Host finding of the pigeon tick Argas reflexus.

The medically and veterinary important feral pigeon tick Argas reflexus (Ixodida: Argasidae) Fabricius usually feeds on pigeons, but if its natural hosts are not available, it also enters dwellings to bite humans that can possibly react with severe allergic reactions. Argas reflexus is ecologically extremely successful as a result of some outstanding morphological, physiological, and ethological features. Yet, it is still unknown how the pigeon tick finds its hosts. Here, different host stimuli such as living nestlings as well as begging calls, body heat, smell, host breath and tick faeces, were tested under controlled laboratory conditions. Of all stimuli tested, only heat played a role in host-finding. The heat stimulus was then tested under natural conditions within a pigeon loft. The results showed that A. reflexus is able to find a host over short distances of only a few centimetres. Furthermore, it finds its host by random movements and recognizes a host only right before direct contact is made. The findings are useful for the control of A. reflexus in infested apartments, both to diagnose an infestation and to perform a success monitoring after disinfestation.

Strongyloides stercoralis larvae excretion patterns before and after treatment.

The variability of larval excretion impedes the parasitological diagnosis of Strongyloides stercoralis in infected individuals. We assessed the number of larvae excreted per gram (LPG) stool in 219 samples from 38 infected individuals over 7 consecutive days before and in 470 samples from 44 persons for 21 consecutive days after ivermectin treatment (200 µg kg-1 BW). The diagnostic sensitivity of a single stool sample was about 75% for individuals with low-intensity infections (⩽1 LPG) and increased to 95% for those with high-intensity infections (⩾10 LPG). Doubling the number of samples examined per person increased sensitivity to more than 95%, even for low-intensity infections. There was no indication of a cyclic excretion of larvae. After treatment, all individuals stopped excreting larvae within 3 days. Larvae were not detected during any of the following 18 days (total 388 Baermann and 388 Koga Agar tests). Two stool samples, collected on consecutive days, are recommended in settings where low or heterogeneous infection intensities are likely. In this way, taking into account the possible biological variability in excretion, the efficacy of ivermectin treatment can be assessed as soon as 4 days after treatment.

Activity of tribendimidine and praziquantel combination therapy against the liver fluke Opisthorchis viverrini in vitro and in vivo.

Opisthorchiasis, caused by the liver fluke Opisthorchis viverrini, a food-borne trematode, is an important public health problem; however, only a single drug, praziquantel is available. We investigated tribendimidine-praziquantel combinations against O. viverrini in vitro and in vivo. The IC50 values of 0.16 µg/ml and 0.05 µg/ml were determined for praziquantel and tribendimidine, respectively, against adult O. viverrini in vitro. When O. viverrini was exposed to both drugs simultaneously (using a drug ratio based on the IC50 (1:3.2)) a synergistic effect was calculated (combination index (CI) at the IC50= 0.7). A similar result was observed when drug addition in vitro was spaced by the respective half-lives of the drugs (a CI of 0.78 at the IC50 for tribendimidine followed by praziquantel and a CI of 0.47 at the IC50 for praziquantel followed by tribendimidine). In vivo median-effect dose (ED50) values of 191 mg/kg and 147 mg/kg were calculated for praziquantel and tribendimidine, respectively. Low to moderate worm burden reductions (38-62%) were observed in O. viverrini infected hamsters when both drugs were administered simultaneously or on subsequent days, pointing to antagonistic effects in vivo. Further studies are necessary to understand the striking differences between the in vitro and in vivo observations using combinations of praziquantel and tribendimidine on O. viverrini.

Identification of the human paragonimiasis causative agent in Lao People's Democratic Republic.

To assess the species of human paragonimiasis in Lao People's Democratic Republic, 6 ovum samples from 6 native confirmed paragonimiasis patients were examined with polymerase chain reaction (PCR) amplifying the internal transcribed spacer 2 (ITS2). The PCR products were sequenced, and a homology search was performed using the GenBank. All 6 sequences were identical with Paragonimus heterotremus ITS2. Our work suggests that P. heterotremus may be the main etiological agent of human paragonimiasis in this locality.

Liver morbidity due to Schistosoma mekongi in Cambodia after seven rounds of mass drug administration.

