Larval Migration Research Articles

Linalyl acetate against larvae of Haemonchus spp. and Trichostrongylus spp. that affects ruminants: considerations about the hormetic effect.

Active components from plants are an alternative therapy to parasite control, addressing the widespread multidrug resistance populations. Linalyl acetate (LA), an ester abundantly found in plants of the genus Lavandula, was tested in vitro against third-stage larvae (L3) of Haemonchus spp. and Trichostrongylus spp. using the larval migration test at 0.89, 2.24, 4.47, 8.95, 17.9, 35.8, 71.6, and 143.2 mg/ml. After an initial incubation of 18 h, the total content of each tube was transferred to a 24-well plate that allowed active L3 to migrate through a nylon mesh (second incubation). Although LA exhibited 100% efficacy in reducing larval migration at 8.95 and 17.9 mg/ml, it showed reduced activity (5%) at 143.2 mg/ml. The data revealed a hormetic biphasic response characterised by an inverted U-shaped concentration-response curve. While hormesis has been previously documented in insecticidal and allelopathic contexts, this study reports the occurrence of hormesis induced by a phytochemical component against two species of nematodes for the first time. This distinctive stimulation-and-inhibition effect should be considered when selecting new compounds for preclinical testing.

Sialoadenosis caused by spirocercosis in two dogs from Sri Lanka

AbstractSpirocercosis is a common parasitic disease in dogs in tropical and mediterranean regions of the world caused by the nematode Spirocerca lupi. Some dogs with spirocercosis develop sialoadenosis, a condition identified by non‐inflammatory, painless, bilateral enlargement of the mandibular salivary glands. Development of sialoadenosis in dogs infected with S. lupi occurs as a consequence of neurological stimulation caused by larval migration and oesophageal parasitic nodule formation. This report describes the clinical signs, diagnosis, treatment and the treatment outcome of two dogs diagnosed with sialoadenosis caused by spirocercosis. Phenobarbital therapy is useful to control clinical signs shown by the dogs with sialoadenosis secondary to spirocercosis presented at an early stage of the disease. A more favourable disease outcome is possible when phenobarbital therapy is combined with anti‐parasitic medication effective against S. lupi.

Pink bollworm (Pectinophora gossypiella) movement with respect to rosette flowers in cotton: Novel insights for integrated pest management

Aim: This preliminary study aimed to investigate the movement patterns of Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae) larvae in the rosette flowers. Methodology: Field experiments conducted on the migration behavior of pink bollworm larvae with respect to rosette flowers in cotton fields. Observations included monitoring infested flowers, larval stage duration within rosette flowers, and larval movement to soil for pupation, larval mortality post-drop, and larval migration to early bolls, all conducted without insecticide application to reflect natural conditions. Results: The movement of the larvae was tracked and recorded from the start of flowering to the boll formation stage. Nearly, 44.88% of the larvae present on the infested flowers had moved to the soil for pupation, while 14.29% had moved to newly formed bolls on the same rosette flower. Additionally, 30.90% of the larvae had moved to dry leaf debris on the soil, and the remaining 9.93% either escaped or died due to environmental factors such as damp soil. Notably, the study showed that dry soils or light debris accumulation were the most favorable environments for pink bollworm larvae. Interpretation: The present study has generated useful information regarding the movement of PBWs larvae from rosette flowers to bolls that contribute to infestation. Hence, by implementing integrated pest management strategies during the early crop periods between 60 and 100 DAS, green boll infestations can be avoided and economic yields improved. Key words: Larval movement, Pest carryover, Pest management, Rosette flower

Evaluating alternative compounds for strongyloidiasis therapy: Novel insights from larval migration inhibition test.

