Chemosensory mechanisms of host seeking and infectivity in skin-penetrating nematodes.

Approximately 800 million people worldwide are infected with one or more species of skin-penetrating nematodes. These parasites persist in the environment as developmentally arrested third-stage infective larvae (iL3s) that navigate toward host-emitted cues, contact host skin, and penetrate the skin. iL3s then reinitiate development inside the host in response to sensory cues, a process called activation. Here, we investigate how chemosensation drives host seeking and activation in skin-penetrating nematodes. We show that the olfactory preferences of iL3s are categorically different from those of free-living adults, which may restrict host seeking to iL3s. The human-parasitic threadworm Strongyloides stercoralis and hookworm Ancylostoma ceylanicum have highly dissimilar olfactory preferences, suggesting that these two species may use distinct strategies to target humans. CRISPR/Cas9-mediated mutagenesis of the S. stercoralis tax-4 gene abolishes iL3 attraction to a host-emitted odorant and prevents activation. Our results suggest an important role for chemosensation in iL3 host seeking and infectivity and provide insight into the molecular mechanisms that underlie these processes.

A sampling of factors relative to the epidemiology of gastrointestinal nematode parasites of cattle in the United States.

Gastrointestinal nematodosis of cattle is a parasitic condition resulting from an immense and seemingly forever-expanding array of factors. Countless determinants influence the incidence and severity of the species-specific infections that occur in cattle, determinants that affect the free-living or environmental stages of the parasites and the parasitic stages. The vast majority of animals have a subclinical or economic level of parasitism undetectable to the eye but quantified more accurately by treatment-induced improved performance (e.g., feed efficiency, nitrogen balance, weight gain, milk production). Unfortunately, the results of treatment (effectiveness and improved animal performance) sometimes can be as varied as the parasitisms that are being treated.

More parasitic myositis cases in humans in Australia, and the definition of genetic markers for the causative agents as a basis for molecular diagnosis.

Since 1998, there have been six reported human cases of myositis in Australia, attributable to infection with the nematode Haycocknema perplexum. However, an unequivocal diagnosis of H. perplexum infection and associated disease has been seriously compromised by a lack of molecular markers for this nematode. Here, we report new cases of disseminated myositis in two male patients from the states of Queensland and Tasmania in Australia, respectively; genetically characterize the causative agent from each case; and, also establish a PCR-based sequencing approach as a tool to support the diagnosis of future cases and to underpin epidemiological studies.

Prevalence and risk factors for protozoan and nematode infections among children in an Ecuadorian highland community.

In order to create a parasite prevention program for Santa Ana, Ecuador, we worked with local physicians to identify the prevalence and risk factors for intestinal parasitic infection among children. Two hundred households were randomly selected and asked to submit three stool samples from a selected child. Information from direct observation and questionnaires was used to determine environmental and behavioral risk factors for parasitic infection. Prevalence of any parasitic infection was 65.6% of the 189 children who submitted fecal samples. Parasitic infections included Entamoeba histolytica/E. dispar (46.6%), Giardia lamblia (18.5%) and Ascaris lumbricoides (20.1%). In a multivariate logistic model, risk factors (P<0.05) for E. histolytica/E. dispar included >1 month since antiparasitic treatment, not adding chlorine to drinking water, children not washing their hands before eating, and having a fewer number of electrical appliances in the home. The risk factor identified for G. lamblia was children not washing their hands before eating. Risk factors for A. lumbricoides included >6 months since antiparasitic treatment and having a fewer number of electrical appliances in the home. This study may have implications for other communities throughout the developing world.

Raccoon ascarid larvae (Baylisascaris procyonis) as a cause of ocular larva migrans.

Larvae of the common raccoon roundworm, Baylisascaris procyonis, are known causes of visceral larva migrans and CNS disease in animals and human beings. In the present experiments we examined the ability of B. procyonis to cause ocular larva migrans (OLM) in subhuman primates, as an indication of its possible ocular zoonotic importance. Squirrel monkeys given 5,000 or 10,000 infective B. procyonis eggs per os and cynomolgus monkeys given 20,000 eggs had clinical and histologic evidence of OLM, beginning 7 days after inoculation. Clinically, multifocal retinal hemorrhages, white spots, chorioretinitis, inflammatory tracks, vascular sheathing, diffuse retinal degeneration, and motile intraretinal larvae were seen. Histologically, primarily subretinal larvae caused varying degrees of retinal disruption, degeneration and necrosis, retinitis, vasculitis, and perivascular sheathing, primarily with eosinophils. Larvae were also present in choroidal granulomas. It was concluded that B. procyonis larvae have marked ability to produce OLM in subhuman primates following oral infection and should be considered as a possible etiology in human ocular disease.

