Concomitant Parasitic Infections Research Articles

A comprehensive investigation of an outbreak of concomitant parasitic infections in backyard poultry

A comprehensive investigation of an outbreak of concomitant parasitic infections in backyard poultry

Schistosomiasis and Recurrent Arthritis: A Systematic Review of the Literature.

Schistosomiasis is an endemic parasitic infection found in many tropical countries and is highly prevalent in sub-Saharan Africa. It can follow different and atypical clinical patterns. In these unusual cases, diagnosis may be difficult, as symptoms are unspecific. Arthropathy can appear in parasitic infections, but making a connection between arthritis and parasitic aetiology is difficult. This review aims to summarise all cases that have reported schistosomiasis associated with arthropathy, and the different ways authors have diagnosed this disease. We present a systematic literature review of schistosomiasis associated with joint impairments, with a focus on the difficulty of differentiating between reactive arthritis and its parasitic presence in situ. Joint impairments mimicking polyarthropathy are not rare in parasitic infections. Diagnosis is difficult. On the one hand, some patients have arthritis with parasite eggs found in situ, particularly in synovial biopsy. These situations are less common and antiparasitic treatment is straightforward. On the other hand, arthritis can be associated with parasitic infections in the form of reactive arthritis due to an immunological reaction. In such cases, pathogenicity due to circulating immune complex should be suspected. Anti-inflammatory treatments such as corticosteroids or immunosuppressive therapies are ineffective in cases of schistosomal arthropathy. A joint fluid puncture appears to be necessary and parasitic examination as well as in situ immunological techniques appear to be important in order to confirm the diagnosis of schistosomal arthropathy. The frequency of articular schistosomiasis is probably underestimated and should be sought when patients have unexplained polyarthropathy, as it can be an alternative diagnosis when patients have concomitant parasitic infections. These situations are common, whereas the association between unexplained inflammatory arthritis and a concomitant parasitic infection is rarely made. Unspecific rheumatism can lead to probabilistic treatments with many side effects, and looking for a parasitic aetiology could lead to repeated antiparasitic treatments and may avoid other immunosuppressive or corticosteroid therapies. With increasing travel and global migration, physicians need to be more aware of nonspecific symptoms that may reveal an atypical presentation of a tropical disease that can be treated easily, thus avoiding inappropriate immunosuppressive treatments.

Effect of intestinal parasites infection on clinical features of patients infected with COVID-19 in Al-Diwaniyah governorate

The study included a survey of intestinal parasites of patients infected with the emerging coronavirus, COVID-19 in Al-Diwaniyah Governorate, from October 2021 to June 2022, aimed to study the effect of concomitant parasitic infections on the severity of infection with the emerging coronavirus (Covid-19), by examining 211 patients with severe acute respiratory syndrome (SARS-COVID-19), their infection was confirmed by Real time PCR method in the laboratories of Al-Diwaniyah Teaching Hospital. The results show that the severity of COVID-19 was determined based on clinical symptoms and co-parasitic infection, these symptoms are represented by a cough, fever, loss of taste and smell, shortness of breath, diarrhea, diastolic and systolic blood pressure, lack of oxygen, heart rate, and a high temperature of more than 37° C. The immunoglobulins showed that 7 and 8 cases positive for IgM & IgG were recorded, respectively, while 3 cases were negative for IgM and 4 cases were also negative for IgG, as for patients suffering from parasitic infection in addition to covid 19, 6 positive cases for both IgM & IgG and 4 negative cases for both IgM & IgG were recorded.

The burden of Vector-Borne and Soil-Transmitted Polyparasitism in a Nigerian Rural Community: A cross-sectional study

