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PubMed2006

Effect of Steinernema glaseri-infected host exudates on movement of conspecific infective juveniles.

The entomopathogenic nematode's decision to infect a host is paramount because once the decision is made it is irrevocable; nematodes that invade a host either develop and achieve reproductive success, or they die. Entomopathogenic nematodes that have a cruiser foraging behavior, such as Steinernema glaseri, follow host-associated cues to locate insects to infect. Most of the host finding and infection dynamics research has focused on the infective juvenile nematodes' responses to cues from live insects such as host-associated volatiles and host contact cues. Few studies focus on how previously infected hosts influence infective juvenile infection behaviors. We investigated how exudates from nematode-infected hosts affect the behavior of S. glaseri infective juveniles. We hypothesized that the infective juvenile's behavioral response to cadavers would change as the state of a nematode-infected host changes during pathogenesis. We examined the effect of exudates collected from infected hosts on infective juvenile locomotory behavior. We detected no effects on nematode repulsion or attraction from exudates produced within the first 48h post-infection. We observed repulsion from accumulated exudates during the 3-48, 3-72, 3-120, and 3-144h intervals. Repulsion from exudates was observed during the 48-66, 72-90, and 120-138h intervals in experiments evaluating daily exudate emissions. The repellent effect of infected host exudates may result in an infective juvenile discriminating between suitable and unsuitable hosts.

Animals↗
PubMed1997

Efficacy of doramectin against intestinal nematodes and sarcoptic manage mites in naturally infected swine.

Endectocidal efficacy of doramectin administered intramuscularly at a dosage of 300 micrograms/kg was evaluated in 464 pigs naturally infected with intestinal nematodes or mange mites on 14 commercial farms in Japan. By doramectin treatment, fecal egg counts were reduced > 99% for Ascaris suum, Strongyloides ransomi, Oesophagostomum dentatum, and Trichuris suis; worm counts of T. suis and mite counts of Sarcoptes scabiei reduced 90.1% on Day 21 and 99.5% on Day 28 following treatment, respectively.

Animals↗
PubMed1977

Cellular changes in the intestinal lymph of sheep infected with the enteric nematode, Trichostrongylus colubriformis.

Some changes produced in the cell populations of intestinal lymph by infection with the enteric nematode, Trichostrongylus colubriformis, were studied in sheep regularly re-infused with all discharged lymph. Lymphocyte traffic through the intestinal lymphatic duct was reduced until day 35 of primary infection, mainly due to the absence of lymphocytes with smaller cell volumes, but was increased two-fold after day 70 and in immune sheep. Antigen-reactive lymphocytes in blood and lymph were assayed by the uptake of 3H-thymidine in cell culture stimulated by extracts from the larvae of T. colubriformis. Cells from the blood and lymph of immune sheep were highly reactive to worm antigen. A relatively smaller reactivity was present in the blood of worm-free sheep and was abolished during the first 12 days of primary infection. Antigen reactive cells were not detected in intestinal lymph until 12 days after primary infection, and in vitro antigen reactivity in intestinal lymph of immune sheep was increased after challenge with infective larvae. Responses to the mitogens, concanvalin A and phytohaemagglutinin, in cultures of cells from both intestinal lymph and blood were depressed on days 7 and 12 of primary infection. It is proposed that the diminished traffic of lymphocytes in intestinal lymph and the reduced numbers of mitogen and nematode antigen-reactive lymphocytes in both blood and intestinal lymph during the early stages of infection with T. colubriformis is closely related to the slow development of protective immunity to this parasite.

Animals↗
PubMed2006

A nematode allergen elicits protection against challenge infection under specific conditions.

We describe tropomyosin of the filarial nematode Acanthocheilonema viteae as an allergen and study its protective potential in the natural rodent host Meriones unguiculatus (jird). Jirds immunized with recombinant E. coli-expressed A. viteae tropomyosin emulsified in alum were not protected, while immunization with recombinant A. viteae tropomyosin or with protein purified from worms together with the adjuvant STP led to reduction of adult worm burdens by 30%. Vaccination with cDNA induced protection of about 30%, while application of cDNA together with aluminium phosphate increased the protection to >40%. Our data suggest that vaccination with tropomyosin under Th1 conditions, which are atypical for nematode infections, induces protection via an antibody independent effector mechanism.

