The prevalence of Ascariasis

Implications of the prevalence of Ascaris sp. in the funerary context of a Late Antique population (5th-7th c.) in Granada (Spain)

OBJECTIVE

To evaluate the prevalence of gastro-intestinal parasites in human remains from Late Antiquity (5th - 7th c.) Granada (Spain).

MATERIALS

The study included pelvic and cranial control samples from 17 skeletons from the archaeological sites of Los Mondragones (n = 13) and Rafael Guillén (n = 4).

METHODS

In the paleoparasitological study, soil samples from pelvic area and cranium were analyzed using the rehydration, homogenization, and micro-sieving method and visualization under brightfield microscopy.

RESULTS

Ascaris sp. eggs were detected in pelvic samples from seven individuals.

CONCLUSIONS

These findings may indicate that this parasite was endemic. Its detection frequency is one of the highest reported at group level in an osteological series from Late Antiquity.

SIGNIFICANCE

The prevalence of Ascaris sp. associated with skeletal remains has implications for assessing the lifestyle and health of populations in southern Spain during the Late Antique period.

LIMITATIONS

The number of individuals is small and taphonomic processes could have limited paleoparasitological findings SUGGESTIONS FOR FURTHER RESEARCH: Future interdisciplinary studies of this type are warranted in larger osteological series to improve knowledge of parasitosis in the past.

Hepatic and biliary ascariasis

Ascariasis mainly contributes to the global helminthic burden by infesting a large number of children in the tropical countries. Hepato-biliary ascariasis (HBA) is becoming a common entity now than in the past owing to the frequent usage of ultrasonograms and endoscopic diagnostic procedures in the clinical practice. There are a variety of manifestations in HBA and diagnosis depends on a high index of suspicion in endemic areas coupled with subsequent confirmation by sonographic or endoscopic demonstration of the worm. Most of them present with acute abdomen and jaundice. Oriental or recurrent pyogenic cholangiopathy is possibly the result of HBA, commonly encountered in South-East Asian countries. Conservative treatment with anthelminthic agents is used in the majority. Failure to respond to medical therapy usually indicates the need for endoscopic or surgical interventions. Overall, mortality is low and prognosis is good, but many epidemiological and immunological aspects of Ascaris infection are unclear, meaning our understanding the disease and infection still remains incomplete. Therefore, it is difficult to definitely put down a fixed modality of treatment for HBA. This underscores the need for further studies as ascariasis has the potential to adversely affect the national socio-economy by compromising the health of children and adults alike with its sheer number.

Antibodies trap tissue migrating helminth larvae and prevent tissue damage by driving IL-4Rα-independent alternative differentiation of macrophages

Approximately one-third of the world's population suffers from chronic helminth infections with no effective vaccines currently available. Antibodies and alternatively activated macrophages (AAM) form crucial components of protective immunity against challenge infections with intestinal helminths. However, the mechanisms by which antibodies target these large multi-cellular parasites remain obscure. Alternative activation of macrophages during helminth infection has been linked to signaling through the IL-4 receptor alpha chain (IL-4Rα), but the potential effects of antibodies on macrophage differentiation have not been explored. We demonstrate that helminth-specific antibodies induce the rapid trapping of tissue migrating helminth larvae and prevent tissue necrosis following challenge infection with the natural murine parasite Heligmosomoides polygyrus bakeri (Hp). Mice lacking antibodies (J_H^−/−) or activating Fc receptors (FcRγ^−/−) harbored highly motile larvae, developed extensive tissue damage and accumulated less Arginase-1 expressing macrophages around the larvae. Moreover, Hp-specific antibodies induced FcRγ- and complement-dependent adherence of macrophages to larvae in vitro, resulting in complete larval immobilization. Antibodies together with helminth larvae reprogrammed macrophages to express wound-healing associated genes, including Arginase-1, and the Arginase-1 product L-ornithine directly impaired larval motility. Antibody-induced expression of Arginase-1 in vitro and in vivo occurred independently of IL-4Rα signaling. In summary, we present a novel IL-4Rα-independent mechanism of alternative macrophage activation that is antibody-dependent and which both mediates anti-helminth immunity and prevents tissue disruption caused by migrating larvae.

