Poor outcome and high prevalence of invasive fungal infections in patients with adult T-cell leukemia/lymphoma exposed to zidovudine and interferon alfa.

Patients treated for adult T-Cell leukemia/lymphoma (ATL) have a poor prognosis and are prone to infectious complications which are poorly described. As the French reference center for ATL, we retrospectively analyzed 47 consecutive ATL (acute, n = 23; lymphoma, n = 14; chronic, n = 8; smoldering, n = 2) patients between 2006 and 2016 (median age 51 years, 96% Afro-Caribbean origin). The 3-year overall survival (OS) was 15.8%, 11.3%, and 85.7% for acute, lymphoma, and indolent (chronic and smoldering) forms respectively. Among aggressive subtypes, 20 patients received, as frontline therapy, high dose of zidovudine and interferon alfa (AZT-IFN⍺) resulting in an overall response rate (ORR) of 39% (complete response [CR] 33%) and 17 chemotherapy resulting of an ORR of 59% (CR 50%). Ninety-five infections occurred in 38 patients, most of whom had an acute subtype (n = 73/95; 77%). During their follow-up, patients receiving frontline chemotherapy or frontline AZT-IFNα developed infections in 74% (n = 14/19) and 89% (n = 24/27) of the cases respectively. Sixty-four (67%) of infections were microbiologically documented. Among them, invasive fungal infections (IFI, n = 11) included 2 Pneumocystis jirovecii pneumonia, 5 invasive aspergillosis, and 4 yeast fungemia. IFI exclusively occurred in patients with acute subtype mostly exposed to AZT-IFNα (n = 10/11) and experiencing prolonged (> 10 days) grade 4 neutropenia. Patients with aggressive subtype experiencing IFI had a lower OS than those who did not (median OS 5.4 months versus 18.4 months, p = 0.0048). ATL patients have a poor prognosis even in the modern era. Moreover, the high rate of infections impacts their management especially those exposed to AZT-IFNα.

Strongyloidiasis screening in migrants living in Spain: systematic review and meta-analysis.

OBJECTIVES: To provide information regarding the prevalence of strongyloidiasis among migrants coming from Strongyloides stercoralis-endemic areas who reside in Spain. METHODS: Systematic review of the literature and meta-analysis of studies showing prevalence of S. stercoralis infection among migrants from Latin America, Africa, Eastern Europe, Asia and Oceania who reside in Spain. We included articles published until 30 April 2019 without language restriction. The keywords used for the search included 'Strongyloides stercoralis', 'strongyloidiasis', 'Spain', 'screening' and 'migrants'. RESULTS: Twenty-four studies were included in the review and meta-analysis, comprising 12 386 screened people. Eleven studies (7020 patients) evaluated the presence of S. stercoralis infection only through investigation of larvae in faeces, showing an overall prevalence of 1% (95%CI 1-1%). Thirteen studies (5366 patients) used a serological test, showing an overall prevalence of 14% (95%CI 11-17%). Strongyloidiasis seroprevalence was 20% (95%CI 15-24%) among migrants from sub-Saharan Africa, 14% (95%CI 10-18%) among those from Latin America and 8% (95%CI 5-11%) among migrants from North Africa. CONCLUSIONS: Migrants coming from strongyloidiasis-endemic areas living in Spain had a high S. stercoralis infection prevalence, particularly those from sub-Saharan Africa and Latin America. This population should be screened using serology as the most sensitive test for S. stercoralis infection. This could be easily implemented at primary care level.

