Parasite Intensity Research Articles

Parasite Diversity in a Freshwater Ecosystem.

Parasites are a significant component of biodiversity. They negatively affect fish appearance, growth, and reproduction. In this study, the prevalence of infection, diversity, and mean intensity of parasites were examined in 9 freshwater fish species (45 samples per fish species). Ecto-parasites were examined on the skin, gills, and fins with a hand lens. Wet mounts were prepared using mucosal scrapings from all the external and internal organs of the sampled fish. Microscopy, muscle compression, and the pepsin-HCL artificial digestion technique were also performed. In this study, 26 species of parasites were identified including three taxa belonging to 9 species of protozoan parasites, 11 treamtodes, and 6 monogenean parasites. The identified protozoan parasites were Entamoeba histolitica, Chilodonella sp., Coccidia sp., Costia sp., Cryptobia sp., Ichthyopthiris-multifilis, Microsporidia, Piscinoodinium sp., and Ichthyobodo necator. The identified trematode parasites were Fasciola gigantica, Echinostoma revolutum, Fasciola hepatica, Haplorchis pumilio, Brachylaima cribbi, Echinostoma cinetorchis, Neascus sp., Deropegus sp., Trematode Soldier, Centrocestus formosanus, and Clinostomum marginatum. The identified monogenean parasites were Dactylogyrus limipopoensis, Dactylogyrus anchoratus, Dactylogyrus myersi, Dactylogyrus vastator, Gyrodactylus salaris, and Ancyrocephalus. The diversity of parasites was maximum at the Okara site. The host's organs that were targeted for parasitic infection included the intestine, liver, gills, fins, skin, and kidneys. The majority of the parasites were identified in Labeo rohita followed by Hypophthalmichthys molitrix, Ctenopharyngodon idella, Oreochromis niloticus, Cyprinus carpio, and Wallagu attu. Two species appeared to be resistant species because none of the parasites were observed in Notopterus notopterus or Sperata seenghala. This study also concluded that the prevalence of parasites increased with increasing length, size, and age of fish.

Impacts of brood parasitism by shiny cowbird Molothrus bonariensis on the breeding success of a small host, the black-backed water tyrant Fluvicola albiventer.

The shiny cowbird Molothrus bonariensis parasitizes many species with different life-history traits and has a detrimental effect on the survival of the progeny of the hosts. In response, hosts have developed numerous antiparasitic defenses. Here, we examined the effects of brood parasitism by shiny cowbird on the clutch and brood sizes (83 nests) in a small host, the black-backed water tyrant Fluvicola albiventer. We also studied whether the death of parasite nestlings was related to the care of the foster parents and whether the host had any antiparasitic defense against the shiny cowbird. Our results indicate that brood parasitism significantly decreased the host hatching and fledging successes. The majority of nest failures (57%) were caused by brood parasitism. Shiny cowbird parasitism occurred in 52% of nests and the intensity of parasitism was 1.23 ± 0.53 eggs per parasitized nest. Of the total host eggs, 54% were damaged. During the incubation stage, 20 nests (47%) were abandoned because of egg punctures by shiny cowbirds females. Only two parasitic fledglings were recorded, while the remaining nestlings either died from starvation (n = 12) or predation (n = 3). Foster parents abandoned parasitic nestlings between 5 and 10 days old. Our findings demonstrate that the shiny cowbird has very low rates of fledging success when parasitizing black-backed water tyrant. Also, parasitism had a high reproductive cost in the black-backed water tyrant because a very low proportion (7%) of the parasitized nests (n = 43) were successful.