Strongyloidiasis is a neglected tropical disease estimated to affect more than 600 million people worldwide. Recently, the World Health Organization road map on neglected tropical diseases 2021-2030 has put the focus on strongyloidiasis, including this disease within its mass drug administration campaigns. With the use of ivermectin in extensive treatment of all populations at-risk, identifying effective therapeutic alternatives is crucial in case ivermectin resistance arises. The objective of the present study was the development of a larval migration inhibition assay to evaluate the anthelmintic efficacy of commercial drugs and diamine and aminoalcohol derivatives against infective Strongyloides ratti third stage larvae. Through this technique, we successfully screened and estimated the in vitro anthelmintic efficacy of six commercial drugs, seven diamine derivatives and eight aminoalcohol derivatives. Unexpectedly, the half-maximal effective concentration of ivermectin and moxidectin (2.21 and 2.34 μM, respectively) were observed as the highest value obtained among all commercial drugs tested by this in vitro technique. Moreover, some diamine and aminoalcohol derivatives showed superior efficacy inhibiting S. ratti motility compared to ivermectin, with five compounds (AA23, AA34, AO2 AO7 and AO14b) also displaying selectivity indexes on HepG2 and Caco2 higher than 1. These findings underscore the potential of these derivatives as promising alternatives for strongyloidiasis treatment, warranting further investigation and in vivo efficacy assessment.

Unidirectional dispersal of blow fly larvae following decomposition fluids from a pig carcass

The decomposition of a body, and the associated gaseous and liquid discharges emanating from it, attract gravid female blow flies which lay their eggs in or on the body. After the eggs have hatched, the emerging larvae start feeding on the body. As decomposition progresses, the blow fly larvae often migrate away, typically in a random manner in search of favourable conditions for pupation. In this paper, we report on a rarely described phenomenon of unidirectional mass migration of blow fly larvae and postulate on the factors which may drive this process. A decomposition trial utilising a 60-kg pig carcass, deployed in the summer months in Table Mountain National Park, Cape Town, South Africa, was conducted in 2022. On the fifth day of the trial, simultaneous unidirectional mass dispersal of blow fly larvae was observed. The larvae moved downhill in a southeasterly direction, following the flow of decomposition fluids oozing out from the pig carcass. The ‘larval migration stream’ had a length of approximately 1.5 m with a width of 40 cm, tapering to 17 cm at the terminal point. The larval migration stream consisted of the larvae of Chrysomya albiceps and Chrysomya chloropyga. This study demonstrates the importance of understanding the timing and pattern of dispersal of post-feeding blow fly larvae in each geographical region. This is crucial as the minimum post-mortem interval can be miscalculated if older immature insects dispersing from the corpse are not considered and collected during crime scene investigations.

Th2-biased immune responses to body migrating Ascaris larvae in primary infection are associated with pathology but not protection

Helminth infections lead to an overdispersion of the parasites in humans as well as in animals. We asked whether early immune responses against migrating Ascaris larvae are responsible for the unequal distribution of worms in natural host populations and thus investigated a susceptible versus a resistant mouse strain. In mice, the roundworm larvae develop until the lung stage and thus early anti-Ascaris immune responses against the migrating larvae in the liver and lung can be deciphered. Our data show that susceptible C57BL/6 mice respond to Ascaris larval migration significantly stronger compared to resistant CBA mice and the anti-parasite reactivity is associated with pathology. Increased eosinophil recruitment was detected in the liver and lungs, but also in the spleen and peritoneal cavity of susceptible mice on day 8 post infection compared to resistant mice. In serum, eosinophil peroxidase levels were significantly higher only in the susceptible mice, indicating functional activity of the recruited eosinophils. This effect was associated with an increased IL-5/IL-13 production by innate lymphoid cells and CD4+ T cells and a pronounced type 2 macrophage polarization in the lungs of susceptible mice. Furthermore, a comparison of wildtype BALB/c and eosinophil-deficient dblGATA-1 BALB/c mice showed that eosinophils were not essential for the early control of migrating Ascaris larvae. In conclusion, in primary infection, a strong local and systemic type 2 immune response during hepato-tracheal helminth larval migration is associated with pathology rather than protection.

Organ-specific Toxocara canis larvae migration and host immune response in experimentally infected mice.