Allergens↗
PubMed1995

Haemopoietic cell responses in the blood and bone marrow of sheep infected with the abomasal nematode Telodorsagia circumcincta.

The generation of bone marrow and blood haemopoietic progenitor colony-forming cells (CFCs) in sheep given primary or challenge infections with the nematode parasite Telodorsagia circumcincta is described. Ten days after a primary infection, the frequency of early multipotential-CFCs, eosinophil-CFCs, macrophage-CFCs and mast cell or basophil-CFCs was greater than in controls. These frequencies then declined to pre-infection levels by day 21. Blood CFCs (mainly macrophage-CFCs and eosinophil-CFCs) also increased after infection, indicating a migration of CFCs, presumably to the site of infection. Ten days after challenge infection there was less marked myelopoiesis than in the primary infection on day 10, though both eosinophil-CFCs and mast cell or basophil-CFCs were significantly above control values. Blood CFC output (mainly macrophage-CFCs and eosinophil-CFCs) reached a peak 2-6 days after challenge, evidence of rapid recruitment to the site of infection. Telodorsagia circumcincta infection is therefore associated with an increase in myelopoiesis, particularly for the cell types characteristic of the local inflammatory response to abomasal nematodes. There was no correlation between any of the haemopoietic cell responses measured and worm burdens in individual animals after either primary or challenge infection.

Animals↗
PubMed2001

Effects of parenteral administration of doramectin or a combination of ivermectin and clorsulon on control of gastrointestinal nematode and liver fluke infections and on growth performance in cattle.

OBJECTIVE: To compare effects of an injectable doramectin preparation with those of an injectable ivermectin-clorsulon preparation on control of gastrointestinal nematodes and liver flukes and on growth performance in cattle. DESIGN: Randomized complete block design. ANIMALS: 60 crossbred calves. PROCEDURES: Calves (20/treatment group) were treated with doramectin or ivermectin-clorsulon or were not treated. Fecal samples were collected for nematode and Fasciola hepatica egg counts on day 0 and for up to 140 days after treatment. Cattle were weighed before treatment and at 28-day intervals until day 140. RESULTS: From day 7 through day 49, nematode egg counts for calves treated with doramectin or with ivermectin-clorsulon were significantly lower than those for untreated control calves. As the study progressed beyond day 56, the percentages of cattle with fluke eggs in their feces increased, but differences in regard to these percentages were not detected among the 3 groups. Average daily gain for the doramectin-treated cattle (0.79 kg/d [1.74 lb/d]) was significantly greater than that for the cattle treated with ivermectin-clorsuIon (0.71 kg/d [1.56 lb/d]); values for both groups were significantly greater than that for the control cattle (0.62 kg/d [1.37 lb/d]). CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that doramectin had a greater impact on subclinical gastrointestinal tract parasitism in calves, as demonstrated by growth performance, than did ivermectin-clorsulon. In the Gulf Coast region of the United States, spring-born nursing beef calves may have minimal grazing exposure to F hepatica during the peak fluke transmission period; therefore, mature fluke burdens may be negligible at the beginning of the fall season.

Animals↗
PubMed2000

Mucosal mast cell responses are not required for protection against infection with the murine nematode parasite Trichuris muris.

The involvement of mucosal mast cells (MMC) in protection against infection with the murine nematode parasite Trichuris muris was studied in genetically mast cell-deficient WBB6F1-W/Wv mice and their normal littermates WBB6F1-+/+ mice. Expulsion of T. muris worms occurred in infected +/+ mice, whereas no worm expulsion was observed in infected W/Wv mice where the infection persisted until at least day 46 postinfection. No MMC responses were induced in either infected W/Wv or +/+ mice. Specific IgG1and IgG2a antibodies to T. muris excretory/secretory antigens were observed in infected W/Wv and +/+ mice, and antibody production showed similar kinetics. Interleukin 4 production by concanavalin A (Con A)-stimulated mesenteric lymph node cells (MLNC) was induced preferentially in infected +/+ mice. T. muris infection increased the levels of IFN-gamma produced by Con A-stimulated MLNC of infected W/Wv and +/+ mice, with the levels of IFN-gamma in infected W/Wv mice being higher than those in infected +/+ mice. Taken together, these results indicate that W/Wv and +/+ mice are susceptible and resistant to T. muris infection, respectively, and that MMC responses are not required for protective immunity.