Multiparasitism and repeated parasitism by the great spotted cuckoo Clamator glandarius on its main host, the magpie Pica pica: effects on reproductive success, nest desertion and nest predation

Brood parasites are expected to lay only one egg per parasitized nest, as the existence of several parasitic nestlings in a brood increases competition and can lead the starvation of some of them. However, multiparasitism (laying of two or more eggs by one or more parasitic females in a single host nest) is surprisingly frequent. Here, we study multiparasitism by different females or by the same female (repeated parasitism) in the great spotted cuckoo Clamator glandarius, a non‐evictor brood parasite that mainly parasitizes the magpie Pica pica, and whose chicks may be raised together with host nestlings in the same nest. We used a total of 262 magpie nests found during four breeding seasons. Multiparasitism and repeated parasitism are very frequent because this brood parasite is less virulent than other cuckoo species and magpie hosts can successfully raise more than one parasitic nestling per nest. The total number of cuckoo chicks fledged was higher in multiparasitized nests than in single‐ or double‐parasitized magpie nests. Magpie breeding success (i.e. the proportion of eggs that produce young that leave the nest) did not differ between single‐, double‐, and multiparasitized magpie nests. These results suggest that multiparasitism is an adaptation in the great spotted cuckoo. The intensity of parasitism (number of cuckoo eggs per nest), after controlling for the potential effect of year, did not affect nest desertion or nest predation rate, neither during the incubation nor the nestling periods. This implies that nest concealment does not affect the susceptibility of one nest being parasitized and predated, as nest predation rate was similar regardless of the intensity of parasitism. Predation rate during the nestling phase did not vary according to intensity of parasitism, which does not support either the ‘mutualism' hypothesis or the ‘predation cost of begging' hypothesis.

Dual effector population modification gene-drive strains of the African malaria mosquitoes, Anopheles gambiae and Anopheles coluzzii

Proposed genetic approaches for reducing human malaria include population modification, which introduces genes into vector mosquitoes to reduce or prevent parasite transmission. We demonstrate the potential of Cas9/guide RNA (gRNA)-based gene-drive systems linked to dual antiparasite effector genes to spread rapidly through mosquito populations. Two strains have an autonomous gene-drive system coupled to dual anti-Plasmodium falciparum effector genes comprising single-chain variable fragment monoclonal antibodies targeting parasite ookinetes and sporozoites in the African malaria mosquitoes Anopheles gambiae (AgTP13) and Anopheles coluzzii (AcTP13). The gene-drive systems achieved full introduction within 3 to 6 mo after release in small cage trials. Life-table analyses revealed no fitness loads affecting AcTP13 gene-drive dynamics but AgTP13 males were less competitive than wild types. The effector molecules reduced significantly both parasite prevalence and infection intensities. These data supported transmission modeling of conceptual field releases in an island setting that shows meaningful epidemiological impacts at different sporozoite threshold levels (2.5 to 10 k) for human infection by reducing malaria incidence in optimal simulations by 50 to 90% within as few as 1 to 2 mo after a series of releases, and by ≥90% within 3 mo. Modeling outcomes for low sporozoite thresholds are sensitive to gene-drive system fitness loads, gametocytemia infection intensities during parasite challenges, and the formation of potentially drive-resistant genome target sites, extending the predicted times to achieve reduced incidence. TP13-based strains could be effective for malaria control strategies following validation of sporozoite transmission threshold numbers and testing field-derived parasite strains. These or similar strains are viable candidates for future field trials in a malaria-endemic region.

External and gastrointestinal parasites of the black-faced ibis Theristicus melanopis (Pelecaniformes: Threskiornithidae) in the Los Ríos region, southern Chile.