We investigated organ specific Toxocara canis larval migration in mice infected with T. canis larvae. We observed the worm burden and systemic immune responses. Three groups of BALB/c mice (n=5 each) were orally administered 1,000 T. canis 2nd stage larvae to induce larva migrans. Mice were sacrificed at 1, 3, and 5 weeks post-infection. Liver, lung, brain, and eye tissues were collected. Tissue from 2 mice per group was digested for larval count, while the remaining 3 mice underwent histological analysis. Blood hematology and serology were evaluated and compared to that in a control uninfected group (n=5) to assess the immune response. Cytokine levels in bronchoalveolar lavage (BAL) fluid were also analyzed. We found that, 1 week post-infection, the mean parasite load in the liver (72±7.1), brain (31±4.2), lungs (20±5.7), and eyes (2±0) peaked and stayed constant until the 3 weeks. By 5-week post-infection, the worm burden in the liver and lungs significantly decreased to 10±4.2 and 9±5.7, respectively, while they remained relatively stable in the brain and eyes (18±4.2 and 1±0, respectively). Interestingly, ocular larvae resided in all retinal layers, without notable inflammation in outer retina. Mice infected with T. canis exhibited elevated levels of neutrophils, monocytes, eosinophils, and immunoglobulin E. At 5 weeks post-infection, interleukin (IL)-5 and IL-13 levels were elevated in BAL fluid. Whereas IL-4, IL-10, IL-17, and interferon-γ levels in BAL fluid were similar to that in controls. Our findings demonstrate that a small portion of T. canis larvae migrate to the eyes and brain within the first week of infection. Minimal tissue inflammation was observed, probably due to increase of anti-inflammatory cytokines. This study contributes to our understanding of the histological and immunological responses to T. canis infection in mice, which may have implications to further understand human toxocariasis.

Ascaris suum infection in juvenile pigs elicits a local Th2 response in a setting of ongoing Th1 expansion.

Ascaris spp. undergo extensive migration within the body before establishing patent infections in the small intestinal tract of humans and pigs. However, whether larval migration is critical for inducing efficient type 2 responses remains poorly understood. Therefore, we investigated systemic versus local adaptive immune responses along the hepato-tracheal migration of Ascaris suum during primary, single infections in conventionally raised pigs. Neither the initial invasion of gut tissue nor migration through the liver resulted in discernable Th2 cell responses. In contrast, lung-stage larvae elicited a Th2-biased pulmonary response, which declined after the larvae had left the lungs. In the small intestine, we observed an accumulation of Th2 cells upon the arrival of fourth-stage larvae (L4) to the small intestinal lumen. In parallel, we noticed robust and increasing Th1 responses in circulation, migration-affected organs, and draining lymph nodes. Phenotypic analysis of CD4+ T cells specifically recognizing A. suum antigens in the circulation and lung tissue of infected pigs confirmed that the majority of Ascaris-specific T cells produced IL-4 (Th2) and, to a much lesser extent, IL-4/IFN-g (Th2/1 hybrids) or IFN-g alone (Th1). These data demonstrate that lung-stage but not the early liver-stage larvae lead to a locally restricted Th2 response. Significant Th2 cell accumulation in the small intestine occurs only when L4 complete the body migration. In addition, Th2 immunity seems to be hampered by the concurrent, nonspecific Th1 bias in growing pigs. Together, the late onset of Th2 immunity at the site of infection and the Th1-biased systemic immunity likely enable the establishment of intestinal infections by sufficientlylarge L4 stages and pre-adult worms, some of which resist expulsion mechanisms.