Severe liver disease due to Schistosoma mekongi was frequent in northern Cambodia. Between 1995 and 2002, seven rounds of mass chemotherapy (praziquantel) reduced infection from 50% to below 3%. In 2002, we assessed hepatosplenic morbidity by historical, clinical and ultrasonographic investigations in adults (older than 14 years) from endemic (n=342) and non-endemic (n=103) areas (Kratie province). Clinical hepatomegaly (25 vs. 0%), splenomegaly (55 vs. 0%), reported blood in stool (41 vs. 20%) and abdominal pain (78 vs. 57%) were significantly higher in the endemic area. In this area, significantly more subjects reported a family history of death due to schistosomiasis (12 vs. 0%); 63% (vs. 0%) reported having at least three treatments of praziquantel in previous years; and only 11% (vs. 99%) had normal liver ultrasonographic examination. Periportal fibrosis with portal hypertension was diagnosed in 46% (vs. 0%) of people in this area; 18% (vs. 0%) and 5% (vs. 0%) of portal hypertension was classified as moderate and severe, respectively. People aged between 24 and 35 years were mostly affected. There was no gender difference. The pathology in the endemic district is most probably residual morbidity of S. mekongi infections. Contributions of co-infections (hepatitis) cannot be excluded. Careful monitoring of the affected communities is required.

Control of Schistosoma mekongi in Cambodia: results of eight years of control activities in the two endemic provinces.

In Cambodia, schistosomiasis is transmitted in the provinces of Kratie and Stung Treng where approximately 80000 individuals are estimated to be at risk of infection. The baseline prevalence of infection was estimated to be between 73% and 88%, and cases of severe morbidity (hepatosplenomegaly, puberty retardation) and mortality were very common. In 1994, the Ministry of Health of Cambodia started schistosomiasis control applying universal chemotherapy with praziquantel (40mg/kg). The coverage of the programme was between 62% and 86% for 8 years. This simple control measure resulted in the control of the disease: no cases were reported in 2004 and only three cases were reported in 2005. In addition, there are no longer reports of cases of severe morbidity due to schistosomiasis. Since the beginning of the control programme, a single dose of mebendazole (500mg) has been combined with praziquantel during the mass chemotherapy; as a result the prevalence of Ascaris lumbricoides and hookworms dropped from 74.5% to 10% and from 86% to 40% respectively. The experience in Cambodia demonstrates that, with political commitment, control of parasitic diseases is achievable even in a situation of minimal resources. The programme represents a successful model for other developing countries.

Paragonimiasis and its intermediate hosts in a transmission focus in Lao People's Democratic Republic.

Human cases of paragonimiasis have been reported in Lao People's Democratic Republic from several provinces, however, detailed descriptions of a focus of transmission including parasites species and intermediate hosts are lacking. Field investigations were carried out between February and July 2004 in three neighboring villages of the province of Vientiane. Persons with chronic cough (more than three weeks) were identified during a door-to-door survey and three sputum samples were examined for Paragonimus spp. and tuberculosis on two consecutive days. Potential intermediate snail and crustacean hosts were sampled among the populations' water-contact sites and examined for metacercarial infections or cercarial shedding. Four dogs were infected with metacercaria and the species of the subsequently retrieved adult parasites were identified. 12.7% (15 cases) of all chronic cough patients (0.6% of the total population) suffered from paragonimiasis. Samples of five species of freshwater snails, two species of crabs and one species of prawn were collected from the Nam Sêt River. None of the snails were infected. Metacercariae of P. harinasutai, P. bangkokensis and P. heterotremus were found in Potamon lipkei crabs while an infection with P. westermani was observed in a Chulathelphusa brandti crab. No paragonimid metacercaria was found in the Macrobrachium dienbienphuense prawns Dang and Nguyen 1972. This study demonstrates the importance of Paragonimus spp. as an etiological agent in patients with chronic cough and suggests that similar transmission might be widespread in Lao People's Democratic Republic. We document herein the transmission of several Paragonimus species indicating that paragonimiasis is an active zoonosis in Lao People's Democratic Republic.

[Animal and human Cryptosporidiosis in rural zone in Vietnam (Cu Chi district, Ho-Chi-Minh-City)]. / Cryptosporidiose animale et humaine en zone rurale au Vietnam (district de Cu Chi, Hô-Chi-Minh-ville).

A pilot study was carried out in May-June 2003 to evaluate the epidemiological situation of cryptosporidiosis in the Cu Chi district, a rural zone of Ho-Chi-Minh City Vietnam. The modified acid-fast stain of the stools revealed that 10/202 (5%) cows, 1/29 (3.5%) cattle breeders, and 2/53 (3.8%) under five year- old children with diarrhoea were infected by this germ. Unconfined cattle had a significantly higher risk of infection than penned animals (odds ratio [OR]: 8.3; 95% confidence interval [CI]: 1.06-64.7; p: 0.025).

