Ancylostoma duodenale infection: a study of serum immunoglobulin G4 response to the excretory secretory antigen of adult worm

The serum anti-Ancylostoma duodenale immunoglobulin (Ig) G4 antibody response to fraction III of the partially purified excretory secretory antigen of adult worm (Ad III ESA) was studied. The work included 60 patients with A. duodenale infection (GI), 40 patients with other parasitic infections (GII) and 30 apparently healthy parasite-free controls (GIII). Level of serum specific IgG4 was measured by indirect enzyme linked immunosorbent assay and compared with serum specific IgG, IgG 1, 2 & 3 subclass antibodies. Patients of GI had gastro-intestinal manifestations and symptoms suggestive of anaemia, and by investigations they had anaemia in 31.7% & eosinophilia in 100%. Measuring the intensity of A. duodenale infection, quantified as fecal egg counts, in patients of GI revealed that 60%, 30% & 10% had light, moderate, and heavy infections, respectively. The serum anti-Ad III ESA IgG & IgG 1-4 subclass antibodies were significantly elevated (P < 0.001) in patients of GI compared with GIII. Serum specific IgG4 was expressed in 100% of patients of GI at a significantly highly elevated level than IgGI (P < 0.01), IgG2 & IgG3 (P < 0.001). Specific IgG1 was expressed in 88.3% of patients of GI at a significantly elevated level (P < 0.001) than IgG2 & IgG3 which were expressed in 31.7% & 38.3%, respectively and elevated to a moderate extent. Serum specific IgG4 showed a 1.0, 1.1, 3.1 & 2.6-fold increase in detection rate of positive cases than IgG, IgG1, IgG2 & IgG3, respectively. The highest ability to differentiate between infected and healthy subjects was by serum specific IgG4 recording a discrimination coefficient of 9.4, while IgG, IgG1, IgG2 & IgG3 recorded 5.2, 6.3, 3.2 & 3.4, respectively. Serum specific IgG4 showed a significant positive correlation (r = 0.41, P < 0.001) with the intensity of A. duodenale infection, as was demonstrated by IgG & IgG3 (P < 0.01 & P < 0.05, respectively). Detection of serum anti-Ad III ESA IgG4 antibody recorded a 100% sensitivity that was significantly higher (P < 0.001) than IgG1, IgG2 & IgG3, but insignificantly different (P > 0.05) from IgG. Finally, serum specific IgG4 recorded a 100% specificity that was significantly higher than IgG, IgG2, IgG3 (P < 0.01) & IgG1 (P < 0.05). They showed cross-reactions with ascariasis, lymphatic filariasis and strongyloidiasis. The results are discussed.

[Iron-deficiency anemia related to ancylostoma duodenale infection among Ethiopian immigrants to Israel]

BACKGROUND

Among the diseases imported by the Ethiopian immigrants to Israel are many parasite infections. Hookworm infections, caused by the nematodes Necator americanus and Ancylostoma duodenale, involve the gastrointestinal tract, causing iron-deficiency anemia.

OBJECTIVES

To evaluate the rate of iron-deficiency anemia related to hookworm infections among immigrants from an endemic area.

METHODS

We retrospectively studied the medical records of all Ethiopians over the age of 18, who immigrated to Israel in the early 90's, in two primary care clinics of Clalit Health Services in Ofakim.

RESULTS

Sixty patients (64%) had evidence of A. duodenale infection. The mean hemoglobin level was 11.92.3 g/dl in the Ancylostoma group and 13.81.6 g/dl in the control group (p = 0.0001). Analyzing the data according to the patient's sex revealed significant differences in the hemoglobin levels between the Ancylostoma group and the control group. Patients infected with A. duodenale had significantly lower mean corpuscular volume (MCV) and serum iron, and were likely to have eosinophilia and hypoalbuminemia.

CONCLUSION

Among the Ethiopian immigrant population, Ancylostoma duodenale infection is a common cause of iron deficiency anemia. In young patients it should be ruled out before invasive and expensive investigations are performed.