Phytochemical analysis and anthelmintic activity of Combretum mucronatum leaf extract against infective larvae of soil-transmitted helminths including ruminant gastrointestinal nematodes

BackgroundSoil-transmitted helminths (STH) infect more than a quarter of the world’s human population. In the absence of vaccines for most animal and human gastrointestinal nematodes (GIN), treatment of infections primarily relies on anthelmintic drugs, while resistance is a growing threat. Therefore, there is a need to find alternatives to current anthelmintic drugs, especially those with novel modes of action. The present work aimed to study the composition and anthelmintic activity of Combretum mucronatum leaf extract (CMLE) by phytochemical analysis and larval migration inhibition assays, respectively.MethodsCombretum mucronatum leaves were defatted with petroleum ether and the residue was extracted by ethanol/water (1/1) followed by freeze-drying. The proanthocyanidins and flavonoids were characterized by thin layer chromatography (TLC) and ultra-high performance liquid chromatography (UPLC). To evaluate the inhibitory activity of this extract, larval migration assays with STH and GIN were performed. For this purpose, infective larvae of the helminths were, if necessary, exsheathed (Ancylostoma caninum, GIN) and incubated with different concentrations of CMLE.ResultsCMLE was found to be rich in flavonoids and proanthocyanidins; catechin and epicatechin were therefore quantified for standardization of the extract. Data indicate that CMLE had a significant effect on larval migration. The effect was dose-dependent and higher concentrations (1000 µg/mL) exerted significantly higher larvicidal effect (P < 0.001) compared with the negative control (1% dimethyl sulfoxide, DMSO) and lower concentrations (≤ 100 µg/ml). Infective larvae of Ascaris suum [half-maximal inhibitory concentration (IC50) = 5.5 µg/mL], Trichuris suis (IC50 = 7.4 µg/mL), and A. caninum (IC50 = 18.9 µg/mL) were more sensitive to CMLE than that of Toxocara canis (IC50 = 310.0 µg/mL), while infective larvae of Toxocara cati were largely unaffected (IC50 > 1000 µg/mL). Likewise, CMLE was active against most infective larvae of soil-transmitted ruminant GIN, except for Cooperia punctata. Trichostrongylus colubriformis was most sensitive to CMLE (IC50 = 2.1 µg/mL) followed by Cooperia oncophora (IC50 = 27.6 µg/mL), Ostertagia ostertagi (IC50 = 48.5 µg/mL), Trichostrongylus axei (IC50 = 54.7 µg/mL), Haemonchus contortus (IC50 = 145.6 µg/mL), and Cooperia curticei (IC50 = 156.6 µg/mL).ConclusionsThese results indicate that CMLE exhibits promising anthelmintic properties against infective larvae of a large variety of soil-transmitted nematodes.Graphical

Effectiveness of an ecological flow regime to assure successful recruitment of anadromous Coregoninae populations in the Rupert River (northern Quebec, Canada)

AbstractObjectiveAs part of a large‐scale hydroelectric project, the mean annual flow of the Rupert River (northern Quebec, Canada) was reduced by 52% at its mouth in 2009. To protect fish habitat, an ecological flow regime that was modulated according to the biological seasons was implemented downstream from the diversion point. An 8‐year monitoring program, including 2 years before partial diversion, was carried out to verify the effectiveness of this mitigation measure on the total annual abundance of anadromous Coregoninae (Cisco Coregonus artedi and Lake Whitefish C. clupeaformis) larvae, which was used as biological indicator of recruitment success. The monitoring also aimed to determine the effects of flow modification on the timing of the larval drift and the spatial distribution of larvae in a river cross section.MethodsEach year, sampling consisted of installing drift nets during the entire downstream larval migration in a river cross section of the lower Rupert River. Drift nets were systematically placed to ensure representative sampling of the river section.ResultPrior to flow reduction, the estimated total number of larvae varied between 1.8 and 8.6 million. Over the following 6 years, the estimated larval population has remained steady at 3–4 million. Otherwise, larval drift characteristics have not changed since the flow reduction, as (1) the duration of the larval drift is the same as before, about 1 month in May and early June, with a peak period of about 8 days; (2) rise in water temperature in spring is a determining factor in the timing of larval drift; and (3) the larvae drift mainly near the surface of the water.ConclusionThe monitoring results indicate that the ecological flow regime implemented in the Rupert River was adequate to maintain anadromous coregonine populations.