[Anaemia in a school of rural Cambodia: detection, prevalence, and links with intestinal worms and malnutrition]. / Anémie dans une école du Cambodge rural: détection, prévalence et liens avec les parasitoses intestinales et la malnutrition.

According to WHO, half of the world's children suffers from anaemia, which is a silent and neglected endemic resulting from three major causes: iron deficiency intestinal worms and malaria. A two month transversal study was conducted in a rural primary school in Battambang Province, Cambodia, in a malaria-free area. The main objective of the study was to assess the prevalence of anaemia and two of its possible driving factors, intestinal parasites and general malnutrition; a secondary objective was to assess the accuracy of haemoglobin colour scale, an easy and cheap visual technique compared to spectrophotometry used as the reference. Among 168 school children (average age: 11), the prevalence rates of moderate and severe anaemia were 24% and nil respectively; average haemoglobin was 12.6 g/dl. These results compared favourably with previous data from Cambodia. In our study's conditions, the haemoglobin colour scale grossly overestimated the anaemia prevalence: 83 vs. 24%, specificity 22%. Despite its simplicity and very low cost, this technique appeared inaccurate. Anaemia was independently associated with Ancylostoma carriage (p = 0.05), and stunting (p = 0.01), which prevalences were 54% et 40% respectively; and this, despite a mebendazole 500 mg dose given 9 months prior to the study as part of a regular deworming school program. Although periodical mass deworming in schools does not prevent early Ancylostoma reinfection, it may reduce the severity of anaemia. It therefore appears fully justified, and may be strengthened, notably by switching from mebendazole to albendazole.

The WHO dose pole for the administration of praziquantel is also accurate in non-African populations.

In 2001, WHO developed a pole for the administration of praziquantel without the use of weighing scales, with encouraging results in African populations. In the present study, the pole was tested on height/weight data from 9354 individuals from 11 non-African countries. In more than 98% of the individuals (95% CI 97.8-98.4) the pole estimated an acceptable dosage (30-60 mg/kg), a performance statistically similar to that observed in African populations. Reproducing the present pole in the form of a strip of paper and including it in each container of praziquantel would greatly facilitate the administration of the drug in large-scale interventions.

[Pleuro-pulmonary paragonimiasis]. / La paragonimose pleuropulmonaire.

Paragonimiasis is a food borne zoonosis due to a trematode belonging to the genus Paragonimus. Although present throughout the world, about 90% of the cases occur in Asia where around 20 million people are infected. The parasitic cycle is complex with two different intermediate hosts. Man is infected by ingesting the raw or undercooked flesh of the second host - a freshwater crab or prawn - or possibly of a paratenic mammal host (wild boar), which contains the infective larval stage metacercariae that reaches the lung which is the main target organ. Epidemiological, pathological, and clinical aspects are reviewed. The main symptoms are protracted cough, and recurrent "benign" hemoptysis. Abnormal pleuro-pulmonary imaging features are constant, but protean and non-specific, leading to frequent confusion with tuberculosis. Diagnosis is easily achieved by ova search in the sputum or pleural fluid, or by serology. Evolution is usually considered benign, although not well known. Finally, praziquantel is the effective first choice treatment. Some paradoxical aspects of this disease are underlined such as: underdiagnosis despite a very simple diagnostic procedure, or opposite tendencies according to location, either extinction or re-emergence.

The use of morbidity questionnaires to identify communities with high prevalences of schistosome or geohelminth infections in Tanzania.

Parasitic infections were investigated in Morogoro Rural District, Tanzania, between October 1992 and June 1993. A total of 4589 schoolchildren (aged 7-17 years) from 30 primary schools was screened for infection with Ascaris lumbricoides, Trichuris trichiura, hookworms (3456 children only), Schistosoma mansoni and S. haematobium. The children were also asked about their recent experiences of the following: diarrhoea, abdominal pain, blood in stool, perception of suffering from schistosomiasis, and worm infection and examined for spleen and liver enlargement. Among schools, there were correlations between the prevalence of S. mansoni infection and bloody stools, spleen enlargement and liver enlargement, and between S. haematobium infection and the presence of blood in urine. To exclude ecological explanations for the correlations, logistic regression was used to estimate the adjusted odds ratio (OR) for each infection and each sign or symptom. No sign or symptom was significantly associated with any geohelminth infection. Reported blood in stool was significantly associated with S. mansoni infection (OR = 1.62, P = 0.045). Reported blood in urine was significantly associated with S. haematobium infection (OR = 7.71, P < 0.001), as was reported blood in stool (OR = 11.52, P < 0.001), indicating that presence of blood in either form of excreta was related to the local term for schistosomiasis. These results support the possibility of using reported blood in stool as a means of rapid assessment for identifying communities with a high prevalence of S. mansoni infection.