T-lymphocyte subsets in patients with hookworm infection in Zaria, Nigeria

Peripheral lymphocyte subsets CD3, CD4, CD8 were studied using monoclonal antibodies to determine the mechanism of immunosuppression observed in an earlier study with total T-cells using the sheep erythrocyte rosetting technique. The study was carried out in 37 Nigerian patients with hookworm infection (Necator americanus and Ancylostoma duodenale and 17 healthy Nigerians as controls. The leucocyte migration inhibition (LMI) test was also carried out to assess the functional integrity of the lymphocytes, while the hookworm status of the patients was assessed by the Stoll technique for measuring egg counts. The results of the T-cell studied showed that CD3 and CD4 cell percentages were significantly depressed in hookworm patients compared to controls (P<0.05). The difference between mean CD8 percentages and absolutes in hookworms patients and controls were not significant. Absolute CD3 and CD4 numbers were not significantly lowered compared to controls in the study and CD4/CD8 ratios were insignificantly reduced. Patients with polyparasitism including hookworm infection showed significant reduction in CD3 and CD4 cells when compared with controls and with patients with hookworm infection alone. The leucocyte migration inhibition response to purified protein derivative of M. tuberculosis (PPD) was significantly decreased in hookworm patients compared to controls, confirming that functionally cell mediated immunity is depressed in hookworm infection.

Epidemiology of human ancylostomiasis among rural villagers in Nanlin County (Zhongzhou Village), Anhui Province, China: II. Seroepidemiological studies of the age relationships of serum antibody levels and infection status

Anti-hookworm antibody serologic responses were measured in residents of an Anhui provincial Chinese village where Ancylostoma duodenale is the predominant hookworm. Antibody responses were measured against either soluble infective third-stage larval (L3) or adult antigens. Immunoglobulins of the IgG class, especially IgG4 correlated with both the prevalence and intensity of A. duodenale hookworm infections. In contrast, there was an inverse correlation with IgM, but no correlation with IgA or IgE. Circulating IgG4 antibody responses might serve as a surrogate marker for active A. duodenale hookworm infection.

Enzyme-linked immunoelectrotransfer blotting analysis of human serologic responses to infective hookworm larval antigen

OBJECTIVE

To explore the possibility of using specific antigens for immunodiagnosis of hookworm disease in endemic area.

METHOD

Infective third-stage larvae of the canine hookworm, Ancylostoma caninum (A. caninum), were prepared as the source of antigen. Enzyme-linked immunoelectrotransfer blotting (EITB) was employed as an immunodiagnostic method.

RESULTS

Two immunodominant bands of hookworm antigens (42 kDa and 55 kDa) were recognized by the sera of hookworm-infected patients (serum dilution 1:200; antigen centrifuged at 36,000 r/m for 20 minutes, but not by sera from negative controls.

CONCLUSION

The 42 kDa and 55 kDa A. caninum antigens might be the specific antigens that could be used for immunodiagnosis of hookworm disease in endemic area.

Immunoglobulin G subclass antibodies against excretory/secretory antigens of Ancylostoma caninum in human enteric infections

Most patients with proven or suspected enteric infection with the common hookworm of dogs, Ancylostoma caninum, produce immunoglobulin G (IgG) and IgE antibodies to an immunodominant excretory/secretory antigen (Ac68) of the parasite. These antibodies were detected in both enzyme-linked immunosorbent assay (ELISA) and Western blots; the Western blot to detect IgG antibodies to Ac68 was the most specific and sensitive. The subclasses of IgG of the antibody response to the parasite were analyzed using Western blots with anti-IgG subclass-specific monoclonal antibodies as marker systems in an attempt to further improve the specificity of the assay. Eight patients with confirmed enteric infections with A. caninum (positive controls) were tested; six had antibodies in all IgG subclasses against Ac68. Twenty sera from patients with suspected enteric infection with A. caninum (manifested as eosinophilic enteritis or unexplained abdominal pain with peripheral eosinophilia) were tested; 16 had total IgG antibodies to Ac68, while IgG1, IgG2, IgG3, and IgG4 responses were found in 11, 10, 9, and 12 of these sera, respectively. Small numbers of sera from groups of patients infected with other helminths and from healthy blood donors had various combinations of IgG, IgG1, IgG2, and IgG3 antibodies to Ac68, but none of these sera had IgG4 antibodies to Ac68. Sera from all nine patients with human hookworm infection had IgG, IgG1, IgG2, and IgG3 antibodies to Ac68 and eight of the nine were also positive for IgG4 antibodies. These results indicate the Western blot to detect IgG4 antibodies to Ac68 is the most reliable immunodiagnostic test yet described for enteric infection with A. caninum, although this test does not discriminate between infections with human and canine hookworms.