Toxocara canis infection in multiple types of animals: ophthalmological and pathological observations.

Human ocular toxocariasis (OT), caused by pet roundworm Toxocara canis (Nematoda Ascaridoidea), is a worldwide ocular parasitic infection that poses a severe threat to eyesight, especially in school-aged children. However, the infection process and pathological mechanism of Toxocara are difficult to study in the human body. This study was designed to explore long-term ocular manifestations in different rodents infected with Toxocara canis, uncovering the specific pathological mechanism and migration pathway of larvae after infection. The three types of experimental animals we selected were C57BL/6 mice, Mongolian gerbils and Brown Norway rats. Mice were randomly divided into five groups and infected orally with 1000, 2000, 4000, 8000 and 10,000 T. canis eggs; gerbils were randomly divided into four groups and infected orally with 1000, 2000, 4000 and 10,000 T. canis eggs; rats were randomly divided into three groups and infected orally with 2000, 6000 and 10,000 T. canis eggs. Their ocular changes were closely observed and recorded for at least 2months. We also enucleated the eyeballs of some animals to perform pathological sectioning and hematoxylin-eosin staining. After 3 dpi (days post-infection), hemorrhagic lesions, mechanical injury of the retina and larval migration could be observed in some infected animals. The ocular infection and mortality rates tended to be stable at 7 dpi. Larval tissue, structure disorder and inflammation could be observed in the pathological sections. In conclusion, the mice infected with 2000T. canis eggs and gerbils infected with 1000, 2000 and 4000T. canis eggs showing obvious ocular lesions and lower mortality rates could provide a basis for long-term observation.

Evaluation of reference genes for gene expression analysis by real-time quantitative PCR (qPCR) in different tissues from mice infected by Ascaris suum

Human ascariasis is the most prevalent helminth infection, affecting 445 million people worldwide. To better understand the impact of the immune system on the pathophysiology of individuals infected with Ascaris suum, mice have been used as experimental models. The RT-qPCR technique is a critical auxiliary tool of investigation used to quantify mRNA levels. However, proper normalization using reference genes is essential to ensure reliable outcomes to avoid analytical errors and false results. Despite the importance of reference genes for experimental A. suum infection studies, no specific reference genes have been identified yet. Therefore, we conducted a study to assess five potential reference genes (GAPDH, 18s, ACTB, B2M, and HPRT1) in different tissues (liver, lungs, small and large intestines) affected by A. suum larval migration in C57BL/6j mice. Tissue collection was carried out to analyze parasite burden and confirm the presence of larvae during the peak of migration in each tissue. Upon confirmation, we analyzed different genes in the tissues and found no common gene with stable expression. Our results highlight the importance of analyzing different genes and using different software programs to ensure reliable relative expression results. Based on our findings, B2M was ranked as the ideal reference gene for the liver, while 18S was the most stable gene in the lung and small intestine. ACTB, or a combination of ACTB with GAPDH, was deemed suitable as reference genes for the large intestine due to their stable expression and less variation between the control and infected groups. To further demonstrate the impact of using different reference genes, we normalized the expression of a chemokine gene (CXCL9) in all tissues. Significant differences in CXCL9 expression levels were observed between different groups in all tissues except for the large intestine. This underscores the importance of selecting appropriate reference genes to avoid overestimating target gene expression levels and encountering normalization-related issues that can lead to false results. In conclusion, our study highlights the significance of using reliable reference genes for accurate RT-qPCR analysis, especially in the context of A. suum infection studies in different tissues. Proper normalization is crucial to ensure the validity of gene expression data and avoid potential pitfalls in interpreting results.

