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PubMed1999

Parasitic infections. Treatment and developmental therapeutics. 1. Necatoriasis.

Necator americanus is a nematode hookworm of the family Ancylostomatidae, subfamily Necatorinae. This nematode parasite, which is distinguished by two chitinous cutting plates in the buccal cavity and fused male copulatory spicules, is the causative agent of necatoriasis, a hookworm disease prevalent in the Americas as well as in the tropical regions of Africa, southern Asia, and Polynesia. The adult parasites attached to the villi of the small intestines will suck blood causing abdominal discomfort, diarrhea and cramps, anorexia, wight loss, and in advanced disease, hypochromic microcytic anemia. Hookworm infections in man, especially in children, are one of the leading causes of iron-deficiency anemia resulting directly from intestinal capillary blood loss following the feeding activities of fourth-stage (L4) larva and adult worms. Another clinical manifestation often associated with hookworm infections is cutaneous larva migrans (CLM). It is a well recognized, usually self-limiting condition caused by the infectious larvae of nematodes. CLM is characterized by skin eruption and represents a clinical description rather than a definitive diagnosis. Of the hookworm parasites, the dog and cat worm Ancylostoma braziliense is the most common causing CLM, although many other species have been implicated. The major subject of this review article will be discussion of the evolution of therapies and treatment of human necatoriasis and the development of experimental infections with N. americanus. Difference in the clinical efficacies of mebendazole and albendazole will be discussed along with drug resistance of N. americanus.

Albendazole↗
PubMed1989

Evaluation of albendazole, pyrantel, bephenium, pyrantel-praziquantel and pyrantel-bephenium for single-dose mass treatment of necatoriasis.

An effective drug for single-dose mass treatment of necatoriasis was sought by testing three drugs and two drug combinations in Ethiopian immigrants to Israel found to have light infections. The drugs tested sequentially in single-doses were pyrantel pamoate (20 mg kg-1, 81 subjects); bephenium hydroxynaphthoate (2.5-5 g, 65 subjects); combined pyrantel and bephenium (25 subjects); combined pyrantel (20 mg kg-1) and praziquantel (40 mg kg-1) (16 subjects); and albendazole (400 mg, 77 subjects). Follow-up under conditions without likelihood of reinfection was by one stool examination. Cure rates with albendazole, pyrantel-bephenium and pyrantel-praziquantel were 84, 80 and 81% respectively; these rates were significantly higher than the 49% found for bephenium and the 51% for pyrantel (P less than 0.05). Egg reductions in those not cured were pyrantel (22%), bephenium (6%), pyrantel-bephenium (34%), pyrantel-praziquantel (3%) and albendazole (6%). Albendazole was the most promising single drug treatment; unexpected was the high effectiveness of pyrantel-praziquantel in combination.

Adolescent↗
PubMed2004

Immune responses in human necatoriasis: association between interleukin-5 responses and resistance to reinfection.

Cytokine and proliferative responses to Necator americanus infection were measured in a treatment-reinfection study of infected subjects from an area of Papua New Guinea where N. americanus is highly endemic. Before treatment, most subjects produced detectable interleukin (IL)-4 (97%), IL-5 (86%), and interferon (IFN)- gamma (64%) in response to adult N. americanus antigen. Pretreatment IFN- gamma responses were negatively associated with hookworm burden, decreasing by 18 pg/mL for each increase of 1000 eggs/gram (epg) (n=75; P<.01). Mean IFN- gamma responses increased significantly after anthelmintic treatment, from 166 to 322 pg/mL (n=42; P<.01). The intensity of reinfection was significantly negatively correlated with pretreatment IL-5 responses, decreasing by 551 epg for each 100 pg/mL increase in production of IL-5 (n=51; P<.01). These data indicate that there is a mixed cytokine response in necatoriasis, with worm burden-associated suppression of IFN- gamma responses to adult N. americanus antigen. Resistance to reinfection is associated with the parasite-specific IL-5 response.

Adolescent↗
PubMed2005

The assessment of hookworm calreticulin as a potential vaccine for necatoriasis.

A vaccine against the human hookworm Necator americanus is urgently required to reduce hookworm-induced morbidity in endemic areas. In the present study, recombinant hookworm calreticulin, a nominated vaccine candidate, has been tested in mice. Mice given calreticulin had 43-49% fewer worms in their lungs, compared to non-vaccinated controls, following challenge infection with infective hookworm larvae. These levels of protection were achieved in the absence of adjuvant following intraperitoneal administration of three doses of 15 microg antigen. Antigen was also encapsulated in PLG microparticles. Encapsulated calreticulin elicited higher levels of anti-calreticulin IgG1 than free antigen but failed to induce protective immunity. The protection induced by free calreticulin was associated with low levels of serum IgE and moderate lung eosinophilia whilst administration of calreticulin-loaded microparticles was associated with high levels of serum IgE and higher lung eosinophil activity, suggesting that the classical Th2 phenotype may not always be associated with protective immunity, albeit in experimental necatoriasis.

Animals↗
PubMed2000

Necatoriasis: treatment and developmental therapeutics.