Pathogenicity of the hookworm, Ancylostoma pluridentatum, in a Florida panther (Felis concolor coryi) kitten

We evaluated clinical signs and administered anthelmintic treatment to a wild-caught, captive Florida panther (Felis concolor coryi) kitten from Big Cypress National Preserve, Florida (USA) infected with the hookworm, Ancylostoma pluridentatum. Clinical signs observed included poor body condition, lethargy, and below normal red blood cell numbers, hemoglobin concentration, and packed cell volume, and elevated eosinophil numbers. In addition, a maximum of 936 Ancylostoma sp. eggs/g of feces were found on Day 11 of captivity. Following oral administration of 20 mg/kg pyrantel pamoate on Day 11, 26 A. pluridentatum were collected from the feces. Based on the resolution of clinical signs, cessation of egg shedding, and a return to normal hematologic values following anthelmintic treatment, we believe that infection with A. pluridentatum was the primary cause of the stressed conditions in the panther kitten.

Immunosuppression in Nigerians with hookworm infection

T rosette cells results in patients with (Necator americanus and Ancylostoma duodenale) hookworm infection, divided into groups on the basis of the degree of anaemia (Group I had marked anaemia Hb 1-7, hypochromia ), Group II had moderate anaemia (Hb 8-11, hypochromia ++) and Group III had no signs of anaemia despite the underlying hookworm infection), were compared with results in 28 healthy controls who had no signs of other infection and excreting no ova of hookworm or other parasites. The level of sheep erythrocyte rosette-forming T-lymphocytes (SE-TL) in the patients (Group I:42 +/- 8%; Group II:45 +/- 11%; Group III:47 +/- 6%) was markedly reduced compared to controls (58 +/- 13%) (P < 0.001). The leucocyte migratory responses to purified protein derivative (P.P.D); were significantly (P < 0.05) reduced in all the subgroups as compared with the controls. The results support the hypothesis of the existence of immunosuppression in patients with hookworm infection.

Haematological changes in dogs infected with Ancylostoma duodenale

A definite relation between the intensity of Ancylostoma duodenale and haematological changes in dogs were studied. There was a relation between the increase in egg count with the haemoglobin percentage. The present study reported haematological data collected during the acute phase of experimental infection with A. duodenale.

Occult enteric infection by Ancylostoma caninum: a previously unrecognized zoonosis

BACKGROUND/AIMS

Human disease caused by the canine hookworm Ancylostoma caninum and a high incidence of eosinophilic enteritis have been reported from northern Queensland, Australia. The aim of this study was to evaluate patients with unexplained abdominal pain and a possible association with cryptic infections by A. caninum.

METHODS

The clinical and demographic features of patients from this region with eosinophilic enteritis (group A1, n = 42), obscure abdominal pain associated with (group A2, n = 105) and without (group A3, n = 84) blood eosinophilia were reviewed and sera were tested against A. caninum excretory-secretory antigens by enzyme-linked immunosorbent assay (ELISA) and Western blot. Four additional patients, two with confirmed A. caninum, had hookworm infection.

RESULTS

The level of dog ownership in these four groups was 79%-100%, higher than in the local population (P < 0.001). The ELISA tested positive in 71% of A1, 67% of A2, and 30% of A3, versus 8% in controls (P < 0.002). All cases tested were positive on Western blot versus 10% of controls (P < 0.0001). The ELISA values increased with chronicity and decreased during convalescence.

CONCLUSIONS

We conclude occult human A. caninum infections are common and are characterized by eosinophilic enteritis and obscure abdominal pain with or without blood eosinophilia. The diagnosis can be confirmed by serology.

[The clinical laboratory indices in ancylostomiasis among the population of Kindia Prefecture (Republic of Guinea)]

Clinical and laboratory data have been compared in patients with ankylostomiasis and healthy population of Guinea Republic. An increase in ankylostomiasis morbidity during the humid season has been observed. The clinical pattern of the disease did not differ from that earlier described in literature. Anemia and eosinophilia were the most persistent signs of the disease. The patients with ankylostomiasis revealed an elevated IgM level and a trend towards an increase in 0-lymphocyte population, which is indicative of certain shifts in cellular and humoral immunity.

