Laboratory diagnosis of schistosomiasis and Katayama syndrome in returning travellers.

The gold standard for laboratory diagnosis of schistosomiasis is the presence of typical eggs in stool or urine. The laboratory diagnosis of schistosomiasis and Katayama syndrome in returning travellers is difficult because the number of excreted eggs is often very limited. In early infections and in patients with only a few contacts with contaminated water, the total number of parasites, migrating larvae or schistosomulae, and adult worms, is very low. Eggs can only be found in faeces or urine when there is at least one pair of adult worms at the final location. The number of parasites increases as a function of the number of contacts with infected water. The exact latency between contamination and egg production is unknown. It is estimated that excretion of eggs starts after 40-50 days. The specific diagnosis of early schistosomiasis and Katayama fever relies essentially on serologic tests or preferably on PCR (if available). These assays are much more sensitive (up to four times) in the early phase of schistosomiasis than microscopic examination for typical eggs. Eosinophilia (sometimes exceeding 50%) is often present in patients with acute schistosomiasis (Katayama fever), but may be limited or absent in late fibrotic manifestations of the disease.

[Schistosomiasis due to Schistosoma intercalatum and urbanization in central Africa]. / Schistosomose due à Schistosoma intercalatum et urbanisation en Afrique centrale.

The species name of Schistosoma intercalatum, Fischer 1934 is linked to the shape and the size of his eggs, which are intermediate between those of S. haematobium and S. bovis. S. intercalatum is the instrument of an intestinal form of schistosomiasis looking like the form induced by S. mansoni but characterized by a low location of the lesions, mainly situated at the rectum and sigmoid level. The spreading area of S. intercalatum is bound to Central Africa. The foci are often urban and of a size limited to a town district. Bulinus forskalii is the intermediate host mostly involved in transmitting S. intercalatum lower Guinea strain, which is the strain found in the largest number of foci. B. crystallinus too transmits the parasite in the area of Gamba in Gabon. The Central Basin congolese strain of S. intercalatum is transmitted by Bulinus globosus. The houses where inhabitants are voiding eggs of S. intercalatum are just in front of the river bank or stream which are snails'breeding places. S. intercalatum is expending at the present time because of the development of built-up areas which are characterized by a disorganized town-planning. The disease is due to the high faecal pollution of the environment, causing a contamination of the urban hydrographic network which is the setting of schistosomiasis transmission. Although primely linked to the forest area, S. intercalatum is spreading with deforestation. Coming from the savannah area, S. haematobium is now invading the forest area, entering into competition with S. intercalatum. But since Bulinus acting as intermediate hosts of S. haematobium are more heliophilous than Bulinus transmitting S. intercalatum, urinary schistosomiasis has a tendency to supplant recto-sigmoidal schistosomiasis, especially in foci where hybridization between the two species of schistosomes is occurring.

[S. mansoni intestinal schistosomiasis]. / Bilharziose intestinale à S. mansoni.

EPIDEMIOLOGICAL DATA: Caused by Schistosoma mansoni, intestinal bilharziasis is endemic in west central Africa, the Arabic peninsula, the Caribbean Islands and the Atlantic cost of South America. Young adults emit large quantities of eggs in stools. CLINICALLY: The adult stage of Schistosoma mansoni lives in the mesenteric veins draining the colon. Its eggs are deposited in the submucosal veinules then pass into the intestinal lumen. Patients eliminating eggs massively experience abdominal pain and diarrhea with stools containing blood and mucus. Hepatomegalia develops, often with splenomegalia. Signs of portal hypertension, collateral circulation and ascitis are observed in highly endemic areas. Other less typical signs of digestive disorders such as anorexia, vomiting, or nausea, have also been reported.

[Urinary schistosomiasis]. / Bilharziose urinaire.

