Transactions of the Royal Society of Tropical Medicine and Hygiene

Editorial Board

2010-04-01

Clinical heterogeneity of human neurocysticercosis results from complex interactions among parasite, host and environmental factors

Agnès Fleury, Alfonso Escobar, Gladis Fragoso, Edda Sciutto, Carlos Larralde — 2010-04-01

Abstract: Human neurocysticercosis (NC) is endemic in most countries of Latin America, Asia and Africa and is re-emerging in some industrialized nations. Both within and among endemic countries, NC is very variable in its clinical and radiological features, as well as in the intensity of the immuno-inflammatory reactions of the hosts. This review, focusing on the Mexican experience, describes and interprets the heterogeneity of NC as the result of different combinations among factors associated with the parasite, host and environment. The review may serve to foster similar descriptive efforts in other endemic areas of the world in order to facilitate the identification of the distinct factors that participate in the complex pathogenesis and diverse clinical outcomes of NC. In particular, it is necessary to understand the precise physiopathology of the inflammatory reaction associated with NC, as inflammation is one of the characteristics of those NC cases that are clinically more severe and less responsive to current treatments. Devising new medical interventions through the use of molecular regulators of the innate and adaptive immune responses of the host is a largely unexplored approach that could improve the existing forms of treatment.

Malaria imported into Réunion Island: is there a risk of re-emergence of the disease?

E. D’Ortenzio, D. Sissoko, J.S. Dehecq, P. Renault, L. Filleul — 2010-04-01

Abstract: After a long period of endemicity until the 1950s, the World Health Organization considered autochthonous malaria eliminated from Réunion in 1979. To prevent secondary transmission and re-emergence of autochthonous malaria, permanent epidemiologic and entomological surveillance and vector control measures are conducted.The objective of this study is to report sociodemographic characteristics of imported malaria patients and incidence rates from 2003–2008 using mandatory notification with the aim of identifying risk groups and destinations.During this period, 684 imported malaria cases were reported. Median age of patients was 34.4 years and 22.1% were children ≤ 15 years. Men represented 67.7% of cases and 59.1% of patients reported having taken chemoprophylaxis based on chloroquine alone. Incidence of malaria was considerably different by country destination. For Comoros, incidence was stable and high during the period accounting for 1481 cases per 100000 travels in 2008. The rate was lower for travels to Madagascar, South Africa and Mayotte and decreased over the period to 37, 19 and 3 per 100000 respectively, by 2008.To avoid re-emergence of malaria on the island and to protect themselves, travelers should reduce their risks of acquisition and importation of parasites by using adequate preventive measures. A special preventive program and social mobilisation should be a priority, essentially for the Comorian community in Réunion.

Development of a new assay for the diagnosis of schistosomiasis, using cercarial antigens

M.A. Chand, P.L. Chiodini, M.J. Doenhoff — 2010-04-01

Abstract: We have developed a new ELISA for detection of anti-schistosome antibodies using an extract from Schistosoma mansoni cercariae. We evaluated the new assay on serum samples sent to the Hospital for Tropical Diseases, Department of Clinical Parasitology, London, UK, by comparing it with our routinely used S. mansoni soluble egg antigen (SEA) assay. We also evaluated the new assay for cross-reactivity with a number of helminth and other infections. We demonstrate that the cercarial antigen assay is equivalent to the SEA assay for serodiagnosis of schistosomiasis in a non-endemic setting. The cercarial antigen preparation is more easily produced than SEA, and for this reason this assay may be preferred for routine clinical use and may be amenable to scaling up. Further assessment is needed before it can be recommended for use in an endemic area, as chronic disease and co-infection with other helminths are likely to be under-represented in our sample set.

Testing different antigen capture ELISA formats for detection of Leptospira spp. in human blood serum

2010-04-01

Abstract: Leptospirosis is an infectious disease caused by pathogenic spirochetes of the genus Leptospira. The illness is characterized by an acute bacteremic phase followed by an immune phase, in which specific antibodies are found in blood and leptospires are eliminated in urine. Novel diagnostic strategies for use in the acute phase of leptospirosis are needed since clinical manifestations in this phase mimic other feverish tropical diseases. In the present study, mAbs and polyclonal IgY were used in the standardization of three different antigen capture ELISA formats for direct detection of leptospires in human blood during the acute phase of the disease. Detection limit of leptospires in experimentally contaminated human sera ranged from 105 to 107 cells ml−1 in the different formats. The ELISA format with the best performance was able to detect 105 leptospires ml−1 in human sera using a mAb against LipL32, the major outer membrane protein of pathogenic leptospires, as capture antibody, and a biotinylated polyclonal IgY against a pathogenic serovar of L. interrogans Icterohamorrhagiae as detection antibody. By increasing the degree of IgY biotinylation this detection limit could be improved to make the assay clinically useful.

