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PubMed2004

Molecular characterization, expression, and in vivo analysis of LmexCht1: the chitinase of the human pathogen, Leishmania mexicana.

Chitinases have been implicated to be of importance in the life cycle development and transmission of a variety of parasitic organisms. Using a molecular approach, we identified and characterized the structure of a single copy LmexCht1-chitinase gene from the primitive trypanosomatid pathogen of humans, Leishmania mexicana. The LmexCht1 encodes an approximately 50 kDa protein, with well conserved substrate binding and catalytic domains characteristic of members of the chitinase-18 protein family. Further, we showed that LmexCht1 mRNA is constitutively expressed by both the insect vector (i.e. promastigote) and mammalian (i.e. amastigote) life cycle developmental forms of this protozoan parasite. Interestingly, however, amastigotes were found to secrete/release approximately >2-4-fold higher levels of chitinase activity during their growth in vitro than promastigotes. Moreover, a homologous episomal expression system was devised and used to express an epitope-tagged LmexCht1 chimeric construct in these parasites. Expression of the LmexCht1 chimera was verified in these transfectants by reverse transcription-PCR, Western blots, and indirect immunofluorescence analyses. Further, results of coupled immunoprecipitation/enzyme activity experiments demonstrated that the LmexCht1 chimeric protein was secreted/released by these transfected L. mexicana parasites and that it possessed functional chitinase enzyme activity. Such transfectants were also evaluated for their infectivity both in human macrophages in vitro and in two different strains of mice. Results of those experiments demonstrated that the LmexCht1 transfectants survived significantly better in human macrophages and also produced significantly larger lesions in mice than control parasites. Taken together, our results indicate that the LmexCht1-chimera afforded a definitive survival advantage to the parasite within these mammalian hosts. Thus, the LmexCht1 could potentially represent a new virulence determinant in the mammalian phase of this important human pathogen.

Amino Acid Sequence↗

PubMed1994

[New interpretation of the quantitative fecal examination in humans].

The pattern of spatial disposition of eggs of the parasites (Ascaris lumbricoides, Trichuris trichiura and Ancylostomidae) into the faeces was found overdispersed, independently of the technique of coprodiagnosis used (Direct smear without standarisation, Stoll, Shore & Lynch, Kato-Katz and Mc Master). Therefore, differences were not detected in the interpretation of the results among the techniques at the population level, in quantitative studies. In an overdispersed pattern, only few hosts are the major responsibles for the environmental contamination. The importance of this spatial arrangement for parasite control purposes, is discussed.

Adolescent↗

PubMed1994

Maternal transmission of immunity to Eimeria maxima: enzyme-linked immunosorbent assay analysis of protective antibodies induced by infection.

Vaccination of broiler chickens against Eimeria infection is problematic because of the need to ensure that birds are protected from the time of hatching. We have therefore investigated the feasibility of protecting hatchling broilers via maternal transfer of protective antibodies from hens to their offspring. Oral infection of broiler breeder hens with 20,000 sporulated Eimeria maxima oocysts caused production of antibodies which were passed into the egg yolk and subsequently to hatchlings. The level of specific antibodies in the yolks to unsporulated oocysts, sporulated oocysts, merozoites, and gametocytes was assessed by enzyme-linked immunosorbent assays. The levels in yolks of antibodies to all developmental stages peaked 3 to 4 weeks after infection of the hens. Groups of 10 hatchlings were challenged at 3 days of age by oral infection with 100 sporulated E. maxima oocysts. In the first experiment, the mean 4-day (days 6 to 9 post-infection) total number of oocysts excreted in the feces of chicks from eggs collected 3 weeks after infection of the hens was (0.6 +/- 0.4) x 10(6) (mean +/- standard error) compared with (9.9 +/- 1.4) x 10(6) for the progeny of uninfected hens, which represents a greater than 90% reduction. However, oocyst excretion by chicks from eggs collected 7 or 8 weeks after infection of the hens was only 47 or 68% lower than control values, reflecting declining levels of protective antibodies. In a second experiment, in which the hens were somewhat older and pretreated by intramuscular injection of saline in the emulsifying agent, Arlacel A, the period for which protective antibodies were transferred to hatchlings was prolonged. Thus, oocyst excretion by challenged hatchlings from eggs collected for an 8-week period after infection of the hens was more than 90% lower than oocyst excretion by control chicks, and even hatchlings of eggs collected 19 weeks after infection of the hens showed a 60% reduction in oocyst output. In both experiments, the levels of immunoglobulin G (IgG) antibodies to all developmental stages in yolks or hatchling sera were very strongly correlated with maternally derived immunity to E. maxima. In contrast, parasite-specific IgM or IgA was not detectable, either in egg yolk or egg white. These results demonstrate the ability of IgG antibodies to protect against E. maxima in poultry, thus raising the possibility of using protective maternally derived IgG antibodies to identify potentially protective parasite antigens and indicating the feasibility of using maternal immunization as a means for parasite control.