Host‐dependent larval migration and parasitism risk in a polyphagous moth

AbstractFemale herbivorous insects are expected to oviposit on the host plant providing the best performance of the offspring. However, in some insects the larvae are mobile and are not totally dependent on the mother's choice. They can change host plant when conditions for development or exposure to natural enemies vary between individual plants within a patch. Here we study larval migration and preference between two host plants, cotton and alfalfa, in the Egyptian leafworm, Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae). Previous studies have shown that although larval performance is better on cotton, females prefer to oviposit on alfalfa, and this preference corresponds to a higher survival of the eggs. In this study, S. littoralis larvae showed directed movement between host plants and were found to prefer alfalfa over cotton in field test in Egypt, as well as in laboratory selection of feeding site assays. To determine effects by natural enemies, the parasitism rates and various life‐history traits were measured for one larval parasitoid, Microplitis rufiventris Kokujev (Hymenoptera: Braconidae), on several host plants including cotton and clover (equivalent host plant to alfalfa). Overall, parasitism was higher on cotton and parasitoid performance (cocoon mass, adult longevity, and female egg load) was better on cotton compared to clover. This fact suggests an enemy‐free space on clover and alfalfa, as parasitism rate is higher on cotton, and the parasitoid performance is also better on cotton‐fed larvae.

Curcumin-PVP improves the in vitro efficacy of ivermectin against resistant and susceptible Haemonchus contortus

Ivermectin (IVM) resistance in parasitic nematodes such as Haemonchus contortus has spurred a search for substances that help to recover its efficacy. One potential agent is the natural product curcumin (CUR). In this study, CUR was combined with polyvinylpyrrolidone (PVP) (CUR/PVP) to improve its solubility and biological applicability. This study determined the effect of CUR preincubation on the EC50 of IVM in three H. contortus isolates with different susceptibilities to IVM. The IVM effective concentration 50% (EC50) was determined for three H. contortus isolates with different IVM susceptibilities using the larval migration inhibition (LMI) test. The three isolates were (i) PARAISO (IVM resistant), (ii) FMVZ-UADY (IVM susceptible), and (iii) CENID-SAI INIFAP (reference IVM susceptible). The L3 of each isolate were preincubated for 3 h with one of three concentrations of CUR (μg curcumin/mL): CONC-1 (3.67), CONC-2 (5.67), or CONC-3 (8.48). Corresponding controls were performed without CUR. The EC50 of IVM was determined for each isolate after they were exposed to the different CUR concentrations. The EC50 of IVM differed between the isolates PARAISO > FMVZ-UADY > CENID-SAI INIFAP (P < 0.05). The CUR preincubation at CONC-1 did not decrease the EC50 of IVM for any of the three isolates, suggesting a hormetic effect. By contrast, CUR preincubation at CONC-2 or CONC-3 decreased the IVM EC50 for the PARAISO isolate (P < 0.05) compared with the reference isolate and reduced the EC50 of IVM for the FMVZ-UADY and CENID-SAI INIFAP isolates below the EC50 for the CENID-SAI INIFAP isolate without CUR preincubation. In conclusion, Preincubation of H. contortus L3 with CUR reduced the EC50 of IVM for field isolates classified as resistant and susceptible to IVM. The CUR preincubation reduced the IVM RF in the different isolates tested.

The long-lasting Ascaris suum antigens in the lungs shapes the tissue adaptation modifying the pulmonary architecture and immune response after infection in mice

Ascariasis is the most prevalent helminth affecting approximately 819 million people worldwide. The acute phase of Ascariasis is characterized by larval migration of Ascaris spp., through the intestinal wall, carried to the liver and lungs of the host by the circulatory system. Most of the larvae subsequently transverse the lung parenchyma leading to tissue injury, reaching the airways and pharynx, where they can be expectorated and swallowed back to the gastrointestinal tract, where they develop into adult worms. However, some larvae are trapped in the lung parenchyma inciting an inflammatory response that causes persistent pulmonary tissue damage long after the resolution of infection, which returns to tissue homeostasis. However, the mechanism by which chronic lung disease develops and resolves remains unknown. Here, using immunohistochemistry, we demonstrate that small fragments and larval antigens of Ascaris suum are deposited and retained chronically in the lung parenchyma of mice following a single Ascaris infection. Our results reveal that the prolonged presence of Ascaris larval antigens in the lung parenchyma contributes to the persistent immune stimulation inducing histopathological changes observed chronically following infection, and clearly demonstrate that larval antigens are related to all phases of tissue adaptation after infection: lung injury, chronic inflammation, resolution, and tissue remodeling, in parallel to increased specific humoral immunity and the recovery of lung function in mice. Additional insight is needed into the mechanisms of Ascaris antigen to induce chronic immune responses and resolution in the host lungs following larval migration.