Studies on caprine responsiveness to nematodiasis: segregation of male goats into responders and non-responders.

Eighty-three 2-4-year-old intact male goats exposed to a combination of artificial and natural challenge were segregated into responders and non-responders by ranking of weekly faecal egg counts (FECs). Retrospective analysis of samples over a 15-week-period showed responders had a statistically lower mean FEC than non-responders. Estimates of repeatability between consecutive egg counts were significant in both groups. The 6 top responders and bottom non-responders were subsequently given an artificial trickle challenge with Teladorsagia circumcincta and Trichostrongylus vitrinus. Mean faecal egg output was significantly lower in responders than non-responders. Peripheral eosinophil numbers following challenge were significantly greater in responder than non-responder goats. Abomasal and intestinal worm burdens were considerably lower in responders, with evidence of retardation of worm development compared to non-responders. Both abomasal and jejunal tissue eosinophil numbers were significantly higher in responders, although there was no difference in mucosal mast cell or globule leucocyte numbers. These results suggest that under temperate climatic conditions, it is possible to segregate male goats into responders and non-responders on the basis of simple parasitological criteria.

Eosinophilic meningoencephalitis due to Angiostrongylus cantonensis as the cause of death in captive non-human primates.

Fatal eosinophilic meningoencephalitis due to Angiostrongylus cantonensis is reported in captive non-human primates. A howler monkey (Alouatta caraya) at the Audubon Park and Zoological Gardens, New Orleans, LA, died 21 days after initial clinical symptoms. A white-handed gibbon (Hylobates lar) died at the Ardastra Gardens and Zoo, Nassau, Bahamas, 17 days after onset of symptoms. Both had access to free-ranging gastropods within the zoos. These are the first reported cases of natural infection by A. cantonensis in non-human primates in the western hemisphere.

Parasitic diarrhea in normal and malnourished children.

Diarrhea is only one of the many manifestations of intestinal parasites. Environmental influences are inescapable, regardless of an individual's state of health: in a highly endemic region, intestinal parasitic colonization is almost the rule. The clinical expression of the parasitoses, however, is largely determined by host defenses; and when they are weakened, parasitic diarrhea is frequent and severe. Protein-energy malnutrition is by far the most important cause of immune deficiency in developing countries. Diarrhea caused by Strongyloides or Giardia is common and severe in malnourished children, while well-nourished children remain healthy carriers. These parasites require specific treatment in the malnourished; and the well-nourished should have preventive treatment when they are to receive corticosteroids or immunosuppressive agents. Diarrhea caused by Cryptosporidium spp. may be severe in malnourished or immunodeficient children, and recovery is achieved only after renutrition or treatment of the immunodeficiency.

Human gnathostomiasis.

Following a meal that included raw fish in Bangladesh, a woman aged 40 years had symptoms suggestive of gnathostomiasis. The presentation of her illness and the results of investigations are reported.

Meningo-encephalomyelitis due to the saprophagous nematode, Micronema deletrix.

A five-year-old boy succumbed 24 days following an unusual farm accident in which considerable manure was deposited in multiple lacerations. Death was due to an extensive meningo-encephalomyelitis caused by a nematode that is ordinarily saprophagous.

Comparative susceptibility of Pyrenean and Brown Swiss calves to gastrointestinal nematodes in subclinical naturally acquired infections.