OBJECTIFS: Fournir des informations sur la prévalence de la strongyloïdose parmi les migrants résidant en Espagne et provenant de zones endémiques pour Strongyloides stercoralis. MÉTHODES: Revue systématique de la littérature et méta-analyse des études montrant la prévalence de l'infection à S. stercoralis parmi les migrants d'Amérique latine, d'Afrique, d'Europe de l'Est, d'Asie et d'Océanie qui résident en Espagne. Nous avons inclus des articles publiés jusqu'au 30 avril e 2019 sans restriction de langue. Les mots clés utilisés pour la recherche comprenaient "Strongyloides stercoralis", "strongyloïdose", "Espagne", "dépistage" et "migrants". RÉSULTATS: Vingt-quatre études ont été incluses dans la revue et la méta-analyse, comprenant 12.386 personnes dépistées. Onze études (7.020 patients) ont évalué la présence d'une infection à S. stercoralis uniquement en examinant les larves dans les selles, montrant une prévalence globale de 1% (IC95%: 1-1%). Treize études (5.366 patients) ont utilisé un test sérologique, montrant une prévalence globale de 14% (IC95%: 11-17%). La séroprévalence de la strongyloïdose était de 20% (IC95%: 15-24%) chez les migrants d'Afrique subsaharienne, 14% (IC95%: 10-18%) chez ceux d'Amérique latine et 8% (IC95%: 5-11%) chez ceux d'Afrique du Nord. CONCLUSIONS: Les migrants en provenance de zones d'endémie pour la strongyloïdose vivant en Espagne avaient une prévalence élevée d'infection à S. stercoralis, en particulier ceux d'Afrique subsaharienne et d'Amérique latine. Cette population devrait être dépistée en utilisant la sérologie comme le test le plus sensible pour l' infection à S. stercoralis. Cela pourrait être facilement mis en œuvre au niveau des soins primaires.

Organ donor screening practices for Strongyloides stercoralis infection among US organ procurement organizations.

BACKGROUND: Targeted donor screening for strongyloidiasis performed at the time of organ procurement can prevent this life-threatening donor-derived infection. METHOD: The Association of Organ Procurement Organizations surveyed members to determine the number of US organ procurement organizations (OPOs) performing donor screening for Strongyloides infection and their screening practices. RESULTS: All 58 OPOs responded to the survey. Only 6 (10%) currently screen donors for strongyloidiasis; most OPOs started 6-36 months before the survey and one started 6 years prior. All used risk-based criteria to determine which donors to screen, though the criteria varied among OPOs. A median of 56 donors have been screened at each OPO since initiating their screening programs, with a median of 2 infected donors (range 0-13) identified. Overall, 53 organs have been transplanted from 22 infected donors, including hearts, lungs, kidneys, and livers. Of 52 OPOs not currently screening, 20 had considered screening and one plans to start screening in the near future. Of those considering risk-based screening, most had not decided on the criteria. Uncertainty about the benefits of and guidelines for screening and misconceptions about the interpretation of test results were concerns shared by non-screening OPOs. CONCLUSION: Continued education and advocacy on the importance of targeted donor screening are needed.

Impact of the health education and preventive equipment package (HEPEP) on prevention of Strongyloides stercoralis infection among rural communities in Northeast Thailand: a cluster randomized controlled trial.

BACKGROUND: Strongyloidiasis is prevalent in northeast Thailand. This study aimed to evaluate the impact of the Health Education and Preventive Equipment Package (HEPEP), a package we developed to improve awareness and aid in the prevention of Strongyloides stercoralis infection among rural communities in northeast Thailand. METHODS: This was an intervention trial conducted in 12 villages (six interventions and six controls) in rural areas of northeast Thailand from March 2016 to September 2017. Single stool sample was collected from each participant and examined using agar plate culture (APC) technique. Each participant was interviewed using a pre-tested questionnaire, treated with single dose of ivermectin (200 µg/Kg), and allocated to either the intervention or control group. Members of the intervention group were given "Practices to Prevent Strongyloidiasis" poster and vinyl boards containing information aimed at raising awareness of S. stercoralis and strongyloidiasis. In addition, they were given a poster lecture regarding the lifecycle of S. stercoralis before being treated with ivermectin. Aside from that, they were also given a protective equipment package. Monthly refresher courses were provided by village health volunteers (VHVs) regarding the health information they had received and proper equipment usage. The control group, on the other hand, was only provided with a five-minute lecture regarding strongyloidiasis. Assessment of new infection was conducted 3 months later in 327 and 318 participants in the intervention group and control group, respectively. RESULTS: The HEPEP had 41% greater efficacy in preventing S. stercoralis infection in the intervention group than the measures taken in the control group (adjusted Odds Ratio (aOR) = 0.59; 95%CI: 0.41 to 0.85, P-value = 0.005). The intervention group also scored significantly higher on all aspects of a test of S. stercoralis knowledge compared with the control group (mean difference (mean dif.) = 2.89, P-value = < 0.05). CONCLUSIONS: The HEPEP was the first model that has been found to be effective in controlling of S. stercoralis in rural communities in the northeast Thailand. The results should encourage policy makers and public health personnel to improve control programs, as well as health promotion, with regard to parasites. TRIAL REGISTRATION: Thai Clinical Trials Registry (TCTR), Medical Research Foundation of Thailand, Medical Research Network of the Consortium of Thai Medical Schools: MedResNet (Thailand) (identification number: TCTR20180404002 ) Registered 4 April 2018 (retrospectively registered).