Background: Concomitant parasitic infections are common in the developing world, yet most studies focused on a single parasite in a narrow age group. This study investigated the extent of polyparasitism and co-infections in a rural community in Osun State, Nigeria. Methods: Two hundred and forty-seven consenting individuals consisting of 118 males and 129 females participated in this study. Faecal specimens, venous blood, and skin snips were collected from the participants. The Kato-Katz technique was used to screen the faecal samples for soil-transmitted helminth, while Giemsa-stained blood smears were used for Plasmodium falciparum detection. Skin snips microscopy and haematoxylin-stained blood smears were used to diagnose onchocerciasis and loiasis, respectively. Demographic information was collected from all the participants. Results: The prevalence of P. falciparum, hookworms and Ascaris lumbricoides were 55.9%, 19.4% and 26.3%, respectively. The overall prevalence of the filarial infections was 4.5% for Loa loa microfilaremia, 23.5% for Onchocerca volvulus microfilarial. Thirty-eight per cent of the population harboured at least two parasites concurrently. Females (52.2%) were generally more infected with all the helminths than males (48.8%), but the difference was not statistically significant (p=0.128). For onchocerciasis prevalence, males (29.7%) were more infected than females (17.8%), and the difference was statistically significant (p=0.035). Co-infection of malaria and loiasis was observed in 1.2% of the population (p=0.051), while 13% were co-infected with malaria and onchocerciasis (p=0.903). Co-infection of malaria and hookworm was observed in 10.5% of the population. The overall mean Packed Cell Volume (PCV) of the population was 40.03±5.84, and no significant difference (p=0.224) was observed between PCV and infection status. Also, no significant association (p=0.051) was observed between the age group and infection status. The intensity of the parasites was classified into 1-9, 10-99, 100-149, and 150 and above. Almost all the helminths except Ascaris lumbricoides had a low grade of helminths (1-9). The intensity was more pronounced in Ascaris lumbricoides than in other helminths. A. lumbricoides + P. falciparum co-infection had a higher geometric mean para-sites density (GMPD) value when compared with only P. falciparum infection. There was no significant difference in co-infection of P. falciparum + loa loa, P. falciparum + O .volvulus and P. falciparum + Hookworm with P. falciparum alone. Conclusion: This study confirmed that polyparasitism is still common in rural communities in the study area. The findings can be used to design and implement appropriate intervention strategies to alleviate morbidity and co-morbidity in rural communities.

A large case series of travel-related Mansonella perstans (vector-borne filarial nematode): a TropNet study in Europe.

Infection with Mansonella perstans is a neglected filariasis, widely distributed in sub-Saharan Africa, characterized by an elusive clinical picture; treatment for mansonellosis is not standardized. This retrospective study aimed to describe the clinical features, treatment schemes and evolution, of a large cohort of imported cases of M. perstans infection seen in four European centres for tropical diseases. Mansonella perstans infections, diagnosed by identification of blood microfilariae in migrants, expatriates and travellers, collected between 1994 and 2018, were retrospectively analysed. Data concerning demographics, clinical history and laboratory examinations at diagnosis and at follow-up time points were retrieved. A total of 392 patients were included in the study. Of the 281 patients for whom information on symptoms could be retrieved, 150 (53.4%) reported symptoms, abdominal pain and itching being the most frequent. Positive serology and eosinophilia were present in 84.4% and 66.1%, respectively, of those patients for whom these data were available. Concomitant parasitic infections were reported in 23.5% of patients. Treatment, administered to 325 patients (82.9%), was extremely heterogeneous between and within centres; the most commonly used regimen was mebendazole 100mg twice a day for 1 month. A total of 256 (65.3%) patients attended a first follow-up, median 3months (interquartile range 2-12) after the first visit; 83.1% of patients having received treatment based on mebendazole and/or doxycycline, targeting Wolbachia, became amicrofilaremic, 41.1-78.4% of whom within 12months from single treatment. Lack of specific symptoms, together with the inconstant positivity of parasitological and antibody-based assays in the infected population, makes the clinical suspicion and screening for mansonellosis particularly difficult. Prospective studies evaluating prevalence of infection in migrants from endemic areas, infection-specific morbidity, presence of Wolbachia endosymbionts in M. perstans populations from different geographical areas and efficacy of treatment regimens are absolutely needed to optimize the clinical management of infection.

Elevated Pediatric Chagas Disease Burden Complicated by Concomitant Intestinal Parasites and Malnutrition in El Salvador.

The eradication of the vector Rhodnius prolixus from Central America was heralded as a victory for controlling transmission of Trypanosoma cruzi, the parasite that causes Chagas disease. While public health officials believed this milestone achievement would effectively eliminate Chagas disease, case reports of acute vector transmission began amassing within a few years. This investigation employed a cross-sectional serosurvey of children either presenting with fever for clinical care or children living in homes with known triatomine presence in the state of Sonsonate, El Salvador. Over the 2018 calendar year, a 2.3% Chagas disease seroprevalence among children with hotspot clustering in Nahuizalco was identified. Positive serology was significantly associated with dogs in the home, older participant age, and a higher number of children in the home by multivariate regression. Concomitant intestinal parasitic infection was noted in a subset of studied children; 60% having at least one intestinal parasite and 15% having two or more concomitant infections. Concomitant parasitic infection was statistically associated with an overall higher parasitic load detected in stool by qPCR. Lastly, a four-fold higher burden of stunting was identified in the cohort compared to the national average, with four-fifths of mothers reporting severe food insecurity. This study highlights that polyparasitism is common, and a systems-based approach is warranted when treating Chagas disease seropositive children.