Animals↗

PubMed2000

Using genetics to control cattle parasites-the Rockhampton experience.

Ever since their accidental introduction, cattle ticks, gastrointestinal nematodes and buffalo flies have been major parasites of cattle in northern Australia. Enormous effort and resources have been directed at chemical control of these parasites but the problem persists in undiminished form. The principal control measure remains the use of breeds that have some degree of parasite resistance. No breed is completely resistant and all are at times adversely affected by parasites. Complete resistance is the ultimate solution but has been generally ignored as a commercial reality. Studies at Rockhampton have demonstrated that completely resistant lines can be developed by genetic means within a commercially acceptable timeframe from even the most parasite-susceptible breeds. Genetic changes in tick and worm resistance over 15 years in response to selection for increased tick resistance in the Belmont Adaptaur (Bos taurus) line are reported. Costs and benefits of achieving increased tick resistance are examined and the applicability of the results to other breeds is discussed. Breed differences in resistance to buffalo flies and their effects on live weight are also reported and the possibility of selecting for increased buffalo fly resistance is explored.

Animals↗

PubMed2006

Neospora caninum in wildlife.

Neosporosis, which is caused by the coccidian parasite Neospora caninum, is recognized as a major disease of domestic animals that causes high abortion rates in cattle and fatal neurological disease in dogs. A life cycle of N. caninum in wild animals (i.e. sylvatic) has long been suspected because neosporosis has been detected in several wildlife species. Recently, the transmission of N. caninum has been confirmed in coyotes and white-tailed deer. The newly confirmed wild hosts and other wild animals are probably involved in the sylvatic cycle of the parasite. Control measures for neosporosis could now become more complicated, given the participation of wildlife in the life cycle of N. caninum.

Animals↗

PubMed1997

Immunological control of Trypanosoma cruzi infection and pathogenesis of Chagas' disease.

The major goal of studies on immunity to Trypanosoma cruzi is the understanding of immunological mechanisms involved in resistance to this protozoan as well as the pathogenesis of Chagas' disease. Different studies have defined CD8+ T lymphocytes, IFN-gamma and macrophages as important elements controlling parasite replication during the acute phase of infection. In contrast, during the chronic stage of the disease parasite-specific antibodies that fix complement and lyse the blood from trypomastigotes are thought to be the main effector molecules responsible for maintaining latent infection. In both acute and chronic infection with T. cruzi CD4+ Th1 lymphocytes appear to be the main cells responsible for induction of protective immunity. The immunological mechanisms involved in the pathogenesis of Chagas' disease are much more controversial. CD8+ lymphocytes are thought to be the main effector cells responsible for cardiac tissue destruction. Although many experiments suggest the involvement of autoimmunity in the pathogenesis of Chagas' disease, recent studies both in mice and humans indicate a positive association of tissue parasitism, inflammation and severity of pathology induced by T. cruzi. Finally, T. cruzi has emerged as an important opportunistic pathogen in patients infected with HIV and presenting low numbers of CD4+ T lymphocytes. These clinical findings indicate the essential requirement of CD4+ T-helper cells in mediating resistance during chronic Chagas' disease; however, the effector mechanisms that control the reactivation of chronic infection in vivo are not completely defined.

Acute Disease↗

PubMed1995

Effect of treatment with an ivermectin sustained-release bolus on productivity of stocker beef calves.