Intestinal helminths present a pressing problem in developing countries with approximately 2 billion people suffering from chronic infection. To date no successful vaccines are available and a detailed mechanistic understanding of anti-helminth immunity is urgently needed to improve strategies for prevention and therapy. Antibodies form a crucial component of protective immunity against challenge infections with intestinal helminths. However, the exact mechanisms by which antibodies target these large multi-cellular parasites have remained obscure. We now demonstrate that helminth-specific antibodies induce the rapid trapping of tissue migrating helminth larvae by activating phagocytes. In the absence of antibodies or their receptors, helminth-infected mice developed extensive tissue damage, revealing a novel role for antibodies in limiting parasite-caused tissue disruption. Furthermore, helminth-specific antibodies reprogrammed macrophages to express wound-healing factors such as the arginine-metabolizing enzyme Arginase-1. Interestingly, the Arginase-1 product L-ornithine directly impaired the motility of helminth larvae. In summary, our study provides detailed mechanistic insights into how antibodies can modulate phagocyte function to provide protection against a large multi-cellular parasite. Our findings suggest that novel anti-helminth vaccines should target the larval surface and activate wound-healing macrophages to provide rapid protection against tissue-disruptive larvae.

Prevalence and epidemiology of intestinal parasitism, as revealed by three distinct techniques in an endemic area in the Brazilian Amazon

This survey aims to estimate the prevalence of intestinal parasitic infections in Santa Isabel do Rio Negro, Amazonian Brazil, through three distinct techniques, correlating the prevalence rates with family income and age groups as well as assessing the household clustering of infections. Prevalence rates were assessed through Graham (n=113), Baermann-Moraes (n=232) and Ritchie (n=463) methods. The Graham method was adopted only for children under 5 years old, 15% of whom were positive for Enterobius vermicularis. By the Baermann-Moraes technique, 5·6% of the samples were positive for Strongyloides stercoralis larvae. The Ritchie technique disclosed the following results: Ascaris lumbricoides (26%), Trichuris trichiura (22·5%), hookworms (9·5%), Entamoeba histolytica/Entamoeba dispar (25·3%), Giardia lamblia (12·5%) and E. vermicularis (0·6%). Children aged 5-14 years presented the highest prevalence for pathogenic parasites. Giardiasis and hookworm infection rates were inversely related to family income. The presence of positive contacts in the same household substantially increased the risk of infection by enteric parasites: odds ratio (OR)=2·70, 95% confidence interval (CI)=1·69-4·29 for ascariasis; OR=2·17, 95% CI=1·34-3·51 for trichuriasis; OR=2·13, 95% CI=1·08-4·17 for hookworm disease; OR=3·42, 95% CI=1·86-6·30 for giardiasis; and OR=2·16, 95% CI=1·35-3·47 for amoebiasis, supporting infection clustering in the home. Intestinal parasitoses are extremely frequent in the studied area, and routine methods for diagnosis may underestimate the prevalence of enterobiasis and strongyloidiasis.

Estimating the global distribution and disease burden of intestinal nematode infections: adding up the numbers--a review

Intestinal nematode infections are among the most common infections of humans in developing countries, but precise estimates of the populations at risk of infection, morbidity and mortality are difficult to derive. Careful evaluation of the global distribution and disease burden of nematodes is essential to determine the cost-effectiveness of control and ensure that control programmes are focused appropriately. In turn, understanding the disease burden depends on a summary measure of health as well as reliable data on risks of infection, morbidity and mortality. This review provides an overview of data sources and methods adopted in the Global Burden of Disease study to estimate the burden of intestinal nematodes, including the empirical and modelling challenges in its estimation. Particular attention is paid to efforts to improve our ability to define at-risk populations, based on a Global Atlas of Helminth Infection, and to better estimate attributable morbidity.