Two hookworm parasites, Necator americanus and Ancylostoma duodenale, infect approximately one billion people worldwide. These hookworms are one of the leading causes of iron-deficiency anaemia especially in children, resulting directly from intestinal capillary blood loss following the feeding activities of fourth-stage (L(4)) larva and adult worms. If ignored, human hookworm infections can retard growth and the intellectual development of children. Another clinical manifestation often associated with hookworm infections is cutaneous larva migrans (CLM). It is a well recognised, usually self-limiting condition caused by the infectious larvae of nematodes, especially Ancylostoma spp. CLM is characterised by skin eruption and represents a clinical description rather than a definitive diagnosis. Of the hookworm parasites, the dog and cat worm A. braziliense and A. caninum are the most common nematodes causing CLM, although many other species have also been implicated. The major subject of this review article will be discussion of the evolution of therapies and treatment of human necatoriasis and the development of experimental infections with N. americanus. Difference in the clinical efficacy of mebendazole and albendazole will be discussed along with drug resistance of N. americanus.

Ancylostomiasis↗
PubMedDate not supplied

[Epidemiological study of intestinal helminthiasis in the island of Tortuga (Haiti). I. Prevalence of trichocephalosis, ascaridiasis and necatoriasis studied from elimination of eggs in the stools].

An epidemiological survey is conducted by spot-checks over about 10% of the population of Tortuga Island in order to estimate the prevalence of intestinal helminthiasis in that region of the Republic of Haïti, by researching the presence of eggs in faeces. Population sample is representative of the whole of the island's population excepting the 0-4 years old group whose faeces are difficult to obtain. Faeces are examined through the Kato method, a very simple, quick and remarkably accurate procedure. Trichuriasis and ascariasis, which are transmitted in the area around the house, affect mainly children, but also adults. Women seem to be more often infested than men by Ascaris lumbricoides. Necatoriasis, the farmer's disease, hits primarily young men and elderly women who spend most time in the fields. It is observed in inland villages where people are engaged in agricultural production, with a higher incidence if they are located in a not so sloping zone.

Adolescent↗
PubMedDate not supplied

[Evaluation of the effectiveness of thiabendazole, pyrantel and mebendazole in the treatment of necatoriasis in children].

A study was made of 48 patients from the different departments of the Hospital del Niño, DIF, in which hookworm eggs were demonstrated by qualitative coproparasitoscopic study (CPS). During the study, quantitative CPS was practiced on them by Stoll's dilution and the Harada-Mori technique, for the identification of the hookworm larvae. They were divided into three groups: A, B and C (16 patients in each group); the study was single-blind. The effectiveness of the evaluated drugs was based on the disappearance or diminution of hookworms eggs in the CPS (Stoll) practiced 2 weeks after the drug treatment had finished. The work was done with patients parasitized by Necator americanus (verified by the Harada-Mori technique). The A group was given pyrantel pamoate; the B group, thiabendazole and the C group, mebendazole. The results obtained were statistically processed by means of X2 proportions. There was no significant difference between the three groups when a light to moderate necatoriasis was treated; when a massive infection was involved, there was a significant difference and it was found that the best drug was pyrantel pamoate administered at the dose of 20 mg/kg/day/3 days. There were few side effects in the three groups, but they were not sufficient to cause suspension of the treatment. The cheapest drug was thiabendazole.

Adolescent↗
PubMed1995

Immunoepidemiology of human necatoriasis: correlations between antibody responses and parasite burdens.

In this paper we describe the relationship between antibodies to Necator americanus stage-specific antigens and parasite burden in an endemically-infected population in Papua New Guinea. Using an age-structured analysis, we show that the correlation coefficient between levels of IgG against adult worm excretory-secretory (ES) antigen and parasite burden declined significantly with host age from positive in younger hosts to significantly negative in older hosts. A trend towards similar patterns was present for anti-larval IgG both pretreatment and after reinfection, and for anti-ES IgM and anti-ES IgE pretreatment. These patterns are consistent with a role for these isotypes in a protective immune response, although parasite-induced immunosuppression may provide an alternate explanation. This is another demonstration of possibly protective responses to N. americanus infection.

Adolescent↗
PubMed2000

Epidemiology of human geohelminth infections (ascariasis, trichuriasis and necatoriasis) in Lushui and Puer Counties, Yunnan Province, China.

Between April and June of 1998, the prevalence and intensity of geohelminth infections caused by hookworm, Ascaris and Trichuris were investigated in two rural Yunnan villages. In Liuku, a village of Lisu indigenous people in Lushui County, there was an overall geohelminth prevalence of 72% (48%, 43% and 16% for hookworm infection, ascariasis, and trichuriasis, respectively). The prevalence of ascariasis was greatest among preschool and school aged children, whereas the prevalence of trichuriasis was greatest among teenagers and the prevalence of hookworm increased until the age of 10-15 and then remained high throughout adulthood. In Linger, a village of Han Chinese, located in Puer County, there was an overall geohelminth prevalence of 77% (30%, 60% and 36% for hookworm infection, ascariasis, and trichuriasis, respectively). The differences in prevalence for hookworm and ascariasis were statistically significant. The prevalence of hookworm in Linger increased steadily with age and did not plateau, but there were no discernible patterns of prevalence versus age for either ascariasis or trichuriasis. Heavy trichuriasis infections were noted to occur in Linger. In both villages, more than 98% of the hookworm infections were of light and moderate intensity. Both by morphologic identification of third-stage infective larvae (L3) from eggs as well as identification of adult hookworms recovered from adult residents after treatment with quantrel, Necator americanus was identified as the exclusive hookworm in each village. Geohelminth infections caused by Ascaris, Trichuris and hookworm remain highly endemic to the rural areas of Yunnan Province in southwestern China.

Adolescent↗