Further studies on the molecular systematics of Biomphalaria snails from Brazil

The polymerase chain reaction and restriction fragment length polymorphism (RFLP) of the internal transcribed spacer (ITS) region of the rRNA gene, using the enzyme DdeI were used for the molecular identification of ten species and one subspecies of Brazilian Biomphalaria. Emphasis is given to the analysis of B. oligoza, B. schrammi and B. amazonica. The RFLP profiles obtained using this enzyme were highly distinctive for the majority of the species and exhibited low levels of intraspecific polymorphism among specimens from different regions of Brazil. However, B. peregrina and B. oligoza presented very similar profiles that complicated their identification at the molecular level and suggested a very close genetic similarity between the two species. Others enzymes including HaeIII, HpaII, AluI and MnlI were tested for their ability to differentiate these species. For B. amazonica three variant profiles produced with DdeI were observed. The study demonstrated that the ITS contains useful genetic markers for the identification of these snails

Effect of interferon-alpha on experimental septal fibrosis of the liver - study with a new model

Interferon-alpha is used in antiviral therapy in humans, mainly for viral hepatitis B and C. An anti-fibrotic effect of interferon has been postulated even in the absence of anti-viral response, which suggests that interferon directly inhibits fibrogenesis. Rats infected with the helminth Capillaria hepatica regularly develop diffuse septal fibrosis of the liver, which terminates in cirrhosis 40 days after inoculation. The aim of this study was to test the anti-fibrotic effect of interferon in this experimental model. Evaluation of fibrosis was made by three separate methods: semi-quantitative histology, computerized morphometry and hydroxyproline measurements. Treatment with interferon-alpha proved to inhibit the development of fibrosis in this model, especially when doses of 500,000 and 800,000 IU were used for 60 days. Besides confirming the anti-fibrotic potential of interferon-alpha on a non-viral new experimental model of hepatic fibrosis, a clear-cut dose-dependent effect was observed.

First Report of Lappetascaris lutjani Rasheed, 1965 (Nematoda, Ascaridoidea, Anisakidae) Parasitizing Trachipterus arawatae (Pisces, Lampridiformes) on the Atlantic Coast of Brazil

New host and geographical records are reported for the nematode Lappetascaris lutjani Rasheed, 1965, parasitizing the marine fish Trachipterus arawatae Clark, 1881 in Brazilian waters. Morphometric data and illustrations of the parasites are included.

Observations on the Domestic Ecology of Rhodnius ecuadoriensis (Triatominae)

Rhodnius ecuadoriensis infests peridomiciles and colonises houses in rural southern Ecuador. Six out of 84 dwellings (7%) surveyed in a rural village were infested (78 bugs/infested domicile; 279 bugs were collected in a single dwelling). Precipitin tests revealed R. ecuadoriensis fed on birds (65%), rodents (31%), marsupials (8%), and humans (15%) - mixed bloodmeals detected in 37.5% of individual samples. Trypanosoma cruzi from opossums and rodents may thus be introduced into the domestic cycle. Wasp parasitoidism was detected in 6.5% of 995 R. ecuadoriensis eggs (only in peridomestic habitats). Control strategies should integrate insecticide spraying (indoors and peridomestic), better management of poultry, and housing improvements. A possible inefficacy of Malathion is reported.

Longitudinal Study on the Natural Infection of Biomphalaria straminea and B. glabrata by Schistosoma mansoni in an Endemic Area of Schistosomiasis in Pernambuco, Brazil

The abundance of snail hosts and the rates of infection with Schistosoma mansoni were monitored monthly for four years in two representative localities subjected to repeated chemotherapy of infected persons. Snail abundance varied from 1.0 to 4.4 collected per person/minute/station for Biomphalaria straminea and from 0.1 to 7.0 for B. glabrata. Infection rates of snails in nature varied from 0% to 15% for the former and from 0% to 70% for the latter species. Human infection increased from 35.5% to 61.9% in the locality occupied by B. straminea, and decreased from 40.3% to 20.8% in that occupied by B. glabrata. No relationship could be detected between human infection and the snail variables. Despite seasonal variations, natural infection persisted throughout the monitoring period in both snail species. It reached remarkably high levels in B. straminea when compared to those obtained by other authors probably because of differences in methodology. It is recommended that longitudinal studies should be carried out focally and periodically to avoid underestimating the prevalence of schistosome infection in snails.

The effect of isolation on reproduction and growth of Pseudosuccinea columella (Pulmonata: Lymnaeidae): a snail-conditioned water experiment

A snail-conditioned water experiment was conducted in Pseudosuccinea columella to test the possible role of a chemical interaction between snails on the diminished growth and fecundity rates found for snails raised in pairs compared to those raised in complete isolation. The results permit to discard the hypothesis of an inhibition of growth and reproduction between snails due to factors released into the water.