[Parasitologic, clinical, hematologic and serologic findings in puppies after lactogenic infection with Ancylostoma caninum ERCOLANI 1859 (Ancylostomidae)]

The correlation between intensity of Ancylostoma caninum infections in bitches and the intensity of lactogenic infections and clinical signs of their puppies was investigated. On average, 825, 1,867 or 2,125 specimens were observed in litters of two bitches inoculated with 5,000, 10,000 or 20,000 third stage larvae (LIII) respectively, at the day of conception. Adverse effects of the infection on the growth and behaviour of the puppies were observed after onset of their second week of life: 11/27 puppies died during the fourth week. The body weight of puppies surviving 28 days was up to 750 g less than that of uninfected controls. Eosinophilia, erythroblastosis and microcytic, hypochromic anemia developed in all puppies during their first four weeks. The IFA test (LIII antigen) was positive for only 5/18 heavily infected puppies after uptake of colostrum.

[Uncinariasis in younger infants]

In order to determine the main clinical and laboratory manifestations associated with the infestation by an uncinaria during the first year of life, 42 children were studied from a group hospitalized between the years 1980 and 1985 in whom the main diagnosis at their time of leave from the hospital was parasitosis. Over 31 patients (74%) showed some degree of malnutrition, and severe in 24 of them (57% of the total). Clinical manifestations were mainly related to anemia (paleness, lack of air) and active intestinal bleeding (enterorrhagia, melena). Among the laboratory findings, 80% of the patients were shown to have anemia and in 24% of them, their hemoglobin levels were less than 5 g/dL, in more than half the anemia was normocytic normochromic. Also included are particularities concerning uncinariasis in the breast-feeding infant and some differences with the infection in the adult.

Molecular basis of hyperlipidemia in golden hamsters during experimental infection with Ancylostoma ceylanicum (Nematoda:Strongylidae)

An infection of golden hamsters with Ancylostoma ceylanicum, a hookworm parasite, induced profound hyperlipidemia, particularly hypertriglyceridemia, and the effect was directly related to the degree of infection. A significant increase was also noticed in serum cholesterol and phospholipid levels. The appearance of lipoprotein-X, an abnormal low density lipoprotein, was detected in the serum of hookworm-infected animals. The hyperlipidemia was further characterized by an increase in very low density lipoproteins (VLDL) and low density lipoproteins (LDL) with a concomitant decline in high density lipoproteins (HDL). Decreased lipolytic activities, especially triglyceride lipase, in hepatic tissue and induction of lipolytic activities in intestine and adipose tissues indicated mobilization of fats from adipose and jejunum with a defective removal of triglyceride-rich lipoproteins in hepatic tissues. Accumulation of lipids in liver and depletion in adipose tissue supported these results. The derangement may have a significant effect on host parasite interaction and is an important pathophysiological feature occurring during experimental ancylostomiasis.

Experimental infection of humans with Ancylostoma ceylanicum: clinical, parasitological, haematological and immunological findings

Experimental infection of two human volunteers with Ancylostoma ceylanicum produced patent infection. Following percutaneous infection with 1200 infective larvae, there was no evidence of skin eruption, however, severe abdominal discomfort was experienced by both subjects coincidently at various intervals. Eggs appeared in the faeces five weeks after infection; low level excretion continued until termination of the infection 30 weeks after inoculation. Infection had no significant effect on haemoglobin concentrations, total white cell counts, platelet levels or spontaneous and phytohaemagglutinin-induced lymphocyte transformations in either of the infected volunteers. Persistent eosinophilia began four weeks after infection in both infected persons; lymphocytes from one subject responded transiently to stimulation with larval antigen while lymphocytes from both infected subjects responded to stimulation with adult worm antigen. Specific IgM and IgG antibodies appeared two and six weeks after infection, respectively, and persisted for the duration of the experiment.

Ancylostoma ceylanicum (Looss, 1911) in golden hamsters (Mesocricetus auratus): pathogenicity and humoral immune response to a primary infection

The response of hamsters to Ancylostoma ceylanicum was studied between days 13 and 200 after infection. The infected hamsters showed signs of anaemia, particularly between the 13th and 60th days. A significant loss in body-weight in the infected animals was also observed during this period. Serological studies with agar gel-diffusion, counterimmunoelectrophoresis and indirect haemagglutination tests revealed positive reactions between the 20th and 60th days followed by a negative response in the latent period between the 60th and 200th days of infection, counterimmunoelectrophoresis test remained positive for a period of 150 days in this experimental model.