Three groups of 30 crossbred beef steers, 8-10 months of age and ranging in weight from 158 to 320 kg, were used to compare effects of treatment with an ivermectin sustained-release bolus or two ivermectin injectable treatments on parasite control and productivity in relation to untreated controls during a 168 day winter-spring grazing period. Each group of 30 consisted of five cattle on each of six separate 1.6 ha pastures. Treatments on Day 0 (12 December) were: Group 1: untreated controls; Group 2: ivermectin injectable at 200 micrograms kg-1 bodyweight, s.c., on Day 0 and Day 56; Group 3: ivermectin sustained-release bolus to deliver ivermectin at 12 mg day-1 over approximately 135 days. All cattle were weighed at 28 day intervals and fecal samples were collected for egg per gram counts (EPG). Geometric mean EPG for Group 3 remained consistently less than 1.0 after Day 0 and were highest (2.4) on Day 168. All group EPG were significantly different (P < 0.01) by Day 56, and EPG of Group 2 had increased to 10.5 following initial treatment and to 42.8 on Day 112. With the exception of a low mean EPG of 6.8 for Group 1 on Day 112, EPG of the group were consistently highest (range 24.9-36.0) to the end of the experiment. Ostertagia ostertagi was predominant, along with smaller proportions of Haemonchus placei and Cooperia spp. Throughout the experiment Group 3 had highest liveweights and gains that were most often different from those of Group 1 at P < 0.01 or greater.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2004

Integrated pharmacological assessment of flubendazole potential for use in sheep: disposition kinetics, liver metabolism and parasite diffusion ability.

Flubendazole (FLBZ) is a broad spectrum benzimidazole methylcarbamate anthelmintic widely used in poultry and swine. However, there is no information available on the pharmacological behaviour of FLBZ in ruminants. The work reported here was addressed to evaluate the potential of FLBZ for use in sheep. The integrated assessment included evaluation of FLBZ and metabolites plasma disposition kinetics, liver metabolism and ex vivo ability to diffuse into the cestode parasite Moniezia benedeni. In a cross-over kinetic study, six healthy Corriedale sheep were treated with FLBZ by intravenous (i.v.) (4% solution) and intraruminal (i.r.) (4% suspension) administrations at the same dosage (5 mg/kg) with a 21-day washout period between treatments. Blood samples were collected between 0 and 72 h post-treatments. Sheep liver microsomes were incubated with 40 microm FLBZ and specimens of the cestode parasite M. benedeni, collected from untreated animals, were incubated (5-120 min) with FLBZ and its reduced (R-FLBZ) metabolite (5 microm). Samples of plasma, microsomal incubations and parasite material were prepared and analyzed by high-performance liquid chromatography to measure FLBZ and its metabolites. FLBZ parent drug showed a fast disposition being detected in the bloodstream up to 36 h after its i.v. administration. Both R-FLBZ and hydrolyzed FLBZ (H-FLBZ) metabolites were recovered in plasma as early as 5 min after the i.v. treatment in sheep. The plasma AUC ratios for R-FLBZ and FLBZ (AUC(R-FLBZ)/AUC(FLBZ)) were 4.07 i.v. and 5.55 i.r., respectively. R-FLBZ achieved a significantly higher (P < 0.01) C(max) value (0.14 microg/mL at 17.3 h post-treatment) than that observed for the parent drug FLBZ (0.04 microg/mL at 14.4 h post-treatment). Low plasma concentrations of FLBZ parent drug were measured between 6 and 48 h, and only trace concentrations of H-FLBZ were detected during a short period of time after the i.r. treatment. Consistently, sheep liver microsomes metabolized FLBZ into its reduced metabolite at a rate of 9.46 +/- 2.72 nmol/mg/h. Both FLBZ and R-FLBZ demonstrated a similar ability to quickly diffuse through the tegument of the cestode parasite. The data on FLBZ pharmacological behaviour presented here contribute to evaluate its potential to be developed as an anthelmintic for broad spectrum parasite control in ruminants.

Animals↗

PubMed2003

The pathophysiology of falciparum malaria.