Spatial distribution of enteroparasites among school children from Guarapuava, State of Paraná, Brazil

The most common infections in human beings are caused by intestinal parasites. They can lead to a number of harmful effects, which could include, among others, intestinal obstruction, malnutrition, iron deficiency anemia, diarrhea, and poor absorption. In Brazil, enteroparasites are one of the main public health issues. The present study aims at analyzing the distribution and frequency of enteroparasite occurrence in 635 children from seven community schools in the city of Guarapuava, Paraná (PR). In addition, we used similarity and diversity indices to analyze the parasite community. We found 475 samples with at least one parasite showing that 75.27% of children had enteroparasites. A smaller fraction (26.73%) of children harbored several parasites (multiparasitism), especially Giardia duodenalis (56%), and Ascaris lumbricoides (18%). Statistical analysis showed that three (out of seven) children communities had higher similarity in frequency and amount of parasites. Our results suggest that the children studied were highly infected by enteroparasites. These levels of infestation could be related to several factors, such as climate, social and economic conditions and characteristics of the parasites.

Biliary ascariasis: the value of ultrasound in the diagnosis and management

BACKGROUND

Conventional methods of radiographic examination are often unsatisfactory for identifying worms in the biliary tract. Ultrasonography is a non-invasive, quick and safe procedure known to have diagnostic accuracy. We studied the ultrasonographic appearances of biliary ascariasis and the role of ultrasonography in diagnosis and management.

METHODS

In a prospective 5-year study, a sonographic diagnosis of biliary ascariasis was made on 46 Yemeni patients. The diagnosis was based mainly on sonographic appearances supported by clinical and laboratory results and proved by outcome of either surgical or medical management or spontaneous exit of worms. Follow-up ultrasound was performed for all patients to confirm the diagnosis and to monitor management.

RESULTS

Parasites were present in the dilated main bile duct in 23 patients, in the gallbladder in 12 patients, in the intrahepatic ducts in 6 patients, in the main pancreatic duct in 4 patients and as an intrahepatic abscess in one patient. The characteristic appearance of Ascaris lumbricoides was as single or multiple echogenic non- shadowing linear or curved strips with or without echoic tubular central lines that represent the digestive tracts of the worm. A spaghetti-like appearance was seen in 9 patients and amorphous fragments were seen in 2 patients. Sixteen patients underwent surgery, 20 patients were treated medically (including spontaneous exit of the worm in 7 patients without treatment) and in 10 patients worms were extracted by endoscopic retrograde cholangiopancreatography.

CONCLUSIONS

Follow-up ultrasound was found to be effective in confirming the diagnosis and monitoring management.

Human thelaziosis--a neglected parasitic disease of the eye

The oriental eyeworm, Thelazia callipaeda (Spirurida, Thelaziidae), infects a range of definitive hosts, such as dogs, cats, foxes, rabbits, and humans. This parasite usually lives under the nictitating membrane of the eye, where the adult females release first-stage larvae into the lachrymal secretions; these larvae are subsequently ingested by the intermediate arthropod host within which they develop to the infective, third-stage larvae. The latter larvae are then deposited into the eyes of the definitive host. Recently, T. callipaeda has been reported to infect dogs, foxes, and/or cats in Europe (Italy, France, and Germany). Human thelaziosis (HT) is considered to be an underestimated parasitic disease, whose prevalence appears to have increased in poor socioeconomic settings in many Asian countries, including China. In humans, the disease can be subclinical or symptomatic, exhibiting epiphora, conjunctivitis, keratitis, excessive lachrymation, corneal opacity, and/or ulcers. Knowledge about HT is presently fragmentary and mainly limited to clinical case reports. This article provides a background on the parasite and its life cycle, reviews cases of human thelaziosis, summarizes key aspects regarding the diagnosis of thelaziosis, and proposes future research and methods of control of the disease in humans, particularly in Asia.