Traditional kinship system enhanced classic community-directed treatment with ivermectin (CDTI) for onchocerciasis control in Uganda

2010-04-01

Abstract: The challenges of community-directed treatment with ivermectin (CDTI) for onchocerciasis control in Africa have been: maintaining a desired treatment coverage, demand for monetary incentives, high attrition of community distributors and low involvement of women. This study assessed how challenges could be minimised and performance improved using existing traditional kinship structures.In classic CDTI areas, community members decide upon selection criteria for community distributors, centers for health education and training, and methods of distributing ivermectin. In kinship enhanced CDTI, similar procedures were followed at the kinship level. We compared 14 randomly selected kinship enhanced CDTI communities with 25 classic CDTI communities through interviews of 447 and 750 household members and 127 and 64 community distributors respectively.Household respondents from kinship enhanced CDTI reported better performance (P<0.001) than classic CDTI on the following measures of program effectiveness: (a) treatment coverage (b) decision on treatment location and (c) mobilization for CDTI activities. There were more female distributors in kinship enhanced CDTI than in classic CDTI. Attrition was not a problem. Kinship enhanced CDTI had a higher number of community distributors per population working among relatives, and were more likely to be involved in additional health care activities. The results suggest that kinship enhanced CDTI was more effective than classic CDTI.

Wash resistance and residual efficacy of long-lasting polyester netting coated with α-cypermethrin (Interceptor) against malaria-transmitting mosquitoes in Assam, northeast India

V. Dev, K. Raghavendra, S.P. Singh, S. Phookan, K. Khound, A.P. Dash — 2010-04-01

Abstract: Malaria is endemic in Assam, northeast India, with low-to-moderate transmission of the causative parasites, mostly by Anopheles minimus. Plasmodium falciparum is the predominant parasite (>60%), with remaining cases being due to P. vivax. As an alternative intervention for malaria control, long-lasting insecticidal nets [Interceptor coated with α-cypermethrin 10% suspension concentrate (SC), 0.667% w/w, 0.2g/m2] underwent field evaluation for laboratory wash resistance and residual efficacy in field conditions against malaria-transmitting mosquitoes. Based on entomological observations, the Interceptor net intervention was the most effective, corresponding to the lowest mosquito vector density in experimental villages. There was virtual disappearance of A. minimus in Interceptor net villages in contrast to the untreated net intervention and the no-net control. Contact cone bioassay tests revealed 100% mortality in the A. minimus group of mosquito species in the community using the Interceptor net, which was consistent during the follow-up monitoring period (October 2006 to April 2007) in field conditions. Similar levels of mortality were observed in laboratory-washed nets compared with unwashed nets, and wash resistance was consistent even after the 20th serial wash at fortnightly intervals. Community compliance and acceptance of the Interceptor net was high, with decreased nuisance due to biting mosquitoes and other household insect pests being reported.

A comparative retrospective study of RT-PCR-based liquid hybridization assay for early, definitive diagnosis of dengue

2010-04-01

Summary: Dengue is an important flaviviral infection in tropical and subtropical regions. Early diagnosis of dengue infection helps in monitoring the disease, determining when hospital admission is necessary and reducing case fatalities. The objective of this study was to carry out a retrospective comparison of an RT-PCR-based liquid hybridization (RT-PCR-LH) assay with PCR amplification, virus isolation and serological techniques for laboratory diagnosis of dengue infection. Amplified products of non-structural 3 gene were hybridized with a mixture of four dengue type-specific DNA probes in liquid phase. The assay was validated in a comparative retrospective study using acute serum samples collected from 119 fever patients with or without dengue, confirmed by haemagglutination inhibition (HAI) assay, the gold standard assay for diagnosis of dengue infection. The RT-PCR-LH assay was highly specific for dengue and, as an early laboratory diagnostic method, had 100% sensitivity in detecting dengue patients confirmed by HAI assay. A high analytical sensitivity of two fluorescent focus units of dengue virus/reaction was achieved. This RT-PCR-LH assay using a single serum specimen offers distinct advantages of specificity and sensitivity over other diagnostic techniques for early definitive laboratory diagnosis of dengue infection when serological methods are of little value.

Assessment of latrine use and quality and association with risk of trachoma in rural Tanzania

Maggie A. Montgomery, Mayur M. Desai, Menachem Elimelech — 2010-04-01

Abstract: The existing evidence regarding latrines and trachoma is inconclusive. Using more precise sanitation measures we examine the association between use and quality of latrines and risk of trachoma. We conducted a case-control study of 678 households (95 cases, 583 controls) in eight villages in Kongwa District, Tanzania. Case households were defined as having a sentinel child with clinical signs of trachoma. A latrine quality score was calculated based on seven indicators and case and control households were compared with respect to use and quality of latrines. Logistic regression analyses controlled for potential confounders. Latrine use was significantly greater in control households than in case households (90.4 vs. 76.8%, P=0.03). The protective effect of latrine use persisted even after controlling for household characteristics significant at P <0.20 (adjusted OR=0.56 [95% CI: 0.32-0.98]). Contrary to expectation, we did not find an inverse association between increasing latrine quality and decreasing odds of trachoma. Although latrine use in the communities was high, latrines, regardless of quality, were significantly associated with decreased risk of trachoma. These findings underscore the importance of achieving 100% latrine use in communities.