The influence of hydrocortisone on cellular defence mechanisms of Biomphalaria glabrata

Since the internal defense system of mollusks consists of cellular and humoral mechanisms, we examined the role of hydrocortisone in mollusks defense cells and the influence of this steroid on the development of Schistosoma mansoni in its intermediary host. Hydrocortisone had an immunosuppressive action in Biomphalaria glabrata, as reflected in the reduced number of defense cells and the altered cell physiology. Histopathological analysis showed that hydrocortisone facilitated the intramolluscan development of S. mansoni, by reducing the extent of the inflammatory response, seen as a greater number of viable sporocysts with no surrounding hemocytes.

Schistosomiasis mansoni in Bananal (State of São Paulo, Brazil): IV. Study on the public awareness of its risks in the Palha District

A rather high prevalence of mansoni schistosomiasis has been observed in some localities of Bananal, State of São Paulo, during the past decade. The highest prevalence of schistosomiasis was found in the Palha District; it was thus considered adequate for an evaluation of public awareness of the risks involved in acquiring schistosomiasis, a likely outcome of certain behavior patterns. We interviewed 542 district-dwellers. The 5-to-39 age-group constituted 65.5% of the whole sample. Concerning the infection, 69.2% had hearsay information; 46.1% know the infection; 69.6% know how it is acquired; 31.5% know about the symptoms and 57.1% know what can be done to avoid infection; 17.7% declared to have acquired the infection at least once in their lifetime; 62.3% reported total or partial immersion in collections of water of Bananal, once or twice a week, 53.9% of these for bathing or fishing. Although most (91.7%) households have treated running water, are connected to the sewage network or have septic tanks, 9% of the people interviewed use to defecate on the field. It became clear that the educational messages aimed at this population had not been adequate, having failed to fulfil any expectations. The local people received only piecemeal and subjective information about their problem. The control of schistosomiasis requires an integrated practice, which includes the analysis of macro-determinant factors, such as basic sanitation, habitation, education and health care. In short, we require a multidisciplinary vision of the mechanisms of transmission of the infection, which depends upon adequate planning and well trained personnel, intent on their educational work, to attain satisfactory results.

Schistosomiasis mansoni: follow-up of control program based on parasitologic and serologic methods in a Brazilian community of low endemicity

A field survey on schistosomiais was carried out in 1998, in the municipality of Pedro de Toledo, a low endemic area in the state of São Paulo, Brazil. According to the parasitologic Kato-Katz method, the prevalence rate was 1.6%, with an infection intensity of 40.9 eggs per gram of stool. By the immunofluorescence test (IFT) for detection of IgG and IgM antibodies in the serum, IgG-IFT and IgM-IFT, respectively, prevalence indices of 33.2% and 33.5% were observed. To assess the impact of the schistosomiasis control program in the area, parasitologic and serologic data obtained in 1998, analyzed according to the age, sex, and residence zone, were compared to previous data obtained in a epidemiologic study carried out in 1980, when prevalence indices were of 22.8% and 55.5%, respectively by Kato-Katz and IgG-IFT. A significant fall of the prevalence was observed, indicating that the control measures were effective. Nonetheless, residual transmission was observed, demonstrating the need for a joint effort to include new approaches for better understanding the real situation and improving the control of the disease in low endemic areas.

Effect of angiotensin II and losartan on the phagocytic activity of peritoneal macrophages from Balb/C mice

Angiotensin II (AII), a product of rennin-angiotensin system, exerts an important role on the function of immune system cells. In this study, the effect of AII on the phagocytic activity of mouse peritoneal macrophages was assessed. Mice peritoneal macrophages were cultured for 48 h and the influence of different concentrations of AII (10-14 to 10-7 M) and/or losartan, 10-16 to 10-6 M), an AT1 angiotensin receptor antagonist, on phagocytic activity and superoxide anion production was determined. Dimethylthiazoldiphenyltetrazolium bromide reduction and the nucleic acid content were used to assess the cytotoxicity of losartan. A stimulatory effect on phagocytic activity (P < 0.05) was observed with 10-13 M and 10-12 M AII concentrations. The addition of losartan (up to10-14 M) to the cell cultures blocked (P < 0.001) the phagocytosis indicating the involvement of AT1 receptors. In contrast, superoxide anion production was not affected by AII or losartan. The existence of AT1 and AT2 receptors in peritoneal macrophages was demonstrated by immunofluorescence microscopy. These results support the hypothesis that AII receptors can modulate murine macrophage activity and phagocytosis, and suggest that AII may have a therapeutic role as an immunomodulatory agent in modifying the host resistance to infection.