Parasitological, hematologic, and immunologic responses in acute and chronic infections of dogs with Ancylostoma ceylanicum: a model of human hookworm infection

A model of human hookworm infection has been defined with a strain of Ancylostoma ceylanicum that is known to be infective for humans. In the first experiment, dogs were infected with between 150 and 12,150 filariform larvae and followed up for six weeks. A direct relation was found between the size of infecting dose, fecal egg excretion, intestinal adult worm burden, and worm distribution in the bowel. Dogs with heavy infection developed bloody diarrhea and iron-deficient anemia. In the second experiment, dogs infected with 2,000 larvae excreted ova until autopsy 36 weeks after infection. Normocytic anemia and blood eosinophilia coincided with maximal egg excretion. Transitory lymphocyte stimulation was seen with adult worm antigen. The specific IgM antibody response was transient, but IgG antibodies persisted indefinitely. Marked skin immediate hypersensitivity and Arthus (but no delayed) hypersensitivity reactions were seen to injected larval and adult antigens. Thus, dogs develop both hookworm disease and chronic infections similar to those seen in humans.

The anticoagulant effects of the hookworm, ancylostoma ceylanicum: observations on human and dog blood in vitro and infected dogs in vivo

Extracts of adult Ancylostoma ceylanicum prolonged the prothrombin time (PT) and partial thromboplastin time with kaolin ( PPTK ) of both human and dog plasmas in vitro. Excretory/secretory (E/S) products of these worms had similar effects while larval extract prolonged the PTTK only. Thus, the anticoagulant activities of this parasite are dependent upon the stage of the worm's life cycle. Collagen- and ADP-induced platelet aggregation were inhibited by adult and larval extracts. When the peripheral blood and bleeding times of dogs with varying worm burdens were examined, the only abnormality was shortening of the PTTK in the most heavily infected animals. Homogenates of dog small bowel subjacent to adult hookworms prolonged the PT of dog plasma and electron microscopical examination of this tissue revealed aggregation of platelets in blood venules without fibrin deposition. Thus, this study provides evidence that the anticoagulant properties of hookworms may have biological significance in infected animals.

Investigation of the haemolytic effects of Ancylostoma ceylanicum: observations on infected dogs in vivo and human and dog blood in vitro

Investigations into the probable role of haemolysins in the causation of hookworm anaemia have been undertaken in living infected dogs. Secondly, the effects of living hookworms and various worm products on erythrocytes in vitro have been assessed. In dogs infected with varying numbers of A. ceylanicum, severe microcytic anaemia developed in the most heavily infected animals six weeks after infection. Erythrocytes from the latter animals showed significantly greater autohaemolysis in the presence of added glucose. When serum bilirubin and methaemalbumin, plasma haemoglobin, urinary urobilinogin and osmotic fragility of their red cells were measured, however, no evidence of haemolysis was detected. Erythrocytes from these animals appeared normal under scanning electron microscopy. In in vitro studies varying concentrations of adult worm extract had no effect on the haemolysis of either dog or human erythrocytes in the presence or absence of glucose nor on their mechanical fragility. There was no increase in 51Cr release from dog or human labelled red cells when incubated with either adult worm extract or excretory/secretory products of worms. Living adult worms caused an increase in 51Cr release from human but not dog labelled erythrocytes. Thus, the role of haemolysins in the genesis of hookworm anaemia is minimal.

Secretion of a proteolytic anticoagulant by Ancylostoma hookworms

Hookworms of the genus Ancylostoma secrete an anticoagulant that both inhibits the clotting of human plasma and promotes fibrin clot dissolution. This anticoagulant activity is attributable to a 36,000 dalton proteolytic enzyme. The protease can degrade fibrinogen into five smaller polypeptides that intrinsically have anticoagulating properties, covert plasminogen to a mini-plasminogen-like molecule, and hydrolyze a synthetic peptide substrate with specificity for elastolytic enzymes. It is hypothesized that the parasite uses this enzyme to prevent blood clotting while feeding on villous capillaries.

[Ancylostomotic anemia: a physiopathological study]