Doxycycline-chloroquine vs. doxycycline-placebo for malaria prophylaxis in nonimmune soldiers: a double-blind randomized field trial in sub-Saharan Africa

2010-04-01

Summary: Failures of malaria chemoprophylaxis have been related to a lack of compliance with doxycycline due to its short elimination half-life. Adding a molecule with a long half-life to doxycycline could be useful to take over from this drug in case of occasional missed doses. A double-blind, placebo-controlled randomized field trial was designed to compare the tolerability of a doxycycline-chloroquine combination vs. doxycycline as malaria prophylaxis among French soldiers deployed in Africa. Data from 936 volunteers were analyzed. In both groups, the proportion of volunteers who reported at least one adverse effect was about 57%. Tolerability was similar in the groups except for a higher proportion of nausea or vomiting in the doxycycline-chloroquine group. The reported compliance rate was 86.6% and was similar in the two groups. Eight Plasmodium falciparum malaria cases were diagnosed in the doxycycline group and seven in the doxycycline-chloroquine group. The efficacy of the two chemoprophylaxis regimens was similar. Our study was the first randomized field trial to assess a doxycycline-chloroquine combination as malaria prophylaxis and showed no significant decrease of overall tolerability of the combination compared with doxycycline alone. Our results showed that a doxycycline-chloroquine combination could be a safe combination for malaria chemoprophylaxis.

Determinants of glycaemic control in type 2 diabetes African patients monitored by physicians from 1991 to 2004 in Cote d’Ivoire

2010-04-01

Summary: The aim of this study was to propose determinants of glycaemic control which are useful to adequately manage the healthcare of type 2 diabetes patients attending an out-patient clinic. A retrospective, descriptive research design was implemented at the Centre AntiDiabétique d’Abidjan in 2399 African patients. Glycaemic control was calculated from the average of at least 12 fasting plasma glucose levels measured during at least three years. Logistic and multiple linear regressions were performed at the limit of the glycaemia average of 6.7mmol/l (120mg/dl). The determinants of poor glycaemic control were: long duration of monitoring (odds ratio (OR)=1.66, then 2.68), annual frequency of visits outside the 2–3 per year interval (OR=3.25) and insulin treatment (OR=4.66) in ‘non-obese men’; the aforementioned frequency of visits (OR=3.69) and insulin treatment (OR=3.72) in ‘non-obese women’; the duration of monitoring reaching the 10–14 year interval (OR=3.48), the aforementioned frequency of visits (OR=2.51), insulin treatment (OR=26.16) and housewife status (OR=1.94) in ‘obese women’. In ‘obese men’, insulin treatment was the sole determinant (r2=0.24). Healthcare parameters (treatment, frequency of visits, and duration of monitoring) seemed to be predominant as effective predictors of glycaemic control in our study context. These findings reveal the urgent need for both more concern and further research in diabetes management to improve the quality of care and tackle this health challenge.

Toxicity of a novel suspension concentrate of niclosamide against Biomphalaria glabrata

Jian-rong Dai, Gerald C. Coles, Wei Wang, You-sheng Liang — 2010-04-01

Summary: As a new suspension concentrate of niclosamide (SCN) was more effective in controlling Oncomelania snails than a wettable powder of the same drug, it was tested against Biomphalaria glabrata. There were no differences in the effect of the suspension concentrate, the wettable powder of niclosamide and ball-milled pure niclosamide against the adult snails, but at after 48h 0.125mg/l SCN killed 100% of eggs compared with 84.3% for WPN and 17.7% for pure niclosamide. Because of the improved handling characteristics of SCN over the other formulations, further field tests on Biompharia and Bulinus species are warranted.

Seroprevalence of IgG antibodies to hepatitis E in urban and rural southern India

Rosario Vivek, George M. Chandy, David W. Brown, Gagandeep Kang — 2010-04-01

Summary: Hepatitis E virus (HEV) is an important cause of sporadic and epidemic hepatitis E infection in northern India. Sera, collected from different age groups in rural (n=1144) and urban (n=1135) areas using a probability proportional to size survey, were tested using an ELISA for IgG antibodies. Antibodies increased with age in both populations, but the urban population had higher exposure in all age groups (Mann-Whitney U test, P<0.001 for all age groups except children <5 years). These results indicate that urban populations with higher density and common water supplies may be at greater risk of hepatitis E.

Scrub typhus mimicking enteric fever; a report of three patients

2010-04-01

Abstract: We report three patients who presented with fever and late onset diarrhoea mimicking enteric fever. All three patients were diagnosed with an Orientia tsutsugamushi infection and responded dramatically to doxycycline treatment. Clinicians practicing in rickettsial disease endemic areas should be made aware of similar clinical presentations in order to prevent morbidity and mortality associated with rickettsioses.