Lako rešivo kada se prepozna - prikaz slučaja - kutana larva migransa

Introduction: Cutaneous larva migrans (CLM) is a syndrome, defined by clinical appearance of slowly migrating cutaneous eruption caused by inoculation with animal hookworms larvae in the skin. Despite the typical clinical presentation, CLM is frequently misdiagnosed due to its rarity in temperate climate urban communities. Case Report: We report a case of a 42-year old female, admitted to an outpatient clinic with eruption of multiple intense pruritic, erythematous, exudative papules and oval plaques, located predominately on the back. The patient claimed that skin lesions started three weeks before the examination, during her vacation in Thailand, and at first, was taught to be caused by a contact with jelly fish. Lesions were treated unsuccessfully with oral antihistamines and various topical corticosteroids, which lead to more questions regarding the differential diagnosis. Dermoscopical and histopathological findings were indicative of parasitic infection, most likely CLM. A three-day course of oral albendazole, 400 mg daily, resulted in complete cure of the disease. Conclusions: Careful clinical examination and detailed history taken from the patient are fundamentals for creating a set of differential diagnoses, that can be further clarified by the use of laboratory findings, imaging methods (including dermoscopy) and biopsy with histopathology. Although CLM has a benign self-limiting course, intense itch may substantially impact the quality of life, and possible visceral involvement or concomitant parasitic infection may lead to serious health deterioration in unrecognized cases.

Unexpected concomitant parasitic infection and tuberculosis in the evaluation of hypertrophic pachymeningitis with 18F-FDG PET/CT: [[es]]Infección parasitaria y tuberculosis como hallazgos inesperados en laevaluación de paquimeningitis hipertrófica mediante 18FDG-PET/TC

Unexpected concomitant parasitic infection and tuberculosis in the evaluation of hypertrophic pachymeningitis with 18F-FDG PET/CT: [[es]]Infección parasitaria y tuberculosis como hallazgos inesperados en laevaluación de paquimeningitis hipertrófica mediante 18FDG-PET/TC

S0721 Intestinal Parasitism in Patients With Inflammatory Bowel Disease

INTRODUCTION: A link between parasite colonization has been hypothesized to play a role in the pathophysiology of IBD and other autoimmune diseases. However, the occurrence of intestinal parasitism (IP) in pre-existing IBD and the effects on inpatient outcomes have not been studied. The aim of this study was to examine the inpatient prevalence and outcomes of IP in patients with IBD in the US in the last 5 years. METHODS: Retrospective, observational study using the National Inpatient Sample 2012–2016. All patients with ICD9-10CM codes for IBD were included. The cohort was stratified into ulcerative colitis (UC) and Crohn’s disease (CD). The primary outcome was determining the occurrence and odds of IP in patients with IBD compared to patients with diarrhea but without IBD. Examined parasites included helminths, coccidia and protozoans. Secondary outcomes were morbidity, mortality, resource utilization, colectomy rates, hospital length of stay (LOS), and inflation-adjusted total hospital costs and charges. Multivariate regression analyses were used to adjust for covariates. RESULTS: A total of 1,594,230 patient admissions with IBD were included in the study (37% UC), out of which 1,020 had an associated diagnosis of IP (54% with UC). The mean age was 51 years and 56% were female. For the primary outcome, patients with UC were significantly more likely to have associated IP compared to non-IBD patients with diarrhea (aOR: 1.84, P 0.03). Positive parasitic associations in the UC cohort included Strongyloides, Cryptosporidium, amebiasis and giardiasis. No associations were found between IBD and other parasites. Patients with IBD and associated IP displayed higher additional hospitalization costs, charges and LOS compared to patients with IBD and no IP. Outcomes are depicted in Table 1. CONCLUSION: Inpatients with UC have higher odds of intestinal parasitism with certain organisms compared to non-IBD patients with diarrhea. Despite representing one-third of the IBD cohort, patients with UC accounted for more than half of the cases of associated intestinal parasitism, suggesting its occurrence is higher in this subset of patients. Costs, charges and hospitalization length are longer in patients with IBD and associated intestinal parasitism compared to patients with IBD and no parasitism. This study highlights the importance of considering concomitant parasitic infection in hospitalized patients with IBD.Table 1.: A. Adjusted odds ratios and additional adjusted means for patients with IBD and intestinal parasitism compared to patients with IBD and no intestinal parasitism. B. Adjusted odds ratio for occurrence of selected intestinal parasitic diseases in patients with IBD compared to patients without IBD