Foram estudados 17 casos de ancilostomose e determinados alguns parâmetros hematológicos como: dosagem de hemoglobina, do ferro sérico e da transferrina, contagem de hemácias, hematócrito, volume corpuscular médio (VCM) e hemoglobina corpuscular média (HCM). O estudo incluiu também a obtenção de alguns dados eritrocinéticos, como a determinação da velocidade de decaimento do ferro plasmático (T1V2 do 59Fe) e da incorporação do ferro à hemoglobina. O estudo radioisotópico permitiu ainda determinar o volume de sangue e a quantidade de hemoglobina perdida nas fezes, bem como o teor de ferro reabsorvido dessa hemoglobina. Estabeleceram também o grau de infecção através da contagem de ovos e de vermes nas fezes. Os doentes não apresentaram evidente alteração nutricional. A carência de ferro foi o fator comum a todos os casos que exibiram anemia, constituindo a base fisiopatológica da anemia ancilostomótica. O verme fixado à mucosa duodenal suga o sangue do hospedeiro e esta espoliação de sangue a longo prazo provoca a anemia. O volume de sangue perdido é geralmente proporcional ao grau de infecção, mas a quantidade de hemoglobina perdida mostrou ser independente do volume de sangue espoliado. A reabsorção de grande parte do ferro da hemoglobina perdida na luz intestinal concorre para que a anemia se estabeleça mais tardiamente que em outras hemorragias como a vaginal. Os indivíduos anêmicos foram submetidos a transfusões de sangue e com isso apresentaram melhora clínica e laboratorial, imediata mas temporária. A cura clínica foi estabelecida somente após tratamento adequado com vermífugos.

Pathogenicity of hookworms. The significance of population regression for the pathogenicity of hookworms

A method is described to estimate the reduction of the hookworm population in the host during the infection period (population regression). A formula is proposed to estimate the average worm population during the infection period, on the assumption that a decreasing hookworm population causes a decrease in daily blood loss. Daily blood loss per worm was calculated for Ancylostoma caninum: 43 microliters; for A. ceylanicum: 14 microliters for A. braziliense: 5 microliters. Accordingly hookworms cause blood loss one half to two thirds smaller than formerly assumed.

Hookworm infection and blood changes in the rural population of Dezful area in Khuzestan, South-West of Iran

Hookworm infection and blood changes relationship in the 937 infected persons in 6 villages of Dezful area in Khuzestan, South West of Iran, were studied. The most prevalent intestinal helminths in the area were Ascaris lumbricoides 21%, Ancylostoma duodenale 35%, Trichostrongylus spp. 17% and Hymenolepis nana 17%. Only 2% of the hookworm infected persons showed high intensity of infection which accompanied with rather low haemoglobin level of 9.4 g/100. The eosinophil level was 12-d16.5%. The results of this study indicates that the anaemia produced by hookworm infection in Khuzestan is not significant.

Experimental Ancylostoma tubaeforme infection of cats: changes in blood values and worm burden in relation to single infections of varying size

Worm-free cats about 12 weeks old were infected with 100, 500, 1,000 and 2,000 third-stage larvae (L3) of Ancylostoma tubaeforme. The changes in packed cell volume (PCV) and haemoglobin content were monitored, and the worm populations developing in each infection recorded. Cats receiving infection doses of 1,000 L3 and above showed morbidity symptoms by the third week and a rapid decline especially in the PCV value. The low dose rates (500 L3 and below) produced an apparently symptomless condition without pronounced changes in the blood values. Adult hookworm populations were linearly related to the logarithm of the dose of infective larvae administered, but there was a lower female to male ratio (FMR) at high dose levels. No significant size differences were observed in the adult hookworm populations.

alpha 1-Acid glycoprotein, alpha 1-antitrypsin, and ceruloplasmin in human intestinal helminthiases

alpha 1-acid glycoprotein, alpha 1-antitrypsin, and ceruloplasmin levels were followed in 150 children from the rural tropics after arrival in the temperate zone. It is postulated that multiple intestinal helminthiases, especially ancylostomiasis, cause an acute phase type of reaction which is enhanced by immunization with T.A.B.-cholera vaccine.

Serum protein pattern of mice during infection with single and repeated doses of Ancylostoma caninum larvae

Electrophoretic pattern of serum protein in mice during Ancylostoma caninum larval infection with various single and repeated doses were observed to ascertain whether these changes take place according to their increase in dose levels. Comparison between single and repeatedly infected groups were also made statistically.

Arrested development in Ancylostoma duodenale: course of a self-induced infection in man

The course of self-induced infection with about 100 Ancylostoma duodenale larvae was followed by twice-weekly blood and stool examinations. After a small initial increase, no further change in eosinophil counts occurred until the 33rd week of infection when they began to increase sharply. Seven weeks later, eggs were first observed in stools. Thus, in this infection, the prepatent period was five times the expected. It is suggested that a strain of A.duodenale exists which either 1) has an inherent, abnormally long prepatent period or 2) has a prepatent period which is susceptible to change depending upon the environmental conditions experienced by the free-living larvae. In either case, the third stage larvae probably enter a hypobiotic state within the host which lasts for about 8 months.