Effect of blood components, abdominal distension, and ecdysone therapy on the ultrastructural organization of posterior midgut epithelial cells and perimicrovillar membranes in Rhodnius prolixus

The effects of blood components, nerve-cord severance, and ecdysone therapy on the posterior midgut epithelial cells of 5th-instar Rhodnius prolixus nymphs 10 days after feeding were analyzed by transmission electron microscopy. Cutting the nerve-cord of the blood-fed insects partially reduced the development of microvilli and perimicrovillar membranes (PMM), and produced large vacuoles and small electrondense granules; insects fed on Ringer's saline diet exhibited well developed microvilli and low PMM production; swolled rough endoplasmatic reticulum and electrondense granules; Ringer's saline meal with ecdysone led to PMM development, glycogen particles, and several mitochondria in the cytoplasm; epithelial cells of the insects fed on Ringer's saline meal whose nerve-cord was severed showed heterogeneously distributed microvilli with reduced PMM production and a great quantity of mitochondria and glycogen in the cytoplasm; well developed microvilli and PMM were observed in nerve-cord severed insects fed on Ringer's saline meal with ecdysone; Ringer's saline diet containing hemoglobin recovered the release of PMM; and insects fed on human plasma showed slightly reduced PMM production, although the addition of ecdysone in the plasma led to a normal midgut ultrastructural organization. We suggest that the full development of microvilli and PMM in the epithelial cells depends on the abdominal distension in addition to ingestion of hemoglobin, and the release of ecdysone.

Triatoma rubrovaria (Blanchard, 1843) (Hemiptera - Reduviidae - Triatominae) IV: bionomic aspects on the vector capacity of nymphs

Triatoma rubrovaria has become the most frequently captured triatomine species since the control of T. infestans in the state of Rio Grande do Sul (RS), Brazil. The aim of this study was to evaluate aspects of the vectorial competence of T. rubrovaria using nymphs raised in laboratory under environmental conditions of temperature and humidity and fed on mice. The average developmental period of T. rubrovaria was 180.1 days. The percentage of defecation shortly after feeding was still higher than previous studies in which samples of T. rubrovaria subjected to a slight starvation period before the blood meal were used. The obtained results support former indication that T. rubrovaria presents bionomic characteristics propitious to be a good vector of Trypanosoma cruzi to man. Therefore its domiciliary invasion process must be continuously monitored.

The effects of temperature change on the infection rate of Biomphalaria glabrata with Schistosoma mansoni

The aim of this study was to investigate the influence of temperature on the development of Schistosoma mansoni infections in Biomphalaria glabrata. The snails were infected at 15, 20, and 30ºC, and the cercarial release was analyzed after 30 and 60 days post-infection. Our results showed that a decrease in the temperature has a substantial influence on the development of S. mansoni infection in B. glabrata, with significant differences (p < 0.05) between 15 and 30ºC. These data could provide a better understanding of the epidemiological aspects of schistosomiasis.

The effects of drugs, ions, and poly-l-lysine on the excretory system of Schistosoma mansoni

We have been able to label the excretory system of cercariae and all forms of schistosomula, immature and adult worms with the highly fluorescent dye resorufin. We have shown that the accumulation of the resorufin into the excretory tubules and collecting ducts of the male adult worm depends on the presence of extracellular calcium and phosphate ions. In the adult male worms, praziquantel (PZQ) prevents this accumulation in RPMI medium and disperses resorufin from tubules which have been prelabelled. Female worms and all other developmental stages are much less affected either by the presence of calcium and phosphate ions, or the disruption caused by PZQ. The male can inhibit the excretory system in paired female. Fluorescent PZQ localises in the posterior gut (intestine) region of the male adult worm, but not in the excretory system, except for the anionic carboxy fluorescein derivative of PZQ, which may be excreted by this route. All stages of the parasite can recover from damage by PZQ treatment in vitro. The excretory system is highly sensitive to damage to the surface membrane and may be involved in vesicle movement and damage repair processes. In vivo the adult parasite does not recover from PZQ treatment, but what is inhibiting recovery is unknown, but likely to be related to immune effector molecules.

A thirty years follow-up study on Schistosomiasis mansoni in a community of Minas Gerais, Brazil

During thirty years - 1973-2003 - a group of individuals infected by Schistosoma mansoni in Capitão Andrade, Rio Doce Valley, Minas Gerais, Brazil, was evaluated by the same authors, being one of the longest follow-up studies on schistosomiasisis mansoni in an endemic area. The diagnosis of S. mansoni was based on parasitological stool tests. In the clinical classification, three groups were considered: type I - schistosomiasis-infection, type II - hepatointestinal form, and type III- hepatosplenic form. The prevalence of infection were 60.8% in 1973, 36.2% in 1984, 27.3% in 1994, and 19.4% in 2003, while the index of hepatosplenomegaly were respectively 5.8%, 2.8%, 2.3% and 1.3%. The maintenance of high prevalence and severity of clinical forms are probably related to reinfection.