increases in microglial reactivity induced by infection in both the dorsal and ventral hippocampus, outdoor mice with infection had fewer microglia and microglial processes in the ventral hippocampus. We observed no differences in cognitive performance on the hippocampus-dependent object location task between infected and uninfected mice living in either setting. However, we found that infection caused an increase in anxiety-like behavior in the open field test but only in outdoor mice. These findings suggest that living conditions, as well as gut infection, interact to produce complex effects on brain structure and function.

The Influence of Sex, Parasitism, and Ontogeny on the Physiological Response of European Eels (Anguilla anguilla) to an Abiotic Stressor.

Migration of adult European eels (Anguilla anguilla) from freshwater feeding grounds to oceanic spawning grounds is an energetically demanding process and is accompanied by dramatic physiological and behavioral changes. Humans have altered the aquatic environment (e.g., dams) and made an inherently challenging migration even more difficult; human activity is regarded as the primary driver of the collapse in eel populations. The neuroendocrine stress response is central in coping with these challenging conditions, yet little is known about how various biotic factors such as sex, parasites, and ontogeny influence (singly and via interactions) the stress response of eels. In this study, mixed-effects and linear models were used to quantify the influence of sex, parasitism (Anguillicola crassus), life stage (yellow and silver eels), and silvering stage on the stress response of eels when exposed to a standardized handling stressor. The physiological response of eels to a standardized abiotic stressor (netting confinement in air) was quantified through measurements of blood glucose and plasma cortisol. The relationships between biotic factors and the activity of gill Na+/K+-ATPase was also examined. Analyses revealed that in some instances a biotic factor acted alone while in other cases several factors interacted to influence the stress response. Blood glucose concentrations increased after exposure to the standardized stressor and remained elevated after 4 h. Variation in plasma cortisol concentrations after exposure to the stressor were found to be time dependent, which was exacerbated by life stage and parasitism condition. Males and nonparasitized silver eels had the highest Na+/K+-ATPase activity. Silvering stage was strongly positively correlated with Na+/K+-ATPase activity in female eels. Collectively, these findings confirm that the factors mediating stress responsiveness in fish are complicated and that aspects of inherent biotic variation cannot be ignored.