Microsporidia in diarrheic patients: detection and evaluation of intestinal inflammation and malabsorption

BackgroundEarly reports on microsporidial diarrhea involved mainly HIV-immunodeficient patients. More recent studies indicate that microsporidial spores may also be detected in immunocompromised persons not infected with HIV as well as in immunocompetent individuals. However, the exact mechanism of microsporidial diarrhea is not clearly defined.ObjectivesThe aims of this study were to evaluate the contribution of microsporidia toward the burden of diarrheal diseases and to investigate the occurrence of associated intestinal inflammation and malabsorption.Patients and methodsStool samples of 237 patients with diarrhea were examined for microsporidial spores using modified trichrome stain. Microsporidia-positive samples were examined for concomitant parasitic infections. Intestinal inflammation was evaluated in patients infected solely with microsporidia ( n = 30) by comparing the fecal lactoferrin level measured by an enzyme immunoassay with that of a control group of healthy, age and sex matched, parasite-free nondiarrheic individuals ( n = 15). Fecal pH and assessment of fecal fat using oil red O stain were used as indictors of carbohydrate and fat malabsorption, respectively.ResultsMicrosporidian spores were detected in 15.6% of diarrheic patients. Considering the median and range values, microsporidia-infected patients showed significantly higher fecal lactoferrin levels (median 49.75, range 2.8-220 μg/g, respectively) and lower fecal pH (median 5.82, range 5.12-6.98, respectively) compared with the control group (median 4.1, range 2.4-31 μg/g and median 6.7, range 6.3-7.16 μg/g, respectively). A significantly greater proportion of microsporidia-infected patients had elevated lactoferrin levels (>7.4 μg/g stool), markedly acidic stool (pH < 6), or increased fecal fat compared with the control group.ConclusionInfection with microsporidia is present in a considerable proportion of diarrheic patients and results in an intestinal inflammatory response as well as carbohydrate and fat malabsorption. Enteric microsporidiosis should be taken into consideration in the management of diarrheal diseases.

Asymptomatic malaria and intestinal helminth co-infection among children in a rural community in Southwest Nigeria.

Malaria is prevalent in sub-Saharan Africa, where other concomitant parasitic infections, including intestinal helminths, are common. However, little is known about how concurrent infections affect the expression or pathogenesis of each other. This study aimed to document the prevalence rates of malaria and intestinal helminths individually and as co-infection among asymptomatic children in a rural community in southwest Nigeria. Apparently healthy children aged 1-17 years, who were enrolled into a larger study that evaluated the efficacy and safety of two anti-helminthic drugs, were evaluated for intestinal helminths by stool examination using the saline wet mount and Kato-Katz methods. Capillary blood from finger prick samples was used for haematocrit determination and malaria screening by microscopy. Data analysis was conducted using SPSS and significance levels were set at p < 0.05. Eighty-nine of 178 (50%) enrolees were male. One hundred and fifteen of the 178 (64.6%) children had at least one intestinal helminthic infection while 69 (60%) thereof harboured multiple helminthic infections. Malaria parasites were encountered in 35/178 (19.7%) of the enrolees. Parasite density was ≤500/μl in 51.4% (18/35), 501-1,000/μl in 9 (25.7%) and 1,000-4,720/μl in 8 (22.9%) of the children. Malaria-helminth co-infection was detected in 24/115 (20.9%) of the children. The prevalence [60/115 (52.2%) versus 8/63 (12.7%) p<0.0001] and severity of anaemia were significantly higher among children with worms compared to those without worms. For mild anaemia this was 53/115 (46.8%; with worms) versus 7/63 (11.1%; no worms p<0.0001); for moderate anaemia 2/115 (1.74%; with worms) versus 1/63 (1.59%; without worms; p<0.271). Malaria and helminths co-infection is common among apparently asymptomatic children in the rural community studied. Co-infections increase the problems associated with anaemia and aggravate the burden of disease in Nigerian children.