Status and Risk Factors of Strongyloides stercoralis Infection in Rural Communities of Xayaburi Province, Lao PDR.

The present study was performed to reveal the current status and risk factors of Strongyloides stercoralis infections in the villages of Kenethao district, Xayaburi Province, Lao PDR. Fecal specimens were collected and examined for S. stercoralis using Koga-agar plate culture technique. Among 516 individuals, the prevalence of S. stercoralis and hookworm infection was 44.2% and 17.1%, respectively. Co-infection was detected in 13.2% of the cases. The prevalence did not significantly differ between males and females (P=0.193). However, the prevalence of S. stercoralis infection increased significantly with age (P=0.041). Of the risk factors examined, both performing farming activities (P=0.001) and walking barefoot when going outside of the house (P=0.003) showed significant correlations with S. stercoralis infections. Our results suggest that S. stercoralis is highly endemic in this area. The National Helminth Control Program of Lao PDR should take actions to control S. stercoralis infection. In addition, provision of health education about the benefits of wearing shoes would be important for reducing infection in the study area. Moreover, the application of high-sensitivity diagnostic approaches is needed to obtain the true impact of S. stercoralis infections in all rural communities in order to provide surveillance activities in Lao PDR.

[Strongyloidiasis: who is at risk of severe infection and how to prevent it?]. / Strongyloïdose: qui est à risque d'infection sévère et comment la prévenir?

Strongyloides stercoralis hyperinfection syndrome, which carries a high mortality (60%), occurs usually after immunosuppressive therapy. Cellular immunosuppression allows the parasite to reactivate and stimulate its cycle of auto-infection. It is therefore important to prevent this syndrome by screening at risk patients at risk for chronic strongyloidiasis before starting immunosuppressive treatment and especially before treatment with corticosteroids, even that of short duration. Ivermectine is the treatment of choice.

Generation of IgG antibodies against Strongyloides stercoralis in mice via immunization with recombinant antigens A133 and Ss-IR.

Strongyloidiasis, caused by the nematode Strongyloides stercoralis, remains a threat to global public health, and a vaccine would be useful to control the disease, especially in developing countries. This study aimed to evaluate the efficacy of recombinant proteins, A133 and Ss-IR, as potential vaccine candidates against strongyloidiasis by investigating the humoral and cellular immune responses in immunized mice. Respective antigens were adjuvanted with Complete Freund's Adjuvant (prime) and Incomplete Freund's Adjuvant (boost) and administered intraperitoneally (prime) and subcutaneously (boost) to female BALB/c mice. For antigen-only doses, only antigens were injected without adjuvants. Altogether, 1 prime dose, 4 booster doses, and 2 antigen-only doses were administered successively. ELISAs were conducted to assess the antibody responses, along with flow cytometry and cytokine ELISA to elucidate the cellular immune responses. Results showed that A133 and Ss-IR induced the production of IgG1 and IgG2a, with A133 generating more robust IgG2a responses than Ss-IR. Flow cytometry findings indicated that effector CD8+T-cells and memory B-cells activity were upregulated significantly for A133 only, whereas cytokine ELISA demonstrated that a Th1/Th2/Th17 mixed cell responses were triggered upon vaccination with either antigen. This preliminary study illustrated the good potential of recombinant A133 and Ss-IR as vaccine candidates against S. stercoralis. It provided information on the probable immune mechanism involved in host defence and the elicitation of protection against S. stercoralis.

Progress towards the implementation of control programmes for strongyloidiasis in endemic areas: estimation of number of adults in need of ivermectin for strongyloidiasis.