Numerical models reveal the suitable habitat area for the stock enhancement and release of marine organism larvae in Liaodong Bay

Stock enhancement can effectively increase population sustainablility and improve fishery resources, making it crucial to discern the suitable habitats for stock enhancement based on efficiency considerations. In this paper, a comprehensive model was established to simulate environmental characteristics in the Liaodong Bay. A habitat suitability model was developed by considering the optimal growth conditions of the Portunus trituberculatus larvae (PTL). The coupled model showed that the optimal area for stock-enhancement with PTL occurs in late June, and the initial suitable habitat area identified represents 17.12% of the whole Liaodong Bay. Based on the larval migration model of PTL, the deviation between the larvae and the suitable habitat, as well as the actual available area for stock enhancement, were further determined after larval release in the initial suitable habitat. Only 33.67% of the larvae fulfilled the criteria of remaining within the suitable habitat for 95% of the time, and these larvae represented 6.19% of the whole area of Liaodong Bay. These findings means that the truly area available for stock enhancement is likely to be a very small portion of the entire bay, and more precise release of larvae will be necessary to ensure survival rates after release. Our study actually provides a methodological framework for the identification of suitable environment of stock enhancement. This methodology can provide technical guidance for the stock enhancement of marine larvae with same applicability for other bays, which in turn contributes to the sustainable use of marine ecosystem services and fisheries resources.

Potential of plant extracts to inhibit egg hatching and migration of Haemonchus contortus larvae

Gastrointestinal parasitosis constitutes important health problems, aggravating throughout the years, due to inadequate use of drugs for its control, causing anthelmintic resistance. The objective of the present study was to evaluate the potential of Azadirachta indica (AZA) and Moringa oleifera (MOR) extracts in inhibiting egg hatching and in vitro migration of Haemonchus contortus larvae. A completely randomized design of experiment was carried out, where 15 treatments and a dimethyl sulfoxide negative control were evaluated: MOR-75, MOR-50, MOR-25, MOR-12.5, and MOR-6.25 mg/mL; AZA-75, AZA-50, AZA-25, AZA-12.5, and AZA-6.25 mg/mL; and thiabendazole (TBZ) TBZ-200, TBZ-100, TBZ-40, TBZ-20, TBZ-10 µg/mL. The extracts did not inhibit egg hatching capacity; however, we observed a motility decrease of up to 100% in L1 larvae. The extracts affected larval migration (P &lt; 0.0020) compared with controls (dimethyl sulfoxide and TBZ), with migration rate inhibition above 65 %. Probit analysis showed that the median effective concentrations were 60.41 and 65.69 mg/mL for M. oleifera and A. indica, respectively. The in vitro results suggest that the water extract of both plants has an anthelmintic action against gastrointestinal nematode larvae.

Post-mortem tissue migration of Anisakis simplex (s.s.) larvae (Nematoda: Anisakidae) in three commercially harvested fish species from the Northeast Atlantic: The role of storage time and temperature

