An extensive malacological survey was carried out between 2005-2009 in
order to clarify the exact number of lymnaeid species which may be
intermediate hosts of Fasciola hepatica in Venezuela. Four ...species
were discovered during this survey, including two local species:
Lymnaea cubensis and Lymnaea cousini and two exotic species:
Lymnaea truncatula and Lymnaea columella . The most common local
species was L. cubensis which was found at 16 out of the 298 sampling
sites. This species has a large distribution area throughout the
Northern part of Venezuela and was encountered from sea level to an
altitude of 1,802 m in state of Trujillo. The second local species L.
cousini was collected at only two sites of the Andean Region at
altitudes of 3,550 m and 4,040 m, respectively. The European L.
truncatula was found at 24 sites all located in the states of
Mérida and Táchira at an altitude varying between 1,540-4,000
m. The respective distribution areas of L. cubensis and L. truncatula
do not appear to overlap, but more detailed malacological surveys are
needed. The fourth lymnaeid species, L. columella was collected in a
canal from Mérida at an altitude of 1,929 m and in an irrigation
canal from the state of Guárico, at an altitude of 63 m. The role
of these four lymnaeid species in the transmission of fascioliasis in
Venezuela is discussed.
Display omitted
•28 isolates of Trypanosoma cruzi from five outbreaks of orally Chagas disease occurred in Venezuela were evaluated.•Parasite populations with the haplotype TcId and multiclonal ...populations were identified.•Analysis of the SL-IR motif showed two clones with a different sequence that is possibly evidence of a hybrid haplotype.•Different haplotypes among pre and post-treatment isolates from a single patient have been found.
In Venezuela six episodes of oral transmission of Chagas disease (OChD) have been described, being the one reported in 2007 with a total of 103 people infected the largest worldwide. This work shows the use of three molecular markers (mini-exon gene and domains 24Sα and 18S of the ribosomal RNA) to characterize the infecting Trypanosoma cruzi strain of patients, reservoirs and vectors involved in five of the six OChD outbreaks. For this, 28 T. cruzi isolates were characterized by PCR, and the products of these reactions cloned and sequenced to reveal the existence of different TcI SL-IR genotypes. We also describe a new PCR assay able to discriminate between TcIb and TcId parasite populations. In summary, we have identified mostly parasites with the TcId haplotype and multiclonal populations with predominance of haplotype TcId (65.2%). Additionally, populations of haplotypes TcIb, TcIa and mixtures (TcId+TcIb, TcId+TcIa, TcIb+TcIa) are recurrent in samples obtained from children. The analysis of the SL-IR motif showed two clones depicting a different motif that could be an evidence for a possible hybrid haplotype between TcIa and TcIb (haplotype TcIa/Ib). Interestingly, in a single patient haplotype differences between T.cruzi isolates obtained pre and post-treatment were found. In conclusion, our findings show that in order to understand the pathogenic mechanisms involved in the orally adquired Chagas disease there is a need to join efforts to study T. cruzi haplotypes, their tissue tropisms and their susceptibility to chemoteaphy.
Trypanosoma cruzi I, a discrete typing unit (DTU) found in human infections in Venezuela and other countries of the northern region of South America and in Central America, has been recently ...classified into five intra-DTU genotypes (Ia, Ib, Ic, Id, Ie) based on sequence polymorphisms found in the spliced leader intergenic region. In this paper we report the genotype identification of T. cruzi human isolates from one outbreak of acute orally acquired Chagas disease that occurred in a non-endemic region of Venezuela and from T. cruzi triatomine and rat isolates captured at a guava juice preparation site which was identified as the presumptive source of infection. The genotyping of all these isolates as TcId supports the view of a common source of infection in this oral Chagas disease outbreak through the ingestion of guava juice. Implications for clinical manifestations and dynamics of transmission cycles are discussed.
Low and very-low intensities of infection hinder the diagnosis of schistosomiasis. Therefore, new parameters should be established in order to more accurately identify active cases and true infection ...prevalence, for the adequate implementation of a control program. After the survey and analysis of the epidemiological characteristics of five Venezuelan communities, we propose three criteria for the definition of a "schistosomiasis case", based on different diagnostic methods: stool examination, ELISA-soluble egg antigen with sodium metaperiodate (SMP-ELISA), alkaline phosphatase immunoassay (APIA) and the circumoval precipitin test (COPT). Briefly, criterion I: persons with Schistosoma mansoni eggs in stools; criterion II: persons without eggs in stools, with positive COPT, without previous antischistosome chemotherapy in the last year; and criterion III: persons without eggs in stools, with negative COPT, with two positive immunoenzymatic tests (SMP-ELISA and APIA), and with no previous chemotherapy. The incorporation of serological tests to epidemiologic surveillance in areas of low-transmission tries to compensate the underestimation of prevalence based only on parasitological diagnosis.