Fertilization state of Ascaris suum determined by electrorotation

Electrorotation is a non-invasive technique that is capable of detecting changes in the morphology and physicochemical properties of microorganisms. The first detailed electrorotation study of the egg (ovum) of a parasitic nematode, namely Ascaris suum is described to show that electrorotation can rapidly differentiate between fertilized and non-fertilized eggs. Support for this conclusion is by optical microscopy of egg morphology, and also from modelling of the electrorotational response. Modelling was used to determine differences in the dielectric properties of the unfertilized and fertilized eggs, and also to investigate specific differences in the spectra of fertilized eggs only, potentially reflecting embryogenesis. The potential of electrorotation as an investigative tool is shown, as undamaged eggs can be subjected to further non-destructive and destructive techniques, which could provide further insight into parasite biology and epidemiology.

Endoscopic management of early postoperative biliary ascariasis in patients with biliary tract surgery

Bile leak and residual stones are well known complications of biliary tract surgery. In endemic areas of ascariasis, invasion of the biliary tract by roundworms during the early postoperative period is an infrequent but serious complication. The present study describes the endoscopic management of postoperative biliary ascariasis in 19 consecutive patients. There were 5 men and 14 women with a mean age of 33.3 +/- 6.3 years. All patients had undergone cholecystectomy, with choledocholithotomy and placement of a T-tube in 13 (68.4%) patients. Eight (42.1%) patients including two with T-tubes were acutely sick at referral. Altogether, 16 (84.2%) patients had widened papillae due to previous endoscopic sphincterotomy (3 patients) or recent dilatation of the sphincter of Oddi by Bake's dilators (13 patients). All patients with a T-tube in situ had undergone unsuccessful attempts to remove the worms by flushing saline through the T-tube. Endoscopic retrograde cholangiopancreatography was performed 4 to 16 days after biliary tract surgery and revealed roundworms in the common bile duct in 10 patients, in the hepatic ducts in 2, or in both ducts in 7. Three patients had coexisting biliary leakage: from the cystic duct stump in two and from a T-tube track in one. Endoscopic treatment consisted of extracting the worms from the biliary tree and placing stents in those with coexisting leakage. Endoscopic success was defined as complete worm extraction and resolution of biliary leakage and was achieved in all patients. Complications occurred in one (5.3%) patient. We concluded that endoscopic management is an effective, safe approach for extracting ascarids from the biliary tree during the early postoperative period. It reduces the hospital stay, avoids T-tube-related complications, and permits a postoperative complication to be treated using a nonsurgical method.

Pharmacotherapy of ascariasis

Ascaris lumbricoides, the most frequent human intestinal nematode, is the causative agent of ascariasis, with an estimated worldwide prevalence of over one billion people, especially in moist tropical and subtropical regions, but also in cooler climates. Although characterised with low morbidity and mortality rates, the global prevalence of ascariasis still results in approximately 20,000 deaths annually, primarily as a consequence of intestinal obstruction. In humans, transmission usually occurs by hand-to-mouth route by way of contaminated agricultural products and food, or from dirty hands. Three phases of ascariasis may be present, namely, the pulmonary, intestinal and the complications stage. Although generally asymptomatic, heavy infestation may cause serious pulmonary disease, or partial or complete obstruction of biliary or intestinal tracts. Anthelminthic chemotherapy is required to eradicate the parasites and prevent potentially serious complications. Mebendazole, albendazole and pyrantel pamoate are the most widely used agents to treat ascariasis. Preventive chemotherapy delivered to communities in endemic regions may serve as an affordable and cost-effective strategy to reduce the prevalence and morbidity in endemic regions. Under unusual circumstances, Ascaris suum, the cause of helminthic infection in pigs, may also cause disease in humans.

Vaccination against helminth parasites--the ultimate challenge for vaccinologists?