Anisakis simplex sensu stricto is a parasite infecting several commercial fish species in the Northeast (NE) Atlantic, known to be the aetiological agent of the human zoonosis anisakiasis. The present study investigated the response of A. simplex (s. s.) third stage larvae (identified to species level by mtDNA cox2 sequencing) to the storage time and temperature of Atlantic herring (Clupea harengus), Atlantic mackerel (Scomber scombrus) and blue whiting (Micromesistius poutassou) from NE Atlantic fishing areas. A total of 300 fish per species were divided in batches of 50 individuals straight after catch. Each batch was stored at different temperature conditions (2 °C, 5 °C, 15 °C) for different time intervals (24h and 48h). A batch of 50 fish of each species was frozen immediately after catch and used as control (time zero). All fish were inspected by the UV-press method. Blue whiting was the most infected fish species while mackerel harboured the highest proportion of intra-vitam A. simplex (s. s.) larvae in the musculature. In blue withing there was a significant increase in the proportion of larvae in the muscle with increasing storage temperatures (5 °C < 15 °C) and time (24h < 48h). Herring showed a weak trend of increasing parasite infection in the muscle with increasing temperature/time. In contrast, no significant differences of muscle/viscera larval distribution were observed between batches of mackerel stored at different temperatures for different time intervals. Storage temperature and time seem to play a role in the post-mortem motility of A. simplex (s. s.) larvae in herring and blue whiting. Keeping the temperature at ≤ 2 °C seems to prevent post-mortem larval migration into the flesh during fish storage, handling, and transport. Besides abiotic variables, the differences observed in larval post-mortem motility in the different fish species are biologically determined, and attributable to species-specific host-parasite interactions.

Zooplankton-microplastic exposure in Delaware coastal waters: Atlantic blue crab (Callinectes sapidus) larvae case study

High microplastic concentrations in the Delaware Bay have prompted concern regarding harm to local species. We consider the extent to which the zooplankton is exposed to bay-derived microplastics, focusing on Atlantic blue crabs (Callinectes sapidus) during offshore larval migration. We simulate regional flow fields for a spawning season in the Delaware coastal system to advect passive Lagrangian microplastic and zooplankton tracers. Microplastic exposure levels are estimated from tracer distributions. Field sampling of zooplankton and microplastic concentrations for the Delaware Bay mouth and the adjacent shelf in August 2020 is utilized to appraise model performance. Three mechanisms elevating microplastics exposure are identified: zooplankton transport into microplastic-laden tidelines, displacement of microplastics into the buoyant outflow current, and aggregation in offshore plume fronts. Organization via the above mechanisms substantially enhance microplastic exposures over zooplankton migrations (by an average factor of at least 3.8).

Parasites and zoonotic bacteria in the feces of cats and dogs from animal shelters in Carinthia, Austria

Due to their close associations with humans, dogs and cats can be important reservoirs for zoonotic pathogens. In the current study 200 fecal samples of dogs (n = 70 samples) and cats (n = 130 samples) from animal shelters in Carinthia, southern Austria, were examined for the presence of parasites (fecal flotation and larval migration assay) and selected bacteria. Overall, 17.1% of the canine and 38.5% of the feline samples were positive for parasites (p < 0.001), most commonly Giardia duodenalis (dogs and cats), including potentially zoonotic genotypes revealed by multilocus genotyping, and Toxocara cati (cats). Cryptosporidium (C. felis), Cystoisospora spp. (dogs and cats), hookworms (dog), Trichuris (dog) Capillaria hepatica (cats), taeniids (cat), and Aelurostrongylus abstrusus (cat) were also found. Zoonotic bacteria were detected in 10.5% of the samples, Salmonella enterica (dogs), Campylobacter jejuni (dogs and cats) and Yersinia enterocolitica (cat) and were significantly associated with parasite infections in cats but not in dogs. Samples that were positive for several pathogens were common; especially G. duodenalis and T. cati were frequently found in association with each other, other parasites or bacteria. The spectrum of detected pathogens is comparable to that of other dog and cat populations in central Europe. However, since animals from shelters are frequently rehomed, diagnostic measures, appropriate hygiene and therapy as well as training of shelter staff are recommended to prevent zoonotic transmission of enteropathogens to staff or new owners. The presence of heteroxenic parasites, i.e. Aelurostrongylus abstrusus and Taenia taeniaeformis, and spurious excretion of Ca. hepatica in cats, indicates that these animals preyed on intermediate hosts, and that biosafety measures in pet shelters need to be evaluated for their efficacy in the prevention of pathogen transmission.