Parasitic diseases remain as a major public health problem worldwide, not only based on their historically high morbidity and mortality rates, but also because risk factors associated with their ...transmission are increasing. Laboratory diagnosis and particularly immunodiagnosis is a basic tool for the demonstration, clinical management and control of these infections. Classically, the serological tests for the detection of antibodies or antigens are based on the use of crude and purified antigens. Synthetic peptides have opened a new field and perspectives, as the source of pure epitopes and molecules for diagnosis of malaria, Chagas' disease, leishmaniasis, schistosomiasis, hidatidosis, cysticercosis and fasciolosis based on the detection of antibodies and circulating antigens. Herein, are critically reviewed the relevant advances and applications of the synthetic peptides on immunodiagnosis of parasitic diseases. A variety of sequences, constructs (monomers, polymers, MAPs), immunological methods and samples have been used, demonstrating their diagnostic potential. However, in most parasitic infections it is necessary to use more than a single peptide in order to avoid the genetic restriction against certain epitopes, as well as to test them in well characteized groups of patients, in order to confirm their sensitivity and specificity. The concept of multidiagnosis with synthetic peptides, using a novel multi-dot blot assay is introduced. Finally, the chemical imitation of antigens, offers a tremendous posibilities in the diagnosis of parasitic infections in developing countries since this strategy is cheaper, simpler, reproducible, useful for large scale testing and in most cases, specific and sensitive.
We have previously confirmed the presence of common antigens between
Schistosoma mansoni and its vector, Biomphalaria glabrata .
Cross-reactive antigens may be important as possible candidates for
...vaccine and diagnosis of schistosomiasis. Sera from outbred mice
immunized with a soluble Biomphalaria glabrata antigen ( SBg A) of
non-infected B. glabrata snails recognized molecules of SBg A itself
and S. mansoni AWA by Western blot. Recognition of several molecules of
the SBg A were inhibited by pre-incubation with AWA (16, 30, 36, 60 and
155 kDa). The only specific molecule of AWA, inhibited by SBg A, was a
120 kDa protein. In order to determine which epitopes of SBg A were
glycoproteins, the antigen was treated with sodium metaperiodate and
compared with non-treated antigen. Molecules of 140, 60 and 24 kDa in
the SBg A appear to be glycoproteins. Possible protective effects of
the SBg A were evaluated immunizing outbred mice in two different
experiments using Freund's Adjuvant. In the first one (12 mice/group),
we obtained a significant level of protection (46%) in the total worm
load, with a high variability in worm recovery. In the second
experiment (22 mice/group), no significant protection was observed,
neither in worm load nor in egg production per female. Our results
suggest that SBg A constitutes a rich source of candidate antigens for
diagnosis and prophylactic studies.
After 57 years of successful control of schistosomiasis in Venezuela,
the prevalence and intensity of infection have declined. Approximately
80% of the individuals eliminate less than 100 eggs/g of ...stools,
therefore morbidity is mild and the majority are asymptomatic. The
sensitivity of Kato-Katz decreases to approximately 60%. Available
serological methods for the detection of circulating antigens only
reach a 70% of sensitivity. Tests based on the detection of antibodies
by immunoenzymatic assays have been improved. The circumoval
precipitine test has shown a high sensitivity (97%), specificity
(100%), and correlation with oviposition, being considered the best
confirmatory diagnostic test. Additionally to the classical
immunoenzymatic assays, the development of the alkaline phosphatase
immunoassay, allowed to reach a 100% specificity with an 89%
sensitivity. Recently, we have developed a modified ELISA in which the
soluble egg antigen is treated with sodium metaperiodate (SMP-ELISA) in
order to eliminate the glycosilated epitopes responsible for the false
positive reactions. The specificity and sensitivity reaches 97% and
99%, respectively. Synthetic peptides from the excretory-secretory
enzymes, cathepsin B (Sm31) legumain (Sm32) and cathepsin D (Sm45),
have been synthesized. The combination of two peptides derived from the
Sm31 have been evaluated, reaching a sensitivity of 96% when analyzed
independently and with a 100% specificity. Antibodies raised in rabbits
against peptides derived from the Sm31 and Sm32 are currently evaluated
in two different antigen-capture-based assays. The development of a
simple, cheap and reliable test that correlates with parasite activity
is a major goal.
It is not unusual to find common molecules among different species of the genus
Schistosoma. When those molecules are antigenic, they may be used in immunodiagnosis and vaccines, but they could also ...be applied to taxonomic and evolutionary studies. To study cross-reactivity and antigenic community among different species of schistosomes, plasmas from laboratory animals infected with
Schistosoma bovis,
S. guineensis,
S. rodhaini,
S. haematobium, and four strains of
S. mansoni were evaluated with a crude extract of adult worms of
S. mansoni by Western blot. Using the multiple antigen blot assay, plasmas from these infected animals were exposed to a selected group of synthetic peptides from Sm28GST, Sm28TPI, Sm elastase, Sm97, Sm32, Sm31, and Sm Cathepsin L. The results presented herein demonstrate differential cross-reactivity and antigenic community among the Mansoni and Haematobium groups of schistosomes, which is of relevance as an additional new tool for phylogenetic studies of schistosomes as well as for diagnosis and vaccine purposes.
Hepatitis B virus (HBV) infection among Venezuelan populations of African origin was analyzed. These populations exhibited lower HBV prevalence than the one found in the African continent. Sequence ...analysis of 6 isolates showed that 3 belonged to genotype F, while the 3 others were HBV genotype A. HBV genotype A was more common in the Afro-Venezuelan groups than in the general Venezuelan population. This might reflect the introduction of genotype A during the slavery period. The absence of the African genotype E among these isolates supports the hypothesis of a recent origin for this HBV genotype. HBV genotype F has already been introduced to these relatively isolated communities.
PDF