The World Health Organization has started a process to issue guidelines for the control of strongyloidiasis. The guidelines might recommend to implement preventive chemotherapy (PC) at community level (i.e. to all individuals above 5 years of age), over a defined prevalence threshold. We previously estimated the number of school-age children (SAC) who would need PC. Here we estimate the number of people above 15 years of age who might be included in PC for strongyloidiasis. Based on previous Strongyloides prevalence estimates and on countries' age distribution, we retrieved the number of adults in need of PC. We then subtracted the number of people already involved in ivermectin mass distribution for the elimination of onchocerciasis and lymphatic filariasis and people living in countries where Loa loa is endemic. The number of adults to be involved in PC was estimated at 905.4 (95% confidence interval (CI): 520.6-1177.2), 660.2 (95% CI: 512.7-1214.9), and 512.1 (95% CI: 276-719.4) million people, when the strongyloidiasis prevalence threshold for implementing PC was set to 10%, 15% and 20%, respectively. Estimates at country level are also provided.These estimates might help endemic countries wishing to implement PC for strongyloidiasis to allocate resources to include adults in addition to SAC in control programmes. This article is part of the Theo Murphy meeting issue 'Strongyloides: omics to worm-free populations'.

IgG and IgE collaboratively accelerate expulsion of Strongyloides venezuelensis in a primary infection.

The host deploys a subset of immune responses to expel helminths, which differs depending on the nature of the helminth. Strongyloides venezuelensis, a counterpart of the human pathogen S. stercoralis, naturally infects rodents and has been used as an experimental model. Here we show that induction of immunoglobulin G (IgG) and IgE is a prerequisite for rapid expulsion of S. venezuelensis during a primary infection. Activation-induced cytidine deaminase-deficient (AID(-/-)) mice, which lack the ability to switch IgM to other isotypes, normally developed T-helper 2 (Th2) cells and intestinal mastocytosis after infection with S. venezuelensis. Although AID(-/-) mice expelled Nippostrongylus brasiliensis normally, they required a much longer period to expel S. venezuelensis than wild-type (WT) mice. Adoptive transfers of immune sera from S. venezuelensis-infected but not N. brasiliensis-infected mice restored the ability of AID(-/-) mice to promptly expel S. venezuelensis. Immune serum-derived IgG and IgE induced worm expulsion via Fc γ receptor III (FcγRIII) and Fc ε receptor I (FcεRI), respectively, and a mixture of IgG and IgE showed collaborative effects. Whereas FcγRIII(-/-) mice or FcεRIα(-/-) mice normally could expel S. venezuelensis, FcγRIII(-/-) mice, when their IgE was neutralized by anti-IgE, or FcεRIα(-/-) mice, when their IgG binding to FcγRIII was blocked by anti-FcγRIII, showed a markedly reduced ability to expel S. venezuelensis. These data reveal that IgG and IgE play redundant roles but act in concert to accelerate S. venezuelensis expulsion. Mast cell-deficient mice, even those equipped with immune serum-derived IgG or IgE, failed to expel S. venezuelensis promptly, suggesting that mast cells are cellular targets of IgG and IgE.

Prevalence of Strongyloides in Southeast Asia: a systematic review and meta-analysis with implications for public health and sustainable control strategies.

BACKGROUND: Strongyloidiasis, caused by the nematodes Strongyloides stercoralis and Strongyloides fuelleborni, is estimated to affect over 600 million individuals worldwide. The disease is endemic in Southeast Asia, where a warm-humid climate and socio-economic conditions maintain the parasite's life cycle and transmission. However, the current diagnostic methods may not be sufficiently sensitive, suggesting that the true prevalence of strongyloidiasis could be seriously underestimated in this. This study aims to determine the prevalence of strongyloidiasis in Southeast Asia through a systematic review and meta-analysis and to discuss the implications of the estimated prevalence on diagnostic approaches and control strategies. METHODS: Following PRISMA guidelines, we conducted a systematic literature search in PubMed and Google Scholar databases to identify studies reporting Strongyloides prevalence data in the 11 Southeast Asian countries up to December 2022. A random effects model was employed to estimate the pooled prevalence of S. stercoralis at both regional and country levels. RESULTS: Out of 3722 articles identified, 224 met our inclusion criteria. For S. stercoralis specifically, we found 187 articles, of which 52.4% were from Thailand. All Southeast Asian countries, except Brunei, had at least one study on Strongyloides prevalence. The estimated pooled prevalence of S. stercoralis regionally was 12.7% (95% CI 10.70-14.80%), ranging from 0.4 to 24.9% at the country level. Cambodia had the highest pooled prevalence (24.9%, 95% CI 15.65-35.38%), followed by Lao PDR (16.5%, 95% CI 9.50-24.95%). Moreover, we obtained a pooled prevalence of 10% (95% CI 7.06-13.52%) in a group comprising immigrants, workers, and veterans from Southeast Asian countries. S. stercoralis infects various host types, including nonhuman primates, domestic dogs and cats, rodents, and transport carriers such as cockroaches and vegetables. CONCLUSIONS: A high prevalence of strongyloidiasis in Southeast Asia was revealed, highlighting the importance of the region's ongoing research, surveillance, and control efforts. Factors contributing to the strongyloidiasis transmission include the role of animal hosts, the impact of global connectivity, and the significance of the co-endemicity of other Strongyloides species. Based on these findings, a multi-pronged One-Health approach is essential for sustainable intervention and control.