The black-faced ibis, Theristicus melanopis, is considered a useful bird species for agricultural activity because it preys upon various invertebrate and vertebrate pests. Although it is a common species in Chile, limited information is available regarding its parasites. The main objective of this study was to recover the diversity of ectoparasites and gastrointestinal helminths in black-faced ibises living in the communes of Valdivia and Panguipulli, Los Ríos region. A total of 74 specimens were received for examination from the Centro de Rehabilitación de Fauna Silvestre at the Universidad Austral de Chile (CEREFAS-UACh), Valdivia, in 2011-2015. Black-faced ibises were externally inspected for ectoparasites by direct examining of the plumage, and necropsies were performed to examine digestive and respiratory organs in search of endoparasites. For each taxon, prevalence, mean intensity, mean abundance, and range of parasites per bird were estimated. Five species of ectoparasites and six species of helminths were identified. A total of 298 lice (Insecta: Phthiraptera) belonging to four species were collected: Ardeicola melanopis (13.51%), Colpocephalum trispinum (20.27%), Ibidoecus fissisignatus (4.05%), and Plegadiphilus mamillatus (9.46%). In addition, one feather mite species, Diodochaetus melanopis (Acari: Pterolichoidea) (17.56%), was isolated. In 48 black-faced ibis (64.86%), a total of 1229 gastrointestinal helminths were found: two nematodes, Porrocaecum heteropterum (55.41%) and Baruscapillaria obsignata (24.32%); one tapeworm Eugonodaeum nasuta (20.27%); two digeneans, Echinoparyphium recurvatum (1.35%) and Strigea bulbosa (6.76%); and the acanthocephalan Sphaerirostris sp. (1.35%). The findings of the following parasites present new host-parasite associations: P. mamillatus, D. melanopis, B. obsignata, E. recurvatum, S. bulbosa, and Sphaerirostris sp. Additionally, the louse P. mamillatus, feather mite D. melanopis, platyhelminths E. nasuta, E. recurvatum and S. bulbosa, and the acanthocephalan Sphaerirostris sp. are new records for the fauna of Chile.

Occurrence of the Parasite Myosaccium ecaude in Thread Herrings from the Gulf of Tehuantepec, Mexico

Thread herrings (Opisthonema spp.) are economically important fish species in the Tropical Eastern Pacific. Knowledge of the parasitofauna of commercially exploited species is useful as it can increase our understanding of fish biology and ecology. However, our knowledge of the parasites of Opisthonema spp. is limited. During a fisheries exploration survey in April 2022, samples of Opisthonema bulleri and O. libertate were collected from three oceanographic stations in the Gulf of Tehuantepec in the Mexican Pacific. Parasitological analysis of these materials uncovered four parasite species: Myosaccium ecaude (Trematoda), Cribromazocraes sp. (Monogenea), Pseudoterranova sp. (Nematoda), and an unidentified crustacean of the family Pennellidae (Copepoda). All these species appeared rarely, except for M. ecaude, which reached a prevalence of 100%. The median intensity of M. ecaude infection was significantly higher in O. bulleri than in O. libertate. We analyzed the relationship between parasitic infection intensity and three host traits (fork length, body weight, and age). Only body weight showed a significant positive association with intensity. Future studies are required to analyze the possible effects of seasonality, locality, and host ontogeny on the occurrence of M. ecaude in thread herrings in the Tropical Eastern Pacific.

Parasite Diversity and Histopathological Changes Due to Infection on Three Croakers (Pennahia Anea, Panna Microdon and Johnius Argentatus) of Saint Martin’s Island, Bay of Bengal

This study investigated the parasites of three species of croakers (Pennahia anea, Panna microdon, and Johnius argentatus) and their effect on host’s tissues. Fish samples were collected directly from the local fishermen and the fish landing station of Saint Martin’s Island, Bay of Bengal on a regular monthly basis. A total of 448 individuals of parasites were collected of which nine species of parasites were identified including three crustaceans, four nematodes, one pentastomida, and one acanthocephala. The nematode Procamallanus longus had the highest prevalence (50%) and intensity (10.33) compared with the other parasites. The prevalence and intensity of parasites were slightly higher in female fish (55%, 35) than in male fish (50%, 20). The stomach and liver were the most favorable infection sites (53.33%). Furthermore, parasites with the largest length and weight showed the highest prevalence and intensity (66.66% and 38.4 as well as 80% and 72.5, respectively). In histopathological investigations, the most important alterations in various tissues of fish were hemorrhage, necrosis, fatty droplets, edema, vacuolar degenerations, missing villi, haemosiderotic nodules, ovarian follicle disruption, and parasitic cell distribution.
 Bioresearch Commu. 9(2): 1297-1304, 2023 (July)