Epidemiology and control of mekongi schistosomiasis.

Since the first case of Schistosoma mekongi infection was reported in 1957, control measures have been implemented in Laos and in Cambodia. Operational research provided the necessary information on parasite epidemiology and the associated morbidity in order to develop adequate control measures. S. mekongi transmission occurs in rocky banks of the river according to a seasonal cycle. Common daily activities of villagers living in the endemic areas constitute the risk factors for infection. The potential role of an animal reservoir is not fully understood. Severe disease is associated with advanced infection status. Signs and symptoms of portal hypertension dominate the clinical situation, and death is usually due to bleeding from ruptured esophageal varices. Schistosomiasis control in both Laos and Cambodia was based on universal treatment campaigns and resulted in a dramatic fall in the prevalence of the infection and in morbidity control. However, even if the disease and the infection have been satisfactorily controlled, transmission still occurs, and in very limited areas the prevalence reaches rates of more than 15%. Today, 60000 people are estimated to be still at risk of infection in Laos and about 80,000 in Cambodia. The new challenge in schistosomiasis control in endemic areas along the Mekong river is to consolidate the results, to establish a sensitive and reliable surveillance system, and finally to adapt control strategies to the low endemic situation. The impoverished nature of the region makes the possibility of sanitation unfeasible, and external support is still needed to sustain activities in the near future and to enable the substantial reduction of risk behaviors.

[The role of common starlings (Sturnus vulgaris) in the epidemiology of bacterial, potentially human pathogenic, disease agents]. / Die Rolle des Gemeinen Stars (Sturnus vulgaris) in der Epidemiologie bakterieller, potentiell humanpathogener Krankheitserreger.

Since a long time a public garden in Basel is known as a site for overnight accommodation and assembly of starlings. The birds cause an immense faecal contamination of the park and the neighbouring district. A nursery and a primary school are directly affected. To evaluate the health risk coming from the starlings droppings for the population, particularly for the children and to assess the role of starlings in the transmission of diseases to humans and in the epidemiology of human diseases the presence of human bacterial pathogens in the faeces of starlings was determined. Some of the isolated strains were further typed and compared to strains of human origin. C. jejuni, L. monocytogenes and C. psittaci were most often found. The typing of some C. jejuni and L. monocytogenes isolates showed a great variety of geno-, sero- respectively phage types that did not belong to the strains most often found in isolates of human origin. Starlings can harbour human pathogens and therefore a potential risk of infection comes from their droppings. It seems however rather improbable, that these birds present a constant direct source of infection for human beings.

[Diarrhea in urban agricultural workers in Nouakchott in Mauritania]. / La diarrhée chez les agriculteurs urbains de Nouakchott en Mauritanie.

Nearly 200 million people in the developing world are dependent or urban gardening for food and income. This practice has been accelerated by the droughts of recent decades which have forced more and more migrants into urban areas. Numerous potential health hazards have been attributed to urban gardening but the exact risks in Sahelian areas remain unclear. The purpose of this cross-sectional study was to evaluate the incidence of diarrhea at the Tel Zatar gardening site in urban Nouakchott, Mauritania. In addition, a case-control study was carried out to identify risk factors for diarrhea in function of gardeners' activity and living conditions. Statistical analysis was performed using univariate and logistical regression methods. The annual incidence of diarrhea ranged from 6.9 (IC95 p. 100 = 5.0-8.8) to 8.5 (IC95 p. 100 = 6.2-10.8) episodes per gardener and year. Multivariate analysis identified four significant risk factors. Two of these factors were unrelated to gardening, i.e., not having spent more than USD 3.50 the previous day (odds ratio (OR = 2.8, IC95 p. 100 = 1.01-7.81) and poor food hygiene (cooking outside (OR = 4.69, IC95 p. 100 = 1.06-20.83). The other two factors were regular consumption of raw vegetables (OR = 25.5, IC95 p. 100 = 2.0-32.0) and use of untreated well water (OR = 3.85, IC95 p. 100 = 1.08-14.29). Unprotected well water was the cause of 59.2 p. 100 of diarrheal episodes reported by gardeners at Tel Zatar. The results of this study confirm that vegetable production in urban gardens such as Tel Zatar is associated with health risks. Public health measures should address not only the garden sites but also domestic hygiene.