Helminths are multicellular pathogens which infect vast numbers of human and animal hosts, causing widespread chronic disease and morbidity. Vaccination against these parasites requires more than identification of effective target antigens, because without understanding the immunology of the host-parasite relationship, ineffective immune mechanisms may be invoked, and there is a danger of amplifying immunopathogenic responses. The fundamental features of the immune response to helminths are therefore summarised in the context of vaccines to helminth parasites. The contention between type-1 and type-2 responses is a central issue in helminth infections, which bias the immune system strongly to the type-2 pathway. Evidence from both human and experimental animal infections indicates that both lineages contribute to immunity in differing circumstances, and that a balanced response leads to the most favourable outcome. A diversity of immune mechanisms can be brought to bear on various helminth species, ranging from antibody-independent macrophages, antibody-dependent granulocyte killing, and nonlymphoid actions, particularly in the gut. This diversity is highlighted by analysis of rodent infections, particularly in comparisons of cytokine-depleted and gene-targeted animals. This knowledge of protective mechanisms needs to be combined with a careful choice of parasite antigens for vaccines. Many existing candidates have been selected with host antibodies, rather than T-cell responses, and include a preponderance of highly conserved proteins with similarities to mammalian or invertebrate antigens. Advantage has yet to be taken of parasite genome projects, or of directed searches for novel, parasite-specific antigens and targets expressed only by infective stages and not mature forms which may generate immunopathology. With advances under way in parasite genomics and new vaccine delivery systems offering more rapid assessment and development, there are now excellent opportunities for new antihelminth vaccines.

Intestinal helminth infections among school children in Visakhapatnam

A study was carried out between 1993-1994 to determine the prevalence and intensity of intestinal helminth infections among 217 primary school children in Relliveedhi, a slum area in Visakhapatnam. The children were between 7 to 13 years of age and belonged to lower socio-economic status. Stool samples collected were processed by modified formalin-ethyl acetate sedimentation technique to determine ova counts (EPG). One hundred and seventy seven children were infected with one or more of the intestinal parasites viz. Ascaris lumbricoides, Trichuris trichiura and hookworm. The overall prevalence of infection was eighty two per cent. Ascaris lumbricoides was the most common infection with a prevalence of 75% followed by T. trichiura (66%) and hookworm (9%). All infected children received a single dose of albendazole (400 mg/child). Single stool samples were examined over a period of nine months to study reinfection dynamics.

Characterisation of Ascaris from human and pig hosts by nuclear ribosomal DNA sequences

The sequences of the nuclear ribosomal DNA region spanning the first internal transcribed spacer, the 5.8S rRNA gene and the second internal transcribed spacer were determined for Ascaris samples from pigs and humans from different geographical regions. The sequences of the 5.8S gene and the second internal transcribed spacer were the same for all samples examined, whereas all Ascaris samples from humans had six (1.3%) nucleotide differences in the first internal transcribed spacer compared with those from pigs. These differences provided some support for the existence of separate species of Ascaris or population variation within this genus. Using a nucleotide difference within a site for the restriction enzyme HaeIII, a PCR-linked restriction fragment length polymorphism method was established which allowed the delineation of the Ascaris samples from pigs and humans used herein. Exploiting the sequence differences in the first internal transcribed spacer, a PCR-based single-strand conformation polymorphism method was established for future analysis of the genetic structure of pig and human Ascaris populations in sympatric and allopatric zones.

Biliary ascariasis complicating endoscopic sphincterotomy for choledocholithiasis in India

Endoscopic sphincterotomy is the treatment of choice for patients with choledocholithiasis. Biliary ascariasis has been reported from many parts of the world but is common in Kashmir, India. We report five cases of biliary ascariasis of which four were the result of post-endoscopic sphincterotomy for choledocholithiasis. Therefore, biliary ascariasis is not an uncommon complication of endoscopic sphincterotomy.