EPIDEMIOLOGICAL DATA: The most frequently encountered human bilharziasis, urinary Schistosoma haematobium schistosomiasis, is endemic in Africa and western Asia: 51 countries are concerned. Humans are infected by contact with water harboring snails of the genus Bulinus that emit furcocercous cercariae. Older children eliminate large quantities of schistosoma eggs in urine. CLINICALLY: Schistosoma haematobium lives in the adult form in the bladder plexus, emitting eggs into the urine. Hematuria and signs of upper urinary tract dilatation are the most frequent clinical manifestations. There has been no data substantiating a higher incidence of urinary tract infections or urinary stones in S. haematobium infested subjects. Schistosomiasis alone does not appear to play a major role in infertility. Inversely, clinical and pathology studies do persistently demonstrate an epidemiological association between urinary schistosomiasis and bladder cancer.

[Other forms of schistosomiasis]. / Autres bilharzioses.

SCHISTOSOMA INTERCALATUM: Endemic in central Africa, S. intercalatum is the causal agent of this intestinal bilharziasis, which is similar to Mansoni's disease but with a characteristic lower localization (rectum and sigmoid). The principal clinical signs are digestive disorders: abdominal pain, diarrhea or dysentery, straining, tenesmus, rectal bleeding. The moderately enlarged liver is smooth and hard but not painful, especially observed in adolescents. ORIENTAL BILHARZIASIS: Schistosoma japonicum (found in lakes in China, Thailand, Philippines, Indonesia) and Schistosoma mekongi (Melong valley) are the principal agents. Both lead to major liver fibrosis producing severe portal hypertension and growth retardation in children.

[Schistosomiasis: diagnosis and treatment]. / Diagnostic et traitement.

LABORATORY DIAGNOSIS: Eggs from Schistosoma haematobium can be found in large quantities in end-miction urine. Their elimination is favored by forced urination. Large quantities of S. mansoni, S. intercalatum, S. japonicum, and S. mekongi can be found on the surface of stools and in mucus and bloody fecal matter. Eggs from S. haematobium are exceptionally found in stools and may be identified in rectosigmoid biopsy samples. Immunological reactions can also be used to identify the species. THERAPY: Praziquantel, the drug of choice, is active against all schistosomal species. Oxamniquine is only active against S. mansoni and is not used outside Latin America. Molluscicidal agents have provided interesting results. Sanitary measures and education are essential therapeutic tools while waiting for a hypothetical vaccine.

[Reactive hypereosinophilia in parasitic diseases]. / Hyperéosinophilies réactionnelles des parasitoses.

Hypereosinophilia is often linked to the presence of pluricellular parasites in host tissues. Polynuclear eosinophils are sprung from the bone marrow. After multiplying and maturing, they are thrown into the blood flow and from the blood to the tissues where they are found in immediate contact with the parasite. Eosinophils are major components of the parasitic granuloma. Parasitic diseases are a major cause of hypereosinophilia and eosinophilia is mainly due to helminths. Protozoa do not produce hypereosinophilia, except for toxoplasmosis in which a low and discontinuous eosinophilia may be seen. Subsequently, maggots producing myiasis yield to hypereosinophilia too. In helminthiasis, the action of the eosinophil granulocyte is double. In tissues, it destroys the parasite and plays a regulatory role in mastocytes degranulation. Eosinophils which participate in the inflammatory reaction secrete factors which neutralize mediators liberated by mastocytes, histamine mainly, destroyed by histaminase. In a practical point of view, blood hypereosinophilia is a very useful tool for diagnosis. Eosinophilia reach early a high value, this before the parasitic infection becomes detectable by means of resources other than immunological. The eosinophils rates decreases rapidly as an effect of the anthelmintic drug, this confirming the efficacy and specificity of the prescribed treatment.

[Epidemiology of certain endemic parasitic diseases in the town of Guadalupe (Republic of Sao Tome and Principe). II. Other endemic parasitic diseases]. / Epidémiologie de certaines endémies parasitaires dans la ville de Guadalupe (République de Saõ Tomé et Príncipe). II. Autres endémies parasitaires.

Stool, blood and urine specimens have been collected from 380 inhabitants of all age groups living in the small town of Guadalupe in May 1992. The seroprevalence of Falciparum malaria (96%), toxoplasmosis (73.3%), have been measured.

[Epidemiology of certain endemic parasitic diseases in the town of Guadalupe (Republic of Sao Tome and Principe) I. Schistosomiasis intercalatum and intestinal worms]. / Epidémiologie de certaines endémies parasitaires dans la ville de Guadalupe (République de Saõ Tomé et Príncipe). I. Schistosomose à S. intercalatum et verminoses intestinales.