Multiple hosts, multiple impacts: the role of vertebrate host diversity in shaping mosquito life history and pathogen transmission

The transmission of malaria parasites from mosquito to human is largely determined by the dietary specialization of Anopheles mosquitoes to feed on humans. Few studies have explored the impact of blood meal sources on the fitness of both the parasite and the mosquito. Our study investigated the effects of 3-4 consecutive blood meals from one of four vertebrate species (human, cattle, sheep, or chicken) on several fitness traits, including mosquito feeding rate, blood meal size, susceptibility to wild isolates of Plasmodium falciparum, survival, fecundity, F1 offspring development time, and size. Our findings revealed no significant effect on parasite development. Similarly, parasite exposure had no overall effects on mosquito fitness. However, blood meal type did have a strong impact on mosquito feeding rate, survival, lifetime fecundity, and offspring size. Specifically, mosquitoes that were fed successive chicken blood meals produced fewer eggs and fewer and smaller F1 adults compared to those fed human blood. Combining our results in a theoretical model, we show a decrease in the vectorial capacity of mosquitoes fed chicken or cow blood and an increase in the capacity of those fed sheep blood compared to those fed human blood. These findings emphasize the importance of considering the diversity of blood meal sources in understanding mosquito ecology and their role in the transmission intensity of malaria parasites.

No impacts of glyphosate or Crithidia bombi, or their combination, on the bumblebee microbiome

Pesticides are recognised as a key threat to pollinators, impacting their health in many ways. One route through which pesticides can affect pollinators like bumblebees is through the gut microbiome, with knock-on effects on their immune system and parasite resistance. We tested the impacts of a high acute oral dose of glyphosate on the gut microbiome of the buff tailed bumblebee (Bombus terrestris), and glyphosate’s interaction with the gut parasite (Crithidia bombi). We used a fully crossed design measuring bee mortality, parasite intensity and the bacterial composition in the gut microbiome estimated from the relative abundance of 16S rRNA amplicons. We found no impact of either glyphosate, C. bombi, or their combination on any metric, including bacterial composition. This result differs from studies on honeybees, which have consistently found an impact of glyphosate on gut bacterial composition. This is potentially explained by the use of an acute exposure, rather than a chronic exposure, and the difference in test species. Since A. mellifera is used as a model species to represent pollinators more broadly in risk assessment, our results highlight that caution is needed in extrapolating gut microbiome results from A. mellifera to other bee species.

Anthelmintic effects of peppermint (Mentha piperita), lemon (Citrus limon), and tea tree (Melaleuca alternifolia) essential oils against Monogenean parasite (Dactylogyrus sp.) on carp (Cyprinus carpio).

Dactylogyrus sp. (Monogenea) is one of the most dangerous pathogens causing parasitic infections in carp (Cyprinus carpio) and other freshwater fish. Due to the adverse effects of conventional chemical treatments on the environment and fish, the use of herbal products in aquaculture against various diseases has increased. In the present study, anthelmintic effects of peppermint (Mentha piperita), lemon (Citrus limon), and tea tree (Melaleuca alternifolia) essential oils against Dactylogyrus sp. found on the gills of carp were studied using in vitro and in vivo experiments. In in vitro experiments, 1, 2.5, 5, and 10 μl/ml concentrations of these essential oils were tested on the parasites and cumulative mortalities were observed to reach 100 % after treatment with peppermint, lemon, and tea tree essential oils of 1 μl/ml concentration in approximately 15, 10 and 2 min, respectively. The in vitro experiments demonstrated that the cumulative mortality of the parasites increased with essential oil concentration and exposure duration. As the concentration of essential oil used increased, the observed mean time to death of parasites decreased. In in vivo experiments, median effective concentrations (EC50) as assessed by in vitro tests for peppermint and lemon essential oils in 5 min exposure and EC50 concentration for tea tree essential oil in 2 min exposure was applied on fish as a single bath and there was a significant decrease in the mean parasite intensities (p<0.05). Antiparasitic efficacies of peppermint, lemon, and tea tree essential oils were determined as 28.23 %, 30.95 %, and 35.31 %, respectively. The tea tree oil was the most effective and peppermint oil was the least effective in both in vitro and in vivo experiments. All three herbal essential oils tested in this study have weak antiparasitic potential against monogenean infections in fish.

