PCR-RFLP analysis of the ITS2 region to identify Schistosoma haematobium and S. bovis from Kenya.
(33/1021)
Schistosoma haematobium, primarily a human parasite, and the closely related Schistosoma bovis from ruminants, are sympatric in many African countries such as Kenya. Because these two species 1) can inhabit the same Bulinus snails, 2) may be found in the same freshwater habitat, and 3) have morphologically similar cercariae, better means are needed to tell them apart. The second internal transcribed spacer (ITS2) region of the ribosomal gene complex (rDNA) of recent Kenyan isolates of both species was sequenced and found to be a 98% match. The S. bovis sequences were nearly identical (99%) to conspecific sequences from Niger; the S. haematobium sequences were nearly identical (99%) to conspecific sequences from Egypt, Mali, and Niger. Restriction fragment length polymorphism (RFLP) analysis of a 480 base pair (bp) PCR product containing the ITS2 region using two restriction enzymes, Taq1 and Sau3A1, yielded species-specific fragment patterns that allowed successful identification of a single S. haematobium cercaria. The protocol outlined here is useful in providing a rapid, one-day identification of S. haematobium (and likely S. bovis) cercariae (the infective larval stage) and/or other life cycle stages in a basic molecular biology laboratory. By helping to determine whether schistosome-infected bulinid snails in a particular body of water are transmitting a human or an animal schistosome, or both, this analysis will aid in disease control and in ongoing epidemiological studies. (+info)
Erhaia (Gastropoda: Rissooidea): phylogenetic relationships and the question of Paragonimus coevolution in Asia.
(34/1021)
The human lung fluke Paragonimus is transmitted by gastropod taxa of two superfamilies: Ceritheoidea and Rissooidea. The question whether or not Paragonimus shows the same specificity of host-parasite coevolved relationship as the human blood fluke Schistosoma was inspired by the finding of two sympatric snail species as hosts for Paragonimus skrjabini in Fujian Province, China: Gammatricula and Erhaia. The former species can clearly be classified as Pomatiopsidae: Triculinae. The latter has previously been classified as Pomatiopsidae: Pomatiopsinae. However, this classification based on anatomical characteristics is uncertain. In order to obtain a robust phylogenetic hypothesis for Erhaia, we have studied three gene fragments from this taxon as well as from twelve related taxa. The data show that the species involved represent four families: Pomatiopsidae, Hydrobiidae, Cochliopidae (here raised to family status), and Amnicolidae. Erhaia fits securely into the Amnicolidae. This indicates that P. skrjabini has not coevolved with snail lineages. However, P. skrjabini has so far only been reported from rissooidean snails, whereas members of the Paragonimus westermani complex have only been found in ceritheoidean snails. The implication is that there is a host specificity on the superfamily level. However, Asian freshwater species of the Ceritheoidea and Rissooidea usually are not sympatric and often prefer different habitats. It is therefore possible that ecological niche partitioning plays the primary role for Paragonimus evolution. (+info)
Prevalence and familial aggregation of schistosomal liver morbidity in Kenya: evaluation by new ultrasound criteria.
(35/1021)
Severe periportal fibrosis is not an inevitable consequence of infection with Schistosoma mansoni. Genetic predisposition may be a deciding factor in the development of disease. To assess the contribution of genetic factors in the severity of hepatic fibrosis, the degree of familial aggregation was determined in a Kenyan population. Schistosomal fibrosis was identified with hepatic ultrasound and newly proposed World Health Organization criteria, which include both qualitative and quantitative observations. These 2 aspects of the criteria correlated well with one another. The peak prevalence of ultrasound proven fibrosis trailed 5-10 years behind peak prevalence of infection and declined sharply after age 50 years. This pattern was consistent with either resolution of severe fibrosis over 10-20 years or early death of those severely affected. Genetic predisposition appears to be a weak factor in the development of severe disease in this population, since no household or familial aggregation could be identified. (+info)
Geographical distribution of Biomphalaria snails in the State of Minas Gerais, Brazil.