Eosinophilic Cationic Protein [ECP] in Fascioliasis and Hydatidosis

Eosinophils and their granules were shown to be significant participants in the inflammatory processes of various helminthic infections. So far, only few reports have dealt with ECP level in parasitic diseases. So, this study aimed at evaluating the serum ECP in fascioliasis and hydatis disease and to compare the ECP level with the blood eosinophil count and serum lgE antibody levels in both diseases. Material and methods: this work included 90 individuals [30 patients with fascioliasis [group I], 30 patients with hydatid disease [group II], and 30 normal persons as control group]. All patients were free from concomitant parasitic infections, viral hepatitis B or C, allergic and autoimmune disorders. ECP was estimated in all patients and controls by radioimmuno assay. Moreover, peripheral blood eosinophil count and serum lgE were also estimated. Results: the mean serum level of ECP was significantly higher in patients with fascioliasis and hydatid disease [31.1±21.4, 20.3±11.6 µg/L, respectively] than the control group [7.1±4.0 µg/L], P=0.001 in each case. Moreover, ECP was significantly higher in fascioliasis group than in hydatid group [P=0.001]. The mean eosinophil count was 3.1x109/L ±2.2 in patients with fasciola infection, 1.4x109/L ±1.0 in patients with hydatid disease, and 0.2x109/L ±0.1 in the control group. Serum level of lgE antibody was found to have a mean value of 178.9±66.7 IU/ml in patients with fascioliasis, 157.9±54.1 IU/ml in patients with hydatid disease, and 90.9±35.5 IU/ml in the control group. ECP was shown to have significant positive correlations with the peripheral blood eosinophil count in both groups of patients. However, it was more significant with fascioliasis, a disease with more degree of eosinophilia. In contrast, no significant correlations existed between ECP and lgE antibody in either the groups. Conclusion: The data indicate a generally greater activity of the eosinophil cell system in fascioliasis and hydatid disease. So, ECP appears to be a useful clinical parameter in parasitic infections with eosinophilia to assess disease activity, inflammatory process, or may serve as a new tool for monitoring therapy.

Changes In Peripheral Leukocyte And Body Fluids Of Onchocerciasis Patients Treated With Ivermectin

This study evaluated the peripheral leukocyte count and the presence of microfilariae in the body fluids of onchocerciasis patients treated with ivermectin. Fifty-three patients over the age 10 years were selected from Ipogun, an onchocerciasis endemic area in Ondo State, Nigeria. Before and after treatment, all patients received a parasitologic and clinical examination that included physical examination, palpation of onchocercal nodules, assessment of microfilarial densities in iliac crest skin snips, diagnosis of concomitant parasitic infections in stool specimens and total leukocytes differential counts. Results indicated that ivermectin did not induce a decrease in the total number of peripheral leukocytes but there was a decrease in the number of eosinophils. Microfilariae were not found in increase frequency in the urine, blood and sputum, while the number of microfilariae per mg of skin snip decreased. Afr. J. Clin. Exper. Microbiol. 2004; 5 (3): 225-230

Multiple parasite infections and their relationship to self-reported morbidity in a community of rural Côte d'Ivoire.

Concomitant parasitic infections are common in the developing world, yet most studies focus on a single parasite in a narrow age group. We investigated the extent of polyparasitism and parasite associations, and related these findings to self-reported morbidity. Inhabitants of 75 randomly selected households from a single village in western Côte d'Ivoire provided multiple faecal specimens and a single finger prick blood sample. The Kato-Katz technique and a formol-ether concentration method were employed to screen faecal samples for Schistosoma mansoni, soil-transmitted helminths and intestinal protozoa. Giemsa-stained blood smears were analysed for malaria parasites. A questionnaire was administered for collection of demographic information and self-reported morbidity indicators. Complete parasitological data were obtained for 500/561 (89.1%) participants, similarly distributed among sex, with an age range from 5 days to 91 years. The prevalences of Plasmodium falciparum, hookworms, Entamoeba histolytica/E. dispar, and S. mansoni were 76.4%, 45.0%, 42.2%, and 39.8%, respectively. Three-quarters of the population harboured three or more parasites concurrently. Multivariate analysis revealed significant associations between several pairs of parasites. Some parasitic infections and the total number of parasites were significantly associated with self-reported morbidity indicators. Our data confirm that polyparasitism is very common in rural Côte d'Ivoire and that people have clear perceptions about the morbidity caused by some of these parasitic infections. Our findings can be used for the design and implementation of sound intervention strategies to mitigate morbidity and co-morbidity.