Resource availability and parasitism intensity influence the response of soybean to the parasitic plant Cuscuta australis.

Parasitic plants can damage crop plants and consequently cause yield losses and thus threaten food security. Resource availability (e.g., phosphorus, water) has an important role in the response of crop plants to biotic attacks. However, how the growth of crop plants under parasitism are affected by environmental resource fluctuation is poorly understood. We conducted a pot experiment to test the effects of the intensity of Cuscuta australis parasitism and the availability of water and phosphorus (P) on soybean shoot and root biomass. We found that low-intensity parasitism caused ~6% biomass reduction, while high-intensity parasitism caused ~26% biomass reduction in soybean. Under 5-15% water holding capacity (WHC), the deleterious effect of parasitism on soybean hosts was ~60% and ~115% higher than that under 45-55% WHC and 85-95% WHC, respectively. When the P supply was 0 μM, the deleterious effect of parasitism on soybean was 67% lower than that when the P supply was 20 μM. Besides, the biomass of C. australis was highest when both the water and the P availability were lowest. Cuscuta australis caused the highest damage to soybean hosts under 5 μM P supply, 5-15% WHC, and high-intensity parasitism. Additionally, C. australis biomass was significantly and negatively related to the deleterious effect of parasitism on soybean hosts and to the total biomass of soybean hosts under high-intensity parasitism, but not under low-intensity parasitism. Although high resource availability can promote soybean growth, the two resources have different impacts on the response of hosts to parasitism. Higher P availability decreased host tolerance to parasites, while higher water availability increased host tolerance. These results indicate that crop management, specifically water and phosphorus supply, can efficiently control C. australis in soybean. To our best knowledge, this appears to be the first study to test the interactive effect of different resources on the growth and response of host plants under parasitism.

Modeling the contribution of antibody attack rates to single and dual helminth infections in a natural system

Within-host models of infection can provide important insights into the processes that affect parasite spread and persistence in host populations. However, modeling can be limited by the availability of empirical data, a problem commonly encountered in natural systems. Here, we used six years of immune-infection observations of two gastrointestinal helminths (Trichostrongylus retortaeformis and Graphidium strigosum) from a population of European rabbits (Oryctolagus cuniculus) to develop an age-dependent, mathematical model that explicitly included species-specific and cross-reacting antibody (IgA and IgG) responses to each helminth in hosts with single or dual infections. Different models of single infection were formally compared to test alternative mechanisms of parasite regulation. The two models that best described single infections of each helminth species were then coupled through antibody cross-immunity to examine how the presence of one species could alter the host immune response to, and the within-host dynamics of, the other species. For both single infections, model selection suggested that either IgA or IgG responses could equally explain the observed parasite intensities by host age. However, the antibody attack rate and affinity level changed between the two helminths, it was stronger against T. retortaeformis than against G. strigosum and caused contrasting age-intensity profiles. When the two helminths coinfect the same host, we found variation of the species-specific antibody response to both species together with an asymmetric cross-immune response driven by IgG. Lower attack rate and affinity of antibodies in dual than single infections contributed to the significant increase of both helminth intensities. By combining mathematical modeling with immuno-infection data, our work provides a tractable model framework for disentangling some of the complexities generated by host-parasite and parasite–parasite interactions in natural systems.