[Clinical aspects and epidemiology of cryptosporidiosis in immunocompetent children]. / Klinik und Epidemiologie der Kryptosporidiose bei immunkompetenten Kindern.

A prospective case-control study was performed in urban and periurban areas of Basel to investigate the epidemiology of Cryptosporidium sp., an intestinal coccidian parasite. 455 children with diarrhoea, who attended paediatric and general practices, participated in the study. Oocysts of the parasite were detected in stool specimens of 21 (4.6%) patients using auramine-fluorescence and modified Ziehl-Neelson staining. Another ten infected people were found during separate investigations of outbreaks in a Kindergarten and in two families. Serial stool stains were performed to determine the period of oocyst shedding. The median duration of diarrhoea was six days and ranged from 1 to 25 days. In contrast, shedding of oocysts of Cryptosporidium sp. lasted for 12.5 days and was significantly longer than the period of diarrhoea (p = 0.02). Compared with control patients suffering from diarrhoea of other origin, respiratory symptoms were significantly (p = 0.02) more frequent in children with cryptosporidiosis (42% vs 13%). In comparison with healthy controls, prior contact with a person suffering from diarrhoea and travel to a Mediterranean country were the most important risk factors for cryptosporidiosis. An illustrative case is described in detail. It is concluded that cryptosporidial infection of the respiratory tract may also occur in immunocompetent children. The possibility of a long period of oocyst shedding is important for the planning of hygiene measures both in individuals and public health.

Risk of Vibrio transmission linked to the consumption of crustaceans in coastal towns of Côte d'Ivoire.

The purpose of this study was to assess the risk of Vibrio spp. transmission from crustaceans to humans in two coastal towns of Côte d'Ivoire. Bacteriologic analysis was performed on 322 crustacean samples obtained from six markets in Abidjan and one in Dabou. Suspected Vibrio colonies were identified by morphological, cultural, biochemical, and molecular tests and matrix-assisted laser desorption ionization-time-of-flight mass spectrometry. PCR assays were used to further characterize Vibrio strains. A survey on consumption of crustaceans was conducted among 120 randomly selected households in Abidjan. Overall, Vibrio spp. were isolated from 7.8% of the crustacean samples studied, at levels as high as 6.3 log CFU/g. Of the Vibrio strains identified, 40% were V. alginolyticus, 36% were V. parahaemolyticus, and 24% were nontoxigenic V. cholerae; the latter two species can cause mild to severe forms of seafood-associated gastroenteritis. Among interviewed households, 11.7% reported daily consumption of crustaceans, confirming the high probability of exposure of human population to Vibrio spp., and 7.5% reported symptoms of food poisoning after consumption of crustaceans. The absence of genes encoding major virulence factors in the studied strains, i.e., cholera toxin (ctxA and ctxB) in V. cholerae and thermostable direct hemolysin (tdh) and thermostable direct hemolysin-related hemolysin (trh) in V. parahaemolyticus, does not exclude the possibility of exposure to pathogenic strains. However, human infections are not common because most households (96.7%) boil crustaceans, usually for at least 45 min (85.9% of households) before consumption.

Trichinellosis during pregnancy: a case control study in the Lao Peoples' Democratic Republic.

Transmission of Trichinella to humans is still a global public health concern. Although theoretically possible, vertical transmission of Trichinella has rarely been investigated. In June 2005 an outbreak of trichinellosis was reported in Udomxay province, the Northern Lao Peoples' Democratic Republic (PDR). In February and March 2006 we performed a study of all pregnant and lactating mothers and infants in the location of this outbreak to assess the possible occurrence of vertical transmission. The study used questionnaires, mother and child clinical examinations, and serology (Western blot) and, based on the results, women were classified as suspect, possible, or confirmed cases. A control group included unexposed pregnant women and their children. Among 200 women from 21 villages, 8 were confirmed positive for trichinellosis by serology; 4 of these were symptomatic. Among their children, one died in utero at 26 weeks gestation due to maternal hepatitis of unknown etiology and a second child had Trichinella-specific IgG antibodies but was clinically normal. A third child, with negative serology had an inter-ventricular cardiac communication. The remaining children did not differ from controls. Our results cannot prove that transmission of trichinellosis occurs from mother to child.