The global burden of intestinal nematode infections — Fifty years on

Fifty years after Stoll published his 'This Wormy World' article, the global prevalence of infections with intestinal nematodes remains virtually unchanged. The main species involved are Ascaris lumbricoides, Trichuris trichiura and hookworms, and there are now approximately one billion infections with each of these, worldwide. Given these large numbers, Man-Suen Chan here focuses on attempting to quantify the disease burden caused by these infections, using a recently formulated method of calculating disability-adjusted life years (DALYs). Using a mathematical model, it is estimated that approximately 70% of this burden can be prevented in high-prevalence communities by treating schoolchildren alone. Programmes targeted at schoolchildren have been shown to be extremely cost-effective, and hence this provides a realistic approach for combating these infections in the future.

[Intestinal parasitoses in schoolchildren of Martinésia District, Uberlândia, MG: a pilot study]

This work evaluates the occurrence of intestinal parasites in the students of the Martinésia District, Uberlândia municipality, Minas Gerais state. A total of 103 children were examined, from September to November 1995, according to Lutz or Hoffman, Pons and Janer method. The overall prevalence rate was 22.3% and the highest indices of infection were observed in 8-9 age group (34.8%), in village dwellers (30.0%) and in females (26.9%). Helminthiasis and protozoosis showed similar prevalence rates (10.7% and 12.6%, respectively). Giardia lamblia was the unique protozoan parasite verified and only one case of polyparasitism was found. We concluded that: the prevalence of enteroparasitosis in the studied group is lower than expectations for a rural community, what is, probably, a consequence of the good sanitary conditions presenting in that district.

Structural and functional analysis of a glutathione S-transferase from Ascaris suum

A recombinant glutathione S-transferase (GST) (EC 2.5.1.18) from the parasitic nematode Ascaris suum (AsGST1) displays specific activity with a variety of model substrates and secondary products of lipid peroxidation. The AsGST1 interacts with a range of model inhibitors, haematin-related compounds, bile acids and anthelminthics. The reported variations in biochemical activity correlate with structural differences observed by homology modelling. Here, differences in the topography of the proposed substrate binding site between the AsGST1 and the host GSTs were identified. A rabbit polyclonal antiserum was raised against the glutathione-binding proteins of A. suum and specific antibodies against AsGST1 were affinity-purified using the recombinant protein. These antibodies were used to localize the AsGST1 in adult worms by immunohistochemical staining. The strongest immunostaining for AsGST1 was localized in the intestine in all worms examined. This suggests that the enzyme may be responsible for the metabolism of materials that are incorporated from the environment, as well as for molecules that are excreted or secreted from the parasite to the environment. It also demonstrates the accessibility of the enzyme to an inhibitor or blocking antibody. In addition, the structure and sequence of the gene encoding AsGST1 have been determined. Southern-blot analyses of the AsGST1 gene suggests that it is a single-copy gene. The nucleotide sequence analysis revealed that the gene is composed of four exons and three introns, and potential regulatory elements were identified in the 5' flanking sequence.

Ascariasis

Ascariasis is a helminthic infection of global distribution with more than 1.4 billion persons infected throughout the world. The majority of infections occur in the developing countries of Asia and Latin America. Of 4 million people infected in the United States, a large percentage are immigrants from developing countries. Ascaris-related clinical disease is restricted to subjects with heavy worm load, and an estimated 1.2 to 2 million such cases, with 20,000 deaths, occur in endemic areas per year. More often, recurring moderate infections cause stunting of linear growth, cause reduced cognitive function, and contribute to existing malnutrition in children in endemic areas. Ascaris infection is acquired by the ingestion of the embryonated eggs. The larvae, while passing through the pulmonary migration phase for maturation, cause ascaris pneumonia. Intestinal ascaris is usually detected as an incidental finding. Ascaris-induced intestinal obstruction is a frequent complication in children with heavy worm loads. It can be complicated by intussusception, perforation, and gangrene of the bowel. Acute appendicitis and appendicular perforation can occur as a result of worms entering the appendix. HPA is a frequent cause of biliary and pancreatic disease in endemic areas. It occurs in adult women and can cause biliary colic, acute cholecystitis, acute cholangitis, acute pancreatitis, and hepatic abscess. RPC causing hepatic duct calculi is possibly an aftermath of recurrent biliary invasion in such areas. Ultrasonography can detect worms in the biliary tract and pancreas and is a useful noninvasive technique for diagnosis and follow-up of such patients. ERCP can help diagnose biliary and pancreatic ascariasis, including ascaris in the duodenum. Also, ERCP can be used to extract worms from the biliary and pancreatic ducts when indicated. Pyrantel pomoate, mebendazole, albendazole, and levamisole are effective drugs and can be used for mass therapy to control ascariasis in endemic areas.