Factors Influencing Prevalence and Intensity of Haemosporidian Infection in American Kestrels in the Nonbreeding Season on the Baja California Peninsula, Mexico

ABSTRACT Overwintering areas can act as reservoirs for haemosporidians, and their blood-sucking vectors may easily survive and flourish in warm climates. The American Kestrel (Falco sparverius) is a small-sized raptor that includes both resident and migratory individuals that overwinter in agriculture areas of the Baja California peninsula, Mexico. We measured and collected blood samples from 54 individual kestrels captured in a fragmented habitat located within a matrix of agricultural and native scrub in the southern part of the peninsula during the autumn and winter of 2018–2019 and 2019–2020. We identified and quantified haemosporidians in blood smears of each individual. We used decision tree classification models of prevalence and intensities of haemosporidians to assess the importance of season, host body size, and environmental characteristics of the capture site (proximity to the nearest infected host, number of ponds used for irrigation, Normalized Difference Vegetation Index [NDVI], distance to the edge of the agricultural matrix, and distance to the nearest city). Overall prevalence was 42.6%, with an average intensity of 2.4 haemosporidian-infected cells per 2000 erythrocytes. Most haemosporidians (91.3%) were identified as Haemoproteus tinnunculi, and the rest as Plasmodium spp. The prevalence of haemosporidians increased with pond availability, the distance from the edge of the agricultural matrix, and the proximity of infected individuals. Parasite intensity increased with the availability of ponds, the distance to the edge of the agriculture matrix, and the NDVI. Spatial and temporal patterns of parasite prevalence and intensity illustrated local infection dynamics, suggesting a complex scenario of haemosporidian transmission in migratory and resident kestrels.

Parasitic infection in the scyphozoan Rhizostoma pulmo (Macri, 1778)

Very little information is reported for parasites of cnidarians, therefore, the present work aimed to investigate parasitic infections in one of the most widespread jellyfish in the Mediterranean Sea, Rhizostoma pulmo. The goals were to determine prevalence and intensity of parasites in R. pulmo, identify the species involved through morphological and molecular analysis, test whether infection parameters differ in different body parts and in relation to jellyfish size. 58 individuals were collected, 100% of them infected with digenean metacercariae. Intensity varied between 18.7 ± 6.7 per individual in 0–2 cm diameter jellyfish up to 505 ± 50.6 in 14 cm ones. Morphological and molecular analyses suggest that the metacercariae belonged to the family Lepocreadiidae and could be possibly assigned to the genus Clavogalea. Prevalence values of 100% suggest that R. pulmo is an important intermediate host in the life cycle of lepocreadiids in the region. Our findings also support the hypothesis that R. pulmo is an important part in the diet of teleost fish, which are reported as definitive hosts of lepocreadiids, since trophic transmission is necessary for these parasites to complete their life cycles. Parasitological data may therefore be useful to investigate fish-jellyfish predation, integrating traditional methods such as gut contents analysis.

Overwinter users of nest cavities affect breeding birds via nest‐dwelling ectoparasites

AbstractCavities used for avian reproduction in spring often host other organisms for roosting during winter, which should affect their microclimatic conditions and, then, the patterns of emergence of nest‐dwelling ectoparasites of birds and successful parasitism. To prove these cascade effects, we experimentally blocked the entrance of half of nest boxes previously used for reproduction by hoopoes (Upupa epops), recorded temperature and humidity during the fall–winter period, and evaluated abundance, emergence of ectoparasitic flies (Carnus hemapterus), and intensity of parasitism in hoopoe nestlings growing in open and blocked nest boxes the next spring. As expected, experimental treatment as well as the occupancy of open nest boxes by rodents (i.e., mainly dormice [Eliomys quercinus]) affected temperature and humidity, but did not predict the onset or duration of Carnus emergence. Moreover, flies were more abundant in open nest boxes and, among them, those occupied by dormice showed the lowest abundance. Finally, hoopoe nestlings developing in nest boxes blocked during winter experienced lower intensity of ectoparasitism than those in open nest boxes. These hitherto undescribed cryptic effects of overwinter occupants of nest cavities on subsequent emergence and viability of nest‐dwelling ectoparasites would profoundly impact on the interaction with their avian hosts.