Falciparum malaria is a complex disease with no simple explanation, affecting organs where the parasite is rare as well as those organs where it is more common. We continue to argue that it can best be understood in terms of excessive stimulation of normally useful pathways mediated by inflammatory cytokines, the prototype being tumor necrosis factor (TNF). These pathways involve downstream mediators, such as nitric oxide (NO) that the host normally uses to control parasites, but which, when uncontrolled, have bioenergetic failure of patient tissues as their predictable end point. Falciparum malaria is no different from many other infectious diseases that are clinically confused with it. The sequestration of parasitized red blood cells, prominent in some tissues but absent in others with equal functional loss, exacerbates, but does not change, these overriding principles. Recent opportunities to stain a wide range of tissues from African pediatric cases of falciparum malaria and sepsis for the inducible NO synthase (iNOS) and migration inhibitory factor (MIF) have strengthened these arguments considerably. The recent demonstration of bioenergetic failure in tissue removed from sepsis patients being able to predict a fatal outcome fulfils a prediction of these principles, and it is plausible that this will be demonstrable in severe falciparum malaria. Understanding the disease caused by falciparum malaria at a molecular level requires an appreciation of the universality of poly(ADP-ribose) polymerase-1 (PARP-1) and Na(+)/K(+)-ATPase and the protean effects of activation by inflammation of the former that include inactivation of the latter.

Africa↗

PubMed1991

Evidence for the segregation of a major gene in human susceptibility/resistance to infection by Schistosoma mansoni.

Severe clinical disease caused by the major human parasite Schistosoma mansoni is the consequence of high and prolonged infections. Epidemiological studies indicate that, for individuals having frequent contacts with cercaria-infested waters, both infection intensities and reinfection after treatment depend, in large part, on their intrinsic susceptibility/resistance to infection, suggesting the role of genetic factors in human resistance to S. mansoni. To investigate whether a major gene controls human susceptibility/resistance to infection by S. mansoni, segregation analysis of infection intensities, adjusted for the factors relevant in schistosomiasis (water contact, age, sex), was performed on 20 Brazilian pedigrees (269 individuals), using both the unified mixed model and the regressive model of analysis. The results are consistent with the hypothesis that there is a codominant major gene controlling human susceptibility/resistance to infection by S. mansoni. Parameter estimates indicate a frequency of .20-.25 for the deleterious allele; thus, about 5% of the population is predisposed to high infections, 60% is resistant, and 35% has an intermediate, although fairly good, level of resistance. These findings provide a genetic basis for earlier observations on the lower resistance and the predisposition to reinfection of certain individuals. In addition to the detection of a major gene effect, the data suggest that immunity to S. mansoni develops progressively during childhood to reach a maximum around the age of puberty. The implications of these results for the strategy to be used in endemic areas to reduce morbidity and to control parasite transmission are discussed.

Age Factors↗

PubMed2002

A cathepsin L protease essential for Caenorhabditis elegans embryogenesis is functionally conserved in parasitic nematodes.

Proteolytic enzymes are involved in processes important to development and survival of many organisms. Parasite proteases are considered potential targets of parasite control yet, for most, their precise physiological functions are unknown. Validation of potential targets requires analysis of function. We have recently identified a cathepsin L (CPL) cysteine protease, Ce-CPL-1, which is essential for embryonic development of the free-living nematode Caenorhabditis elegans. We now show that CPL genes closely related to Ce-cpl-1 are expressed in the animal parasitic nematodes Haemonchus contortus, Dictyocaulus viviparus, Teladorsagia circumcincta, Ancylostoma caninum and Ascaris suum, as well as in plant parasitic nematodes. The similarities in gene structure and encoded amino acid sequence indicate that the parasite and C. elegans CPLs are homologous enzymes. We demonstrate functional compensation of the loss of C. elegans cpl-1 by transgenic expression of the H. contortus cpl-1 gene, rescuing the embryonic lethality. These genes may therefore be orthologues, sharing the same function in both species. Targeting of this enzyme has potential in inhibiting development and transmission of parasitic nematodes. In addition, the role of CPL is important to our understanding of nematode development.

Amino Acid Sequence↗

PubMed2002

Relatively rapid loss of lampricide residues from fillet tissue of fish after routine treatment.

The selective sea lamprey (Petromyzon marinus) larvicide 3-trifluoromethyl-4-nitrophenol (TFM) is currently used to control parasitic sea lampreys in tributaries to the Great Lakes basin. The concentration and persistence of TFM and its major metabolite, TFM glucuronide (TFM-glu), was determined in fillet tissue of fish after a typical stream application. Rainbow trout (Oncorhynchus mykiss) and channel catfish (Ictalurus punctatus) were exposed to a nominal concentration of 12.6 nmol/mL TFM for about 12 h during a sea lamprey control treatment of the Ford River in Michigan. Concentrations of TFM and TFM-glu were greatest in the fillet tissues during the exposure period, with greater residues in channel catfish (wet wt; mean, 6.95 nmol/g TFM; mean, 2.40 nmol/g TFM-glu) than in rainbow trout (wet wt; mean, 1.45 nmol/g TFM; mean, 0.93 nmol/g TFM-glu). After the exposure period, residues in both species decreased by 90-99% within 6-12 h and were less than the quantitation limit (<0.03 nmol/g) within 36 h.