The susceptibility of two common breeds of cattle in the Pyrenees, Brown Swiss and Pyrenean breed, to parasitism by gastrointestinal nematodes was studied. Twenty-two female calves (13 Brown Swiss and 9 Pyrenean), 3 months old with a mean weight of 112.8 +/- 18.33 and 103.3 +/- 17.11 kg respectively at the start of the study, were used. The calves began their first grazing season grazing with 200 cattle following the traditional grazing system for mountainous areas: Stabling during winter (December-April), grazing on harvesting meadows at an elevation of 900 m in the spring (May-June) and autumn (October-November), and grazing areas between 1200-2100 m during the summer (July-September). Faeces, blood samples and calves growth rate were taken at 2-week intervals throughout the grazing season. Faecal egg counts of gastrointestinal nematodes, level of serum pepsinogen, total serum protein and blood parameters were measured. The worm egg counts and Cooperia sp. counts were significantly smaller in the calves of Pyrenean breed than in Brown Swiss throughout the experiment. Numbers of eggs of the other genera of parasites found were smaller in the calves of Pyrenean breed than in calves of Brown Swiss breed, but no statistical differences were found. Blood was compared during two periods: the prepatent and patent periods. During the first period, no differences were found between the breeds for any parameter studied. However, during the patent period, Pyrenean animals had significantly greater numbers of erythrocytes, haemoglobin values and packed cell volume (PCV) values, and smaller numbers of eosinophils than animals of the Brown Swiss breed. No differences were found in the level of serum pepsinogen, total serum protein and live weight gains between the two breeds.

Pathogenesis of helminths in equines.

This review summarizes information on the clinical signs, gross and microscopic lesions associated with nematode and cestode infections and discusses the development of these conditions in the equine host.

Comparative effects of nematode infection on Bos taurus and Bos indicus crossbred calves grazing on Argentina's Western Pampas.

Breed differences in resistance or tolerance to naturally acquired gastrointestinal nematodes were compared between Aberdeen Angus (AA) and Santa Gertrudis (SG) weaned steer calves grazing in a temperate environment. Within breeds, one half of the calves was untreated: AAU (n = 17) and SGU (n = 18) while the other half was treated with moxidectin monthly: AAT (n = 14) and SGT (n = 14). All calves were grazed on the same contaminated pasture from autumn to winter, when each group was separated to uninfected paddocks for the remaining period of the study. Faecal egg counts, plasma pepsinogen levels (PPL), herbage larval counts and liveweight (LW) were recorded monthly. Egg counts and PPL of AAU and SGU increased from autumn to early winter when calves showed heavy parasitism (mainly Trichostrongylus axei) and severely sick calves needed emergency treatment. On the clean paddocks, parasitological parameters progressively decreased. Late winter egg counts were higher (P < 0.05) in SGU than in AAU. PPL of SGU were higher than AAU ones, but no significant differences were detected. Larval differential counts of SGU showed fewer Cooperia (P < 0.08) and higher T. axei (P < 0.002) proportions than those of AAU. Numbers of severely sick and dead SGU calves (61%) were greater (P < 0.01) than those numbers of AAU calves (17.5%). Cumulative LW gains differences within SG breed were higher (P < 0.0001) than those differences within AA breed (P < 0.003). LW gains of AAU during autumn-winter period were greater (P < 0.002) than those of SGU.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of nematode infections of the gastrointestinal tract in Angora and dairy goats in a rangeland environment: relations with the feeding behaviour.

A study was conducted in order to examine the possible influence of feeding behaviour on differences in the diversity and the intensity of nematode infections of the gastrointestinal tract between two breeds of goats placed in the same rangeland environment. Within the same flock bred on rangeland conditions, 10 Saanen dairy goats and 14 Angora goats were surveyed for 5 months (from May to September) and parasitological and behavioural parameters were measured. The level of nematode infection was estimated by monthly measurements of faecal egg counts whereas the feeding behaviour was assessed every fortnight. During the whole survey, nematode egg excretion was repeatedly higher in the Angora goats compared to the Saanen ones and significant differences were observed in May and September. This difference in egg excretion was related to major difference in feeding behaviour between the two breeds. In contrast with the Saanen does, Angora goats did not show any browsing and resting activities at any date of observation. Hence, Angora goats can be considered mainly as grazers whereas Saanen goats exhibit feeding activities close to browsers. The relative influence of feeding behaviour and host immune response on the susceptibility to gastrointestinal nematode infection in goats is discussed.

Seasonal occurrence of infective nematode larvae in California Sierra foothill pastures grazed by cattle.