Schistosomiasis intercalatum in known to exist in Saõ Tomé since 1988, (Corachan et al.). It is transmitted by Bulinus forskalii, (Brown et al., 1989). Stool, blood and urine specimens have been collected from 380 inhabitants of all age groups living in the small town of Guadalupe close to the Agua Traz river and Agua Polino. The prevalence of schistosomiasis by detection of S. intercalatum eggs in a 10 mg stool thick smear (Kato technique) is 25.5%. An excreted Schistosoma polysaccharide antigen, detected by means of a monoclonal antibody (Ripert et al., 1992), is found in 49.1% of the urine samples. Patients voiding S. intercalatum eggs in stools have been treated with praziquantel (40 mg/kg body weight), as recommended by WHO Expert Committee on Schistosomiasis, but it might be wise to also treat persons excreting antigen in urine. The prevalence of intestinal helminthiasis, ascariasis (73.7%), trichuriasis (73.7%) and necatoriasis have been measured.

[Malaria indices, larval ecology and trophic activity of Anopheles mosquitoes in Djohong (Adamaoua, Cameroon) in the rainy season]. / Indices paludométriques, écologie larvaire et activité trophique des anophèles à Djohong (Adamaoua, Cameroun) en saison des pluies.

In Djohong in the wet season the prevalence of malaria is 17.5% for Plasmodium falciparum and 1.1% for Plasmodium malariae. In children 2 to 9 years of age the plasmodic index is 38.6% (mesoendemicity) for the children of the peasants and 9.4% for those belonging to other socioeconomical groups. In infants less than 12 months old, the plasmodic index is 9.3%, this relatively high rate corresponding to the high transmission period of the rainy season. Anopheles gambiae is the mosquito species most often found in the area (2/3 of the mosquitoes caught in the houses). The breeding sites in he surrounding of the houses are rainwater holes linked to human activity. At a larger distance from the houses, in the valley, the breeding sites are water holes borrowed for the retting of cassava tubercle or natural rock pools found in the basaltic shores of the Mbere river. The trophic activity of Anopheles gambiae and Anopheles funestus is high between 0 and 4 hours a.m. In October the mean number of anopheline mosquitoes bites per night per inhabitant is 33 inside the houses and 7 outside.

Etude epidemiologique de l'onchocercose dans la vallee de la Bini (Adamaoua) Cameroun : prevalence de l'infestation et charge parasitaire

L'Enquete epidemiologique effectuee dans la vallee de la Bini montre que l'onchocercose touche l'ensemble de la population urbaine. Les resultats obtenus dans les villages sont sensiblement identiques. On note en effet que la prevalence parasitaire est de 57;3pour les hommes et de 50;3pour les femmes. Cette difference entre les sexes est encore accentuee par le calcul du nombre moyen de microfilaires par biopsie entamee. Celui-ci est de 55 pour les hommes et de 22 pour les femmes

Etude epidemiologique de l'onchocercose dans la Vallee de la Bini (Adamaoua); Cameroun: pouvoir pathogene de la souche locale d'o. volvulus: atteintes oculaires et cutanees

A N'dena; dans la Vallee de la Bini (Ademaoua) ou la prevalence de l'onchocercose est de 51;4 pour cent d'apres la microfilarodermie; l'importance des atteintes cutanees et oculaires est mesuree. La depigmentation et l'atrophie cutanees s'observent chez 33;1 pour cent des habitants. Et 20;3 pour cent d'entre eux sont porteurs de kystes onchocerquiens. Des microfilaires sont vues dans le segment anterieur de l'oeil chez 23;3 pour cent des sujets et dans la chambre posterieure chez 9;8 pour cent. L'etude du pouvoir pathogene de la souche forestiere locale d'o. volvulus isolee met en evidence un contraste entre; d'une part; une infestation onchocerquienne massive et; d'autre part; la faible repercussion de cette pathologie sur la sante des populations

An epidemiological study of a Schistosoma intercalatum focus in south-east Gabon.