Ascaridoid parasites in European sardine throughout the annual cycle: Variability in parasitic load according to host stock features.

In recent years, a drop in the condition of the European sardine has been observed. Although several causes have been attributed to this issue, as overfishing and climate change, little is known about the link between ascaridoid nematode parasitisation and fish status. In this study, sardines were obtained from four fishing grounds along the Mediterranean (Alboran, Northern Spain, Northern Adriatic, and Aegean), and one location in the Atlantic Ocean (Southern Portugal). After analysing individual fish body condition (by direct tissue fat content measurements and condition indices), and reproductive status (by a detailed gonadal examination) throughout the entire annual cycle, ascaridoids were recognised by combining naked eye and UV-press method along flesh, viscera, and gonads. Afterwards, sequence analysis of the rDNA internal transcribed spacers region (ITS) and the mtDNA cox2 gene were used to identify and characterise the different species of ascaridoids from the fish host in the localities throughout the seasons. The main species found along different areas was Hysterothylacium aduncum, present in the Northern Adriatic (prevalence of 7.6%, mean intensity 1.700), the Atlantic (7.5%, 3.889), and the Northern Spain (3.9%, 1.600). Moreover, few individuals of Anisakis simplex (s.s.) and A. pegreffii were observed in the Atlantic (1.7% and 0.8%, respectively), and the latter species was also found in the Adriatic stock (0.8%). All ascaridoid specimens were found in viscera. Obtained results seem to indicate that in stocks with medium sizes, small variations in length are related to parasite intensity. This study highlights the importance of seasonal parasitological analyses at stock level and, especially, in capital breeders, as relationships between condition and reproduction parameters and parasitism are conditioned by seasonality.

Parasitism of Dirofilaria incrassata Molin, 1858 in coatis (Nasua nasua).

Populations of the coati, Nasua nasua, like the populations of other wild animals, are regulated by several biotic or abiotic factors. For example, parasites act as a biotic factor affecting the dynamics and density of coati populations. The parasitic nematodes of coatis include Dirofilaria species, such as Dirofilaria immitis, Dirofilaria repens, and Dirofilaria incrassata. Considering that there are few records on parasitism by D. incrassata, including information on the life cycle or location in the host body, this study aimed to investigate the infection of N. nasua by D. incrassata in midwestern Brazil. Thus, two coatis (males and adults) from the Cerrado of Goiás, which died (cause unknown) at the Wild Animal Screening Center/IBAMA in the municipality of Goiânia, Goiás, Midwestern of Brazil, were dissected and all helminths found were collected, identified following specific keys and quantified. A total of 85 specimens of D. incrassata were collected, with a mean parasitic intensity of 42.5 and a parasitic amplitude ranging from 40 to 45, measuring 41-93mm in length and 0.23-0.45mm in width. All helminths were adults and were distributed in the superficial and deep fascia (at different levels) from the neck to the hind limb. Most helminths were tangled, with some encased in a connective tissue film. Most reported human heartworm cases refer to subcutaneous or ocular heartworm infection, mainly caused by D. repens, although other species of heartworm may be associated. D. incrassata was not reported as zoonotic agent, diferently of other Dirofilaria species associated with wild animals and with zoonotic potential in the Americas. This study reiterates N. nasua as the definitive host for D. incrassata and the subcutaneous tissue as the site of choice for this helminth in the adult form. In addition, it reports new body regions where the parasite occurs. This study is the first to document the occurrence of D. incrassata infestation in the State of Goiás, Brazil.