Impact of preventive chemotherapy on Strongyloides stercoralis: A systematic review and meta-analysis.

BACKGROUND: Strongyloides stercoralis is a neglected soil-transmitted helminth (STH) that leads to significant morbidity in endemic populations. Infection with this helminth has recently been recognised by the World Health Organization (WHO) as a major global health problem to be addressed with ivermectin preventive chemotherapy, and therefore, there is now, the need to develop guidelines for strongyloidiasis control that can be implemented by endemic countries. This study aimed to evaluate the impact of ivermectin preventive chemotherapy (PC) on S. stercoralis prevalence in endemic areas to generate evidence that can inform global health policy. METHODOLOGY/PRINCIPAL FINDINGS: This study was a systematic review and meta-analysis. We searched PubMed, EMBASE, Cochrane Central Register of Controlled Trials, and LILACS for literature published between 1990 and 2022 and reporting prevalence of S. stercoralis before and after PC with ivermectin, administered either at school or at community level. The search strategy identified 933 records, eight of which were included in the meta-analysis. Data extraction and quality assessment were carried out by two authors. Meta-analysis of studies based on fecal testing demonstrated a significant reduction of S. stercoralis prevalence after PC: prevalence Risk Ratio (RR) 0.18 (95% CI 0.14-0.23), I2 = 0. A similar trend was observed in studies that used serology for diagnosis: RR 0.35 (95% CI 0.26-0.48), I2 = 4.25%. A sensitivity analysis was carried out for fecal tests where low quality studies were removed, confirming a post-intervention reduction in prevalence. The impact of PC could not be evaluated at different time points or comparing annual vs biannual administration due to insufficient data. CONCLUSIONS/SIGNIFICANCE: Our findings demonstrate a significant decrease of S. stercoralis prevalence in areas where ivermectin PC has taken place, supporting the use of ivermectin PC in endemic areas.

Efficacy of Oral Ivermectin as Empirical Prophylaxis for Strongyloidiasis in Patients Treated with High-Dose Corticosteroids: A Retrospective Cohort Study.

People living in areas endemic for strongyloidiasis are at risk of latent Strongyloides stercoralis infection. Corticosteroid therapy is a well-established risk factor for life-threatening hyperinfection syndrome and disseminated disease owing to suppression of the immune system. There are limited data available on the efficacy and cost of providing oral ivermectin prophylaxis to all patients receiving high-dose corticosteroids for strongyloidiasis in endemic areas. We thus conducted this retrospective cohort study at Khon Kaen University's Srinagarind Hospital from 2015 to 2019. Inclusion criteria were as follows: age ≥ 18 years, having received ≥ 0.5 mg/kg/day of prednisolone or equivalent for at least 14 days, and hospitalization during the study period. A total of 250 patients were included in the study: 125 in the empirical prophylaxis group (prescribed ivermectin even if fecal examination results were negative or nonexistent) and the remaining patients in the definite therapy group (prescribed ivermectin only if S. stercoralis was detected by fecal examination). The prevalence of strongyloidiasis at enrollment estimated by fecal examination was 5.5%. Ivermectin was given to 125 patients (100%) in the prophylaxis group compared with 12 (9.6%) in the definite therapy group (P value < 0.001). During the 12-month follow-up period, S. stercoralis was detected in three patients, two in the prophylaxis group and one in the definite therapy group (P value = 1.000). No cases of hyperinfection syndrome or disseminated disease were found. The empirical prophylaxis strategy had a significantly higher cost than the definite therapy strategy (563 versus 254, P value < 0.001) and did not demonstrate superior efficacy in strongyloidiasis prevention.

Screening, prevention, and treatment for hyperinfection syndrome and disseminated infections caused by Strongyloides stercoralis.