Worm-free Holstein tracer calves were used to assess the seasonal variation in number and course of development of nematode parasites of cattle on an irrigated pasture located in the California Sierra foothills. The most common genera of nematodes found in the abomasum and small intestine were Ostertagia and Cooperia, respectively. The infective Ostertagia larvae on herbage were most numerous in early spring and lowest in summer months. Arrested development of Ostertagia occurred in mid-to-late spring. The percentage of the population of Ostertagia found to be arrested larvae was constant (73% to 95%) over 4 years, even though the total number of nematodes in the genus was markedly different. Levels of infection with Ostertagia and Cooperia were found to correlate with pasture contamination occurring in the preceding fall and concurrent winter months. In the cecum and large intestine, Oesophagostomum venulosum was found to be the most common nematode. It is suggested that this species may replace Os radiatum as the cattle nodular worm in regions where climate is similar to that of the southwestern coast of North America. Evidence of seasonal hypobiotic development of Oe venulosum was found. Other genera of nematodes observed in tracer calves were Trichostrongylus, Haemonchus, Bunostomum, Trichuris, and Dictyocaulus.

Anthelmintic activity of the macrocyclic lactone F28249-alpha in sheep.

The macrolytic lactone F28249-alpha was titrated in experimentally infected sheep and found to be highly effective against most of the common gastrointestinal nematodes as a single oral dose, given at a rate of 0.025, 0.05, or 0.1 mg/kg. Specifically, maximal activity was evident at even the lowest dosage against adult Haemonchus contortus, Ostertagia circumcinta, Trichostrongylus axei, and T colubriformis and L4 O circumcinta. Activity against Oesophagostomum columbianum was also high at all dosages, with a calculated ED95 of 0.029 mg/kg. Cooperia curticei was eliminated at 0.1 mg/kg, but control was erratic at the lower dosages. The greatest weakness of this compound was its activity against C oncophora. The activity against this parasite was weak (less than or equal to 85%) at all dosages, and the dosage-response curve was flat, suggesting dosages substantially higher than those given would be necessary for high-order control of this species.

Intestinal capillariasis from Maha Sarakham Province, northeast Thailand: report of a case.

Intestinal capillariasis cases in Thailand were reported from the areas where people customarily ate raw freshwater fish. The present case came from Maha-Sarakham Province, Northeast of Thailand with the chief complaint of diarrhoea for one month. Eggs, larvae and adult Capillaria philippinensis were found in the faeces. The authors observed that protein-losing enteropathy was an early manifestation on this disease.

Pathological findings in four cases of human angiostrongyliasis.

Three adults and a 3 1/2-year-old child presented with eosinophilic meningitis. A history of consumption of raw snails was elicited in 2; evidence of a constant diet of raw food, in the form of opisthorchiasis and taeniasis, as well as angiostrongyliasis, was present in the third; no history of raw food ingestion was obtained in the fourth, the child. Pathologic changes were similar in all 4 cases. There was infiltration of the meninges and around intracerebral vessels by varying proportions of lymphocytes, plasma cells and eosinophils. Numerous tracks and microcavities were found in the brains, and in the spinal cords in 2 cases, varying in size from 0.1 to 2 mm, and in age, with older tracks containing debris and gitter cells, newer tracks showing disruption of brain tissue, with and without haemorrhage. Numerous 4th and 5th stage Angiostrongylus larvae, alive and dead, were found in the meninges and brain tissue, sometimes in blood vessels or perivascular spaces, in 3 cases; in the fourth case a 5th stage larva was found on the surface of the right frontal lobe. In one case a degenerating larva was found in a pulmonary vessel. Cellular reaction was more often associated with dead larvae.

[Seroepidemiological data on anisakiasis: prophylactic consequences in fish products]. / Données séroépidémiologiques sur l'anisakiase: conséquences prophylactiques pour les produits de la pêche.

The Western blotting method allowed us to confirm the diagnosis in 7 cases of acute anisakiasis, to assess it in 5 cases of chronic anisakiasis, and to follow up the evolution. These chronic frames according to the question of their long term evolution, and the part played by Anisakis simplex in fish nutritional allergy increase the negative score of that parasite. This situation should leave to discuss preventive rules.

[Mechanism of distribution of Strongyloidea larvae among ungulate animals at pasture]. / O makhanizme rasseleniia lichinok strongiliat kopytnykh na pastbishche.

The problem of dissimilation of larvae of strongylates of ruminants in pasture biocoenosis is discussed. A new form of their migration in horizontal direction on the basis of negative geotaxis is suggested. As a result of alternation of vertical migration of larvae on the tilting leaves of the grass and their subsequent washing off with rain or dew down on the ground proceeds their distribution on the pasture. The description of corresponding experiments is given.