Host genetic identity determines parasite community structure across time and space in oyster restoration.

Intraspecific variation in host susceptibility to individual parasite species is common, yet how these effects scale to mediate the structure of diverse parasite communities in nature is less well understood. To address this knowledge gap, we tested how host genetic identity affects parasite communities on restored reefs seeded with juvenile oysters from different sources-a regional commercial hatchery or one of two wild progenitor lines. We assessed prevalence and intensity of three micro- and two macroparasite species for 4 years following restoration. Despite the spatial proximity of restored reefs, oyster source identity strongly predicted parasite community prevalence across all years, with sources varying in their relative susceptibility to different parasites. Oyster seed source also predicted reef-level parasite intensities across space and through time. Our results highlight that host intraspecific variation can shape parasite community structure in natural systems, and reinforce the importance of considering source identity and diversity in restoration design.

Of mice, ticks, and fleas: host behaviour and co-occurring parasites

Host behaviour should be a key determinant of the acquisition of “sit-and-wait” and nidicolous ectoparasitic arthropods that ambush the host in their environment and/or nest. Here, we tested the association between parasitism and individual differences in exploratory and grooming behaviours in white-footed mice ( Peromyscus leucopus (Rafinesque, 1818)), the primary host for the black-legged tick ( Ixodes scapularis Say, 1821) in its larval stage. During 4333 captures of 1035 individual mice over five summers (2016–2020) in Ontario, Canada, the probability and intensity of tick parasitism were both significantly higher when the mouse was also parasitized by fleas, suggesting co-occurrence of these two parasites on host mice. Distance moved by mice in a novel environment was negatively and positively affected by tick and flea parasitism, respectively. Interestingly, there was a significant “tick × flea” statistical interaction on distance moved, such that fleas were positively associated with activity/exploration only when ticks were absent. There was no relationship between grooming behaviour and parasite presence. This study suggests that co-occurring parasite species (ticks and fleas) may differentially affect their host's behaviour depending on the presence/absence of the other parasite on the host. Alternatively, host behaviour may differentially affect individual susceptibility to being infested with ticks, fleas, or both.

What is the sensitivity and exactness of post-mortem diagnostic method for cardiopulmonary nematodes in wild carnivores? towards the gold standard

Cardiopulmonary nematodes cause health and fitness disorders in wild and domestic carnivores. The red fox (Vulpes vulpes) participates in the spread of these shared parasites at the domestic-wildlife interface. This study aimed to evaluate the sensitivity of post-mortem diagnostic method for detecting lungworms in carnivores, and its exactness to estimate the parasite intensity of each nematode species. Cardiorespiratory system of fifty-one foxes were examined through three consecutively methodological steps: first, the tracheobronchial tree, pulmonary arteries and their branches were opened (OT); next, lung parenchyma was immersed in water and squeezed (WS); finally, the parenchyma was artificially digested in a pepsin and chlorhydric acid solution (AD). Eucoleus aerophilus, Angiostrongylus vasorum, Crenosoma vulpis and Metathelazia capsulata were identified. The number of recovered nematodes in each step were 454 (OT), 285 (WS) and 141 (AD). The use of OT and WS helped to improve parasite intensity results and decreased false negative cases. Accordingly, when OT and WS were used together, the sensitivity in the detection of parasitized foxes was 96.1%, while the exactness of parasite intensity was 84%. When AD was performed, although sensitivity does not rise, results were more exact, increasing the total number of detected parasites by 16%. Moreover, AD improved the sensitivity in the detection of A. vasorum and M. capsulata, as well as quantifying more exactly the parasite intensity (92.5% and 92.3% of exactness without AD, respectively). Our study provides valuable information that should be taken into account when planning epidemiological studies based on cardiopulmonary nematode detection in carnivores.