A Schistosoma intercalatum focus in south-east Gabon was studied between July 1989 and July 1990. Among the 356 permanent residents in the village, 354 provided stool specimens and 101 (28.5%) were excreting eggs (geometric mean of egg density = 101.4 eggs/g, with a range of 1-3200). The pattern of prevalence and intensity of infection with age showed the curve usually found in schistosomiasis, i.e. increasing during the first 2 decades of life and then gradually decreasing. The analysis by stepwise logistic regression of factors shown to be important in determining infection in other schistosomiasis clearly demonstrated the significant and independent effects of both age and water contact on infection by S. intercalatum. These similarities with other schistosomal infections could indicate that similar immune mechanisms were operating. Urine from 284 subjects, of whom 90 were egg excreters, was tested for circulating antigen by enzyme-linked immunosorbent assay using a Schistosoma genus-specific monoclonal antibody (Sm 10.27.12). The test was positive for 90 subjects but only 35 of these were egg excreters. Although S. intercalatum is usually considered of low pathogenicity in man, this study showed a relationship between egg excretion and both splenomegaly and lower haemoglobin levels, even after taking into account the confounding presence of Plasmodium falciparum.

Etude epidemiologique du foyer de bilharziose a schistosoma intercalatum de Bata (Guinee Equatoriale)

Un antigene polysaccharidique caracteristique du genre schistosoma excrete dans l'urine est mis en evidence; avant et apres traitement par le praziquantel (40 mg/kg) dans la ville de Bata; ou un foyer de bilharziose a schistosoma intercalatum a ete identifie. Le test de detection urinaire de l'antigene met en jeu un anticorps monoclonal et fait appel a la technique d'inhibition de l'hemagglutination passive. Parmi les 779 sujets examines 145; soit 18;6 pour cent d'entre eux eliminent des oeufs de schistosoma intercalatum dans leurs selles et 305; soit 39;1 pour cent excretent de l'antigene dans les urines; ce qui dans la bilharziose traduit l'existence d'une profonde impregnation antigenique de l'organisme

Aspects epidemiologiques du paludisme dans la ville de Kumba (Cameroun-Province du Sud Ouest)

L'enquete paludometrique effectuee en fin de saison des pluies en octobre 1987 a Kumba; ville du Sud Ouest du Cameroun; a partir d'un echantillon de 804 sujets etabli montre la frequence des acces febriles et des automedications inadequates pratiquees. Elle apprecie le retentissement du paludisme sur la morbidite et la mortalite dans cette region forestiere. Plasmodium falciparum est l'hematozoaire le plus frequent; present sur 26;1 pour cent des lames examinees et responsable de 97;7 pour cent des infestations

Enquete paludometrique dans trois villages de la vallee de la Kadei; Cameroun

L'enquete paludometrique menee en janvier 1991 dans trois villages riverains de la riviere Kadei a l'Est du Cameroun revele un paludisme hyperendemique. L'indice plasmodique des enfants de 2 a 9 ans est de 63;5 pour cent. La formule parasitaire montre la preponderance de plasmodium falciparum et la presence de plasmodium malariae et de plasmodium ovale. La reaction d'immunofluorescence met en evidence un indice serologique eleve et une acquisition precoce des anticorps antipalustres; reflets d'une transmission intense. La pression medicamenteuse est restee tres faible dans la population traditionnelle et la construction d'un barrage ne devrait pas modifier la morbidite palustre en raison d'une transmission deja tres intense dans la region

Etude epidemiologique des filarioses (onchocercose; loase; mansonellose); dans la vallee de la Kadei (Cameroun)

L'etude des filarioses est realisee dans trois villages proche du site prevu pour la construction d'un barrage sur la riviere Kadei (Cameroun oriental). La presence des microfilaires d'onchocerca volvulus est determinee par l'examen des biopsies cutanees. La prevalence parasitologique (37;9 pour cent) et les caracteristiques lesionnelles observees indiquent que l'onchocercose sevit dans la region au niveau de mesoendemie et se presente un facies de foret. Compte tenu de l'ecologie des vecteurs; cette etude d'impact montre que le barrage prevu ne devrait pas modifier d'une facon notable l'ecologie regionale et la transmission des filarioses dans la region