Animals↗

PubMed1998

Mechanism of parasitism-induced elevation of haemolymph growth-blocking peptide levels in host insect larvae (Pseudaletia separata).

Growth-blocking peptide (GBP) has been purified for the first time from the haemolymph of the host armyworm Pseudaletia separata whose growth is inhibited and shows developmental arrest in the last larval instar stage when parasitized by the parasitoid wasp Cotesia kariyai. GBP naturally occurs in the haemolymph of lepidopteran larvae but its concentration is very low during the last larval instar in comparison with that in the penultimate larval instar. However, by 24h after parasitization or polydnavirus (PdV)-infection on day 0 of the last larval instar, a four-fold increase in GBP level, compared with synchronous non-parasitized control larvae, is observed. Although Northern blot analysis indicates that GBP mRNA is transcribed in brain-nerve cord and fat body, plasma GBP is likely to be secreted mainly from fat body because the GBP mRNA level is approximately 100-fold higher in fat body than that in brain-nerve cord. RT-PCR analysis demonstrates the constant expression of GBP mRNA in both parasitized (or PdV-infected) and non-parasitized larval fat body, which suggests that parasitism does not influence transcriptional level, but might influence post-transcriptional level to elevate plasma GBP concentration. This interpretation was supported by estimating GBP precursor levels in fat body of PdV-infected and non-infected larvae. Virus infection appears to elevate the GBP precursor levels in fat body to about six times greater than that in non-infected last instar larvae by 6h after PdV-injection. The GBP processing enzyme activity that occurs in Golgi body-rich extract of the fat body is increased by about 90% after parasitization or PdV-injection.

Journal Article↗

PubMed1998

Recombinant Mycobacterium bovis bacillus Calmette-Guérin secreting merozoite surface protein 1 (MSP1) induces protection against rodent malaria parasite infection depending on MSP1-stimulated interferon gamma and parasite-specific antibodies.

The merozoite surface protein 1 (MSP1) has emerged as a leading malaria vaccine candidate at the erythrocytic stage. Recombinant bacillus Calmette-Guérin (rBCG), which expressed a COOH-terminal 15-kD fragment of MSP1 of Plasmodium yoelii (MSP1-15) as a fusion protein with a secretory protein of Mycobacterium kansasii, was constructed. Immunization of mice with this rBCG induced a higher degree of protection against blood-stage parasite infection than with recombinant MSP1-15 in the RIBI adjuvant (RIBI ImmunoChem Research, Inc., Hamilton, MT) or incomplete Freund's adjuvant systems. We studied the mechanism of protection induced by MSP1-15, and found that interferon (IFN)-gamma had a major role in protection in all adjuvant systems we examined. Mice that produced low amounts of MSP1-15 stimulated IFN-gamma and could not control parasite infection. The antibody against MSP1-15 did not play a major role in protection in this system. After parasite infection, immunoglobulin G2a antibodies, which had been produced by IFN-gamma stimulation, were induced and subsequently played an important role in eradicating parasites. Thus, both cellular and humoral immune responses were essential for protection from malaria disease. These data revealed that BCG is a powerful adjuvant to induce such a protective immune response against malaria parasites.

Adjuvants, Immunologic↗

PubMed2001

Mice lacking the chemokine receptor CCR1 show increased susceptibility to Toxoplasma gondii infection.

Chemokines are critical for the recruitment of effector immune cells to sites of infection. Mice lacking the chemokine receptor CCR1 have defects in neutrophil trafficking and proliferation. In the present study, we tested the susceptibility of CCR1 knockout mice to infection with the obligate intracellular protozoan parasite Toxoplasma gondii. In comparison with parental wild-type mice, CCR1(-/-) mice exhibited dramatically increased mortality to T. gondii in association with an increased tissue parasite load. No differences were observed in Ag-specific T cell proliferation or in cytokine responses between mutant and wild-type mice. However, the influx of PMNs to the peripheral blood and to the liver were reduced in CCR1(-/-) mice during early infection. Our results suggest that CCR1-dependent migration of neutrophils to the blood and tissues may have a significant impact in controlling parasite replication.