Re-assessing the global prevalence and distribution of lymphatic filariasis

This paper estimates the global burden of lymphatic filariasis based on a review of the published literature on infection and disease surveys. A method for aggregating and projecting prevalence data from individual studies to national, regional and global levels, which also facilitates the estimation of gender and age-specific burdens, is presented. The method weights in favour of the larger, and hence presumbably more reliable, studies and relies on estimated empirical relationships between gender, age, infection and disease in order to correct studies with incomplete data. The results presented here suggest that although the overall prevalence of filariasis cases is 2.0% globally (approximately totalling 119 million cases), the disease continues to be of considerable local importance, particularly in India and Sub-Saharan Africa. Estimates by age and gender clearly show that, unlike other helminth infections, filariasis is mainly a disease of the adult and older age-classes and appears to be more prevalent in males. This work suggests that the derivation of more accurate estimates of the burden of filariasis will require a better understanding of both the epidemiology and the spatial aspects of infection and disease. It also suggests that filariasis is preventable based on a geographically targeted strategy for control.

The evaluation of potential global morbidity attributable to intestinal nematode infections

This paper presents a method of estimating the potential global morbidity due to human intestinal nematode infections (Ascaris lumbricoides, Trichuris trichiura and hookworms), based on the observed prevalence of infection. The method relies on the observed relationships between prevalence and intensity of infection, and between worm burden and potential morbidity. This approach is shown to be sensitive to the precision of the original prevalence estimates and, in particular, to the degree of spatial heterogeneity in levels of infection. The estimates presented here indicate that several tens of millions of children are likely to suffer developmental consequences from infection, and suggest that the global disease burden of geohelminthiasis may be significantly greater than was supposed.

Immunoepidemiology of intestinal helminthic infections. 1. The global burden of intestinal nematode disease

Estimates of the world-wide prevalence of intestinal nematode infections indicate that there are more than 1000 million people infected, and several million cases of clinical helminthiases. Recent studies suggest that the morbidity has been underestimated and that moderate intensities of infection may have important developmental consequences, particularly for children of school age.

Metabolism and fate of ecdysteroids in the nematodes Ascaris suum and Parascaris equorum

When injected with [3H]ecdysone and maintained in vitro, the parasitic nematodes, Ascaris suum and Parascaris equorum each produced a series of polar and relatively apolar metabolites. A. suum metabolised the compound into ecdysonoic acid ([3H]EOIC), ecdysone 25-glucoside ([3H]E25gluc), putative ecdysone 22-phosphate ([3H]E22P) and a series of at least six relatively apolar metabolites. All of these, except ecdysonoic acid, were hydrolysed by a crude enzyme preparation from Helix pomatia, releasing ecdysone. In a similar study, P. equorum produced ecdysone 25-glucoside, putative ecdysone 22-phosphate and a series of relatively apolar compounds all of which were hydrolysed by H. pomatia enzymes, releasing ecdysone. [3H]Ecdysone 25-glucoside was the most abundant single metabolite in both species, and in P. equorum, at least, was released into the culture medium in relatively large amounts. Apolar metabolites were present in worm samples and were the major, if not the only radiolabelled compounds detected in eggs of both species. Data indicated a metabolic relationship between some of the apolar conjugates found in both nematode species and ecdysone 25-glucoside.