Animals↗
PubMed2003

Functional consequences of genetic diversity in Strongyloides ratti infections.

Parasitic nematodes show levels of genetic diversity comparable to other taxa, but the functional consequences of this are not understood. Thus, a large body of theoretical work highlights the potential consequences of parasite genetic diversity for the epidemiology of parasite infections and its possible implications for the evolution of host and parasite populations. However, few relevant empirical data are available from parasites in general and none from parasitic nematodes in particular. Here, we test two hypotheses. First, that different parasitic nematode genotypes vary in life-history traits, such as survivorship and fecundity, which may cause variation in infection dynamics. Second, that different parasitic nematode genotypes interact within the host (either directly or via the host immune system) to increase the mean reproductive output of mixed-genotype infections compared with single-genotype infections. We test these hypotheses in laboratory infections using genetically homogeneous lines of Strongyloides ratti. We find that nematode genotypes do vary in their survivorship and fecundity and, consequently, in their dynamics of infection. However, we find little evidence of interactions between genotypes within hosts under a variety of trickle- and single-infected infection regimes.

Animals↗
PubMed1979

Relative importance of winter survival of larval nematodes in pasture and infected carrier calves in a study of parasitic gastroenteritis in calves.

A study was done in Maine to determine the relative importance of winter survival of nematode larvae in pasture and infected carrier animals as sources of infection for susceptible calves. Under the conditions of the experiment, it appeared that winter survivals in pasture of the infective stages of the genera Ostertagia, Cooperia, Nematodirus, and Trichostrongylus were of greater importance than carrier animals as sources of infection for susceptible calves. While animals in plots infected the previous summer and simultaneously allowed to graze alongside infected carrier animals did show more worms than those grazed only in infected plots, these differences were not statistically significant. Both groups had significantly (P greater than 0.01) more worms than did calves grazed only with carrier animals for the period of the experiment (8 weeks). It was also observed that carrier calves with low fecal egg counts (less than 200 eggs/g of feces) introduced in early spring to uncontaminated pasture could produce enough parasitic contamination by early fall to cause fulminating infections in susceptible calves grazing the pasture at the same time. Infected animals that survived clinical disease during their 1st summer developed a strong immunity which limited their acquisition of further infections when they were exposed to severe pasture contamination the following year.

Animals↗
PubMed1996

Responses in milk production to control of gastrointestinal nematode and paramphistome parasites in dairy cattle.

OBJECTIVE: To determine the effect of treating naturally acquired gastrointestinal nematode and paramphistome infections on milk production in dairy cattle. DESIGN: A field trial. ANIMALS: One thousand two hundred and thirty nine dairy cows. PROCEDURE: Cows were either not treated or treated with 4.5 mg/kg oxfendazole, 16.6 mg/kg oxyclozanide or 4.5 mg/kg oxfendazole and 16.6 mg/kg oxyclozanide in March, May and August. RESULTS: A significant increase in milk production, averaging 0.4 L (SE 0.2) per day, was seen when dairy cows infected with gastrointestinal nematodes and paramphistomes were treated with oxfendazole or oxfendazole and oxyclozanide in March, May and August. Cows treated with oxyclozanide alone at these times produced no more milk than untreated cows. Faecal egg counts confirmed that oxyclozanide treatment reduced paramphistome populations and oxfendazole treatment reduced nematode populations in cows over the 7-month monitoring period. CONCLUSION: When dairy cows infested with gastrointestinal nematodes and paramphistomes were treated with oxfendazole alone or oxfendazole and oxyclozanide in March, May and August milk production increased.

Animals↗