Animals↗

PubMed2004

The point prevalence of gastro-intestinal parasites in calves, sheep and goats in Magadi division, south-western Kenya.

Helminths cause great economic loss in livestock in Africa, and can be categorized as either direct or indirect losses. Arid and semi-arid lands (ASAL) in Kenya comprise 71% of total land area and harbour the largest population of cattle, sheep and goats. However, little information on the distribution and impact of gastro-intestinal (GIT) parasitism in these animals is available. This survey was conducted to establish the prevalence of GIT parasites infecting calves, sheep and goats and their relative importance in Magadi division, which is semi-arid. Faecal samples were obtained directly from the rectum of 109 calves, 133 goats and 20 sheep and submitted to the laboratory for faecal worm egg counts, and coccidial oocysts examination using a modified McMaster method. The significance of differences in mean egg count per gram (epg) between animal species and herds (farms) were assessed using analysis of variance. The overall prevalence of nematodes in the calves, sheep and goats was 69.2%, 80% and 82%, respectively. About 10% of sheep and goats had epgs higher than 1 000, the remainder having light to moderate infections. The overall prevalence of coccidial oocysts in calves, sheep and goats was 30%, 44% and 45%, respectively. Poor productivity in ASAL areas, where nutrition is often poor, is likely to be pronounced in the presence of parasite infections. These findings indicate that viable internal parasite control should be implemented in the study area in order to increase the productivity of the livestock there.

Analysis of Variance↗

PubMed2005

Adaptive significance of avian beak morphology for ectoparasite control.

The beaks of Darwin's finches and other birds are among the best known examples of adaptive evolution. Beak morphology is usually interpreted in relation to its critical role in feeding. However, the beak also plays an important role in preening, which is the first line of defence against harmful ectoparasites such as feather lice, fleas, bugs, flies, ticks and feather mites. Here, we show a feature of the beak specifically adapted for ectoparasite control. Experimental trimming of the tiny (1-2 mm) maxillary overhang of rock pigeons (Columba livia) had no effect on feeding efficiency, yet triggered a dramatic increase in feather lice and the feather damage they cause. The overhang functions by generating a shearing force against the tip of the lower mandible, which moves forward remarkably quickly during preening, at up to 31 timesper second. This force damages parasite exoskeletons, significantly enhancing the efficiency of preening for parasite control. Overhangs longer than the natural mean of 1.6mm break significantly more often than short overhangs. Hence, stabilizing selection will favour overhangs of intermediate length. The adaptive radiation of beak morphology should be re-assessed with both feeding and preening in mind.

Adaptation, Biological↗

PubMed1999

Parasitization of Lacanobia oleracea (Lepidoptera: Noctuidae) by the ectoparasitc wasp, Eulophus pennicornis. Effects of parasitization, venom and starvation on host haemocytes.

In contrast to the situation with endoparasitic wasps, little is known about the effects of ectoparasitoids and their secretions on the haemocytes of their insect hosts. To address this deficit, a study has been made of the ectoparasitic wasp, Eulophus pennicornis, and it's host, the tomato moth, Lacanobia oleracea. Using light microscopy, it was determined that L. oleracea has five main haemocyte types, namely, plasmatocytes, granular cells, spherule cells, oenocytoids and pro-haemocytes, representing 56%, 30%, 10%, 2% and 2% of the population, respectively. Parasitization by E. pennicornis, resulted in an increase in the number of circulating haemocytes up to day three, followed by a decrease towards day eight; the latter being associated with changes to the morphology and viability of the cells. For example, on day five after parasitization, plasmatocytes and granular cells had become more rounded and put out pseudopods less readily compared with those from non-parasitized controls, whilst from day seven onwards there was a significant decrease in haemocyte viability and by day nine, extensive haemocyte damage and disintegration was evident. These changes were not observed when larvae were injected with E. pennicornis venom, or when haemocytes were exposed directly to venom in vitro, neither did they occur in starved larvae. Thus, although the observed effects on L. oleracea haemocytes are definitely associated with parasitization they are not due to wasp venom components, nor are they a non-specific effect resulting from nutritional deprivation. The possibility that the feeding wasp larvae produce factors which perturb host haemocytes in order to help condition the host to ensure that successful parasitization occurs, is discussed.

Journal Article↗