PURPOSE OF REVIEW: This review discusses the latest approaches to the diagnosis and treatment of patients with strongyloidiasis, with an emphasis on infection in the immunocompromised host and the risk for disseminated strongyloidiasis. RECENT FINDINGS: The differences in acute, chronic, accelerated autoinfection, and disseminated disease in Strongyloides stercoralis infection are explored with particular emphasis on early diagnosis, treatment, and prevention. The goals of treatment are investigated for the different infection states. Predisposing risks for dissemination are delineated, and the roles played for newer diagnostics in the identification of at-risk individuals are detailed. SUMMARY: The use of newer diagnostic tests and broader screening of immunocompromised patients from Strongyloides-endemic areas is of paramount importance, particularly if prevention of life-threatening dissemination is the goal.

Characterization of genes with a putative key role in the parasitic lifestyle of the nematode Strongyloides ratti.

Parasitic nematodes are significant pathogens of humans and other animals. The molecular and genetic basis of animal parasitism is not yet fully understood. Strongyloides spp. are a genus of gastrointestinal nematodes of which species infect approximately 100­200 million people worldwide. S. ratti is a natural parasite of the rat, and a useful and amenable laboratory model. Previous EST and microarray analyses of the S. ratti life cycle have identified genes whose expression was specific, or biased, to the parasitic adult stage, suggesting that they may play a key role in parasitism in this species. Here we have further investigated the expression of these genes (by RT-PCR) throughout the S. ratti life-cycle. We produced recombinant proteins in vitro for a subset of these genes, which were used in Western blot analyses to investigate the distribution of the gene products among different stages of the S. ratti life cycle. We tested the efficacy of these recombinant proteins as anti-S. ratti vaccines. One of the proteins was detected in the excretory/secretory products of the parasitic stages.

Ivermectin and albendazole coadministration: opportunities for strongyloidiasis control.

In 2020, WHO recognised the importance of strongyloidiasis alongside soil-transmitted helminths (STH) in their 2021-30 roadmap, which aspires to target Strongyloides stercoralis with preventive chemotherapy by use of ivermectin. Combination treatment with both albendazole, the primary drug used to treat STH, and ivermectin, would improve the efficiency of mass drug administration targeting both STH and S stercoralis. In this Personal View, we discuss the challenges and opportunities towards the development of an efficient control programme for strongyloidiasis, particularly if it is to run concurrently with STH control. We argue the need to define the prevalence threshold to implement preventive chemotherapy for S stercoralis, the target populations and optimal dosing schedules, and discuss the added benefits of a fixed-dose coformulation of ivermectin and albendazole. Implementation of an efficient control programme will require improvements to current diagnostics, and validation of new diagnostics, to target and monitor S stercoralis infections, and consideration of the challenges of multispecies diagnostics for S stercoralis and STH control. Finally, the evolution of ivermectin resistance represents a credible risk to control S stercoralis; we argue that genome-wide approaches, together with improved genome resources, are needed to characterise and prevent the emergence of resistance. Overcoming these challenges will help to reduce strongyloidiasis burden and enhance the feasibility of controlling it worldwide.

Major basic protein from eosinophils and myeloperoxidase from neutrophils are required for protective immunity to Strongyloides stercoralis in mice.

Eosinophils and neutrophils contribute to larval killing during the primary immune response, and neutrophils are effector cells in the secondary response to Strongyloides stercoralis in mice. The objective of this study was to determine the molecular mechanisms used by eosinophils and neutrophils to control infections with S. stercoralis. Using mice deficient in the eosinophil granule products major basic protein (MBP) and eosinophil peroxidase (EPO), it was determined that eosinophils kill the larvae through an MBP-dependent mechanism in the primary immune response if other effector cells are absent. Infecting PHIL mice, which are eosinophil deficient, with S. stercoralis resulted in development of primary and secondary immune responses that were similar to those of wild-type mice, suggesting that eosinophils are not an absolute requirement for larval killing or development of secondary immunity. Treating PHIL mice with a neutrophil-depleting antibody resulted in a significant impairment in larval killing. Naïve and immunized mice with neutrophils deficient in myeloperoxidase (MPO) infected with S. stercoralis had significantly decreased larval killing. It was concluded that there is redundancy in the primary immune response, with eosinophils killing the larvae through an MBP-dependent mechanism and neutrophils killing the worms through an MPO-dependent mechanism. Eosinophils are not required for the development or function of secondary immunity, but MPO from neutrophils is required for protective secondary immunity.