Reduction in the incidence of biliary and other surgical complications of ascariasis according to the decrease of its national egg prevalence in Korea

While various examples of rationale or benefits of ascariasis control could justify a necessity of control activity in a community, few practical index other than the egg prevalence or intensity of infection has been used to evaluate the efficacy obtained by the control activity. A literature-based retrospective study was undertaken to provide some numerical data on the decreasing morbidity of surgical ascariasis as a consequence of ascariasis control in Korea. A thorough review of literatures (1959-1990) on biliary and other surgical complications of ascariasis reported from general hospitals revealed that their incidence has been decreasing very proportionally to the national figures of its egg prevalence and worm burden. For example, according to the remarkable decreases of the prevalence of ascariasis, there is an evident decreasing tendency of the proportion (%) of biliary ascariasis cases among all biliary surgical patients and the proportion of biliary ascariasis cases among all biliary stone patients in general hospitals. It is highly suggested that the Korean people have been much benefited by the control activity of ascariasis executed at a national scale since 1960s, especially in terms of incidence of biliary and other surgical complications of ascariasis.

Prevalência e intensidade de infecção por Ascaris lumbricoides em amostra populacional urbana (São Paulo, SP)

Pesquisaram-se ovos de Ascaris lumbricoides em amostras fecais de 407 moradores (8,87% do total) de uma favela da cidade de São Paulo. Realizaram-se exames qualitativos (sedimentação por gravidade) e quantitativos (técnica de Kato & Miura adaptada a contagens). Discutem-se aspectos diferenciais da epidemiologia da ascaríase em áreas urbanas e rurais, com base em dados deste estudo e da literatura. Salienta-se a importância, em epidemiologia, da quantificação de exames de fezes.

Epidemiology and control of ascariasis in Korea

In view of the epidemiology and control strategy, ascariasis was reviewed with special reference to the data obtained for the past years in Korea. The range of length and prepatent period of A. lumbricoides to become fertile were 12.5-13.5 cm and 1.8-2.1 months for females, and 10.5-11.5 cm and 2.1-2.5 months for males, respectively. In the female worm burden 1 per case, the egglaying capacity steadily increased from 12.6 cm of their length up to 25.0 cm and then decreased significantly after their growth to 27.5 cm. Analysed the egg discharging pattern, it was turned out that the cases with six or more worms have no probability to be false negative or unfertilized ova passer, and 52% of all false negatives were found infected only with male(s). The sex ratio was in the range of 0.74-0.82 (male/female). Basic reproductive rate was calculated in the range of 1.16-2.11 in rural areas, but it was approaching nearly to the 'break point' in some areas. It was observed that the 'U-rate' was increased from 19.4% (1973) to 61.1% (1989) for the past seventeen years. According to the survey in 6 rural areas, the average worm burden was 2.2 per population and 4.5 per infected. The frequency distribution pattern of A. lumbricoides per person in a rural community was well fitted to the negative binomial distribution. Seasonal fluctuation was shown in two, smaller and larger, peaks. The annual prevalence in student group was initially 55.4% in 1969, but decreased to 0.3% in 1989, and it is evident that the decrease has been greatly owing to the national control project. It was proved that the efficacy of a quarter dose of pyrantel pamoate used in long term control programme was almost equal to that of conventional dose (10 mg/kg). The comparatie efficacy of various interval mass chemotherapy schemes was evaluated through 2 year observations, and it was confirmed that at least biannual mass chemotherapy is necessitated to expect gradual lowering of reinfection. In the case of blanket treatments with 2-month interval in a village, all of inhabitants have been free from reinfection for the period of 28 months after the initial treatment. It was fully recognized that without specific legislation and organization supported by the government, the national mass control programme has almost no chance of success, especially in developing countries.(ABSTRACT TRUNCATED AT 400 WORDS)