Loa loa infection in a patient with thymoma

An exceptional observation of a Loa loa infection occurring in a short term traveller with a thymoma is described in details. We discuss the implications of the immunodeficiency induced by a thymoma on a concomitant parasitic infection.

Immune responses against protozoal and nematodal infection in mice with underlying Schistosoma mansoni infection

Schistosoma mansoni infection induces T helper (Th) 2-dominant immune response in mice not only to S. mansoni itself but also to other coexisting antigens. In the present study, we challenged S. mansoni-infected mice with the intestinal nematode, Strongyloides venezuelensis, and the intracellular protozoa, Leishmania major to see whether such Th2-dominant immune responses alter susceptibility of the host to other concomitant parasitic infections. The recovery of S. venezuelensis adult worms from the small intestine was significantly decreased by S. mansoni infection, and the protection to S. venezuelensis appeared to act on migrating larvae. Antibodies elicited by S. mansoni infection showed cross-binding to third-stage larvae antigen of S. venezuelensis. On the other hand, S. mansoni infection did not affect the outcome of L. major infection in both susceptible BALB/c and resistant C57BL/6 mice. Popliteal lymph node cells of BALB/c mice expressed mRNA for interleukin (IL)-10 rather than IL-4, regardless of S. mansoni infection, and those of C57BL/6 mice expressed IFN-γ mRNA upon L. major antigen stimulation, even in S. mansoni-infected mice. Our findings suggest that Th2-dominant immune response induced by S. mansoni protects mice from intestinal helminthic infections, whereas they do not always modulate protozoal infections.

Frequency of Recovery of Blastocystis hominis in Clinical Practice

We examined the frequency of isolation of Blastocystis hominis from stools of patients seen in an indigent-care teaching hospital. Over a 2-year period, 2,744 stool specimens were examined prospectively. B. hominis was found in 262 stools (9.5% of all stool specimens and 53.5% of the positive specimens). Clinical data were obtained from 80 patients with stools positive for B. hominis. B. hominis was the only parasite isolated in 39 of 47 (83%) of the adults, compared with 17 of 33 (52%) of the children (p = 0.006). All but 2 of 52 patients without concomitant parasitic infection or bacterial pathogens in stool had gastrointestinal symptoms (41 abdominal pain, 26 diarrhea, and 5 vomiting), but no association was seen with fever, peripheral leukocytosis, stool occult blood, fecal leukocytes, or endoscopic or radiologic evidence of colitis. Therefore, B. hominis was frequently recovered from stools examined in a hospital clinical parasitology laboratory. The clinical presentations of patients in our series did not suggest that B. hominis was invasive. Most patients with B. hominis probably do not require treatment since they will either have spontaneous resolution of symptoms or will be found to have an alternative explanation for their problem.

Changes in intestinal fluid transport and immune responses to enterotoxins due to concomitant parasitic infection.

The effect of a parasitic infection on enterotoxic diarrhea and on local and systemic formation of antibody to the toxin after immunization was studied in mice. Trichinella spiralis infection was chosen as the model, since the effects of the parasite when residing in both intestinal and extraintestinal sites can be studied. It was found that during the intestinal stage of the infection, the fluid response to cholera toxin as well as dibutyryl-cyclic adenosine 3',5' -monophosphate was greatly enhanced and that this was associated with a marked reduction in the absorption of fluid from the intestine. Later in the infection (migration stage), fluid accumulation in response to cholera toxin was significantly reduced, whereas absorption was normal and secretion in response to dibutyryl-cyclic adenosine 3',5'-monophosphate was somewhat increased. Still later in the infection (muscular stage), the fluid-secretory response to cholera toxin was normal. There was a drastic depression of local formation of antitoxin of both immunoglobulin and immunoglobulin classes in mice given the first two of four oral immunizations with cholera toxin during the intestinal stage of T. spiralis infection. When the priming was given before or after the intestinal stage, the local antitoxin response was not affected. The titers of circulating antibodies were also depressed in mice given the first immunizations during the intestinal stage. In addition, significant though less pronounced depression of the serum antibody response was observed in mice primed during the extraintestinal stage.