(36/1021)
Published and unpublished observations on geographical distribution of Biomphalaria snails in the State of Minas Gerais, Brazil, were compiled. This work is aimed at knowing the present occurrence of Biomphalaria species in this region, and at contributing to the elaboration of the planorbid chart of Minas Gerais. In malacological surveys, performed by several researchers, the presence of seven species of this genus was recorded. Those planorbids were found in 12 mesoregions, in 283 (33.1%) municipalities out of 853 with the following distribution: B. glabrata (185 municipalities), B. straminea (125), B. tenagophila (58), B. peregrina (57), B. schrammi (26), B. intermedia (20) and B. occidentalis (2). B. glabrata and B. tenagophila are found naturally infected by Schistosoma mansoni in Minas Gerais. In 24 municipalities the three snail hosts of S. mansoni in Brazil, B. glabrata, B. tenagophila and B. straminea, are present. (+info)
The situation of sleeping sickness in Angola: a calamity.
(37/1021)
Although nearly one-fifth of the Angolan population is at risk of becoming infected with trypanosomiasis, only 6% currently have access to surveillance and treatment because of the war and its resultant destruction of the country's infrastructure. The paper outlines the history of human African trypanosomiasis (HAT) control activities in Angola and sums up what measures need to be taken to re-establish them. (+info)
Sleeping sickness resurgence in the DRC: the past decade.
(38/1021)
An overview of the evolution of sleeping sickness and control activities in the DRC during the period 1989-1998 is presented. A resurgence was already developing in the mid-1980s and, after a breakdown of active case-finding between 1990 and 1993, annual detection rates attained levels similar to those of the late 1920s. Although a staggering number of 150 591 new cases have been detected during the past decade, the problem is ignored by most of the international community. The major cause for the resurgence appears to be the interruption of active case-finding for a prolonged period of time. Control activities have improved considerably in recent years, but a lot remains to be done and supplementary resources are needed. (+info)
Mechanical transmission of lumpy skin disease virus by Aedes aegypti (Diptera: Culicidae).
(39/1021)
Aedes aegypti female mosquitoes are capable of the mechanical transmission of lumpy skin disease virus (LSDV) from infected to susceptible cattle. Mosquitoes that had fed upon lesions of LSDV-infected cattle were able to transmit virus to susceptible cattle over a period of 2-6 days post-infective feeding. Virus was isolated from the recipient animals in 5 out of 7 cases. The clinical disease recorded in the animals exposed to infected mosquitoes was generally of a mild nature, with only one case being moderate. LSDV has long been suspected to be insect transmitted, but these findings are the first to demonstrate this unequivocally, and they suggest that mosquito species are competent vectors. (+info)
Comments on the process and product of the health impacts assessment component of the national assessment of the potential consequences of climate variability and change for the United States.
(40/1021)
In 1990 Congress formed the U.S. Global Change Research Program and required it to conduct a periodic national assessment of the potential impacts of climate variability and change on all regions and select economic/resource sectors of the United States. Between 1998 and 2000, a team of experts collaborated on a health impacts assessment that formed the basis for the first National Assessment's analysis of the potential impacts of climate on human health. The health impacts assessment was integrated across a number of health disciplines and involved a search for and qualitative expert judgment review of data on the potential links between climate events and population health. Accomplishments included identification of vulnerable populations, adaptation strategies, research needs, and data gaps. Experts, stakeholders, and the public were involved. The assessment is reported in five articles in this issue; a summary was published in the April 2000 issue of Environmental Health Perspectives. The assessment report will enhance understanding of ways human health might be affected by various climate-associated stresses and of the need for further empirical and predictive research. Improved understanding and communication of the significance and inevitability of uncertainties in such an assessment are critical to further research and policy development. (+info)